A Third Derivative Estimate for Monge-Ampere Equations with Conic Singularities(Dedicated to Haim Brezis on the occasion of his 70th birthday)

The author applies the arguments in his PKU Master degree thesis in 1988 to derive a third derivative estimate, and consequently, a C~(2,α)-estimate, for complex MongeAmpere equations in the conic case. This C~(2,α)-estimate was used by Jeffres-MazzeoRubinstein in their proof of the existence of K¨ahler-Einstein metrics with conic singularities.     

Harmonic Maps in Connection of Phase Transitions with Higher Dimensional Potential Wells

This is in the sequel of authors' paper [Lin, F. H., Pan, X. B. and Wang, C. Y.,Phase transition for potentials of high dimensional wells, Comm. Pure Appl. Math., 65(6),2012, 833–888] in which the authors had set up a program to verify rigorously some formal statements associated with the multiple component phase transitions with higher dimensional wells. The main goal here is to establish a regularity theory for minimizing maps with a rather non-standard boundary condition at the sharp interface of the transition.The authors also present a proof, under simplified geometric assumptions, of existence of local smooth gradient flows under such constraints on interfaces which are in the motion by the mean-curvature. In a forthcoming paper, a general theory for such gradient flows and its relation to Keller-Rubinstein-Sternberg's work(in 1989) on the fast reaction, slow diffusion and motion by the mean curvature would be addressed.     

Reflections on the security proofs of Boneh-Franklin identity-based encryption scheme

In this paper, we first review the existing proofs of the Boneh-Franklin identity-based encryption scheme (BF-IBE for short), and show how to admit a new proof by slightly modifying the specifications of the hash functions of the original BF-IBE. Compared with prior proofs, our new proof provides a tighter security reduction and minimizes the use of random oracles, thus indicates BF-IBE has better provable security with our new choices of hash functions. The techniques developed in our proof can also be applied to improving security analysis of some other IBE schemes. As an independent technical contribution, we also give a rigorous proof of the Fujisaki-Okamoto (FO) transformation in the case of CPA-to-CCA, which demonstrates the efficiency of the FO-transformation (CPA-to-CCA), in terms of the tightness of security reduction, has long been underestimated. This result can remarkably benefit the security proofs of encryption schemes using the FO-transformation for CPA-to-CCA enhancement.     

Limiting behavior of a class of Hermitian Yang-Mills metrics,I

This paper begins to study the limiting behavior of a family of Hermitian Yang-Mills(HYM for brevity) metrics on a class of rank two slope stable vector bundles over a product of two elliptic curves with K?hler metrics ωε when ε → 0. Here, ωε are flat and have areas ε and ε-1 on the two elliptic curves, respectively.A family of Hermitian metrics on the vector bundle are explicitly constructed and with respect to them, the HYM metrics are normalized. We then compare the family of normalized HYM metrics with the family of constructed Hermitian metrics by doing estimates. We get the higher order estimates as long as the C~0-estimate is provided. We also get the estimate of the lower bound of the C~0-norm. If the desired estimate of the upper bound of the C~0-norm can be obtained, then it would be shown that these two families of metrics are close to arbitrary order in ε in any Cknorms.     

Rough singular integral operators on Hardy-Sobolev spaces

The authors study the singular integral operator TΩ,αf(x)=p.v.∫R^nb(|y|Ω(y′)|y|^-n-αf(x-y)dy, defined on all test functions f, where b is a bounded function, α＞0, Ω(y′) is an integrable function on the unit sphere S^n-1 satisfying certain cancellation conditions. It is proved that, for n/(n α)＜p＜∞,TΩ,α is a bounded operator from the Hardy-Sobolev space H^pα to the Hardy space H^p. The results and its applications improve some theorems in a previous paper of the author and they are extensions of the main theorems in Wheeden‘s paper(1969). The proof is based on a new atomic decomposition of the space H^pα by Han, Paluszynski and Weiss(1995). By using the same proof,the singluar integral operators with variable kernels are also studied.     

Differential-operator representations of Weyl group and singular vectors in Verma modules

Given a suitable ordering of the positive root system associated with a semisimple Lie algebra,there exists a natural correspondence between Verma modules and related polynomial algebras. With this, the Lie algebra action on a Verma module can be interpreted as a differential operator action on polynomials, and thus on the corresponding truncated formal power series. We prove that the space of truncated formal power series gives a differential-operator representation of the Weyl group W. We also introduce a system of partial differential equations to investigate singular vectors in the Verma module. It is shown that the solution space of the system in the space of truncated formal power series is the span of {w(1) | w ∈ W }. Those w(1) that are polynomials correspond to singular vectors in the Verma module. This elementary approach by partial differential equations also gives a new proof of the well-known BGG-Verma theorem.     

Constructing super Gabor frames: the rational time-frequency lattice case

For a time-frequency lattice Λ = A Z d B Z d , it is known that an orthonormal super Gabor frame of length L exists with respect to this lattice if and only if |det( AB) | = 1 L . The proof of this result involves various techniques from multi-lattice tiling and operator algebra theory, and it is far from constructive. In this paper we present a very general scheme for constructing super Gabor frames for the rational lattice case. Our method is based on partitioning an arbitrary fundamental domain of the lattice in the frequency domain such that each subset in the partition tiles R d by the lattice in the time domain. This approach not only provides us a simple algorithm of constructing various kinds of orthonormal super Gabor frames with flexible length and multiplicity, but also allows us to construct super Gabor (non-Riesz) frames with high order smoothness and regularity. Several examples are also presented.     

GLOBAL REGULARITY FOR MODIFIED CRITICAL DISSIPATIVE QUASI-GEOSTROPHIC EQUATIONS

We consider the n-dimensional modified quasi-geostrophic(SQG) equations δ_tθ + u·▽θ+kΛαθ=0, u = Λα-1R⊥θ with κ 0, α∈(0, 1] and θ0∈ W1,∞(Rn). In this paper, we establish a different proof for the global regularity of this system. The original proof was given by Constantin, Iyer, and Wu[5], who employed the approach of Besov space techniques to study the global existence and regularity of strong solutions to modified critical SQG equations for two dimensional case.The proof provided in this paper is based on the nonlinear maximum principle as well as the approach in Constantin and Vicol [2].     

INTERFACE BEHAVIOR OF COMPRESSIBLE NAVIER-STOKES EQUATIONS WITH DISCONTINUOUS BOUNDARY CONDITIONS AND VACUM

In this paper,we study a one-dimensional motion of viscous gas near vacuum. We are interested in the case that the gas is in contact with the vacuum at a finite interval. This is a free boundary problem for the one-dimensional isentropic Navier-Stokes equations, and the free boundaries are the interfaces separating the gas from vacuum,across which the density changes discontinuosly.Smoothness of the solutions and the uniqueness of the weak solutions are also discussed.The present paper extends results in Luo-Xin-Yang[12] to the jump boundary conditions case.     

ON THE ERROR ESTIMATE OF LINEAR FINITE ELEMENT APPROXIMATION TO THE ELASTIC CONTACT PROBLEM WITH CURVED CONTACT BOUNDARY

1. PreliminaryThe error estimate of linear finite element approximation to the elastic contact problem with curved contact boundary was considered in [2], in which the authors obtainedthe error bound of O(hl) with a much complex proof, requirement of three times continuously differentiable for contact boundary and extra regularities of triangulation (c.f. [2, Theorem 3.3, p.149]). In this paper, we obtained the error bound of O(hi) withonly requirement of two times continuously differentiable…     

Gradient Estimates for a Nonlinear Parabolic Equation with Diffusion on Complete Noncompact Manifolds

The authors obtain some gradient estimates for positive solutions to the following nonlinear parabolic equation:αu/αt=△u-b(x,t)u~σ on complete noncompact manifolds with Ricci curvature bounded from below,where 0σ1 is a real constant,and b(x,t) is a function which is C~2 in the x-variable and C~1 in the t-variable.     

On Some Families of Smooth Affine Spherical Varieties of Full Rank

Let G be a complex connected reductive group. Losev has shown that a smooth affine spherical G-variety X is uniquely determined by its weight monoid, which is the set of irreducible representations of G that occur in the coordinate ring of X. In this paper we use a combinatorial characterization of the weight monoids of smooth affine spherical varieties to classify:(a) all such varieties for G = SL(2) × C~×and(b) all such varieties for G simple which have a G-saturated weight monoid of full rank. We also use the characterization and Knop's classification theorem for multiplicity free Hamiltonian manifolds to give a new proof of Woodward's result that every reflective Delzant polytope is the moment polytope of such a manifold.     

A Third Derivative Estimate for Monge-Ampere Equations with Conic Singularities

The author applies the arguments in his PKU Master degree thesis in 1988 to derive a third derivative estimate,and consequently,a C2,α-estimate,for complex MongeAmpere equations in the conic case.This C2,α-estimate was used by Jeffres-MazzeoRubinstein in their proof of the existence of K（a）hler-Einstein metrics with conic singularities.     

The complex 2-sphere in C~3 and Schr?dinger flows Dedicated to Professor Hesheng Hu on the Occasion of Her 90th Birthday

By using holomorphic Riemannian geometry in C~3, the coupled Landau-Lifshitz(CLL) equation is proved to be exactly the equation of Schr¨odinger flows from R~1 to the complex 2-sphere CS~2(1) → C~3.Furthermore, regarded as a model of moving complex curves in C~3, the CLL equation is shown to preserve the PT symmetry if the initial data is of the P symmetry. As a consequence, the nonlocal nonlinear Schr¨odinger(NNLS)equation proposed recently by Ablowitz and Musslimani is proved to be gauge equivalent to the CLL equation with initial data being restricted by the P symmetry. This gives an accurate characterization of the gaugeequivalent magnetic structure of the NNLS equation described roughly by Gadzhimuradov and Agalarov(2016).     

Smoothness of invariant manifolds and foliations for infinite dimensional random dynamical systems Dedicated to Professor Shantao Liao

In this paper, we investigate the smoothness of invariant manifolds and foliations for random dynamical systems with nonuniform pseudo-hyperbolicity in Hilbert spaces. We discuss on the effect of temperedness and the spectral gaps in the nonuniform pseudo-hyperbolicity so as to prove the existence of invariant manifolds and invariant foliations, which preserve the C~(N,τ(ω))Holder smoothness of the random system in the space variable and the measurability of the random system in the sample point. Moreover, we also prove that the stable foliation is C~(N-1,τ(ω))in the base point.     

On a Lemma of Erdos et al and Its Applications

In 1943, Erdos stated a famous result concerning interpolatory polynomials,but no proof given. Since this theorem is a fundamental and frequently quoted resultof the theory of interpolation, Erdos et al. published a proof in[2] (1989) recently.Three deep lemmas have been established in [2] in order to give this proof. However,we found that the proof of lemma 2 of [2] is not correct. The main purpose of this     

SMALLEST g-SUPERSOLUTION WITH CONSTRAINT

In this paper the existence and uniqueness of the smallest g-supersolution for BSDE is discussed in the case without Lipschitz condition imposing on both constraint function and drift coefficient in the different method from the one with Lipschitz condition. Then by considering (ξ,g) as a parameter of BSDE,and (ξ^α,g^α) as a class of parameters for BSDE,where α belongs to a set φ,for every α∈φ there exists a pair of solution {Y^α,Z^α} for the BSDE,the properties of supα∈φ {Y^α} which is also a solution for some BSDE is studied. This result may be used to discuss optimal problems with recursive utility.     

Nodal Sets and Doubling Conditions in Elliptic Homogenization

This paper is concerned with uniform measure estimates for nodal sets of solutions in elliptic homogenization. We consider a family of second-order elliptic operators {L_ε} in divergence form with rapidly oscillating and periodic coefficients. We show that the(d-1)-dimensional Hausdorff measures of the nodal sets of solutions to L_ε(u_ε) = 0 in a ball in Rdare bounded uniformly in ε 0. The proof relies on a uniform doubling condition and approximation of u_ε by solutions of the homogenized equation.     

光滑函数类中一族无高阶导数的大范围收敛迭代法

The problem whether the iteration formula with the global convergence which does notneed to compute the second order derivative of the function can be found, raised in [7], issolved for f(x)∈C~1(R~1) in the present paper by using the methods of prior estimates andintroducing a parametric function. The main results are as follows: 1. For f(x)∈C~1(R~1), the families of iteration formulas of the global convergence,without derivatives of higher order, are suggested in the following formx_(n 1)=x_n±|f(x_n)|/|f'(x_n)| α(x_n)|f(x_n)|,(1)x_(n 1)=x_n-α|f(x_n)|/(α-1)f'(x_n)sgnf(x_0)±(f'2(x_n)αp(x_n)|f(x_n)|),(2)x_(n 1)=x_n±|f(x_n)f'(x_n)|/f'2(x_n) 1/2p(x_n)|f(x_n)|,(3)Where the real parameter a∈(0, 2] and the real parametric functions α(x)=α(f(x),f'(x)) (>0) and p(x)= p(f(x), f,(x)) (>0) with certain arbitrariness are continuous orpiecewise continuous. 2. The convergence order of the iteration sequence {x_n} generated by (1), (2) or (3)is 2 for a simple real zero of f(x), and is 1 for a multiple zero.