A connection between a general class of superparabolic functions and supersolutions

We show for a general class of parabolic equations that every bounded superparabolic function is a weak supersolution and, in particular, has derivatives in a Sobolev sense. To this end, we establish various comparison principles between super- and subparabolic functions, and show that a pointwise limit of uniformly bounded weak supersolutions is a weak supersolution.     

Nonlinear parabolic capacity and polar sets of superparabolic functions

We extend the theory of the thermal capacity for the heat equation to nonlinear parabolic equations of the $p$ -Laplacian type. We study definitions and properties of the nonlinear parabolic capacity and show that the capacity of a compact set can be represented via a capacitary potential. As an application, we show that polar sets of superparabolic functions are of zero capacity. The main technical tools used include estimates for equations with measure data and obstacle problems.     

The porous medium equation with measure data

We study the existence of solutions to the porous medium equation with a nonnegative, finite Radon measure on the right-hand side. We show that such problems have solutions in a wide class of supersolutions. These supersolutions are defined as lower semicontinuous functions obeying a parabolic comparison principle with respect to continuous solutions. We also consider the question of how the integrability of the gradient of solutions is affected if the measure is given by a function in L ^s , for a small exponent s > 1.     

Barrier functions for one class of semilinear parabolic equations

For a parabolic quasilinear equation with monotone convex potential, we construct superparabolic and subparabolic barrier functions by the method of decomposition. Translated from Ukrains’kyi Matematychnyi Zhurnal, Vol. 60, No. 11, pp. 1449–1456, November, 2008.     

Existence for a degenerate Cauchy problem

We prove the existence of a solution to the degenerate parabolic Cauchy problem with a possibly unbounded Radon measure as an initial data. To accomplish this, we establish a priori estimates and derive a compactness result. We also show that the result is optimal in the Euclidian setting.     

Trace au bord latéral des solutions positives d'équations paraboliques non linéaires

Let us consider the equation (PE): in Q_T B x (0, T), where B is the open unit ball in R^N. We show that every positive solution u possesses a uniquely defined trace on ∂₁Q_T = ∂B x (0, T), given by a positive, regular Borel measure (not necessarily a Radon measure). If, there exists a one-to-one correspondence between the set of measures as above and the set of positive solutions of (PE) vanishing for t = 0.     

On the solvability of the Cauchy problem with growing initial data for a class of anisotropic parabolic equations

We study the Cauchy problem for a doubly nonlinear parabolic equation with anisotropic degeneration in the case where the initial data are locally finite Radon measures growing, generally saying, at infinity. The weak solution of the problem is obtained as the limit of regular solutions with smoothed initial data.     

On measures on Rosenthal compacta

We show that if K is Rosenthal compact which can be represented by functions with countably many discontinuities then every Radon measure on K is countably determined. We also present an alternative proof of the result stating that every Radon measure on an arbitrary Rosenthal compactum is of countable type. Our approach is based on some caliber-type properties of measures, parameterized by separable metrizable spaces.     

On Efimov spaces and Radon measures

We give a construction under CH of an infinite Hausdorff compact space having no converging sequences and carrying no Radon measure of uncountable type. Under ? we obtain another example of a compact space with no convergent sequences, which in addition has the stronger property that every nonatomic Radon measure on it is uniformly regular. This example refutes a conjecture of Mercourakis from 1996 stating that if every measure on a compact space K is uniformly regular then K is necessarily sequentially compact.     

Boundedness of the gradient for a doubly nonlinear parabolic equation

We prove the local boundedness of the gradient for positive solutions to a doubly nonlinear parabolic equation in the case when the standard Lebesgue measure has been replaced by a doubling measure which supports a weak Poincaré inequality.     

Convergence of solutions of the weighted Allen–Cahn equations to Brakke type flow

In this paper, we study the parabolic Allen–Cahn equation, which has slow diffusion and fast reaction, with a potential K. In particular, the convergence of solutions to a generalized Brakke’s mean curvature flow is established in the limit of a small parameter \( \varepsilon \rightarrow 0\). More precisely, we show that a sequence of Radon measures, associated to energy density of solutions to the parabolic Allen–Cahn equation, converges to a weight measure of an integral varifold. Moreover, the limiting varifold evolves by a vector which is the difference between the mean curvature vector and the normal part of \({\nabla K}/{2K}\).     

Monotone schemes for a class of nonlinear elliptic and parabolic problems

We construct monotone numerical schemes for a class of nonlinear PDE for elliptic and initial value problems for parabolic problems. The elliptic part is closely connected to a linear elliptic operator, which we discretize by monotone schemes, and solve the nonlinear problem by iteration. We assume that the elliptic differential operator is in the divergence form, with measurable coefficients satisfying the strict ellipticity condition, and that the right-hand side is a positive Radon measure. The numerical schemes are not derived from finite difference operators approximating differential operators, but rather from a general principle which ensures the convergence of approximate solutions. The main feature of these schemes is that they possess stencils stretching far from basic grid-rectangles, thus leading to system matrices which are related to M-matrices.     

On the connection between the Hilger and Radon–Nikodym derivatives

We show that the Hilger derivative on time scales is a special case of the Radon–Nikodym derivative with respect to the natural measure associated with every time scale. Moreover, we show that the concept of delta absolute continuity agrees with the one from measure theory in this context.     

Periodic-parabolic eigenvalue problems with indefinite weight functions

We improve a result on the existence and uniqueness of a positive principal eigenvalue of a periodic parabolic equation with respect to an indefinite weight function due to Beltramo and Hess. We remove the regularity conditions on the domain and weaken considerably the regularity assumptions on the weight and the coefficients of the parabolic operator. Further we give a perturbation theorem for the principal eigenvalue which allows to perturb the domain, the coefficients of the parabolic operator and the weight simultaneously.     

A weak existence theorem and weak permanence properties for strong liftings

On a locally compact space with a first-uncountable basis for its topology every positive Radon measure is majorized by an upper integral which admits a strong lifting. The set of B-continuous measures on any space that are majorized by an upper integral with strong lifting forms a band.Supported by NSF-Grant-20541     

Generalized positive continuous additive functionals of multidimensional Brownian motion and their associated Revuz measures

We extend the notion of positive continuous additive functionals of multidimensional Brownian motions to generalized Wiener functionals in the setting of Malliavin calculus. We call such a functional a generalized PCAF. The associated Revuz measure and a characteristic of a generalized PCAF are also extended adequately. By making use of these tools a local time representation of generalized PCAFs is discussed. It is known that a Radon measure corresponds to a generalized Wiener functional through the occupation time formula. We also study a condition for this functional to be a generalized PCAF and the relation between the associated Revuz measure of the generalized PCAF corresponding to Radon measure and this Radon measure. Finally we discuss a criterion to determine the exact Meyer–Watanabe’s Sobolev space to which this corresponding functional belongs.     

Anisotropic Parabolic Equations with Measure Data

In this paper, we prove the existence of solutions to anisotropic parabolic equations with right hand side term in the bounded Radon measure M(Q) and the initial condition in M(Ω) or in L^m space (with m “small”).     

Harnack estimates for a quasi-linear parabolic equation with a singular weight

In this paper, based on measure theoretical arguments, we establish Harnack estimates and Hölder continuity of nonnegative weak solutions for a degenerate parabolic equation with a singular weight. We transform the equation by performing the change of function. The energy estimates, the upper boundedness, the lower boundedness and the expansion of positivity for the solutions to the transformed equation are obtained. Then our aim is reached.     

Local approximation of superharmonic and superparabolic functions in nonlinear potential theory

We prove that arbitrary superharmonic functions and superparabolic functions related to the p-Laplace and the p-parabolic equations are locally obtained as limits of supersolutions with desired convergence properties of the corresponding Riesz measures. As an application we show that a family of uniformly bounded supersolutions to the p-parabolic equation contains a subsequence that converges to a supersolution.     

Cauchy problem and initial traces for fast diffusion equation with space-dependent source

We consider existence of initial traces of nonnegative solutions for fast diffusion equation with space-dependent source and the solvability of the Cauchy problem when the initial datum is merely a function in ${L_{{\rm loc}}^1(R^N)}$ or even a Radon measure.