セミナー

Jiro Arafune, National Institution for Academic Degrees and University Evaluation

Relic Neutrino の反射、屈折について

Seminar hall, 3 go-Kan
Relic Neutrinoの直接観測は大変困難だが、標的からのニュートリノのコヒーレントな反射、屈折によるrecoilを観測できないか、という理論的な考察が古くからなされてきた。そして、ほとんど不可能という結論がされてきている。主な理由は、コヒーレントな散乱では、ニュートリノが標的へ入射する際と、標的から脱出する際とで、recoilが相殺するからである。それを相殺しない工夫を考察しているのだが、まだよくわからないところがあって、確定的な結論に至っていない。議論していただけると幸いです。

Ken-ichi Nishikawa, UAH/CSAPR

Radiation from accelerated particles in shocks and reconnections

Meeting room 3, Kenkyu honkan 1F
We have investigated particle acceleration and shock structure associated with an unmagnetized relativistic jets propagating into an unmagnetized plasmas. Strong magnetic fields generated in the trailing shock contribute to the electronstransverse deflection and acceleration. We have calculated, self-consistently, the radiation from electrons accelerated in the turbulent magnetic fields. We found that the synthetic spectra depend on the Lorentz factor of the jet, its thermal temperature and strength of the generated magnetic fields. The properties of the radiation may be important for understanding the complex time evolutionand/or spectral structure in gamma-ray bursts, relativistic jets in general, and supernova remnants.

Laila Alabidi, Yukawa Institute for Theoretical Physics, Kyoto University

A further discriminatory signature of inflation

Meeting room 3, Kenkyu honkan 1F
In this talk I revise the current status of canonical single field models of inflation in light of the WMAP 7 data, using the observational bounds on the spectral index and tensor fraction, extracted using the large scale measurements of the Cosmic Microwave Background. I then extend this analysis to include models which predict a significant positive running of the spectral index, which can lead to the production of Primordial Black Holes (PBHs) towards the end of inflation. I then explain the concept of induced gravitational waves, which are gravitational waves induced by scalar perturbations re-entering the horizon during nucleosynthesis. I consider the case where the scalar perturbations are created by Hilltop-type and Running Mass Models, and where the gravitational waves are induced early on in the radiation phase of the Universe. I explore the impact a detection of such GWs would have on the field of Inflation Model Discrimination in general. I show that the Hilltop-type model can produce observable induced gravitational waves within the range of BBO and DECIGO for integral and fractional powers of the potential within a reasonable number of e−folds. I also show that the running mass model can produce a spectrum within the range of these detectors, but require that inflation terminates after an unreasonably small number of e−folds.

Yaroslav klopot, Dubna, JINR

Axial anomaly and transition form factors of pseudoscalar mesons

Meeting room 1, Kenkyu honkan 1F
We study photon-meson transition form factors of pseudoscalar mesons by means of anomaly sum rule, a relation which follows from dispersive representation of axial anomaly. As the anomaly sum rule is an exact relation (perturbative and nonperturbative corrections are absent), it allows us to study the interplay between possible corrections to continuum and to lower states within method which does not rely on QCD factorization hypothesis. We show, relying on the recent data of the BaBar Collaboration, that while the relative correction to continuum is quite small, the correction to continuum can dramatically change the pion form factor. In the octet channel, where a strong mixing between $eta$ and $eta’$ is present, the anomaly sum rule allows to get additional constraints for the mixing parameters. The notion of quark-hadron duality in our approach is discussed.

Hayato Motohashi, RESCEU, University of Tokyo

f(R) models for the early and the present acceleration of the Universe

Meeting room 1, Kenkyu honkan 1F
f(R) gravity is a simple and nontrivial extension of General Relativity. The idea was originally proposed in 1980 by Starobinsky, and now it is recognized as R^2 inflationary model. Several years ago, it was also applied to describe dark energy in the present Universe. Although some of f(R) models can satisfy laboratory, Solar system and cosmological tests, it was found that there are weak singularities and other problems in this class of models. Recently, it is found that we are able to cure the problem and describe both accelerating expansion in the early and the present Universe. I will talk about this class of f(R) models and the dynamics during inflation and reheating.

Gergely Fejos, The Univ of Tokyo

An approximate large-N solution of the U(N)xU(N) model from 2PI effective action

Seminar room, Kenkyu honkan 3F
I will briefly review the 2PI (or Phi-derivable) formalism and as an application I will present an approximate large-N solution of the U(N)xU(N) meson model. What makes a particular importance of this is that even the leading order large-N solution of the model is unknown. The present solution is based on an assumption on the mass hierarchy of the spectrum, which is proved to be valid in certain parts of the parameter space. The ground state of the system was explored and found that a U(N)xU(N) -> U(N-1) spontaneous symmetry breaking can be realized. The finite temperature study showed that the system (partially) suffers a 1st order transition. Properties of this transition will also be highlighted.

Carina Popovici, Giessen U

Dyson-Schwinger approach to QCD and three-dimensional QED

Meeting room 3, Kenkyu honkan 1F
In this talk we describe the DS approach to QCD and 3-dimensional QED. After sketching the formal derivation of the DSEs, we first consider the heavy quark limit of nonperturbative Coulomb gauge QCD and the confinement problem. In this framework, we demonstrate, under truncation, a direct connection between the Yang-Mills sector of the theory (the temporal component of the gluon propagator) and the quark confining potential. We further show that only color singlet quark-antiquark (meson) and three-quark (baryon) bound states are physically allowed, and discuss the implications for phenomenological studies of hadrons. Turning to QED3, we consider an infinite slab of graphene and investigate its properties in the setup of an effective quantum field theoretical model. Specifically, we study the gap generation, also in relation to the structural defects and transport properties of graphene. In particular, we show that breaking the sublattice symmetry in a graphene monolayer leads to confined states of massless Dirac fermions — experimentally, this corresponds to chemical bonding of foreign atoms to carbon atoms.

Tsubasa Ichikawa, Research Center for Quantum Computing, Kinki U

エラー耐性のあるユニタリ変換と幾何学的位相

Seminar room, Kenkyu honkan 3F
量子系を制御するにあたっては、エラーやノイズに耐性がある操作が望ましい。そのような技術のひとつとして、主に核磁気共鳴の技術として発展してきた複合パルス法というものがある。これは、目的の操作を実装するにあたって、ある程度の冗長性をもたせて設計し、操作過程でのエラーが相殺するようにしておくのである。このようにして作成した操作を複合パルスという。本講演では、あるタイプのエラーに関して耐性を持たせた複合パルスは、全て幾何学的位相を用いたユニタリ変換となっていることを示す。

西尾亮一, IPMU

Studying DVCS in gravitational dual (in Japanese)

Seminar room, Kenkyu honkan 3F
仮想光子とハドロンの非前方散乱(DVCS)は、一般化されたパートン分布(GPD)を決定できるという点で興味深い。GPDは散乱振幅におけるゲージ理論の非摂動部分なので、通常の解析計算からは導出できない。なので私は、ゲージ/重力対応による、DVCSとGPDのモデルを提示したい。ゲージ理論側ではGPDとは、DVCSの散乱振幅を演算子展開(OPE)した際の、twist 2の演算子の寄与である。従って重力理論側からGPDを決定しようとする際に問題となるのは、重力理論側でのDVCSの散乱振幅に対して、OPEに相当する展開を行い、twist 2の演算子の寄与を決定し抽出することである。これを詳しく整理することで、最新の研究ではskewedness依存性も取り扱えるようになった。この点についても紹介する予定である。

A.B. Balantekin, University of Wisconsin-Madison and NAOJ

PERSPECTIVES IN NEUTRINO PHYSICS

Meeting room 1, Kenkyu honkan 1F
After a very exciting discovery stage during the last decade, neutrino physics is now at precision stage. Additionally neutrinos play a rather special role in astrophysics. This talk will cover one example of each; i) Testing the CPT theorem and physics beyond the Standard Model using solar neutrinos; ii) Invariants associated with the supernova neutrinos and their implications for observations.

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