LeCosPA Cosmology and Particle Astrophysics Seminar
Next seminar:
-
Note: There will be 2 talks next week. One on Monday at 11:00 UTC+8, and another on Thursday at 11:00 UTC+8.
-
Location: Room 7S1, Chee-Chun Leung Cosmology Hall, NTU 國立臺灣大學次震宇宙館7樓7S1會議室
-
Or join the seminar online via Skype (← click the link) Name: LeCosPA Seminar
-
Talk #1:
-
Date and time [YYYY-MM-DD hh:mm]: 2023-05-29 11:00-12:00 (UTC+8)
-
Speaker: Dr. Junsup Shim (ASIAA)
-
Title: Identifying Cosmic Voids as Massive Cluster Counterparts
-
Abstract:
We develop a method to identify cosmic voids from matter/galaxy density fields by adopting a physically-motivated void-cluster correspondence theory that voids are the counterpart of massive clusters. To prove the concept we use a pair of LCDM simulations, a reference and its initial density-inverted mirror simulation, and study the relation between the effective size of voids and the mass of corresponding clusters. We study the voids corresponding to the halos more massive than 10^{13}Msol/h and find a power-law scaling relation between the void size and the corresponding cluster mass. We also find that the density profile of the identified voids follows a universal functional form. Based on these findings, we propose a method to identify cluster-counterpart voids directly from the matter/galaxy density field without their mirror information. The completeness and reliability we achieve in recovering voids corresponding to clusters more massive than 3×10^{14}Msol/h are about 70-74 % for matter density fields and 60-67% for galaxy density fields. Our results demonstrate that we can apply this method to the galaxy redshift survey data to identify cosmic voids corresponding statistically to the galaxy clusters in a given mass range.
Talk #2:
-
Date and time [YYYY-MM-DD hh:mm]: 2023-06-01 11:00-12:00 (UTC+8)
-
Speaker: Prof. Jun’ichi Yokoyama (RESCEU, Tokyo University)
-
Title: Generation of neutrino dark matter, baryon asymmetry and radiation after quintessential inflation
-
Abstract:
We construct a model explaining dark matter, baryon asymmetry and reheating in quintessential inflation model. Three generations of right-handed neutrinos having hierarchical masses. Three generations of right handed neutrino explain dark matter and baryon asymmetry, while reheating is realized by spinodal instabilities of the Standard Model Higgs field induced by the non-minimal coupling to the scalar curvature, which can solve overproduction of gravitons and curvature perturbation created by the Higgs condensation.
General Information:
-
Time: 11:00-12:00 (UTC+8), every Monday (* may be different for some special talks)
-
Location: Room 7S1, Chee-Chun Leung Cosmology Hall, NTU 國立臺灣大學次震宇宙館7樓7S1會議室 (see the map below)
-
Organizers :
-
Dr. Hsu-Wen Chiang (contact: b98202036@ntu.edu.tw)
Dr. Shih-Hao Wang (contact: wsh4180@gmail.com)
List of Seminar Speakers and Talk Titles
2023 Spring (also available in our Wiki)
Date [YYYY/MM/DD] | Name (Affiliation) | Title and Abstract |
2023/03/06 | Dr. Shih-Hao Wang (National Taiwan University) |
Detecting Ultra-High Energy Particles with TAROGE-M Radio Array on Antarctic High Mountain Detecting ultra-high energy (UHE, beyond 1017 eV) cosmic rays and neutrinos is crucial for unraveling their yet elusive origin and testing fundamental physics at energies and distances not achievable by accelerator experiments. Particularly, UHE neutrino, expected to exist but not yet detected, is the unique cosmic messenger bringing information deep in the universe and the most energetic stellar objects. UHE particles can be efficiently detected by coherent radio pulses emitted by air showers induced by their interaction with the atmosphere. One unexpected discovery of this technique is the so-called ANITA anomalous events (AAEs), having feature of upward-going UHE air showers but cannot be explained by tau neutrinos.TAROGE-M is a radio antenna station operating at 180-450 MHz atop 2.7 km-high Mt. Melbourne in Antarctica for detecting UHE air showers in near-horizontal directions. Besides the detection of cosmic rays and Earth-skimming tau neutrinos, its primary goal is to verify the origin of AAEs. The detection concept and advantages, the first result on cosmic ray detection, and the current status of TAROGE-M will be reviewed in this talk. |
2023/03/13 | Prof. Dong-Ham Yeom (Pusan National University) |
Euclidean quantum gravity and information loss paradox: past and future I first summarize recent progresses on the Euclidean path integral approach as a solution to the information loss paradox. We may extend the topics for the ultimate understanding of the information recovery of evaporating black holes. I will carefully suggest possible future research topics. |
2023/03/14 11:20 | Prof. Misao Sasaki (YITP, Kyoto University/IPMU, Tokyo University/LeCosPA, National Taiwan University) |
Primordial Black Holes from Inflation The rapid progress in gravitational wave astrophysics/cosmology has made projections of detecting signatures of PBHs quite feasible. Parallel to it, various models of inflation that produce PBHs have been proposed. In this talk I first overview the PBH formation from inflation, and introduce some recently-found novel mechanisms that lead to it. |
2023/03/20 | Prof. Masahiro Hotta (Tohoku University) |
Expanding Edges of Quantum Hall Systems in a Cosmology Language - Hawking Radiation from de Sitter Horizon in Edge Modes Expanding edge experiments are promising to open new physics windows of quantum Hall systems. In a static edge, the edge excitation, which is described by free fields decoupled with the bulk dynamics, is gapless, and the dynamics preserve conformal symmetry. When the edge expands, such properties need not be preserved. We formulate a quantum field theory in 1+1 dimensional curved spacetimes to analyze the edge dynamics. We propose methods to address the following questions using edge waveforms from the expanding region: Does the conformal symmetry survive? Is the nonlinear interaction of the edge excitations induced by edge expansion? Do the edge excitations interact with the bulk excitations? We additionally show that the expanding edges can be regarded as expanding universe simulators of two-dimensional dilaton-gravity models, including the Jackiw-Teitelboim gravity model. As an application, we point out that our theoretical setup might simulate emission of analog Hawking radiation with the Gibbons-Hawking temperature from the future de Sitter horizon formed in the expanding edge region. |
2023/03/27 | Dr. Che-Yu Chen (Academia Sinica -> RIKEN, Japan) |
Testing black hole eikonal correspondence
Adopting geometric-optics approximations in black hole spacetimes enables the construction of a mapping between black hole images and eikonal black hole quasinormal modes (QNMs). More explicitly, the real part and imaginary part of the QNM frequencies correspond to the ring size and the detailed ring structure of the image, respectively. This correspondence may be violated when going beyond general relativity. In this talk, I’ll discuss the possibility of testing this mapping using real black hole observations. We propose a novel method to test the eikonal correspondence via the comparison of two sets of observables from a nonrotating black hole, one extracted from QNM spectra and the other from the lensed photon rings on the image plane. In particular, I’ll demonstrate that the photon ring observables robustly capture the information of the black hole spacetime itself regardless of the surrounding emission models. Therefore, the proposed test of eikonal correspondence can be validated in quite broad scenarios. |
2023/04/10 | Prof. Keiju Murata (Nihon University) |
Creating stars orbiting in AdS We propose a method to create a star orbiting in an asymptotically AdS spacetime using the AdS/CFT correspondence. We demonstrate that by applying an appropriate source in the quantum field theory defined on a 2-sphere, the localized star gradually appears in the dual asymptotically AdS geometry. Once the star is created, the angular position can be observed from the response function. The relationship between the parameters of the created star and those of the source is studied. We show that information regarding the bulk geometry can be extracted from the observation of stellar motion in the bulk geometry. |
2023/04/11 | Prof. Machael Good (Nazarbayev University) | Electron Acceleration Temperature
Thermal radiation from a moving point charge is found. The derivation is completely classical but has an immediate connection to quantum theory. |
2023/04/17 17:00-18:00 | Dr. Jason Kristiano (RESCEU, Tokyo University) |
Primordial black holes from single-field inflation?
The most widely studied formation mechanism of a primordial black hole (PBH) is collapse of large-amplitude perturbation on small scales generated in single-field inflation. In this talk, we will present the one-loop correction to the large-scale power spectrum in such a model. We find models producing appreciable amount of PBHs generically induce too large one-loop correction on large scale probed by cosmic microwave background radiation. We therefore conclude that PBH formation from single-field inflation is ruled out. |
2023/04/24 | Prof. Tetsuya Hashimoto (National Chung Hsing University) |
Towards uncovering the origin of fast radio bursts and future prospects in Taiwan
This talk will include an overview of recent observational research progress on fast radio bursts (FRBs) and future prospects of FRB science in Taiwan. FRBs are mysterious millisecond pulses in radio, most of which originate from distant galaxies. Despite more than 50 theoretical models of FRB progenitors, their origin is still unknown. Therefore, revealing the origin of FRBs is becoming central in astronomy and astrophysics. After presenting some basic knowledge of FRBs, I will summarize the current observational constraints on the FRB progenitors, including our approaches using the FRB number density, host galaxies, machine learning etc. I will also introduce a new FRB telescope project in Taiwan: Bustling Universe Radio Survey Telescope in Taiwan (BURSTT). Our paper predicts that BURSTT would detect more than two orders of magnitude more FRB-like events in the Milky Way compared with the other wide field-of-view FRB telescopes, STARE2 and GReX. BURSTT would also be useful to detect gravitationally lensed FRBs to constrain the primordial black hole scenario as the origin of the dark matter. |
2023/05/08 | Prof. I-Non Chiu (National Cheng Kung University) |
First Cosmology from galaxy clusters observed by eROSITA
We present the first cosmological constraints using the cluster abundance of a sample of eROSITA clusters, which were identified in the eROSITA Final Equatorial Depth Survey (eFEDS). In a joint selection on X-ray and optical observables, the sample contains 455 clusters within a redshift range of 0.1 < z < 1.2, of which 177 systems are covered by the public data from the Hyper Suprime-Cam (HSC) survey that enables a uniform weak-lensing mass calibration. In a framework of empirical modelling and blind analysis, we simultaneously model the cosmology, the X-ray selection, and the observable-to-mass-and-redshift relations with the observables including the X-ray count rate, the optical richness, and the weak-lensing mass. As a result, we deliver cosmological constraints that are in excellent agreement (at a level of < 1 sigma) with the results from the Planck mission, the galaxy-galaxy lensing and clustering analysis of the Dark Energy Survey, and the cluster abundance analysis of the SPT-SZ survey. With the empirical modelling, this work presents the first fully self-consistent cosmological constraints based on a synergy between wide-field X-ray and weak lensing surveys. |
2023/05/15 | Dr. Karan Fernandes (National Taiwan Normal University) |
Nonlinear memory effect from a subleading eikonal dressing The early inspiral phase in binary mergers can be derived using gravitationally interacting point particles considered within the eikonal approximation to scattering amplitudes. In particular, at third and higher post-Minkowski orders, the scattering process is inelastic and leads to an imaginary contribution to the eikonal phase. The corresponding eikonal operator describes a coherent state constructed from the leading Weinberg soft factor. These states have been recently used to derive gravitational wave observables in the finite and soft (vanishing frequency) limits of the emitted gravitational radiation. In this talk, I will discuss how next-to-eikonal corrections can be used to derive a generalized coherent state. We discuss key properties of this operator and use it to derive the nonlinear memory effect in the soft limit. The talk is based on an ongoing project with Prof. Feng-Li Lin (NTNU). |
2023/05/22 | Prof. Naritaka Oshita (YITP, Japan) |
Overtones, Greybody Factors and Thermal Ringdown of Black Holes
A gravitational wave from a binary black hole merger is an important probe to test gravity. Especially, the observation of ringdown may allow us to perform a robust test of gravity as it is a superposition of excited quasi-normal (QN) modes of a Kerr black hole. The excitation factor is an important quantity that quantifies the excitability of QN modes and is independent of the initial data of black hole mergers. Also, the reflectivity of the black hole geometry, quantified by the greybody factor, could be imprinted on the ringdown spectrum. The greybody factor is another no-hair quantity of a black hole and is useful to test gravity in strong gravity regimes.In this talk, I will discuss the modeling of ringdown with QN modes and with the greybody factors. I will show that the 5th overtone has the highest excitability of ringdown (i.e., has the highest value of the excitation factor) among the tones for l=m=2 mode with the spin parameters of ~ 0.7. Also, I will show that the greybody factor for the near extremal cases is very similar to the Fermi-Dirac distribution of the Hawking frequency. By virtue of the mysterious nature of spinning black holes, the ringdown spectrum of a small mass ratio merger involving a massive and rapidly spinning black hole can be modeled by the thermal Fermi-Dirac distribution characterized by the black hole surface gravity. |
2023/05/29 | Dr. Junsup Shim (ASIAA) |
Identifying Cosmic Voids as Massive Cluster Counterparts
We develop a method to identify cosmic voids from matter/galaxy density fields by adopting a physically-motivated void-cluster correspondence theory that voids are the counterpart of massive clusters. To prove the concept we use a pair of LCDM simulations, a reference and its initial density-inverted mirror simulation, and study the relation between the effective size of voids and the mass of corresponding clusters. We study the voids corresponding to the halos more massive than 10^{13}Msol/h and find a power-law scaling relation between the void size and the corresponding cluster mass. We also find that the density profile of the identified voids follows a universal functional form. Based on these findings, we propose a method to identify cluster-counterpart voids directly from the matter/galaxy density field without their mirror information. The completeness and reliability we achieve in recovering voids corresponding to clusters more massive than 3×10^{14}Msol/h are about 70-74 % for matter density fields and 60-67% for galaxy density fields. Our results demonstrate that we can apply this method to the galaxy redshift survey data to identify cosmic voids corresponding statistically to the galaxy clusters in a given mass range. |
2023/06/01 | Prof. Jun’ichi Yokoyama (RESCEU, Tokyo University) | Generation of neutrino dark matter, baryon asymmetry and radiation after quintessential inflation
We construct a model explaining dark matter, baryon asymmetry and reheating in quintessential inflation model. Three generations of right-handed neutrinos having hierarchical masses. Three generations of right handed neutrino explain dark matter and baryon asymmetry, while reheating is realized by spinodal instabilities of the Standard Model Higgs field induced by the non-minimal coupling to the scalar curvature, which can solve overproduction of gravitons and curvature perturbation created by the Higgs condensation. |
2023/06/19 | Prof. Yuki Inoue (National Central University) |
TBA
TBA |
TBD | Dr. Vipin Sudevan (LeCosPA, NTU) |
TBA
TBA |
Previous Talks
click the title to expand the abstract Dr. Shu-Yu Ho Asymmetric SIMP Dark Matter In this talk, I will show for the first time an asymmetric strongly interacting massive particles (SIMP) dark matter (DM) model, where a new vector-like fermion and a new complex scalar both having nonzero chemical potentials can be asymmetric DM particles. After the spontaneous breaking of a U(1)_D dark gauge symmetry, these two particles can have accidental Z_4 charges making them stable. By adding one more complex scalar as a mediator between the SIMP DM, the relic density of DM is determined by 3 to 2 and two-loop induced 2 to 2 annihilations in this model. On the other hand, the SIMP DM can maintain kinetic equilibrium with the thermal bath until the DM freeze-out temperature via the new gauge interaction. Interestingly, this model can have a bouncing effect on DM, whereby the DM number density rises after the chemical freeze-out of DM. With this effect, the prediction of the DM self-interacting cross section in this model can be consistent with astrophysical observations, and the ratio of the DM energy density to the baryonic matter energy density can be explained by primordial asymmetries. We also predict the DM-electron elastic scattering cross section that can be used to test this model in future projected experiments. Prof. Po-Feng Wu Extragalactic archeology: deciphering the evolution of galaxies with their fossil records One of the fundamental constraints on studying galaxy evolution is that we are not able to monitor individual galaxies throughout their lifetime to track the evolution. The stars in galaxies provide fossil records on the build-up processes of galaxies. I will demonstrate that with current observing facilities, we are able to track the evolution of individual galaxies in the distant Universe from their stellar populations. The archeological method can date the ages of galaxies, pinpoint where they are in their evolutionary process, and identify galaxies in the key phase of galaxy evolution for follow-up studies. The high precision allows quantitative comparison to cosmological hydro-dynamical simulations and validate current models of galaxy formation. With the coming survey projects and observing facilities, the archeological method will be able to track the evolution of galaxies in even earlier Universe, and with better statistics and precision. Dr. Jen-Tsung Hsiang Can the Universe get decohered all by itself? One of the common beliefs in cosmology is that cosmic expansion (or more dramatically inflation) is all we need to make the quantum to classical transition of the cosmological perturbations. We try to debunk this myth. Dr. Jakub Ripa Early results from GRBAlpha and VZLUSAT-2 CubeSats with gamma-ray burst detectors Gamma-ray bursts (GRBs) are the brightest explosions in the Universe. Some of them, the short GRBs, are important sources of gravitational waves originating in mergers of neutron stars or possibly also in mergers of neutron stars with black holes. I will present the detector performance and early science results from GRBAlpha, a 1U CubeSat mission, which is a technological pathfinder to a future constellation of nanosatellites monitoring and localazing GRBs. The localization can be achieved by measuring the time difference between the arrival of the signal at different satellites (synchronized by GPS). GRBAlpha was launched in March 2021 and has been operating already about a year on a 550 km altitude sun-synchronous orbit. The onboard gamma-ray burst detector consists of a 75×75×5mm CsI(Tl) scintillator, read out by a dual-channel multi-pixel (SiPM) photon counter (MPPC) setup. It is sensitive in the ~30-900 keV range. The main goal of GRBAlpha is the in-orbit demonstration of the detector concept, verification of the detector's lifetime, and measurement of the background level on low-Earth orbit, including polar regions and in the South Atlantic Anomaly. GRBAlpha has already detected five GRBs and was even able to detect two GRBs within 8 hours, proving that nanosatellites can be used for routine detection of gamma-ray transients. For one GRB, we were able to obtain a high resolution spectrum and compare it with measurements from the Swift satellite. We find that, due to the variable background, about half of the low-Earth polar orbit is suitable for gamma-ray burst detection. One year after launch, the detector performance is good and the degradation of the SiPM photon counters remains at an acceptable level. The same detector system, but double in size, was launched in January 2022 on VZLUSAT-2 (3U CubeSat). The GRB detectors perform as expected and I will present the early measurements from this mission as well. Our ultimate aim is to develop and launch a constellation of nanosatellites monitoring GRBs and these precursor missions help us to converge to this ambitious goal. Prof. Vitor Cardoso Niels Bohr Institute, Denmark) Testing GR with GWs One of the most remarkable possibilities of General Relativity concerns gravitational collapse to black holes, leaving behind a geometry with light rings, ergoregions and horizons. These peculiarities are responsible for uniqueness properties and energy extraction mechanisms that turn black holes into ideal laboratories of strong gravity, of particle physics (yes!) and of possible quantum-gravity effects. I will review the status of black holes, in light of gravitational-wave and electromagnetic observations in the last few years. Prof. Eiichiro Komatsu Hunting for Parity-violating Physics in Polarisation of the Cosmic Microwave Background Polarised light of the cosmic microwave background, the remnant light of the Big Bang, is sensitive to parity-violating physics. In this presentation we report on a measurement of parity violation from polarisation data of the European Space Agency (ESA)’s Planck satellite. The statistical significance of the measured signal is 2.4 sigma. If confirmed with higher statistical significance in future, it would have important implications for the elusive nature of dark matter and dark energy. We also report on a new measurement from the latest Planck public data release 4. Prof. Masahiro Hotta Prof. Daniel Baumann Dr. Che-Yu Chen Prof. Yuan-Hann Chang Prof. Feng-Li Lin Dr. Geoff Chih-Fan Chen Prof. Yen Chin Ong Prof. Hans Kristian Kamfjord Eriksen 2020 Spring: cancelled due to CoVID-19 pandemic (under construction) (under construction) (under construction) (under construction)
Date
Name (Affiliation)
Title and Abstract
2022/12/19
(Korea Institute for Advanced Study, Korea)
2022/12/12
(National Taiwan University, Taiwan)
2022/10/03
(National Central University, Taiwan)
2022/04/25
(Faculty of Science, Department of Theoretical Physics and Astrophysics, Masaryk University)
2022/03/14
(Center for Astrophysics and Gravitation, Instituto Superior Técnico, Portugal
2022/01/24 16:00
(Max-Planck-Institut für Astrophysik, Germany)
Date
Name (Affiliation)
Title and Abstract
2021/01/11
(Tohoku University, Japan)Generalized partners in quantum field theory
2021/03/08
(University of Amsterdam, Nederland)Cosmological Collider Physics
2021/06/07
(Institute of Physics, Academia Sinica, Taiwan)Black Hole Quasinormal Modes in General Relativity and Beyond
2021/06/21
(Institute of Physics, Academia Sinica and National Central University, Taiwan)Update of Dark Matter search with the AMS experiment and the TASEH project
2021/11/15
(National Taiwan Normal University, Taiwan)Weak Cosmic Censorship for Higher Derivative Gravity Theories
2021/11/29 10:00
(University of California, Los Angeles, United States)H0 measurement from time-delay cosmography
2021/12/06
(Yangzhou University, China)Musings on Springy Black Holes
2021/12/13 17:15
(Institute of Theoretical Astrophysics, University of Oslo, Norway)BeyondPlanck: Optimal end-to-end Bayesian analysis of Planck LFI
Date
Name (Affiliation)
Title and Abstract
2020/10/19
Dr. Shubham Maheshwari
(University of Groningen, Netherland) Stable, ghost-free solutions in UV non-local gravity
2020/11/30
Prof. Benjamin L'Huillier
(Yonsei University, Korea)Constraining Cosmology with the Large-Scale Structures
2020/12/07
Dr. Yen-Yung Chang
(Caltech/ NASA JPL) Quantum information science for next generation dark matter search
2020/12/21
Dr. Hsu-Wen Chiang
(LeCosPA, NTU) Modification to the Hawking temperature of a dynamical black hole by a flow-induced supertranslation, or could microsoft save the day?
2020/12/28
Dr. Hsu-Wen Chiang
(LeCosPA, NTU) Modification to the Hawking temperature of a dynamical black hole by a flow-induced supertranslation, or could microsoft save the day? Part 2
Date
Name (Affiliation)
Title and Abstract
2019/01/07
Dr. Akira Matsumura
(Nagoya University, Japan) Detectability of Bell-CHSH nonlocality by two spin detectors with optimal local filters
2019/01/21
Dr. Yen-Yung Chang
(Caltech)SuperCDMS SNOLAB and Future Low-Mass Dark Matter Searches
2019/02/26
Dr. Ippei Obata
(ICRR, Tokyo University, Japan) Axion Dark Matter Search with Optical Cavity Experiment
2019/03/07
Prof. Pisin Chen
(LeCosPA, NTU) Tabletop analog black holes to investigate the information loss paradox
2019/03/14
Dr. Aniket Agrawal
(ASIAA) Tensor Non-Gaussianity from Axion-Gauge-Fields Dynamics
2019/03/21
Dr. Shohei Aoyama
(ASIAA) Dust Hrains in Cosmological simulations
2019/03/28
Dr. Yen-Wei Liu
(NCU, Taiwan) Acausality in Transverse-Traceless Spin-2 Gravitational Waves
2019/04/11
Prof. Kai-Feng Chen
(NTU) Explore the universe with big Data at LHC
2019/04/25
Prof. Laurent Baulieu
(CNRS and UNESCO. LPTHE Sorbonne Université Paris) On the stochastic quantisation of quantum gravity, and its physical predictions for the early cosmology
2019/05/02
Prof. Rampei Kimura
(Waseda University, Japan) Are redshift-space distortions actually a probe of growth of structure?
2019/05/06
Prof. Yi Yang (NCKU, Taiwan)
The AMS experiment and it's latest results
2019/05/27
Prof. Daniel R. Terno (Macquarie University, Australia)
A self-consistent analysis of black hole horizons
2019/10/07
Prof. Mariam Bouhmadi-López (University of Basque Country, Spain)
Cosmological constraints of phantom dark energy models
2019/10/18 14:20
Prof. Kazunori Kohri (KEK/Sokendai/Kavli IPMU, Japan)
Axion-Like Particles and Recent Observations of the Cosmic Infrared Background Radiation and the GeV-TeV Gamma-rays
2019/10/21
Prof. Yu-Ting Huang (NTU)
Kerr black holes/ Taub-NUT geometry from on-shell S-matrix of higher spin particles/dyons
2019/12/16
Dr. Naoki Watamura (Shanghai University, China)
On the time development of Entanglement Entropy in massive scalar field theory