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
Nuclear structure changes drastically by low-excitation energies. We discuss deformations and clustering effects, which play important roles in nuclear structures. Nuclei have various structures such as coexistence of various rotational bands, prolate-oblate shape coexistence, multi-cluster states, and so on. In order to understand those structures, both of deformations and clustering should be taken into account.
Laszlo Feher, Institute for Particle and Nuclear Physics, Wigner RCP, HAS
The Ruijsenaars self-duality map as a mapping class symplectomorphism
Seminar Room, Kenkyu Honkan 3F
We explain that the self-duality symplectomorphism of the completely integrable compactified trigonometric Ruijsenaars-Schneider system arises from the natural action of the mapping class group on the moduli space of flat SU(n) connections on the one-holed torus. The talk is based on joint work with C. Klimcik reviewed in arXiv:1203.3300.
Andrew G. Akeroyd, University of Southampton
Phenomenology of the Higgs Triplet Model at the LHC
Meeting Room 1, Kenkyu Honkan 1F
