arXiv subjects

Dror Varolin

Publications and source records attributed to Dror Varolin.

23 records · Page 2Linked to original sources

arXiv2004

Holomorphic DIffeomorphisms of Semisimple Homogeneous Spaces

The density property for a Stein manifold X implies that the group of holomorphic diffeomorphisms of X is infinite-dimensional and, in a certain well-defined sense, as large as possible. We prove that if G is a complex semisimple Lie group of adjoint type and K is a reductive subgroup, then G/K has the density property. This theorem is a non-trivial extension of an earlier result of ours, which handles the case of complex semi-simple Lie groups. We also establish the density property for some other complex homogeneous spaces by ad hoc methods. Finally, we introduce a lifting method that extends many results on complex manifolds with the density property to covering spaces of such manifolds.

math.CV↗

arXiv2004

Interpolation and Sampling Hypersurfaces for the Bargmann-Fock space in higher dimensions

We study those smooth complex hypersurfaces W in C^n having the property that all holomorphic functions of finite weighted L^p norm on W extend to entire functions with finite weighted L^p norm. Such hypersurfaces are called interpolation hypersurfaces. We also examine the dual problem of finding all sampling hypersurfaces, i.e., smooth hypersurfaces W in C^n such that any entire function with finite weighted L^p norm is stably determined by its restriction to W. We provide sufficient geometric conditions on the hypersurface to be an interpolation and sampling hypersurface. The geometric conditions that imply the extension property and the restriction property are given in terms of some directional densities.

math.CV↗

arXiv2003

Positivity conditions for Hermitian symmetric functions

We introduce a countable collection of positivity classes for Hermitian symmetric functions on a complex manifold, and establish their basic properties. We study a related notion of stability. The first main result shows that, if the underlying matrix of coefficients of an entire Hermitian symmetric function has at most k positive eigenvalues, then it can lie in the k-th positivity class only if it is a squared norm. We establish a similar result for Hermitian symmetric functions on the total space of a holomorphic line bundle. Finally we study the positivity classes for a natural one-parameter family of Hermitian metrics on a power of the universal bundle over complex projective space; we obtain sharp information about the parameter values in order to be in the k-th class. The paper closes with some additional information about the case when k is 2, where a nonlinear version of the Cauchy-Schwarz inequality arises.

math.CV↗

arXiv2003

Jumping Coefficients of Multiplier Ideals

We study in this paper some local invariants attached via multiplier ideals to an effective divisor or ideal sheaf on a smooth complex variety. First considered (at least implicitly) by Libgober and by Loeser and Vaquie, these jumping coefficients consist of an increasing sequence of rational numbers beginning with the log canonical threshold of the divisor or ideal in question. They encode interesting geometric and algebraic information, and we show that they arise naturally in several different contexts. Given a polynomial f having only isolated singularities, results of Varchenko, Loeser and Vaquie imply that if ξis a jumping number of f = 0 lying in the interval (0, 1], then -ξis a root of the Bernstein-Sato polynomial of f. We adapt an argument of Kollar to show prove that this holds also when the singular locus of f has positive dimension. In a more algebraic direction, we show that the number of such jumping coefficients bounds the uniform Artin-Rees number of the principal ideal (f) in the sense of Huneke: in the case of isolated singularities, this in turn leads to bounds involving the Milnor and Tyurina numbers of f . Along the way, we establish a general result relating multiplier to Jacobian ideals. We also explore the extension of these ideas to the setting of graded families of ideals. The paper contains many concrete examples.

math.AG↗

arXiv2002

Stable manifolds of holomorphic diffeomorphisms

We consider stable manifolds of a holomorphic diffeomorphism of a complex manifold. Using a conjugation of the dynamics to a (non-stationary) polynomial normal form, we show that typical stable manifolds are biholomorphic to complex Euclidean space.

math.CV↗