We consider mixed problems for strongly elliptic second-order systems in a bounded domain with Lipschitz boundary in the space Rn. For such problems, equivalent equations on the boundary in the simplest L2-spaces Hs of Sobolev type are derived, which permits one to represent the solutions via surface potentials. We prove a result on the regularity of solutions in the slightly more general spaces Hsp of Bessel potentials and Besov spaces Bsp. Problems with spectral parameter in the system or in the condition on a part of the boundary are considered, and the spectral properties of the corresponding operators, including the eigenvalue asymptotics, are discussed.

In this paper we study attractors of skew products, for which the following dichotomy is ascertained. These attractors either are not asymptotically stable or possess the following two surprising properties. The intersection of the attractor with some invariant submanifold does not coincide with the attractor of the restriction of the skew product to this submanifold but contains this restriction as a proper subset. Moreover, this intersection is thick on the submanifold, that is, both the intersection and its complement have positive relative measure. Such an intersection is called a bone, and the attractor itself is said to be bony. These attractors are studied in the space of skew products. They have the important property that, on some open subset of the space of skew products, the set of maps with such attractors is, in a certain sense, prevalent, i. e., "big." It seems plausible that attractors with such properties also form a prevalent subset in an open subset of the space of diffeomorphisms.

A two-sided estimate of local multiplicities of Maxwell sets of isolated singularities of smooth functions is proved. This estimate is sharp for semi-homogeneous functions.

We prove that, for any *E* *u* ⊕ *E* *cs* partially hyperbolic *C* 2 diffeomorphism, the *ω*-limit set of a generic (with respect to the Lebesgue measure) point is a union of unstable leaves. As a corollary, we prove a conjecture made by Ilyashenko in his 2011 paper that the Milnor attractor is a union of unstable leaves. In the paper mentioned above, Ilyashenko reduced the local generecity of the existence of a “thick” Milnor attractor in the class of boundary-preserving diffeomorphisms of the product of the interval and the 2-torus to this conjecture.

The investigation of decompositions of a permutation into a product of permutations satisfying certain conditions plays a key role in the study of meromorphic functions or, equivalently, branched coverings of the 2-sphere; it goes back to A. Hurwitz’ work in the late nineteenth century. In 2000 M. Bousquet-Melou and G. Schaeffer obtained an elegant formula for the number of decompositions of a permutation into a product of a given number of permutations corresponding to coverings of genus 0. Their formula has not been generalized to coverings of the sphere by surfaces of higher genera so far. This paper contains a new proof of the Bousquet-Melou-Schaeffer formula for the case of decompositions of a cyclic permutation, which, hopefully, can be generalized to positive genera. © 2015, Springer Science+Business Media New York.

We consider bounded analytic functions in domains generated by sets with the Littlewood– Paley property. We show that each such function is an lp-multiplier.

It is shown that a series of recent (2012–2016) generalizations of the notion of contraction (*F*-contraction, weak *F*-contraction, etc.) in fact reduce to known notions of contraction (due to Browder, Boyd and Wong, Meir and Keeler, etc.).

We consider domains D ⊆ ℝn with C1 boundary and study the following question: For what domains D does the Fourier transform 1D of the characteristic function 1D belong to Lp(ℝn)?

A relationship is considered between ergodic properties of a discrete dynamical system on a compact metric space Ω and characteristics of companion algebro-topological objects, namely, the Ellis enveloping semigroup E, the Kohler enveloping operator semigroup Γ, and the semigroup G being the closure of the convex hull of Γ in the weak-star topology on the operator space End C*(Ω). The main results are formulated for ordinary (having metrizable semigroup E) semicascades and for tame dynamical systems determined by the condition card E ≤ c. A classification of compact semicascades in terms of topological properties of the semigroups specified above is given.

We consider boundary value problems and transmission problems for strongly elliptic second-order systems with boundary conditions on a compact nonclosed Lipschitz surface S with Lipschitz boundary. The main goal is to find conditions for the unique solvability of these problems in the spaces Hs , the simplest L2-spaces of the Sobolev type, with the use of potential type operators on S. We also discuss, first, the regularity of solutions in somewhat more general Bessel potential spaces and Besov spaces and, second, the spectral properties of problems with spectral parameter in the transmission conditions on S, including the asymptotics of the eigenvalues.

It is well known that every module *M* over the algebra ℒ(*X*) of operators on a finite-dimensional space *X* can be represented as the tensor product of *X* by some vector space *E*, *M* ≅ = *E* ⊗ *X*. We generalize this assertion to the case of topological modules by proving that if *X* is a stereotype space with the stereotype approximation property, then for each stereotype module *M* over the stereotype algebra ℒ (*X*) of operators on *X* there exists a unique (up to isomorphism) stereotype space *E* such that *M* lies between two natural stereotype tensor products of *E* by *X*,

. As a corollary, we show that if *X* is a nuclear Fréchet space with a basis, then each Fréchet module *M* over the stereotype operator algebra ℒ(*X*) can be uniquely represented as the projective tensor product of *X* by some Fréchet space E, M=E⊗ˆXM=E⊗^X.