Hölder continuity for continuous solutions of the singular minimal surface equation with arbitrary zero set

In this paper we prove the following theorem: Let \(\Omega \subset \mathbb {R}^{n}\) be a bounded open set, \(\psi \in C_{c}^{2}(\mathbb {R}^{n})\), \(\psi > 0\) on \(\partial \Omega \), be given boundary values and u a nonnegative solution to the problem

$$\begin{aligned}&u \in C^{0}(\overline{\Omega }) \cap C^{2}(\{u> 0\}) \\&u = \psi \quad \text { on } \; \partial \Omega \\&{\text {div}} \left( \frac{Du}{\sqrt{1 + |Du|^{2}}}\right) = \frac{\alpha }{u \sqrt{1 + |Du|^{2}}} \quad \text { in } \; \{u > 0\} \end{aligned}$$

where \(\alpha > 0\) is a given constant. Then \(u \in C^{0, \frac{1}{2}} (\overline{\Omega })\). Furthermore we prove strict mean convexity of the free boundary \(\partial \{u = 0\}\) provided \(\partial \{u = 0\}\) is assumed to be of class \(C^{2}\) and \(\alpha \ge 1\).

     

Improved regularity of harmonic map flows with Hölder continuous energy

For a smooth harmonic map flow with blow-up as , it has been asked [5,6,7] whether the weak limit is continuous. Recently, in [12], we showed that in general it need not be. Meanwhile, the energy function , being weakly positive, smooth and weakly decreasing, has a continuous extension to [0,T]. Here we show that if this extension is also Hölder continuous, then the weak limit u(T) must also be Hölder continuous.Received: 1 September 2003, Accepted: 7 October 2003, Published online: 25 February 2004Version of 19/9/03. Partly supported by an EPSRC Advanced Research Fellowship.     

Ergodicity of scalar stochastic differential equations with Hölder continuous coefficients

It is well-known that for a one dimensional stochastic differential equation driven by Brownian noise, with coefficient functions satisfying the assumptions of the Yamada–Watanabe theorem (Yamada and Watanabe, 1971, [31,32]) and the Feller test for explosions (Feller, 1951, 1954), there exists a unique stationary distribution with respect to the Markov semigroup of transition probabilities. We consider systems on a restricted domain $D$ of the phase space $\mathbb{R}$ and study the rate of convergence to the stationary distribution. Using a geometrical approach that uses the so called free energy function on the density function space, we prove that the density functions, which are solutions of the Fokker–Planck equation, converge to the stationary density function exponentially under the Kullback–Leibler divergence, thus also in the total variation norm. The results show that there is a relation between the Bakry–Émery curvature dimension condition and the dissipativity condition of the transformed system under the Fisher–Lamperti transformation. Several applications are discussed, including the Cox–Ingersoll–Ross model and the Ait-Sahalia model in finance and the Wright–Fisher model in population genetics.     

On the extension of Hölder maps with values in spaces of continuous functions

We study the isometric extension problem for Hölder maps from subsets of any Banach space intoc ₀ or into a space of continuous functions. For a Banach spaceX, we prove that anyα-Hölder map, with 0<α ≤1, from a subset ofX intoc ₀ can be isometrically extended toX if and only ifX is finite dimensional. For a finite dimensional normed spaceX and for a compact metric spaceK, we prove that the set ofα’s for which allα-Hölder maps from a subset ofX intoC(K) can be extended isometrically is either (0, 1] or (0, 1) and we give examples of both occurrences. We also prove that for any metric spaceX, the above described set ofα’s does not depend onK, but only on finiteness ofK.     

Hölder continuity of interfaces for the porous medium equation with absorption

In this paper, we study the one-dimensional motion of viscous gas connecting to vacuum state with a jump in density when the viscosity depends on the density. Precisely, when the viscosity coefficient μ is proportional to ρ^θ and 0 < θ < 1/2, where ρ is the density, the global existence and the uniqueness of weak solutions are proved. This improves the previous results by enlarging the interval of θ.     

Regularity results for deep-water waves with Hölder continuous vorticity

In this paper we study the regularity properties of periodic deep-water waves travelling under the influence of gravity. The flow beneath the wave surface is assumed to be rotational and the vorticity function is taken to be uniformly Hölder continuous. Excluding the presence of stagnation points, we transform the problem on a fixed reference half-plane and we use Schauder estimates to prove that the streamlines and the free surface of such waves are real-analytic graphs.     

Exponential convergence for functional SDEs with Hölder continuous drift

Abstract

Applying Zvonkin’s transform, the exponential convergence in Wasserstein distance for a class of functional SDEs with Hölder continuous drift is obtained. This combining with log-Harnack inequality implies the same convergence in the sense of entropy, which also yields the convergence in total variation norm by Pinsker’s inequality.     

Approximation by Riesz sums of periodic functions of Hölder classes

We have found asymptotic equalities for the least upper bounds of the deviations of Riesz sums on the Hölder classes W^rH, r is a nonnegative integer, (t) is an arbitrary convex modulus of continuity.Translated from Matematicheskie Zametki, Vol. 21, No. 3, pp. 341–354, March, 1977.     

The Hölder continuity of the solution map to the b-family equation in weak topology

We prove that the solution map of the $b$ -family equation is Hölder continuous as a map from a bounded set of $H^s(\mathbb{R }), s>\frac{3}{2}$ with $H^r(\mathbb{R })$ ( $0\le r<s$ ) topology, to $C([0, T], H^r(\mathbb{R }))$ for some $T>0$ . Moreover, we show that the obtained exponent of the Hölder continuity is optimal when $s-1<r<s$ .     

Hölder and Lipschitz stability of solution sets in programs with probabilistic constraints

We study perturbations of a stochastic program with a probabilistic constraint and r-concave original probability distribution. First we improve our earlier results substantially and provide conditions implying Hölder continuity properties of the solution sets w.r.t. the Kolmogorov distance of probability distributions. Secondly, we derive an upper Lipschitz continuity property for solution sets under more restrictive conditions on the original program and on the perturbed probability measures. The latter analysis applies to linear-quadratic models and is based on work by Bonnans and Shapiro. The stability results are illustrated by numerical tests showing the different asymptotic behaviour of parametric and nonparametric estimates in a program with a normal probabilistic constraint.Mathematics Subject Classification (2000): 90C15, 90C31     

Area formulas for classes of Hölder continuous mappings of Carnot groups

We prove area formulas for classes of the mappings that are Hölder continuous in the sub-Riemannian sense and defined on nilpotent graded groups. Moreover, in one of the model cases, we establish an area formula for calculating the initial measure and a measure close to it.     

Hölder estimate for the solution of degenerate parabolic equations

Consider the degenerate parabolic equations of the type $$u_t = div A(x,t,u,Du) + b(x,t,u,Du)$$ which is of the same nature as $$u_t = div|Du|^p Du + |Du|^{p + 2} (p > 2).$$ This paper is to study the \(C^{1 + \alpha } ,\frac{{1 + \alpha }}{2}\) Hölder continuity of a class of degenerate parabolic equations and the existence and uniqueness of the initial boundary value problem.     

Eigenfunction statistics for Anderson model with Hölder continuous single site potential

We consider random Schrödinger operators on \(\ell ^{2}(\mathbb {Z}^{d})\) with α-Hölder continuous (0<α≤1) single site distribution. In localized regime, we study the distribution of eigenfunctions in space and energy simultaneously. In a certain scaling limit, we prove limit points are Poisson.