Toshifumi Noumi, RIKEN
Effects of heavy fields during inflation
Meeting room 3, Kenkyu honkan 1F
Effects of heavy fields during inflation will be discussed. Inflationary models based on high energy theories, such as supergravity and superstring theory, generically contain heavy scalar fields in addition to the inflaton. Such heavy scalar fields could be therefore used as a probe of high energy physics. In this talk, I will discuss multi-field inflation models with a turning background trajectory, as a possible scenario heavy fields can affect inflationary dynamics. When heavy fields are excited after the turn and oscillate around the bottom of the potential, the following two effects are generically induced: deformation of the inflationary background spacetime and conversion interactions between adiabatic and isocurvature perturbations. I will discuss such effects on primordial power spectra of curvature perturbations.
Tomohiro Nakama, RESCEU
Revealing the formation condition of primordial black holes by numerical simulations
Meeting room 1, Kenkyu honkan 1F
Primordial black holes (PBHs) are an important tool in cosmology to probe the primordial spectrum of small-scale curvature perturbations that reenter the cosmological horizon during radiation domination epoch. We numerically solve the evolution of spherically symmetric highly perturbed configurations to clarify the criteria of PBHs formation using an extremely wide class of curvature profiles characterized by five parameters, (in contrast to only two parameters used in all previous papers) which specify the curvature profiles not only at the central region but also at the outer boundary of configurations. It is shown that formation or non-formation of PBHs is determined entirely by only two master parameters one of which can be presented as an integral of curvature over initial configurations and the other is presented in terms of the position of the core and the boundary.
Noriaki Kitazawa, Tokyo Metropolitan University
Towards constructing realistic string models with D-branes
Meeting Room 1, Kenkyu-Honkan 1F
In the first part of the seminar some basic ingredients of the string models of particle physics are reviewed. The mechanisms to obtain chiral fermion spectrum at the intersection of D-branes or on the D-branes at a singularity are briefly explained. An attempt to construct a model with non-trivial Yukawa couplings is introduced. In the second part of the seminar two systems of D-branes without supersymmetry are introduced; the system of D-branes at non-supersymmetric orbifold fixed point, and the system of so called “brane supersymmetry breaking”. The NS-NS tadpole problem of non-supersymmetric system is discussed. The possible spontaneous gauge symmetry breaking in two concrete models, corresponding to the above two systems, is discussed.
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
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
