Abstract Relative projection constants of certain classes of cubspaces of codimension 2 in \(l_\infty^{2n}\) are found. The minimal projections under considerations are of two kinds, with unit norm and with norm larger than 1.

Abstract In continuous-discrete Sobolev spaces a generalized trace formula for orthogonal polynomials \(\{\widehat{q}_n\}_{n=0}^\infty\) is obtained. The proof of this formula is based on the representation of the Fejér kernel for the system \(\{\widehat{q}_n\}_{n=0}^\infty\). As a consequence, a generalized trace formula for Gegenbauer–Sobolev polynomials in a discrete Sobolev space is obtained.

Abstract In a 2004 paper by V. M. Buchstaber and D. V. Leikin, published in “Functional Analysis and Its Applications,” for each \(g > 0\), a system of \(2g\) multidimensional Schrödinger equations in magnetic fields with quadratic potentials was defined. Such systems are equivalent to systems of heat equations in a nonholonomic frame. It was proved that such a system determines the sigma function

Abstract Quite recently a criterion for the \(\mathcal{A}\)-compactness of an ajointable operator \(F\colon {\mathcal M} \to\mathcal{N}\) between Hilbert \(C^*\)-modules, where \(\mathcal{N}\) is countably generated, was obtained. Namely, a uniform structure (a system of pseudometrics) in \(\mathcal{N}\) was discovered such that \(F\) is \(\mathcal{A}\)-compact if and only if \(F(B)\) is totally bounded

Abstract A natural class of expansive endomorphisms \(G\in C^1\) of the infinite-dimensional torus \(\mathbb{T}^{\infty}\) (the Cartesian product of countably many circles with the product topology) is considered. The endomorphisms in this class can be represented in the form of the sum of a linear expansion and a periodic addition. The following standard facts of hyperbolic theory are proved: the

Abstract We consider the problem of the constancy of the minimizer in the fractional embedding theorem \(\mathcal{H}^s(\Omega) \hookrightarrow L_q(\Omega)\) for a bounded Lipschitz domain \(\Omega\), depending on the domain size. For the family of domains \(\varepsilon \Omega\), we prove that, for small dilation coefficients \(\varepsilon\), the unique minimizer is constant, whereas for large \(\varepsilon\)

Abstract Using a change of basis in the algebra of symmetric functions, we compute the moments of the Hermitian Jacobi process. After a careful arrangement of terms and the evaluation of the determinant of an “almost upper-triangular” matrix, we end up with a moment formula which is considerably simpler than the one derived in [8]. As an application, we propose the Hermitian Jacobi process as a dynamical

Abstract The classical Fourier transform on the line sends the operator of multiplication by \(x\) to \(i\frac{d}{d\xi}\) and the operator \(\frac{d}{d x}\) of differentiation to multiplication by \(-i\xi\). For the Fourier transform on the Lobachevsky plane, we establish a similar correspondence for a certain family of differential operators. It appears that differential operators on the Lobachevsky

Abstract This paper studies spaces of distributions on a dyadic half-line, which is the positive half-line equipped with bitwise binary addition and Lebesgue measure. We prove the nonexistence of a space of dyadic distributions which satisfies a number of natural requirements (for instance, the property of being invariant with respect to the Walsh–Fourier transform) and, in addition, is invariant with

Abstract A differential inclusion whose right-hand side is the sum of two set-valued mappings in a separable Banach space is considered. The values of the first mapping are bounded and closed but not necessarily convex, and this mapping is Lipschitz continuous in the phase variable. The values of the second one are closed, and this mapping has mixed semicontinuity properties: given any phase point

Abstract Interpolation inequalities play an important role in the study of PDEs and their applications. There are still some interesting open questions and problems related to integral estimates and regularity of solutions to elliptic and/or parabolic equations. The main purpose of our work is to provide an important observation concerning the \(L^p\)-boundedness property in the context of interpolation

Abstract We prove the polynomiality of the bigraded ring \(J_{*,*}^{w, W}(F_4)\) of weak Jacobi forms for the root system \(F_4\) which are invariant with respect to the corresponding Weyl group. This work is a continuation of a joint article with V. A. Gritsenko, where the structure of the algebras of weak Jacobi forms related to the root systems of \(D_n\) type for \(2\leqslant n \leqslant 8\) was

Abstract A complete description of indecomposable characters of the infinite symmetric inverse semigroup is given. The method essentially uses the decomposition of the elements of this semigroup into a product of independent quasi-cycles and the multiplicativity theorem. Realizations of all factor representations of finite type are constructed.

Abstract A weight system is a function on chord diagrams that satisfies the so-called four-term relations. Vassiliev’s theory of finite-order knot invariants describes these invariants in terms of weight systems. In particular, there is a weight system corresponding to the colored Jones polynomial. This weight system can be easily defined in terms of the Lie algebra \(\mathfrak{sl}_2\), but this definition

Abstract In this paper we propose a generalization of Krichever’s algebraic-geometric construction of orthogonal coordinate systems in a flat space. In the theory of integrable systems of hydrodynamic type a fundamental role is also played by orthogonal coordinates in some special nonflat spaces. The most important class of such spaces is given by metrics of submanifolds in flat spaces that have flat

Abstract An elliptic fourth-order differential operator \(A_\varepsilon\) on \(L_2(\mathbb{R}^d;\mathbb{C}^n)\) is studied. Here \(\varepsilon >0\) is a small parameter. It is assumed that the operator is given in the factorized form \(A_\varepsilon = b(\mathbf{D})^* g(\mathbf{x}/\varepsilon) b(\mathbf{D})\), where \(g(\mathbf{x})\) is a Hermitian matrix-valued function periodic with respect to some

We consider the complex interpolation method in the context of protoquantum spaces. We apply it to construct an ℒp-protoquantization of an arbitrary normed space for 1 < p < ∞.

We describe the location of the essential spectrum of one-dimensional Dirac operators with singular potentials supported on discrete sets in ℝ in terms of limit operators.

We give a new formula for the zeta determinant of a Sturm-Liouville operator on a line segment.

The paper considers the classical Bernoulli scheme, that is, a sequence of independent random variables identically distributed with respect to the Lebesgue measure m on the interval [0,1]. The space of realizations of this scheme is the infinite-dimensional cube \({\mathcal{X}} = ({[0,1]^{\mathbb{N}}},\mu )\) with Lebesgue measure μ = mℕ. It is proved that there exists a function k(·): (0, 1) → ℝ

Let V1, …, Vn be finite-dimensional spaces of smooth functions on a smooth n-manifold X. We determine a relationship between the average number of solutions to systems of equations {fi = ai ∣ fi ∈ Vi, ai ∈ ℝ, i =1, …, n} and mixed volumes of convex bodies. To this end, assuming the spaces Vi to be normed, we construct (1) measures on the spaces of systems of equations and (2) Banach convex bodies in

We consider two examples of a fully decodable combinatorial encoding of Bernoulli schemes: the encoding via Weyl simplices and the much more complicated encoding via the RSK (Robinson-Schensted-Knuth) correspondence. In the first case, decodability is quite a simple fact, while in the second case, this is a nontrivial result obtained by D. Romik and P. Sniady and based on [2], [12], and other papers

We show that the spectrum of the Schrödinger operator H = −Δ + V in a smooth cylinder with Robin boundary condition ∂vu = σu is purely absolutely continuous, assuming that the coefficients V and σ are periodic in the axial directions.

The paper deals with a three-dimensional family of diffusion processes on an infinite-dimensional simplex. These processes were constructed by Borodin and Olshanski in 2009 and 2010, and they include, as limit objects, the infinitely-many-neutral-allels diffusion model constructed by Ethier and Kurtz in 1981 and its extension found by Petrov in 2009. Each process X in our family possesses a unique

It is proved that any finite-dimensional Lie algebra over an algebraically closed field K of characteristic 0 can be embedded (realized) as a transitive Lie subalgebra of the Lie algebra of polynomial vector fields on the space Kn. The same is also proved for arbitrary real Lie algebras and in some other cases.

Let Ω be a C1,s bounded domain (s > 1/2) in ℝd, and let \({{\cal A}^\varepsilon } = - {\rm{div}}\;A(x,x/\varepsilon )\nabla \) be a matrix elliptic operator on Ω with Dirichlet boundary condition. We suppose that ε is small and the function A is Lipschitz in the first variable and periodic in the second one, so the coefficients of \({{\cal A}^\varepsilon }\) are locally periodic. For μ in the resolvent

A self-adjoint strongly elliptic second-order differential operator Aε on L2(ℝd;ℂn) is considered. It is assumed that the coefficients of Aε are periodic and depend on x/ε, where ε > 0 is a small parameter. Approximations for the operators cos(A 1/2ε τ) and A 1/2ε sin(A 1/2ε τ) in the norm of operators from the Sobolev space Hs(ℝd;ℂn) to L2(ℝd;ℂn) (for appropriate s) are obtained. Approximation with

The paper considers the Schrödinger equation with an additional linear potential on the entire real line. A transformation operator with a condition at −∞ is constructed. The Gelfand-Levitan integral equation is obtained on the half-line (−∞, x).

Geremia and Sullivan [Ann. Math Pure Appl. 127 (1981), 231–251] gave a necessary and sufficient condition for an ℓp-product of spaces to be 2-uniformly rotund. We extend this result to k-uniform rotundity for any integer k > 1. The nonreflexive, uniformly nonoctahedral Banach space \(\widetilde{X}\) constructed by James [Israel J. Math. 18 (1974), 145–155] does not contain arbitrarily close copies

We prove that the connected sum of two links is quasipositive if and only if each summand is quasipositive. The proof is based on the filling disk technique.

Conditions under which the system of dilations and translations of a function f in a symmetric space X is a representing system in X are found. Previously a similar result was known only for the spaces Lp, 1 ⩽ p < ∞. In particular, each function f with \(\int_0^1 {f(t)dt \ne 0} \) in a Lorentz space Λϕ generates an absolutely representing system of dilations and translations in this space if and only

We show that the extremal extrapolation spaces for an operator with any function ξ characterizing the growth of the operator norms are the sum and the intersection of spaces whose norms depend on ξ and are written out explicitly.

Basic results for nonlinear operators are given. These results include nonlinear versions of the classical uniform boundedness theorem and Hahn-Banach theorem. Further, mappings of a metrizable space into another normed space can belong to some normed spaces if one defines suitable norms.

Given one-dimensional determinantal point processes induced by orthogonal projections with integrable kernels satisfying a certain growth condition, it is proved that their conditional measures with respect to the configuration in the complement of a compact interval are orthogonal polynomial ensembles with explicitly found weights. Examples include the sine-process and the process with Bessel kernel

We prove that the sigma functions of Weierstrass (g = 1) and Klein (g = 2) are the unique solutions (up to multiplication by a complex constant) of the corresponding systems of 2g linear differential heat equations in a nonholonomic frame (for a function of 3g variables) that are holomorphic in a neighborhood of at least one point where all modular variables vanish. We also show that all local holomorphic

For any small ε > 0, a two-dimensional elastic waveguide is constructed such that λe = ε4 is the only eigenvalue in the vicinity of the lower bound λ† = 0 of the continuous spectrum. This result is rather unexpected, because an acoustic waveguide (the Neumann problem for the Laplace operator) with an arbitrary small localized perturbation cannot support a trapped mode at a low frequency.

Compact pseudodifferential operators whose symbol fails to be smooth with respect to x on a given set are considered. Conditions under which Weyl’s law of spectral asymptotics remains valid for such operators are obtained. The results are applied to operators with symbols such that their order of decay as |ξ| → ∞ is a nonsmooth function of x.

We prove the attainability of the best constant in the fractional Hardy-Sobolev inequality with a boundary singularity for the spectral Dirichlet Laplacian. The main assumption is the average concavity of the boundary at the origin. A similar result has been proved earlier for the conventional Hardy-Sobolev inequality.

We study the center of the universal enveloping algebra of the strange Lie superalgebra q(N). We obtain an analogue of the well-known Perelomov-Popov formula [6] for the central elements of this algebra—an expression of the central characters through the highest weight parameters.

It is proved that any Bethe subalgebra corresponding to a regular semisimple element in a Yangian is a maximal commutative subalgebra and, moreover, the centralizer of its quadratic part. As a consequence, a description of such subalgebras as the traces of the R-matrix over all finite-dimensional representations of the Yangian is obtained.

Rules for calculating the densities of Borel measures which are absolutely continuous with respect to a positive nonatomic Radon measure are considered. The Borel measures are generated by composite functions which depend on continuous functions of bounded variation defined on an interval. Questions related to the absolute continuity of Borel measures generated by composite functions with respect to

We compute the Coulomb branch of a multiloop quiver gauge theory for the quiver with a single vertex, r loops, one-dimensional framing, and dim V = 2. We identify it with a Slodowy slice in the nilpotent cone of the symplectic Lie algebra of rank r. Hence it possesses a symplectic resolution with 2r fixed points with respect to a Hamiltonian torus action. We also identify its flavor deformation with

This paper describes a class of spectral curves and gives explicit formulas for the Darboux coordinates of the Hitchin systems of types Al, Bl, and Cl on hyperelliptic curves. The current state of the problem in the case of the systems of type Dl is described.

S. V. Chmutov, M. E. Kazarian, and S. K. Lando have recently introduced a class of graph invariants, which they called shadow invariants (these invariants are graded homomorphisms from the Hopf algebra of graphs to the Hopf algebra of polynomials in infinitely many variables). They proved that, after an appropriate rescaling of the variables, the result of the averaging of almost every such invariant

The variational problem on the equilibrium of a two-phase elastic medium is studied for conditions of the Signorini type. The strong convergence of its solutions to single-phase states as the temperature unboundedly increases is proved. A sufficient condition for the existence of phase transition temperatures for one-sided problems is given. A one-dimensional example illustrating the results is presented

We consider generalized Hausdorff operators and introduce the notion of the symbol of such an operator. Using this notion, we describe, under some natural conditions, the structure and investigate important properties (such as invertibility, spectrum, and norm) of normal generalized Hausdorff operators on Lebesgue spaces over ℝn. As an example we consider Cesàro operators.

Relative projection constants and strong unicity constants for a certain class of projection operators on the space l 2 n∞ are found. The maximum values of strong unicity constants are calculated for the projection operators with unit norm on certain codimension-2 subspaces formed by using hyperplanes in l 2 n∞ .

In this paper we strengthen the result of Fomin and Zelevinsky (2002) on the Laurent phenomenon for Somos-4 and Somos-5 sequences.

A new Caristi-type inequality is considered and Caristi’s fixed point theorem for mappings of complete metric spaces is developed (in both the single- and set-valued cases). On the basis of this development mappings of complete metric spaces which are contractions with respect to a function of two vector arguments are studied. This function is not required to be a metric or even a continuous function

Let T be a self-adjoint operator on a Hilbert space H with domain \(\mathscr{D}(T)\). Assume that the spectrum of T is contained in the union of disjoint intervals Δk = [α2k−1,α2k], k ∈ ℤ, the lengths of the gaps between which satisfy the inequalities$${\alpha _{2k + 1}} - {\alpha _{2k}}\geqslant b{\rm{|}}{\alpha _{2k + 1}} + {\alpha _{2k}}{{\rm{|}}^p}\;\;\;\;{\rm{for}}\;{\rm{some}}\;\;{\rm{b}} > 0

We give a complete solution of the inverse problem for finite Jacobi operators with matrix-valued coefficients.

We consider arbitrary noncompact hyperbolic Riemann surfaces of finite area. For such surfaces, we obtain identities relating the discrete spectrum of the Laplace operator to the resonance spectrum (formed by the poles of the scattering matrix). These identities depend on the choice of a test function. We indicate a class of admissible test functions and consider two examples corresponding to specific

This paper is devoted to the classical problem of the inversion of ultraelliptic integrals given by basic holomorphic differentials on a curve of genus 2. Basic solutions F and G of this problem are obtained from a single-valued 4-periodic meromorphic function on the Abelian covering W of the universal hyperelliptic curve of genus 2. Here W is the nonsingular analytic curve W = {u =(u1, u3) ∈ ℂ2: σ(u)

The asymptotic behavior at large times of the solution of the Cauchy problem for the Airy equation—a third-order evolutionary equation—is established. We assume that the initial function is locally Lebesgue integrable and has a power-law asymptotics at infinity. For the solution in the form of a convolution integral with the Airy function, we use the auxiliary parameter method and the regularization

We consider foliations of compact complex manifolds by analytic curves. We suppose that the line bundle tangent to the foliation is negative. We show that, in the generic case, there exists a finitely smooth homomorphism holomorphic on the fibers and mapping fiberwise the manifold of universal coverings over the leaves passing through a given transversal B onto some domain with continuous boundary

We obtain a qualitative characterization of the convergence rate of the averages (with respect to the Margulis measure) of C2 functions over the iterations of domains in unstable manifolds of a topologically mixing C3 Anosov diffeomorphism with oriented invariant foliations. For this purpose, we extend the constructions of Margulis and Bufetov and introduce holonomy invariant families of finitely additive

Let Ω be a metric space. By At we denote the metric neighborhood of radius t of a set A ⊂ Ω and by \(\mathfrak{D}\), the lattice of open sets in Ω with partial order ⊆ and order convergence. The lattice of \(\mathfrak{D}\)-valued functions of t ∈ (0, ∞) with pointwise partial order and convergence contains the family I\(\mathfrak{D}\) = {A(·)| A(t) = At, A ∈ \(\mathfrak{D}\)}. Let ̃Ω be the set of

We suggest a combinatorial method for encoding continuous symbolic dynamical systems. We transform a continuous phase space, the infinite-dimensional cube, into the path space of a tree, and the shift corresponds to a transformation which we called “transfer.” The central problem is that of distinguishability: does the encoding distinguishes between almost all points of the space? The main result says

Several necessary conditions for the topological flatness of Banach modules are given. The main result is as follows: a Banach module over a relatively amenable Banach algebra which is topologically flat as a Banach space is topologically flat as a Banach module. Finally examples of topologically flat modules among classical modules of analysis are given.

Let M be a subharmonic function in a domain D ⊂ ℂn with Riesz measure νM, and let Z ⊂ D. As was shown in the first of the preceding papers, if there exists a holomorphic function f ≠ 0 in D such that f(Z) = 0 and |f| ⩽ exp M on D, then one has a scale of integral uniform upper bounds for the distribution of the set Z via νM. The present paper shows that for n = 1 this result "almost has a converse