Kazushi Yamashiro, Shizuoka University
Target space entanglement in a matrix model for the bubbling geometry
Online (Zoom) https://kds.kek.jp/event/43729/
We study the target space entanglement entropy in a complex matrix model that describes the chiral primary sector in N=4super Yang-Mills theory, which is associated with the bubbling AdS geometry. The target space for the matrix model is a two-dimensional plane where the eigenvalues of the complex matrix distribute. The eigenvalues are regarded as the position coordinates of fermions, and the eigenvalue distribution can be viewed as a droplet formed by the fermions, which is identified with one that specifies a boundary condition in the bubbling geometry. We consider states in the matrix model that correspond to AdS5× S5, an AdS giant graviton and a giant graviton in the bubbling geometry. We calculate the target space entanglement entropy of a subregion for each of such states in the matrix model as well as the area of the boundary of the subregion in the bubbling geometry, and find a qualitative agreement between them.
Masaaki Tomii, Univ. of Connecticut
Lattice calculation of $K ¥to ¥pi¥pi$ decay on the lattice with periodic boundary conditions
Hybrid On-site: Kenkyu-Honkan Seminar room, Online: (Zoom) https://kds.kek.jp/event/43752/ Since RBC/UKQCD’s latest publication of lattice result for direct CP violation and the Delta I = 1/2 rule in $K ¥to ¥pi¥pi$ decay, which was made with G-parity boundary conditions in 2020, we have been revisiting this problem with a different lattice setup with periodic boundary conditions and multiple lattice spacings to see the consistency with our previous result and to improve the precision. While there was an expectation that it could be difficult to extract physical kinematics of K to pipi decay with periodic boundary conditions, we overcome it through the variational method. Also periodic boundary conditions provide a relatively easy way to introduce electromagnetic and isospin breaking corrections, which is desired to be implemented in near future.
Since RBC/UKQCD’s latest publication of lattice result for direct CP violation and the Delta I = 1/2 rule in $K ¥to ¥pi¥pi$ decay, which was made with G-parity boundary conditions in 2020, we have been revisiting this problem with a different lattice setup with periodic boundary conditions and multiple lattice spacings to see the consistency with our previous result and to improve the precision. While there was an expectation that it could be difficult to extract physical kinematics of K to pipi decay with periodic boundary conditions, we overcome it through the variational method. Also periodic boundary conditions provide a relatively easy way to introduce electromagnetic and isospin breaking corrections, which is desired to be implemented in near future.
In this talk, we show our preliminary result and discuss prospect of high-precision calculation of $K ¥to ¥pi¥pi$ decay with periodic boundary conditions.
Choong Sun Kim, Yonsei University
[EX] Is the sub-eV active neutrino Dirac or Majorana? (New alternative method to 0-nu-beta-beta decay, by using B^0 (or Upsiol(1s)) --> mu+ mu- nu nu-bar)
Online (Zoom) https://kds.kek.jp/event/43753/
The nature of neutrino, whether it is a Dirac type or Majorana type, may be comprehensively probed using their quantum statistical properties. If neutrino is a Majorana fermion, then by definition it is identical and indistinguishable from the corresponding antineutrino. When a Majorana neutrino and antineutrino are pair produced, the corresponding state has to obey Pauli principle unlike in the Dirac case. We use this property to distinguish between the two cases using the process B^0 → µ− µ+ νµ ¯νµ. We show that the two cases differ dramatically in a special kinematic scenario where, in the rest frame of the parent B meson, the muons fly away back-to-back (i.e. fly with 3-momenta of equal magnitudes but opposite directions), and so do the neutrino and antineutrino.
Kei-ichi Maeda, Waseda University
Relativistic Dynamical System and Gravitational Waves
Hybrid On-site: Kenkyu-Honkan Seminar room, Online: (Zoom) https://kds.kek.jp/event/43754/ After the discovery of the gravitational waves, gravitational wave physics and astronomy have provided us new information about strong gravitational phenomena and new physics. For example, speed of gravitational waves, equation of state at very high dense region, constraint on gravitational theories, and so on.
After the discovery of the gravitational waves, gravitational wave physics and astronomy have provided us new information about strong gravitational phenomena and new physics. For example, speed of gravitational waves, equation of state at very high dense region, constraint on gravitational theories, and so on.
In order to observe gravitational waves, we have used the templates of emitted gravitational waves from a binary system. However, we may have more complicated relativistic dynamical system in nature, which may not be integrable. We may expect chaotic behavior in such a system, for which it is very difficult to make appropriate templates.
In this talk, we study chaos in a relativistic dynamical system of compact objects and the gravitational waves emitted from such a system. We then look for some characteristic feature of the gravitational waves, which could be used in gravitational wave observation.
We also discuss about a hierarchical triple system with the Kozai-Lidov mechanism, which shows the oscillation between the eccentricity of inner binary and relative inclination. The evolution curve of the cumulative perihelion shift, which is indirect evidence of gravitational wave emission, will be bended since the gravitational waves are emitted strongly when the eccentricity becomes large. We then show the observability of gravitational waves from such a triple system. We also consider relativistic effects such as Lense-Thirring precession.
Hikaru Kawai, National Taiwan University
Do different observers see different physics?
Hybrid On-site: Kenkyu Honkan Seminar room, Online: (Zoom) https://kds.kek.jp/event/43755/
Considering a system of particles in a gravitational field for example, in classical mechanics, there is naturally a one-to-one correspondence between the motion observed by an freely falling observer and the motion observed by a distant observer. However, in quantum mechanics, a “good wave packet” whose position and velocity are relatively well determined for one observer is not necessarily a “good wave packet” for another observer, which means the above one-to-one correspondence no longer exists. We will argue that such deviations can be significantly large when non-renormalizable interactions, or interactions that becomes strong at the Planck scale, such as gravity, are taken into account.
Po-Yen Tseng, National Tsing Hua University
Correlated signals of first-order phase transition in the dark sector
Hybrid style On-site: Kenkyu Honkan Seminar room, Online: (Zoom) https://kds.kek.jp/event/43756/
Fermion dark matter particles can aggregate to form extended dark matter structures via a first-order phase transition in which the particles get trapped in the false vacuum. We study Fermi balls created in a phase transition induced by a generic quartic thermal effective potential. We show that for Fermi balls of mass, $10^{-7}M_{Sun} M_{¥rm FB} < 10^{-5}M _{Sun}$, correlated observations of gravitational waves produced during the phase transition (at SKA/THEIA/$¥mu$Ares), and gravitational microlensing caused by Fermi balls (at Subaru-HSC), can be made if the amount of dark radiation today is smaller than the equivalent of one neutrino. Fermi balls may collapse to primordial black holes (PBHs) if the fermion dark matter particles that comprise them interact via a sufficiently strong Yukawa force. We show that phase transitions with vacuum energy, $0.1 < B^{1/4}/{MeV} < 10^3$}, generate PBHs of mass, $10^{-20} < M_{PBH} /M_{Sun} < 10^{-16}$, and correlated isotropic extragalactic X-ray/$¥ gamma$-ray background from PBH evaporation (at AMEGO-X/e-ASTROGAM).
Muneto Nitta, Keio University
Relations among topological solitons
Online (Zoom) https://kds.kek.jp/event/43757/ We clarify relations among topological solitons in various dimensions: a domain wall, non-Abelian vortex, magnetic monopole, and Yang-Mills instanton, together with a (non-Abelian) sine-Gordon soliton, baby skyrmion (lump), and skyrmion. We construct a composite configuration consisting of a domain wall, vortex, magnetic monopole, and Yang-Mills instanton (wall-vortex-monopole-instanton) using the effective theory technique or moduli approximation. Removing some solitons from such a composite, we obtain all possible composite solitons in the form of solitons within a soliton, including all the previously known configurations, yielding relations among topological solitons.
We clarify relations among topological solitons in various dimensions: a domain wall, non-Abelian vortex, magnetic monopole, and Yang-Mills instanton, together with a (non-Abelian) sine-Gordon soliton, baby skyrmion (lump), and skyrmion. We construct a composite configuration consisting of a domain wall, vortex, magnetic monopole, and Yang-Mills instanton (wall-vortex-monopole-instanton) using the effective theory technique or moduli approximation. Removing some solitons from such a composite, we obtain all possible composite solitons in the form of solitons within a soliton, including all the previously known configurations, yielding relations among topological solitons.
This talk is based on Phys.Rev.D 105 (2022) 10, 105006, e-Print: 2202.
03929 [hep-th].
Misao Sasaki, Kavli IPMU, University of Tokyo
Multiple classical histories as a solution to the black hole information loss paradox
Online (Zoom) https://kds.kek.jp/event/43758/
The information loss paradox associated with black hole evaporation is an unresolved problem in modern theoretical physics. We consider the evolution of the black hole entanglement entropy via the Euclidean path integral of the quantum state under the semi-classical approximation. We argue that there exist Euclidean instantons that mediate the tunneling from a black hole geometry to a trivial geometry where all the black hole mass is carried away as radiation. By taking into account the multiple classical histories resulting from the tunneling, we recover the Page curve for the entanglement entropy, albeit being modified, with its maximum largely exceeding the Bekenstein-Hawking bound.
Yosio Kikukawa, University of Tokyo
Two approaches to non-abelian chiral gauge theory on the lattice with exact gauge invariance
Online (Zoom) https://kds.kek.jp/event/43759/ We discuss how to construct non-abelian chiral gauge theories with anomaly-free multiplets of Weyl fermions on the lattice without breaking the gauge invariance or violating any other fundamental principle. There are two approaches for this purpose:
We discuss how to construct non-abelian chiral gauge theories with anomaly-free multiplets of Weyl fermions on the lattice without breaking the gauge invariance or violating any other fundamental principle. There are two approaches for this purpose:
1.To establish the integrability condition for the chiral determinant of overlap Weyl fermions
2.To gap out the mirror degrees of freedom of overlap Dirac fermions (Domain-wall fermions) with certain (boundary) interaction terms
In the former case, the integrability condition for the chiral determinant of overlap Weyl fermions can be formulated with five-, and six-dimensional lattice Domain-wall fermions. This formulation of the integrability condition is in parallel to the recent cobordism classification of global ‘t Hooft anomaly with the η-invariant based on the Dai-Freed theorem and the APS index theorem in the continuum theory. In the latter case, the required condition for the interaction terms is given by the complete cancellation of ‘t Hooft anomalies. We discuss the recent results on these two approaches.
Nobuyuki Matsumoto, Riken BNL Research Center
Comment on the subtlety of defining real-time path integral in lattice gauge theories
Online (Zoom) https://kds.kek.jp/event/43760/ Recently, Hoshina, Fujii, and Kikukawa [1] pointed out that the naive lattice gauge theory action in Minkowski signature does not result in a unitary theory in the continuum limit, and Kanwar and Wagman [2] proposed alternative lattice actions to the Wilson action without divergences. We here show that the subtlety can be understood from the asymptotic expansion of the modified Bessel function, which has been discussed for path integral of compact variables in nonrelativistic quantum mechanics [3,4]. The essential ingredient for defining the appropriate continuum theory is the iε prescription, which we show is applicable also for the Wilson action. It is here important that the iε should be implemented for both timelike and spacelike plaquettes. We then argue that such iε can be given a physical meaning that they remove singular paths having nontrivial winding for an infinitesimal time evolution that do not have corresponding paths in the continuum. Such point of view is only apparent in systems with compact variables as lattice gauge theories. This talk is based on [5].
