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In this paper we consider weighted polynomial approximation on unbounded multidimensional domains in the spirit of the weighted version of the Weierstrass trigonometric theorem according to which every continuous function on the real line with equal finite limits at ± ∞ is a uniform limit on R of weighted algebraic polynomials of degree 2 n with varying weights ( 1 + t 2 ) − n . We will verify a similar statement in the multivariate setting for a general class of convex weights. We also consider the similar problem of multivariate polynomial approximation with varying weights for some typical non convex weights. In case of non convex weights of the form w α ( x ) ≔ ( 1 + | x 1 | α + . . . + | x d | α ) 1 α , 0 α 1 in order for weighted polynomial approximation to hold for a given continuous function it is necessary that the function vanishes on a certain exceptional set consisting of all coordinate hyperplanes and ∞ . Moreover, in case of rational α this condition is also sufficient for weighted polynomial approximation to hold.

One of the most influential versions of the classical Schwarz–Pick Lemma is probably that of Ahlfors. Pulling back a conformal semimetric on a Riemann surface under any holomorphic map from the open unit disk equipped with a Poincare metric, the curvature of which is assumed to bound from above the curvature of the Riemann surface, he successfully showed that a conformal semimetric to be compared with the Poincare metric is obtained. In the present paper, we give a comparison theorem between two conformal semimetrics of variable curvature in the same spirit. Our main theorem is a local one by its nature, but global results can be derived therefrom.

In this paper, we first study generalizations of Fujita vanishing theorems for q-ample divisors. We then apply them to study positivity of subvarieties with nef normal bundle in the sense of intersection theory. After Ottem's work on ample subschemes, we introduce the notion of a nef subscheme, which generalizes the notion of a subvariety with nef normal bundle. We show that restriction of a pseudoeffective (resp. big) divisor to a nef subvariety is pseudoeffective (resp. big). We also show that ampleness and nefness are transitive properties. We define the weakly movable cone as the cone generated by the pushforward of cycle classes of nef subvarieties via proper surjective maps. This cone contains the movable cone and shares similar intersection-theoretic properties with it, thanks to the aforementioned properties of nef subvarieties. On the other hand, we prove that if Y ⊂ X is an ample subscheme of codimension r and D | Y is q-ample, then D is ( q + r ) -ample. This is analogous to a result proved by Demailly-Peternell-Schneider and Kuronya.

The exact boundary controllability for hyperbolic systems can not be realized generally on a network with loops (see [16] ). In this paper we consider the exact boundary controllability of nodal profile on a network with loops. Precisely speaking, on a network with a triangle-like loop, when nodal profiles are given at various kinds of nodes, different constructive methods can be used to get the corresponding exact boundary controllability of nodal profile for Saint-Venant system by means of boundary controls acting on suitable nodes, respectively. This reveals that the exact boundary controllability of nodal profile is quite different from the usual exact boundary controllability, and has relatively distinctive behaviors and characters.

We make systematic developments on Lawson-Osserman constructions relating to the Dirichlet problem (over unit disks) for minimal surfaces of high codimension in their 1977 Acta paper. In particular, we show the existence of boundary functions for which infinitely many analytic solutions and at least one nonsmooth Lipschitz solution exist simultaneously. This newly-discovered amusing phenomenon enriches the understanding on the Lawson-Osserman philosophy., Supercedes arXiv:1610.08162. To appear in the Journal de Math\'ematiques Pures et Appliqu\'ees

We prove a partial fraction decomposition of a quotient of two functions E α ( i t x ) and I α ( i t ) which are defined in terms of the Bessel functions J α and J α + 1 of the first kind. This expansion leads naturally to the introduction of an orthonormal system with respect to the measure | x | 2 α + 1 d x 2 α + 1 Γ ( α + 1 ) in [ − 1 , 1 ] , which we call the Fourier–Dunkl system of the second kind. Euler–Dunkl polynomials E n , α ( x ) of degree n are defined by considering E α ( t x ) ∕ I α ( t ) as a generating function. It is shown that the sum ∑ m = 1 ∞ 1 ∕ j m , α 2 k , where j m , α are the positive zeros of J α , is equal (up to an explicit factor) to E 2 k − 1 , α ( 1 ) . For α = 1 ∕ 2 this leads to classical results of Euler since the function E 1 ∕ 2 ( x ) is the exponential function and E n , 1 ∕ 2 ( x ) are (essentially) the Euler polynomials. In the second part of the paper a sampling theorem of Whittaker–Shannon–Kotel’nikov type is established which is strongly related to the above-mentioned partial decomposition and which holds for all functions in the Payley–Wiener space defined by the Dunkl transform in [ − 1 , 1 ] .

In this paper we investigate the extent to which the Lovasz Local Lemma (an important tool in probabilistic combinatorics) can be adapted for the measurable setting. In most applications, the Lovasz Local Lemma is used to produce a function f : X → Y with certain properties, where X is some underlying combinatorial structure and Y is a (typically finite) set. Can this function f be chosen to be Borel or μ -measurable for some probability Borel measure μ on X (assuming that X is a standard Borel space)? In the positive direction, we prove that if the set of constraints put on f is, in a certain sense, “locally finite,” then there is always a Borel choice for f that is “ e -close” to satisfying these constraints, for any e > 0 . Moreover, if the combinatorial structure on X is “induced” by the [ 0 ; 1 ] -shift action of a countable group Γ, then, even without any local finiteness assumptions, there is a Borel choice for f which satisfies the constraints on an invariant conull set (i.e., with e = 0 ). A direct corollary of our results is an upper bound on the measurable chromatic number of the graph G n generated by the shift action of the free group F n that is asymptotically tight up to a factor of at most 2 (which answers a question of Lyons and Nazarov). On the other hand, our result for structures induced by measure-preserving group actions is, at least for amenable groups, sharp in the following sense: a probability measure-preserving action of a countably infinite amenable group satisfies the measurable version of the Lovasz Local Lemma if and only if it admits a factor map to the [ 0 ; 1 ] -shift action. To prove this, we combine the tools of the Ornstein–Weiss theory of entropy for actions of amenable groups with concepts from computability theory, specifically, Kolmogorov complexity.

Corresponding to the Legendre ellipsoid and the LYZ ellipsoid, two new sine ellipsoids are introduced in this paper. These four ellipsoids are closely related in the Pythagorean relation and duality. Several volume inequalities and the valuation properties are obtained for two new ellipsoids.

Let $W$ be a Coxeter group. The goal of the paper is to construct new Hopf algebras that contain Hecke algebras $H_{\bf q}(W)$ as (left) coideal subalgebras. Our Hecke-Hopf algebras ${\bf H}(W)$ have a number of applications. In particular they provide new solutions of quantum Yang-Baxter equation and lead to a construction of a new family of endo-functors of the category of $H_{\bf q}(W)$-modules. Hecke-Hopf algebras for the symmetric group are related to Fomin-Kirillov algebras, for an arbitrary Coxeter group $W$ the "Demazure" part of ${\bf H}(W)$ is being acted upon by generalized braided derivatives which generate the corresponding (generalized) Nichols algebra., Comment: AMSLaTex 67 pages, to appear in Advances in Mathematics

In this paper, we study the topological structure of the Hahn field F whose elements are functions from the additive abelian group of rational numbers Q to the real numbers field R , with well-ordered support. After reviewing the algebraic and order structures of the field F , we introduce different vector topologies on F that are induced by families of semi-norms, all of which are weaker than the order or valuation topology. We compare those vector topologies and we identify the weakest one which we denote by τ w and whose properties are similar to those of the weak topology on the Levi-Civita field (Shamseddine, 2010). In particular, we state and prove a convergence criterion for power series in F , τ w that is similar to that for power series on the Levi-Civita field in its weak topology (Shamseddine, 2013).

Let f = h + g ‾ be a normalized and sense-preserving convex harmonic mapping in the unit disk D . In a recent paper, Ponnusamy and Sairam Kaliraj conjectured that there is a θ ∈ [ 0 , 2 π ) such that the function h + e i θ g is convex in D . In this article, we first disprove a more flexible conjecture: “Let f = h + g ‾ be a convex harmonic mapping in the disk D . Then there is a θ ∈ [ 0 , 2 π ) such that the function h + e i θ g is starlike in D ”. In addition, we present an example to show that there exists a harmonic automorphism f = h + g ‾ of a disk such that the function h + e i θ g is convex in only one direction for θ ≠ 0 , and that the analytic function h + g is not starlike therein. The article concludes with a new conjecture.

We study the class P of positive linear functionals φ on L ∞ ( [ 1 , ∞ ) ) for which φ ( f ) = α if lim x → ∞ 1 x ∫ 1 x f ( t ) d t = α . The semigroup of translations f ( x ) ↦ f ( r x ) on L ∞ ( [ 1 , ∞ ) ) , where r ∈ [ 1 , ∞ ) , plays a crucial role in the study of P . In particular, we give three different expressions of their extremal values, which can be considered main results of this paper. We also study linear functionals on l ∞ , the set of all real-valued bounded functions on natural numbers N , which extend Cesaro mean and give similar results about their extremal values, including a functional analytic proof of the classical result of Polya.

The study of the restricted isometry property (RIP) of corrupted random matrices is particularly important in the field of compressed sensing (CS) with corruptions. If a matrix still satisfies the RIP after that a certain portion of rows are erased, then we say that this matrix has the strong restricted isometry property (SRIP). In the field of compressed sensing, random matrices which satisfy certain moment conditions are of particular interest. Among these matrices, those with entries generated from i.i.d. Gaussian or symmetric Bernoulli random variables are often typically considered. Recent studies have shown that matrices with entries generated from i.i.d. Gaussian random variables satisfy the SRIP under arbitrary erasure of rows with high probability. In this paper, we study the erasure robustness property of Bernoulli random matrices. Our main result shows that with overwhelming probability, the SRIP holds for Bernoulli random matrices. Moreover, our analysis leads to a robust version of the famous Johnson–Lindenstrauss lemma for Bernoulli random matrices.

Let F Θ = G ∕ P Θ be a generalized flag manifold, where G is a real non-compact semi-simple Lie group and P Θ a parabolic subgroup. A classical result says the Schubert cells, which are the closure of the Bruhat cells, endow F Θ with a cellular CW structure. In this paper we exhibit explicit parametrizations of the Schubert cells by closed balls (cubes) in R n and use them to compute the boundary operator ∂ for the cellular homology. We recover the result obtained by Kocherlakota [1995], in the setting of Morse Homology, that the coefficients of ∂ are 0 or ± 2 (so that Z 2 -homology is freely generated by the cells). In particular, the formula given here is more refined in the sense that the ambiguity of signals in the Morse–Witten complex is solved.

$\newcommand{\poly}{_{\operatorname{poly}}^{\bullet}}\newcommand{\td}{(\operatorname{td}_{L/A}^{\nabla})^{\frac{1}{2}}}\newcommand{\cx}[1]{\operatorname{tot}\big(\Gamma(\Lambda^\bullet A^\vee)\otimes_R\mathcal{#1}\poly\big)}\newcommand{\cy}[1]{\mathbb{H}^\bullet_{\operatorname{CE}}(A,\mathcal{#1}\poly)}$Kontsevich's formality theorem states that there exists an $L_\infty$ quasi-isomorphism from the dgla $T\poly(M)$ of polyvector fields on a smooth manifold $M$ to the dgla $D\poly(M)$ of polydifferential operators on $M$, which extends the classical Hochschild--Kostant--Rosenberg map. In this paper, we extend Kontsevich's formality theorem to Lie pairs, a framework which includes a range of diverse geometric contexts such as complex manifolds, foliations, and $\mathfrak{g}$-manifolds. The spaces $\cx{T}$ and $\cx{D}$ associated with a Lie pair $(L,A)$ each carry an $L_\infty$ algebra structure canonical up to $L_\infty$ isomorphism. These two spaces serve as replacements for the spaces of polyvector fields and polydifferential operators, respectively. Their corresponding cohomology groups $\cy{T}$ and $\cy{D}$ admit canonical Gerstenhaber algebra structures. We establish the following formality theorem for Lie pairs: there exists an $L_\infty$ quasi isomorphism from $\cx{T}$ to $\cx{D}$ whose first Taylor coefficient is equal to $\operatorname{hkr}\circ\td$. Here $\td$ acts on $\cx{T}$ by contraction. Furthermore, we prove a Kontsevich--Duflo type theorem for Lie pairs: the Hochschild--Kostant--Rosenberg map twisted by the square root of the Todd class of the Lie pair $(L,A)$ is an isomorphism of Gerstenhaber algebras from $\cy{T}$ to $\cy{D}$. As applications, we establish formality theorems and Kontsevich--Duflo type theorems for complex manifolds, foliations, and $\mathfrak{g}$-manifolds. In the case of complex manifolds, we recover the Kontsevich--Duflo theorem of complex geometry., Comment: 55 pages, several typos corrected, some references added, some minor cosmetic changes in the presentation

In this paper we characterize the surjective linear variation norm isometries on JB-algebras. Variation norm isometries are precisely the maps that preserve the maximal deviation, the quantum analogue of the standard deviation, which plays an important role in quantum statistics. Consequently, we characterize the Hilbert's metric isometries on cones in JB-algebras., Comment: 21 pages

Motivated by analogies with basic density theorems in analytic number theory, we introduce a notion (and variations) of the homological density of one space in another. We use Weil's number field/function field analogy to predict coincidences for limiting homological densities of various sequences Z n ( d 1 , … , d m ) ( X ) of spaces of 0-cycles on manifolds X. The main theorem in this paper is that these topological predictions, which seem strange from a purely topological viewpoint, are indeed true. One obstacle to proving such a theorem is the combinatorial complexity of all possible “collisions” of points. This problem does not arise in the simplest (and classical) case ( m , n ) = ( 1 , 2 ) of configuration spaces. To overcome this obstacle we apply the Bjorner–Wachs theory of lexicographic shellability from algebraic combinatorics.

In this paper, we study smooth complex projective varieties X such that some exterior power ⋀ r T X of the tangent bundle is strictly nef. We prove that such varieties are rationally connected. We also classify the following two cases. If T X is strictly nef, then X isomorphic to the projective space P n . If ⋀ 2 T X is strictly nef and if X has dimension at least 3, then X is either isomorphic to P n or a quadric Q n .

Given an ample action of an inverse semigroup on a locally compact and Hausdorff topological space, we study the ideal structure of the crossed product algebra associated with it. By developing a theory of induced ideals, we manage to prove that every ideal in the crossed product algebra may be obtained as the intersection of ideals induced from isotropy group algebras. This can be interpreted as an algebraic version of the Effros-Hahn conjecture. Finally, as an application of our result, we study the ideal structure of a Steinberg algebra associated with an ample groupoid by interpreting it as an inverse semigroup crossed product algebra., Comment: This paper has resulted from the author's work as a PhD student in Florianopolis under the advice of professor Ruy Exel. arXiv admin note: substantial text overlap with arXiv:1605.07540 by other authors

In this paper, we construct a class of weighted Bergman spaces such that they can generate H ∞ in the sense of Mobius invariance. H ∞ is also equal to the intersection of these spaces. Applying the relation between H ∞ and these spaces, we show that the characterization via higher order derivatives does not hold for some of these weighted Bergman spaces.

In this paper, we prove that the spectral curve Γ n of the generalized Lame equation with the Treibich–Verdier potential y ″ ( z ) = [ ∑ k = 0 3 n k ( n k + 1 ) ℘ ( z + ω k 2 | τ ) + B ] y ( z ) , n k ∈ Z ≥ 0 can be embedded into the symmetric space Sym N E τ of the N-th copy of the torus E τ , where N = ∑ n k . This embedding induces an addition map σ n ( ⋅ | τ ) from Γ n onto E τ . The main result is to prove that the degree of σ n ( ⋅ | τ ) is equal to ∑ k = 0 3 n k ( n k + 1 ) / 2 . This is the first step toward constructing the pre-modular form associated with this generalized Lame equation.

It seems that the index theory for non-compact spaces has found its ultimate formulation in the realm of coarse spaces and K-theory of related operator algebras. Relative and partitioned index theorems may be mentioned as two important and interesting examples of this program. In this paper we formulate a combination of these two theorems and establish a partitioned-relative index theorem.

Let X be a variety with an action by an algebraic group G. In this paper we discuss various properties of G-equivariant D -modules on X, such as the decompositions of their global sections as representations of G (when G is reductive), and descriptions of the categories that they form. When G acts on X with finitely many orbits, the category of equivariant D -modules is equivalent to the category of finite-dimensional representations of a finite quiver with relations. We describe explicitly these categories for irreducible G-modules X that are spherical varieties, and show that in such cases the quivers are almost always representation-finite (i.e. with finitely many indecomposable representations).

The Boussinesq a b c d system is a 4-parameter set of equations posed in R t × R x , originally derived by Bona, Chen and Saut [11] , [12] as first order 2-wave approximations of the incompressible and irrotational, two dimensional water wave equations in the shallow water wave regime, in the spirit of the original Boussinesq derivation [17] . Among many particular regimes, depending each of them in terms of the value of the parameters ( a , b , c , d ) present in the equations, the generic regime is characterized by the setting b , d > 0 and a , c 0 . If additionally b = d , the a b c d system is Hamiltonian. The equations in this regime are globally well-posed in the energy space H 1 × H 1 , provided one works with small solutions [12] . In this paper, we investigate decay and the scattering problem in this regime, which is characterized as having (quadratic) long-range nonlinearities, very weak linear decay O ( t − 1 / 3 ) because of the one dimensional setting, and existence of non scattering solutions (solitary waves). We prove, among other results, that for a sufficiently dispersive a b c d systems (characterized only in terms of parameters a , b and c), all small solutions must decay to zero, locally strongly in the energy space, in proper subset of the light cone | x | ≤ | t | . We prove this result by constructing three suitable virial functionals in the spirit of works [27] , [28] , and more precisely [42] (valid for the simpler scalar “good Boussinesq” model), leading to global in time decay and control of all local H 1 × H 1 terms. No parity nor extra decay assumptions are needed to prove decay, only small solutions in the energy space.

The Bialynicki-Birula decomposition of the space of λ-connections restricts to the Morse stratification on the moduli space of Higgs bundles and to the partial oper stratification on the de Rham moduli space of holomorphic connections. For both the Morse and partial oper stratifications, every stratum is a holomorphic Lagrangian fibration over a component of the space of complex variations of Hodge structure. In this paper, we generalize known results for the Hitchin section and the space of opers to arbitrary strata. These include the following: a biholomorphic identification of the fibers of the two strata over a stable variation of Hodge structure via the “ħ-conformal limit” of Gaiotto, a proof that the fibers of the Morse and partial oper stratifications are transverse at the base point, and an explicit parametrization of the fibers as half-dimensional affine spaces.

In arxiv:1602.04254, we have defined polynomial Witt vectors functor from vector spaces over a perfect field $k$ of positive characteristic $p$ to abelian groups. In this paper, we use polynomial Witt vectors to construct a functorial Hochschild-Witt complex $WCH_*(A)$ for any associative unital $k$-algebra $A$, with homology groups $WHH_*(A)$. We prove that the group $WHH_0(A)$ coincides with the group of non-commutative Witt vectors defined by Hesselholt, while if $A$ is commutative, finitely generated, and smooth, the groups $WHH_i(A)$ are naturally identified with the terms $W\Omega^i_A$ of the de Rham-Witt complex of the spectrum of $A$., Comment: 64 pages, LaTeX2e

The Eichler-Shimura isomorphism relates holomorphic modular cusps forms of positive even integral weight to cohomology classes. The Haberland formula uses the cup product to give a cohomological formulation of the Petersson scalar product. In this paper we extend Haberland's formula to modular cusp forms of positive real weight. This relation is based on the cup product of an Eichler cocycle and a Knopp cocycle. We may also consider the cup product of two Eichler cocycles. In the classical situation this cup product is almost always zero. However we show evidence that for real weights this cup product may very well be non-trivial. We approach the question whether the cup product is a non-trivial coinvariant by duality with a space of entire modular forms. The cup product yields a bilinear map over C from pairs of holomorphic modular forms (not necessarily of the same weight, one of them may have large growth at the cusps) to coinvariants in infinite-dimensional modules. To investigate whether this bilinear map is non-trivial we test the result against entire modular forms of a suitable weight. Under some conditions on the weights, this leads to an explicit triple integral, which can be investigated numerically, thus providing evidence that the cup product is non-trivial at least in some situations.

Let $L$ be the generator of an analytic semigroup whose kernels satisfy Gaussian upper bounds and H\"older's continuity. Also assume that $L$ has a bounded holomorphic functional calculus on $L^2(\mathbb{R}^n)$. In this paper, we construct a frame decomposition for the functions belonging to the Hardy space $H_{L}^{1}(\mathbb{R}^n)$ associated to $L$, and for functions in the Lebesgue spaces $L^p$, $1, Comment: 37 pages, to appear in Journal of Approximation Theory

In this paper, we will study the maximality of functions and a new Cegrell class N m ( Ω ) which is between the classes F m ( Ω ) and E m ( Ω ) . We study the Dirichlet problem, the subsolution theorem and the stability theorem for this class.

In this paper, we show a stochastic expression for the radial processes of Brownian motions on RCD ⁎ ( K , N ) -spaces. It corresponds to the one on Riemannian manifolds. The expression holds for all starting points without exceptional sets. It can be extended beyond the hitting time to the reference point provided the reference point is sufficiently regular. We further prove that the regularity condition is satisfied for almost every reference point. Our results extend the comparison theorems over Alexandrov spaces proved in [36] , [29] .

For a prime p, we call a positive integer n a Frobenius p-number if there exists a finite group with exactly n subgroups of order p^a for some $a\ge 0$. Extending previous results on Sylow's theorem, we prove in this paper that every Frobenius p-number $n\equiv 1\pmod{p^2}$ is a Sylow p-number, i.e., the number of Sylow p-subgroups of some finite group. As a consequence, we verify that 46 is a pseudo Frobenius 3-number, that is, no finite group has exactly 46 subgroups of order 3^a for any $a\ge 0$., Comment: 6 pages, expository, to appear in Expo. Math

In this survey paper, we take the viewpoint of polar invariants to the local and global study of non-dicritical holomorphic foliation in dimension two and their invariant curves. It appears a characterization of second type foliations and generalized curve foliations as well as a description of the G S V -index in terms of polar curves. We also interpret the proofs concerning the Poincare problem with polar invariants.

Recently, a new partition function associated with Ramanujan's third order mock theta function ω ( q ) was discovered, and subsequently its overpartition analogue was introduced. In this paper, we prove an intriguing identity arising from the study of that analogue, which involves a double series of Hecke-Rogers type. In addition, two further identities will be given. Our proofs heavily rely on formulas from the work of Liu [12] .

This paper studies connections among observable sets, the observability inequality, the Holder-type interpolation inequality and the spectral inequality for the heat equation in R n . We present the characteristic of observable sets for the heat equation. In more detail, we show that a measurable set in R n satisfies the observability inequality if and only if it is γ-thick at scale L for some γ > 0 and L > 0 . We also build up the equivalence among the above-mentioned three inequalities. More precisely, we obtain that if a measurable set in R n satisfies one of these inequalities, then it satisfies others. Finally, we get some weak observability inequalities and weak interpolation inequalities where observations are made over a ball.

Abelian categories provide a self-dual axiomatic context for establishing homomorphism theorems (such as the isomorphism theorems and homological diagram lemmas) for abelian groups, and more generally, modules. In this paper we describe a self-dual context which allows one to establish the same theorems in the case of non-abelian group-like structures; the question of whether such a context can be found has been left open for seventy years. We also formulate and prove in our context a universal isomorphism theorem from which all other isomorphism theorems can be deduced.

The metric d ( A , B ) = tr A + tr B − 2 tr ( A 1 ∕ 2 B A 1 ∕ 2 ) 1 ∕ 2 1 ∕ 2 on the manifold of n × n positive definite matrices arises in various optimisation problems, in quantum information and in the theory of optimal transport. It is also related to Riemannian geometry. In the first part of this paper we study this metric from the perspective of matrix analysis, simplifying and unifying various proofs. Then we develop a theory of a mean of two, and a barycentre of several, positive definite matrices with respect to this metric. We explain some recent work on a fixed point iteration for computing this Wasserstein barycentre. Our emphasis is on ideas natural to matrix analysis.

This paper is devoted to the study of the deviation of the (random) average L 2 − error associated to the least-squares regressor over a family of functions F n (with controlled complexity) obtained from n independent, but not necessarily identically distributed, samples of explanatory and response variables, from the minimal (deterministic) average L 2 − error associated to this family of functions, and to some of the corresponding consequences for the problem of consistency. In the i.i.d. case, this specializes as classical questions on least-squares regression problems, but in more general cases, this setting permits a precise investigation in the direction of the study of nonasymptotic errors for least-squares regression schemes in nonstationary settings, which we motivate providing background and examples. More precisely, we prove first two nonasymptotic deviation inequalities that generalize and refine corresponding known results in the i.i.d. case. We then explore some consequences for nonasymptotic bounds of the error both in the weak and the strong senses. Finally, we exploit these estimates to shed new light into questions of consistency for least-squares regression schemes in the distribution-free, nonparametric setting. As an application to the classical theory, we provide in particular a result that generalizes the link between the problem of consistency and the Glivenko-Cantelli property, which applied to regression in the i.i.d. setting over non-decreasing families ( F n ) n of functions permits to create a scheme which is strongly consistent in L 2 under the sole (necessary) assumption of the existence of functions in ∪ n F n which are arbitrarily close in L 2 to the corresponding regressor.

We consider the type I multiple orthogonal polynomials (MOPs) ( A n , m , B n , m ) , deg ⁡ A n , m ≤ n − 1 , deg ⁡ B n , m ≤ m − 1 , and type II MOPs P n , m , deg ⁡ P n , m = n + m , satisfying non-hermitian orthogonality with respect to the weight e − z 3 on two unbounded contours γ 1 and γ 2 on C , with (in the case of type II MOPs) n conditions on γ 1 and m on γ 2 . Under the assumption that n , m → ∞ , n n + m → α ∈ ( 0 , 1 ) we find the detailed (rescaled) asymptotics of A n , m , B n , m and P n , m on C , and describe the phase transitions of this limit behavior as a function of α. This description is given in terms of the vector critical measure μ → α = ( μ 1 , μ 2 , μ 3 ) , the saddle point of an energy functional comprising both attracting and repelling forces. This critical measure is characterized by a cubic equation (spectral curve), and its components μ j live on trajectories of a canonical quadratic differential ϖ on the Riemann surface of this equation. The structure of these trajectories and their deformations as functions of α was object of study in our previous paper [42] , and some of the present results strongly rely on the analysis carried out there. We conclude that the asymptotic zero distribution of the polynomials A n , m and P n , m are given by appropriate combinations of the components μ j of the vector critical measure μ → α . However, in the case of the zeros of B n , m the behavior is totally different, and can be described in terms of the balayage of the signed measure μ 2 − μ 3 onto certain curves on the plane. These curves are constructed with the aid of the canonical quadratic differential ϖ, and their topology has three very distinct characters, depending on the value of α, and are obtained from the critical graph of ϖ. Once the trajectories and vector critical measures are studied, the main asymptotic technical tool is the Deift-Zhou nonlinear steepest descent analysis of a 3 × 3 matrix-valued Riemann–Hilbert problem characterizing both ( A n , m , B n , m ) and P n , m , which allows us to obtain the limit behavior of both types of MOPs simultaneously. We illustrate our findings with results of several numerical experiments, explain the computational methodology, and formulate some conjectures and empirical observations based on these experiments.

Recently, the convergence–divergence properties of the Berrut rational interpolant (Berrut, 1988) were studied in the case of equidistant nodes (Mastroianni and Szabados, 2017). A very general class called “well-spaced nodes” was introduced in Bos et al. (2013), a class which includes essentially any distribution of nodes that satisfies a particular regularity condition, such as equidistant nodes, Chebyshev nodes as well as extended Chebyshev nodes. In this paper we show that results obtained in Mastroianni and Szabados, (2017) for the equidistant nodes hold more generally for the class of well-spaced nodes, with the restriction that the end points of the definition interval are nodes.

The paper is concerned with the scope of semi-intuitionistic set theories that relate to various foundational stances. It also provides a proof for a second conjecture of Feferman’s that relates the concepts for which the law of excluded middle obtains to those that are absolute with regard to the relevant test structures, or more precisely of Δ 1 complexity. The latter is then used to show that a plethora of statements is indeterminate with respect to various semi-intuitionistic set theories.

In this paper we elucidate the connection between various notions of differentiability in the Wasserstein space: some have been introduced intrinsically (in the Wasserstein space, by using typical objects from the theory of Optimal Transport) and used by various authors to study gradient flows, Hamiltonian flows, and Hamilton–Jacobi equations in this context. Another notion is extrinsic and arises from the identification of the Wasserstein space with the Hilbert space of square-integrable random variables on a non-atomic probability space. As a consequence, the classical theory of well-posedness for viscosity solutions for Hamilton–Jacobi equations in infinite-dimensional Hilbert spaces is brought to bear on well-posedness for Hamilton–Jacobi equations in the Wasserstein space.

For a connected quasi-split reductive algebraic group G over a field k, which is either a finite field or a non-archimedean local field, θ an involutive automorphism of G over k, let K = G θ . Let K 1 = [ K 0 , K 0 ] , the commutator subgroup of K 0 , the connected component of identity of K. In this paper, we provide a simple condition on ( G , θ ) for there to be an irreducible admissible generic representation π of G with Hom K 1 [ π , C ] ≠ 0 . The condition is most transparent to state in terms of a real reductive group G θ ( R ) associated to the pair ( G , θ ) being quasi-split.

Let ζ ( s ) be the Riemann zeta function. In 1911, Bohr showed that the set { ζ ( σ + i τ ) : σ > 1 , τ ∈ R } is dense in ℂ . By Voronin’s denseness theorems in 1972, the sets { ( ζ ( σ + i λ 1 + i τ ) , … , ζ ( σ + i λ n + i τ ) ) : σ ≥ 1 , τ ∈ R } with distinct λ 1 , … , λ n ∈ R and { ( ζ ( σ + i τ ) , ζ ′ ( σ + i τ ) , … , ζ ( n − 1 ) ( σ + i τ ) ) : σ ≥ 1 , τ ∈ R } are dense in ℂ n . By Voronin’s universality theorem, for any fixed 1 ∕ 2 σ 1 and any non-negative integer k , the set { ζ σ , τ ( k ) : τ ∈ R } is dense in C [ a , b ] , where ζ σ , τ ( k ) ( t ) ≔ ζ ( k ) ( σ + i t + i τ ) , t ∈ [ a , b ] . In the present paper, we prove that the set { ζ σ , τ ( k ) : σ ≥ 1 , τ ∈ R } ∩ C [ a , b ] is not dense in C [ a , b ] .

This paper sketches a way of supplementing classical mathematics with a motivation for a Brouwerian theory of free choice sequences. The idea is that time is unending, i.e. that one can never come to an end of it, but also indeterminate, so that in a branching time model only one branch represents the ‘actual’ one. The branching can be random or subject to various restrictions imposed by the creating subject. The fact that the underlying mathematics is classical makes such perhaps delicate issues as the fan theorem no longer problematic. On this model, only intuitionistic logic applies to the Brouwerian free choice sequences, and there it applies not because of any skepticism about classical mathematics, but because there is no ‘end of time’ from the standpoint of which everything about the sequences can be decided.

In this paper, we obtain weighted norm inequalities for the spatial gradients of weak solutions to quasilinear parabolic equations with weights in the Muckenhoupt class A q p ( R n + 1 ) for q ≥ p on non-smooth domains. Here the quasilinear nonlinearity is modeled after the standard p-Laplacian operator. Until now, all the weighted estimates for the gradient were obtained only for exponents q > p . The results for exponents q > p used the full complicated machinery of the Calderon-Zygmund theory developed over the past few decades, but the constants blow up as q → p (essentially because the Maximal function is not bounded on L 1 ). In order to prove the weighted estimates for the gradient at the natural exponent, i.e., q = p , we need to obtain improved a priori estimates below the natural exponent. To this end, we develop the technique of Lipschitz truncation based on [3] , [25] and obtain significantly improved estimates below the natural exponent. Along the way, we also obtain improved, unweighted Calderon-Zygmund type estimates below the natural exponent which is new even for the linear equations.

In this paper we consider iterated integrals on P 1 ∖ { 0 , 1 , ∞ , z } and define a class of Q -linear relations among them, which arises from the differential structure of the iterated integrals with respect to z. We then define a new class of Q -linear relations among the multiple zeta values by taking their limits of z → 1 , which we call confluence relations (i.e., the relations obtained by the confluence of two punctured points). One of the significance of the confluence relations is that it gives a rich family and seems to exhaust all the linear relations among the multiple zeta values. As a good reason for this, we show that confluence relations imply both the regularized double shuffle relations and the duality relations.

Brouwer’s views on the foundations of mathematics have inspired the study of intuitionistic logic, including the study of the intuitionistic propositional calculus and its extensions. The theory of these systems has become an independent branch of logic with connections to lattice theory, topology, modal logic, and other areas. This paper aims to present a modern account of semantics for intuitionistic propositional systems. The guiding idea is that of a hierarchy of semantics, organized by increasing generality: from the least general Kripke semantics on through Beth semantics, topological semantics, Dragalin semantics, and finally to the most general algebraic semantics. While the Kripke, topological, and algebraic semantics have been extensively studied, the Beth and Dragalin semantics have received less attention. We bring Beth and Dragalin semantics to the fore, relating them to the concept of a nucleus from pointfree topology, which provides a unifying perspective on the semantic hierarchy.

In this paper, the notion of measure complexity is introduced for a topological dynamical system and it is shown that Sarnak's Mobius disjointness conjecture holds for any system for which every invariant Borel probability measure has sub-polynomial measure complexity. We then apply this result to a number of situations, including certain systems whose invariant measure don't all have discrete spectrum.

An important feature of the planetary oceanic dynamics is that the aspect ratio (the ratio of the depth to horizontal width) is very small. As a result, the hydrostatic approximation (balance), derived by performing the formal small aspect ratio limit to the Navier–Stokes equations, is considered as a fundamental component in the primitive equations of the large-scale ocean. In this paper, we justify rigorously the small aspect ratio limit of the Navier–Stokes equations to the primitive equations. Specifically, we prove that the Navier–Stokes equations, after being scaled appropriately by the small aspect ratio parameter of the physical domain, converge strongly to the primitive equations, globally and uniformly in time, and the convergence rate is of the same order as the aspect ratio parameter. This result validates the hydrostatic approximation for the large-scale oceanic dynamics. Notably, only the weak convergence of this small aspect ratio limit was rigorously justified before.

The fundamental theorem of surface theory asserts that a surface in the three-dimensional Euclidean space E 3 can be reconstructed from the knowledge of its two fundamental forms under the assumptions that their components are smooth enough—classically in the space C 2 ( ω ) for the first one and in the space C 1 ( ω ) for the second one—and satisfy the Gauss and Codazzi–Mainardi equations over a simply-connected open subset ω of R 2 ; the surface is then uniquely determined up to proper isometries of E 3 . Then S. Mardare showed in 2005 that this result still holds under the much weaker assumptions that the components of the first form are only in the space W loc 1 , p ( ω ) and those of the second form only in the space L loc p ( ω ) , the components of the immersion defining the reconstructed surface being then in the space W loc 2 , p ( ω ) , p > 2 . The purpose of this paper is to complement this last result as follows. First, under the additional assumption that ω is bounded and has a Lipschitz-continuous boundary, we show that a similar existence and uniqueness theorem holds with the spaces W m , p ( ω ) instead of W loc m , p ( ω ) . Second, we establish a nonlinear Korn inequality on a surface asserting that the distance in the W 2 , p ( ω ) -norm, p > 2 , between two given surfaces is bounded, at least locally, by the distance in the W 1 , p ( ω ) -norm between their first fundamental forms and the distance in the L p ( ω ) -norm between their second fundamental forms. Third, we show that the mapping that uniquely defines in this fashion a surface up to proper isometries of E 3 in terms of its two fundamental forms is locally Lipschitz-continuous.