32 citations · 116 across the 10 of their papers we have counts for
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math-ph2018★ 9 cited
Quantum spins and random loops on the complete graph
Jakob E. Björnberg, Jürg Fröhlich, Daniel Ueltschi
We present a systematic analysis of quantum Heisenberg-, XY- and interchange models on the complete graph. These models exhibit phase transitions accompanied by spontaneous symmetr…
math-ph2015★ 10 cited
Decay of transverse correlations in quantum Heisenberg models
Jakob E. Björnberg, Daniel Ueltschi
We study a class of quantum spin systems that includes the Heisenberg and XY-models, and prove that two-point correlations exhibit exponential decay in the presence of…
math-ph2009★ 32 cited
The phase transition of the quantum Ising model is sharp
J. E. Björnberg, G. R. Grimmett
An analysis is presented of the phase transition of the quantum Ising model with transverse field on the d-dimensional hypercubic lattice. It is shown that there is a unique sharp…