585 citations · 1.1k across the 46 of their papers we have counts for
6 papers · 1 filter
Proof of the absence of long-range temporal orders in Gibbs states
Haruki Watanabe, Masaki Oshikawa, Tohru Koma
We address the question whether time translation symmetry can be spontaneously broken in a quantum many-body system. One way of detecting such a symmetry breaking is to examine the…
Scattering of Conduction Electrons by a Ferromagnetic Domain Wall
Masanori Yamanaka, Tohru Koma
We study the scattering of an electron by a ferromagnetic domain wall of the quantum Heisenberg-Ising model (XXZ model) with certain boundary conditions. The spin of the electron i…
Decay of Superconducting and Magnetic Correlations in One- and Two-Dimensional Hubbard Models
Tohru Koma, Hal Tasaki
In a general class of one and two dimensional Hubbard models, we prove upper bounds for the two-point correlation functions at finite temperatures for electrons, for electron pairs…
The complete set of ground states of the ferromagnetic XXZ chains
Tohru Koma, Bruno Nachtergaele
We show that the well-known translation invariant ground states and the recently discovered kink and antikink ground states are the complete set of pure infinite-volume ground stat…
Symmetry Breaking and Finite Size Effects in Quantum Many-Body Systems
Tohru Koma, Hal Tasaki
We consider a quantum many-body system on a lattice with a continuous symmetry which exhibits a spontaneous symmetry breaking in its infinite volume ground states, but in which the…
Classical XY Model in 1.99 Dimensions
Tohru Koma, Hal Tasaki
We consider the classical XY model (O(2) nonlinear sigma-model) on a class of lattices with the (fractal) dimensions 1<D<2. The Berezinskii's harmonic approximation suggests that t…