Han Yan, OIST
Hyperbolic fracton model, subsystem symmetry, and holography
Seminar room, Kenkyu honkan 3F
We propose that the fracton models with subsystem symmetry can be a class of toy models for the holographic principle. The discovery of the anti–de Sitter/conformal field theory correspondence as a concrete construction of holography and the subsequent developments including the subregion duality and Ryu-Takayanagi formula of entanglement entropy have revolutionized our understanding of quantum gravity and provided powerful tool sets for solving various strongly coupled quantum field theory problems. To resolve many mysteries of holography, toy models can be very helpful. One example is the holographic tensor networks, which illuminate the quantum-error-correcting properties of gravity in the anti–de Sitter space. In this work we discuss a classical toy model featuring subsystem symmetries and immobile fracton excitations. We show that such a model defined on the hyperbolic lattice satisfies some key properties of the holographic correspondence. The correct subregion duality and Ryu-Takayanagi formula for mutual information are established for a connected boundary region. A naively defined black hole’s entropy scales as its horizon area. We also present discussions on corrections for more complicated boundary subregions, the possible generalizations of the model, and a comparison with the holographic tensor networks.
Kenji Toma, Frontier Research Institute for Interdisciplinary Sciences, Tohoku University
Theoretical Interpretation of the M87 black hole shadow imaged by EHT
Seminar room, Kenkyu honkan 3F
The Event Horizon Telescope (EHT) observed the central compact radio source of the elliptical galaxy M87 at 1.3mm with unprecedented angular resolution, and on April 10, 2019, the EHT Collaboration reported the asymmetric ring-like image reconstructed from the data. We generated a theoretical model image library of magnetohydrodynamic simulations and photon ray tracing calculations in the steady rotating black hole spacetime with broad ranges of parameter values to compare the observed data with the models. As a result, we confirmed that the asymmetric ring is consistent with strong gravitational lensing and Doppler beaming of synchrotron emission from a hot plasma orbiting near the supermassive black hole event horizon. In this seminar, we mainly review our theoretical interpretation, shown in the EHT Collaboration paper v. This time EHT did not have sufficient number of stations for detecting extended emission component such as the jet and accretion flow. We try to discuss how to identify the driving mechanism of the jet in M87 with next EHT observations.
Hiroshi Isono, Department of Physics, Faculty of Science, Chulalongkorn University
A microscopic model for inflation from supersymmetry breaking
Seminar room, Kenkyu honkan 3F
In this talk, I first introduce our recent proposal of a class of small-field inflation models driven by supersymmetry breaking. The inflaton is a superpartner of the goldstino of the supersymmetry breaking, and charged under a gauged U(1) R transformation. The models in this class has a linear superpotential, leading to avoiding the eta problem. Furthermore, the gauged U(1) R invariance makes the pseudo-scalar companion of the inflaton absorbed into the U(1) R gauge field, and also allows for a global minimum with tuneable cosmological constant. I introduce a concrete model in this class as an effective field theory, and propose a generalisation of Fayet-Iliopoulos model in supergravity as a microscopic model leading to this effective theory.
Hisashi Okui, Niigata University
Tomography by neutrino pair beam
Seminar room, Kenkyu honkan 3F, slides (kek.jp only)
Neutrino Tomography is an application of the particle physics to other science. The idea of neutrino tomography is imaging the interior structure of the Earth by using neutrinos. We consider the tomography method using neutrino oscillation. Neutrino oscillation probability is distorted by matter effect, and we reconstruct the matter density distribution that neutrinos passed through from the distortion. We assume the neutrino pair beam which has recently been proposed as an attractive neutrino source. The beam produces a large amount of neutrino and antineutrino pairs from the circulating partially stripped ions and provides the possibility to measure the energy spectrum of oscillation probability very precisely, together with a sufficiently large detector. In addition, we present a method to reconstruct a matter density profile by means of the analytic formula of the oscillation probability in which the matter effect is included perturbatively to the second order.
小林研介, 東大・阪大
[9th KEK joint colloquium] ゆらぎで探る量子液体
Seminar hall 4 go-kan / Room 116 1 go-kan Tokai campus（TV link） 半導体や金属を微細加工して作られる微小な固体素子をメゾスコピック系と呼ぶ。
半導体や金属を微細加工して作られる微小な固体素子をメゾスコピック系と呼ぶ。
その最大の特長は、量子効果が本質的なスケールにおいて、磁場や電場などの外場を利用することで、制御性の高い精密な実験が可能となる点にある。
たとえば、電子干渉計や人工原子等で発現するコヒーレンス・スピン・多体効果に依存する伝導の研究は、物性物理学の発展に大きな貢献を果たしてきた。
これまで、メゾスコピック系における実験研究の多くは、系の電気伝導度測定を主体とするものであった。しかし、近年、非平衡状態の動的な情報を得る手段として、電流ゆらぎ（電流雑音）測定が大きな関心を集めている[１]。本講演では、まず、メゾスコピック系と電流ゆらぎについて紹介する。さらに、近藤効果によって、人工原子に形成された量子液体のゆらぎについて、議論する[２−５]。
[１]K. Kobayashi, Proc. Jpn. Acad., Ser. B 92, 204 (2016).
[２]Y. Yamauchi et al., Phys. Rev. Lett. 106, 176601 (2011).
[３]M. Ferrier et al., Nature Phys. 12, 230 (2016).
[４] M. Ferrier et al., Phys. Rev. Lett. 118, 196803 (2017).
[５]T. Hata et al., Phys. Rev. Lett. 121, 247703 (2018).
岡本亮, 京都大学
量子系の時間発展と弱値
Meeting room 3, Kenkyu honkan 1F
量子系では，「観測」がその後の量子状態の時間発展に大きな影響を及ぼす．例えば，ある時刻に，光子の位置の射影測定を行った場合，その後の光子の位置の時間発展は，測定を行わなかった場合と大きく異なってしまう．同様に，光子の位置の射影測定を行った後，運動量の射影測定を行ったとしても，位置測定以前の運動量の正確な情報を得ることはできない．従って，射影測定を用いて，光子が辿る軌跡を問うこと無意味である．一方，射影測定ではなく，「弱測定」と呼ばれる測定手法，および弱測定結果から得られる「弱値」を用いると，この問いに答えることができる．例えば，トロント大学の研究グループは，2重スリットの実験において，弱測定を用いることで，光子の軌跡を記録することに成功している．また，位置と運動量のような，非可換な観測量の同時測定が，連続的な弱測定によって実現されている．これにより，パラドキシカルな弱値の間の関係性といった従来アクセスできなかった情報を得ることが可能になっている．本講演では，時間発展する量子系の弱値について，光子を用いた実験を軸に概観するとともに，最近の我々の研究結果について紹介する．
Yusuke Yamada, Research center for the early universe (RESCEU), University of Tokyo
Nonlinear realization in supergravity and its application
Meeting room 3, Kenkyu honkan 1F
Spontaneously broken supersymmetry plays important roles in supergravity model buildings. Below the supersymmetry breaking scale, the effective theory is well described by nonlinear realizations of supergravity. We show two applications of nonlinearly realized supergravity: One is the effective action of anti-D3 brane in KKLT background. The KKLT model is well known as the string realization of de Sitter vacua. The anti-D3 brane plays an important role in uplifting the vacuum. We show that the world volume fields on anti-D3 brane and their couplings are described in terms of the constrained superfields (nonlinear realizations). Secondly, we show that the nonlinear realization is useful to realize non-supersymmetric models within supergravity. As an example, we show the embedding of the Horndeski model into supergravity, which describes the most general ghost-free scalar-tensor system.
Takumi Doi, RIKEN Nishina Center for Accelerator-Based Science
Nuclear Physics from Lattice QCD
Meeting Room 1, Kenkyu honkan 1F
One of the most fundamental questions in nuclear physics is how nuclear physics itself emerges from the underlying theory, quantum chromodynamics (QCD), and the determination of baryon forces from QCD plays a crucial role to answer this question. In this talk, I review the first-principles lattice QCD calculation of baryon forces as well as general hadron-hadron interactions. I introduce a novel theoretical framework, HAL QCD method, and present the latest lattice QCD results, in particular, those obtained near the physical point. The physical implications for exotic dibaryons, equation of state of high dense matter and the structure of neutron stars are also discussed and future prospects will be given.
Sota Nakajima, Osaka City University
Exponentially suppressed cosmological constant with enhanced gauge symmetry in heterotic interpolating models
Meeting room 1, Kenkyu honkan 1F
An interpolating model is a (D－ d)-dimensional string model that continuously relates two D-dimensional string models. A few nine-dimensional interpolating models with two parameters are constructed and the massless spectra are studied by considering compactification of heterotic strings on a twisted circle with Wilson line. It is found that there are some conditions between radius R and Wilson line A under which the gauge symmetry is enhanced. In particular, when the gauge symmetry is enhanced to SO(18) \times SO(14), the cosmological constant is exponentially suppressed. We also construct a non-supersymmetric string model which is tachyon-free in all regions of moduli space and whose gauge symmetry involves E_8. This talk will be based on the work with H. Itoyama, arXiv: 1905.10745.
小川和久, 北海道大学
プローブを用いない弱値の直接測定法
Seminar room, Kenkyu honkan 3F
