Dark Matter WGセミナー

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Dark Matter WGセミナー

Precise WIMP Dark Matter Abundance and Standard Model Thermodynamics

2021年6月24日16:30 - 17:30

白井 智 (東京大学 カブリ数物連携宇宙研究機構 特任助教)

We are now living in the era of precision cosmology. The relic abundance of dark matter (DM) is now observationally well-determined, and its error is smaller than O(1)%. This means that the same or much higher precision is required when we make theoretical predictions. Weakly Interacting Massive Particle (WIMP) has long been the leading candidate for DM because of its beautiful mechanism to predict the observed relic abundance. WIMP is in the same thermal bath as the Standard Model particles in the beginning. At a certain point when the temperature of the Universe is smaller than the DM mass, it decouples to fix its number density. The yield of the DM is determined by its annihilation cross-section to the Standard Model sector. It seems that there is no ambiguity in the calculation of this process at first: the cross-section is purely theoretical and all the remainings are described in the Standard Model physics. However, the source of the uncertainty does remain in the Standard Model sector. The dilution of the number density of DM particle depends on the expansion rate of the Universe, which is determined by the Standard Model particles. The effective degree of freedom (d.o.f) of the relativistic species controls this factor. We have to deal with the non-equilibrium dynamics to precisely describe the time-evolution of the d.o.f, in which we need numerical approaches. In this talk, he introduced his work to update these calculations. By implementing the latest findings in the non-equilibrium dynamics in i) the neutrino decoupling, ii) the QCD phase transition, iii) the electroweak phase transition, and iv) the perturbative calculations, they found that the final d.o.f is smaller than the previous estimate in more than 1%. This is larger than the level of precision in observations. It is also important that the uncertainty is quantified by them. Another good news is that he makes the calculated d.o.f with its error publically available. With these updates, we now correctly know the points to probe DM!

会場: via Zoom

イベント公式言語: 英語

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Dark Matter WGセミナー

Emulation for lensing and clustering observables of the cosmological large-scale structure

2021年5月12日10:00 - 11:00

西道 啓博 (京都大学 基礎物理学研究所)

Recent developments in observational technologies open exciting opportunities to map out the detailed structure of the universe. Remarkably, the unique combination of imaging and spectroscopic galaxy surveys is now becoming well established as a standard analysis methodology for precision cosmology. While the former can access directly the underlying clustering of mass dominated by dark matter projected on the sky through the weak gravitational lensing effect, the latter provides us with the three dimensional map of the structure traced by galaxies. One can mitigate the galaxy-bias uncertainty, which has been the major obstacle for cosmology based on galaxy surveys, by jointly analyzing these effects. We still need, however, a robust and versatile theoretical and statistical framework to interpret these datasets. The Dark Quest project, launched in 2015, is a structure formation simulation campaign precisely for this purpose. We have developed an emulation tool, dubbed as Dark Emulator, based on a large database of simulated dark matter halos in virtual universes with different cosmologies efficiently sampled in six-dimensional parameter space. Dark Emulator employs a simple machine-learning architecture with Gaussian process at its core. It makes predictions of various statistical measures of dark matter halos, both lensing and clustering observables, for a given cosmological parameters in a few seconds on laptop computers without running a new simulation. This AI-aided tool, once supplemented with recipes for the halo-galaxy connection, is therefore applicable to real-data analyses as the theoretical template, which typically requires hundreds of thousands of function calls in the course of parameter inference. I will introduce this project and report the status of its application to Subaru HSC data. We are looking forward to seeing you online.

会場: via Zoom

イベント公式言語: 英語

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Dark Matter WGセミナー

Mapping the Milky Way by VLBI Astrometry

2021年2月16日13:30 - 15:00

坂井 伸行 (Korea Astronomy and Space Science Institute (KASI), Republic of Korea)

Astrometry is the only way to obtain 6D (position-velocity) phase space information for astronomical objects. The unique capability allows us to examine the past, present, and future of the Milky Way. Firstly, I will introduce history and basics of astrometry. Secondly, I will overview astrometric projects in the world. Thirdly, I will highlight recent astrometric results about the Galactic structure. Lastly, I will introduce astrometric research in Korea as well as future astrometric projects and sciences in 2020s and 30s.

会場: via Zoom

イベント公式言語: 英語

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Dark Matter WGセミナー

Directional dark matter search and the technologies

2020年12月3日10:00 - 11:00

中 竜大 (東邦大学 理学部物理学科 講師 / 名古屋大学 素粒子宇宙起源研究所 (KMI) 特任助教)

For identification of the dark matter, various methodologies are required. Especially, the direct detection is one of the most important goals to directly understand itself. Now, there are various technologies for direct detection, but almost all detectors have no direction sensitivity. We can obtain essential information such as dependence of motion between the earth and the dark matter, velocity distribution and background from direction information, therefore that becomes a very important methodology to identify the dark matter for future as long as we consider "particle dark matter". In this seminar, I report about the potential of direction sensitive dark matter search and current experimental effort.

会場: via Zoom

イベント公式言語: 英語

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Dark Matter WGセミナー

Composite Dark matter and gravitational waves

2020年10月20日10:00 - 11:00

エンリコ・リナルディ (数理創造プログラム 客員研究員 / AI Researcher/Engineer, Arithmer Inc.)

With non-perturbative lattice calculations we investigate the finite-temperature confinement transition of a composite dark matter model. We focus on the regime in which this early-universe transition is first order and would generate a stochastic background of gravitational waves. Future searches for stochastic gravitational waves will provide a new way to discover or constrain composite dark matter, in addition to direct-detection and collider experiments. As a first step to enabling this phenomenology, we determine how heavy the dark fermions need to be in order to produce a first-order stealth dark matter confinement transition.

会場: via Zoom

イベント公式言語: 英語

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Dark Matter WGセミナー

The Uchuu Simulations: Data Release 1 and Dark Matter Halo Concentrations

2020年10月1日14:00 - 15:00

石山 智明 (千葉大学統合情報センター 准教授)

We introduce the Uchuu suite of large high-resolution cosmological N-body simulations. The largest simulation, named Uchuu, consists of 2.1 trillion dark matter particles in a box of 2.0 Gpc/h. The highest resolution simulation, called Shin-Uchuu, consists of 262 billion particles in a box of 140 Mpc/h. Combining these simulations we can follow the evolution of dark matter haloes (and subhaloes) spanning from dwarf galaxies to massive galaxy cluster hosts. We present basic statistics, dark matter power spectra and halo (subhalo) mass function, to demonstrate the huge dynamic range and superb statistics of the Uchuu simulations. From the analysis of the evolution of the power spectra we conclude that our simulations are accurate enough from the Baryon Acoustic Oscillations up to very small scales. We also provide parameters of a mass-concentration model, which describes the evolution of halo concentrations, that reproduces our simulation data within 5% error for haloes with masses spanning nearly eight orders of magnitude at redshift 0<z<14. We make publicly available various N -body products, as part of Uchuu Data Release 1, on the Skies & Universes site. We also plan to release gravitational lensing maps, mock galaxy, X-ray cluster and active galactic nuclei catalogues in the near future.

会場: via Zoom

イベント公式言語: 英語

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Dark Matter WGセミナー

DMWG special seminar : “The result of the XENON1T experiment and its implications”

2020年7月22日15:30 - 17:00

山下 雅樹 (名古屋大学 宇宙地球環境研究所 宇宙線研究部 特任准教授)

会場: via Zoom

イベント公式言語: 日本語

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Dark Matter WGセミナー

Search for ultralight dark matter with laser interferometric gravitational wave detectors

2020年7月13日10:00 - 11:00

道村 唯太 (東京大学 大学院理学系研究科 物理学専攻 助教)

会場: via Zoom

イベント公式言語: 英語

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Dark Matter WGセミナー

Dark Matter Heating vs. Rotochemical Heating in Old Neutron Stars

2020年6月22日16:00 - 17:00

濱口 幸一 (東京大学 大学院理学系研究科 准教授)

*Detailed information about the seminar refer to the email

会場: via Zoom

イベント公式言語: 英語

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Dark Matter WGセミナー

The effect of the early kinetic decoupling in a fermionic dark matter model

2020年6月12日10:00 - 11:00

阿部 智広 (名古屋大学 素粒子宇宙起源研究所 (KMI) 基礎理論研究部門 素粒⼦論部 特任助教)

*Detailed information about the seminar refer to the email

会場: via Zoom

イベント公式言語: 英語

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Dark Matter WGセミナー

Characterizing the continuous gravitational-wave signal from boson clouds around Galactic isolated black holes

2020年4月27日16:00 - 17:00

Dr. Sylvia Zhu (Postdoctoral Researcher, Deutsches Elektronen-Synchrotron DESY, Germany)

Bosons such as axions or axion-like particles can form enormous clouds around black holes via the superradiance instability. As the bosons annihilate in the presence of the black hole, they produce a long-lived, slowly-evolving continuous gravitational-wave signal that is potentially detectable using the current generation of gravitational-wave interferometers.A non-detection can disfavor the existence of axions in certain mass ranges, although this is highly dependent on the Galactic black hole population. In this talk, I will discuss the expected annihilation signal from the population of isolated stellar-mass black holes in the Galaxy, and the prospects for detecting the signal using standard searches for continuous gravitational waves.

会場: via Zoom

イベント公式言語: 英語

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Dark Matter WGセミナー

Mining for Dark Matter substructure: Learning from lenses without a likelihood

2020年2月17日14:00 - 15:30

Dr. Johann Brehmer (Postdoctoral Researcher New York University)

Dr. Brehmer gives us a talk about a method to deduce DM small structures. Please join us!

会場: 研究本館 424-426号室

イベント公式言語: 英語

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Dark Matter WGセミナー

Weak lensing cosmology by Subaru HSC survey

2019年12月12日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 特任准教授)

Place: IPMU seminar room C

会場: Kavli IPMU 棟

イベント公式言語: 英語

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Dark Matter WGセミナー

Haloes at the low-mass end in wino dark matter

2019年10月21日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)

会場: セミナー室 (160号室)

イベント公式言語: 英語

セミナー

Dark Matter WGセミナー

A new lamppost in dark matter searches: Composite Dark Matter

2019年10月1日10:00 - 18:00

エンリコ・リナルディ (数理創造プログラム 研究パートタイマー)

会場: 研究本館 424-426号室

イベント公式言語: 英語