Homogenization Theorem Research Articles

A Variational Perspective on Auxetic Metamaterials of Checkerboard-Type

The main result of this work is a homogenization theorem via variational convergence for elastic materials with stiff checkerboard-type heterogeneities under the assumptions of physical growth and non-self-interpenetration. While the obtained energy estimates are rather standard, determining the effective deformation behavior, or in other words, characterizing the weak Sobolev limits of deformation maps whose gradients are locally close to rotations on the stiff components, is the challenging part. To this end, we establish an asymptotic rigidity result, showing that, under suitable scaling assumptions, the attainable macroscopic deformations are affine conformal contractions. This identifies the composite as a mechanical metamaterial with a negative Poisson’s ratio. Our proof strategy is to tackle first an idealized model with full rigidity on the stiff tiles to acquire insight into the mechanics of the model and then transfer the findings and methodology to the model with diverging elastic constants. The latter requires, in particular, a new quantitative geometric rigidity estimate for non-connected squares touching each other at their vertices and a tailored Poincaré type inequality for checkerboard structures.

Space-time homogenization for nonlinear diffusion

The present paper is concerned with a space-time homogenization problem for nonlinear diffusion equations with periodically oscillating (in space and time) coefficients. Main results consist of a homogenization theorem (i.e., convergence of solutions as the period of oscillation goes to zero) as well as a characterization of homogenized equations. In particular, homogenized matrices are described in terms of solutions to cell-problems, which have different forms depending on the log-ratio of the spatial and temporal periods of the coefficients. At a critical ratio, the cell problem turns out to be a parabolic equation in microscopic variables (as in linear diffusion) and also involves the limit of solutions, which is a function of macroscopic variables. The latter feature stems from the nonlinearity of the equation, and moreover, some strong interplay between microscopic and macroscopic structures can explicitly be seen for the nonlinear diffusion. As for the other ratios, the cell problems are always elliptic (in micro-variable only) and do not involve any macroscopic variables, and hence, micro- and macrostructures are weakly interacting each other. Proofs of the main results are based on the two-scale convergence theory (for space-time homogenization). Furthermore, finer asymptotics of gradients, diffusion fluxes and time-derivatives with certain corrector terms are provided, and a qualitative analysis on homogenized matrices is also performed.

Space–time arithmetic quasi-periodic homogenization for damped wave equations

This paper is concerned with space–time homogenization problems for damped wave equations with spatially periodic oscillating elliptic coefficients and temporally (arithmetic) quasi-periodic oscillating viscosity coefficients. Main results consist of a homogenization theorem, qualitative properties of homogenized matrices which appear in homogenized equations and a corrector result for gradients of solutions. In particular, homogenized equations and cell problems will turn out to deeply depend on the quasi-periodicity as well as the log-ratio of spatial and temporal periods of the coefficients. Even types of equations will change depending on the log-ratio and quasi-periodicity. Proofs of the main results are based on a (very weak) space–time two-scale convergence theory.

Functional limit theorems for power series with rapid decay of moving averages of Hermite processes

We aim to obtain a homogenization theorem for a passive tracer interacting with a fractional, possibly non-Gaussian, noise. To do so, we analyze limit theorems for normalized functionals of Hermite–Volterra processes and extend existing results to cover power series with fast decaying coefficients. We obtain either convergence to a Wiener process, in the short-range dependent case, or to a Hermite process, in the long-range dependent case. Furthermore, we prove convergence in the multivariate case with both, short- and long-range dependent components. Applying this theorem, we obtain a homogenization result for a slow/fast system driven by such Hermite noises.

Quantitative homogenization of the parabolic and elliptic Green’s functions on percolation clusters

We study the heat kernel and the Green’s function on the infinite supercritical percolation cluster in dimension d≥2 and prove a quantitative homogenization theorem for these functions with an almost optimal rate of convergence. These results are a quantitative version of the local central limit theorem proved by Barlow and Hambly in (Electron. J. Probab. 14 (2009) 1–27). The proof relies on a structure of renormalization for the infinite percolation cluster introduced in (Comm. Pure Appl. Math. 71 (2018) 1717–1849), Gaussian bounds on the heat kernel established by Barlow in (Ann. Probab. 32 (2004) 3024–3084) and tools of the theory of quantitative stochastic homogenization. An important step in the proof is to establish a C0,1-large-scale regularity theory for caloric functions on the infinite cluster and is of independent interest.

Homogenization of random convolution energies

We prove a homogenization theorem for a class of quadratic convolution energies with random coefficients. Under suitably stated hypotheses of ergodicity and stationarity we prove that the $\Gamma$-limit of such energy is almost surely a deterministic quadratic Dirichlet-type integral functional, whose integrand can be characterized through an asymptotic formula. The proof of this characterization relies on results on the asymptotic behaviour of subadditive processes. The proof of the limit theorem uses a blow-up technique common for local energies, that can be extended to this `asymptotically-local' case. As a particular application we derive a homogenization theorem on random perforated domains.

Stochastic homogenization of the Landau–Lifshitz–Gilbert equation

Following the ideas of Zhikov and Piatnitski (Izv Math 70(1):19–67, 2006), and more precisely the stochastic two-scale convergence, this paper establishes a homogenization theorem in a stochastic setting for two nonlinear equations: the equation of harmonic maps into the sphere and the Landau–Lifschitz–Gilbert equation. These equations have strong nonlinear features, and in general their solutions are not unique.

Homogenization of quadratic convolution energies in periodically perforated domains

Abstract We prove a homogenization theorem for quadratic convolution energies defined in perforated domains. The corresponding limit is a Dirichlet-type quadratic energy, whose integrand is defined by a non-local cell-problem formula. The proof relies on an extension theorem from perforated domains belonging to a wide class containing compact periodic perforations.

Convergence of a class of nonlinear time delays reaction-diffusion equations

Stability under a variational convergence of nonlinear time delays reaction-diffusion equations is discussed. Problems considered cover various models of population dynamics or diseases in heterogeneous environments where delays terms may depend on the space variable. As a consequence a stochastic homogenization theorem is established and applied to vector disease and logistic models. The results illustrate the interplay between the growth rates and the time delays which are mixed in the homogenized model.

Homogenization for Generalized Langevin Equations with Applications to Anomalous Diffusion

We study homogenization for a class of generalized Langevin equations (GLEs) with state-dependent coefficients and exhibiting multiple time scales. In addition to the small mass limit, we focus on homogenization limits, which involve taking to zero the inertial time scale and, possibly, some of the memory time scales and noise correlation time scales. The latter are meaningful limits for a class of GLEs modeling anomalous diffusion. We find that, in general, the limiting stochastic differential equations for the slow degrees of freedom contain non-trivial drift correction terms and are driven by non-Markov noise processes. These results follow from a general homogenization theorem stated and proven here. We illustrate them using stochastic models of particle diffusion.

Mechanical properties and constitutive model for artificially structured soils with an initial stress-induced anisotropy

A series of triaxial compression tests was performed on artificially structured soil samples with an initial stress- -induced anisotropy at confining pressures of 25, 37.5, 50, 100, 200, and 400 kPa. Based on the results of these tests, a constitutive model for structured soils with initial stress-induced anisotropy was formulated. In the proposed model, the initially anisotropic structured soils are regarded as heterogeneous materials composed of bonded blocks and weaker bands. The bonded blocks (denoted as bonded elements) are described as transversely isotropic elastic– brittle materials, while the weaker bands (denoted as frictional elements) are described by the Lade–Duncan model of elastic–plastic materials. Based on the homogenization theorem for heterogeneous materials, and the introduction of structural parameters such as the breakage ratio and the local strain coefficient, the non-uniform distribution of stress and strain within a representative volume element was obtained. Finally, the parameters of the model were determined based on experimental results. The model was verified with test results, demonstrating that it can effectively capture many important features of artificially structured soils with an initial stress-induced anisotropy.

Oscillatory Integrals and Periodic Homogenization of Robin Boundary Value Problems

In this paper, we consider a family of second-order elliptic systems subject to a periodically oscillating Robin boundary condition. We establish the qualitative homogenization theorem on any Lipschitz domains satisfying a non-resonance condition. We also use the quantitative estimates of oscillatory integrals to obtain the dimension-dependent convergence rates in $L^2$, assuming that the domain is smooth and strictly convex.

Corrector estimates in homogenization of a nonlinear transmission problem for diffusion equations in connected domains.

This paper is devoted to the homogenization of a nonlinear transmission problem stated in a two‐phase domain. We consider a system of linear diffusion equations defined in a periodic domain consisting of two disjoint phases that are both connected sets separated by a thin interface. Depending on the field variables, at the interface, nonlinear conditions are imposed to describe interface reactions. In the variational setting of the problem, we prove the homogenization theorem and a bidomain averaged model. The periodic unfolding technique is used to obtain the residual error estimate with a first‐order corrector.

Stability of a class of nonlinear reaction–diffusion equations and stochastic homogenization

We establish a convergence theorem for a class of nonlinear reaction-diffusion equations when the diffusion term is the subdifferential of a convex functional in a class of functionals of the calculus of variations equipped with the Mosco-convergence. The reaction term, which is not globally Lipschitz with respect to the state variable, gives rise to bounded solutions, and cover a wide variety of models. As a consequence we prove a homogenization theorem for this class under a stochastic homogenization framework.

Vibrations of a Fluid Containing a Wide Spaced Net with Floats Under Its Free Surface

We consider the problem of low-frequency vibrations of a heavy viscous incompressible fluid occupying a vessel. Under the free surface of the fluid, there is a wide spaced net with floats forming a nonperiodic structure. On the walls of the vessel and the surface of the floats the adhesion condition (zero Dirichlet condition) is imposed. For this problem, which is formulated in terms of a quadratic operator pencil, we construct a limit (homogenized) pencil and establish a homogenization theorem in the case of a “fairly small” number of floats. It is shown that asymptotically, this structure does not affect free vibrations of the fluid.

Non-metricity in the continuum limit of randomly-distributed point defects

We present a homogenization theorem for isotropically-distributed point defects, by considering a sequence of manifolds with increasingly dense point defects. The loci of the defects are chosen randomly according to a weighted Poisson point process, making it a continuous version of the first passage percolation model. We show that the sequence of manifolds converges to a smooth Riemannian manifold, while the Levi-Civita connections converge to a non-metric connection on the limit manifold. Thus, we obtain rigorously the emergence of a non-metricity tensor, which was postulated in the literature to represent continuous distribution of point defects.

On the Steklov problem in a domain perforated along a part of the boundary

We study the asymptotic behavior of solutions and eigenelements to a 2-dimensional and 3-dimensional boundary value problem for the Laplace equation in a domain perforated along part of the boundary. On the boundary of holes we set the homogeneous Dirichlet boundary condition and the Steklov spectral condition on the mentioned part of the outer boundary of the domain. Assuming that the boundary microstructure is periodic, we construct the limit problem and prove the homogenization theorem.

On a singularly perturbed Steklov problem in a domain perforated along the boundary

We study the asymptotic behavior of solutions and eigenelements to a boundary value problem for the Laplace equation in a domain perforated along part of the boundary. On the boundary of holes, we set the homogeneous Dirichlet boundary condition and the Steklov spectral condition on the mentioned part of the outer boundary of the domain. Assuming that the boundary microstructure is periodic, we construct the limit problem and prove the homogenization theorem. Nous étudions le comportement asymptotique des solutions et des éléments propres à un problème aux limites pour l'équation de Laplace dans un domaine perforé le long d'une partie de la frontière. Sur la frontière de trous, nous posons la condition de Dirichlet homogène et la condition spectrale de Steklov sur la part mentionnée de la frontière extérieure du domaine. En supposant que la microstructure de la frontière est périodique, nous construisons le problème aux limites et prouvons le théorème d'homogénéisation.

The emergence of torsion in the continuum limit of distributed edge-dislocations

We present a rigorous homogenization theorem for distributed dislocations. We construct a sequence of locally-flat Riemannian manifolds with dislocation-type singularities. We show that this sequence converges, as the dislocations become denser, to a flat non-singular Weitzenb\"ock manifold, i.e. a flat manifold endowed with a metrically-consistent connection with zero curvature and non-zero torsion. In the process, we introduce a new notion of convergence of Weitzenb\"ock manifolds, which is relevant to this class of homogenization problems.

Plane Scalar Analog of Linear Degenerate Hydrodynamic Problem with Nonperiodic Microstructure of Free Surface

We consider the degenerate problem on low-frequency oscillations of a heavy viscous incompressible fluid in a vessel with free surface of inhomogeneous nonperiodic microstructure. For the obtained quadratic operator pencil we construct the limit (homogenized) pencil which turns out to be degenerate. We prove a homogenization theorem. Bibliography: 40 titles. Illustration: 2 figures.