Zdzislaw Burda, Jagellonian University
Spectrum of the Product of Independent Random Gaussian Matrices
Meeting room 1, Kenkyu honkan 1F
We show that the eigenvalue density of a product $¥X=¥X_1 ¥X_2 ¥cdots ¥X_M$ of $M$ independent $N¥times N$ Gaussian random matrices in the limit $N¥rightarrow ¥infty$ is rotationally symmetric in the complex plane and is given by a simple expression $¥rho(z,¥bar{z}) = ¥frac{1}{M¥pi} ¥sigma^{-¥frac{2}{M}} |z|^{-2+¥frac{2}{M}}$ for $|z|¥le ¥sigma$, and is zero for $|z|> ¥sigma$. The parameter $¥sigma$ corresponds to the radius of the circular support and is related to the amplitude of the Gaussian fluctuations. This form of the eigenvalue density is highly universal. It is identical for products of Gaussian Hermitian, non-Hermitian, real or complex random matrices. It does not change even if the matrices in the product are taken from different Gaussian ensembles. We present a self-contained derivation of this result using a planar diagrammatic technique. Additionally, we conjecture that this distribution also holds for any matrices whose elements are independent, centered random variables with a finite variance or even more generally for matrices which fulfill Pastur-Lindeberg’s condition. We provide a numerical evidence supporting this conjecture.
Tomohiro Takahashi, Kyoto University
Lovelock Black Holeの安定性解析
Meeting room 2, Kenkyu honkan 1F
時空が高次元の場合、加速器でblack holeが生成される可能性が指摘されている。そのため、高次元のblack hole解や解の持つ性質が調べられている。それらの研究のほとんどはEinstein理論に基づいて行われている。本発表においては、重力理論の高次元への“自然な”拡張であるLovelock理論に基づき、解の性質の一つである線形安定性について議論する。まず、Lovelock理論とその理論の厳密解である球対称静的なblack hole解について述べる。その後に、その解の周りの線形摂動が従う方程式を紹介し、摂動が時間的に増大する条件について述べる。最後に、その判定条件を用いて十分massの小さいblack holeは不安定であることを述べる。
Shunsaku Horiuchi, Ohio State Univeristy
The possible origins of heavy nuclei ultra-high energy cosmic rays
Meeting room 1, Kenkyu honkan 1F
A century after their discovery, the astrophysical origins of cosmic rays remain intensely studied. In particular, cosmic rays of the highest energies cannot feasibly be confined in our Galaxy, and is thought to originate from extra-galactic sources. While many source candidates have been proposed, disentangling them is generally complicated by the fact that charged cosmic rays bend in the magnetic universe. However, new observational results on the composition may provide new insights. It has recently been reported that the composition of cosmic rays at the highest energies become increasingly heavy (Fe-like). I will review the composition claims and discuss implications for source candidates. In particular, I will discuss the potential that explosive nucleosynthesis in gamma-ray burst jets can provide a uniquely heavy-nuclei-dominated cosmic ray source.
Carsten Rott, Ohio State University
Closing in on Dark Matter with Neutrino Telescopes
Meeting room 3, Kenkyu honkan 1F
Unraveling the mysterious nature of dark matter is one of the most exciting scientific goals of this decade. While there is overwhelming evidence for its existence, its properties remain literally in the dark. New approaches in the search for dark matter might finally shed light on its properties and distribution in our Galaxy. Neutrino telescopes offer exciting opportunities for the detection of neutrinos produced as part of dark matter self-annihilations or decays. Using data collected during the construction period of the giga-ton sized IceCube detector, I will present a new analysis that searched for a neutrino anisotropy from the Galactic dark matter halo. This search is complementary to searches performed with gamma-ray telescopes and capable to test dark matter models motivated by the observed lepton excess by PAMELA. I will further discuss results from searches looking at the Galactic Center and dwarf spheroidal galaxies, which are expected to be dark matter dominated. Besides these searches that can constrain the dark matter self-annihilation cross section, I will discuss prospect and methods in the search for dark matter captured by the Sun. These Solar WIMP searches offer complementary ways to direct detection experiments to probe the dark matter nucleon scattering cross sections. The talk will also cover a first look at results obtained with the low-energy extension of IceCube, Deep Core, which is taking data since June 2010. Future upgrades that offers exciting opportunities for dark matter searches down to candidate masses in the GeV range, will be discussed as part of an outlook.
Antonio Enea Romano, National Taiwan Univeristy
Corrections to the apparent value of the cosmological constant due to local inhomogeneities
Seminar room, Kenkyu honkan 3F
Supernovae observations strongly support the presence of a cosmological constant, but its value, which we will call apparent, is normally determined assuming that the Universe can be accurately described by a homogeneous model. Even in the presence of a cosmological constant we cannot exclude nevertheless the presence of a small local inhomogeneity which could affect the apparent value of the cosmological constant. Neglecting the presence of the inhomogeneity can in fact introduce a systematic misinterpretation of cosmological data, leading to the distinction between an apparent and true value of the cosmological constant. Modeling the local inhomogeneity with a $¥Lambda LTB$ solution we compute the relation between the apparent and true value of the cosmological constant. Contrary to previous attempts to fit data using large void models our approach is quite general. The correction to the apparent value of the cosmological constant is in fact present for local inhomogeneity of any size, and should always be taken appropriately into account both theoretically and observationally.
Danny Marfatia, Kansas Univeristy
Isospin-Violating Dark Matter
Meeting room 1, Kenkyu honkan 1F
Searches for dark matter scattering off nuclei are typically compared assuming that the dark matter’s spin-independent couplings are identical for protons and neutrons. This assumption is neither without consequence nor well motivated. We consider isospin-violating dark matter with one extra parameter, the ratio of neutron to proton couplings. For a single choice of this ratio, the DAMA and CoGeNT signals are consistent with each other and with XENON constraints, and unambiguously predict a signal at CRESST.
Tsubasa Ichikawa, Kinki U
系統的なエラーに耐性のあるユニタリ操作の設計
Seminar room, Kenkyu honkan 3F
量子情報処理では、系の正確な操作が不可欠である。一方、実際の実験環境ではノイズやエラーの影響により、実際に行った操作が所望の操作からずれてしまうことが一般的である。従って、所望の操作を実装するにあたっては、上手い工夫をして「ずれ」が少なくなるようにすることが望ましい。 本講演では、上述のずれの少ない量子操作をどのように設計すればよいかについて紹介する。近年の進展を概説した後に、二準位系に対する最近の我々のグループの取り組みについて述べる。
Kousuke Sumiyoshi, Numazu College of Technology / KEK
Progress of EOS tables for core-collapse supernovae & its applications to explosion dynamics and neutrino signals
Seminar room, Kenkyu honkan 3F
I would like to talk on the recent development of the EOS tables for core-collapse supernovae and their influence on the dynamics and the signal of neutrino bursts. I would like to describe the role of the equation of state in the neutrino-radiation hydrodynamics for supernova explosion. Some topics I try to cover include the mixture of light elements in supernova cores and the neutrino emission from the black hole formation.
Masahiro Ibe, ICRR
Recent Model Buildings of Gauge Mediation
Meeting room 1, Kenkyu honkan 1F
The models with gauge mediation are quite attractive to realize phenomenologically viable supersymmetric standard model. From the cosmological point of view, the models with the very light gravitino with a mass in the eV range is also motivated since it does not cause any cosmological problems. The models with such a light gravitino mass is, however, known to difficult to be realized. In this talk, I explain our recent models which realize such a very light gravitino mass. I also discuss a separate topic in gauge mediation, the lightest Higgs boson mass in gauge mediation. In the MSSM with gauge mediation, the Higgs boson mass is usually predicted at the lower edge of the experimental bound. We show however, the Higgs boson mass can be much enhanced even if we do not extend the models.
Naoki Yamamoto, Keio University
量子フィードバック制御理論の基礎
Seminar room, Kenkyu honkan 3F
