Takemichi Okui, Florida State University
Partially Acoustic Dark Matter, Interacting Dark Radiation, and Large Scale Structure
Meeting room 1, Kenkyu honkan 1F, slides (kek.jp only)
The standard paradigm of collisionless cold dark matter is in tension with measurements on large scales. In particular, the best fit values of the Hubble rate H0 and the matter density perturbation sigma8 inferred from the cosmic microwave background seem inconsistent with the results from direct measurements. We show that both problems can be solved in a framework in which dark matter consists of two distinct components, a dominant component and a subdominant component. The primary component is cold and collisionless. The secondary component is also cold, but interacts strongly with dark radiation, which itself forms a tightly coupled fluid. The growth of density perturbations in the subdominant component is inhibited by dark acoustic oscillations due to its coupling to the dark radiation, solving the σ8 problem, while the presence of tightly coupled dark radiation ameliorates the H0 problem. The subdominant component of dark matter and dark radiation continue to remain in thermal equilibrium until late times, inhibiting the formation of a dark disk. We present an example of a simple model that naturally realizes this scenario in which both constituents of dark matter are thermal WIMPs. Our scenario can be tested by future stage-IV experiments designed to probe the CMB and large scale structure.
Yu Hamada, Kyoto University
Axial U(1) current in Grabowska and Kaplan’s formulation (in Japanese)
Meeting room 1, Kenkyu honkan 1F
最近、カイラルゲージ理論の非摂動的な定式化としてdomain-wall fermionとgradient flowを組み合わせた方法がKaplanたちにより提案された。通常のdomain-wall fermionでは2枚のdomain wall上にそれぞれ異なるカイラリティを持った無質量フェルミオンが局在するが、ここでバルクのゲージ場をgradient flowを用いて減衰させることで、片方のカイラリティのフェルミオンのみがゲージ場と相互作用できるようになる。我々はこの方法をもとに、4次元のベクトル的な理論における軸性U(1)カレントについて調べた。軸性U(1)カレントの素朴な定義として、gradient flowで減衰していく仮想的なU(1)ゲージ場を新たに導入し、そのU(1)ゲージ場のdomain wall上の値で有効作用を変分したものを考えた。しかし、このカレントはバルクの寄与も含んでおり保存してしまいアノマリーを再現しないことがわかった。本講演ではまずKaplanたちの定式化を簡単に紹介した後、この軸性U(1)カレントの保存について解説する。最後に、正しくアノマリーを再現するような軸性U(1)カレントの定義を提案する。
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
