2025-01-22 (Wednesday) 3:00 PM CST [Webinar]

Short-bio:
Prof. Akarsu, a Turkish cosmologist, currently holds a full professorship at Istanbul Technical University (ITU). He earned his PhD in astrophysics from Ege University in 2010, specializing in cosmology. During his doctoral studies, he conducted research as a visiting PhD student/researcher at the University of Cambridge. In 2010, supported by the Turkish Academy of Sciences, he began his postdoctoral work at Koç University, focusing on theoretical cosmology, before being appointed as an associate professor at ITU in 2015. Prof. Akarsu's primary research interests include theoretical and observational cosmology, as well as modified gravity theories. In recent years, he has focused on understanding and resolving cosmological tensions. He is the co-proposer of the graduated dark energy (gDE) model, which led to the late time AdS-to-dS transition conjecture and the development of the $\Lambda_{\rm s}$CDM paradigm, regarded as one of the most promising approaches for addressing multiple cosmological tensions. He has been a regular guest scientist at the ICTP in Italy since 2010 and has received two of Turkey's most prestigious awards for young scientists, presented by the Science Academy and the Turkish Academy of Sciences.   

Abstract:
Sign-switching cosmological constant cold dark matter ($\Lambda_{\rm s}$CDM) cosmology has emerged as a compelling new paradigm, demonstrating unprecedented success in aligning with observational data from various datasets and effectively addressing major cosmological tensions, such as the $H_0$ and $S_8$ tensions. This model is characterized by a minimal but non-trivial deviation from the standard $\Lambda$CDM framework, proposing a rapid Anti-de Sitter (AdS) to de Sitter (dS) transition in the late universe ($z_\dagger \sim 1.7$), as conjectured through findings in graduated dark energy (gDE) model. In this talk, we will first provide a concise introduction to $\Lambda_{\rm s}$CDM cosmology. We will then discuss the latest theoretical and observational advances that position $\Lambda_{\rm s}$CDM model as a promising candidate or guide for a new concordance cosmological model of the Universe.

Voov Meeting： 973-5661-5791
https://meeting.tencent.com/dm/jZxkr6XiXIkO
Koushare live broadcast 蔻享直播 :
https://www.koushare.com/live/details/34727

2024-11-20 (Wednesday) 3:00 PM CST [Webinar]

Short-bio:
Dr. Sebastian Zell completed his graduate studies at the Max Planck Institute for Physics and Ludwig Maximilian University of Munich, where he earned his PhD in 2019 under the supervision of Gia Dvali. Subsequently, he went on to work at École Polytechnique Fédérale de Lausanne and at UCLouvain, before taking up his current postdoc position at Ludwig Maximilian University of Munich. His research is based at the interface of particle physics and cosmology, with topics ranging from gravity, inflation, black holes and dark matter to axions, quantum information and the mass scales of Nature.   

Abstract:
First reviewing black hole evaporation, I will discuss that the semi-classical calculation of particle production is expected to break down at the latest once half of the mass is lost. Quantum analogue systems, which imitate important properties of a black hole such as its entropy, provide strong indications for a drastic slowdown of evaporation. Therefore, small primordial black holes (PBHs) can both become viable dark matter candidates and provide a unique window on quantum gravity. Finally, I will turn to the inflationary production of small PBHs. A sufficiently small mass alleviates any tension with CMB observations and scalar-induced gravitational waves (GW) can yield an observable signal. I will highlight the need to develop new experiments for high-frequency GW detection in the kHz to MHz range.

Voov Meeting： 973-5661-5791
https://meeting.tencent.com/dm/jZxkr6XiXIkO
Koushare live broadcast 蔻享直播 :
https://www.koushare.com/live/details/34727

2022-05-04 [Webinar]

Title: Emergent inflation from a Nambu–Jona-Lasinio mechanism in gravity with non-dynamical torsion
Speaker: Prof. Antonino Marciano
Institutions: Fudan University 复旦大学

Short-bio:
Antonino Marciano’ is currently Tenured Associate Professor at Fudan University, Full Professor for the Italian Ministry of University and Research, and member of the Italian Institute of Nuclear Physics (INFN), assigned to the theory division of the Frascati laboratories.
As a theoretical physicist, Antonino focuses his scientific research on a variety of topics, ranging mainly from quantum field theories and theories of gravity, to their neighboring research areas as well as analogous applications to Solid State Physics, Artificial Intelligence and Quantum Computation.
Antonino has published so far about 100 articles in international scientific journals with the highest impact factors. He serves as referee for Nature, the American Physical Society, and several Chinese and European journals to assess publications of scientific papers, and as a reviewer for the Italian Minister of the University and Research, for the Dutch Royal Academy of Science, and for the National Science Centre of Poland, to evaluate tenure-track applications and assess scientific grants up to one million euros.

Abstract:
We discuss how inflation can emerge from a four-fermion interaction induced by torsion. Inflation can arise from coupling torsion to Standard Model fermions, without any need of introducing new scalar particles beyond the Standard Model. Within this picture, the inflaton field can be a composite field of the SM-particles and arises from a Nambu-Jona-Lasinio mechanism in curved space-time, non-minimally coupled with the Ricci scalar. The model we specify predicts small value of the r-parameter, namely r ~ 10−4 ÷ 10−2, which nonetheless would be detectable by the next generation of experiments, including BICEP 3 and the AliCPT projects.

2022-05-11 [Colloquium]

Title: Primordial Black Holes from Inflation
Speaker: Prof. Misao Sasaki （佐佐木节 教授）
Institutions: IPMU 数物连携宇宙物理学研究所

Short-bio:
Currently Prof. Misao Sasaki is working as Deputy Director and Project Professor in KAVLI IPMU. His main research interest is in general relativity and cosmology. He is particularly interested in the theory of the inflationary universe. What he is interested in now is looking for new observational signatures that can distinguish differences between different models, to identify the physics behind inflation, and to possibly find traces from physics beyond inflation. In this respect, in addition to electromagnetic waves as an observational tool, gravitational waves will certainly play a central role in cosmology, particularly in exploring early universe physics in coming years. He is currently working on gravitational wave cosmology with this expectation . according to IHeP, .He has around 34 articles as a single author and around 400 as a group !!

Abstract:
The existence of primordial black holes (PBHs) was suggested more than half a century ago. However, studies on the PBH formation have remained at a qualitative level until recently. The situation has changed in the last few years. Thanks to the rapid progress in gravitational wave (GW) astrophysics/cosmology, we have begun to realize that we may actually detect signatures of PBHs by GW observations, in addition to classic gravitational lensing observations. Thus it has become highly important to study possible early universe models for the PBH formation and their observational signatures. In this talk, I discuss some of the recently proposed models of inflation that may lead to a copious production of PBHs.

2022-05-18 [Colloquium]

Short-bio:
Prof. Mark Devlin did his PhD from University of California at Berkeley (1993). Later on Postdoctoral Research from Princeton University and University of California at Berkeley. Currently Prod. Mark Devlin is at University of Pennsylvania as a Reese W. Flower Professor of Astronomy and Astrophysics. His research focuses on experimental cosmology at millimeter and submillimeter wavelengths. He design and build sophisticated instrumentation and telescopes which he use to observe from high-altitude balloons and the high-plateaus of Chile. Current work on four major projects include the Atacama Cosmology Telescope (ACT), the Simons Observatory (SO), The Balloon-borne Large Aperture Telescope (BLAST), and the MUSTANG-2 Instrument on the Green Bank Telescope.

Abstract:
Millimeter-wave surveys of the sky have the potential for yielding a wealth of information about our universe from the first instants of its existence to our own solar system.  I will describe how modern measurements of the cosmic microwave background (CMB) are being used to measure how our universe has evolved over cosmic time leading to a better understand the fundamental parameters governing its nature.  I will present recent results from the Atacama Cosmology Telescope (ACT) and future plans for the Simons Observatory program.

Zoom Meeting： 868 5838 7813 Password： 390176
https://dooyle.zoom.us/j/86858387813?pwd=bWV6cjVqQ1Jra1pPMXZhbjhpaEFLQT09
Koushare live broadcast 蔻享直播 :
https://www.koushare.com/topic-hd/i/Euade

2022-05-21 [Open Lecture]

Abstract:
袁业飞教授：银心黑洞吸积及成像 薛涌泉教授：黑洞照片又双叒叕来啦——直击银心黑洞 蔡一夫教授：银河系的心跳——理论解读

2022-05-25 [Colloquium]

Short-bio:
Prof. Chunshan Lin obtained his PhD degree in 2011, from the University of Science and Technology of China. He successively held postdoc positions in Tokyo University and Kyoto University between 2011 - 2017. In 2017 he joined the university of Warsaw as an assistant professor. He moved to Jagiellonian university, which is his current affiliation, in 2020. His research interests lie primarily in the gravitational waves, early universe, modified gravity, and dark energy.

Abstract:
This is a colloquium talk for students and non-experts (the experts on the topic may find it boring). In this talk I will review several attempts beyond Einstein's general relativity, including the massive gravity whose history can be traced all the way back to 1939, the Horndeski theory which was discovered in 1974 and then rediscovered in 2011, and 4-dimensional Einstein-Gauss-Bonnet theory which was proposed recently yet has stimulated an extensive discussion and controversy among colleagues in the field. The focuses will be on the theoretical consistency of these theories, as well as the experimental testability (or falsifiability).

Zoom Meeting： 872 5593 6961 Password： 879097
https://dooyle.zoom.us/j/87255936961?pwd=TWYrT1B2YlhiNmtWTXBGN3pucno1QT09
Koushare live broadcast 蔻享直播 :
https://www.koushare.com/lives/room/366119

2022-06-01(Wednesday) 9:00 PM CST [Webinar]

Short-bio:
Researcher since 1974 in the field of cosmology, general relativity and quantum field theory
1980:Master at University of Utrecht, supervisor Prof. G, ‘t Hooft
1986: PhD at University of Amsterdam. Promotors Prof. K. Gaemers and Prof E. v/d Heuvel
Copromotor Prof G. ‘t Hooft
www.asfyon.com

Abstract:
A throughout investigation is made of the exact black hole solution in five-dimensional warped conformal dilaton gravity, found in an earlier investigation. The singularities of the dynamical black hole spacetime are determined by the zeros of a meromorphic quintic polynomial, which has no essential singularities.
The solutions of the polynomial are analyzed in the complex plane in relation to the icosahedron group and by the Hopf-fibrations of the Klein surface.
The model fits the antipodal boundary condition, i.e., antipodal points in the projected space are identified using the embedding of a Klein surface in ${C}^2$, using the ${Z}_2$ symmetry on the two sides of the brane.
If one writes $^{(5)}g_{\mu\nu}=\omega^{4/3}{^{(5)}}{\tilde g_{\mu\nu}}, {^{(5)}}{\tilde g_{\mu\nu}}={^{(4)}}{\tilde g_{\mu\nu}}+n_\mu n_\nu$, $ ^{(4)}\tilde g_{\mu\nu}=\bar\omega^2 {^{(4)}}\bar g_{\mu\nu}$, with $n_\mu$ the normal to the brane and $\omega$ the dilaton field, then ${^{(4)}}\bar g_{\mu\nu}$ is conformally flat.
It is the contribution from the bulk which determines the real pole on the effective four-dimensional spacetime.
There is no objection applying 't Hooft's back reaction method in constructing the unitary S-matrix for the Hawking radiation.
Again, there is no "inside" of the black hole.

Zoom Meeting： 840 9109 6731 Password： Ustc1234
https://dooyle.zoom.us/j/84091096731?pwd=d1JtRkVJRlBGV09xZ2g5SDRFZFVRQT09
Koushare live broadcast 蔻享直播 :
https://www.koushare.com/lives/room/831059

2022-06-08 (Wednesday) 7:00 PM CST [Webinar]

Short-bio:
Dr. Dong-Gang Wang was a master student in USTC from 2013 to 2016. After that, he moved to Leiden University in the Netherlands for PhD as a de Sitter Fellow from 2016 to 2020. Now he is a postdoctoral researcher as a Rubicon Fellow at the Department of Applied Mathematics and Theoretical Physics in the University of Cambridge, UK. His research mainly focuses on the primordial cosmology. In particular he is interested in dissecting non-Gaussian statistics of primordial fluctuations by using the effective field theory and bootstrap approaches.

Abstract:
Correlation functions of primordial fluctuations provide us an exciting avenue into the physics with extremely high energy in the very early Universe. Recently the bootstrap approach has offered new perspectives and powerful tools to study these cosmological correlators. In this talk, I will first briefly review this subject. Then, by incorporating the latest developments, I will “bootstrap” two types of inflationary correlators, which are most relevant for the next-generation observations. The first one is the contact correlators arising from large self-interactions of the inflaton. The second is the cosmological collider bispectra from the massive exchange diagrams with all possible boost-breaking interactions. Applying the bootstrap approach, we derive for the first time not only a complete set of these correlators systematically, but also their full shape information analytically. Since the de Sitter boost symmetries are broken in our consideration, the sizes of signals are boosted to be detectable for near-future experiments. We identify new features in these non-Gaussianity shapes, which provide interesting targets for the data analysis of upcoming surveys.

Zoom Meeting： 834 6695 7596 Password： 395040
https://dooyle.zoom.us/j/83466957596?pwd=cDg2eURyd25BRUtGZjN5M1dZZGFJZz09
Koushare live broadcast 蔻享直播 :
https://www.koushare.com/topic-hd/i/Euade

2022-06-15 (Wednesday) 3:00 PM CST [Webinar]

Short-bio:
Prof. Teruaki Suyama is an associate professor at Tokyo Institute of Technology since 2018. He obtained his doctorate from Kyoto University in 2007, after which he did postdoctoral research at the University of Tokyo and Louvain University. Since 2012, he has been a faculty member at the Research Center for the Early Universe (U.Tokyo), until he was appointed the current position. His research interest is to (mainly theoretically) investigate the horizon of our understanding of cosmology and gravitational physics we could reach in the era of the gravitational-wave astronomy. He is a lover of Belgian beers.

Abstract:
Gravitational waves from the distant sources are gravitationally lensed during their propagation through the intervening matter inhomogeneities before arriving at detectors. In this talk, I first give an overview of the gravitational lensing of gravitational waves, followed by a proposal made in the literature that the variance of the lensed waveform can be used to extract information of the matter power spectrum at very small scales and of low-mass dark halos. I will then show that the variance of the amplitude fluctuation and that of the phase fluctuation of the lensed waveform obey a simple consistency relation irrespective of the shape of the matter power spectrum. I will discuss about conditions under which this relation can be violated and provide some potential applications of the relation.

Zoom Meeting： 891 4812 4260 Password： 076606
https://dooyle.zoom.us/j/89148124260?pwd=d0prSjFnT3JRY1crSk9jNzVxV3MxUT09
Koushare live broadcast 蔻享直播 :
https://www.koushare.com/lives/room/413819

2022-06-22 (Wednesday) 9:00 AM CST [Webinar]

Short-bio:
Dr. Taishi Katsuragawa received his Ph.D. from Nagoya University in 2017. After working in postdoctoral research positions at Kobayashi-Maskawa Institute and Central China Normal University, he joined in Institute of Astrophysics of Central China Normal University as an associate professor. His research interests are the modified gravity theory and its applications to particle cosmology and astrophysics.

Abstract:
The F(R) gravity is one of the extensions of general relativity, and it has been investigated in various research fields. This talk focuses on the astrophysical application and demonstrates that adjusting the F(R) function can construct an arbitrary mass-radius relation of the compact star because the model-dependence of the equation of state and modification of gravity degenerate to each other. We also see that a non-integer curvature power correction is naturally introduced when the Schwarzschild spacetime is chosen as a boundary condition, which gives guidelines for model-building in F(R) gravity. Comparing with the reconstruction method known in cosmology and higher-curvature corrections to avoid curvature singularities in the dark energy model, we consider some problems in the existing studies on compact stars and discuss the prospects for future studies.

Zoom Meeting： 874 6858 5677 Password： 838803
https://dooyle.zoom.us/j/87468585677?pwd=OHNsTkJCRktWRkZhekw3Y1MrVkhoZz09
Koushare live broadcast 蔻享直播 :
https://www.koushare.com/topic-hd/i/Euade

2022-06-29 (Wednesday) 3:00 PM CST [Webinar]

Short-bio:
Dr. Nicolás Bernal received his Ph.D. from Paris-Saclay University in 2008. After postdoctoral appointments at the University of Barcelona, Lisboa University, Bonn University, and ICTP-SAIFR, he joined Universidad Antonio Nariño in Bogotá, Colombia, as an associate professor. His research interests are dark matter, beyond standard model phenomenology, and particle cosmology.

Abstract:
Rotating black holes (BHs) can efficiently transfer energy to the surrounding environment via superradiance. In particular, when the Compton length of a particle is comparable to the gravitational radius of a BH, the particle’s occupation number can be exponentially amplified. In this work, we investigate the effect of the primordial-black-hole (PBH) superradiant instabilities on the generation of heavy bosonic dark matter (DM) with a mass above ∼ 1 TeV. Additionally, we analyze its interplay with other purely gravitational and therefore unavoidable DM production mechanisms such as Hawking emission and the ultraviolet freeze-in. We find that superradiance can significantly increase the DM density produced by PBHs with respect to the case that only considers Hawking emission, and hence lower initial PBH densities are required.

Zoom Meeting： 891 4812 4260 Password： 076606
https://dooyle.zoom.us/j/89148124260?pwd=d0prSjFnT3JRY1crSk9jNzVxV3MxUT09
Koushare live broadcast 蔻享直播 :
https://www.koushare.com/topic-hd/i/Euade

2022-07-13 (Wednesday) 3:00 PM CST [Webinar]

Short-bio:
Professor of Physics, McGill University Department of Physics McGill University
Ph.D. in Physics, Harvard University, November 1983——

Professor of Physics, McGill University, Sept. 2004 -present
Professor of Physics, Brown University, July 1997 - June 2005
Associate Professor of Physics, Brown University, July 1991 to June 1997
Assistant Professor of Physics, Brown University, Sept. 1986 to June 1991
Postdoctoral Fellow, Dept. of Applied Mathematics and Theoretical Physics University of Cambridge, UK, October 1985 to August 1987
Postdoctoral Fellow, Institute for Theoretical Physics, University of California, Santa Barbara, Sept. 1983 to Sept. 1985

More than 400 publications with around 26000 citations.
More than 900 invited seminar and conference talks

Canadian Association of Physicists CAP Lifetime Achievement Award, 2021—
Canada Research Chair (Tier 1), Oct. 1 2004 - present

Research field: Theoretical cosmology

Abstract:
The Trans-Planckian Censorship Criterion and other arguments indicate that we need to go beyond an effective field theory analysis in order to understand the evolution of the very early universe. I will present a proposal to obtain an emergent metric space-time and an emergent early universe scenario from the BFSS matrix model, a proposed non-perturbative definition of superstring theory.

Zoom Meeting： 891 4812 4260 Password： 076606
https://dooyle.zoom.us/j/89148124260?pwd=d0prSjFnT3JRY1crSk9jNzVxV3MxUT09
Koushare live broadcast 蔻享直播 :
https://www.koushare.com/topic-hd/i/Euade

2022-07-27 (Wednesday) 3:00 PM CST [Webinar]

Short-bio:
Prof.Antonio took his Ph.D. in Syracuse University (NY, USA) with prof. Trodden. He has been a postdoctoral researcher in Sussex U. (Brighton, UK), Louvain U. (Louvain-la-Neuve, Belgium). Then he got a JSPS fellowship working at Tokyo U. of Science. Then he became a lecturer at IF (Naresuan U., Phitsanulok, Thailand). From the end of 2013 he has joined the Yukawa Institute For Theoretical Physics (Kyoto U.) as an associate professor. His research focuses on modified gravity models (applied to dark energy as well as inflation).

Abstract:
"I will describe the minimal theories and modified gravity I have been working recently on. In particular, I will describe why minimal theories might help resolve today's tensions in cosmology."

Zoom Meeting： 891 4812 4260 Password： 076606
https://dooyle.zoom.us/j/89148124260?pwd=d0prSjFnT3JRY1crSk9jNzVxV3MxUT09
Koushare live broadcast 蔻享直播 :
https://www.koushare.com/topic-hd/i/Euade

2022-08-08 (Monday) 3:00 PM CST [Webinar]

Short-bio:
Dr. Tao Liu's research focuses on particle physics and its connection with astronomy and cosmology. Dr. Tao Liu received his PhD in Physics at University of Pennsylvania in 2007. Then he hold a position of ``McCormick Fellow'' in Enrico Fermi Institute at University of Chicago during 2007-2010. After that, he moved to University of California at Santa Barbara to continue his postdoctoral research. He joined the Hong Kong University of Science and Technology (HKUST) in 2013 as a junior faculty. Now he is an associate professor at HKUST. He received the HKUST ``School of Science Research Award'' in 2016, and currently is the Project Coordinator/Principal Investigator of the Hong Kong UGC/RGC Collaborative Research Fund project ``Dark Matter and the Universe''.

Abstract:
Pulsar timing arrays (PTAs) consisting of widely distributed and well-timed millisecond pulsars can serve as a galactic interferometer to measure gravitational waves. With the same data acquired for PTAs, we have proposed (https://arxiv.org/abs/2111.10615) to develop pulsar polarization arrays (PPAs), to explore astrophysics and fundamental physics. As in the case of PTAs, PPAs are best suited to reveal temporal and spatial correlations at large scales that are hard to mimic by local noise. As a demonstration of the physical potential of PPAs, we considered the detection of ultralight axion-like dark matter (ALDM), through cosmic birefringence induced by its Chern-Simons coupling. Because of its tiny mass, the ultralight ALDM can be generated as a Bose-Einstein condensate, characterized by a strong wavy nature. In this talk, the speaker will give a detailed introduction to this topic and show how the PPAs can significantly enhance the detection of ALDM by correlating the their polarization data. 

Zoom Meeting： 879 6329 4916 Password： 129582
https://dooyle.zoom.us/j/87963294916?pwd=K2RSbmc0VnZPZWpkc1hTM2FyYi9nUT09
Koushare live broadcast 蔻享直播 :
https://www.koushare.com/lives/room/235406

2022-08-17 (Wednesday) 3:00 PM CST [Webinar]

Short-bio:
PhD—Kavli IPMU, University of Tokyo, Chiba, Japan in March 2015

Postdoctoral Research Fellow— Tokyo Institute of Technology(April 2015) —Stanford Institute for Theoretical Physics(October 2015)—Kyoto University(2017) —Institute for Cosmic Ray Research (April 2020 )

In April 2021, he joined Waseda Institute for Advanced Study, Waseda University as an assistant professor. Won Young Scientist Award The Physical Society of Japan(2022)

Research Interests—Inflation, Gravitational waves, Dark matter, Large scale structure

Abstract:
Having many on-going and upcoming experiments to detect them, we hope primordial gravitational waves (PGWs) imprinted in CMB B-mode will be observed in the near future. PGWs produced during inflation are the unique probe for very high energy physics beyond the reach of particle accelerators, and now is a good time to study what we can learn from them. In this webinar, I will discuss that much more information than the energy scale of inflation can be extracted from PGWs by using a model as an example. In the model, SU(2) gauge fields coupled to axion generate detectable PGWs with distinguishable signatures such as non-Gaussianity and circular polarization.

Zoom Meeting： 891 4812 4260 Password： 076606
https://dooyle.zoom.us/j/89148124260?pwd=d0prSjFnT3JRY1crSk9jNzVxV3MxUT09
Koushare live broadcast 蔻享直播 :
https://www.koushare.com/topic-hd/i/Euade

2022-09-14 (Wednesday) 3:00 PM CST [Webinar]

Short-bio:
PhD --- University of São Paulo, Brazil, December 2017

Research Associate --- Fermi National Accelerator Laboratory, 2018 - 2021

Postdoctoral Researcher Associate --- Northwestern University, 2018 - 2021

Postdoctoral Researcher Associate --- IPPP, Durham University, 2021 - present.

Research Interests: Neutrimo Physics, Black Hole Physics, Particle Phenomenology in the Early Universe.

Abstract:
Black Hole evaporation offers a unique method of particle production, unlike any other interaction process. In the Early Universe, such an evaporation can affect the baryon asymmetry produced via leptogenesis since heavy right-handed neutrinos can be emitted independently of the properties of the primordial plasma. However, there is also a large amount of entropy injected, which could dilute the generated asymmetry. We will explore in detail this interplay between Primordial Black Holes and Leptogenesis, determining the regions of the parameter space where the evaporation increases or erases the asymmetry.

Zoom Meeting： 891 4812 4260 Password： 076606
https://dooyle.zoom.us/j/89148124260?pwd=d0prSjFnT3JRY1crSk9jNzVxV3MxUT09
Koushare live broadcast 蔻享直播 :
https://www.koushare.com/topic-hd/i/Euade

2022-09-28 (Wednesday) 3:00 PM CST [Webinar]

Short-bio:
Dr. Fangxia An is a postdoc fellow based at the Purple Mountain Observatory in Nanjing China from July 2022. She obtained her Doctoral degree from the Purple Mountain Observatory in Nov. 2018. During Oct. 2016 to Oct. 2018, she studied at Durham University in UK as a joint PhD student. During Feb. 2019 to May 2022, she worked at Inter-University Institute for Data Intensive Astronomy in South Africa as a postdoc fellow.

Her research interests are galaxies formation and evolution, galaxy clusters/proto-clusters, large-scale structures of galaxies.

Abstract:
A well-determined radio spectrum for star-forming galaxy (SFG) is critically important for studies that are based on rest-frame radio power, especially those at high-redshift where k-corrections are generally extrapolated the most. In this talk, I will introduce two of our recently completed projects based on the MeerKAT(SKA pathfinder)+VLA+GMRT data in the COSMOS field and the LOFAR+GMRT+JVLA data in the ELAIS-N1 field. I will present our measured radio spectral indices between the observer-frame frequencies of 150-400, 400-610, 400-1300MHz, 1.3-3GHz, and 610-5000MHz and show the correlations between radio spectrum and physical properties of radio-selected SFGs. With these results, I will discuss the possible physical mechanisms that determine the radio spectrum of SFGs. I will also show how the adoption of these different radio spectral indices (from low- and high-frequency) in k-correction affects the study of far-infrared-radio correlation of SFGs.

Zoom Meeting： 891 4812 4260 Password： 076606
https://dooyle.zoom.us/j/89148124260?pwd=d0prSjFnT3JRY1crSk9jNzVxV3MxUT09
Koushare live broadcast 蔻享直播 :
https://www.koushare.com/topic-hd/i/Euade

2022-10-13 (Thursday) 9:00 AM CST [Webinar]

Short-bio:
Ph.D. in Physics, Tokyo institute of Technology, March 2017

IAS Postdoctoral Fellow, The HKUST Jockey Club Institute for Advanced Study, October 2021-present

Postdoctral researcher, Physics & Astronomy Department, Ohio University, April 2020- September 2021

Oversea Research Fellow of the Japan Society for the Promotion of Science, DAMTP, University of Cambridge (main), April 2018 – March 2020

Research Fellow of the Japan Society for the Promotion of Science (PD), Department of Physics, Tokyo Institute of Technology, April 2017 – March 2018

Research Fellow of the Japan Society for the Promotion of Science (DC2), Department of Physics, Tokyo Institute of Technology, April 2016 – March 2017

Research interest: cosmological perturbation theory and aim to find new observational approaches to the early Universe and high energy physics.

Abstract:
The inflationary 1-loop tensor power spectrum from an excited spectator scalar field is calculated. Recent studies on primordial black holes suggest that the inflationary curvature perturbation may be huge on small scales. An enhanced curvature perturbation may arise from a drastic enhancement of spectator scalar field fluctuations. In this letter, using the in-in formalism, we calculate 1-loop quantum corrections to primordial gravitational waves by such an excited spectator field with a sharp peak in momentum space. We find scale-invariant loop corrections in this full quantum setup, in contrast to the sharply peaked corrections in the previously calculated scalar-induced tensor modes. Especially, on super Hubble scales, the primordial gravitational waves are also amplified, which can be understood as a Bogolyubov transformation of the vacuum due to the excited scalar field. This mechanism allows us to probe the scalar field properties on extremely short-distance scales with the current and future cosmic microwave background and gravitational wave experiments, opening a novel window for inflationary cosmology.

Zoom Meeting： 819 0963 7699 Password： 607973
https://dooyle.zoom.us/j/81909637699?pwd=NUdycmV6Ny9NWElOVzRBLzNUNHQ4dz09
Koushare live broadcast 蔻享直播 :
https://www.koushare.com/topic-hd/i/Euade

2022-10-26 (Wednesday) 3:00 PM CST [Webinar]

Short-bio:
Prof. Aurel Schneider is an assistant professor at the University of Zurich, Switzerland, predominantly working on weak lensing and 21cm reionization science. Before this, he held research positions at ETH Zurich and the University of Sussex, United Kingdom.

Abstract:
Upcoming weak lensing and galaxy clustering surveys will push the frontier of cosmology towards small, highly nonlinear scales. I will discuss how to develop new theoretical tools to predict nonlinear structure formation (including baryons) at high precision. I will furthermore discuss how to apply these methods to current and future weak lensing surveys in order to learn something about cosmology, astrophysics, and the nature of dark matter.

Zoom Meeting： 891 4812 4260 Password： 076606
https://dooyle.zoom.us/j/89148124260?pwd=d0prSjFnT3JRY1crSk9jNzVxV3MxUT09
Koushare live broadcast 蔻享直播 :
https://www.koushare.com/topic-hd/i/Euade

2022-11-16 (Wednesday) 3:00 PM CST [Webinar]

Short-bio:
Prof. Roy has held a Research Chair at the University of the Western Cape since 2011, which supports a team of students and postdocs working on cosmology with the SKA and other surveys. He got his PhD from the University of Cape Town in 1980 (advisor George Ellis). He was at the University of Portsmouth in the UK during 1994-2010, where he was the founding Director of the Institute of Cosmology & Gravitation, one of the top cosmology research groups in the UK. His main interests are in the nature and applications of general relativistic effects in cosmology.

Abstract:
Tensions in the observed values of some key parameters of the concordance model of cosmology may indicate problems in the model itself. This motivates further independent tests of the model. I will describe a test of a key foundation of the concordance model - the Cosmological Principle. According to the Cosmological Principle, the Universe should be statistically isotropic. In particular, isotropy in the CMB must be consistent with isotropy in the galaxy distribution. This means that the dipole in the CMB should agree in direction and amplitude with the dipole in the galaxies. Current results suggest that there is a significant tension between the amplitudes of these dipoles. I will discuss some theoretical and observational issues that remain to be clarified before this can be declared as a new tension.

Zoom Meeting： 891 4812 4260 Password： 076606
https://dooyle.zoom.us/j/89148124260?pwd=d0prSjFnT3JRY1crSk9jNzVxV3MxUT09
Koushare live broadcast 蔻享直播 :
https://www.koushare.com/topic-hd/i/Euade

2022-11-30 (Wednesday) 3:00 PM CST [Webinar]

Short-bio:
Prof. Alexandre Refregier obtained his PhD in Physics from Columbia University, New York, NY, USA in 1997. Following this, he was a postdoc at Princeton University, Princeton, NJ, USA (1997 – 1999) and the University of Cambridge, Cambridge, UK (1999 - 2002). He was then Astrophysicist at CEA Saclay, France (2002 – 2011) and is currently Professor at ETH Zürich, Switzerland since 2011. His research interest are cosmology, structure formation, gravitation lensing and statistical methods.

Abstract:
Weak gravitational lensing is a unique technique to map the distribution of dark matter in the universe. It is also a sensitive probe of dark energy, large scale structures in the universe, and cosmological parameters. We will first briefly describe the principles of weak lensing. We will then review the current observational status of this field, highlighting several new measurements and the resulting sigma8 tension between different cosmological probes. We will then present recent measurements of non-gaussian statistics based on human-made summaries and machine  learning at map-level.

Zoom Meeting： 891 4812 4260 Password： 076606
https://dooyle.zoom.us/j/89148124260?pwd=d0prSjFnT3JRY1crSk9jNzVxV3MxUT09
Koushare live broadcast 蔻享直播 :
https://www.koushare.com/topic-hd/i/Euade

2022-12-07 (Wednesday) 9:00 AM CST [Webinar]

Short-bio:
Andrea V. Macciò is a Professor of Physics at New York University, Abu Dhabi and the Director of the Center for Astro, Particle and Planetary Physics.

Professor  Macciò is interested in understanding the nature and origin of the mysterious dark components of our cosmos: dark energy and dark matter, which account for 95 percent of the total energy/matter budget of the universe. In order to achieve this goal, he studies the formation and evolution of galaxies in such a dark universe via large computer numerical simulations

Abstract:
Our current understanding of galaxy formation is based on the presence of an elusive matter component: the Cold Dark Matter (CDM) This simple model has ben challenged many times in the past decade, mainly by galaxy observations on small scales: from the abundance of satellites, to the distribution of dark matter within galaxies, and more recently by the discovery of galaxies "without" dark matter. In my talk I will first revise all these claims with the help of cosmological numerical simulations of galaxy formation from the NIHAO project. I will then discuss whether there is indeed an observationally motivated need to abandon Cold Dark Matter and move beyond such a simple model.

Zoom Meeting： 865 7871 0701 Password： Ustc1234
https://dooyle.zoom.us/j/86578710701?pwd=Q2p5UEsxWjJ4ZWs4RmlPbnRpczNsdz09
Koushare live broadcast 蔻享直播 :
https://www.koushare.com/topic-hd/i/Euade

2022-12-21 (Wednesday) 3:00 PM CST [Webinar]

Short-bio:
Albert Escrivà is a JSPS postdoctoral fellow in the QG-lab at Nagoya University (Japan) since November 2022. Previously, he was a postdoctoral researcher at Brussels University (Belgium) for one year and finished his PhD in 2021 at the University of Barcelona (Spain). His current main research interest is devoted to the numerical simulation of primordial black holes.

Abstract:
Primordial Black Holes (PBHs) are black holes that could have been formed in the very early universe due to the collapse of large curvature fluctuations after inflation. PBHs are nowadays one of the most attractive and fascinating research areas in cosmology for their possible theoretical and observational implications. In this talk, I will review the physical process of PBH formation and its numerical simulation, focusing on the definition of "threshold for PBH formation" and its analytical estimation, which is essential to estimate the abundance of PBHs correctly. Moreover, I will present recent results about the formation of PBHs when a time-dependent equation of state is considered, which has a significant phenomenological impact compared with the standard case of a radiation-dominated era.

Zoom Meeting： 891 4812 4260 Password： 076606
https://dooyle.zoom.us/j/89148124260?pwd=d0prSjFnT3JRY1crSk9jNzVxV3MxUT09
Koushare live broadcast 蔻享直播 :
https://www.koushare.com/topic-hd/i/Euade

2023-01-11 (Wednesday) 9:00 PM CST [Webinar]

Short-bio:
Ricardo is a Beatriu de Pinós fellow at IFAE, the Institute for High Energy Physics at the U. Autónoma of Barcelona in Spain. He obtained his PhD in 2016 at the CP3-Origins Institute, University of Southern Denmark, and has held postdoctoral positions at the U. Barcelona, Nordita (Stockholm) and IFAE (Barcelona). His research has been devoted to topics in the interface between cosmology, axion physics and gravity including inflation, gravitational waves and the cosmic microwave background.

Abstract:
Primordial black holes with asteroid-like masses (10^{14-18} kg) can still account for all the dark matter. In this talk, I will discuss a new indirect probe of PBH dark matter. I will show that axions with masses in the 0.1eV-MeV range can form in clouds around such PBHs, via superradiance, and ultimately decay, if coupled to photons. The decay products will contribute to the galactic or extragalactic background flux at frequencies between the UV and the gamma-rays, depending on the axion mass. I will show that current data already constraints a large range of parameters and that searches for narrow lines with future experiments such as the Athena X-ray telescope will further test this co-existence of PBH dark matter and axions. If time allows I will also discuss recent work on another probe of axion physics: gravitational waves.

Zoom Meeting： 833 9022 1307 Password： 782677
https://dooyle.zoom.us/j/83390221307?pwd=MGpnQWgzS3IzWmFjbGd4d2RXWWZzQT09
Koushare live broadcast 蔻享直播 :
https://www.koushare.com/topic-hd/i/Euade

2023-01-25 (Wednesday) 9:00 PM CST [Webinar]

Short-bio:
Bachelor and Master degree at the University of Pisa (Italy);

PhD at the University of Geneva (Switzerland) under the supervision of Prof. Antonio Riotto;

Postdoc researcher at the University of Pennsylvania (United States).

Abstract:
Tidal Love numbers describe the deformability of compact objects under the presence of external tidal perturbations, and are found to be exactly zero for black holes. We discuss about their connection to the weak gravity conjecture and investigate the scenario of black holes dressed with an ultralight scalar field, addressing their detectability at future gravitational wave experiments.

Zoom Meeting： 833 9022 1307 Password： 782677
https://dooyle.zoom.us/j/83390221307?pwd=MGpnQWgzS3IzWmFjbGd4d2RXWWZzQT09
Koushare live broadcast 蔻享直播 :
https://www.koushare.com/topic-hd/i/Euade

2023-02-15 (Wednesday) 9:00 PM CST [Webinar]

Short-bio:
Regarding my bio, I am a Royal Society Dorothy Hodgkin Research Fellow at the University of Sheffield (UK). Previous to this I've been an Addison-Wheeler fellow at Durham University (UK), a postdoc at the University of Manchester (UK), and a Lagrange fellow at the IAP in Paris (France). I had my PhD in Rome at "La Sapienza" University.

Abstract:
The scenario that has been selected as the standard cosmological model is Lambda Cold Dark Matter (ΛCDM), which provides a remarkable fit to the bulk of available cosmological data. However, discrepancies among key cosmological parameters of the model have emerged with different statistical significance. While some portion of these discrepancies may be due to systematic errors, their persistence across probes can indicate a failure of the canonical ΛCDM model. I will review these tensions, showing some interesting extended cosmological scenarios that can alleviate them.

Zoom Meeting： 833 9022 1307 Password： 782677
https://dooyle.zoom.us/j/83390221307?pwd=MGpnQWgzS3IzWmFjbGd4d2RXWWZzQT09
Koushare live broadcast 蔻享直播 :
https://www.koushare.com/topic-hd/i/Euade

2023-02-22 (Wednesday) 9:00 AM CST [Webinar]

Short-bio:
Professor Celine Boehm is an Astroparticlephysicist who worked in the UK (Oxford, Durham), France (CNRS), Switzerland (CERN), Canada (Perimeter institute) and Australia (USYD).She is known for her work across Cosmology/Particle Physics/AstroparticlePhysics. 

Professor Boehm has been the lead of the space mission consortium ESA/Theia(leading more than 200 researchers in the collaboration)and was also the Head of School of Physics at the University of Sydney. Her work on dark matter has motivated a plethora ofnew experimentse.g.NA64,SENSEI, DAMIC, FASER,and new searches such as XENON1T,BELLE, DAPHNE, KLOE, etc. 

Professor Boehmwas the first to quantify the impact of dark matter interactions with the Standard Model particles on the CMB and large-scale-structure formation and also, with her collaborators, the first to perform N-body simulations of these scenarios to determine the number and properties of satellite companions of the milky Way. She further contributed to thefirst predictions of the CMB spectrum for the first relativistic extension of MOND (the so-called TeVeS theory).Her research topics are currently much broader and range from digital health to new technologies

Abstract:
In the talk, I will explore the historical reasons to explore sub-GeV dark matter scenarios and  will discuss the implications for structure formation. 

Zoom Meeting： 868 2491 7231 Password： Ustc1234 
https://dooyle.zoom.us/j/86824917231?pwd=MkNndTZVa2FpcEFJMnpsR2lHZjJpdz09
Koushare live broadcast 蔻享直播 :
https://www.koushare.com/topic-hd/i/Euade

2023-03-15 (Wednesday) 3:00 PM CST [Webinar]

Short-bio:
Professor Leandros Perivolaropoulos received his PhD from Brown University in 1991. After that, he was a postdoctoral fellow at the Harvard Center for Astrophysics 1991-1994 and at MIT 1994-95. He has been visiting associate professor at the physics department of the university of Crete in Greece (1996-99) and research fellow at the NCSR Demokritos research center in Athens Greece (1999-2002). Since 2002 he has been a faculty member (full Professor since 2011) at the physics department of the university of Ioannina in Greece. His expertise focuses on cosmology, dark energy, modified gravity on both theoretical aspects and model constraints using data analysis methods. He has authored 148 research papers with more than 7000 citations (h index 44) according to the database inspire. His recent extensive review 'Challenges for ΛCDM: An  update' published in 2022,  reviews the current status of the standard cosmological model and has received about 300 citations so far.

Abstract:
During the past few years it has become apparent that there is inconsistency between specific best fit parameter values of the standard LCDM model favored by different cosmological observations. These inconsistencies are known as tensions of ΛCDM. The most important of these tensions include the Hubble tension (5σ), the growth tension (2-3σ) and the large-scale dipole tension (3-4σ).

Thus, it is likely that new degrees of freedom are required that can extend the ΛCDM model in order to eliminate these inconsistencies. Such new degrees of freedom may originate from new dark fluids/fields and/or modified gravity. There are three sectors of the standard model that can accommodate such new degrees of freedom: The expansion rate/gravity of the Universe before the time of recombination (z=1100 early time models) when early time H0 calibrators are determined,  the expansion rate of the Universe between the time of recombination and redshift z=0.01 when the Hubble flow is detectab;e (late time models), and ultralate time physics (z<0.01) when distance probes (SnIa) are calibrated but the Hubble flow is undetectable due to peculiar velocities. I will discuss these three classes of models with emphasis on the ultralate time models and point out their strong and weak points.

Zoom Meeting： 891 4812 4260 Password： 076606
https://dooyle.zoom.us/j/89148124260?pwd=d0prSjFnT3JRY1crSk9jNzVxV3MxUT09
Koushare live broadcast 蔻享直播 :
https://www.koushare.com/topic-hd/i/Euade

2023-03-29 (Wednesday) 9:00 PM CST [Webinar]

Short-bio:
Prof. Oleg Lebedev, Obtained a PhD in physics from Virginia Tech (USA) in 1998 under the supervision of Lay Nam Chang. After graduating, held postdoctoral positions at the University of Sussex, DESY and CERN as well as a staff position at DESY (Hamburg). Since 2013, full professor at the University of Helsinki with a research focus on the interface between particle physics and cosmology.

Abstract:
I discuss particle production during and after inflation. Even if particles have only gravitational interactions, they can be produced copiously leading to overabundance of dark relics. I discuss the resulting constraints on stable particles and their implications for quantum gravity.

Zoom Meeting： 833 9022 1307 Password： 782677
https://dooyle.zoom.us/j/83390221307?pwd=MGpnQWgzS3IzWmFjbGd4d2RXWWZzQT09
Koushare live broadcast 蔻享直播 :
https://www.koushare.com/topic-hd/i/Euade

2023-04-12 (Wednesday) 9:00 AM CST [Webinar]

Short-bio:
Marilena Loverde is the Dr. Ann Nelson Endowed Associate Professor of Physics at the University of Washington. She received a B.A. in Physics and Mathematics from the University of California, Berkeley, a Ph.D. in Physics from Columbia University, and did postdoctoral studies at the Institute for Advanced Study in Princeton and at the University of Chicago. Prior to moving to the University of Washington, Loverde was an Assistant Professor Physics in the C.N. Yang Institute for Theoretical Physics at Stony Brook University. Loverde's research is centered on understanding the origin and evolution of structure in the Universe, from inflation until today. She is co-chair of the Maps to Parameters analysis working group for the CMB-S4 Experiment. 

Abstract:
Neutrinos and other light relic particles leave a number of imprints in the cosmic microwave background anisotropies and on maps of the large-scale structure of our Universe. These imprints can not only demonstrate the presence of these particles and constrain their masses, but can provide insight into their nature via signatures of interactions or other behavior that changes during the history of the Universe. I will describe this physics, present constraints on non-standard neutrino self-interactions and other forms of dark radiation from cosmic datasets. I will also discuss prospects for detecting neutrino mass and highlight how relic neutrinos force us to adopt new technology when modeling structures in the Universe today.

Zoom Meeting： 874 6858 5677 Password： 838803
https://dooyle.zoom.us/j/87468585677?pwd=OHNsTkJCRktWRkZhekw3Y1MrVkhoZz09
Koushare live broadcast 蔻享直播 :
https://www.koushare.com/topic-hd/i/Euade

2023-04-26 (Wednesday) 9:00 PM CST [Webinar]

Short-bio:
Paul Shah received his Ph.D. from Cambridge University in 1995 in Theoretical Physics, and has had a varied career in both academia and industry. He has been a postdoc working on quantum field theory, a satellite controller for the European Space Agency, and a financial derivatives trader in London, Chicago, Singapore and Tokyo for 20 years. Returning to academia in 2018, he now works in Department of Physics and Astronomy at University College London in the field of observational cosmology.

Abstract:
Edwin Hubble published his paper “A Relation between Distance and Radial Velocity among Extra-Galactic Nebulae” in 1929, but nearly 100 years later astronomers have still not settled on a value for Hubble’s constant. In particular, there is a significant tension between distance ladders calibrated with Cepheids and inverse distance ladders calibrated with the cosmic microwave background. Is this gap a sign that the well-established Lambda CDM model is somehow incomplete? Or are there unknown systematics? In this talk, I will review the methods used to calculate H0 and the potential issues they may face. In the spirit of the title, I will provide a buyer’s guide to the results and make recommendations. 

Zoom Meeting： 833 9022 1307 Password： 782677
https://dooyle.zoom.us/j/83390221307?pwd=MGpnQWgzS3IzWmFjbGd4d2RXWWZzQT09
Koushare live broadcast 蔻享直播 :
https://www.koushare.com/topic-hd/i/Euade

2023-05-10 (Wednesday) 3:00 PM CST [Webinar]

Short-bio:
Prof Tomohiro Harada is a professor of physics in Department of Physics, Rikkyo University, Japan. In 1999, he did his PhD from Kyoto University. Right after his PhD, he joined same institute as a postdoctoral position. Prior to moving to the Rikkyo University, he held postdoctoral positions at Waseda university, Queen Marry University of London. He works in the research field of general relativity, relativistic astrophysics and cosmology. His research interest includes black hole physics, gravitational waves, primordial black holes, gravitational collapse, spacetimes singularities and dark energy.

Abstract:
Shibata and Sasaki (1999) introduced the so-called compaction function. Since then, it has been empirically established that the maximum value of this function (or its volume-averaged counterpart) in the long-wavelength solutions gives a very robust threshold of primordial black hole formation. In this paper, we show that in spite of initial intention, the Shibata-Sasaki compaction function cannot be interpreted as the ratio of the mass excess to the areal radius in the constant-mean-curvature slice of their choice but coincides with that in the {\it comoving} slice up to a constant factor depending on the equation of state. We also discuss the gauge-(in)dependence of the legitimate compaction function, i.e., the ratio of the mass excess to the areal radius, in the long-wavelength solutions.

Zoom Meeting： 891 4812 4260 Password： 076606
https://dooyle.zoom.us/j/89148124260?pwd=d0prSjFnT3JRY1crSk9jNzVxV3MxUT09
Koushare live broadcast 蔻享直播 :
https://www.koushare.com/topic-hd/i/Euade

2023-05-24 (Wednesday) 9:00 AM CST [Webinar]

Short-bio:
Prof. Francis-Yan Cyr-Racine is an Assistant Professor at the University of New Mexico. He did his Ph.D in 2013 from University of British Columbia, BC, Canada. He was a Postdoctoral Fellow at Harvard University and W.M. Keck Institute for Space Studies CalTech. His research focuses on dark matter, gravitational lensing, neutrinos, and cosmology, with an emphasis on their relation with particle physics. The most interesting thing is he has been playing drums since his childhood. He has been a part of few musical bands through the years playing mostly rock and metal.

Abstract:
Since they naturally live in angular and redshift space, astronomical observations have a built-in invariance under rescaling all length scales in the problem. Breaking this invariance requires the use of anchors, such as known distances or energy scales, that can set the absolute scale of the problem. These anchors are fundamental to our knowledge of cosmological distances throughout the Universe, and provide the backbone on which much of our knowledge of cosmology rests. These pillars have recently come under renewed scrutiny due to apparently discrepant measurements of the Hubble constant, a very important cosmological quantity which sets the size and age of the observable Universe.  Here, we carefully examine the key anchors underpinning observations of the cosmic microwave background and baryon acoustic oscillations, finding ways to detach these measurements from their traditional anchors and fully restore their intrinsic scaling invariance. Not only can this help to understand the possible cause of the Hubble constant discrepancy, but it also sheds new light on the origins of cosmological constraints on new physics beyond the Standard Model. This in turn provides us with a general toolbox to design novel cosmological models that are automatically compatible with observations.

Zoom Meeting： 874 6858 5677 Password： 838803
https://dooyle.zoom.us/j/87468585677?pwd=OHNsTkJCRktWRkZhekw3Y1MrVkhoZz09
Koushare live broadcast 蔻享直播 :
https://www.koushare.com/topic-hd/i/Euade

2023-06-14 (Wednesday) 9:00 AM CST [Webinar]

Short-bio:
Prof. Stefano Profumo is a Professor of Physics and the Director of Physics Graduate Studies at the University of California, Santa Cruz, and the Deputy Director for Theory of the Santa Cruz Institute for Particle Physics. Profumo earned his MS in Theoretical Physics from Scuola Normale Superiore in Pisa, Italy, in 2001, and a PhD in Elementary Particles Theory from the International School for Advanced Studies in Trieste, Italy, in 2004. He joined the faculty at the University of California in 2007 after two postdoctoral positions, one at Florida State University (2004-5) and one at the California Institute for Technology (2005-7).

Profumo’s research work spans particle physics theory, cosmology, and high-energy astrophysics. He has published around 200 peer-reviewed articles, most of which on the topic of particle dark matter; his research work has been cited around 25,000 times, according to Google Scholar. He is the author of the textbook "An Introduction to Particle Dark Matter". Profumo is also an avid runner, biker, and triathlete.

Abstract:
In the age of gravitational wave astronomy and direct black hole imaging, the possibility that some of the black holes in the universe have a primordial, rather than stellar origin, and that they might be a non-negligible fraction of the cosmological dark matter, is quite intriguing. I will review the status of the field, and describe search strategies and future prospects for detection across many decades in black hole mass. I will also discuss how light primordial black holes could seed both baryonic and particle dark matter in the very early universe.

Zoom Meeting： 874 6858 5677 Password： 838803
https://dooyle.zoom.us/j/87468585677?pwd=OHNsTkJCRktWRkZhekw3Y1MrVkhoZz09
Koushare live broadcast 蔻享直播 :
https://www.koushare.com/topic-hd/i/Euade

2023-08-16 (Wednesday) 9:00 PM CST [Webinar]

Short-bio:
I am an assistant professor at the Department of Physical Sciences, Indian Institute of Science Education and Research (IISER), Berhampur. My research area is particle physics phenomenology. My current research focuses on various aspects of dark matter, neutrinos, and gravitational waves.

After my PhD from Harish-Chandra Research Institute, Allahabad in 2014, I joined Physical Reasearch Laboratory, Ahmedabad as postdoctoral fellow. Afterwards as National Post-Doctoral Fellow (NPDF) I joined Indian Institute of Technology Kharagpur in 2016. Before joining IISER Berhampur in 2019, I had a couple of post-doctoral positions in National Taiwan University (2018) and Asia Pacific Center for Theoretical Physics, Pohang (2018-19) respectively. Details of my publication can be found at the INSPIRE link.

Abstract:
Phase transitions in the early Universe can be a source of stochastic gravitational background. In addition, under certain circumstances primordial black holes can be produced from these phase transitions. We consider gravitational waves from this production mechanism of primordial black holes and from the gravitational interactions of those primordial black holes among themselves and other astrophysical black holes. We specifically focus on asynchronous bubble nucleation during a first order phase transition as the creation mechanism. We have used two benchmark phase transitions through which the primordial black holes and the primary gravitational wave spectra have been generated. We have considered binary systems and close hyperbolic interactions of primordial black holes with other primordial and astrophysical black holes as the source of the secondary part of the spectra. We show that this unique cumulative spectra have features which directly and indirectly depend on the specifics of the production mechanism.

Zoom Meeting： 833 9022 1307 Password： 782677
https://dooyle.zoom.us/j/83390221307?pwd=MGpnQWgzS3IzWmFjbGd4d2RXWWZzQT09
Koushare live broadcast 蔻享直播 :
https://www.koushare.com/topic-hd/i/Euade

2023-09-13 (Wednesday) 9:00 PM CST [Webinar]

Short-bio:
Oliver Philcox is a postdoctoral fellow at Columbia University and a Junior Fellow at the Simons Society of Fellows in New York City. He completed his PhD in Princeton University with Professors David Spergel and Matias Zaldarriaga and has previously conducted research at the University of Cambridge and Harvard University. Philcox is primarily interested in theoretical and experimental aspects of cosmology, particularly as applied to large scale structure and cosmic microwave background datasets.

Abstract:
Observations of the Cosmic Microwave Background (CMB) have cemented the notion that the large-scale Universe is both statistically homogeneous and isotropic. But is it invariant also under (point) reflections? Recently, observations of CMB polarization (through birefringence) and the distribution of galaxies (through four-point functions, or trispectra) have challenged this notion, and give tentative evidence for new parity-violating processes at work in the early or late Universe. In this talk, I will discuss these measurements, including their formulation and interpretation before commenting on possible explanations for the signal, both in terms of new physics and systematics. I will further discuss new analyses using the CMB temperature and polarization fluctuations, and their implications for parity violation in the Universe.

Zoom Meeting： 833 9022 1307 Password： 782677
https://dooyle.zoom.us/j/83390221307?pwd=MGpnQWgzS3IzWmFjbGd4d2RXWWZzQT09
Koushare live broadcast 蔻享直播 :
https://www.koushare.com/topic-hd/i/Euade

2023-09-27 (Wednesday) 9:00 PM CST [Webinar]

Short-bio:
Prof. Blake D. Sherwin obtained his  Ph.D. in Physics from Princeton University in 2013. Later on, he held research positions at  University of California and University of Cambridge. Currently he is a Professor of Cosmology and Astrophysics in University of Cambridge. Blake is a theoretical and observational cosmologist. He has research interests across CMB and large-scale structure, with a particular focus on measurements of the gravitational lensing of the CMB.

Abstract:
One of the most powerful tests of our cosmological model is to verify the predicted growth of large-scale structure with time. Intriguingly, many recent measurements have reported small discrepancies in such tests of structure growth ("the S8 tension"), which could hint at systematic errors or even new physics. Motivated by this puzzling situation, I will present new determinations of cosmic structure growth using CMB gravitational lensing measurements from the Atacama Cosmology Telescope (ACT). These ACT DR6 CMB lensing measurements allow us to directly map the mass distribution in projection out to high redshifts; new cross-correlations of CMB lensing with unWISE galaxies also allow us to probe the mass distribution tomographically. I will discuss the implications of our new lensing results for the validity of our standard cosmological model as well as for key cosmological parameters such as the neutrino mass and Hubble constant.

Zoom Meeting： 833 9022 1307 Password： 782677
https://dooyle.zoom.us/j/83390221307?pwd=MGpnQWgzS3IzWmFjbGd4d2RXWWZzQT09
Koushare live broadcast 蔻享直播 :
https://www.koushare.com/topic-hd/i/Euade

2023-10-11 (Wednesday) 9:00 PM CST [Webinar]

Short-bio:
Dr. Samuel Brieden is a postdoctoral research associate at the Institute for Astronomy at University of Edinburgh working within the research group of Prof. Florian Beutler. He is an active member of the Dark Energy Spectroscopic Instrument (DESI) and Euclid collaborations and is primarily interested in the interface between theoretical and observational cosmology. Samuel completed his PhD in University of Barcelona in 2022 with his thesis titled “From the Precision Era towards the Accuracy Era of Cosmology with DESI” outlining the catalog-level blinding procedure used by DESI and presenting “ShapeFit”: a novel methodology to get the most out of spectroscopic galaxy survey data in a model-agnostic way.

Samuel is very passionate for public outreach, he is co-chair of the DESI public outreach and education committee and runs the DESI social media accounts.

Abstract:
“It was the best of Hubble times, it was the worst of Hubble times, it was the h of new physics, it was the h of systematics, it was the season of photons and baryons, it was the season of Dark Matter and Dark Energy… In short, the period was so far like the present period, that some of its noisiest authorities insisted on its being received, for good or for evil, in the superlative degree of comparison only.”

This would probably be Dickens’ opening, if 84 years from now he had the chance to write a novel about the state of cosmology circa 2023.

On one hand (“best of Hubble times”) we have an observationally well-established model of cosmology, the standard flat LCDM model. On the other hand (“worst of Hubble times”) we do not understand the underlying nature of the universe’s “dark” ingredients contributing to 95% of its energy content. Beyond that, during the past decade cosmological “tensions” have emerged, most prominently the 5 sigma Hubble tension between direct measurements of the expansion rate at late times and its indirect inference from early times using the LCDM model, challenging either the late-time measurements (“systematics”?) or the model itself (“new physics”?). In short, when it comes to standard LCDM, either you love it, or you hate it.*

One particular probe of the expansion rate of the universe is the so-called baryon acoustic oscillation (BAO) probe obtained via the standard ruler method from spectroscopic galaxy surveys. In this “tale of two h’s” (based on https://arxiv.org/abs/2212.04522) I demonstrate that galaxy clustering data exhibit another standard ruler in addition to the acoustic scale (or sound horizon), namely the scale of matter-radiation equality k_eq.  I show how this scale is related to the shape of the power spectrum m, as measured in our recently developed “ShapeFit” method and present independent measurements of the Hubble parameter h obtained from both of these standard rulers. I briefly present the ongoing Dark Energy Spectroscopic Instrument (DESI) Survey and argue that its BAO, RSD and Shape measurements might well lead to a revolution in cosmology very soon.**

*Of course, there is also the middle ground, but this does not fit into the Dickens analogy.

**But as sort of anticipated by Dickens, after the revolution is before the next revolution.

Zoom Meeting： 833 9022 1307 Password： 782677
https://dooyle.zoom.us/j/83390221307?pwd=MGpnQWgzS3IzWmFjbGd4d2RXWWZzQT09
Koushare live broadcast 蔻享直播 :
https://www.koushare.com/topic-hd/i/Euade

2023-11-09 (Thursday) 12:30 PM CST [Webinar]

Short-bio:
Andrea Addazi (AA), born in Teramo, Italy, is currently Tenured Associate Professor in the College of Physics of Sichuan University, Chengdu, and Associate Researcher in LNF INFN, Rome, Italy.

Andrea Addazi is an expert in High Energy Physics, Cosmology and Quantum Gravity with more than 100 papers in international journals on these subjects, including Physical Review Letters (PRL), Physical Review D (PRD), Physical Letters B (PLB), JCAP, JHEP, European Physics Journal C (EPJC). He is currently working on gravitational wave phenomenology from early universe physics, first order phase transitions and primordial black holes.

Abstract:
In this talk, I will discuss recent results for New physics beyond the Standard Model of particles and Cosmology relating to Gravitational Waves signals in form of stochastic backgrounds. In particular, I will focus on the cases of First Order Phase Transitions and inflation for Primordial Black Holes Dark Matter. I will motivate why Dark Matter is one of the main reasons for searches of new gravitational waves signals from early Universe. Implications for space-based gravitational waves interferometers such as LISA, TianQing and TAIJI projects as well as for Pulsar-timing radio-astronomy such as NANOGrav are discussed.

Voov Meeting： 922 080 528

Koushare live broadcast 蔻享直播 :
https://www.koushare.com/lives/room/850585

2023-11-22 (Wednesday) 9:00 PM CST [Webinar]

Short-bio:
I did my Phd at ETH in Zurich, I then did postdocs first at the institute for Astronomy in Hawaii, and then at the University of Sussex, where I started to specialize in CMB lensing working on the Planck final release. Since 2020 I am assistant professor at University of Geneva.

Abstract:
The lensing signal imprinted on the CMB by large-scale structures will play an increasingly important part of the science returns of a number of CMB experiments. I will first review current lensing results and measurement techniques. For CMB polarization noise below the lensing B-power, methods more powerful but more complex than quadratic estimators must be used in order to achieve best recovery of the CMB lensing signal. This is particularly relevant for example for deep and high-resolution experiments aimed at constraining the primordial gravitational wave background from inflation, or for tightest constraints on neutrino masses and other parameters from the lensing spectrum. I will discuss progress in these optimized lensing reconstruction methods and their prospects, with a focus on the maximum a posteriori reconstruction method we have been developing in Geneva and its performance on simulations for r-constraints.

Zoom Meeting： 833 9022 1307 Password： 782677
https://dooyle.zoom.us/j/83390221307?pwd=MGpnQWgzS3IzWmFjbGd4d2RXWWZzQT09
Koushare live broadcast 蔻享直播 :
https://www.koushare.com/topic-hd/i/Euade

2023-11-29 (Wednesday) 3:00 PM CST [Webinar]

Short-bio:
Dr. Kai Schmitz did his PhD in 2012 from DESY Hamburg. From 2012-2015, he did his first postdoc at Kavli IPMU at the University of Tokyo in Japan, Second postdoc (2015-2018) at the Max Planck Institute for Nuclear Physiks in Heidelberg in Germany Third postdoc (2018-2019) at the University of Padua in Italy From 2019-2022, he worked as a Marie Curie Fellow of the European Commission in the CERN Theory Group in Geneva, Switzerland Since 2022, he is a Tenure-track junior professor at the University of Münster in Germany. In Münster, he is the leader of the "Particle Cosmology Münster" research group; see https://www.uni-muenster.de/Physik.TP/research/schmitz/ . At the same time, he is also a member of the NANOGrav pulsar timing array (PTA) collaboration; see https://nanograv.org/ . Within NANOGrav, And one of two Co-Chairs of the NANOGrav New Physics Working Group.

Abstract:
Pulsar Timing Array (PTA) collaborations around the globe recently announced compelling evidence for low-frequency gravitational waves permeating our entire Universe, that is, a gravitational-wave background (GWB) reaching us from all directions and at all times. This breakthrough achievement has important implications for astrophysics, as the GWB signal, if genuine, is likely to originate from a cosmic population of supermassive black holes orbiting each other at the centers of galaxies. As I will illustrate in this talk, the new PTA data is, however, also of great interest to the high-energy physics community, as it allows to probe a broad range of particle physics models of the early Universe that predict the generation of a cosmological GWB in the Big Bang. In this sense, the PTA data opens a new window onto the very early Universe and enables particle physicists to constrain scenarios of new physics beyond the Standard Model at extremely high energies. In my talk, I will give an overview of these searches for new physics at the PTA frontier and highlight several cosmological scenarios that underline the relevance of PTA observations for fundamental problems such as dark matter, neutrino masses, and the matter-antimatter asymmetry of the Universe. Finally, I will conclude with a brief outlook on future measurements that may help in discriminating between a GWB signal of astrophysical origin and a GWB signal from the Big Bang.

Zoom Meeting： 891 4812 4260 Password： 076606
https://dooyle.zoom.us/j/89148124260?pwd=d0prSjFnT3JRY1crSk9jNzVxV3MxUT09
Koushare live broadcast 蔻享直播 :
https://www.koushare.com/topic-hd/i/Euade

2023-12-13 (Wednesday) 9:00 PM CST [Webinar]

Short-bio:
Dr. Andrina Nicola completed her doctoral studies in 2018 at ETH Zurich and subsequently became a Postdoctoral Research Associate at the Department of Astrophysical Sciences at Princeton University. Her current research centers on the intersection of theoretical and observational cosmology. She is actively involved in developing methodologies to integrate data from various cosmological sources, aiming to enhance the precision of cosmological models and gain insights into the enigmatic components of the universe—Dark Matter and Dark Energy.

Abstract:
The clustering properties of galaxies are a powerful cosmological probe that has the potential to provide tight constraints on the late as well as the early Universe. Upcoming surveys such as LSST will deliver large galaxy samples, which will require tight control of systematic uncertainties. In this talk, I will present two analyses undertaken by the LSST DESC: I will first describe the results from a photometric galaxy clustering analysis using HSC Y1 data. In a second part of the talk, I will discuss the DESC bias challenge, a project aimed at identifying nonlinear galaxy bias models suitable for high-precision surveys.

Zoom Meeting： 833 9022 1307 Password： 782677
https://dooyle.zoom.us/j/83390221307?pwd=MGpnQWgzS3IzWmFjbGd4d2RXWWZzQT09
Koushare live broadcast 蔻享直播 :
https://www.koushare.com/topic-hd/i/Euade

2024-01-17 (Wednesday) 9:00 AM CST [Webinar]

Short-bio:
Julian Muñoz is an Assistant Professor in the Department Astronomy at the University of Texas at Austin since 2023. He finished his Bachelor’s degree in Physics in 2013 at the Complutense University of Madrid, and his PhD in Physics at Johns Hopkins University in 2017. After that, Julian was a postdoctoral fellow at the Harvard Physics Department until 2020, and a Clay Fellow at the Harvard-Smithsonian Center for Astrophysics until 2022. Julian works on understanding the elusive dark matter and its connection to the formation of the first galaxies. He uses techniques ranging from pen-and-paper calculations to computer simulations to confront his theories to cosmological observations. He is best known for his work on detecting dark matter with the 21-cm signal, and for developing a new standard ruler at high redshifts. He has recently been selected one of ScienceNews 10 scientists to watch in 2023.

Abstract:
The 21-cm line of hydrogen holds a wealth of information about the cosmic-dawn era. Unearthing this information is, however, complicated by nonlinear and nonlocal astrophysics, which are traditionally modeled through simulations. In this talk I will present an effective model to find the 21-cm signal during cosmic dawn fully analytically. This model is implemented in the public Zeus21 code, which takes seconds to run on a laptop and has negligible memory requirements. I will review the physics of cosmic dawn,  compare Zeus21 with state-of-the-art semi-numerical simulations, and show how to use it to extract cosmology and astrophysics from measurements of the 21-cm power spectrum. I will show how to use the upcoming data from 21-cm and JWST to measure structure formation at smaller scales—and earlier times—than ever before.

Zoom Meeting： 996 9118 3315 Password： 750937
https://zoom.us/j/99691183315?pwd=YlFxcXF4T2xaUkpqaCt2MWoyNVlRUT09
Koushare live broadcast 蔻享直播 :
https://www.koushare.com/topic-hd/i/Euade

2024-01-24 (Wednesday) 3:00 PM CST [Webinar]

Short-bio:
Ding Ding obtained his BSc from Lanzhou University in 2016. He then went on to complete his doctorate in Pennsylvania State University in 2022. He has been a post-doc at Fudan University from 2022-present. His main interests include cosmology, gravity and effective quantum dynamics.

Abstract:
Quantum fluctuations can be thought of as new degrees-of-freedom (DoFs) on top of the original classical system. In this talk, I will introduce a (canonical) effective framework that encodes quantum fluctuations as additional independent DoFs within an enlarged phase space. In this framework, there is a dynamic two-way communication between classical variables and quantum fluctuations, making it suitable for describing time-dependent quantum backreaction. I will apply our effective framework to examples in both flat and curved spacetimes. We will discover the key roles played by spatial symmetries and the uncertainty principle. The former helps us decouple fluctuations from each other and minimize backreaction on background inhomogeneities. The uncertainty principle, on the other hand, will help us select out minimal-energy configurations. At the leading order, these configurations coincide with ones dictated by textbook (1PI) effective potentials. If time permits I will mention some potential future applications.

Zoom Meeting： 999 7323 5923 Password： 848214
https://zoom.us/j/99973235923?pwd=RExmaEZoRU1HaXhCTEVHSGtiVzh0Zz09
Koushare live broadcast 蔻享直播 :
https://www.koushare.com/topic-hd/i/Euade

2024-03-20 (Wednesday) 9:00 PM CST [Webinar]

Short-bio:
Dr. Guillem Domenech leads an independent research group at the Institute for Theoretical Physics at the Leibniz University Hannover under the Emmy Noether Programme. His main research interests include theories of gravity and physics of the early universe. He is known for his contributions to the generation of secondary gravitational waves from primordial fluctuations. He did his doctorate course at the Yukawa Institute for Theoretical Physics, Kyoto University, under the supervision of Misao Sasaki. Frst postdoc was at the Institute for Theoretical Physics, Heidelberg University, under the supervision of Christof Wetterich. Later, he was a Marie-Curie Fellini Fellow in the cosmology group at the Istituto Nazionale di Fisica Nucleare, Sezione di Padova, under the supervision of Sabino Matarrese. 

Abstract:
There are hints of a Gravitational Wave background at pulsar timing arrays. The GW background could be due to the mergers of supermassive black holes, but it could have a cosmic origin. In this respect, one possibility is that the reported signal is the GW background associated with the formation of sub-solar mass primordial black holes, the so-called induced GWs. In this talk, I will provide a general overview of the induced GW interpretation of the PTA results. I will also discuss the implications for the PBH counterpart and the physics of the very early universe, considering CMB bounds on GWs and microlensing bounds on PBHs simultaneously.

Voov Meeting： 927-0477-1948
https://voovmeeting.com/dm/tRkSaNwQv37B
Koushare live broadcast 蔻享直播 :
https://www.koushare.com/live/details/32996

2024-04-10 (Wednesday) 9:00 AM CST [Webinar]

Short-bio:
In 2020, Dr. Gonzalo Alonso Alvarez did his Ph.D from Heidelberg University Germany. Right after his doctorate, he joined McGill as postdoc fellow. Currently, he is a Post Doctoral Fellow at Department of Physics, University of Toronto. His main research interest lies in Cosmology and early Universe.  

Abstract:
Increasing evidence for a stochastic gravitational background is being collected at pulsar timing arrays. The most plausible origin of the signal is the cumulative strain from the mergers of supermassive black holes at the center of galaxies across the history of the universe. I will discuss how the impact of dark matter dynamical friction on the black hole binary evolution can address some of the questions that this discovery raises. This includes the solution of the “final parsec problem” by which mergers would otherwise stall before gravitational wave emission can drive the coalesce. I will argue that the observational data favor the existence of dark matter self interactions with a cross-section and velocity dependence consistent with the ones capable of solving the small-scale structure problems of collisionless cold dark matter.

Voov Meeting： 315-0399-9274
https://voovmeeting.com/dm/871sXfNS2CD6
Koushare live broadcast 蔻享直播 :
https://www.koushare.com/live/details/32996

2024-05-08 (Wednesday) 9:00 PM CST [Webinar]

Short-bio:
Prof. Glenn Starkman is Distinguished University Professor and Vice-Chair of Physics,  and Professor of Astronomy at  Case Western Reserve University, in Cleveland, Ohio, USA. Glenn received his Bachelor's degree at his hometown University of Toronto, and followed up with PhD work in Physics with Savas Dimopoulos at Stanford University.  After postdocs at the Institute for Advanced Study, in Princeton, and the Canadian Institute for Theoretical Astrophysics, back in Toronto, he took up his current position at Case Western.   

Abstract:
We have long celebrated the great success of cosmology in predicting the observed properties of the cosmic microwave background.  And yet, for well over two decades there has been consistent and slowly mounting evidence that on large scales the CMB is anomalous.   The evidence is consistent from experiment to experiment and it implies the violation of statistical isotropy.   I will discuss this evidence, why it is so compelling, and where it may be pointing us.

Voov Meeting： 927-0477-1948
https://voovmeeting.com/dm/tRkSaNwQv37B
Koushare live broadcast 蔻享直播 :
https://www.koushare.com/live/details/32996

2024-06-05 (Wednesday) 9:00 AM CST [Webinar]

Short-bio:
Dr. Katsuki Aoki completed his Ph.D. in Physics at Waseda University, Japan, in March 2017. Subsequently, he joined Waseda University as an Assistant Professor. From 2019 to 2022, he served as a Research Assistant Professor at Kyoto University. Currently, he holds the position of Program-Specific Assistant Professor at Kyoto University. His research interests include effective field theory approaches to cosmology and cosmological perturbation theory.   

Abstract:
Effective field theory (EFT) allows a universal description of physical systems under assumed symmetries and has been used to systematically investigate various dark energy (DE) scenarios. However, the so-called EFT of DE focuses on a specific cosmological scenario, the universe driven by a scalar field, and cannot cover other cosmological scenarios. In this talk, I will present a unified description of the EFT of DE that accommodates both scalar-tensor and vector-tensor theories, and discuss universal distinctions of DE scenarios with different underlying symmetries. In particular, I will show that the vectorial nature of DE generically prevents modifications of gravity and the shift symmetry implies a phantom DE, wDE < -1. The latter is particularly interesting in light of the latest result of the DESI+CMB combination as the observational verification of wDE > -1 can rule out shift-symmetric theories including vector-tensor theories in one shot.

Voov Meeting： 439-0451-8855
https://voovmeeting.com/dm/HCwDzLGO7xr6
Koushare live broadcast 蔻享直播 :
https://www.koushare.com/live/details/34727

2024-06-26 (Wednesday) 3:00 PM CST [Webinar]

Short-bio:
Prof. Tsutomu Kobayashi completed his Ph.D. in Physics at Kyoto University in 2006. He then pursued postdoctoral research from 2006 to 2011 at the Tokyo Institute of Technology, Waseda University, and the Research Center for the Early Universe (RESCEU) at the University of Tokyo. In 2011, he became an Assistant Professor at the Hakubi Center, Kyoto University. From 2012 to 2019, he served as an Associate Professor at Rikkyo University, where he has been a Professor since 2019. Prof. Tsutomu Kobayashi,s research interests include the physics of the early universe, such as inflation and its alternatives, testing modified gravity with astrophysical, cosmological, and gravitational-wave observations, and probing the nature of gravity in the strong-field regime.   

Abstract:
We study the weak-gravity regime of higher-order scalar-tensor theories that are degenerate in the unitary gauge. In a certain subset of theories analogous to Lorentz-violating scalar-tensor theories, we show that the Vainshtein mechanism due to nonlinear derivative interactions does not work. For this family of theories we determine all the PPN parameters in terms of the EFT of dark energy parameters and discuss the experimental bounds. We present a Lagrangian of a ghost-free higher-order scalar-tensor theory characterized by a single function of the kinetic term of the scalar field whose PPN parameters have the same values as in general relativity.

Voov Meeting： 337-071-589
https://voovmeeting.com/dm/ZcFhaE04S9bj
Koushare live broadcast 蔻享直播 :
https://www.koushare.com/live/details/34727

2024-07-05 (Friday) 3:30 PM CST [Webinar]

Short-bio:
David Wu (吴瀚之) completed his undergraduate studies at Caltech and is currently a third-year PhD student in the Center of Fundamental Laws in the Department of Physics at Harvard University, under the supervision of Prof. Cumrun Vafa. His research interests lie primarily within the swampland program, which aims to identify consistency conditions that theories of quantum gravity must collectively satisfy using both top-down and bottom-up approaches   

Abstract:
In a quantum theory of gravity, the species scale can be defined as the scale at which the Einstein effective action breaks down and higher-curvature corrections become important. Understanding properties of the species scale can shed light on fundamental aspects of quantum gravity and have important applications to phenomenology. In this talk, I will introduce the species scale as a moduli-dependent quantity in supersymmetric theories and explore a diverse set of examples within string theory. I will also discuss a relation between the species scale and the Trans-Planckian censorship conjecture.

Voov Meeting： 736-091-089
https://voovmeeting.com/dm/T7tTygFAI89s
Koushare live broadcast 蔻享直播 :
https://www.koushare.com/live/details/34727

2024-07-24 (Wednesday) 3:00 PM CST [Webinar]

Short-bio:
Luca Amendola obtained his PhD in 1993 at the University of Rome "La Sapienza" (Italy); he worked at the Italian Institute of Astrophysics until 2009, when he became  professor of Theoretical Physics at the University of Heidelberg (Germany). He works mainly in theoretical cosmology and cosmological data analysis.   

Abstract:
A new avenue was recently developed for analyzing large-scale structure data with a model-independent approach, in which the linear power spectrum shape is parametrized with a large number of freely varying wavebands rather than by assuming specific cosmological models. Here we show, using a Fisher matrix approach, that the precision of this method for the case of the one-loop power spectrum is greatly improved with the inclusion of the tree-level bispectrum. We also show that accuracy can be similarly improved by employing perturbation theory kernels whose structure is entirely determined by symmetries instead of evolution equations valid in particular models (like in the usual Einstein-de Sitter approximation). We also present preliminary results of an application to real data from the BOSS survey. Finally, we show how these results can test cosmic geometry and gravity in a model-independent way.

Voov Meeting： 337-071-589
https://voovmeeting.com/dm/ZcFhaE04S9bj
Koushare live broadcast 蔻享直播 :
https://www.koushare.com/live/details/34727

2024-09-04 (Wednesday) 3:00 PM CST [Webinar]

Short-bio:
Joe Zuntz is a Professor of Cosmology at the University of Edinburgh, studying the measurements and use of weak gravitational lensing and galaxy clustering statistics, and practical cosmological inference   

Abstract:
The Vera Rubin Observatory, currently under construction in Chile, will host the new Simonyi Survey Telescope and conduct the Legacy Survey of Space and Time (LSST). The survey will map 18,000 square degrees of the extragalactic sky in the near infrared to depths of 25-27 magnitudes across optical and near-infrared bands. Among many science applications is the analysis of measurements of weak gravitational lensing and galaxy clustering, which will determine the growth of cosmic structure to high redshifts. These measurements will permit let us explore the history of dark energy and the cosmological parameters to unprecedented precision and accuracy. In this talk I will discuss these measurements in the context of other recent surveys, and the challenges of completing them.

Voov Meeting： 657-0796-6742
https://voovmeeting.com/dm/ckUGlzRMN0NS
Koushare live broadcast 蔻享直播 :
https://www.koushare.com/live/details/34727

2024-10-09 (Wednesday) 3:00 PM CST [Webinar]

Short-bio:
Prof. Stefano Camera earned his PhD in Physics and Astrophysics in 2011 at the University of Turin, under the supervision of Antonaldo Diaferio and co-supervised by Alan Heavens at the Royal Observatory of Edinburgh. He held postdoctoral positions, including as an FCT Research Fellow, at the University of Lisbon (2011-2014) and the Jodrell Bank Centre for Astrophysics at the University of Manchester (2014-2017). He became a Rita Levi Montalcini Assistant Professor at the University of Turin in 2017 and has been an Associate Professor since 2020. Prof. Camera holds "Builder" status in the Euclid Consortium and coordinates one of its key cosmology projects. He also chaired the SKA Cosmology Science Working Group from 2020 to 2024.   

Abstract:
In my talk, I shall review the main research projects I'm involved with, which all revolve around the added value of cross-correlations between various cosmological observables, as well as among cosmological and astrophysical observables, to shed new light onto pressing open questions in cosmology and astrophysics.  In particular, I shall touch upon the possibility of detecting relativistic effects on cosmological scales - which will allow us to deepen our understanding of dark energy and modified gravity - and the use of cosmological data to study the anisotropies of ultra-high energy cosmic rays.  All this in the view of the new generation of cosmological experiments across the electromagnetic spectrum, like the SKA Observatory in the radio band, theEuclid satellite at optical/near-infrared wavelengths.

Voov Meeting： 450-410-343
https://meeting.tencent.com/dm/N0AsIw7Bsj4y
Koushare live broadcast 蔻享直播 :
https://www.koushare.com/live/details/34727

2024-11-20 (Wednesday) 3:00 PM CST [Webinar]

Short-bio:
Dr. Sebastian Zell completed his graduate studies at the Max Planck Institute for Physics and Ludwig Maximilian University of Munich, where he earned his PhD in 2019 under the supervision of Gia Dvali. Subsequently, he went on to work at École Polytechnique Fédérale de Lausanne and at UCLouvain, before taking up his current postdoc position at Ludwig Maximilian University of Munich. His research is based at the interface of particle physics and cosmology, with topics ranging from gravity, inflation, black holes and dark matter to axions, quantum information and the mass scales of Nature.   

Abstract:
First reviewing black hole evaporation, I will discuss that the semi-classical calculation of particle production is expected to break down at the latest once half of the mass is lost. Quantum analogue systems, which imitate important properties of a black hole such as its entropy, provide strong indications for a drastic slowdown of evaporation. Therefore, small primordial black holes (PBHs) can both become viable dark matter candidates and provide a unique window on quantum gravity. Finally, I will turn to the inflationary production of small PBHs. A sufficiently small mass alleviates any tension with CMB observations and scalar-induced gravitational waves (GW) can yield an observable signal. I will highlight the need to develop new experiments for high-frequency GW detection in the kHz to MHz range.

Voov Meeting： 973-5661-5791
https://meeting.tencent.com/dm/jZxkr6XiXIkO
Koushare live broadcast 蔻享直播 :
https://www.koushare.com/live/details/34727

2025-01-22 (Wednesday) 3:00 PM CST [Webinar]

Short-bio:
Prof. Akarsu, a Turkish cosmologist, currently holds a full professorship at Istanbul Technical University (ITU). He earned his PhD in astrophysics from Ege University in 2010, specializing in cosmology. During his doctoral studies, he conducted research as a visiting PhD student/researcher at the University of Cambridge. In 2010, supported by the Turkish Academy of Sciences, he began his postdoctoral work at Koç University, focusing on theoretical cosmology, before being appointed as an associate professor at ITU in 2015. Prof. Akarsu's primary research interests include theoretical and observational cosmology, as well as modified gravity theories. In recent years, he has focused on understanding and resolving cosmological tensions. He is the co-proposer of the graduated dark energy (gDE) model, which led to the late time AdS-to-dS transition conjecture and the development of the $\Lambda_{\rm s}$CDM paradigm, regarded as one of the most promising approaches for addressing multiple cosmological tensions. He has been a regular guest scientist at the ICTP in Italy since 2010 and has received two of Turkey's most prestigious awards for young scientists, presented by the Science Academy and the Turkish Academy of Sciences.   

Abstract:
Sign-switching cosmological constant cold dark matter ($\Lambda_{\rm s}$CDM) cosmology has emerged as a compelling new paradigm, demonstrating unprecedented success in aligning with observational data from various datasets and effectively addressing major cosmological tensions, such as the $H_0$ and $S_8$ tensions. This model is characterized by a minimal but non-trivial deviation from the standard $\Lambda$CDM framework, proposing a rapid Anti-de Sitter (AdS) to de Sitter (dS) transition in the late universe ($z_\dagger \sim 1.7$), as conjectured through findings in graduated dark energy (gDE) model. In this talk, we will first provide a concise introduction to $\Lambda_{\rm s}$CDM cosmology. We will then discuss the latest theoretical and observational advances that position $\Lambda_{\rm s}$CDM model as a promising candidate or guide for a new concordance cosmological model of the Universe.

Voov Meeting： 973-5661-5791
https://meeting.tencent.com/dm/jZxkr6XiXIkO
Koushare live broadcast 蔻享直播 :
https://www.koushare.com/live/details/34727