Non-Markovian processes can often be turned Markovian by enlarging the set of variables. Here we show, by an explicit construction, how this can be done for the dynamics of a Brownian particle obeying the generalized Langevin equation. Given an arbitrary bath spectral density J0, we introduce an orthogonal transformation of the bath variables into effective modes, leading stepwise to a semi-infinite chain with nearest-neighbor interactions. The transformation is uniquely determined by J0 and defines a sequence {Jn}nεN of residual spectral densities describing the interaction of the terminal chain mode, at each step, with the remaining bath. We derive a simple one-term recurrence relation for this sequence and show that its limit is the quasi-Ohmic expression provided by the Rubin model of dissipation. Numerical calculations show that, irrespective of the details of J0, convergence is fast enough to be useful in practice for an effective Ohmic reduction of the dissipative dynamics.

Communication : Universal Markovian reduction of Brownian particle dynamics / R. Martinazzo, B. Vacchini, K.H. Hughes, I. Burghardt. - In: THE JOURNAL OF CHEMICAL PHYSICS. - ISSN 0021-9606. - 134:1(2011 Jan 03), pp. 011101.1-011101.5.

Communication : Universal Markovian reduction of Brownian particle dynamics

R. Martinazzo
;
B. Vacchini;
2011-01-03

Abstract

Non-Markovian processes can often be turned Markovian by enlarging the set of variables. Here we show, by an explicit construction, how this can be done for the dynamics of a Brownian particle obeying the generalized Langevin equation. Given an arbitrary bath spectral density J0, we introduce an orthogonal transformation of the bath variables into effective modes, leading stepwise to a semi-infinite chain with nearest-neighbor interactions. The transformation is uniquely determined by J0 and defines a sequence {Jn}nεN of residual spectral densities describing the interaction of the terminal chain mode, at each step, with the remaining bath. We derive a simple one-term recurrence relation for this sequence and show that its limit is the quasi-Ohmic expression provided by the Rubin model of dissipation. Numerical calculations show that, irrespective of the details of J0, convergence is fast enough to be useful in practice for an effective Ohmic reduction of the dissipative dynamics.
Settore CHIM/02 - Chimica Fisica
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/2434/802583
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