Dark Matter WGセミナー
Mining for Dark Matter substructure: Learning from lenses without a likelihood
2020年2月17日(月) 14:00 - 15:30
Dr. Johann Brehmer (Postdoctoral Researcher, New York University, USA)
Dr. Brehmer gives us a talk about a method to deduce DM small structures. Please join us! The subtle imprint of dark matter substructure on extended arcs in strong lensing systems contains a wealth of information about the small-scale distribution of dark matter and, consequently, about the underlying particle physics. However, teasing out this effect is challenging since the likelihood function for realistic simulations of population-level parameters is intractable. Structurally similar problems appear in many other scientific fields ranging from particle physics to neuroscience to epidemiology, which has prompted the development of powerful simulation-based inference techniques based on machine learning. We give a broad overview over these methods, and then apply them to the problem of substructure inference in galaxy-galaxy strong lenses. In this proof-of-principle application to simulated data, we show that these methods can provide an efficient and principled way to simultaneously analyze an ensemble of strong lenses, and can be used to mine the large sample of lensing images deliverable by near-future surveys for signatures of dark matter substructure.
会場: 研究本館 424-426号室
Weak lensing cosmology by Subaru HSC survey
2019年12月12日(木) 10:30 - 12:00
日影 千秋 (東京大学 カブリ数物連携宇宙研究機構 (Kavli IPMU) 特任准教授)
Place: IPMU seminar room C
会場: Kavli IPMU 棟
Haloes at the low-mass end in wino dark matter
2019年10月21日(月) 13:00 - 15:00
関口 豊和 (東京大学 ビッグバン宇宙国際センター (RESCEU))
Neutral wino is a natural candidate of dark matter in split-supersymmetry. Indirect detection is a promising probe of wino dark matter, with its annihilation enhanced non-perturvatively (i.e. Sommerfeld enhancement). In theoretical prediction, halo formation at the low-mass end is a key ingredient. For this purpose, we investigate kinetic decoupling of wino dark matter and consequent dark matter density perturbations. We show that inelastic processes involving charged wino, which are relevant for kinetic equilibrium at late times, shuts off abruptly. This results in boosted acoustic peaks in density power spectrum at horizon scales around the kinetic decoupling. Based on an analytic modeling of subhalo evolution, we estimate the subhalo mass function of (dwarf) galaxy-sized haloes and effects on the annihilation boost factor. We also discuss application of our analysis to SU(2)_L multiplet minimal dark matter.
会場: セミナー室 (160号室)
A new lamppost in dark matter searches: Composite Dark Matter
2019年10月1日(火) 10:00 - 18:00
リナルディ エンリコ (数理創造プログラム 研究パートタイマー)
In the search for the nature of dark matter many particle physics models are proposed. Models originating from a new strongly coupled dark sector, similar to QCD and Nuclear Physics, give rise to Composite Dark Matter particles. These models are hard to study, but they have a very interesting phenomenology with clear signals that are distinct from the usual WIMP candidates. To make robust predictions in Composite Dark Matter models one often needs to investigate non-perturbative effects due to the strong dynamics. In my talk I will explain how Lattice Field Theory methods and numerical simulations are well suited for this task and contribute to a solid uncertainty quantification. A variety of detection signals can be studied with lattice simulations, from dark matter self interactions to interactions with regular matter and even signals of dark phase transitions generating primordial gravitational waves.
会場: 研究本館 424-426号室