Coming Seminars
Seminars in June
Speaker
Keitaro Ishikawa
Date/Place
13:30-, 4(Wed), June. @ES606
Title
Differentiable Cosmological Emulators for Halo Assembly Bias Studies
Abstract
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 haloesas 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 exploratio
Seminars in May
Speaker
Shohei Saga
Date/Place
13:30-, 28(Wed), May. @ES606
Title
Relativistic effects on redshift-space distortions: towards
detection with Euclid
Abstract
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.
Speaker
Kiyotomo Ichiki
Date/Place
13:30-, 14(Wed), May. @ES606
Title
What does Planck tell us about inflation? - and beyond -
Abstract
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.
Speaker
Shuichiro Yokoyama
Date/Place
13:30-, 7(Wed), May. @ES606
Title
What does Planck tell us about inflation? - and beyond -
Abstract
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.
Seminars in April
Speaker
Shun Arai
Date/Place
13:30-, 30(Wed), Apr. @ES606
Abstract
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.
Speaker
Akira Ishikawa
Date/Place
13:30-, 23(Wed), Apr. @ES606
Title
Self Introduction
Abstract
Self Introduction
Speaker
Huyuko Tanaka
Date/Place
13:30-, 23(Wed), Apr. @ES606
Title
Self Introduction
Abstract
Self Introduction
Speaker
Ryota Himeno
Date/Place
13:30-, 23(Wed), Apr. @ES606
Title
Self Introduction
Abstract
Self Introduction
Speaker
Taisuke Makino
Date/Place
13:30-, 16(Wed), Apr. @ES606
Title
Self Introduction
Abstract
Self Introduction
Speaker
Nobuhusa Kobayashi
Date/Place
13:30-, 16(Wed), Apr. @ES606
Title
Empirical Galaxy Formation Modeling
Abstract
Self introduction
Speaker
Kiyotomo Ichiki
Date/Place
13:30-, 16(Wed), Apr. @ES606
Title
Policy speech
Abstract
Policy speech