今後のセミナー
6月のセミナー
発表者
石川慶太朗
日程/場所
6月4日(水)13:30-@ES606
題名
Differentiable Cosmological Emulators for Halo Assembly Bias Studies
概要
Galaxies form in dark matter haloes. The spatial distribution of dark
matter haloes, and the distribution and the number of galaxies within a
dark matter halo, depend primarily on the halo mass. However, they are also
known to depend on halo properties other than mass, such as halo formation
history (Wechsler et al. 2006). This secondary dependence is called
assembly bias. In this work, to construct a halo statistics emulator that
also predicts the assembly bias, we focused on the concentration of haloes
as a representative secondary parameter, and measured the cross-correlation
function of various halo samples selected according to the mass and
concentration using Dark Quest II simulation data. We then constructed an
accurate power spectrum emulator for these statistics as inputs of halo
mass and concentration using a feed-forward neural network. By taking
partial derivatives of the emulator output with respect to halo mass, we
demonstrate that the network successfully captures how variations in
concentration modulate the power amplitude. In this talk, we will discuss
the implementation of automatic differentiation (AD) for both
emulator-based gradient evaluations and point‐estimation workflows,
highlighting the accuracy advantages of AD based on JAX or PyTorch over
simple finite‐difference approximations when compared to simulated galaxy
power spectra. Finally, we will outline prospects for integrating automatic‐
differentiation‐compatible Hamiltonian Monte Carlo (HMC) methods into
cosmological inference pipelines, exploiting the synergistic strengths of
AD and HMC for efficient, high‐dimensional parameter exploration.
5月のセミナー
発表者
嵯峨承平
日程/場所
5月28日(水)13:30-@ES606
題名
Relativistic effects on redshift-space distortions: towards
detection with Euclid
概要
The observed galaxy distribution via galaxy redshift surveys appears distorted due to redshift-space distortions (RSD). One dominant contribution to RSD comes from the Doppler effect induced by the peculiar velocity of galaxies. The other relativistic effects induce the asymmetric distortions, which contains qualitatively different cosmological information from the standard RSD analysis. I will present my recent contributions to Euclid on the asymmetric galaxy clustering.
発表者
市來淨與
日程/場所
5月14日(水)13:30-@ES606
題名
What does Planck tell us about inflation? - and beyond -
概要
The scattering of cosmic microwave background radiation (CMB) in galaxy clusters induces a polarization signal according to the quadrupole anisotropy of the photon distribution at the location of the cluster. This "remote quadrupole" derived from measurements of the induced polarization provides an opportunity to reconstruct primordial fluctuations on large scales. By comparing the local quadrupole of the CMB predicted by the primordial fluctuations reconstructed in this way with direct observations by CMB satellites, we discuss how the dark energy can be tested by CMB observations beyond the indefinite nature of the cosmic variance.
発表者
横山修一郎
日程/場所
5月7日(水)13:30-@ES606
題名
What does Planck tell us about inflation? - and beyond -
概要
Recent precise CMB measurements, such as Planck and BICEP/Keck, have given us a deeper understanding of cosmic inflation. In fact, conventional simple models (e.g., proposed in the early '80s) are in tension. In this talk, I would like to give a brief review of inflation, in particular, introduce how to classify the slow-roll inflationary models on the ns-r plane. I would also like to talk with you about what to expect in the future.
4月のセミナー
発表者
新居舜
日程/場所
4月30日(水)13:30-@ES606
概要
Gravitational lensing has been a remarkable observational tool for over the past century, providing insights into gravitational physics through its relativistic and geometric signatures. Meanwhile, the large-scale structure (LSS) of the Universe encapsulates the dynamic interplay between gravitational infall and cosmic expansion. Recent literature of cosmology has drawn the attention to utilise gravitational lensing of the cosmic microwave background (CMB lensing), sourced by LSS, to reveal the detailed evolutionary history of cosmic structures, especially during their early formation stages at high redshifts (z > 1).In this seminar, we will introduce the concept of "CMB-lensing tomography," a method that employs angular two-point correlation statistics measured across distinct redshift slices. We will outline a strategic programme aimed at achieving precise CMB-lensing tomography at high redshifts. To the last minutes, we will illustrate this methodology using recent observations of Lyman-break galaxies obtained with the Subaru Telescope.
発表者
市來淨與
日程/場所
4月16日(水)13:30-@ES606
題名
所信表明
概要
所信表明