Cセミナー 2022 | セミナー | 名古屋大学 宇宙論研究室(C研)

Cセミナー 2023

English

今後のセミナー

2月のセミナー

発表者
三倉祐輔

日程/場所
2月7日(水)13:30-@ES606

題名
Spin projector formalism and Metric-Affine theories of Gravity

概要
Metric-Affine theories of Gravity (MAGs) are a vast class of extensions of General Relativity, where the metric and connection are treated as independent and dynamical variables. Without any restrictions, however, kinetic term for all the components of the fields cannot be positive, and such theories generically have pathologies such as ghosts or tachyons. In this talk, I review the spin projector formalism as a technique to decompose fields into irreducible representations, construct a ``simple'’ MAG where simple means that only one massive particle propagates on top of the massless graviton, and show in which parameter region the theory is free of the pathologies.

発表者
山下由莉

日程/場所
2月7日(水)10:30-@ES606

題名
Damping of primordial magnetic fields in the early universe

概要
In the early universe, one thinks there are primordial magnetic field and it is commonly called PMF. After PMF was generated, PMF damped by friction of fluid. We have researched this damping regime so far. We have done the relativistic linear and non-linear magneto-hydro-dynamics simulations, and are investigating the results.

発表者
三輪拓真

日程/場所
2月7日(水)10:30-@ES606

題名
Progress Report

概要
Recent CMB polarization observations have pointed to the possibility of parity symmetry violation. The current promising hypothesis is that cosmic birefringence, but I will consider alternatives to this hypothesis. I will consider that parity is violated by primordial gravity waves, estimate what is the upper limit of parity violation of primordial gravity waves allowed by the current observations in my study.

1月のセミナー

発表者
Mariana Vargas-Magaña and Sébastien Fromenteau (メキシコ国立自治大学)

日程/場所
1月31日(水)13:30-@ES606

題名
A roadmap for extracting cosmological information from Galaxy Spectroscopic Surveys.

概要
We will present the roadmap for extracting cosmological information from spectroscopic surveys. We will begin by reviewing the methodology used in stage III experiments over the past two decades. Subsequently, we will discuss the evolution of the methodology during the current decade, with a specific focus on the preparation of the stage IV experiment: the Dark Energy Spectroscopic Instrument (DESI). Particularly, I will highlight the ongoing efforts toward projects based on the first year of data from DESI.

発表者
古澤和也

日程/場所
1月31日(水)10:30-@ES606

題名
Exploring GW Signals under the Foreground from SMBHs in Future PTA Measurement

概要
Recently, NANOGrav and the other PTA teams have reported the evidence of gravitational wave background has been detected.Many cosmologists consider the main candidate is SMBHs. Also, there are other signals in the PTA frequency band coming from the cosmological sources, inflation, cosmic string, PBH and so on. These are related to the new physics and expected to be observed in the future PTA measurement. However, GW signals from SMBHs are worked as the foreground and we have to remove those foreground to probe new physics. In this presentation, I revisit F-statistic in the context of PTA measurement and finally implicate this process in 3-simple cases at one frequency.

発表者
吉﨑允泰

日程/場所
1月31日(水)10:30-@ES606

題名
Progress report(controversial presentation)

概要
The distribution of emission line galaxies(ELGs) is different from that of luminous red galaxies(LRGs), so the void size functions that are defined by each type of galaxy might be different. That's why I will check those void size functions. In my study, I will use a toolkit, void identification and examination(VIDE). Then I will introduce VIDE.

発表者
多田祐一郎

日程/場所
1月24日(水)13:30-@ES606

題名
Cancellation of quantum corrections on the soft cosmological perturbations

概要
Recently, the quantum correction on large-scale (CMB-scale) perturbations from much smaller-scale perturbations has attracted attention, particularly in the context of the primordial black hole. Several authors claim that even superhorizon cosmological perturbations time-evolve due to quantum corrections counterintuitively. Our recent work suggested that the quantum correction on the soft curvature perturbation is cancelled, understood as a kind of cosmological soft theorem, while the cancellation of tensor corrections has not been proven. In the talk, I will review these works as well as several basics of QFT, loop correction, non-equilibrium formulation, etc.

発表者
Yin Li (Peng Cheng Laboratory)

日程/場所
1月19日(金)10:30-@ES606

題名
Forward Model the Universe in the Era of Deep Learning

概要
Rapid advances in deep learning have brought not only myriad powerful neural network models, but also breakthroughs that benefit established scientific research. In particular, automatic differentiation (AD) tools and computational accelerators like GPUs have facilitated forward modeling of the Universe with differentiable simulations. Using backpropagation, current differentiable cosmological simulations are limited by memory, thus are subject to a trade-off between time and space/mass resolution, usually sacrificing both. We present a new approach free of such constraints, using the adjoint method and reverse time integration. Being both memory and computation efficient, it enables larger and more accurate forward modeling at the field level, and will improve inference of fundamental physics from cosmological data in both precision and efficiency. Its differentiability opens up the possibility for data driven workflows, incorporating trainable neural networks in differentiable physical models. We implement it in an open-source particle-mesh (PM) N-body library pmwd (particle-mesh with derivatives). Based on the powerful AD system JAX, pmwd is fully differentiable, and is highly performant on GPUs. Improvements are ongoing and planned to make it a unified framework to model and infer from cosmological data at the field level.

発表者
長谷川賢二

日程/場所
1月17日(水)13:30-@ES606

題名
What ionized the Universe ~recent observations and theories~

概要
I review recent observational results on cosmic reionization. In particular, I focus on ionizing sources, e.g., galaxies and AGNs. Important points here are the abundance of these objects and the escape fraction of ionizing photons. I introduce some theoretical predictions and compare them to the latest observations. Finally I show some my ideas to confirm what ionized the Universe.

12月のセミナー

発表者
門田健司(Hangzhou Institute for Advanced Study at University of Chinese Academy of Sciences:HIAS-UCAS)

日程/場所
12月20日(水)13:30-@ES635

題名
Multi-messenger probes on dark matter surrounding black holes

概要
The environment around the black hole can provide us a promising playground to study the dark matter properties because of the large dark matter density from accretion. I will explore the multi-messenger probes on the dark matter in the vicinity of black holes. More concretely, I will discuss (1) the gravitational wave signals from a black hole binary whose dynamics is affected by the dark matter (2) the multi-wavelength signals covering the radio, CMB and gamma rays which can arise from the dark matter annihilation.

発表者
太田敦久(重慶大学)

日程/場所
12月6日(水)10:30-@ES606

題名
One-loop thermal radiation exchange in gravitational wave power spectrum

概要
I will discuss the intriguing interplay of radiation fields and gravitational waves within a radiation-dominated universe. We explore the quantum aspects of their interaction, questioning whether elementary particles consisting of background radiation interact with primordial gravitational waves in quantum field theory. We analyze quantum corrections to the gravitational wave power spectrum, focusing on thermal radiation loop corrections, revealing the surprising dominance of the 1-loop correction over the tree-level spectrum. The loop expansion is reorganized in terms of the inflationary Hubble-to-Planck mass ratio. We found the leading contributions are up to two-loop order, and thus, the loop expansion may be convergent. Our findings highlight the crucial role of quantum effects between radiation and gravitational waves.

11月のセミナー

発表者
水口由莉乃

日程/場所
11月22日(水)13:30-@ES606

題名
Stochastic lattice simulation

概要
Cosmic inflation is known to solve the problems of Big Bang theory and generate the fluctuations as the seeds of the current cosmological structures. Its existence is strongly suggested by the Planck observation of the cosmic microwave background (CMB). Though the CMB observation implies small fluctuations on large scales, large fluctuations may be realized on a smaller scale and the primordial black holes (PBHs) may be made by their gravitational collapse. PBHs have gotten much attention lately as candidates for dark matter and may be searched by LISA in future probes. However, the detailed analysis of the PBH formation from inflation requires a lot of assumptions, particularly in the statistics of the primordial curvature perturbations. In this talk, I introduce a numerical lattice simulation of inflation in the stochastic approach (STOLAS: STOchastic LAttice Simulation). It enables us to know the true statistics of the curvature perturbation and predict the accurate statistic of PBH in each inflation model. I show examples in some models. I also describe the importance sampling technique to sample efficiently the large perturbation related to PBH formation.

発表者
松井悠真

日程/場所
11月15日(水)13:30-@ES606

題名
Generation and time evolution of primordial gravitational wave in cyclic universe

概要
Inflation theory solves many of problems of the big bang theory. But we cannot discuss a moment when expansion starts, called initial singularity in inflation theory. To solve this, the bouncing theory has considered as an alternative theory. In this theory, we can avoid the initial singularity to consider a contracting universe before expansion. In particular, the cyclic model, which repeats expansion contraction phases forever, has an advantage that universe is flat and non-singular. The cosmic gravitational-wave(GW) background is expected to search for signs of these theories. In the inflation, primordial GW spectrum is nearly scale invariant. In this study, I calculate primordial GW spectrum in the cyclic model by time dependence of scale factor in each phase, and discuss more general situation about dominant component.

発表者
北島歓大(Ta研)

日程/場所
11月15日(水)10:30-@ES606

題名
An origin of narrow extended structure in the interstellar medium: an interstellar contrail created by a fast-moving massive object

概要
We investigate the thermal condensation caused by a massive object that passes through the interstellar medium with high velocity, and propose a mechanism for creating a filamentary gaseous object, or interstellar contrail. Our main result shows that a long interstellar contrail can form with a certain parameter; a compact object more massive than 10^4 M ☉ can make a filament whose length is larger than 100 pc. Observation of interstellar contrails may provide information on the number, masses, and velocities of fast-moving massive objects, and can be a new method for probing invisible gravitating sources such as intermediate-mass black holes.

発表者
成瀬元希

日程/場所
11月8日(水)13:30-@ES606

題名
The Contribution of Subhalos to the 21cm Forest in the Pre-reionization Epoch

概要
The 21 cm forest is a promising tool to trace the structure of the universe before the reionization epoch. In our previous study (Kadota, GN et al. 2023), we found that the 21 cm optical depth is enhanced about 10 times larger at most due to the existence of subhalos in a host halo if such subhalos survive and keep a low temperature. However, it is still unclear whether subhalos suffering from the ram pressure and/or tidal stripping actually survive or not. In this work, we investigated the survivability of the subhalos by performing hydrodynamics simulations. As a result, we found that subhalos can survive until several dynamical times though a large part of shabuhalos is dynamically stiripped away. Then we calculated the enhancement of the 21 cm optical depth caused by survived subhalos and their remnants and found that the enhancement is about one figure less than the previous result.

発表者
石川慶太朗

日程/場所
11月1日(水)10:30-@ES606

題名
Robustness of BAO measurement with Photometric Redshift Uncertainty

概要
There are two main types of galaxy observation methods: spectroscopic and photometric. In contrast to spectroscopic observations, photometric observations have the advantage of being able to reach faint galaxies. However, photometric observations have significant uncertainty in estimating the redshift of galaxies. In this study, we consider baryon acoustic oscillations (BAO) measured by photometric redshift and also discuss the allowed level of systematics due to the one's uncertainties that should be achieved in future observations. For this purpose, we model the photo-z effect by incorporating the photo-z distribution assuming a Gaussian in the 3D two-point correlation function and verify the effect using mock simulations in redshift-space. As a result, we found the following things. In the case the magnitude of the photo-z error is known, the 3D two-point correlation function can constrain the BAO peak location up to the standard deviation σ = 0.01(1+z) of photo-z error. In the case the magnitude of the photo-z error is unknown, a photo-z 1% template can be used (although the statistical error will be larger), and the BAO peak location will not be biased. In addition, we check several variations: redshift, stellar mass limit, cross-correlation between spec-z and photo-z, LSST-like covariance, and so on. We will summarize these tests for robust BAO measurement and discuss the required level of photometric observation accuracy.

10月のセミナー

発表者
谷田幸貴

日程/場所
10月25日(水)13:30-@ES606

題名
"Probing General Relativity: Combining Weak Lensing and Galaxy Clustering from HSC-Y3 and BOSS"

概要
Einstein’s theory of general relativity has been successful in describing various phenomena caused by gravity, such as black holes and gravitational lensing. It has been confirmed that general relativity is consistent with the experiments in the Solar System, whereas it has not been exclusively examined on cosmological scales. In particular, the discovery of cosmic acceleration has recently motivated the investigation of a number of proposals for modified gravity models. Such alternative models can produce the late-time acceleration without the cosmological constant involved in the standard Λ CDM model. In our study, we aim to test the modified gravity models by applying Redshift-space distortion(RSD) as well as the three two-point correlation functions (3×2pt) of the large-scale structure. 3x2pt consists of cosmic shear, galaxy-galaxy lensing, and galaxy-galaxy clustering. We use measurements from the third-year HSC (HSC-Y3) weak lensing sample and SDSS spectroscopic galaxy catalog. a. In this analysis, instead of using specific gravity theories, we phenomenologically modify general relativity. Specifically, we employ a theory model that alters the gravitational effects experienced by non-relativistic matter and relativistic matter (μ-Σ parameterization). In this presentation, we discuss the behavior of the constraints on the cosmological parameters including μ-Σ by analyzing each mock data. And we compare the result with the previous result for the real data analysis from third-year DES(DES-Y3).

発表者
松本明訓(東京大学)

日程/場所
10月25日(水)10:30-@ES606

題名
Primordial Helium Abundance Probed by Subaru Spectroscopy:A Test of the Cosmological Model

概要
The primordial He abundance is best determined by observations of metal-poor galaxies, while there are only a few known extremely metal-poor (< 0.1Z⊙) galaxies (EMPGs) having reliable He/H measurements. We present deep Subaru NIR spectroscopy for 10 EMPGs and determination of the He/H values with NIR HeI10830A line and optical emission lines. Adding pre-existing galaxies with reliable He/H estimates to our sample, we obtain Yp = 0.23790+/-0.0034, which is slightly (∼ 1σ) smaller than the previous values. With the Yp constrain, the existing primordial deuterium Dp constraints, and a prior of baryon-to-photon ratio η, we obtain the degeneracy parameter of electron-neutrino ξe = 0.05+/-0.03, the effective number of neutrino species Neff = 3.11+/-0.33, and η×10^10 = 6.08+/-0.06. Our constraints may suggest a existence lepton asymmetry and allow for a high value of Neff up to Neff ~ 3.4 within the 1σ level, which could mitigate the Hubble tension.

発表者
尹聖煥

日程/場所
10月18日(水)13:30-@ES606

題名
S8 tension and cluster cosmology

概要
two most interesting tensions in modern cosmology, S8 tension and H0 tension, are getting worse as we measure S8 and H0 more precisely. at the seminar, I willl give a small talk on 1. S8 tension, 2. cluster cosmology's role , 3. future survey projects.

発表者
村上広椰

日程/場所
10月11日(水)13:30-@ES606

題名
Estimation of fσ8 using machine learning with 3D image data of the large-scale structure

概要
8 represents the time evolution of the cosmic large-scale structure and can be used to test the gravitational theory. fσ8 can be estimated using the power spectrum of the matter distribution observed by cosmological surveys such as galaxy survey. However, to do this, we need assumptions of the phenomenological model of the power spectrum. In this study, we focus on convolutional neural network (CNN) which is a machine learning image analysis technique as a method to estimate fσ8 without the assumption of this model. CNN can estimate fσ8 directly from 3D images of the matter distribution. In this talk, the results of the estimation of fσ8 for the public N-body simulation data (QUIJOTE simulation) are shown and discussed.

発表者
林慎太郎

日程/場所
10月4日(水)13:30-@ES606

題名
A memorie of my summer vacation(夏休みの自由研究)

概要
Self-interacting dark matter(SIDM) or DM-other species interactions are proposed by some motivations. Recently, I focus on a galactic DM halo and its density profile. In this context, "core-cusp problem" is pointed and this problem is considered as the motivations of introducing SIDM or other interactions. There is a method called "gravothermal fluid method" to calculate the DM halo density profile and its time-evolution. I talk about the gravothermal fluid method and its calculation technique.

7月のセミナー

発表者
新居舜

日程/場所
7月19日(水)13:30-@ES635

題名
An elaborate time lapse of CMB lensing

概要
A measured CMB lensing signal is able to be decomposed into the minuter redshift shells, provided that the angular cross power between a lensing mass and a CMB lensing map is better localised in redshifts at higher SNR. We aim to create a time lapse of CMB lensing meeting such requirements. Collectively utilising cross-correlation statistics between a given lensing mass and reference spectroscopic samples i.e. SDSS, the lensing mass distribution is quantitatively reconstructed in multiple redshift bins with its wide sky coverage. We find that the combination of 3GHz radio map (composed of reconstructed submaps) and Planck PR4 \kappa map (MV) provides a time lapse of the CMB lensing with deserved quality.

発表者
中島光一朗

日程/場所
7月12日(水)13:30-@ES035

題名
RSD analysis with Lyman alpha forest

概要
The Lyman alpha forest (LAF), a series of HI absorption lines in the quasar spectra, can be a strong tool for cosmology at redshifts (z>2) that are generally hard to access with other probes. We present a measurement of the LAF anisotropic power spectrum from the hydrodynamic simulations with the GADGET3-OSAKA code and analyze the full shape to measure the growth rate of the structure through redshift space distortions. Understanding the power spectrum on small scales is essential to further improve the accuracy of cosmological analysis. We measured the 3D power spectrum for 5 simulation models which include different astrophysical feedback. We tested the joint analysis of the 2 × 2 correlation with different simulation models and gained more stringent constraints on $f\sigma_8$ for $k_\mathrm{max} = 3.0 h/\mathrm{Mpc}$ than that of $k_\mathrm{max} = 1.0 h/\mathrm{Mpc}$, but it’s biased. In this talk, I will discuss the analysis method to constrain $f\sigma_8$ correctly.

発表者
乾玲冬

日程/場所
7月5日(水)13:30-@ES635

題名
Constraints on Non-Gaussian primordial density perturbation from the LIGO-Virgo-KAGRA third observing run

概要
The cosmological stochastic gravitational waves background (SGWB) has attracted much attention as a method to explore the universe before the Cosmic Microwave Background (CMB), and mechanisms of generating such SGWB in the early universe before the CMB have been actively investigated. One of them is the second-order induced gravitational waves which are induced by large amplitude primordial density fluctuations. The amplitude of the primordial density fluctuation can be constrained by observing the SGWB. Recent work has evaluated the amplitude of the primordial density fluctuation from the latest data obtained by the LIGO-VIRGO-KAGRA collaboration. However, this analysis was based on the assumption that the primordial density fluctuations follow a Gaussian distribution. On the other hand, recent theoretical studies have shown that inflationary models that generate large amplitude primordial density fluctuations tend to have statistical properties that deviate from a Gaussian distribution (non-Gaussianity). The presence or absence of non-Gaussianity affects the amplitude and shape of the second-order induced gravitational waves spectrum. Therefore, the constraint would be changed if one takes the non-Gaussianity into account in the analysis. In this work, we consider the non-Gaussianity of the primordial density fluctuation and constraint the amplitude and non-Gaussianity of the primordial density fluctuation from the third observing run data of the LIGO-VIRGO-KAGRA collaboration.

6月のセミナー

発表者
彭淇(ポンチイ)

日程/場所
6月28日(水)13:30-@ES635

題名
From Precessions to Gravitational Waves

概要
This paper presents a simple exploration of celestial mechanics, specifically focusing on Mercury’s orbit and its implications in the context of general relativity.

発表者
三輪拓真

日程/場所
6月28日(水)13:30-@ES635

題名
Possibility of parameter restrictions from observations by LiteBIRD and CMB-S4

概要
This presentation is a review of [1]. Inflation theory can solve the initial condition problems of the standard Big Bang theory. The existence of inflation is supported by CMB observations. After inflation, the universe undergoes a reheating epoch. The reheating epoch is the process of producing Standard Model particles from the energy of the scalar field that causes inflation. However, the mechanism of reheating is not well known, such as the temperature at the end of the reheating epoch. The purpose of this work is to consider the possibility of restrictions the temperature at the end of r eheating in the model of interest based on the next generation CMB observations such as Lite BIRD and CMB-S4. In this study, we focus on a model called mutated hilltop inflation, which is one of the slow-roll inflation models in which inflation is drawn by a single scalar field. First, the relationship between model parameters and CMB observables is investigated. Then, we created pseudo data assuming the previously mentioned next-generation observations and estimated the model parameters using a Markov chain Monte Carlo method. We found that Lite BIRD and CMB-S4 can restrict the reheating temperature and so on. This is expected to provide new insights into the Standard Model. [1]M.Drewes, L.Ming, I.Oldengott, LiteBIRD and CMB-S4 Sensitivities to Reheating in Plateau Models of Inflation, 2303.13503v1,79,2023

発表者
吉﨑允泰

日程/場所
6月28日(水)13:30-@ES635

題名
Observational upper bound on the abundance of negative-mass compact objects and Ellis wormholes from SQLS

概要
In general relativity, gravity is interpreted as the curvature of spacetime. Within this curved spacetime, there may exist singularities. To avoid these singularities and smoothly connect spacetime, two candidates are considered: wormholes and negative mass. Wormholes are hypothetical structures that appear as spherically symmetric solutions in Einstein's equations and can be thought of as tunnels connecting distant points in spacetime. The wormhole we will consider in this study is the Ellis wormhole (EWH), which is a wormhole with zero mass. On the other hand, negative mass is a hypothetical concept of matter with mass of the opposite sign to normal matter, producing repulsive gravity. Negative mass has been discussed since the 19th century, but there is no evidence supporting its existence. In this study, we assume the existence of EWHs and compact objects with negative mass and estimate their abundance through gravitational lensing observations in the Sloan Digital Sky Survey Quasar Lens Search (SQLS). The lensing effect of EWHs and negative mass compact objects creates multiple images of quasars. By estimating the upper limits of their abundance based on the size of EWHs, the mass of negative mass compact objects, and the probability of experiencing lensing effects, we found that the upper limit on the abundance of negative mass compact objects is smaller than that of galaxies and galaxy clusters. Additionally, the upper limit on the abundance of EWHs is found to be smaller than that of stars. By improving the precision of observations and discovering more quasars affected by lensing effects, we can expect stronger constraints on EWHs and negative mass compact objects. This presentation is a review based on reference [2]. References: [1]H.G. Ellis, J. Math. Phys. 14 (1973) 104 [2]R. Takahashi, H. Asada, Astrophys.J.Lett. 768 (2013) L16

発表者
山下由莉

日程/場所
6月21日(水)13:30-@ES635

題名
Damping of primordial magnetic fields on the early universe

概要
Magnetic fields exist everywhere in the universe. For example, it is known that magnetic fields of about 10^-6 G exist in galaxies and galaxy clusters, and magnetic fields of about 10^-15-10^-20 G exist in low-density intergalactic regions called voids. Several theories have been proposed to explain the origin of the magnetic fields that exist widely in the universe, and one of them is to find the origin in the magnetic fields generated in the early universe before the clear up of the Universe(hereinafter referred to as "primordial magnetic field"). The generation of the primordial magnetic field may be due to inflation or density fluctuations, but after its generation, the magnetic field lines move with the cosmic plasma fluid and decay with B∝a^(-2). However, scenarios explaining this damping have conventionally neglected the damping effects of various waves generated by the plasma fluid in a magnetic field. In a plasma fluid in a magnetic field, various longitudinal and transverse waves called magneto-hydro-dynamics modes (MHD modes) are generated. Therefore, the damping of the primordial magnetic field can be explained with higher accuracy by considering the damping of these waves. In this presentation, we discuss the mechanism of the decay of MHD modes with wavelengths below the mean free path of both particles during the decoupling of neutrinos and photons from the cosmic plasma fluid in the early universe (before redshift z~1100). As a means of analysis, the dispersion relation was derived by Fourier transforming the linearized relativistic MHD equation, and the propagation velocity and decay rate of MHD modes were calculated. The results suggest that the damping may be very large compared to the previously predicted B∝a^(-2). In this presentation, we will discuss the calculation results of the propagation velocity and damping rate of MHD modes.

発表者
古澤和也

日程/場所
6月21日(水)13:30-@ES635

題名
Constraint on $M$BH-$M$halo Relation at $z=6$ from Detectability of Gravitational Waves in DM Halo-SMBH Coevolution Model

概要
To reveal the mystery of the formation and evolution of a supermassive black hole (SMBH), the estimate of SMBH at high redshift from observational results is meaningful. And gravitational wave (GW) observations are expected to estimate the SMBH growth and formation at high redshift in the most populated region that we cannot approach using the Quasi-Stellar Object (QSO) datasets. To discuss the possibility, in this study, we construct a dark matter halo-SMBH coevolution model and calculate the mass evolution of SMBH only via merger at $0\leq z \leq6$. Then we calculate the GW radiations generated from the coalescence of SMBH binaries and consider their detectability by pulsar timing arrays (PTAs) and Laser Interferometer Space Antenna (LISA). In this C-seminar, I will explain how we describe DM halo-SMBH coevolution and calculate GWs from SMBH binaries. Also, I'll discuss in detail how the detectability of GWs constrains the formation and evolution of SMBH in this model.

発表者
山本貴宏

日程/場所
6月14日(水)13:30-@ES635

題名
CWs from boson clouds around nearest BHs

概要
I will talk about my recent thought on CWs from boson clouds around the nearest BHs. After talking about the motivation, I will give a brief review of the data analysis method for CWs from binary systems. If possible, I want to discuss the possibility of the detection.

5月のセミナー

発表者
Maxime Paillassa

日程/場所
5月24日(水)13:30-@ES635

題名
Source detection and deblending: from classical algorithms to machine learning.

概要
In this C-seminar, I will present source detection techniques for wide-field imaging surveys. I will first review how astronomical images form and the classical approaches for source detection. Then, we will see how those methods can be naturally extended with machine learning techniques. Finally, after reviewing some applications of machine learning for source detection and deblending, I will present our work about blend identification for HSC images.

発表者
Santiago Jaraba (IFT UAM-CSIC)

日程/場所
5月17日(水)13:30-@ES635

題名
Stochastic gravitational wave background constraints from Gaia DR3 astrometry

概要
astrometric surveys can be used to constrain the stochastic gravitational wave background (SGWB) at very low frequencies. The European Space Agency’s (ESA) Gaia mission, launched in 2013 and with a recent data release (DR3) in 2022, shows great potential for this purpose. In this talk, I will review the formalism that relates astrometry to gravitational waves and talk about a recent work in which we used Gaia DR3 to set constraints on the SGWB amplitude. I will also comment on previous works which computed similar constraints and discuss the potential of future Gaia data releases to impose tighter bounds.

発表者
三輪拓真

日程/場所
5月10日(水)13:30-@ES635

題名
Self introduction

概要
Self introduction

発表者
吉﨑允泰

日程/場所
5月10日(水)13:30-@ES635

題名
Self introduction

概要
Self introduction

4月のセミナー

発表者
Xiaolin LIU

日程/場所
4月26日(水)13:30-@ES635

題名
Study on the gravitational waves from elliptical two-body system with spin-precessing effects based on effective-one-body formalism

概要
Binary systems are the most common sources of gravitational waves in the universe. In the detection and data processing of gravitational waves, modeling of gravitational wave sources is crucial. Binary black hole systems have very complex dynamical properties. For a long time, mainstream gravitational wave models only supported the computation of non-memory effect gravitational waves from circular orbit binary black hole systems. With the improvement in sensitivity of future gravitational wave detectors and the launch of space detector projects, there will be an increasing demand for gravitational wave templates with a larger parameter range and higher accuracy. In this work, we computed the orbital dynamics and decomposed waveform that simultaneously support eccentricity and spin precession in the effective-one-body formalism with second-order post-Newtonian accuracy. We then tested this new model and compared its performance in circular orbit situations, and discussed the parameter estimation bias that would result from ignoring this effect in future O4 observations through simulated parameter estimation.

発表者
古澤和也

日程/場所
4月19日(水)13:30-@ES635

題名
Self Introduction

概要
Self Introduction

発表者
山下由莉

日程/場所
4月19日(水)13:30-@ES635

題名
Self Introduction

概要
Self Introduction

発表者
市來淨與

日程/場所
4月19日(水)13:30-@ES635

題名
所信表明

概要
所信表明

▲ Top