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|Type:||Artigo de periódico|
|Title:||Long Time Tails In The Dynamics Of The Spatially Inhomogeneous Magnetization Of Dimerized Isotropic Xy Chains For Spin S = 1/2|
|Abstract:||Exact results for the dynamics of the spatially inhomogeneous magnetization (SIM) in the one-dimensional dimerized isotropic XY model are obtained, and the long-time behavior of SIM is considered in detail. It is shown that in the asymptotic limit t → ∞, the time dependence of SIM can be represented as a sum of several components oscillating at different frequencies. Amplitudes of these components decrease according to the (t/τ)-ν power law. It is shown that both, the inverse of the time scale τ-1 and the exponent ν, have critical-like behavior with respect to the wave-vector Q characterizing the spatial inhomogeneity of the initial state. The value of τ-1 goes to zero at |Q| → Qci, where Qci (i = 1,2,3) are critical values of Q determined by parameters of the main Hamiltonian only. Just at points Qc1, Qc2, the exponent ν changes its value discontinuously from ν = 1/2 to ν = 1/4. This effect is very similar to the critical slowing down phenomena in phase transitions. Due to the long-time tails in the relaxation process, we critically discuss the validity of the spin temperature assumption in spin systems.|
|Appears in Collections:||Unicamp - Artigos e Outros Documentos|
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