Hardy型算子在径向——角向混合空间上的最佳界（英文）

本文运用旋转方法算出了n维Hardy算子H在径向—角向混合空间上的最佳界.进一步,当0<ββ从L_|x|^p L_θ^p(Rⁿ)到L_|x|qL_θ^q(Rⁿ)上的最佳界.通过对偶建立了共轭算子H^*和H_β^*的相应结果.此外,还考虑了算子H的最佳弱型估计.     

临界或超临界增长分数阶Schrodinger-Poisson方程正解的存在性

本文研究如下分数阶Schrodinger-Poisson方程{(-△)^su+Vx(u)+K(x)φu=f(u)+λ|u|^q-2ux∈R³,(-△)^tφ=K(x)u²,x∈R³其中S∈(3/4,1),t∈(0,1),f是在原点超线性无穷远次临界的连续非线性项,指数q≥2_s^*=6/3-2x.当λ>0充分小时,我们利用变分方法证明上述问题正解的存在性.本文的主要贡献是处理了超临界情形.     

(R,S,μ)对称矩阵逆问题和最佳逼近问题及扰动分析

称R∈C^m×m为k次轮换矩阵若 R的最小多项式为x^k-1(k≥2).令μ∈{0,1,…,k-1}和ζ=e^2πi/k.若R∈C^m×m和S∈C^n×n为k次轮换矩阵,则称A∈C^m×m为(R,S,μ)对称矩阵若RAS^-1=ζ^μA.本文研究了(R,S,μ) 对称矩阵的逆问题和最佳逼近问题,得到了解的表达式. 并讨论了最佳逼近解的扰动分析,得到了比较满意的理论结果, 最后通过数值算例验证了该理论结果的正确性.     

带有临界增长的分数阶Kirchhoff方程的半经典解

本文研究如下带有临界增长的分数阶Kirchhoff方程ε^2s(ε^2s-3∫∫R³×R³|u(x)-u(y)/|²|x-y|^3+2s),x∈R³,其中M是一个连续正的Kirchhoff函数,λ>0是一个参数,3/40充分小和λ足够大时,我们首先证明了上述问题正基态解的存在性.其次,证明了基态解集中在一个由位势函数所刻画的特定集合中.最后,研究了基态解的衰减估计.     

球面上的次临界最佳Sobolev不等式

本文在球面S^N上建立了一类最佳Sobolev不等式:||∫||²LqS^N≤(q-2)Γ(N-d/2+1/dΓ(N+d/2)(∫_S^Nf(§d§-Γ(N+d/2)/Γ(N-d)/2∫_S^(N|∫|²d§),其中Ad(0N的高阶保形算子,d§S^N的归一化曲面测度,2≤q<2N/N-d.     

次临界Choquard方程的多解

该文考虑次临界Choquard方程■(0.1)多解的存在性,其中N> 3,λ是正实参数,p_ε=2_μ^*-ε,ε> 0,0 <μμ^*=(2N-μ)/(N-2)是Hardy-Littlewood-Sobolev不等式意义下的临界指数.假定Ω:=int V^-1(0)是R^N中非空带光滑边界的有界区域,利用Lusternik-Schnirelman定理,该文证明了当λ足够大及ε充分小时,方程(0.1)至少有cat_Ω(Ω)个正解.     

指数除数函数的均值问题

设n是大于1的整数,且n=Π_(i=1)^tp_itp_i^(a_i),令τ_k(a_i),令τ_k^((e))(n)=Π_(p_i((e))(n)=Π_(p_i^(a_i)||n)d_i(a_i).本文研究了和式D(■)=Σ_(n≤x)d(■)的渐近公式,这里d(■)=∑_(n=ab_1(a_i)||n)d_i(a_i).本文研究了和式D(■)=Σ_(n≤x)d(■)的渐近公式,这里d(■)=∑_(n=ab_1²…b_i2…b_i²)1.然后基于以上结论得到了指数除数函数τ_i2)1.然后基于以上结论得到了指数除数函数τ_i^((e))(n)的均值的渐近公式,并改进了前人的结果.     

乘积型Morrey空间中乘积Hardy型算子的最佳界

本文得到了乘积Hardy型算子Hm在乘积Morrey空间L^q,λ(Rⁿ×…×Rⁿ)和齐次中心Morrey空间B^q,λ(Rⁿ×…×Rⁿ)上的算子范数.基于旋转方法,我们推广了傅尊伟等人的结果(见[Houston J.Math.,2012,38(1):225-244]).     

Schrödinger方程的连续时空有限元方法

本文讨论Schr?dinger方程的连续时空有限元方法,通过引入相应的时空投影算子,利用实部虚部分离技巧,得到了变量u在时间节点处的L²范数,以及u和u_t的全局L²(H¹)和L²(L²)范数意义下的最优误差估计结果.该文的结论对进一步探索和设计Schr?dinger方程的数值算法是有益的.     

与对数函数相关的Q型空间的调和延拓问题

本文研究了一类与对数函数相关的n维Q型空间——Q_log,λ^m(Rⁿ).首先给出Q_log,λ^m(Rⁿ)的定义和一些基本性质.进而利用Poisson积分和调和函数空间H_log,λ^m(R₊ⁿ⁺¹),得到了Q_log,λ^m(Rⁿ)的调和延拓,以及H_log,λ^m(R₊ⁿ⁺¹)的边值问题.     

Adams inequalities on measure spaces

In 1988 Adams obtained sharp Moser–Trudinger inequalities on bounded domains of Rn. The main step was a sharp exponential integral inequality for convolutions with the Riesz potential. In this paper we extend and improve Adams' results to functions defined on arbitrary measure spaces with finite measure. The Riesz fractional integral is replaced by general integral operators, whose kernels satisfy suitable and explicit growth conditions, given in terms of their distribution functions; natural conditions for sharpness are also given. Most of the known results about Moser–Trudinger inequalities can be easily adapted to our unified scheme. We give some new applications of our theorems, including: sharp higher order Moser–Trudinger trace inequalities, sharp Adams/Moser–Trudinger inequalities for general elliptic differential operators (scalar and vector-valued), for sums of weighted potentials, and for operators in the CR setting.     

Gradient estimates below the duality exponent

We show sharp local a priori estimates and regularity results for possibly degenerate non-linear elliptic problems, with data not lying in the natural dual space. We provide a precise non-linear potential theoretic analog of classical potential theory results due to Adams (Duke Math J 42:765–778, 1975) and Adams and Lewis (Studia Math 74:169–182, 1982), concerning Morrey spaces imbedding/regularity properties. For this we introduce a technique allowing for a “non-local representation” of solutions via Riesz potentials, in turn yielding optimal local estimates simultaneously in both rearrangement and non-rearrangement invariant function spaces. In fact we also derive sharp estimates in Lorentz spaces, covering borderline cases which remained open for some while.     

Rearrangement Free Method for Hardy-Littlewood-Sobolev Inequalities on $\mathbb{S}^n$

For conformal Hardy-Littlewood-Sobolev(HLS) inequalities [22] and reversed conformal HLS inequalities [8] on $\mathbb{S}^n,$ a new proof is given for the attainability of their sharp constants. Classical methods used in [22] and [8] depends on rearrangement inequalities. Here, we use the subcritical approach to construct the extremal sequence and circumvent the blow-up phenomenon by renormalization method. The merit of the method is that it does not rely on rearrangement inequalities.     

Subcritical polarisations of symplectic manifolds have degree one

We show that if the complement of a Donaldson hypersurface in a closed, integral symplectic manifold has the homology of a subcritical Stein manifold, then the hypersurface is of degree one. In particular, this demonstrates a conjecture by Biran and Cieliebak on subcritical polarisations of symplectic manifolds. Our proof is based on a simple homological argument using ideas of Kulkarni–Wood.

     

Sharp critical thresholds for a class of nonlocal traffic flow models

We study a class of traffic flow models with nonlocal look-ahead interactions. The global regularity of solutions depend on the initial data. We obtain sharp critical threshold conditions that distinguish the initial data into a trichotomy: subcritical initial conditions lead to global smooth solutions, while two types of supercritical initial conditions lead to two kinds of finite time shock formations. The existence of non-trivial subcritical initial data indicates that the nonlocal look-ahead interactions can help avoid shock formations, and hence prevent the creation of traffic jams.     

Energy criterion of global existence for energy-critical Schrödinger equations with subcritical perturbations

We present a variational approach to study the energy-critical Schrödinger equations with subcritical perturbations. Through analysing the Hamiltonian property we establish two types of invariant evolution flows, and derive a new sharp energy criterion for blowup of solutions for the equation. Furthermore, we answer the question: how small are the initial data such that the solutions of this equation are bounded in H ¹(R ^N )?     

Sharp Subcritical and Critical Trudinger-Moser Inequalities on $\mathbb {R}^{2}$ and their Extremal Functions

In this paper, we study on \(\mathbb {R}^{2}\) some new types of the sharp subcritical and critical Trudinger-Moser inequality that have close connections to the study of the optimizers for the classical Trudinger-Moser inequalities. For instance, one of our results can be read as follows: Let 0 ≤ β < 2, p ≥ 0, α ≥ 0. Then

$$\sup_{\left\Vert \nabla u\right\Vert_{2}^{2}+\left\Vert u\right\Vert_{2} ^{2}\leq1}\left\Vert u\right\Vert_{2}^{p}{\int}_{\mathbb{R}^{2}}\exp\left( \alpha\left( 1-\frac{\beta}{2}\right) \left\vert u\right\vert^{2}\right) \left\vert u\right\vert^{2}\frac{dx}{\left\vert x\right\vert^{\beta}}<\infty $$

if and only if α < 4π or α = 4π, p ≥ 2. The attainability and inattainability of these sharp inequalties will be also investigated using a new approach, namely the relations between the supremums of the sharp subcritical and critical ones. This new method will enable us to compute explicitly the supremums of the subcritical Trudinger-Moser inequalities in some special cases. Also, a version of Concentration-compactness principle in the spirit of Lions ( Lions, I. Rev. Mat. Iberoam. 1(1) 145–01 1985) will also be studied.

     

A note on a conjecture for the critical curve of a weakly coupled system of semilinear wave equations with scale-invariant lower order terms

In this note, two blow-up results are proved for a weakly coupled system of semilinear wave equations with distinct scale-invariant lower order terms both in the subcritical case and in the critical case when the damping and the mass terms make both equations in some sense “wave-like.” In the proof of the subcritical case, an iteration argument is used. This approach is based on a coupled system of nonlinear ordinary integral inequalities and lower bound estimates for the spatial integral of the nonlinearities. In the critical case, we employ a test function-type method that has been developed recently by Ikeda-Sobajima-Wakasa and relies strongly on a family of certain self-similar solutions of the adjoint linear equation. Therefore, as critical curve in the p−q plane of the exponents of the power nonlinearities for this weakly coupled system, we conjecture a shift of the critical curve for the corresponding weakly coupled system of semilinear wave equations.     

Adams’ Inequality and Limiting Sobolev Embeddings into Zygmund Spaces

We exhibit sharp embedding constants for Sobolev spaces of any order into Zygmund spaces, obtained as the product of sharp embedding constants for second order Sobolev space into Lorentz spaces. As a consequence, we derive a new proof of Adams?? inequality, which holds in the larger hypotheses of homogenoeous Navier boundary contidions.     

Sharp lower bound of spectral gap for Schrödinger operator and related results

We give an easy proof of Andrews and Clutterbuck’s main results [J. Amer. Math. Soc., 2011, 24(3): 899−916], which gives both a sharp lower bound for the spectral gap of a Schrödinger operator and a sharp modulus of concavity for the logarithm of the corresponding first eigenfunction. We arrive directly at the same estimates by the ‘double coordinate’ approach and asymptotic behavior of parabolic flows. Although using the techniques appeared in the above paper, we partly simplify the method and argument. This maybe help to provide an easy way for estimating spectral gap. Besides, we also get a new lower bound of spectral gap for a class of Schödinger operator.