17 citations · 74 across the 14 of their papers we have counts for
6 papers · 1 filter
Exponential decay in -invariant quantum spin systems
Jakob E. Björnberg, Kieran Ryan
We consider -invariant and reflection-positive quantum spin systems on the integer lattice in any dimension, and prove that spin-spin correlations decay exponentially fast pr…
Reflection positivity and infrared bounds for quantum spin systems
Jakob E. Björnberg, Daniel Ueltschi
The method of reflection positivity and infrared bounds allows to prove the occurrence of phase transitions in systems with continuous symmetries. We review the method in the conte…
Heisenberg models and Schur--Weyl duality
Jakob Björnberg, Hjalmar Rosengren, Kieran Ryan
We present a detailed analysis of certain quantum spin systems with inhomogeneous (non-random) mean-field interactions. Examples include, but are not limited to, the interchange- a…
Fermionic observables in the transverse Ising chain
Jakob E. Björnberg
We introduce a notion of s-holomorphicity suitable for certain quantum spin systems in one dimension, and define two observables in the critical transverse-field Ising model which…
The free energy in a class of quantum spin systems and interchange processes
J. E. Björnberg
We study a class of quantum spin systems in the mean-field setting of the complete graph. For spin the model is the Heisenberg ferromagnet, for general spin $S\in\tfra…
Vanishing critical magnetization in the quantum Ising model
Jakob E. Björnberg
Adapting the recent argument of Aizenman, Duminil-Copin and Sidoravicius for the classical Ising model, it is shown here that the magnetization in the transverse-field Ising model…