# Reinaldo García-GarcíaUniversidad de Navarra | UNAV · Department of Physics and Applied Mathematics

Reinaldo García-García

PhD in Physics

Nonequilibrium Statistical Mechanics, Stochastic Thermodynamics, Disordered Elastic Systems, Soft and Active Matter.

## About

36

Publications

7,827

Reads

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328

Citations

Citations since 2017

Introduction

Reinaldo García García is a theoretical physicist currently studying the statistical properties of complex nonequilibrium systems. He is particularly interested in the physics of disordered materials, and in the mathematical modelling of active and living systems. He is also currently working on problems related to heterogeneous condensation patterns and Breath Figures.

Additional affiliations

February 2016 - April 2017

May 2014 - January 2015

**École Polytechnique, and, ESPCI-ParisTech.**

Position

- PostDoc Position

April 2014 - present

**ESPCI ParisTech- CNRS**

Position

- PostDoc Position

Education

September 2000 - July 2005

## Publications

Publications (36)

A brief review is made of the birth and evolution of the “nonequilibrium potential” (NEP) concept. As if providing a landscape for qualitative reasoning were not helpful enough, the NEP adds a quantitative dimension to the qualitative theory of differential equations and provides a global Lyapunov function for the deterministic dynamics. Here we il...

The coarse-graining of amorphous plasticity from the atomistic to the mesoscopic scale is studied in the framework of a simple scalar elasto-plastic model. Building on recent results obtained on the atomistic scale, we discuss the interest in a disordered landscape-informed threshold disorder to reproduce the physics of amorphous plasticity. We sho...

Cross‐species communication, where signals are sent by one species and perceived by others, is one of the most intriguing types of communication that functionally links different species to form complex ecological networks. Global change and human activity can affect communication by increasing fluctuations in species composition and phenology, alt...

We study the Stochastic Thermodynamics of cell growth and division using a theoretical framework based on branching processes with resetting. Cell division may be split into two sub-processes: branching, by which a given cell gives birth to an identical copy of itself, and resetting, by which some properties of the daughter cells (such as their siz...

A brief review is made of the birth and evolution of the ‘‘nonequilibrium potential’’ (NEP) concept. As if
providing a landscape for qualitative reasoning were not helpful enough, the NEP adds a quantitative dimension
to the qualitative theory of differential equations and provides a global Lyapunov function for the deterministic
dynamics. Here we...

We study the Stochastic Thermodynamics of cell growth and division using a theoretical framework based on branching processes with resetting. Cell division may be split into two sub-processes: branching, by which a given cell gives birth to an identical copy of itself, and resetting, by which some properties of the daughter cells (such as their siz...

Cross-species communication, where signals are sent by one species and perceived by others, is one of the most intriguing types of communication that functionally links different species to form complex ecological networks. Yet, global changes and human activities can affect communication by increasing the fluctuations of species composition and ph...

We develop a maximum likelihood method to infer relevant physical properties of elongated active particles. Using individual trajectories of advected swimmers as input, we are able to accurately determine their rotational diffusion coefficients and an effective measure of their aspect ratio, also providing reliable estimators for the uncertainties...

We develop a maximum likelihood method to infer relevant physical properties of elongated active particles. Using individual trajectories of advected swimmers as input, we are able to accurately determine their rotational diffusion coefficients and an effective measure of their aspect ratio, also providing reliable estimators for the uncertainties...

To account for the possibility of an externally driven taxis in active systems, we develop a model of a guided active drift which relies on the presence of an external guiding field and a vectorial coupling between the mechanical degrees of freedom and a chemical reaction. To characterize the ability of guided active particles to carry cargo, we ge...

To account for the possibility of an externally driven taxis in active systems, we develop a model of a guided active drift (GAD) which relies on the presence of an external guiding field and a vectorial
coupling between the mechanical degrees of freedom and a chemical reaction. To characterize the ability of guided active particles to carry cargo...

Using a population dynamics inspired by an ensemble of growing cells, a set of fluctuation theorems linking observables measured at the lineage and population levels is derived. One of these relations implies specific inequalities comparing the population doubling time with the mean generation time at the lineage or population levels. While these i...

We study the statistics of the energy dissipated in individual avalanches at the depinning transition. In the regime dominated by the depinning
phenomenology, a relation between the size of an avalanche and its energy can be derived using ”naive” scaling arguments and verified in mean-field
systems. This relation allows to design a method to determ...

Using a population dynamics inspired by an ensemble of growing cells, a set of fluctuation theorems linking observables measured at the lineage and population levels are derived. One of these relations implies inequalities comparing the population doubling time with the mean generation time at the lineage or population levels. We argue that testing...

Using a population dynamics inspired by an ensemble of growing cells, a set of fluctuation theorems linking observables measured at the lineage and population levels are derived. One of these relations implies inequalities comparing the population doubling time with the mean generation time at the lineage or population levels. We argue that testing...

We focus on the mean velocity induced by a constant force applied on one-dimensional interfaces. In presence of disorder the velocity presents a stretched exponential dependence in the force (the so-called ‘creep law’), which is out of reach of linear response. In dimension one, there is no exact analytical derivation of such a law. We propose an e...

Supplemental Material for "Heat leakage in equilibrium processes". This is a very short text dealing with the proof of an important identity used in the main text, and the calculation of an integral leading to the second main result of the manuscript.

The difference between the zero-mass limit of the heat exchanged with a thermal reservoir, and its value as determined from overdamped dynamics,
is termed `heat leakage' or `hidden heat' in the Smoluchowski limit. If present, heat leakages are the sign of the unsuitability of the overdamped approximation
for addressing thermodynamics.
It is accepte...

In these notes I provide a simple derivation of a formal decomposition of the free energy of a directed polymer with fixed end points in presence of a tilting force. The decomposition is explicit in terms of a translationally invariant part, and contribution arising from the external forcing. With that purpose, a modified version of the statistical...

We develop and extend a method presented in [S. Patinet, D. Vandembroucq, and M. L. Falk, Phys. Rev. Lett., 117, 045501 (2016)] to compute the local yield stresses at the atomic scale in model two-dimensional Lennard-Jones glasses produced via differing quench protocols. This technique allows us to sample the plastic rearrangements in a non-perturb...

We consider the amount of energy dissipated during individual avalanches at the depinning transition of disordered and athermal elastic systems. Analytical
progress is possible in the case of the
Alessandro-Beatrice-Bertotti-Montorsi (ABBM) model for
Barkhausen noise, due to an exact mapping between the energy released in an avalanche and the area...

The response of spatially extended systems to a force leading their steady state out of equilibrium is strongly affected by the presence of disorder. We focus on the mean velocity induced by a constant force applied on one-dimensional interfaces. In the absence of disorder, the velocity is linear in the force. In the presence of disorder, it is wid...

Fluctuation theorems have become an important tool in single molecule
biophysics to measure free energy differences from non-equilibrium experiments.
When significant coarse-graining or noise affect the measurements, the
determination of the free energies becomes challenging. In order to address
this thermodynamic inference problem, we propose impr...

We introduce the violation fraction $\upsilon$ as the cumulative fraction of
time that a mesoscopic system spends consuming entropy at a single trajectory
in phase space. We show that the fluctuations of this quantity are described in
terms of a symmetry relation reminiscent of fluctuation theorems, which involve
a function, $\Phi$, which can be in...

We define the {\it violation fraction} $\nu$ as the cumulative fraction of time that the entropy change is negative during single realizations of processes in phase space. This quantity depends on both the number of degrees of freedom $N$ and the duration of the time interval $\tau$. In the large-$\tau$ and large-$N$ limit we show that, for ergodic...

We define the violation fraction ν as the cumulative fraction of time that the entropy change is negative during single realizations of processes in phase space. This quantity depends both on the number of degrees of freedom N and the duration of the time interval τ . In the large-τ and large-N limit we show that, for ergodic and microreversible sy...

We derive a set of exact relations in the context of the stochastic thermodynamics of small
out-of-equilibrium systems. We study the symmetries of the total entropy production upon
certain involutive transformations (e.g. some transformations such that when applied twice
consecutively one is lead to the identity operator). Based on the mentioned sy...

We extend the definition of nonadiabatic entropy production given for Markovian systems by Esposito and Van den Broeck [Phys. Rev. Lett. 104, 090601 (2010)], to arbitrary non-Markov ergodic dynamics. We also introduce a notion of stability characterizing non-Markovianity. For stable non-Markovian systems, the nonadiabatic entropy production satisfi...

We derive various exact results for Markovian systems that spontaneously relax to a non-equilibrium steady state by using joint probability distribution symmetries of different entropy production decompositions. The analytical approach is applied to diverse problems such as the description of the fluctuations induced by experimental errors, for unv...

We study the probability distribution function (PDF) of the position of a Lévy flight of index 0<α<2 in the presence of an absorbing wall at the origin. The solution of the associated fractional Fokker-Planck equation can be constructed using a perturbation scheme around the Brownian solution (corresponding to α=2) as an expansion in ε=2−α. We obta...

We study the statistics of a one-dimensional L\'evy random walks of index 0< \alpha \leq 2 in a semi-bounded domain. We construct a solution of the associated fractional Fokker-Planck equation with non-local boundary conditions using a perturbative expansion in \epsilon = 2 - \alpha

Any decomposition of the total trajectory entropy production for Markovian systems has a joint probability distribution satisfying a generalized detailed fluctuation theorem, when all the contributing terms are odd with respect to time reversal. The expression of the result does not bring into play dual probability distributions, hence easing poten...

Any decomposition of the total trajectory entropy production for Markovian systems has a joint probability distribution satisfying a generalized detailed fluctuation theorem, when all the contributing terms are odd with respect to time reversal. The expression of the result does not bring into play dual probability distributions, hence easing poten...

We study, using exact numerical simulations, the statistics of the longest excursion l(max)(t) up to time t for the fractional Brownian motion with Hurst exponent 0<H<1. We show that in the large t limit, <l(max)(t)> proportional to variantQ(infinity)t, where Q(infinity) identical with Q(infinity)(H) depends continuously on H. These results are com...

Josephson effects are macroscopic quantum phenomena that can be understood at the undergraduate level with the help of mechanical analogs. Although Josephson junctions in zero magnetic field can be modeled by pendulum analogs, a simple mechanical model of Josephson junctions in nonzero fields has been elusive. We demonstrate how the magnetic field...

## Questions

Questions (4)

Understanding the mechanism behind the glass transition is one of those old problems that has resisted massive efforts and huge grants. Many different models have been invented and discussed and, with time, different schools of thought emerged (among theoreticians) to understand the glass transition. Two notable examples are the school of Kinetically Constrained Models (KCM) and the school of the Random First Order Transition (RFOT).

A huge part of the (theoretical) literature in the previous recent years, focuses either on the debate between these two visions, or on the many problems each of them finds in its own way after each step. This is why it is very difficult to find ideas detached from a given school of thought (at least in recent literature).

As a theoretician, I am naturally interested on the technical developments behind these approaches, nevertheless, I'm also curious about the original problem. So, if one could answer this question without any reference to the pre-existing theories and to their constructions, what are the empirical facts that any successful theory of the glass transition must be able to explain?

Classification of thermodynamic phase transitions relies on the analiticity of the Helmholtz free energy (or the corresponding thermodynamic potential, depending on the ensemble). As it is widely known, first-order phase transitions are characterized by a discontinuity in the first derivative of the thermodynamic potential with respect to the relevant intensive variable, while in continuous phase transitions the thermodynamic potentials are continuous and differentiable, but high-order derivatives may be undefined.

Imagine now that one considers a system udergoing a phase transition for given values of temperature, pressure, etc. Is it possible to infer that such a system will exhibit a thermodynamic phase transition by looking at the microcanonical density of states (DOS), instead of the thermodynamic potentials? Does the DOS carry some signature of the phase transitions? If yes, what traits indicate the order of the transition ?

By studying some classical papers (like those on random energy models and trap models by Derrida), one can infer, for instance, that a DOS with edge states can be linked to a thermodynamic freezing (glass) transition. Are there similar signs in the simpler cases of first and second order phase transitions? I intuitively believe there must be, since, for instance, the canonical partition function is simply the Laplace transform of the microcanonical DOS. But I don't know what those signs may be.