7,937 research outputs found
Entropy production in a photovoltaic cell
We evaluate entropy production in a photovoltaic cell that is modeled by four
electronic levels resonantly coupled to thermally populated field modes at
different temperatures. We use a formalism recently proposed, the so-called
multiple parallel worlds, to consistently address the nonlinearity of entropy
in terms of density matrix. Our result shows that entropy production is the
difference between two flows: a semiclassical flow that linearly depends on
occupational probabilities, and another flow that depends nonlinearly on
quantum coherence and has no semiclassical analog. We show that entropy
production in the cells depends on environmentally induced decoherence time and
energy detuning. We characterize regimes where reversal flow of information
takes place from a cold to hot bath. Interestingly, we identify a lower bound
on entropy production, which sets limitations on the statistics of dissipated
heat in the cells.Comment: 7 pages, 2 figure
Exact correspondence between Renyi entropy flows and physical flows
We present a universal relation between the flow of a Renyi entropy and the
full counting statistics of energy transfers. We prove the exact relation for a
flow to a system in thermal equilibrium that is weakly coupled to an arbitrary
time-dependent and non-equilibrium system. The exact correspondence, given by
this relation, provides a simple protocol to quantify the flows of Shannon and
Renyi entropies from the measurements of energy transfer statistics.Comment: 9 pages, 5 figure
Phase-coexisting patterns, horizontal segregation and controlled convection in vertically vibrated binary granular mixtures
We report new patterns, consisting of coexistence of sub-harmonic/harmonic
and asynchronous states [for example, a granular gas co-existing with (i)
bouncing bed, (ii) undulatory subharmonic waves and (iii) Leidenfrost-like
state], in experiments on vertically vibrated binary granular mixtures in a
Heleshaw-type cell. Most experiments have been carried out with equimolar
binary mixtures of glass and steel balls of same diameter by varying the total
layer-height () for a range of shaking acceleration (). All patterns
as well as the related phase-diagram in the ()-plane have been
reproduced via molecular dynamics simulations of the same system. The
segregation of heavier and lighter particles along the horizontal direction is
shown to be the progenitor of such phase-coexisting patterns as confirmed in
both experiment and simulation. At strong shaking we uncover a {\it partial}
convection state in which a pair of convection rolls is found to coexist with a
Leidenfrost-like state. The crucial role of the relative number density of two
species on controlling the buoyancy-driven granular convection is demonstrated.
A possible model for spontaneous horizontal segregation is suggested based on
anisotropic diffusion
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