arXiv subjects

Miroslav Grmela

Publications and source records attributed to Miroslav Grmela.

At least 19 recordsLinked to original sources

arXiv2026

Comparison of some geometric frameworks for dissipative evolution in multiscale non-equilibrium thermodynamics

In this paper, we review and compare some geometric frameworks for dissipation in non-equilibrium thermodynamics. We start with a brief overview of classical irreversible thermodynamics and gradient dynamics. Then we discuss several specific frameworks including Rayleigh dissipation potential and the dissipative d'Alembert framework, showing their relations with gradient dynamics. Finally, we discuss frameworks for dissipative evolution generated from Poisson brackets.

cond-mat.stat-mech↗

arXiv2026

Rheological modeling with GENERIC and with the Onsager principle

In this paper we compare three frameworks for modeling flows of complex fluids: (i) local conservations of mass, momentum and energy, (ii) GENERIC, and (iii) Onsager principle. The first is based on the mass, momentum, and energy conservation implied by mechanics, the second on the observed approach of externally unforced fluids to equilibrium states at which their behavior is well described by equilibrium thermodynamics, and the third on the minimal resistance to external influences. The comparison is illustrated on isothermal and incompressible polymeric fluids.

cond-mat.soft↗

arXiv2025

On Geometry of Dissipation in Multiscale Dynamics and Thermodynamics

This manuscript introduces novel approaches to three phenomena. First, we extend the algebraic formulation of kinetic theory within the contact framework by making explicit the gauge freedom, thereby obtaining a formulation in which the phase-space volume itself becomes an additional dynamical variable. Second, we develop a new and simpler geometric formulation of the GENERIC framework, unifying Hamiltonian and gradient dynamics in a contact-geometric setting. This is realized within a specifically constructed graph space, which naturally emerges as an intermediate structure in the geometric Hamilton-Jacobi framework. Finally, we formulate a geometric extension of non-equilibrium thermodynamics in the setting of geometric Hamilton-Jacobi theory, allowing for the inclusion of microturbulence - a key feature of complex dynamical systems.

math-ph↗

arXiv2025

Classical and Multiscale Non-equilibrium Thermodynamics

Classical and multiscale non-equilibrium thermodynamics have different histories and different objectives. In this Note we explain the differences and review some topics in which the multiscale viewpoint of mesoscopic time evolution of macroscopic systems helped to advance the classical non-equilibrium thermodynamics. Eventually, we illustrate the Braun-Le Chatelier principle in dissipative thermodynamics.

cond-mat.stat-mech↗

arXiv2025

Temperature

Conversations about weather, environment, health, cuisine, and even politics, all involve the word "temperature". It was an attempt to understand the working of heat engines that gave the temperature a clear definition. In this Note we put the equilibrium-thermodynamics definition into a larger context of the multiscale thermodynamics, the multiscale rate thermodynamics, and nonphysical environments.

cond-mat.stat-mech↗

arXiv2025

Landau Theory of Dynamic Critical Phenomena in the Rayleigh-Benard System

Physics involving more details than hydrodynamics is needed to formulate rate thermodynamics of the Rayleigh-Bénard system. The Boussinesq vector field is approached in the space of mesoscopic vector fields similarly as equilibrium sates are approached in externally unforced systems in the space of mesoscopic state variables. The approach is driven by gradient of a potential (called a rate entropy). This potential then provides the rate thermodynamics in the same way as the entropy provides thermodynamics for externally unforced systems. By restricting the investigation to a small neighborhood of the critical point we can use the rate-thermodynamic version of the Landau theory.

cond-mat.stat-mech↗

arXiv2024

Conformal and Contact Kinetic Dynamics and Their Geometrization

We propose a conformal generalization of the reversible Vlasov equation of kinetic plasma dynamics, called conformal kinetic theory. In order to arrive at this formalism, we start with the conformal Hamiltonian dynamics of particles and lift it to the dynamical formulation of the associated kinetic theory. The resulting theory represents a simple example of a geometric pathway from dissipative particle motion to dissipative kinetic motion. We also derive the kinetic equations of a continuum of particles governed by the contact Hamiltonian dynamics, which may be interpreted in the context of relativistic mechanics. Once again we start with the contact Hamiltonian dynamics and lift it to a kinetic theory, called contact kinetic dynamics. Finally, we project the contact kinetic theory to conformal kinetic theory so that they form a geometric hierarchy.

math-ph↗

arXiv2024

Roles of Energy and Entropy in Multiscale Dynamics and Thermodynamics

Multiscale thermodynamics is a theory of relations among levels of description. Energy and entropy are its two main ingredients. Their roles in the time evolution describing approach of a level (starting level) to another level involving less details (target level) is examined on several examples, including the level on which macroscopic systems are seen as composed of microscopic particles, mesoscopic levels as kinetic theory of ideal and van der Waals gases, fluid mechanics, the level of chemical kinetics, and the level of equilibrium thermodynamics. The entropy enters the emergence of the target level in two roles. It expresses internal energy, that is the part of the energy that cannot be expressed in terms of the state variables used on the starting level, and it reveals emerging features characterizing the target level by sweeping away unimportant details. In the case when the target level is a mesoscopic level involving time evolution the roles of the energy and the entropy is taken by two different potentials that are related to their rates.

cond-mat.stat-mech↗

arXiv2023

Thermodynamics and Rate Thermodynamics

Approach of mesoscopic state variables to time independent equilibrium sates (zero law of thermodynamics) gives birth to the classical equilibrium thermodynamics. Approach of fluxes and forces to fixed points (equilibrium fluxes and forces) that drive reduced mesoscopic dynamics gives birth to the rate thermodynamics that is applicable to driven systems. We formulate the rate thermodynamics and dynamics, investigate its relation to the classical thermodynamics, to extensions involving more details, to the hierarchy reformulations of dynamical theories, and to the Onsager variational principle. We also compare thermodynamic and dynamic critical behavior observed in closed and open systems. Dynamics and thermodynamics of the van der Waals gas provides an illustration.

cond-mat.stat-mech↗

arXiv2023

Direct Poisson neural networks: Learning non-symplectic mechanical systems

In this paper, we present neural networks learning mechanical systems that are both symplectic (for instance particle mechanics) and non-symplectic (for instance rotating rigid body). Mechanical systems have Hamiltonian evolution, which consists of two building blocks: a Poisson bracket and an energy functional. We feed a set of snapshots of a Hamiltonian system to our neural network models which then find both the two building blocks. In particular, the models distinguish between symplectic systems (with non-degenerate Poisson brackets) and non-symplectic systems (degenerate brackets). In contrast with earlier works, our approach does not assume any further a priori information about the dynamics except its Hamiltonianity, and it returns Poisson brackets that satisfy Jacobi identity. Finally, the models indicate whether a system of equations is Hamiltonian or not.

math-ph↗

arXiv2023

Multiscale Theory

Boltzmann kinetic equation is put into the form of an abstract time evolution equation representing links connecting autonomous mesoscopic dynamical theories involving varying amount of details. In the chronological order we present results that led to the abstract time equation evolution in both state space and the space of vector fields. In the final section we list some open problems.

cond-mat.stat-mech↗

arXiv2022

On the role of geometry in statistical mechanics and thermodynamics I: Geometric perspective

This paper contains a fully geometric formulation of the General Equation for Non-Equilibrium Reversible-Irreversible Coupling (GENERIC). Although GENERIC, which is the sum of Hamiltonian mechanics and gradient dynamics, is a framework unifying a vast range of models in non-equilibrium thermodynamics, it has unclear geometric structure, due to the diverse geometric origins of Hamiltonian mechanics and gradient dynamics. The difference can be overcome by cotangent lifts of the dynamics, which leads, for instance, to a Hamiltonian form of gradient dynamics. Moreover, the lifted vector fields can be split into their holonomic and vertical representatives, which provides a geometric method of dynamic reduction. The lifted dynamics can be also given physical meaning, here called the rate-GENERIC. Finally, the lifts can be formulated within contact geometry, where the second law of thermodynamics is explicitly contained within the evolution equations.

cond-mat.stat-mech↗

arXiv2022

On the role of geometry in statistical mechanics and thermodynamics II: Thermodynamic perspective

The General Equation for Non-Equilibrium Reversible-Irreversible Coupling (GENERIC) provides structure of mesoscopic multiscale dynamics that guarantees emergence of equilibrium states. Similarly, a lift of the GENERIC structure to iterated cotangent bundles, called a rate GENERIC, guarantees emergence of the vector fields that generate the approach to equilibrium. Moreover, the rate GENERIC structure also extends Onsager's variational principle. The MaxEnt (Maximum Entropy) principle in the GENERIC structure becomes the Onsager variational principle in the rate GENERIC structure. In the absence of external forces, the rate entropy is a potential that is closely related to the entropy production. In the presence of external forces when the entropy does not exist, the rate entropy still exists. While the entropy at the conclusion of the GENERIC time evolution gives rise to equilibrium thermodynamics, the rate entropy at the conclusion of the rate GENERIC time evolution gives rise to rate thermodynamics. Both GENERIC and rate GENERIC structures are put into the geometrical framework in the first paper of this series. The rate GENERIC is also shown to be related to Grad's hierarchy analysis of reductions of the Boltzmann equation. Chemical kinetics and kinetic theory provide illustrative examples. We introduce rate GENERIC extensions (and thus also Onsager-variational-principle formulations) of both chemical kinetics and the Boltzmann kinetic theory.

cond-mat.stat-mech↗

arXiv2021

Fluctuating Multiscale Mass Action Law

The classical mass action law in chemical kinetics is put into the context of multiscale thermodynamics.Despite the purely dissipative character of the classical mass action law, inertial effects also play a role in chemical kinetics. Therefore, the kinetics is extended to an enlarged state space with reaction rates as new state variables and bringing inertial effects. The dynamics is then lifted to the Liouville description within kinetic theory on the enlarged state space in order to include fluctuations. Subsequently, the kinetic theory is reduced to its first and second moments, leading to a new Grad-like hierarchy in chemical kinetics, expressing the multiscale nature of the chemical kinetic with inertia. Dissipation within the extended state space is proposed and it is shown to lead to the classical mass action law when the moments relax to their respective quasi-equilibria. In particular, we demonstrate the possibility of oscillating homogeneous chemical reactions and how the correlations of fluctuations correspond with the chemical kinetics.

physics.chem-ph↗

arXiv2021

A case study of non-Fourier heat conduction using Internal Variables and GENERIC

Applying simultaneously the methodology of Non-Equilibrium Thermodynamics with Internal Variables (NET-IV) and the framework of General Equation for the Non-Equilibrium Reversible-Irreversible Coupling (GENERIC), we demonstrate that, in heat conduction theories, entropy current multipliers can be interpreted as relaxed state variables. Fourier's law and its various extensions -- the Maxwell-Cattaneo-Vernotte, Guyer-Krumhansl, Jeffreys type, Ginzburg-Landau (Allen-Cahn) type and ballistic-diffusive -- heat conduction equations are derived in both formulations. Along these lines, a comparison of NET-IV and GENERIC is also performed. Our results may pave the way for microscopic/multiscale understanding of beyond-Fourier heat conduction, and open new ways for numerical simulations of heat-conduction problems.

physics.class-ph↗

arXiv2021

Learning Physics from Data: a Thermodynamic Interpretation

Experimental data bases are typically very large and high dimensional. To learn from them requires to recognize important features (a pattern), often present at scales different to that of the recorded data. Following the experience collected in statistical mechanics and thermodynamics, the process of recognizing the pattern (the learning process) can be seen as a dissipative time evolution driven by entropy from a detailed level of description to less detailed. This is the way thermodynamics enters machine learning. On the other hand, reversible (typically Hamiltonian) evolution is propagation within the levels of description, that is also to be recognized. This is how Poisson geometry enters machine learning. Learning to handle free surface liquids and damped rigid body rotation serves as an illustration.

physics.data-an↗

arXiv2020

Multiscale Thermodynamics

Multiscale thermodynamics is a theory of relations among levels of investigation of complex systems. It includes the classical equilibrium thermodynamics as a special case but it is applicable to both static and time evolving processes in externally and internally driven macroscopic systems that are far from equilibrium and are investigated on microscopic, mesoscopic, and macroscopic levels. In this paper we formulate the multiscale thermodynamics, explain its origin, and illustrate it in mesoscopic dynamics that combines levels.

cond-mat.stat-mech↗

arXiv2020

Generalization of the dynamical lack-of-fit reduction

The lack-of-fit statistical reduction, developed and formulated first by Bruce Turkington, is a general method taking Liouville equation for probability density (detailed level) and transforming it to reduced dynamics of projected quantities (less detailed level). In this paper the method is generalized. The Hamiltonian Liouville equation is replaced by an arbitrary Hamiltonian evolution combined with gradient dynamics (GENERIC), the Boltzmann entropy is replaced by an arbitrary entropy, and the kinetic energy by an arbitrary energy. The gradient part is a generalized gradient dynamics generated by a dissipation potential. The reduced evolution of the projected state variables is shown to preserve the GENERIC structure of the original (detailed level) evolution. The dissipation potential is obtained by solving a Hamilton-Jacobi equation. In summary, the lack-of-fit reduction can start with GENERIC and obtain GENERIC for the reduced state variables.

cond-mat.stat-mech↗