Thermalization

I’m wondering if people talk about this. Maybe you know?


Given a self-adjoint operator H that’s bounded below and a density matrix D on some Hilbert space, we can define for any \beta > 0 a new density matrix


\displaystyle{ D_\beta = \frac{e^{-\beta H/2} \, D \, e^{-\beta H/2}}{\mathrm{tr}(e^{-\beta H/2} \, D \, e^{-\beta H/2})} }


I would like to call this the thermalization of D when H is a Hamiltonian and \beta = 1/kT where T is the temperature and k is Boltzmann’s constant.


For example, in the finite-dimensional case we can take D to be the identity matrix, normalized to have trace 1. Then D_\beta is the Gibbs state at temperature T: that is, th...

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Published on June 11, 2020 18:17
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