セミナー 2012年

Satoshi Ohya, Harish-Chandra Research Institute

Path integral junctions

Seminar room, Kenkyu honkan 3F
I propose a new path integral formulation of one-particle quantum mechanics on equilateral quantum wire junctions. I find that scale-invariant junctions realized at fixed points of boundary renormalization group flow are in one-to-one correspondence with matrix-valued weight factors on the path integral side. I show that these weight factors are generally given by multi-dimensional unitary representations of the infinite dihedral group.

Satyanarayan Mukhopadhyay

Effective couplings of the Higgs boson in the light of recent LHC and Tevatron data

Meeting Room 1, Honkan Building 1F
How much can the effective couplings of the Higgs boson deviate from their standard model predictions? We perform a multi-parameter global analysis of the recent LHC and Tevatron data and try to address this question in a very general and model independent setting

Yukinao Akamatsu, KMI, Nagoya

In-medium QCD forces at high temperature

Meeting Room 1, Kenkyu Honkan 1F
The physics of heavy quarkonium suppression in quark-gluon plasma has been discussed in the context of screened QCD force in medium for a long time. In this talk, I will show that another type of force, namely the drag force and its fluctuation, also plays an important role in the real-time dynamics of heavy quarkonium in the medium. In order to make this statement concrete, I will employ the closed-time path formalism of non-equilibrium quantum field theory and perform leading order perturbative analysis. This will tell us how these different types of forces determine the dynamics of quantum states of heavy quark systems in the medium.

Zoltan Fodor, University of Wuppertal, Eotvos University

QCD thermodynamics on the lattice

Meeting Room 1, Kenkyu Honkan 1F
Recent result of lattice QCD thermodynamics are summarized. The nature of the transition between low and high temperatures is determined. Its characteristic temperature (T_c) is calculated. The equation of state is given. Selected results at nonvanishing chemical potentials are presented. Special emphasis is put on the physical point (physical quark masses and extrapolation to the continuum limit).

Makoto Sasaki, The University of Tokyo, ICRR

Ashra NTA

Meeting Room 1, Kenkyu Honkan 1F
The Earth-skimming tau neutrino technique detects extensive air showers produced by tau lepton decays in the atmosphere, which enjoys a large target mass. The tau leptons, produced by VHE tau neutrinos that interact with the Earth matter they traverse, emerge out of a mountain or the ground facing the detector. This method has detection sensitivity in the PeV-EeV region, and can be used to search for neutrinos originating from hadron acceleration in astronomical objects. Additional advantages are perfect shielding of cosmic ray secondaries, precision arrival direction determination, and negligible background from atmospheric neutrinos. The All-Sky High Resolution Air-shower detector (Ashra) projects were independently developed to detect tau neutrinos with the Earth-skimming method. Aiming for realizing very high energy “multi-particle astronomy”, the Ashra detector has been developed since 2002 with 1 arcmin pixel resolution and all-sky coverage. The principal demonstration phase, Ashra-1, has been running at the Mauna Loa site at 3300m above sea level on Hawaii Island since 2008. Ashra-1 succeeded in the first search for PeV-EeV tau neutrinos originating from a GRB as the commissioning run, and has achieved best instantaneous sensitivity since January 2012 after trigger upgrade.
Based on these achievements, we start to form a new collaboration for concrete design and planning for the next generation large Neutrino Telescope Array (NTA). The conceptual layout for the NTA observatory considers three site stations for a 25km-grid triangle watching the total air mass surrounded by the mountains of Mauna Loa, Mauna Kea, and Hualalai. A single site station at the center of the triangle has full-sky coverage. This configuration allows tremendous sensitivity (equivalent to > 100 giga ton water) with Cherenkov-fluorescence stereoscopic observation for PeV-EeV neutrinos in essentially background-free conditions. With the demonstrated fine imaging of Earth-skimming tau showers, we aim for clear discovery and identification of astronomical tau neutrino sources. I would introduce our detector performance, potential capabilities of physics probes into main physics of Very-high energy neutrino search and some of various bread and butter physics like determination of cosmic ray composition with direct cherenkov method and so on.

Tadashi Takayanagi (YITP, Kyoto U / Kavli IPMU, U Tokyo)

Holographic Entanglement Entropy and Emergent Spacetime

Meeting Room 1, Kenkyu Honkan 1F
After a brief review of (holographic) entanglement entropy, we will first introduce our latest result on a thermodynamical property of entanglement entropy for excited states. Later, we study a conjectured connection between the AdS/CFT and a real-space quantum renormalization group scheme, the multi-scale entanglement renormalization ansatz (MERA). By making a close contact with the holographic formula of the entanglement entropy, we propose a general definition of the metric in the MERA in the extra holographic direction, which is formulated purely in terms of quantum field theoretical data.

堀内渉, 北海道大学大学院理学研究院

[Particle and Nuclear Physics Seminar at J-PARC] 第一原理計算による4Heの電弱励起の研究

Tokai 1st building 115, KEK Tokai campus
本講演では4Heの電弱応答について、4体計算による解析結果を紹介する。低励起の光吸収断面積は基底状態から非束縛な励起状態への電気双極子遷移による。あらわに相関した特殊な波動関数を用いることにより、核力によって強く相関する4核子系を一つの枠組みで記述した。得られた光吸収断面積は実験値を広いエネルギー領域でよく再現し、反応閾値近傍の光吸収断面積では3He+n, 3H+pクラスター配位が重要となること、光吸収断面積の総和に対応するThomas-Reiche-Kuhn和則へはπ中間子交換力、とりわけテンソル力が主要な寄与を成すことを示した。また、電気双極子演算子に類似のスピン双極子演算子による遷移はニュートリノー原子核反応の際に重要となる。得られたスピン双極子強度関数は実験のスペクトル、共鳴パラメータをよく再現し、和則においてテンソル力の効果を示唆する結果が得られた。

杉本茂樹, カブリ数物連携宇宙機構

超対称性のないゲージ理論における S-duality とカラーの閉じ込め

Meeting Room 1, Kenkyu Honkan 1F
Type IIB 弦理論において orientifold と D-brane を組み合わせることで超対称性のないゲージ理論を実現し、弦理論の S-duality を用いてその性質を探ることを試みる。考える理論(電気的理論)のゲージ群は USp(2n) で、それと双対な理論(磁気的理論)はタキオン場を含む SO(2n) 理論となる。特に n=1 の場合、電気的理論は低エネルギーでSU(2) Yang-Mills 理論となり、その双対な記述が得られることになる。電気的理論はカラーの閉じ込めやフェルミオン対の凝縮による対称性の自発的破れが起こると考えられている理論で、これらの性質を S-duality と弦理論の知識を使って理解する試みを紹介したい。ただし、S-duality を用いても完全に理論が解ける訳ではないので、議論の一部に speculation が入ることをお許し願いたい。

Seiju Ohashi, Kyoto Univ

Gravitational Collapse in Lovelock Gravity

Meeting Room 345, 4 Go-kan
The final state of gravitational collapse is one of the main subjects in gravitational physics in higher dimensional spacetime as well as in four dimension. Especially it is important to clarify whether naked singularities appear or not during the collapse. Naked singularity implies the breakdown of predictability of the physical theory, so it is conjectured that no such singularities form under physically reasonable condition. In this context, we study the gravitational collapse and its final state in Lovelock gravity, which is higher dimensional generalization of Einstein gravity. Then we show that naked singularity will form depending on the initial data of the collapse. We also discuss the nature of naked singularity.

Junko Yamagata-Sekihara, Osaka Electro-Communication Univ. & KEK

Effective nuclear density probed by meson-nucleus systems

Meeting Room 1, Kenkyu Honkan 1F
Meson-Nuclear systems are very important and useful objects to extract the meson properties at finite density, which may have the close connections to the symmetry breaking pattern of QCD and its partial restoration in the nucleus. However, the effective densities probed by pionic atoms are known to be around ~ 0.6 rho_0 for almost every pionic state and the change of the chiral order parameter < qbar q > in nuclei is only determined at this specific density. Thus, we are very interested in the density probed by various meson-nuclear systems to know the potentiality of the systems for the studies of the meson properties and the aspects of QCD symmetries at various nuclear densities beyond the linear density approximation.
We consider kaonic systems systematically as a first step. The nuclear density probed by kaonic atoms were studied before and we found that the probed density depended on the states significantly. Thus, the kaonic systems could be more suited to observe various densities than pionic systems. And we performe more systematic studies including both bound and low energy scattering states of K and Kbar mesons.

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