Takashi Toma, Laboratoire de Physique Theorique d'Orsay
Electric Dipole Moments of Charged Leptons with Sterile Fermions
Seminar room, Kenkyu honkan 3F
We address the impact of sterile fermions on charged lepton electric dipole moments. In this work, we consider a minimal extension of the Standard Model via the addition of sterile fermions which mix with active neutrinos. Our study reveals that, in order to have a non-vanishing contribution in this framework, the minimal extension necessitates the addition of at least 2 sterile fermion states. Sterile neutrinos can give significant contributions to the charged lepton electric dipole moments if the masses of the non-degenerate sterile states are both above the electroweak scale. In addition, the Majorana nature of neutrinos is also important for the charged lepton electric dipole moments. Furthermore as a more concrete model, we consider the most minimal realisation of the Inverse Seesaw mechanism, in which the Standard Model is extended by two right-handed neutrinos and two sterile fermion states. Our study shows that the two pairs of (heavy) pseudo-Dirac mass eigenstates can give significant contributions to the electron electric dipole moment, lying close to future experimental sensitivity. In our analysis we further discuss the possibility of having a successful leptogenesis in this framework, compatible with a large electron electric dipole moment.
Masahiro Hotta, Tohoku University
Gravitational Memory Charges of Supertranslation and Superrotation on Rindler Horizons
Meeting room 1, kenkyu honkan 1F
In a Rindler-type coordinate system spanned in a region outside of a black hole horizon, we have nonvanishing classical holographic charges as soft hairs on the horizon for stationary black holes. Taking a large black hole mass limit, the spacetimes with the charges are described by asymptotic Rindler metrics. We construct a general theory of gravitational holographic charges for a 1+3-dimensional linearized gravity field in the Minkowski background with Rindler horizons. Although matter crossing a Rindler horizon causes horizon deformation and a time-dependent coordinate shift, that is, gravitational memory, the supertranslation and superrotation charges on the horizon can be defined during and after its passage through the horizon. It is generally proven that holographic states on the horizon cannot store any information about absorbed perturbative gravitational waves. However, matter crossing the horizon really excites holographic states. By using gravitational memory operators, which consist of the holographic charge operators, we suggest a resolution of the no-cloning paradox of quantum information between matter falling into the horizon and holographic charges on the horizon from the viewpoint of the contextuality of quantum measurement.
Koji Ichikawa, IPMU
Non-Sphericity/foreground effect on the dark matter halo estimation of dwarf spheroidal galaxies
Meeting room 3, Kenkyu honkan 1F
One of the most promising ways to detect dark matter is to look for its annihilation or decay products among cosmic-rays. Especially, it is found that quite strong constraints can be imposed by the gamma-ray measurements of dwarf spheroidal galaxies. However, recent studies reveal that these constraints are largely affected by the uncertainty of the dark matter halo density. In this talk, we will discuss the robustness of the dark matter halo estimation especially focusing on the effect of the non-sphericity and contamination of foreground stars.
Yohei Saito, Institute of Industrial Science, University of Tokyo
Discreteness-Induced Transition in Multi-body Reaction Systems
Meeting room 3, Kenkyu honkan 1F Qualitative change in dynamical behaviors due to finite system size attracts much attention in various interdisciplinary fields such as systems biology (stochastic chemical reactions), ecology (population dynamics), game theory, and social networks (agent dynamics). Actually, increase in multiplicative noise intensity due to smaller system size can induce qualitative transition of stationary distribution, which has been known as noise-induced transition since 1970s [1]. Although finite system size not only increases noise intensity but also emphasizes state space discreteness, the role of such discreteness of state space has been rarely studied [2]. Thus, we identify such discreteness-induced transition in a simple 1-and 3 body reaction system[3]. This model enables us to derive a sufficient condition under which the discreteness-induced transition arises. Furthermore, we find that the critical size of discreteness-induced transition can become quadratically large, if multi-body reactions are allowed.
Qualitative change in dynamical behaviors due to finite system size attracts much attention in various interdisciplinary fields such as systems biology (stochastic chemical reactions), ecology (population dynamics), game theory, and social networks (agent dynamics). Actually, increase in multiplicative noise intensity due to smaller system size can induce qualitative transition of stationary distribution, which has been known as noise-induced transition since 1970s [1]. Although finite system size not only increases noise intensity but also emphasizes state space discreteness, the role of such discreteness of state space has been rarely studied [2]. Thus, we identify such discreteness-induced transition in a simple 1-and 3 body reaction system[3]. This model enables us to derive a sufficient condition under which the discreteness-induced transition arises. Furthermore, we find that the critical size of discreteness-induced transition can become quadratically large, if multi-body reactions are allowed.
References:
[1] W. Horsthemke and R. Lefever, Noise-Induced Transitions in Physics, Chemistry, and Biology (Springer, 2006); J. Ohkubo, N. Shnerb, and D. A. Kessler, J. Phys. Soc. Jpn. 77 (2008); T. J. Kobayashi, Phys. Rev. Lett. 106, 228101 (2011).
[2] Y. Togashi and K. Kaneko, Phys. Rev. Lett. 86, 2459 (2001).
[3] Y. Saito, Y. Sughiyama, K. Kaneko and T. J. Kobayashi, arXiv:1605.06273.
Shoichiro Tsutsui, Kyoto University
Improvement in complex Langevin dynamics from a view point of Lefschetz thimble
Meeting room 1, Kenkyu honkan 1F We develop a way of improving complex Langevin dynamics motivated by the Lefschetz-thimble decomposition of integrals. In this talk, we consider the cosine model which has a global sign problem due to its multi-thimble structure. We show that the toy model can be modified so that the new model consists of a single Lefschetz thimble and the configurations sampled by the improved complex Langevin process are distributed around on the thimble.
We develop a way of improving complex Langevin dynamics motivated by the Lefschetz-thimble decomposition of integrals. In this talk, we consider the cosine model which has a global sign problem due to its multi-thimble structure. We show that the toy model can be modified so that the new model consists of a single Lefschetz thimble and the configurations sampled by the improved complex Langevin process are distributed around on the thimble.
Reference: S. T. and T. M. Doi, (arXiv:1508.04231) To be published in PRD.
Thorsten Feldmann, U Siegen
Combining Pati-Salam Grand Unification with Gauged Flavour Symmetries
Meeting room 1, Kenkyu honkan 1F
Starting with a general introduction to the flavour puzzle in the Standard Model (SM) and the flavour problem in generic new physics scenarios, I present a specific SM extension which is based on grand unification with Pati-Salam symmetry. The setup is supplemented with the idea of spontaneous flavour symmetry breaking which is mediated through flavon fields with renormalizable couplings to new heavy fermions. While new gauge bosons in this approach can be sufficiently heavy to be irrelevant at low energies, the fermionic partners of the SM fermions, in particular those for the third generation, can be relatively light and provide new sources of flavour violation. The size of the effects turns out to be constrained by the observed values of the SM Yukawa matrices, but in a way that is different from the standard minimal-flavour violation hypothesis. We determine characteristic deviations from the SM that could eventually be observed in future precision measurements in the quark and lepton sector.
Hiroyuki Shimizu, Kavli IPMU, University of Tokyo
Recent developments in 6d N=(1,0) SCFTs
Meeting room 1, Kenkyu honkan 1F, slides (kek.jp only) Recently, there is a huge amount of progress in the study of 6d N=(1,0) theories. We now have a better understanding of the landscape of such theories and have a general formula for their anomaly polynomials. For a large class of 6d (1,0) theories, we have 2d gauge theory descriptions of the worldsheet 2d (0,4) SCFTs on the BPS strings. The compactifications of 6d (1,0) theories are also being studied by many authors. In this talk, I’d like to explain such recent developments in 6d (1,0) theories, based on my works with collaborators.
Recently, there is a huge amount of progress in the study of 6d N=(1,0) theories. We now have a better understanding of the landscape of such theories and have a general formula for their anomaly polynomials. For a large class of 6d (1,0) theories, we have 2d gauge theory descriptions of the worldsheet 2d (0,4) SCFTs on the BPS strings. The compactifications of 6d (1,0) theories are also being studied by many authors. In this talk, I’d like to explain such recent developments in 6d (1,0) theories, based on my works with collaborators.
In the first part of the talk, I will review the basic ingredients of 6d (1,0) theories, such as moduli spaces of vacua, anomalies of global symmetries, and BPS strings on the tensor branch. I will also describe the string theory realizations of important examples of 6d (1,0) theories.
In the second part of the talk, I will explain the compactification of 6d (1,0) theories on a 2-torus as a first step toward considering more general backgrounds. I’d like to focus on the similarities and differences between 6d (1,0) theories and the 6d (2,0) theory under the compactification.
References: arXiv:1408.5572, 1503.06217 and 1508.00915 with K.Ohmori, Y.Tachikawa and K.Yonekura. arXiv:1608.05894 with Y.Tachikawa.
Kazunobu Maruyoshi, Seikei University
Infrared supersymmetry enhancement in 4d QFT
Meeting room 1, Kenkyu honkan 1F, slides (kek.jp only)
We study certain deformations of four-dimensional N=2 superconformal field theories (SCFTs) with non-abelian flavor symmetry which preserve an N=1 supersymmetry. The deformation is described by adding an N=1 chiral multiplet transforming in the adjoint representation of the flavor symmetry with a superpotential coupling, and giving a nilpotent vacuum expectation value to the chiral multiplet which breaks the flavor symmetry. This triggers a renormalization group flow to an infrared SCFT. Remarkably, we find that classes of theories flow to enhanced N=2 superconformal fixed points in the infrared under the deformation. For instance, the deformations of N=2 supersymmetric SU(N) QCD with 2N flavors and Sp(N) QCD with 2N+2 flavors flows to the (A_1, A_{2N-1}) and (A_1, A_{2N}) Argyres-Douglas theories respectively. From these “Lagrangian descriptions,” we compute the full superconformal indices of the (A_1,A_n) theories and find perfect agreements with the previous results in some limits. Other examples of the infrared supersymmetry enhancement include generalized Argyres-Douglas theories and rank-one SCFTs with non-abelian flavor symmetries. This talk is based on the collaborations with Jaewon Song and on the papers arXiv:1606.05632 and 1607.04281.
Takayuki Myo, Osaka Institute of Technology
Recent development of complex scaling method for many-body unbound states in light nuclei
Meeting room 1, Kenkyu honkan 1F Complex scaling method is one of the approaches to study the resonances in many-body quantum system and widely used in atomic and molecular physics, nuclear physics and hadron physics. For nuclear physics, in proton-rich and neutron-rich nuclei, most of the states are observed as unbound states owing to the weak binding nature of valence protons/neutrons. Complex scaling method becomes a powerful tool to investigate the properties of unbound states in those nuclei. We present the recent development of complex scaling method for the description of the many-body resonances and continuum states in light unstable nuclei.
Complex scaling method is one of the approaches to study the resonances in many-body quantum system and widely used in atomic and molecular physics, nuclear physics and hadron physics. For nuclear physics, in proton-rich and neutron-rich nuclei, most of the states are observed as unbound states owing to the weak binding nature of valence protons/neutrons. Complex scaling method becomes a powerful tool to investigate the properties of unbound states in those nuclei. We present the recent development of complex scaling method for the description of the many-body resonances and continuum states in light unstable nuclei.
The seminar consists of two parts as
1) Fundamental properties of the complex scaling method and its application to the many-body resonances decaying into the system of three-body and more, which are often seen in light unstable nuclei.
2) Application of the complex scaling method to the reaction phenomena with light unstable nuclei. In particular, we present the complex-scaled Green’s function method to obtain the cross sections. Green’s function is essential to evaluate the cross sections not only of resonances, but also of non-resonant continuum part individually. This decomposition of the cross section is useful to clarify the reaction mechanism in the connection with the role of resonances.
Morimichi Kawasaki, Institute of Basic Science, Korea
シンプレクティック・トポロジーと不確定性関係について
Seminar room, Kenkyu honkan 3F シンプレクティック幾何学は解析力学に起源をもつ非常に古い幾何学であるが、1985年のグロモフの有名な仕事以降、急速な発展を遂げていて、それを一部ではシンプレクティック・トポロジーと呼ぶ。 シンプレクティック・トポロジーと不確定性関係にはいくつかの関係が知られており、これについて概要を説明する。
