Yuji Chinone, RESCEU, U of Tokyo
The results and achievements of the POLARBEAR experiment in the 2010s and its future in the 2020s
Online (Zoom) https://kds.kek.jp/indico/event/35385/
POLARBEAR is a ground-based experiment designed to measure polarization of the Cosmic Microwave Background (CMB) at 150 GHz at an elevation of 5,190m in the Atacama Desert in Chile. Our main science goals are for searching for the B-mode signal created by primordial gravitational waves (PGWs) seen at degree scales, as well as for characterizing the B-mode signal from gravitational lensing with high angular resolution seen at sub-degree scales. POLARBEAR was deployed in 2011 and started science observations in 2012 focusing on small patches of the sky (deep survey). In 2014, we started to observe a large patch of the sky focusing on search for PGWs (wide survey). We have published a series of results from the deep survey, including the first/update measurement of a non-zero B-mode auto-power spectrum at sub-degree scales induced by gravitational lensing, constraint of cosmic birefringence and primordial magnetic fields, and demonstration of delensing. We also have achieved the measurement of cross-correlations of gravitational lensing between our CMB data and optical surveys by the Subaru Hyper Suprime-Cam. With the wide survey, we have reported the measurement of large angular scale B-mode signals induced by the Galactic dust foreground and successfully put an upper limit on PGWs. In this talk, I summarize the science results and achievements of the POLARBEAR experiment. I also show the status of Simons Array, which is an upgraded experiment from POLARBEAR and consists of three new receivers. Finally I describe future CMB projects which Japanese institutes have been contributing to.
Masahiro Isaka, Hosei University
Low-lying level structure of p-sd shell Lambda hypernuclei with antisymmetrized molecular dynamics
Online (Zoom), indico page, slides (kek.jp only)
We focus on low-lying level structure such as ΛΛN spin-spin and spin-orbit splittings in excitation spectra of p-sd shell Lambda hypernuclei. One of the major goals of hypernuclear physics is to understand properties of the baryon-baryon interaction including hyperon(s). Another important issue is to clarify dynamics of baryon many-body systems. In the last decades, by the developments of the experimental studies, the low-lying level structure of light ΛΛ hypernuclei has been revealed precisely. It is expected that crucial information on both properties of ΛΛN interaction and hypernuclear structure from the low-lying level structure. In this study, we use the antisymmetrized molecular dynamics with the ΛΛN G-matrix interaction derived from the baryon-baryon interaction model ESC. It is found that the ground-state spin-parity is systematically reproduced in the p-shell ΛΛ hypernuclei by tuning the ΛΛN spin-spin and spin-orbit interactions so as to reproduce the experimental data of 4ΛΛ4H, 7ΛΛ7Li, and 9ΛΛ9Be. Furthermore, it is found that the energy spacing of the ground-state doublet in 19ΛΛ19F is successfully reproduced using the same ΛΛN interaction. We also focus on the excitation energies and energy shifts of the excited doublets by the addition of a ΛΛ particle. In this talk, we will discuss how the spin-dependent properties of the ΛΛN interactions and structure of the core nuclei affect the low-lying spectra of the ΛΛ hypernucle
Masaki Yamada, Tohoku University
Unified Origin of Axion and Monopole Dark Matter, and Solution to the Domain-wall Problem
Online (Zoom) https://kds.kek.jp/indico/event/35279/
A ‘t Hooft-Polyakov monopole in a dark sector is a viable dark-matter candidate as it is stable due to its topological charge. If the spontaneous symmetry breaking proceeds via the first order phase transition, monopoles can be produced from the collisions of expanding bubbles. In the case with a Coleman-Weinberg potential, a monopole with mass of O(10^{10}) GeV can explain the observed DM density. Interestingly, this is within a viable window for the PQ-symmetry breaking. Motivated by the coincidence of the energy scales, we have pursued a possibility of unifying the PQ symmetry breaking and the production of the monopole DM. Even simple models lead to interesting phenomena in cosmological history, like the Witten effect on the axion in the presence of the monopoles, the Lazarides-Shafi mechanism to avoid the domain wall problem, and the formation of Alice strings. I will explain these effects in a KSVZ-type axion model as well as a DFSZ-type axion model and will show how the cosmological domain wall problem of the axion models is avoided by these effects.
Yasuro Funaki, Kanto Gakuin University
Alpha-particle condensate and cluster evolution in nuclei
Online (Zoom), indico page, slides (kek.jp only)
Nuclear cluster dynamics is reviewed from its historical point of view to a new aspect developed recently. After a great success of the model wave function of alpha-particle condensation is explained, the picture of alpha condensation is extended to a general concept of nonlocalized clustering, which is applicable to promisingly all the cluster structures. The competition between the localized and nonlocalized cluster motions is discussed in terms of the inter-cluster Pauli repulsion and dynamical character contained in a new wave function proposed recently. It is also shown that the path of cluster evolution, which is indicated by the Ikeda diagram, can be described by the evolution of a “container”, which plays a role in trapping the constituent clusters in a flexible way.
Yuko Urakawa, Bielefeld University
Anisotropic separate Universe
Online (Zoom)
The essence of the separate Universe approach, which has been widely used in cosmology, is to rephrase an inhomogeneous Universe with glued numerous homogeneous local patches. We show that the separate Universe approach can be generically used, as long as a theory under consideration is local and preserves the spatial diffeomorphism invariance. Remarkably, the separate Universe approach and subsequently the $¥delta N$ formalism can also apply to a Universe with large scale anisotropic pressure and also to modified theories of gravity, accepting a violation of Lorentz invariance. We also show that the same condition ensures the approximate existence of Weinberg’s adiabatic mode, the constant solution of the curvature perturbation.
Koichi Hattori, YITP, Kyoto
Transport phenomena in magnetic and vortical fields from hydrodynamic frameworks
Online (Zoom), indico page, slides (kek.jp only)
I will discuss recent formulation of the relativistic magnetohydrodynamics on the basis of the magnetic (one-form) symmetry inherent in QED. I will then cover some related topics such as an unstable helical magnetohydrodynamic mode induced by the chiral anomaly and “spin hydrodynamics” in the presence of fluid vorticity.
Yasunori Nomura, BCTP, U. of California, Berkeley
Black Hole Conundrum: Information vs Interior
Online (Zoom) https://kds.kek.jp/indico/event/35124/
Studying the thermodynamic aspect of a black hole, including its apparent contradiction with the principles of quantum mechanics, has been driving our understanding of spacetime and gravity at the fundamental level. While we have found that the principles of quantum mechanics prevail in the end, paradoxes still remain; the latest form of these is the difficulty of reconciling unitary evolution of a black hole with the existence of its interior, often called the firewall paradox. I will discuss how this conundrum can be solved by carefully analyzing the degrees of freedom associated with the black hole, which I refer to as hard modes, soft modes, and far modes (early radiation). The resulting picture reveals an intriguing relation between the chaotic behavior of the UV dynamics near the horizon and the IR aspect of emergent spacetime inside the horizon. It also elucidates what the semiclassical description of spacetime and gravity really is. This talk is based on the work presented in arXiv:1810.09453, 1908.05728, and 1911.13120.
Shi Chen, University of Tokyo
[QCD theory seminar] Deconfinement and CP-breaking at θ=π in a softly-broken N=1 SYM
Online (Zoom)
At θ=π in pure Yang-Mills theories, the CP-symmetry is spontaneously broken in the confined phase, justified by an ‘t Hooft anomaly between center symmetry and CP-symmetry. In this talk, we want to see when the deconfinement phase transition occurs, whether CP-symmetry is restored at the same time. We deform the pure Yang-Mills theory to a softly-broken N=1 Super Yang-Mills theory (SYM). In this softly-broken SYM, both deconfinement and CP-restoration can occur in the weakly-coupled region where reliable evaluations can be made. We will show that for gauge groups other than SU(2), these two transitions occur synchronously. For SU(2), the CP-restoration occurs strictly later than the deconfinement, and a CP-breaking deconfined phase appears between the two transitions.
Yoshihisa Kitazawa, KEK
Why now? A History of Dark Energy (in Japanese)
Online (Zoom) https://kds.kek.jp/indico/event/35122/ We investigate the reheating process by the gluon pair productions through QCD trace anomaly. Energy densities of inflaton efficiently transferred into thermal radiation. We identify the conformal zero mode as inflaton The potential energy of inflaton is dark energy.
We investigate the reheating process by the gluon pair productions through QCD trace anomaly. Energy densities of inflaton efficiently transferred into thermal radiation. We identify the conformal zero mode as inflaton The potential energy of inflaton is dark energy.
We argue dark energy decays rapidly by gluon pair emission during reheating and even after the big bang. The reheating temperature is determined by the decay width ¥sqrt{M_p ¥Gamma} as 10^6 GeV. As the Universe cools below the hadronic scale, dark energy density is almost frozen. The energy density of dark energy still decreases by emitting two photons through QED trace anomaly. We can estimate the magnitude of dark energy from the QED decay width ¥sqrt{M_p ¥Delta} ¥sim eV. We have come a long way to give the upper bound on the present magnitude of dark energy as (10^{-2.5} eV)^4.
Kazushi Yamashiro, Shizuoka University
Information geometry encoded in bulk geometry (in Japanese)
Online (Zoom), indico page, slides (kek.jp only)
