Akihiro Suzuki, National Astronomical Observatory of Japan
Core-collapse supernovae and the final evolutionary states of massive stars
Meeting room 1, Kenkyu honkan 1F, slides (kek.jp only)
Massive stars play important roles in the star-forming history of galaxies throughout cosmic time. They end their lives by producing a violent explosion caused by the gravitational collapse of the iron core, called core-collapse supernovae(CCSNe). They give rise to bright optical emission, thereby making them an important tool to investigating star-forming activities of distant galaxies. One of the fundamental questions on massive star evolution is how to connect massive stars born in a specific environment to various types of CCSNe and compact remnants. This problem is still difficult to solve because of the complex interplay of various physical processes involved in massive star evolution and the explosion mechanism of core-collapse supernova themselves. Therefore, it appears that we still have a long way to go. However, recent observational and theoretical progresses, such as, progenitor detections in HST archival images and numerical modelings of CCSNe by massively parallel supercomputers, have gradually made important steps toward the ultimate goal. In this talk, I review observational features CCSNe and discuss recent topics.
Okuto Morikawa, Department of Physics, Kyushu University
Gradient flow and the Wilsonian renormalization group flow (in Japanese)
Meeting room 1, Kenkyu honkan 1F, slides (kek.jp only)
The gradient flow is the evolution of fields and physical quantities along a dimensionful parameter t, the flow time. We give a simple argument that relates this gradient flow and the Wilsonian renormalization group (RG) flow. We then illustrate the Wilsonian RG flow on the basis of the gradient flow in two examples that possess an infrared fixed point, the 4D many-flavor gauge theory and the 3D O(N) linear sigma model.
Kodai Sakurai, University of Toyama / Osaka University
Precise calculations of Higgs decay rates in various extended Higgs sectors
Seminar room, Kenkyu honkan 3F
Precision measurements of observables for the discovered Higgs boson, such as decay rates and production cross sections, play a crucial role in examining structure of the Higgs sectors. By making use of precise data of Higgs observables in future collider experiments, we aim to comprehensively test various extended Higgs models. To achieve such our goal, we previously calculated full set of renormalized Higgs boson couplings at the 1-loop level in various extended Higgs models such as the Higgs singlet model, 4 types of two Higgs doublet models and the inert doublet model. Applying those calculations, we recently computed decay rates of the Higgs boson with NLO EW and NLO QCD corrections in above models. In this talk, we discuss whether or not these models can be discriminated with deviations from the SM for the Higgs decay rates and how we extract information of mass scale of second Higgs bosons. This talk is based on arXiv:1803.01456.
Takahiro Terada, KEK
Semi-Analytic Calculation of Gravitational Wave Spectrum Induced from Primordial Curvature Perturbations
Meeting room 1, Kenkyu honkan 1F Whether or not the primordial gravitational wave (GW) produced during inflation is sufficiently strong to be observable, GWs are necessarily produced from the primordial curvature perturbations in the second order of perturbation. The induced GWs can be enhanced by curvature perturbations enhanced at small scales or by the presence of matter-dominated stages of the cosmological history, both of which are motivated in primordial black hole scenarios to explain dark matter or the LIGO/Virgo event rate. We analytically calculate the integral in the expression of the power spectrum of the induced GWs which is a universal part independent of the primordial spectrum. This makes the subsequent numerical integrals significantly easy. In simple cases, we derive fully analytic formulae for the induced GW spectrum.
Whether or not the primordial gravitational wave (GW) produced during inflation is sufficiently strong to be observable, GWs are necessarily produced from the primordial curvature perturbations in the second order of perturbation. The induced GWs can be enhanced by curvature perturbations enhanced at small scales or by the presence of matter-dominated stages of the cosmological history, both of which are motivated in primordial black hole scenarios to explain dark matter or the LIGO/Virgo event rate. We analytically calculate the integral in the expression of the power spectrum of the induced GWs which is a universal part independent of the primordial spectrum. This makes the subsequent numerical integrals significantly easy. In simple cases, we derive fully analytic formulae for the induced GW spectrum.
references:
K. Kohri and T. Terada, 1804.08577 [gr-qc] (and 1802.06785 [astro-ph.CO])
Susan Gardner, Dept. of Physics & Astronomy, University of Kentucky
Permanent EDM searches and the theoretical landscape of CP violation
Meeting room 1, Kenkyu honkan 1F, slides (kek.jp only)
I will discuss the theoretical motivations for permanent EDM searches, as well as the theoretical interpretation of existing experimental limits in neutrons, atoms, and molecules, and I will examine how such limits combine to refine the possible TeV-scale landscape of CP violation from physics beyond the Standard Model.
甘利俊一, 理化学研究所
[第六回KEK連携コロキウム]人工知能の歴史、現状、将来: 付録ー統計神経力学の構想
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)
人工知能の時代がやってきて、社会構造や文明を変えるのではないかといわれている。人工知能は、人の知能をコンピュータ上に実現する構想から始まった。そこで、人の知能の源である脳の仕組みから初めて、人工知能の歴史を紐解く。そこには、記号と論理を使って知能を構築する流れと、ニューラルネットの学習機能を使って知能を構築する流れとがあった。いま、これが統合しようとしている。しかしまだ我々はその本質を理解できていない。ここが問題である。学術的な問題に加えて、脳における意識の機能、ロボットが心を持てるかなどといった、これからの社会にかかわる問題にも触れてみたい。さらに、最近の私の研究である深層回路の統計神経力学と学習について、構想を聞いていただきたい。
Takafumi Kokubu, KEK
Inhomogeneity Effect of Density Perturbations on Condition of Primordial Black Hole Formation
Meeting room 1, Kenkyu honkan 1F Condition for Primordial Black Hole (PBH) formation in matter dominated era including inhomogeneity effect is derived with treating general relativity. We investigate how the inhomogeneity of density perturbation affects the formation of PBHs. Black hole formation is determined by comparing two characteristic times, the formation time of the horizon and of the singularity. We investigate the threshold of the PBH formation by taking account of the speed of light propagating between the central singularity and the surface of a perturbation to be trapped.
Condition for Primordial Black Hole (PBH) formation in matter dominated era including inhomogeneity effect is derived with treating general relativity. We investigate how the inhomogeneity of density perturbation affects the formation of PBHs. Black hole formation is determined by comparing two characteristic times, the formation time of the horizon and of the singularity. We investigate the threshold of the PBH formation by taking account of the speed of light propagating between the central singularity and the surface of a perturbation to be trapped.
We report our analysis implies density perturbations with larger inhomogeneity would easily lead PBHs.
references:
[1] M. Y. Khlopov and A. G. Polnarev, Phys. Lett. 97B, 383 (1980).
[2] A. G. Polnarev and M. Y. Khlopov, Sov. Astronomy, 25, 406 (1981).
[3] T. Harada, C. M. Yoo, K. Kohri, K. i. Nakao and S. Jhingan,
Astrophys. J. 833, no. 1, 61 (2016).
Hiromasa Takaura, Kyushu University
Determination of αs from static QCD potential with renormalon subtraction
Meeting room 1, Kenkyu honkan 1F
The strong coupling constant α_s is a fundamental parameter in the standard model and requires to be determined with higher accuracy. We determine α_s from static QCD potential with a new method where a renormalon uncertainty, which is an inevitable error in perturbative predictions, is subtracted from a theoretical prediction. We obtain α_s(M_Z^2)=0.1178+0.0016/-0.0015, which is consistent with the PDG result.
Misao Sasaki, Kavli IPMU, The University of Tokyo
Scalaron as a Heavy Field and Formation of Primordial Black Holes
Meeting room 1, Kenkyu honkan 1F, slides (kek.jp only)
We propose a model of two-stage inflation in which a scalar field, χχ, is non-minimally coupled to Starobinsky’s R2R2 gravity. The scalaron, ϕϕ, in Starobinsky’ model drives the first stage of inflation, and χχ drives the second. At the end of the first stage, the scalaron becomes heavy and undergoes damped oscillations. This causes enhancement and oscillatory features in the curvature perturbation power spectrum. The peak in these features may give rise to copious production of primordial black holes (PBHs). For a suitably chosen set of model parameters, these PBHs may even dominate the CDM of the Universe.
Chen Zhang, National Center for Theoretical Sciences, Physics Division
Simplest Little Higgs Revisited: Hidden Mass Relation, Unitarity and Naturalness
Meeting room 1, Kenkyu honkan 1F
