930 research outputs found
Stationary and transient Fluctuation Theorems for effective heat flux between hydrodynamically coupled particles in optical traps
We experimentally study the statistical properties of the energy fluxes
between two trapped Brownian particles, interacting through dissipative
hydrodynamic coupling, submitted to an effective temperature difference , obtained by random forcing the position of one trap. We identify effective
heat fluxes between the two particles and show that they satisfy an exchange
fluctuation theorem (xFT) in the stationary state. We also show that after the
sudden application of a temperature gradient , \resub{the total}
hot-cold flux satisfies \resub{a} transient xFT for any integration time
whereas \resub{the total} cold-hot flux only does it asymptotically for long
times
Effective Temperature in a Colloidal Glass
We study the Brownian motion of particles trapped by optical tweezers inside
a colloidal glass (Laponite) during the sol-gel transition. We use two methods
based on passive rheology to extract the effective temperature from the
fluctuations of the Brownian particles. All of them give a temperature that,
within experimental errors, is equal to the heat bath temperature. Several
interesting features concerning the statistical properties and the long time
correlations of the particles are observed during the transition.Comment: to be published in Philosophical Magazin
Work fluctuation theorems for harmonic oscillators
The work fluctuations of an oscillator in contact with a thermostat and
driven out of equilibrium by an external force are studied experimentally and
theoretically within the context of Fluctuation Theorems (FTs). The oscillator
dynamics is modeled by a second order Langevin equation. Both the transient and
stationary state fluctuation theorems hold and the finite time corrections are
very different from those of a first order Langevin equation. The periodic
forcing of the oscillator is also studied; it presents new and unexpected short
time convergences. Analytical expressions are given in all cases
Engineering the Dynamics of Effective Spin-Chain Models for Strongly Interacting Atomic Gases
We consider a one-dimensional gas of cold atoms with strong contact
interactions and construct an effective spin-chain Hamiltonian for a
two-component system. The resulting Heisenberg spin model can be engineered by
manipulating the shape of the external confining potential of the atomic gas.
We find that bosonic atoms offer more flexibility for tuning independently the
parameters of the spin Hamiltonian through interatomic (intra-species)
interaction which is absent for fermions due to the Pauli exclusion principle.
Our formalism can have important implications for control and manipulation of
the dynamics of few- and many-body quantum systems; as an illustrative example
relevant to quantum computation and communication, we consider state transfer
in the simplest non-trivial system of four particles representing
exchange-coupled qubits.Comment: 10 pages including appendix, 3 figures, revised versio
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