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.
Dmitry Khangulyan, JAXA
Shedding light on the pulsar wind
Meeting room 1, Kenkyu honkan 1F
Pulsars are believed to eject ultrarelativistic electron-positron winds that propagate to the large distances leading to the formation of the extended non-thermal sources known as plerions. The wind has been proposed to originate close to the light cylinder, and carry the rotational energy losses of the pulsar. At the beginning the wind is dominated by electromagnetic energy (Poynting flux), but at some later stage the wind is accelerated with most of the Poynting flux being converted to the kinetic energy of bulk motion. Such winds have not been yet observed, therefore the proposed scenario has been deemed inconclusive. The `cold’ winds (in the sense of the low energy of the electrons in the frame of moving plasma) represent a form of “dark substance” since, despite the very high energy of the wind particles, the wind emission is extremely weak. In fact, the pulsar winds are visible only in inverse Compton gamma-rays. Recent observations in high energy (HE) and very high energy (VHE) domains with Fermi Large Area Telescope (Fermi/LAT) and ground based Cherenkov detectors Magic and Veritas allow the key properties of the pulsar winds to be measured in a few important systems. In particular, the recently observed VHE pulsed gamma-rays emitted by the Crab pulsar are best explained as arising from the X-ray photons scattering off the wind’s electrons. This finding supports the presence of an ultrarelativistic wind in the Crab pulsar, and provides unique information about the acceleration site of the wind at R_w ~ 30 light cylinders, and its Lorentz factor, Γ_0 = 5 x 105. In the case of the pulsars located in close binary systems, the dense stellar photon field provided by the companion star can dramatically enhance the interaction rate of wind electrons with target photons, leading to the formation of detectable gamma-ray signal. Interestingly, the bright gamma ray flare of the binary pulsar PSR B1259-63/LS2883 detected by the Fermi/LAT after several weeks of the periastron passage, can be also interpreted as the inverse Compton (IC) emission of the unshocked electron-positron pulsar wind with Lorentz factor Γ_0 ~104.
Aleksey Cherman, University of Cambridge
Sneaking up on dense QCD using large N methods
Meeting room 1, Kenkyu honkan 1F
Finite-density QCD notoriously suffers from the fermion sign problem, which makes lattice Monte Carlo simulations essentially impossible. As a result, we have little non-perturbative information on the behavior of QCD at finite baryon number density. I will discuss a recent proposal to dodge the sign problem by exploiting orbifold equivalence, a property of the large N limit of QCD. The proposal starts with the observation that if the gauge group of QCD is changed from SU(N) to SO(N), the sign problem does not appear at finite baryon number chemical potential, and the resulting theory can be studied on the lattice. Despite this seemingly drastic change, it turns out that there is a large N orbifold equivalence between the SO(N) theory and SU(N) QCD. I will argue that with some extra work, the equivalence can be made to hold at finite chemical potential, while the SO theory does not have a sign problem. This opens up the prospect of learning about QCD at finite baryon number density using lattice studies of the SO(N) theory.
Kunio Kaneta, Osaka University
Parity Violation in SUSY QCD
Meeting room 1, Kenkyu honkan 1F In SUSY QCD, a mass of left-handed squark is generally not the same as that of right-handed squark. Therefore, parity can be violated in QCD process by quark-squark-gluino vertexes. We focus on this parity violation, and discuss following two topics.
