Upcoming Seminars

Date/Place Jan. 25th (Tues.) (Informal) 13:30-14:30 / H711
Name Sotaro Sugishita (Osaka Univ.)
Title Soft pion theorem, asymptotic symmetry and new memory effect
Abstract It is known that soft photon and graviton theorems can be regarded as the Ward-Takahashi identities of asymptotic symmetries. In this work, we consider soft theorem for pions, i.e., Nambu-Goldstone bosons associated with a spontaneously broken axial symmetry. The soft pion theorem is written as the Ward-Takahashi identities of the S-matrix under asymptotic transformations. We investigate the asymptotic dynamics, and find that the conservation of charges generating the asymptotic transformations can be interpreted as a pion memory effect.

 

Date/Place Jan. 30th (Tues.) 15:30-16:30 / H711
Name Keiju Murata (Osaka Univ.)
Title Fast scrambling in holographic Einstein-Podolsky-Rosen pair
Abstract We demonstrate that a holographic model of the Einstein-Podolsky-Rosen pair exhibits fast scrambling. Strongly entangled quark and antiquark in $N=4$ super Yang-Mills theory are considered. Their gravity dual is a fundamental string whose endpoints are uniformly accelerated in opposite direction. We slightly increase the acceleration of the endpoint and show that it quickly destroys the correlation between the quark and antiquark. The proper time scale of the destruction is $\tau_\ast\sim \beta \ln S$ where $\beta$ is the inverse Unruh temperature and $S$ is the entropy of the accelerating quark. We also evaluate the Lyapunov exponent from correlation function as $\lambda_L=2\pi/\beta$, which saturates the Lyapunov bound. Our results suggest that the fast scrambling or saturation of the Lyapunov bound do not directly imply the existence of an Einstein dual. When we slightly decrease the acceleration, the quark and antiquark are causally connected and an ``one-way traversable wormhole'' is created on the worldsheet. It causes the divergence of the correlation function between the quark and antiquark.

 

Date/Place Jan. 29th (Mon.) (Informal) 16:00-17:00 / H711
Name Yu Muramatsu (KIAS)
Title Nucleon decay to test GUT models
Abstract Supersymmeteric grand unified theory (SUSY GUT) is one of the most attractive candidate for the theory beyond the standard model. Because it can unify the three gauge interactions into a single gauge interaction naturally besides quarks and leptons into fewer multiplets. On the other hand, SUSY GUT models have some open questions: What is the unification group?, What kind of structure is suitable to break the unification group?, Which diagonalizing matrices should be large mixing matrix?, and so on. It is hard to answer these questions because phenomenology to test GUT models are limited. The nucleon decay: not only proton but also neutron baryon-number violating decay plays an important role to test SUSY GUT model. We discuss that what kind of hint we can get to solve these open questions if we find nucleon decay signal. Especially, in this seminar we focus on the diagonalizing matrices and recent nucleon decay event candidates at the super-Kamiokande.

 

Date/Place March 1st (Thu.) (Informal) 15:30-16:30 / H711
Name Shimada Kengo (EPFL)
Title Cosmological implications of quantum scale invariance
Abstract We study cosmology in scale invariant models with renormalization prescription preserving the scale invariance even at quantum level. Such models are known to be non-renormalizable and hence interpreted as effective field theory. The associated cut-off scale is evaluated and we argue that it can be high enough to justify the usual perturbative computation of effective potential. However the resultant potential is still scale invariant with some non-polynomial corrections. We apply it to a realistic model including the standard model fields and discuss how it impacts on the thermal history.

 

Past Seminars