Chinami Kato, Waseda University
The evolutions of massive stars and the importance of neutrino observations
Meeting room 1, Kenkyu honkan 1F, slides (kek.jp only)
Massive stars with more than 8 solar mass initially are supposed to be progenitors of core-collapse supernovae, however, there still remain many problems about the understanding of their evolutions and deaths, especially the interior profile of cores and the explosion mechanism. In order to solve these problems, some observations are necessary. Then we focus on the observations of “neutrinos”, which are emitted inside the stellar core or proto-neutron stars and decide their evolutionary paths. In this talk, I want to talk about what we can learn about the stellar evolutions from the observations of pre-SN and SN neutrinos and what we should do theoretically for the next galactic supernovae which will occur in the near future. In detail, we calculate the realistic neutrino luminosities and spectra for all flavors and estimate the number of events at the terrestrial neutrino detectors.
Debasish Borah, IIT Guwahati, India
When Freeze-out Precedes Freeze-in: Sub-TeV Dark Matter with Radiative Neutrino Mass
Seminar room, Kenkyu honkan 3F
We discuss a minimal predictive scenario for dark matter and radiative neutrino mass where the relic abundance of dark matter is generated from a hybrid setup comprising of both thermal freeze-out as well as non-thermal freeze-in mechanisms. Considering three copies of fermion triplets and one scalar doublet, odd under an unbroken reflection symmetry Z2, to be responsible for radiative origin of neutrino mass, we consider the lightest fermion triplet as a dark matter candidate which remains under-abundant in the sub-TeV regime from usual thermal freeze-out. Late decay of the Z2-odd scalar doublet into dark matter serves as the non-thermal (freeze-in) contribution which not only fills the thermal dark matter deficit, but also constrains the mother particle’s parameter space so that the correct relic abundance of dark matter is generated. Apart from showing interesting differences from the purely freeze-out and purely freeze-in dark matter scenarios, the model remains testable through disappearing charge track signatures at colliders, observable direct and indirect detection rates for dark matter and prediction of almost vanishing lightest neutrino mass.
Takasumi Maruyama, KEK
Light Sterile Neutrino: is there any good pictures?
Seminar room, Kenkyu honkan 3F, slides (kek.jp only)
In this seminar, the status of the light sterile neutrino searches and whether there is good and reasonable physics pictures for the neutrinos are discussed. The light sterile neutrino is non-weak interactive neutrino, and it was introduced to explain the results of the LSND experiment. The idea to exist the particle which is sensitive to gravity but not to strong, electromagnetic and weak forces are interesting, however, currently only LSND and MiniBooNE experiments provided positive results. This seminar reviews the status of the sterile neutrino searches in the world, which includes the JSNS2 experiment (J-PARC Sterile Neutrino Search at the J-PARC Spallation Neutron Source). The experiment aims the direct confirmation or refute the LSND results. It will be started from the end of JFY2018.
Xi Yin, Harvard University
Topological Defect Lines and RG Flows in 2D
Seminar room, Kenkyu honkan 3F
Topological defect lines in 2D generalize both global symmetries and Verlinde lines, and provide models of fusion categories without braiding. I will discuss their roles in CFTs and in constraining RG flows, and use them to determine the infrared (fully extended) topological quantum field theory in some examples of massive flows.
Nobuyuki Matsumoto, Kyoto University
Distance between configurations in MCMC simulations and AdS geometry in the simulated tempering algorithm
Seminar room, Kenkyu honkan, slides (kek.jp only)
For a given Markov chain Monte Carlo (MCMC) algorithm, we define distance between configurations, which quantifies difficulty of transition from one configuration to the other. This distance gives a universal form for a class of MCMC algorithms which generate local moves of configurations. The introduction of distance enables us to investigate a relaxation process in a MCMC simulation from a geometrical point of view. We here consider a system whose equilibrium distribution is highly multimodal with a large number of degenerate classical vacua. We show that, when we implement the simulated tempering method for such a system, the anti-de Sitter (AdS) geometry emerges in the extended configuration space. This talk is based on the work with M. Fukuma and N. Umeda [JHEP12(2017)001, work in preparation].
Koutarou Kyutoku, KEK
Initial data of compact object binaries for numerical relativity
Meeting room 1, Kenkyu honkan 1F Because nonlinear gravity and hydrodynamics play a crucial role, numerical-relativity simulations are necessary to understand accurately the merger stage of compact binary coalescences. In general relativity, valid initial data have to satisfy Hamiltonian and momentum constraints (reminiscent of divergence equations in Maxwell theory). Furthermore, astrophysically realistic time-evolution simulations can be performed only with astrophysically realistic initial data. These facts require us to solve constraint equations imposing realistic conditions. In this seminar, I will review the method to derive desirable initial data of compact object binaries for numerical relativity with a blackboad.
Because nonlinear gravity and hydrodynamics play a crucial role, numerical-relativity simulations are necessary to understand accurately the merger stage of compact binary coalescences. In general relativity, valid initial data have to satisfy Hamiltonian and momentum constraints (reminiscent of divergence equations in Maxwell theory). Furthermore, astrophysically realistic time-evolution simulations can be performed only with astrophysically realistic initial data. These facts require us to solve constraint equations imposing realistic conditions. In this seminar, I will review the method to derive desirable initial data of compact object binaries for numerical relativity with a blackboad.
References:
E. Gourgoulhon [gr-qc/0703035] (review)
Tatsuhiro Misumi, Akita University
't Hooft anomaly matching for circle compactification
Meeting room 1, Kenkyu honkan 1F, slides (kek.jp only)
Anomaly matching constrains low-energy physics of strongly-coupled field theories. It has been recently extended to the theories with one-form symmetries including SU(N) Yang-Mills theory with theta=pi. In this talk, we show that we develop a systematic procedure for deriving an ’t Hooft anomaly of the circle-compactified theory starting from the anomaly of the original uncompactified theory without one-form symmetries, where the twisted boundary condition for the compactified direction plays a pivotal role. As an application, we consider ZN-twisted CP^N-1 sigma model and massless ZN-QCD, and compute their anomalies explicitly. We also discuss constraints on finite-(T,mu) phase diagram of ZN-QCD based on the anomaly matching.
Kouji Nakamura, National Astronomical Observatory of Japan
Extension of the input–output relation for a Michelson interferometer to arbitrary coherent-state light sources: --- Gravitational-wave detector and weak-value amplification ---
Seminar room, Kenkyu honkan 3F
An extension of the input–output relation for a conventional Michelson interferometric gravitational-wave detector is carried out to treat an arbitrary coherent state for the injected optical beam. This extension is one of necessary researches toward the clarification of the relation between conventional gravitational-wave detectors and a simple model of a gravitational-wave detector inspired by weak-measurements in [Nishizawa, Phys. Rev. A vol.92 (2015), 032123.]. The derived input–output relation describes not only a conventional Michelson-interferometric gravitational-wave detector but also the situation of weak measurements. As a result, we may say that a conventional Michelson gravitational-wave detector already includes the essence of the weak-value amplification as the reduction of the quantum noise from the light source through the measurement at the dark port.
Nagisa Hiroshima, KEK/U. Tokyo
Modeling evolution of Dark Matter substructure and annihilation boost
Meeting room 1, Kenkyu honkan 1F We study evolution of dark matter substructures, especially how they lose the mass and change density profile after they fall in gravitational potential of larger host halos. We develop an analytical prescription that models the subhalo mass evolution and calibrate it to results of N-body numerical simulations of various scales from very small (Earth size) to large (galaxies to clusters) halos. We then combine the results with halo accretion histories, and calculate the subhalo mass function that is physically motivated down to Earth-mass scales. Our results — valid for arbitrary host masses and redshifts — show reasonable agreement with those of numerical simulations at resolved scales. Our analytical model also enables self-consistent calculations of the boost factor of dark matter annhilation, which we find to increase from tens of percent at the smallest (Earth) and intermediate (dwarfs) masses to a factor of several at galaxy size, and to become as large as a factor of ?10 for the largest halos (clusters) at small redshifts. Our analytical approach can accommodate substructures in the subhalos (sub-subhalos) in a consistent framework, which we find to give up to a factor of a few enhancement to the annihilation boost. Presence of the subhalos enhances the intensity of the isotropic gamma-ray background by a factor of a few, and as the result, the measurement by Fermi Large Area Telescope excludes the annihilation cross section greater than ?4×10?26 cm3 s?1 for dark matter masses up to ?200 GeV.
We study evolution of dark matter substructures, especially how they lose the mass and change density profile after they fall in gravitational potential of larger host halos. We develop an analytical prescription that models the subhalo mass evolution and calibrate it to results of N-body numerical simulations of various scales from very small (Earth size) to large (galaxies to clusters) halos. We then combine the results with halo accretion histories, and calculate the subhalo mass function that is physically motivated down to Earth-mass scales. Our results — valid for arbitrary host masses and redshifts — show reasonable agreement with those of numerical simulations at resolved scales. Our analytical model also enables self-consistent calculations of the boost factor of dark matter annhilation, which we find to increase from tens of percent at the smallest (Earth) and intermediate (dwarfs) masses to a factor of several at galaxy size, and to become as large as a factor of ?10 for the largest halos (clusters) at small redshifts. Our analytical approach can accommodate substructures in the subhalos (sub-subhalos) in a consistent framework, which we find to give up to a factor of a few enhancement to the annihilation boost. Presence of the subhalos enhances the intensity of the isotropic gamma-ray background by a factor of a few, and as the result, the measurement by Fermi Large Area Telescope excludes the annihilation cross section greater than ?4×10?26 cm3 s?1 for dark matter masses up to ?200 GeV.
references:
arXiv 1803.07691、1403.6827
Fumihiko Sugino, Institute for Basic Science
Highly entangled quantum spin chains and their extensions by semigroups
Meeting room 1, Kenkyu honkan 1F, slides (kek.jp only)
