セミナー

Ken'ichiro Nakazato, Tokyo University of Science

Exploring Hadron Physics in Black Hole Formations: a New Promising Target of Neutrino Astronomy

Room 345, 4 go-kan
Recently, we have performed several sets of core-collapse simulation of a non-rotating star with 40Msolar by a general relativistic neutrino-radiation-hydrodynamics code so as to compute quantitatively the dynamics up to the black hole formation as well as the neutrino luminosities and spectra. Employing different hadronic equations of state (EOS), we have demonstrated that the duration of neutrino emissions from this event is sensitive to the stiffness of EOS at supra-nuclear densities and, therefore, that the observation of neutrinos from such an event will provide us with valuable information on the properties of dense and hot hadronic matter. While this approach can not distinguish EOS’s with a similar stiffness: a soft nucleonic EOS and a hyperonic EOS, for example, we find that we can break this degeneracy by analyzing more in detail the time variation of neutrino numbers observed at a terrestrial detector. Performing the Kolmogolov-Smirnov test, which is free from the ambiguity of the distance to the progenitor, we show that the break-up of the degeneracy of hadronic EOS’s is indeed feasible for Galactic events. Ref. Nakazato et al. Physical Review D 81 (2010) 083009

Thomas Durt, Institut Fresnel, Marseille

Fundamental aspects of Time in Quantum Mechanics and Meson Phenomenology

Seminar room, Kenkyu honkan 3F
Mesons illustrate fundamental quantum properties such as the superposition principle (for instance in kaon oscillations), and their phenomenology also appeared very useful in the past for measuring CP-violation related effects. More recently, mesons were also useful for testing decoherence and entanglement related effects. The aim of our talk is to show that mesons could also be useful for revealing and/or studying fundamental aspects of Time in the quantum theory, such as the existence of a Time Operator (and also of the so-called Time Superoperator).

Naoki Yoshida, IPMU

初期宇宙での構造形成: はじめの3億年

Meeting room 1, Kenkyu honkan 1F
最近の大型望遠鏡を用いた観測により、赤方偏移8以上、つまりビッグバン後数億年の頃の銀河やガンマ線バーストが捉えられました。マイクロ波背景放射の偏光観測などから示唆される宇宙再電離の時期と合わせ、宇宙早期に星や銀河が数多く形成されたと判明しました。私たちの研究グループは、標準宇宙モデルに基づいた大規模数値シミュレーションを行い、初代星や初代ブラックホールの形成過程の研究を行ってきました。その成果を発表します。これからの銀河、ガンマ線バースト、中性水素の観測によりどのようなことが明らかになると期待されるのか展望を述べます。

Tomo Takahashi, Saga Universtity

Probing the early Universe with isocurvature fluctuations and non-Gaussianity

Meeting room 1, Kenkyu honkan 1F
I discuss primordial fluctuations and its non-Gaussianity in models with isocurvature perturbations. First I describe a general formalism which can give a systematic calculation of non-linear perturbations in models with isocurvature fluctuations. Then I discuss isocurvature fluctuations and non-Gaussianity in the mixed curvaton and inflaton model where the curvaton and the inflaton are both responsible for cosmic density fluctuations. The issue of differentiating CDM and baryon isocurvature modes using 21 cm fluctuations is also briefly discussed.
References: D. Langlois, T. Takahashi, arXiv:1012.4885 M. Kawasaki, T. Sekiguchi, T. Takahashi, arXiv:1104.5591

Makoto Nozawa, KEK

[理論宇宙物理グループセミナー] Black holes in an expanding universe

Meeting room 3, Kenkyu honkan 1F
Black holes in the isolated and stationary spacetimes have been intensively studied so far. They are completely characterized by conserved charges and exhausted by Kerr family. Black holes in non-isolated and dynamical background, on the other hand, have been less understood. In particular, the black-hole spacetime which is asymptotically FLRW universe is of considerable importance when discussing formation and evaporation of primordial black holes. In this talk, I will give a talk on the study of `black hole candidate’ recently obtained by Ohta et al, which is specified by a set of harmonic functions. We established that this geometry indeed describes a black hole in a decelerating FLRW universe satisfying appropriate physical conditions. This solution can be generalized to a universe with an arbitrary power law expansion and to any number of spacetime dimensions. Furthermore, we show that in five dimensions this solution is pseudo-supersymmetric in fake supergravity coupled to arbitrary number of scalars and gauge fields. We discuss physical properties and causal structures in detail.
参考文献:Kei-ichi Maeda & Masato Nozawa, Phys.Rev. D81 (2010) 124038; D83 (2011) 024018

Sergey Ketov, Tokyo Metropolitan University

Cosmological Inflation in Supergravity: The Meeting Point of Cosmology and High-Energy Physics

Meeting room 3, Kenkyu honkan 1F
We propose a simple (most economic, based on gravity and supersymmetry only) and viable realization of cosmological (chaotic) inflation of early Universe. It is based on a new theory of supergravity that we call F(R) supergravity. The F(R) supergravity can be understood as the N=1 locally supersymmetric extension of popular theories of f(R) gravity in four spacetime dimensions. Our proposal to inflation uses the supersymmetric extension of the (R+R^2) inflationary model of Starobinsky. The F(R) supergravity theory was invented by me just for that purpose. In my talk I review the Starobinsky inflation, the F(R) supergravity and their applications to the Early Universe cosmology. However, those are not the only features of the proposed approach. The universal reheating and particle production after inflation in the context of F(R) supergravity are briefly discussed too.

Masato Yamanaka, KEK

Big-bang nucleosynthesis with a long-lived CHAMP including helium-4 spallation process

Meeting room 1, Kenkyu honkan 1F
Long-lived charged massive particle (CHAMP) plays a role as catalyzer of exotic nuclear reactions in the Big-bang nucleosynthesis era. I discuss the primordial abundances of light elements involving the helium-4 spallation processes, the catalyzed fusion processes, and the internal conversion processes. Furthermore, I show the cosmologically favored parameter space in the minimal supersymmetric standard model with long-lived stau via solving the Lithium-7 problem

山口康宏, 阪大RCNP

[原子核・ハドロングループセミナー] Exotic baryons from a heavy meson and a nucleon --Negative parity states --II

Meeting room 1, Kenkyu honkan 1F
我々はヘビーフレーバーを含む中間子であるDbarメソンまたはBメソンと核子の系におけるエキゾチックな散乱状態の解析を行う。粒子間の相互作用として、ヘビークォーク対称性に基づいたパイオン、ベクターメソン交換相互作用を用いる。系を非相対論的に取扱い、シュレディンガー方程式を解くことによってS行列を求め、その結果として(I,JP)=(0,3/2-)状態に共鳴があることを予言した。この共鳴はヘビーベクターメソンと核子の系(Dbar*-NまたはB*-N)とのチャンネル結合によって引き起こされるFeshbach共鳴であることがわかった。

大古田俊介, 阪大RCNP

[原子核・ハドロングループセミナー] Exotic baryons from a heavy meson and a nucleon --Negative parity states -- I

Meeting room 1, Kenkyu honkan 1F
我々はヘビーメソンと核子(DbarN 及び BN)によって構成される、エキゾチックなフレーバー量子数を持つヘビーバリオンの研究を行なった。ヘビーメソンと核子間の相互作用はヘビークォーク対称性を反映した1ボソン交換力として記述する。安井氏と須藤氏による先行研究では、パイオンによる長距離力のみ考慮されていたが、今回我々は短距離力の効果も取り入れる。このとき束縛状態は先行結果と同様に(I,J^P) = (0,1/2^-)状態で得られた。また、我々はSU(4)フレーバー対称性に基づく、ヘビーメソン-核子系の束縛状態についての解析も行なった。この解析からクォーク質量が軽い領域と重い領域での物理の違いを議論する。

Akira Mizuta, KEK

[理論宇宙物理グループセミナー] Photospheric thermal radiation for GRB promot emission

Meeting room 3, Kenkyu honkan 1F
ガンマ線バーストの即時放射に関しての放射機構の一つとして光球面からの熱的放射モデルがあげられる。最近の理論的、数値シミュレーションから得られた結果に関して紹介する。
参考文献:
Lazzati et al. ApJ 732, 34 (2011)
Nagakura et al. ApJ 731, 80 (2011)
Pe’er ApJ 682, 463 (2008)

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