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.
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.
齋川賢一 , 東京大学宇宙線研究所
Axion production from topological defects
Meeting Room 1, Kenkyu Honkan 1F
The axion arises as a consequence of the spontaneous breaking of Peccei-Quinn (PQ) symmetry, which is a viable solution to the strong CP problem of quantum chromodynamics and may explain the dark matter of the universe. However, this PQ mechanism predicts the formation of topological defects such as strings and domain walls in the early universe, and the evolution and decay of these defects give some implications for the early universe cosmology. In particular, the analysis of the spectrum of axions radiated from networks of topological defects revealed that axions produced by the defects give significant contributions to the relic cold dark matter abundance. In this talk, I will report recent results of field-theoretic lattice simulations of topological defects and discuss cosmological constraints on axion models.
藤川和男, RIKEN Nishina Center
Universally valid Heisenberg uncertainty relation
Seminar room, Kenkyu honkan 3F The original formulation of the uncertainty relation by Heisenberg, which is based on a thought experiment with an emphasis on measurement processes, lacked a simple mathematical basis compared to the widely accepted relations of Kennard and Robertson. In fact, a commonly assumed form of the Heisenberg-type error-disturbance relation has been recently invalidated by spin-measurements at Vienna [J. Erhart, et al., Nature Phys. 8, 185 (2012)]. On the other hand, the analysis of measurement processes is missing in the relations of Kennard and Robertson. Here we suggest to reformulate the Heisenberg uncertainty relation in such a manner that it incorporates both the intrinsic quantum fluctuations and the effects of measurement, and yet with the same mathematical rigor as the relations of Kennard and Robertson and thus universally valid. This relation, which assumes the form δxδp ∼ ℏ(instead of ℏ/2) when written in a popular notation, is regarded as a combination of the past works on the uncertainty relation by Arthurs and Kelly, who emphasized the role of measurement apparatus, and by Ozawa who clarified the mathematical structure.
The original formulation of the uncertainty relation by Heisenberg, which is based on a thought experiment with an emphasis on measurement processes, lacked a simple mathematical basis compared to the widely accepted relations of Kennard and Robertson. In fact, a commonly assumed form of the Heisenberg-type error-disturbance relation has been recently invalidated by spin-measurements at Vienna [J. Erhart, et al., Nature Phys. 8, 185 (2012)]. On the other hand, the analysis of measurement processes is missing in the relations of Kennard and Robertson. Here we suggest to reformulate the Heisenberg uncertainty relation in such a manner that it incorporates both the intrinsic quantum fluctuations and the effects of measurement, and yet with the same mathematical rigor as the relations of Kennard and Robertson and thus universally valid. This relation, which assumes the form δxδp ∼ ℏ(instead of ℏ/2) when written in a popular notation, is regarded as a combination of the past works on the uncertainty relation by Arthurs and Kelly, who emphasized the role of measurement apparatus, and by Ozawa who clarified the mathematical structure.
Ref. K. Fujikawa. Phys. Rev. A85, 062117 (2012).
Rabin Banerjee, S N Bose National Centre for Basic Science
Unifying tunneling and anomaly based approaches for Hawking effect
Seminar Room, Kenkyu Honkan 3F
We consider the tunneling formalism, based on density matrix, and the covariant trace and diffeomorphism anomaly formalism to discuss the Hawking effect. The two approaches are connected using the notion of chirality.
Yong Tang, National Center for Theoretical Sciences
Electroweak Vacuum Stability with Neutrino and Dark Matter
Meeting Room 1 , Kenkyu Honkan 1F
Motivated by the discovery of the Standard Model (SM) Higgs mass around 125 GeV at the LHC, we study the vacuum stability and perturbativity bounds on Higgs scalar of the SM extensions including neutrinos and dark matter (DM). Guided by the SM gauge symmetry and the minimal changes in the SM Higgs potential we consider two extensions of neutrino sector (Type-I and Type-III seesaw mechanisms) and DM sector (a real scalar singlet (darkon) and minimal dark matter (MDM)) respectively. The darkon contributes positively to the $beta$ function of the Higgs quartic coupling $lambda$ and can stabilize the SM vacuum up to high scale. Similar to the top quark in the SM, the cause of instability is sensitive to the size of new Yukawa couplings between heavy neutrinos and Higgs boson, namely, the scale of seesaw mechanism. MDM and Type-III seesaw fermion triplet, two nontrivial representations of $SU(2)_{L}$ group, will bring the additional positive contributions to the gauge coupling $g_{2}$ renormalization group (RG) evolution and would also help to stabilize the electroweak vacuum up to high scale. Reference: arXiv:1202.5717
Nobuhiro Maekawa, Nagoya U
Spontaneous CP violation in E6 GUT and flavor physics
Meeting Room 1, Kenkyu Honkan 1F
It is shown that the origin of Kobayashi-Maskawa phase can be understood by spontaneous CP violation in E6 GUT with family symmetry and moreover, it can solve the SUSY CP problem, especially the strong constraint for the effective SUSY type sfermion mass spectrum from CEDM can be satisfied in a non-trivial way. The naive problem for massless mu neutrino can be solved by considering the higher dimensional operators which are allowed by the symmetry. As the result, realistic neutrino masses iand mixings including large theta13 can be obtained. In the end of this talk, we will comment on the 125 GeV Higgs for this scenario.
Yasutaka Taniguchi, U Tsukuba
Cluster correlations in largely deformed states of nuclei
Seminar Room, Kenkyu Honkan 3F
