セミナー

川合光, 京都大学

砂漠と自然性 -場の理論をこえて-

Meeting room 1, Kenkyu honkan 1F
LHCの結果によると、超対称性は低エネルギーには見当たらず、しかもHiggs粒子は基本粒子と考えてもよい。そうすると次に問題となるのは、どれくらい大きいエネルギースケールまで標準模型が有効かということであるが、Higgs質量が決定されたため精度のよい解析ができるようになった。まだ、トップクォーク質量の誤差からくるあいまいさはあるが、弱電磁スケールからプランクスケールの間には なにもない砂漠である可能性がでてきた。これは、標準模型の物理とプランクスケールの物理が直接つながっているということであり、それらの統合をはかることが素粒子物理学の次の目標であることを意味している。そのための重要な手掛かりとなるのが宇宙項およびスカラー質量の自然性の問題である。従来、自然性は超対称性との関連で議論されることが多かったが、上記の実験結果はより広い視野から議論しなおす必要性を示している。自然性問題を再考するため、従来の結果を損なうことなく、場の理論を少しはみ出すいくつかの試みについて議論する。

Takahisa Igata, Osaka City U

Stable Bound Orbits of Massless Particles in Myers-Perry Black Holes

Meeting room 1, 3 go-kan 1F
No stable circular orbits of a particle exist in higher-dimensional Schwarzschild black holes because of the dependence of gravitational potential on spacetime dimensions. We find, however, that stable bound orbits of a particle in Myers-Perry black holes appear as black hole spin increases. In this talk we discuss the appearance of stable bound orbits of a massless particle in six-dimensional Myers-Perry black hole and some application.

Ryosuke Sato, KEK

Effective gravitational interactions of dark matter axions

Meeting Room 1, Kenkyu Honkan 1F
We investigate the structure of gravitational self interactions of coherently oscillating axions in the general relativistic framework. A generic action for a massive scalar field in the Friedmann-Robertson-Walker background is first introduced based on the effective field theory approach to cosmological perturbations. Using the obtained setup, we evaluate the effective gravitational interaction of the massive scalar field, i.e. scalar quartic interactions mediated by metric perturbations. Applying the results to the system of dark matter axions, we estimate the self interaction rate of them, and discuss its implications for axion Bose-Einstein condensate dark matter scenario. Leading contributions for gravitational interactions of axions are given by the process mediated by the dynamical graviton field, which is essentially the Newtonian potential induced by fluctuations of the background fluids. We find that it leads to the same order of magnitude for the interaction rate of dark matter axions in the condensed regime, compared with the result of previous studies using the Newtonian approximation.

Christian Weiss, Jefferson Lab.

Sea quark transverse momentum and parton short-range correlations in QCD

Seminar room, Kenkyu honkan 3F
The dynamical breaking of chiral symmetry in QCD is caused by nonperturbative interactions with a range rho ~ 0.3 fm, much smaller than the typical hadronic size. Recent theoretical work has studied the effects of these interactions on the nucleon’s partonic structure at a low scale: (a) Sea quarks have intrinsic transverse momenta up to the scale 1/rho, much larger than those of valence quarks. (b) Sea quarks exhibit short-range correlations of size rho with characteristic quantum numbers (sigma, pi), analogous to NN correlations in nuclei. The effects are demonstrated in a model of low-energy dynamics based on the large-N_c limit of QCD. They can be tested experimentally and have numerous implications for hadron production in semi-inclusive deep-inelastic scattering (HERMES, COMPASS, JLab 12 GeV), dilepton production in hadron-hadron scattering (FNAL, COMPASS, RHIC W, J-PARC), and multiparton processes in high-energy pp collisions (LHC).

Hidehiko Shimada 島田英彦, Okayama Institute for Quantum Physics

[Strings and Fields Group Seminar] Membranes in the bulk from monopole operators in ABJM theory: Large angular momentum in M-theoretic AdS4/CFT3

Meeting Room 3, Main Bldg. 1F
In the talk, I will consider states with large angular momentum to facilitate the study of the M-theory regime of the AdS4/CFT3 correspondence
(duality between M-theory on $AdS_4 ¥times S^7/Z_k$ and ABJM theory with gauge group $U(N)¥times U(N)$ and level $k$, where $k$ is finite and $N$ is large).
In particular I will discuss near-BPS operators in ABJM theory which correspond to states of membranes with large angular momenta on AdS.
The talk will be based on my work with S.
Kovacs(DIAS) and Y. Sato
(Wits University).

Yasuro Funaki, RIKEN

A new theoretical approach to triple-alpha thermonuclear reaction rate

Meeting room 1, Kenkyu honkan 1F
Recently triple-alpha thermonuclear reaction rate is discussed using some theoretical approaches at low temperature region (below 1 GK), where experimental date is not available. One of them, the calculation via CDCC (Continuum Discretized Coupled Channel) method, in particular, predicts much larger reaction rate by 10^{25} at 0.01 GK, than a standard estimation by NACRE compilation, which is usually utilized for investigating evolutions of stars. It is thus very important to give predictions from other theoretical methods to solve this discrepancy. For this purpose, we introduce a new theoretical approach based on an imaginary-time method, which has an advantage that the knowledge of three-body boundary condition is not required. We show that our results are consistent with the NACRE compilation for whole temperature region from 1 GK to 0.01 GK. We also discuss the reason why the coupled-channel approach gives the much larger reaction rate at low temperature region. This exists in truncation of the channel number adopted for continuum states of 8Be, giving a rise to a large enhancement of the reaction rate at low temperature region.

Yukinori Yasui, Osaka City Univ

CKYと時空の隠れた対称性

Meeting room 1, Kenkyu honkan 1F
Kerr時空を表示する便利な方法は,Boyer-Lindquist座標と呼ばれる極座標を使うことである.このときKerr時空上の測地線方程式,Dirac方程式等々の場の方程式が変数分離するという不思議な性質がある.このようなKerr時空の“隠れた対称性”の正体がConformal Killing-Yano(CKY)テンソルであることを最初に見つけたのはWalker-Penrose(1970 年)である.また,CKYを拡張された対称性として純粋に数学的視点から導入したのは柏田,立花(1968年)たちの研究にまで遡る.本講演では,時空にCKYがどのくらい存在するかという基本的な問題に対する新しいアプローチを紹介したい.また,その応用として,Kerr時空にはCKYがただ一つ存在することが示される.

飛岡幸作, カブリ数物連携宇宙研究機構

A Natural Higgs Mass in Supersymmetry from Non-Decoupling Effects

Meeting room1, Kenkyu honkan 1F
The Higgs mass implies fine-tuning for minimal theories of weak scale supersymmetry (SUSY). Non-decoupling effects can boost the Higgs mass when new states interact with the Higgs, but new sources of SUSY breaking that accompany such extensions threaten naturalness. We show that a singlet with a Dirac mass can increase the Higgs mass while maintaining naturalness in the presence of large SUSY breaking in the singlet sector. We explore the modified Higgs phenomenology of this scenario, which we call the “Dirac NMSSM.”

Pedro Jimenez-Delgado, Jefferson Lab.

Extractions of polarized and unpolarized parton distributions functions

Seminar room, Kenkyu honkan 3F
The Jefferson Lab Angular Momentum (JAM) collaboration is a new initiative aimed at the study of the angular-momentum-dependent structure of the nucleon. First results on the determination of spin-dependent parton distribution functions from world data on polarized deep-inelastic Scattering will be presented. In the second part of the talk the ongoing update of the JR unpolarized parton distributions will be reported. Different aspects or polarized and unpolarized global QCD analysis will be discussed, including effects due to the nuclear structure of targets, target-mass corrections and higher twist contributions to the structure functions

Kenta Hotokezaka, Kyoto University

Mass ejection of compact binary merger and the progenitor model of GRB 130603B

Seminar Room, Kenkyu Honkan 3F
A transient powered by the radioactive decay of r-process elements the so-called kilonova is one of the possible observational consequences of compact binary mergers including at least one neutron star. Recent observations discover a kilonova associated with the short GRB130603B.
We explore the possible progenitor of this event based on numerical-relativity simulations and radiative transfer simulations for the dynamical ejecta of binary neutron star (NS-NS) mergers and black hole – neutron star binary (BH-NS) mergers. We show that the only soft EOS models could produce the observed luminosity for the NS-NS ejecta. Our results also show that a BH-NS model is more favorable for GRB130603B than a NS-NS model.
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