Benedikt Fauseweh, Götz S. Uhrig
It is shown that the one-dimensional transverse field Ising model in the high-field limit can be solved by continuous unitary transformations in an essentially exact way. This stems from the closure of the relevant algebra of operators which we call string operators. The closure is related to the possibility to map the model by Jordan-Wigner transformation to non-interacting fermions. But it is proven without referring to this mapping. The effective model derived by the continuous unitary transformations is used to compute the contributions of one, two, and three elementary excitations to the diagonal dynamic structure factors. The three-particle contributions have so far not been addressed analytically, except close to the quantum critical point.
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http://arxiv.org/abs/1302.0230
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