11,494 research outputs found
Thermodynamic Reversibility in Feedback Processes
The sum of the average work dissipated plus the information gained during a
thermodynamic process with discrete feedback must exceed zero. We demonstrate
that the minimum value of zero is attained only by feedback-reversible
processes that are indistinguishable from their time-reversal, thereby
extending the notion of thermodynamic reversibility to feedback processes. In
addition, we prove that in every realization of a feedback-reversible process
the sum of the work dissipated and change in uncertainty is zero.Comment: 6 pages, 4, figures, accepted in EPL, expanded discussion of
thermodynamic reversibilit
Fundamental Bounds on First Passage Time Fluctuations for Currents
Current is a characteristic feature of nonequilibrium systems. In stochastic
systems, these currents exhibit fluctuations constrained by the rate of
dissipation in accordance with the recently discovered thermodynamic
uncertainty relation. Here, we derive a conjugate uncertainty relationship for
the first passage time to accumulate a fixed net current. More generally, we
use the tools of large-deviation theory to simply connect current fluctuations
and first passage time fluctuations in the limit of long times and large
currents. With this connection, previously discovered symmetries and bounds on
the large-deviation function for currents are readily transferred to first
passage times.Comment: 7 pages including S
Proof of the Finite-Time Thermodynamic Uncertainty Relation for Steady-State Currents
The thermodynamic uncertainty relation offers a universal energetic
constraint on the relative magnitude of current fluctuations in nonequilibrium
steady states. However, it has only been derived for long observation times.
Here, we prove a recently conjectured finite-time thermodynamic uncertainty
relation for steady-state current fluctuations. Our proof is based on a
quadratic bound to the large deviation rate function for currents in the limit
of a large ensemble of many copies.Comment: 3 page
Nonequilibrium potential and fluctuation theorems for quantum maps
We derive a general fluctuation theorem for quantum maps. The theorem applies
to a broad class of quantum dynamics, such as unitary evolution, decoherence,
thermalization, and other types of evolution for quantum open systems. The
theorem reproduces well-known fluctuation theorems in a single and simplified
framework and extends the Hatano-Sasa theorem to quantum nonequilibrium
processes. Moreover, it helps to elucidate the physical nature of the
environment inducing a given dynamics in an open quantum system.Comment: 10 page
Quantum fluctuation theorems for arbitrary environments: adiabatic and non-adiabatic entropy production
We analyze the production of entropy along non-equilibrium processes in
quantum systems coupled to generic environments. First, we show that the
entropy production due to final measurements and the loss of correlations obeys
a fluctuation theorem in detailed and integral forms. Second, we discuss the
decomposition of the entropy production into two positive contributions,
adiabatic and non-adiabatic, based on the existence of invariant states of the
local dynamics. Fluctuation theorems for both contributions hold only for
evolutions verifying a specific condition of quantum origin. We illustrate our
results with three relevant examples of quantum thermodynamic processes far
from equilibrium.Comment: 20 pages + 6 of appendices; 7 figures; v2: New example added (example
A) and some minor corrections; accepted in Phys. Rev.
Universal thermodynamic bounds on nonequilibrium response with biochemical applications
Diverse physical systems are characterized by their response to small
perturbations. Near thermodynamic equilibrium, the fluctuation-dissipation
theorem provides a powerful theoretical and experimental tool to determine the
nature of response by observing spontaneous equilibrium fluctuations. In this
spirit, we derive here a collection of equalities and inequalities valid
arbitrarily far from equilibrium that constrain the response of nonequilibrium
steady states in terms of the strength of nonequilibrium driving. Our work
opens new avenues for characterizing nonequilibrium response. As illustrations,
we show how our results rationalize the energetic requirements of two common
biochemical motifs.Comment: 21 pages, 15 figure
Correlation of hippocampal theta rhythm with changes in cutaneous temperature
A possible role for the hippocampus in alerting an animal to changes in cutaneous temperature was examined. Following local warming or cooling of the ears of unanesthetized, loosely restrained rabbits, theta waves (4-7 Hz EEG waves) were recorded from electrodes straddling the hippocampus. The onset of the hippocampal theta rhythm was correlated with changes in cutaneous temperature, an observation consistent with studies indicating that the theta rhythm is a nonspecific response evoked by stimulation of several sensory modalities. Additional data from cats and rabbits were correlated with specific neurons within the hippocampus, namely pyramidal cells. Post stimulus time histograms obtained by excitation of the dorsal fornix were interpreted in terms of excitatory and inhibitory inputs to pyramidal cells. Thus, the theta rhythm, which appears to be evoked by changes in cutaneous temperature, can be related to a specific type of hippocampal neuron which is in turn connected with other areas of the brain involved in temperature regulation
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