In this paper, we prove that for every index perfect non-degenerate compact star-shaped hypersurface ∑ ⊂ R²ⁿ, there exist at least n non-hyperbolic closed characteristics with even Maslovtype indices on ∑ when n is even. When n is odd, there exist at least n closed characteristics with odd Maslov-type indices on ∑ and at least (n-1) of them are non-hyperbolic. Here we call a compact star-shaped hypersurface ∑ ⊂ R²ⁿ index perfect if it carries only finitely many geometrically distinct prime closed characteristics, and every prime closed characteristic (τ, y) on ∑ possesses positive mean index and whose Maslov-type index i(y, m) of its m-th iterate satisfies i(y, m) ≠-1 when n is even, and i(y, m) ∉ {-2, -1, 0} when n is odd for all m ∈ N.

The field K=Q(√-7) is the only imaginary quadratic field with class number 1, in which the prime 2 splits, and we fix one of the primes p of K lying above 2. The modular elliptic curve X₀(49) has complex multiplication by the maximal order O of K, and we let E be the twist of X₀(49) by the quadratic extension K(√M)/K, where M is any square free element of O with M ≡ 1 mod 4 and (M, 7)=1. In the present note, we use surprisingly simple algebraic arguments to prove a sharp estimate for the rank of the Mordell-Weil group modulo torsion of E over the field F_∞=K(E_p∞), where E_p∞ denotes the group of p^∞-division points on E. Moreover, writing B for the twist of X₀(49) by K(⁴√-7)/K, our Iwasawa-theoretic arguments also show that the weak form of the conjecture of Birch and Swinnerton-Dyer implies the non-vanishing at s=1 of the complex L-series of B over every finite layer of the unique Z₂-extension of K unramified outside p. We hope to give a proof of this last non-vanishing assertion in a subsequent paper.

We introduce a class of tri-linear operators that combine features of the bilinear Hilbert transform and paraproduct. For two instances of these operators, we prove boundedness property in a large range D={(p₁, p₂, p₃) ∈ R³:1 < p₁, p₂ < ∞, 1/p₁ + 1/p₂ < 3/2, 1 < p₃ < ∞}

Let Q(x) be a nonnegative definite, symmetric matrix such that √Q(x) is Lipschitz continuous. Given a real-valued function b(x) and a weak solution u(x) of div(Q▽u)=b, we find sufficient conditions in order that √Q▽u has some first order smoothness. Specifically, if Ω is a bounded open set in Rⁿ, we study when the components of √Q▽u belong to the first order Sobolev space W_Q^1,2(Ω) defined by Sawyer and Wheeden. Alternately, we study when each of n first order Lipschitz vector field derivatives X_iu has some first order smoothness if u is a weak solution in Ω of ∑_i=1ⁿ X_i'X_iu + b=0. We do not assume that {X_i} is a Hörmander collection of vector fields in Ω. The results signal ones for more general equations.

In this paper, we derive the global existence of smooth solutions of the 3D incompressible Euler equations with damping for a class of large initial data, whose Sobolev norms H^s can be arbitrarily large for any s ≥ 0. The approach is through studying the quantity representing the difference between the vorticity and velocity. And also, we construct a family of large solutions for MHD equations with damping.

The family of pairwise independently determined (PID) systems, i.e., those for which the independent joining is the only self joining with independent 2-marginals, is a class of systems for which the long standing open question by Rokhlin, of whether mixing implies mixing of all orders, has a positive answer. We show that in the class of weakly mixing PID one finds a positive answer for another long-standing open problem, whether the multiple ergodic averages

almost surely converge.

We give a brief survey of some developments in Nielsen fixed point theory. After a look at early history and a digress to various generalizations, we confine ourselves to several topics on fixed points of self-maps on manifolds and polyhedra. Special attention is paid to connections with geometric group theory and dynamics, as well as some formal approaches.

Given a family of Calabi-Yau varieties over the punctured disc or over the field of Laurent series, we show that, after a finite base change, the family can be extended across the origin while keeping the canonical class trivial. More generally, we prove similar extension results for families whose log-canonical class is semi-ample. We use these to show that the Berkovich and essential skeleta agree for smooth varieties over C((t)) with semi-ample canonical class.

We consider a class of generalized Fibonacci unimodal maps for which the central return times {s_n} satisfy that s_n=s_n-1 + κs_n-2 for some κ ≥ 1. We show that such a unimodal map admits a unique absolutely continuous invariant probability with exactly stretched exponential decay of correlations if its critical order lies in (1, κ + 1).

In this paper, we study solution structures of the following generalized Lennard-Jones system in Rⁿ,

with 0 < α < β. Considering periodic solutions with zero angular momentum, we prove that the corresponding problem degenerates to 1-dimensional and possesses infinitely many periodic solutions which must be oscillating line solutions or constant solutions. Considering solutions with non-zero angular momentum, we compute Morse indices of the circular solutions first, and then apply the mountain pass theorem to show the existence of non-circular solutions with non-zero topological degrees. We further prove that besides circular solutions the system possesses in fact countably many periodic solutions with arbitrarily large topological degree, infinitely many quasi-periodic solutions, and infinitely many asymptotic solutions.

The isovariant Borsuk-Ulam constant c_G of a compact Lie group G is defined to be the supremum of c ∈ R such that the inequality
c(dim V-dim V^G) ≤ dim W-dim W^G
holds whenever there exists a G-isovariant map f:S(V)→S(W) between G-representation spheres. In this paper, we shall discuss some properties of c_G and provide lower estimates of c_G of connected compact Lie groups, which leads us to some Borsuk-Ulam type results for isovariant maps. We also introduce and discuss the generalized isovariant Borsuk-Ulam constant č_G for more general smooth G-actions on spheres. The result is considerably different from the case of linear actions.

In this paper, the complete convergence and complete moment convergence for maximal weighted sums of extended negatively dependent random variables are investigated. Some sufficient conditions for the convergence are provided. In addition, the Marcinkiewicz-Zygmund type strong law of large numbers for weighted sums of extended negatively dependent random variables is obtained. The results obtained in the article extend the corresponding ones for independent random variables and some dependent random variables.

We study the number of solutions N(B, F) of the diophantine equation n₁n₂=n₃n₄, where 1 ≤ n₁ ≤ B, 1 ≤ n₃ ≤ B, n₂, n₄ ∈ F and F⊂[1, B] is a factor closed set. We study more particularly the case when F={m=p₁^ε1…p_k^εk, ε_j ∈ {0, 1}, 1 ≤ j ≤ k}, p₁,…, p_k being distinct prime numbers.

In this paper, complete moment convergence for widely orthant dependent random variables is investigated under some mild conditions. For arrays of rowwise widely orthant dependent random variables, the main results extend recent results on complete convergence to complete moment convergence. These results on complete moment convergence are shown to yield new results on complete integral convergence.

In this paper we present a necessary and sufficient condition to guarantee that the extended function of the solution by zero extension for the biharmonic equation in a smaller domain is still the solution of the corresponding extension problem in a larger domain. We prove the results under the frameworks of classical solutions and strong solutions.

We study Jackson's inequality between the best approximation of a function f ∈ L₂(R³) by entire functions of exponential spherical type and its generalized modulus of continuity. We prove Jackson's inequality with the exact constant and the optimal argument in the modulus of continuity. In particular, Jackson's inequality with the optimal parameters is obtained for classical modulus of continuity of order r and Thue-Morse modulus of continuity of order r ∈ N. These results are based on the solution of the generalized Logan problem for entire functions of exponential type. For it we construct a new quadrature formulas for entire functions of exponential type.

By using the idea of Wakimoto's free field, we construct a class of representations for the Lie superalgebra D(2, 1; α) on the tensor product of a polynomial algebra and an exterior algebra involving one parameter λ. Then we obtain the necessary and sufficient condition for the representations to be irreducible. In fact, the representation is irreducible if and only if the parameter λ satisfies (λ + m)(λ-(1+α/α)≠m)=0 for any m ∈ Z₊.

Estimation of the extreme conditional quantiles with functional covariate is an important problem in quantile regression. The existing methods, however, are only applicable for heavy-tailed distributions with a positive conditional tail index. In this paper, we propose a new framework for estimating the extreme conditional quantiles with functional covariate that combines the nonparametric modeling techniques and extreme value theory systematically. Our proposed method is widely applicable, no matter whether the conditional distribution of a response variable Y given a vector of functional covariates X is short, light or heavy-tailed. It thus enriches the existing literature.

Let p be an odd prime and q=2(p-1). Up to total degree t-s < max{(5p³ + 6p² + 6p + 4)q-10, p⁴q}, the generators of H^s,t(U(L)), the cohomology of the universal enveloping algebra of a bigraded Lie algebra L, are determined and their convergence is also verified. Furthermore our results reveal that this cohomology satisfies an analogous Poinćare duality property. This largely generalizes an earlier classical results due to J. P. May.

Generalized random graphs are considered where the presence or absence of an edge depends on the weights of its nodes. Our main interest is to investigate large deviations for the number of edges per node in such a generalized random graph, where the node weights are deterministic under some regularity conditions, as well as chosen i.i.d. from a finite set with positive components. When the node weights are random variables, obstacles arise because the independence among edges no longer exists, our main tools are some results of large deviations for mixtures. After calculating, our results show that the corresponding rate functions for the deterministic case and the random case are very different.

In this paper, we apply Littlewood-Paley theory and Itô integral to get the global existence of stochastic Navier-Stokes equations with Coriolis force in Fourier-Besov spaces. As a comparison, we also give corresponding results of the deterministic Navier-Stokes equations with Coriolis force.

Let G be the group of the fractional linear transformations generated by
T(τ)=τ + λ, S(τ)=(τ cos π/n + sin π/n)/(-τ sin π/n + cos π/n);
where
λ=2(cos π/m + cos π/n)/sin π/n;
m, n is a pair of integers with either n ≥ 2, m ≥ 3 or n ≥ 3, m ≥ 2; τ lies in the upper half plane H.
A fundamental set of functions f₀, f_i and f_∞ automorphic with respect to G will be constructed from the conformal mapping of the fundamental domain of G. We derive an analogue of Ramanujan's triple differential equations associated with the group G and establish the connection of f₀, f_i and f_∞ with a family of hypergeometric functions.

In this article, we solve some word equations originated from discrete dynamical systems related to antisymmetric cubic map. These equations emerge when we work with primitive and greatest words. In particular, we characterize all the cases for which <β₁β₁>=<β₂β₂> where β₁ and β₂ are the greatest words in <<β₁>> and <<β₂>> of M(n).

Let k be an algebraically closed field of characteristic p > 0, X a smooth projective variety over k with a fixed ample divisor H, F_X:X → X the absolute Frobenius morphism on X. Let E be a rational GL_n(k)-bundle on X, and ρ:GL_n(k) → GL_m(k) a rational GL_n(k)-representation of degree at most d such that ρ maps the radical R(GL_n(k)) of GL_n(k) into the radical R(GL_m(k)) of GL_m(k). We show that if F_X^N*(E) is semistable for some integer N ≥ max_{0 < r < m} (_r^m) · log_p(dr), then the induced rational GL_m(k)-bundle E(GL_m(k)) is semistable. As an application, if dim X=n, we get a sufficient condition for the semistability of Frobenius direct image F_X*(ρ_*(Ω_X¹)), where ρ_*(Ω_X¹) is the vector bundle obtained from Ω_X¹ via the rational representation ρ.

We introduce a new function space that is much finer than the classical Lebesgue spaces, and investigate the continuity and the discontinuity of the Calderón-Zygmund operators on the new weighted spaces. In order to identify the continuity of singular integrals, we prove an interpolation theorem on the new spaces and propose a concept of the spectrum of base functions.

In this article, we establish the existence of an LHMTS(m^v) for v ≡ 2 (mod 6) and m≡ 3 (mod 6). Thus there exists an LHMTS(m^v) if and only if v(v-1)m² ≡ 0 (mod 3) except possibly for v=6, m≡ 1, 5 (mod 6) and m≠1. In the similar way, the existence of LHDTS(m^v) is completely determined, i.e., there exists an LHDTS(m^v) if and only if v(v-1)m² ≡ 0 (mod 3).

In the paper, Ding projective modules and Ding projective complexes are considered. In particular, it is proven that Ding projective complexes are precisely the complexes X for which each X_m is a Ding projective R-module for all m ∈ Z.

The Cauchy problem for the 3D incompressible magneto-hydrodynamics equations in critcal spaces is considered. We first prove the global well-posedness of mild solution for the system in some time dependent spaces. Furthermore, we obtain analyticity of the solution.

Let Pⁿ be a simple n-polytope with a Z²-characteristic function λ. And h is a Morse function over Pⁿ. Then the small cover Mⁿ(λ) corresponding to the pair (Pⁿ, λ) has a cell structure given by h. From this cell structure we can derive a cellular chain complex of Mⁿ(λ) with integer coefficients. In this paper, firstly, we discuss the highest dimensional boundary morphism ∂_n of this cellular chain complex and get that ∂_n=0 or 2 by a natural way. And then, from the well-known result that the submanifold corresponding to (F, λ_F) is naturally a small cover with dimension k, where F is any k-face of Pⁿ and λ_F is the restriction of λ on F, we get that ∂_k=0 or ±2 for 0 ≤ k < n. Finally, by using the definition of inherited characteristic function which is the restriction of λ on the faces of Pⁿ, we get a way to calculate the homology groups of Mⁿ(λ). Applying our result to a 3-small cover we have that the homology groups of any 3-small cover is torsion-free or has only 2-torsion.

Gosper introduced the functions sin_q z and cos_q z as q-analogues for the trigonometric functions sin z and cos z respectively. He stated a variety of identities involving these two q-trigonometric functions along with certain constants denoted by Π_qⁿ (n ∈ N). Gosper noticed that all his formulas on these constants have more than two of the Π_qⁿ. So, it is natural to raise the question of establishing identities involving only two of the Π_qⁿ. In this paper, our main goal is to give examples of such formulas in only two Π_qⁿ.

In this paper, we construct a special class of subshifts of finite type. By studying the spectral radius of the transfer matrix associated with the subshift of finite type, we obtain an estimation of its topological entropy. Interestingly, we find that the topological entropy of this class of subshifts of finite type converges monotonically to log(n + 1) (a constant only depends on the structure of the transfer matrices) as the increasing of the order of the transfer matrices.

The Sobolev space H^s(R^d) with s > d/2 contains many important functions such as the bandlimited or rational ones. In this paper we propose a sequence of measurement functions {ϕ_j,k^γ} ⊆ H^-s(R^d) to the phase retrieval problem for the real-valued functions in H^s(R^d). We prove that any real-valued function f ∈ H^s(R^d) can be determined, up to a global sign, by the phaseless measurements {|<f, ϕ_j,k^γ>|}. It is known that phase retrieval is unstable in infinite dimensional spaces with respect to perturbations of the measurement functions. We examine a special type of perturbations that ensures the stability for the phase-retrieval problem for all the real-valued functions in H^s(R^d) ∩ C¹(R^d), and prove that our iterated reconstruction procedure guarantees uniform convergence for any function f ∈ H^s(R^d) ∩ C¹(R^d) whose Fourier transform f is L¹-integrable. Moreover, numerical simulations are conducted to test the efficiency of the reconstruction algorithm.

Let S₁ and S₂ be two (k-1)-subsets in a k-uniform hypergraph H. We call S₁ and S₂ strongly or middle or weakly independent if H does not contain an edge e ∈ E(H) such that S₁ ∩ e ≠∅ and S₂ ∩ e ≠∅ or e ⊆ S₁ ∪ S₂ or e ⊇ S₁ ∪ S₂, respectively. In this paper, we obtain the following results concerning these three independence. (1) For any n ≥ 2k²-k and k ≥ 3, there exists an n-vertex k-uniform hypergraph, which has degree sum of any two strongly independent (k-1)-sets equal to 2n-4(k-1), contains no perfect matching; (2) Let d ≥ 1 be an integer and H be a k-uniform hypergraph of order n ≥ kd+(k-2)k. If the degree sum of any two middle independent (k-1)-subsets is larger than 2(d-1), then H contains a d-matching; (3) For all k ≥ 3 and sufficiently large n divisible by k, we completely determine the minimum degree sum of two weakly independent (k-1)-subsets that ensures a perfect matching in a k-uniform hypergraph H of order n.

A trust-region sequential quadratic programming (SQP) method is developed and analyzed for the solution of smooth equality constrained optimization problems. The trust-region SQP algorithm is based on filter line search technique and a composite-step approach, which decomposes the overall step as sum of a vertical step and a horizontal step. The algorithm includes critical modifications of horizontal step computation. One orthogonal projective matrix of the Jacobian of constraint functions is employed in trust-region subproblems. The orthogonal projection gives the null space of the transposition of the Jacobian of the constraint function. Theoretical analysis shows that the new algorithm retains the global convergence to the first-order critical points under rather general conditions. The preliminary numerical results are reported.

In this paper, we obtain the quantitative bound of the exponential convergence rates of Markov chains under a weaken minorization condition, using the coupling method and the analytic approach. And also, we obtain the convergence rates for continuous time Markov processes.

We consider the evolution of viscous fluids in a 2D horizontally periodic slab bounded above by a free top surface and below by a fixed flat bottom. This is a free boundary problem. The dynamics of the fluid are governed by the incompressible stationary Navier-Stokes equations under the influence of gravity and the effect of surface tension. We develop the global theory of solutions in low regularity Sobolev spaces for small data by nonlinear energy estimates.

In this paper, we propose and analyze two kinds of novel and symmetric energy-preserving formulae for the nonlinear oscillatory Hamiltonian system of second-order differential equations Aq"(t)+ Bq(t)=f(q(t)), where A ∈ R^m×m is a symmetric positive definite matrix, B ∈ R^m×m is a symmetric positive semi-definite matrix that implicitly contains the main frequencies of the problem and f(q)=-▽_qV(q) for a real-valued function V(q). The energy-preserving formulae can exactly preserve the Hamiltonian H(q', q)=(1)/2q'^τ Aq' + (1)/2q^τ Bq + V(q). We analyze the properties of energy-preserving and convergence of the derived energy-preserving formula and obtain new efficient energy-preserving integrators for practical computation. Numerical experiments are carried out to show the efficiency of the new methods by the nonlinear Hamiltonian systems.

Let T:X → X be a continuous map of a compact metric space X. A point x ∈ X is called Banach recurrent point if for all neighborhood V of x, {n ∈ N:Tⁿ(x) ∈ V } has positive upper Banach density. Denote by Tr(T), W(T), QW(T) and BR(T) the sets of transitive points, weakly almost periodic points, quasi-weakly almost periodic points and Banach recurrent points of (X, T). If (X, T) has the specification property, then we show that every transitive point is Banach recurrent and ∅≠W(T) ∩ Tr(T) _≠^⊂W^*(T) ∩ Tr(T) _≠^⊂ QW(T) ∩ Tr(T) _≠^⊂ BR(T) ∩ Tr(T), in which W^*(T) is a recurrent points set related to an open question posed by Zhou and Feng. Specifically the set Tr(T) ∩ W^*(T)\W(T) is residual in X. Moreover, we construct a point x ∈ BR\QW in symbol dynamical system, and demonstrate that the sets W(T), QW(T) and BR(T) of a dynamical system are all Borel sets.

The minimax concave penalty (MCP) has been demonstrated theoretically and practically to be effective in nonconvex penalization for variable selection and parameter estimation. In this paper, we develop an efficient alternating direction method of multipliers (ADMM) with continuation algorithm for solving the MCP-penalized least squares problem in high dimensions. Under some mild conditions, we study the convergence properties and the Karush-Kuhn-Tucker (KKT) optimality conditions of the proposed method. A high-dimensional BIC is developed to select the optimal tuning parameters. Simulations and a real data example are presented to illustrate the efficiency and accuracy of the proposed method.

The original version of the article was published in[1]. Unfortunately, the original version of this article contains a mistake:in Theorem 6.2 appears that β(n, Δ)=(n-Δ+5)/4 but the correct statement is β(n, Δ)=(n-Δ+4)/4. In this erratum we correct the theorem and give the correct proof.