[geometry-ml:06489] Re: CREST seminars

[Yasuyuki Kawahigashi]

皆様，
次回11月7日の CREST オンラインセミナーは以下のようになります．Zoom 
リンクご希望の方は下記ページで登録をお願いします．(リンクは毎回同じですので登録済みの方は再登録は不要です．)
https://www.ms.u-tokyo.ac.jp/~yasuyuki/crest-seminar.htm
河東泰之
---
Speaker: Kenji Shimomura (YITP, Kyoto University)
Title: Nonequilibrium steady state in Lindblad dynamics for infinite 
quantum spin systems and nonnormality-induced spontaneous symmetry breaking
Date/Time: 16:00-17:30, Friday, November 7, 2025
Abstract: For open quantum systems obeying a Lindblad equation, it is a 
challenging problem to clarify and classify what kind of non-equilibrium 
steady state (NESS) the system relaxes to after a sufficiently long time. 
In this talk, we consider open quantum spin systems on infinite lattices 
described by the Lindblad equation and present a definition of the NESS in 
such infinite systems. The NESS in infinite systems is not necessarily 
equivalent to the thermodynamic limit of the NESS in finite systems; the 
former may correspond in finite systems to a metastable state, not a NESS. 
We see this in a solvable model. We also find a sufficient condition for 
equivalence of them, which relates to both the Liouvillian gap and 
nonnormality, i.e., nonorthogonality among eigenmodes of the Liouvillian. 
The enhancement of nonnormality can cause spontaneous symmetry breaking 
(SSB) for the NESS in infinite systems, which we dub nonnormality-induced 
SSB. Since a Liouvillian is normal in unitary dynamics, such a type of SSB 
is unique to open quantum systems. Furthermore, the nonnormality-induced 
SSB can occur even when the Liouvillian is gapped. This work uncovers a 
novel phase of matter in open quantum systems and establishes a way to 
classify it by focusing on nonnormality. This talk is based on the preprint 
arXiv:2508.07448.