Yoshimasa Hidaka, RIKEN
Nambu-Goldstone modes in open classical and quantum systems
Meeting room 1, Kenkyu honkan 1F, slides (kek.jp only)
We discuss generalization of the Nambu-Goldstone theorem to open classical and quantum systems. For a Hamiltonian system, it is known that there appears a gapless excitation called the Nambu-Goldstone mode, when a global continuum symmetry is spontaneously broken. In this theorem, a conservation law plays an important role. In contrast, for an open system, the ordinary conservation law is violated because of interaction with environment. Nevertheless, we can define another symmetry using path integral formalism, whose Noether charge is different from ordinary one. We show that the Nambu-Goldstone mode appears when the symmetry is spontaneously broken in the open system. The NG mode is generally not propagating but dissipative. We also show the general form of the dispersion relation using Ward-Takahashi identity. We discuss application to a real system such as an active matter system.
Kohta Hatakeyama, Shizuoka University)
Correlation functions and renormalization in a scalar field theory on the fuzzy sphere
Meeting room 1, Kenkyu honkan 1F
We study correlation functions in a scalar field theory on the fuzzy sphere, which is realized by a matrix model where the matrix size plays a role of the UV cutoff. We identify the Berezin symbol for a matrix with a field, and we calculate the correlation functions of the fields by Monte Carlo simulation. By tuning a parameter of the theory, we find that the two-point and four-point correlation functions agree for different matrix sizes. This result strongly suggests that the theory is renormalizable.
Ryosuke Sato, Weizmann Institute
Secondary astrophysical production of anti-deuteron and anti-Helium3 cosmic ray
Seminar room, Kenkyu honkan 3F, slides (kek.jp only)
Cosmic-ray anti-deuterium and anti-helium have long been suggested as probes of dark matter, as their secondary astrophysical production was thought extremely scarce. But how does one actually predict the secondary flux? Anti-nuclei are dominantly produced in pp collisions, where laboratory cross section data is lacking. We make a new attempt at tackling this problem by appealing to a scaling law of nuclear coalescence with the physical volume of the hadronic emission region. The same volume is probed by Hanbury Brown-Twiss (HBT) two-particle correlations. We demonstrate the consistency of the scaling law with systems ranging from central and off-axis AA collisions to pA collisions, spanning 3 orders of magnitude in coalescence yield. Extending the volume scaling to the pp system, HBT data allows us to make a new estimate of coalescence, that we test against preliminary ALICE pp data. For anti-helium the resulting cross section is 1-2 orders of magnitude higher than earlier estimates. The astrophysical secondary flux of anti-helium could be within reach of a five-year exposure of AMS02.
Tomohiro Fujita, Department of Physics, Kyoto University
[Cosmophysics group seminar] Gravitational wave production during inflation
Meeting room 1, Kenkyu honkan 1F, slides (kek.jp only)
It is well known that the amplitude of the gravitational wave (GW) produced during inflation is proportional to the energy scale of inflation. However, it is true only if (i) GW is described by Einstein theory (GR) and (ii) the GWs from vaccum fluctuation is dominant. I will discuss the cases where the above two conditions are not satisfied. In particular, I will explain the new model in which the axion-SU(2) coupled system generates GW during inflation and its observational consequence.
Hajime Otsuka, Waseda University
Three-generation models in SO(32) heterotic string theory
Meeting room 1, Kenkyu honkan 1F
We show realistic supersymmetric standard-like models from SO(32) heterotic string theory on factorizable tori and smooth, quotient complete intersection Calabi-Yau three-folds with multiple line bundles. The stable line bundles lead to the three chiral generations of quarks and leptons without chiral exotics. Massless spectra of our models also include Higgs fields, which have desired Yukawa couplings to quarks and leptons at the tree-level. Finally, we discuss the axion-induced baryogenesis scenario induced by the axion-dependent Yukawa couplings.
Yu Watanabe, YITP Kyoto University
量子f-divergenceの一般化とそこから誘導される情報幾何的性質
Seminar room, Kenkyu honkan 3F
正値性およびCPTP単調性を満たす量子f-divergenceには、様々なバリエーションがあることが知られている。我々は2つの作用素単調関数をパラメタとしてもつ一般化された量子f-divergenceのクラスを定義し、それらが正値性やCPTP単調性を持つことを示した。また、いくつかの既存の量子f-divergenceがこのクラスに含まれていることを示した。ひとたび量子状態空間に対してdivergenceが定義されると、その微分からその空間の計量や接続を得ることができる。一般化された量子f-divergenceからどのような計量や接続が得られるかを示した。
Kenji Toma, Frontier Research Institute for Interdisciplinary Sciences, Tohoku University
[Cosmophysics group seminar] Relativistic Jets Driven by Black Holes
Meeting room 1, Kenkyu honkan 1Fslides (kek.jp only)
Relativistic Jets are collimated plasma outflows with speeds close to the light speed from the vicinities of black holes, and observed in association with some active galaxies and gamma-ray bursts. They could be the emitters of high-energy cosmic-rays, high-energy neutrinos, and gravitational waves. In spite of the significant progress in recent years, there are still many unresolved key issues concerning the energy injection, mass injection, acceleration, collimation, and energy dissipation/emission mechanisms of jets. This talk reviews the current theoretical framework for solving those issues and then focuses on the energy injection mechanism, in particular the Blandford-Znajek process, i.e., steady electromagnetic energy injection by rotating black holes themselves. Physical differences among this process, pulsar winds, and mechanical Penrose process are discussed.
Valentin V. Khoze, Durham U., IPPP
Higgsplosion
Seminar room, Kenkyu honkan 3F
I will introduce and review the Higgsplosion phenomenon proposed in my recent work with Michael Spannowsky https://arxiv.org/pdf/1704.03447.pdf Higgsplosion occurs at some critical energy in the 10^2-10^3 TeV range and leads to an exponentially growing decay rate of highly energetic particles into multiple Higgs bosons. We argue that this a well-controlled non-perturbative phenomenon in the Higgs-sector which involves the final state Higgs multiplicities n in the regime nλ ≫ 1 where λ is the Higgs self-coupling. If this mechanism is realised in nature, the cross-sections for producing ultra-high multiplicities of Higgs bosons are likely to become observable and even dominant in this energy range. At the same time, however, the apparent exponential growth of these cross-sections at even higher energies will be tamed and automatically cut-off by a related Higgspersion mechanism. As a result, and in contrast to previous studies, multi-Higgs production does not violate perturbative unitarity. We then argue that the effects of Higgsplosion alter quantum corrections from very heavy states to the Higgs boson mass. Above a certain energy, which is much smaller than their masses, these states would rapidly decay into multiple Higgs bosons. The loop integrals contributing to the Higgs mass will be cut off not by the masses of the heavy states, but by the characteristic loop momenta where their decay widths become comparable to their masses. Hence, the cut-off scale would be many orders of magnitude lower than the heavy mass scales themselves, thus suppressing their quantum corrections to the Higgs boson mass.
Yuji Satoh, University of Tsukuba
A world-sheet approach to non-geometric backgrounds in string theory
Meeting room 1, Kenkyu honkan 1F, slides (kek.jp only)
String dualities allow us the non-geometric string backgrounds whose transition functions involve duality transformations. We first discuss such non-geometric backgrounds obtained through T-duality, i.e. T-folds, from the world-sheet point of view. In particular, we construct their modular invariant partition functions systematically based on the momentum lattices. Second, as an application, we show that our non-geometrical setting, or its analogs, can simply realize non-supersymmetric backgrounds with vanishing cosmological constant at one loop, as well as non-supersymmetric D-branes with vanishing self-overlap, which give non-perturbatively small cosmological constant. If time is allowed, we would also like to comment on the world-sheet theories obtained from conformal interfaces.
Yuichi Uesaka, Osaka University
Charged lepton flavor violating process in a muonic atom, μ- e- → e- e-
Meeting room 1, Kenkyu honkan 1F
