Bilinear restriction estimates for surfaces with curvatures of different signs

Recently, the sharp -bilinear (adjoint) restriction estimates for the cone and the paraboloid were established by Wolff and Tao, respectively. Their results rely on the fact that for the cone and the paraboloid, the nonzero principal curvatures have the same sign. We generalize those bilinear restriction estimates to surfaces with curvatures of different signs.

     

Restriction estimates for space curves with respect to general measures

In this paper we consider adjoint restriction estimates for space curves with respect to general measures and obtain optimal estimates when the curves satisfy a finite type condition. The argument here is new in that it doesn?t rely on the offspring curve method, which has been extensively used in the previous works. Our work was inspired by the recent argument due to Bourgain and Guth which was used to deduce linear restriction estimates from multilinear estimates for hypersurfaces.     

Bounds on Oscillatory Integral Operators Based on Multilinear Estimates

We apply the Bennett–Carbery–Tao multilinear restriction estimate in order to bound restriction operators and more general oscillatory integral operators. We get improved L ^p estimates in the Stein restriction problem for dimension at least 5 and a small improvement in dimension 3. We prove similar estimates for H?rmander-type oscillatory integral operators when the quadratic term in the phase function is positive definite, getting improvements in dimension at least 5. We also prove estimates for H?rmander-type oscillatory integral operators in even dimensions. These last oscillatory estimates are related to improved bounds on the dimensions of curved Kakeya sets in even dimensions.     

Linear and bilinear estimates for oscillatory integral operators related to restriction to hypersurfaces

We obtain bilinear estimates for oscillatory integral operators which are variable coefficient generalizations of bilinear restriction estimates for hypersurfaces. As applications, we improve the known estimates for oscillatory integrals.     

New restriction estimates for the 3-d paraboloid over finite fields

We improve the range of exponents for the restriction problem for the 3-d paraboloid over finite fields. The key new ingredient is a variant of the Bourgain–Katz–Tao finite field incidence theorem derived from sum-product estimates. In prime order fields, we give an explicit relationship between the exponent in this incidence theorem and restriction estimates for the paraboloid.     

Weighted restriction type estimates for Grushin operators and application to spectral multipliers and Bochner–Riesz summability

We prove weighted restriction type estimates for Grushin operators. These estimates are then used to prove sharp spectral multiplier theorems as well as Bochner–Riesz summability results with sharp exponent.     

Convolution and Restriction Estimates for a 3-Surface in R<Superscript>5</Superscript>

We establish convolution and Fourier restriction estimates for a measure on a 3- surface in R⁵.     

Norm convergence of multiple ergodic averages on amenable groups

We consider abstract non-negative self-adjoint operators on L²(X) which satisfy the finite-speed propagation property for the corresponding wave equation. For such operators, we introduce a restriction type condition, which in the case of the standard Laplace operator is equivalent to (p, 2) restriction estimate of Stein and Tomas. Next, we show that in the considered abstract setting, our restriction type condition implies sharp spectral multipliers and endpoint estimates for the Bochner-Riesz summability. We also observe that this restriction estimate holds for operators satisfying dispersive or Strichartz estimates. We obtain new spectral multiplier results for several second order differential operators and recover some known results. Our examples include Schrödinger operators with inverse square potentials on Rⁿ, the harmonic oscillator, elliptic operators on compact manifolds, and Schr¨odinger operators on asymptotically conic manifolds.     

Curvature estimates for CMC surfaces in three dimensional manifolds

In this paper, we give curvature estimates for strongly stable CMC surfaces in complete three dimensional manifolds.     

Rotational symmetry and properties of the ancient solutions of Ricci flow on surfaces

We give a simple proof for the rotational symmetry of ancient solutions of Ricci flow on surfaces. As a consequence we obtain a simple proof of some results of Daskalopoulos, Hamilton and Sesum on the a priori estimates for the ancient solutions of Ricci flow on surfaces. We also give a simple proof for the solution to be a Rosenau solution under some mild conditions on the solutions of Ricci flow on surfaces.     

Counting Complex Points of Surfaces in ℂ2

We deal with complex points of two-dimensional surfaces. A short survey of basic results about complex points of smooth surfaces in ℂ² is presented at the beginning. For algebraic surfaces, a formula is proven which expresses the number of complex points as the local degree of an explicitly constructed polynomial endomorphism. Using this formula, some estimates for the number of complex points and the Maslov index are obtained in terms of algebraic degrees of defining equations with special attention paid to graphs of planar endomorphisms. Some estimates for the expected number of complex points of a random planar endomorphism are also obtained. __________ Translated from Sovremennaya Matematika i Ee Prilozheniya (Contemporary Mathematics and Its Applications), Vol. 15, Theory of Functions, 2004.     

Sharp Spectral Multipliers for a New Class of Grushin Type Operators

We describe weighted restriction (Plancherel) type estimates and sharp Hebisch-Müller-Stein type spectral multiplier result for a new class of Grushin type operators. We also discuss the optimal exponent for Bochner-Riesz summability in this setting.     

A generalization of the weighted Strichartz estimates for wave equations and an application to self‐similar solutions

Weighted Strichartz estimates with homogeneous weights with critical exponents are proved for the wave equation without a support restriction on the forcing term. The method of proof is based on expansion by spherical harmonics and on the Sobolev space over the unit sphere, by which the required estimates are reduced to the radial case. As an application of the weighted Strichartz estimates, the existence and uniqueness of self‐similar solutions to nonlinear wave equations are proved on up to five space dimensions. © 2006 Wiley Periodicals, Inc.     

Immersions of surfaces in almost-complex 4-manifolds

In this paper, we investigate the relation between double points and complex points of immersed surfaces in almost-complex 4-manifolds and show how estimates for the minimal genus of embedded surfaces lead to inequalities between the number of double points and the number of complex points of an immersion.

     

Resolvent Estimates Related with a Class of Dispersive Equations

We present a simple proof of the resolvent estimates of elliptic Fourier multipliers on the Euclidean space, and apply them to the analysis of time-global and spatially-local smoothing estimates of a class of dispersive equations. For this purpose we study in detail the properties of the restriction of Fourier transform on the unit cotangent sphere associated with the symbols of multipliers. The author was supported by the JSPS Grant-in-Aid for Scientific Research #17540140.     

Clustering of Eigenvalues on Translation Surfaces

We consider Riemannian surfaces in which there are many embedded Euclidean cylinders. We show that quantitative assumptions on the number of such cylinders provide estimates for the counting function of eigenvalues. These results in particular apply to translation surfaces. Communicated by Jens Marklof Submitted: 3/03/ 2005 Accepted: 18/11/2005     

Finite element approximations to surfaces of prescribed variable mean curvature

We give an algorithm for finding finite element approximations to surfaces of prescribed variable mean curvature, which span a given boundary curve. We work in the parametric setting and prove optimal estimates in the H¹ norm. The estimates are verified computationally.     

Curvature Estimates for Strongly Stable Domains on Surfaces with Constant Mean Curvature in Space Forms

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带有不等式约束的生长曲线模型中回归系数线性估计的泛容许性

对于带有不等式约束的生长曲线模型：Y=XBZ＋ε，ε^→～（0，σ^2V×I），tr（NB）≥0，本文在矩阵损失函数（d—KBL）（d—KBL）＇下，给出了可估函数KBL的线性估计的泛（西）容许性定义，分别得到了DYF和DYF＋C在齐次估计类LH和非齐次估计类LI中是KBL的泛容许性估计的充要条件．