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@INPROCEEDINGS{Novotny:811604,
      author       = {Novotny, Mark and Jin, Fengping and Yuan, Shengjun and
                      Miyashita, Seiji and De Raedt, Hans and Michielsen, Kristel},
      title        = {{D}ecoherence and {T}hermalization at {F}inite
                      {T}emperatures for {Q}uantum {S}ystems},
      reportid     = {FZJ-2016-04023},
      year         = {2016},
      abstract     = {We consider a quantum system $S$ with Hamiltonian ${\cal
                      H}_S$ coupled via a Hamiltonian ${\cal H}_{SE}$ to a quantum
                      environment $E$ with Hamiltonian ${\cal H}_E$. We assume the
                      entirety $S+E$ is in a canonical-thermal state at an inverse
                      temperature $\beta$. The entirety is a closed quantum system
                      which evolves via the time-dependent Schr{\”o}dinger
                      equation with Hamiltonian ${\cal H}={\cal H}_S+{\cal
                      H}_E+\lambda{\cal H}_{SE}$ where $\lambda$ is the overall
                      strength of the system-environment coupling. Using both
                      large-scale simulations and perturbation theory calculations
                      in $\lambda$, we have studied a measure $\sigma(t)$ for
                      decoherence and $\delta(t)$ for thermalization of $S$. We
                      performed large-scale parallel calculations on spin systems
                      with up to $N=40$ spins in the entirety, with both real-time
                      and imaginary-time quantum calculations. We performed
                      perturbation theory calculations about $\lambda=0$ and
                      fluctuations about the average for the canonical-thermal
                      ensemble, for both $\sigma$ and $\delta$. We obtained closed
                      form expressions for both $\sigma$ and $\delta$, in terms of
                      the free energies of $S$ and $E$. Our perturbation theory
                      calculations agree very well with our numerical
                      calculations, at least as long as $\beta\lambda$ is small.},
      month         = {Jul},
      date          = {2016-07-18},
      organization  = {26th IUPAP International conference on
                       Statistical Physics, Lyon (France), 18
                       Jul 2016 - 22 Jul 2016},
      subtyp        = {Other},
      cin          = {JSC},
      cid          = {I:(DE-Juel1)JSC-20090406},
      pnm          = {511 - Computational Science and Mathematical Methods
                      (POF3-511)},
      pid          = {G:(DE-HGF)POF3-511},
      typ          = {PUB:(DE-HGF)24},
      url          = {https://juser.fz-juelich.de/record/811604},
}