Nobuya Nishimura, YITP, Kyoto University
Synthesis of the Trans-Iron Elements in Stars
Meeting room 1, Kenkyu honkan 1F, slides (kek.jp only)
Stellar nucleosynthesis beyond iron-group nuclei provides additional problems that we do not encounter when studying nucleosynthesis processes for light nuclei. Besides ambiguity in the determination of astrophysical sites/conditions, uncertainties in nuclear physics inputs have signifiant impacts on the theoretical nucleosynthesis predictions. In this talk, I present recent results of comprehensive nucleosynthesis studies, focusing on the uncertainties of relevant nuclear reactions and decays. The evaluated uncertainty range for the several nucleosynthesis processes, e.g., s- and r-processes, gamma-process and nup-process, are discussed. I also show the lists of “key reactions”, which have strong impacts on the nucleosynthesis yields, based on our Monte-Carlo based analysis.
Alessandro Sfondrini, ETH Zürich - Institute of Theoretical Physics
Integrability, correlation functions, and stringy WZW models
Meeting room 1, Kenkyu honkan 1F Integrability techniques have been crucial to compute non-protected observables in AdS/CFT, starting from the planar spectrum (two-point functions) of the theory. Recently it was understood that planar three- and higher-point functions, as well as non-planar observables, can be computed by integrability techniques. I will discuss these advances in relation to one recently-discovered integrability setup: the AdS3xS3xT4 stringy Wess-Zumino-Witten model.
Integrability techniques have been crucial to compute non-protected observables in AdS/CFT, starting from the planar spectrum (two-point functions) of the theory. Recently it was understood that planar three- and higher-point functions, as well as non-planar observables, can be computed by integrability techniques. I will discuss these advances in relation to one recently-discovered integrability setup: the AdS3xS3xT4 stringy Wess-Zumino-Witten model.
Based on: 1611.05436, 1710.10212, 1804.01998, 1806.00422.
宮武宇也, KEK和光原子核科学センター
[第七回KEK連携コロキウム]金・白金はどこで、どのように生れたのか-WNSCのアプローチ-
つくばキャンパス研究本館/小林ホール東海キャンパス東海1号館116号室 (TV会議中継)
物質の起源と銀河の進化を探求する宇宙核物理と呼ばれる研究領域は、宇宙物理、天文観測、原子核物理などの研究者が連携して急速に進化を遂げている領域です。原子核物理のセクターでは、短寿命原子核などが介在する元素合成過程を地上の加速器実験で再現し、起源天体の解明・特定を目指しています。２０１６年度より共同利用を始めた和光原子核科学センター（WNSC）の元素選択型質量分離器（KEK Isotope SeparationSystem；KISS)も、宇宙核物理に寄与するために設置された装置です。この装置によるおもな研究課題は、天体における重元素合成過程、特に金や白金を生み出した速い中性子捕獲(r-)過程の研究を通じて、爆発的天体現象の解明を行う点にあります。このコロキウムでは、最近の中性子星合体天文観測からのインパクトも含めて、KISSプロジェクトの一端をご紹介したいと思います。
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)
