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This paper presents an integrated framework to construct local-energy solutions to fairly general nonlinear diffusion equations for initial data growing at infinity under suitable assumptions on local-energy estimates for approximate solutions. A delicate issue for constructing local-energy solutions resides in the identification of weak limits of nonlinear terms for approximate solutions in a limiting procedure. Indeed, such an identification process often needs the maximal monotonicity of nonlinear elliptic operators (involved in the doubly-nonlinear equations) as well as uniform estimates for approximate solutions; however, even the monotonicity is violated due to a localization of the equations, which is also necessary to derive local-energy estimates for approximate solutions. In the present paper, such an inconsistency is systematically overcome by reducing the original equation to a localized one, where a (no longer monotone) localized elliptic operator is decomposed into the sum of a maximal monotone operator and a perturbation, and by integrating all the other relevant processes. Furthermore, the general framework developed in the present paper is also applied to the Finsler porous medium and fast diffusion equations , which are variants of the classical PME and FDE and also classified as a doubly-nonlinear equation. [ABSTRACT FROM AUTHOR]

We establish theorems on the existence and compactness of solutions to the σ 2 -Nirenberg problem on the standard sphere S 2. A first significant ingredient, a Liouville type theorem for the associated fully nonlinear Möbius invariant elliptic equations, was established in an earlier paper of ours. Our proof of the existence and compactness results requires a number of additional crucial ingredients which we prove in this paper: A Liouville type theorem for the associated fully nonlinear Möbius invariant degenerate elliptic equations, a priori estimates of first and second order derivatives of solutions to the σ 2 -Nirenberg problem, and a Bôcher type theorem for the associated fully nonlinear Möbius invariant elliptic equations. Given these results, we are able to complete a fine analysis of a sequence of blow-up solutions to the σ 2 -Nirenberg problem. In particular, we prove that there can be at most one blow-up point for such a blow-up sequence of solutions. This, together with a Kazdan-Warner type identity, allows us to prove L ∞ a priori estimates for solutions of the σ 2 -Nirenberg problem under some simple generic hypothesis. The higher derivative estimates then follow from classical estimates of Nirenberg and Schauder. In turn, the existence of solutions to the σ 2 -Nirenberg problem is obtained by an application of the by now standard degree theory for second order fully nonlinear elliptic operators. [ABSTRACT FROM AUTHOR]

A remarkable result by S. Artstein-Avidan and V. Milman states that, up to pre-composition with affine operators, addition of affine functionals, and multiplication by positive scalars, the only fully order preserving mapping acting on the class of lower semicontinuous proper convex functions defined on R n is the identity operator, and the only fully order reversing one acting on the same set is the Fenchel conjugation. Here fully order preserving (reversing) mappings are understood to be those which preserve (reverse) the pointwise order among convex functions, are invertible, and such that their inverses also preserve (reverse) such order. In this paper we establish a suitable extension of these results to order preserving and order reversing operators acting on the class of lower semicontinuous proper convex functions defined on arbitrary infinite dimensional Banach spaces. [ABSTRACT FROM AUTHOR]

In this paper, we consider the following problem { (− Δ) p s u (x) = f (u) , u (x) > 0 in Ω , u (x) = 0 on R n ∖ Ω , where (− Δ) p s is the fractional p -Laplacian with p ≥ 2 and Ω : = { x = (x ′ , x n) | x n > φ (x ′) } is an unbounded domain. In the case φ ≡ 0 , it reduces to the upper half space. Without assuming any asymptotic behavior of u near infinity, we first develop narrow region principles in unbounded domains, then using the method of moving planes, we establish the monotonicity of the positive solutions. In most previous literature, to apply the method of moving planes on unbounded domains, one usually needed to assume that the solution tends to zero in certain rate near infinity; or make a Kelvin transform, or divide the solution by a function, so that the new solution possesses such an asymptotic decay. Here we introduce a new idea, estimating the singular integral defining (− Δ) p s along a sequence of auxiliary functions at their maximum points. This way, we only require the solutions be bounded. We believe that this new method will become a useful tool in investigating qualitative properties of solutions for equations involving nonlinear nonlocal operators. [ABSTRACT FROM AUTHOR]

Sturm's strong law of large numbers in CAT (0) spaces has been an influential tool to study the geometric mean or also called Karcher barycenter of positive definite matrices. It provides an easily computable stochastic approximation based on inductive means. Convergence of a deterministic version of this approximation has been proved by Holbrook, providing his "nodice" theorem for the Karcher mean of positive definite matrices. The Karcher mean has also been extended to the infinite dimensional case of positive operators on a Hilbert space by Lawson-Lim and then to probability measures with bounded support by the second author, however the CAT (0) property of the space is lost and one defines the mean as the unique solution of a nonlinear operator equation on a convex Banach-Finsler manifold. The formulations of Sturm's strong law of large numbers and Holbrook's "nodice" approximation are natural and both conjectured to converge, however all previous techniques of their proofs break down, due to the Banach-Finsler nature of the space. In this paper we prove both conjectures by establishing the most general L 1 -form of Sturm's strong law of large numbers and Holbrook's "nodice" theorem in the operator norm by developing a stochastic discrete-time resolvent flow for the Karcher barycenter using its Wasserstein contraction property. [ABSTRACT FROM AUTHOR]