スピン系の相転移・臨界現象
,非平衡定常系の熱力学の構築
,量子統計力学の基礎づけ
,強相関電子系における強磁性の起源
,量子多体系
,数理物理学
,phase transition and critical phenomena in spin systems
,construction of thermodynamics for nonequilibrium steady state
,foundation of quantum statistical mechanics
,origin of ferromagnetism in strongly interacting electron systems
,quantum many-body systems
,mathematical physics
We prove two theorems concerning the time evolution in general isolated quantum systems. The theorems are relevant to the issue of the time scale in the approach to equilibrium. The first theorem shows that there can be pathological situations in ...
In a system of interacting f = 1 bosons (in the subspace where the total spin in the z direction is vanishing), we prove inequalities for the ground state expectation value of the density of spin-0 bosons. The inequalities imply that the ground st...
We prove basic theorems about the ground states of the S = 1 Bose-Hubbard model. The results are quite universal and depend only on the coefficient U-2 of the spin-dependent interaction. We show that the ground state exhibits saturated ferromagnet...
JOURNAL OF STATISTICAL PHYSICS 145(5) 1275-1290 2011年12月
Recently, in their attempt to construct steady state thermodynamics (SST), Komatsu, Nakagawa, Sasa, and Tasaki found an extension of the Clausius relation to nonequilibrium steady states in classical stochastic processes. Here we derive a quantum ...
JOURNAL OF STATISTICAL PHYSICS 143(1) 1-10 2011年4月
We consider a (small) quantum mechanical system which is operated by an external agent, who changes the Hamiltonian of the system according to a fixed scenario. In particular we assume that the agent (who may be called a demon) performs measuremen...