Seminari di Fisica Matematica
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| Seminari A.A. 2011-2012 |
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Relatore |
Titolo |
Data |
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Rafael Greenblatt
Università di Roma Tre |
21 Giugno 2012 (giovedì) |
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Lev Kantorovich
King's College London |
19 Giugno 2012 |
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Abstract ritorna |
A fully quantum Generalised Langevin Equation (GLE) for an open
quantum phonon system surrounded by one (or more) quantum phonon heat
bath(s) kept at constant temperature(s) is derived from general principles
of quantum statistical mechanics. The Hamiltonian of the open system is
assumed of the most general form, as well as the force acting on atoms in
the bath region(s); however, the bath(s) is(are) considered as harmonic,
and the coupling to the open system linear with respect to atomic
displacements in the bath(s). We find that non-operator (c-number)
equations of motion for atomic average positions ‹xA(t)›=
Tr[ρ(t)xA] (where xA is a
coordinate of atom A in the open part and ρ(t) is
the time-dependent density operator for the whole system: open part + bath(s))
have a rather general GLE form with memory friction and a Gaussian
distributed random (stochastic) force. We obtain a general expression
for the friction kernel for this Hamiltonian and show that the origin of
the stochastic forces comes from one-phonon fluctuations in the heat bath(s).
A class of solutions for the bath is found which ensures that quantum GLE
goes correctly into the classical GLE [L. Kantorovich - Phys. Rev. B
78 094304 (2008)] upon either high temperature or ℏ → 0 limit.
The derived equations form a basis for fully quantum mechanical
non-equilibrium molecular dynamics (MD) simulations for an open system
surrounded by quantum heat bath(s) at constant temperature (NVT ensemble),
and can be used in simulations of various physical processes where
quantum effects are important, such as e.g. quantum heat transport,
quantum character of H atoms in molecules and solids, irradiation, etc.
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Alessandro Giuliani
Università di Roma Tre |
24 Aprile 2012 |
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Michele Correggi
Università di Roma Tre |
17 Aprile 2012 |
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Michele Bartuccelli
Surrey University |
12 Aprile 2012 (giovedì) |
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Mikko Stenlund
Università di Roma "Tor Vergata" |
03 Aprile 2012 |
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Alessandro Pizzo
University of California Davis |
27 Marzo 2012 (ore 14:00) |
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Francesco Zamponi
ENS, Paris |
02 Febbraio 2012 (giovedì) |
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Massimiliano Berti
Università di Napoli "Federico II" |
27 Gennaio 2012 (venerdì) |
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Antti Kupiainen
University of Helsinki |
26 Gennaio 2012 (giovedì) |
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Carlo Marchioro
Università di Roma "La Sapienza" |
13 Dicembre 2011 |
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Sergio Simonella
Università di Roma "La Sapienza" |
06 Dicembre 2011 |
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Nicolas Rougerie
Université Grenoble 1 CNRS |
29 Novembre 2011 |
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Jürg Fröhlich
ETH, Zürich |
15 Novembre 2011 |
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Alessandro Teta
Università dell'Aquila |
11 Ottobre 2011 |
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Christian Hainzl
Universität Tübingen |
04 Ottobre 2011 (ore 15:30 aula 211) |
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