9 research outputs found
Strong current response to slow modulation: a metabolic case-study
We study the current response to periodic driving of a crucial biochemical
reaction network, namely, substrate inhibition. We focus on the conversion rate
of substrate into product under time-varying metabolic conditions, modeled by a
periodic modulation of the product concentration. We find that the system
exhibits a strong nonlinear response to small driving frequencies both for the
mean time-averaged current and for the fluctuations. For the first, we obtain
an analytic formula by coarse-graining the original model to a solvable one.
The result is nonperturbative in the modulation amplitude and frequency. We
then refine the picture by studying the stochastic dynamics of the full system
using a large deviations approach, that allows to show the resonant effect at
the level of the time-averaged variance and signal-to-noise ratio. Finally, we
discuss how this nonequilibrium effect may play a role in metabolic and
synthetic networks.Comment: 10 pages, 7 figures Updated fig.5 and appendix with geometric effect
Relaxation-speed crossover in anharmonic potentials
In a recent paper [Phys. Rev. Lett. 125, 110602 (2020)], thermal relaxation
was observed to occur faster from cold to hot (heating) than from hot to cold
(cooling). Here we show that overdamped diffusion in anharmonic single-well
potentials generically allows for both faster heating and faster cooling,
depending on the initial temperatures and on the potential's degree of
anharmonicity. We draw a relaxation-speed phase diagram that localises the
different behaviours in parameter space. In addition to faster-heating and
faster-cooling regions, we identify a crossover region in the phase diagram,
where heating is initially slower but asymptotically faster than cooling.Comment: 6+3 pages, 3+1 figures, submitted to PR
Methods and conversations in (post)modern thermodynamics
Lecture notes after the doctoral school (Post)Modern Thermodynamics held at the University of Luxembourg, December 2022, 5-7, covering and advancing continuous-time Markov chains, network theory, stochastic thermodynamics, large deviations, deterministic and stochastic chemical reaction networks, metastability, martingales, quantum thermodynamics, and foundational issues
ON THE RELATION BETWEEN STOCHASTIC THERMODYNAMICS AND LINEAR IRREVERSIBLE THERMODYNAMICS
Linear Stochastic Thermodynamics
We study the thermodynamics of open systems weakly driven out-of-equilibrium
by nonconservative and time-dependent forces using the linear regime of
stochastic thermodynamics. We make use of conservation laws to identify the
potential and nonconservative components of the forces. This allows us to
formulate a unified near-equilibrium thermodynamics. For nonequilibrium steady
states, we obtain an Onsager theory ensuring nonsingular response matrices that
is consistent with phenomenological linear irreversible thermodynamics. For
time-dependent driving protocols that do not produce nonconservative forces, we
identify the equilibrium ensemble from which Green-Kubo relations are
recovered. For arbitrary periodic drivings, the averaged entropy production
(EP) is expressed as an independent sum over each driving frequency of
non-negative contributions. These contributions are bilinear in the
nonconservative and conservative forces and involve a novel generalized Onsager
matrix that is symmetric. In the most general case of arbitrary time-dependent
drivings, we advance a novel decomposition of the EP rate into two non-negative
contributions - one solely due to nonconservative forces and the other solely
due to deviation from the instantaneous steady-state - directly implying a
minimum entropy production principle close to equilibrium. This setting reveals
the geometric structure of near-equilibrium thermodynamics and generalizes
previous approaches to cases with nonconservative forces.Comment: 25 pages, 5 figure