Upcoming Seminars

Date/Place Jan. 22nd (Tue.) 15:30-16:30 / H711
Name Shinji Takeda (Kanazawa U.)
Title QCD phase diagram
Abstract It is known that the nature of finite temperature QCD phase transition depends on the number of quark flavors and quark masses. Such a situation is often pictorially summarized as the Columbia plot. There is an important and longstanding issue on the structure of the plot, namely the location of the critical line which separates the first order phase transition region from the cross-over region. In this talk, I will review and show some recent progresses on the issue by lattice QCD simulations. I will also address another issue how the Columbia plot is affected by the presence of finite quark density.


Date/Place Jan. 29th (Tue.) 15:30-16:30 / H711
Name Takahiro Sagawa (U. of Tokyo)
Title Unifying information scrambling with eigenstate thermalization: A partial unitary k-design approach
Abstract Recent studies have revealed that chaotic dynamics in quantum many-body systems leads to thermalization and information scrambling. The former is related to the eigenstate thermalization hypothesis (ETH), which states that all the energy eigenstates are locally indistinguishable from thermal equilibrium. The latter is quantified by the decay of an unconventional correlator, called the out-of-time-ordered correlator (OTOC). In this talk, we introduce our framework to give a unified view on these two notions [1]. Specifically, we introduce a higher-order generalization of the ETH, which we refer to as the k-ETH (k=1, 2, ...). From this perspective, the conventional ETH is regarded as the lowest order (1-ETH), and the decay of the OTOC corresponds to the second order (2-ETH). Furthermore, we introduce a quantum-information theoretic notion, named the partial unitary k-design, which characterizes the indistinguishability of Hamiltonian dynamics and ideally random dynamics (i.e., Haar random unitary). We show that the k-ETH is regarded as a special case of the partial unitary k-design, and the choices of norms to approximate it give the weak and strong versions of the ETH. [1] K. Kaneko, E. Iyoda, and T. Sagawa, in preparation.


Date/Place Apr. 9th (Tue.) 15:30-16:30 / H711
Name Yu Nakayama (Rikkyo U.)
Title TBA
Abstract TBA


Past Seminars