Search results for "Algebraic Geometry"

The Fatou coordinate for parabolic Dulac germs

2017

We study the class of parabolic Dulac germs of hyperbolic polycycles. For such germs we give a constructive proof of the existence of a unique Fatou coordinate, admitting an asymptotic expansion in the power-iterated log scale.

Zur Spektralinvarianz von Algebren von Pseudodifferentialoperatoren in derL p -Theorie

1988

Die Hormander-Klassen Ψ1,δ0 (0≤δ<1) von Pseudodifferentialoperatoren sind Ψ-Algebren. Insbesondere ist die Inverse eines inL(Lp(ℝn)) invertierbaren Pseudodifferentialoperators der Klasse Ψ1,δ0 selbst wieder ein Pseudodifferential-operator derselben Klasse.

Regular orbits of hall π-subgroups

1991

On BLD-mappings with small distortion

2021

We show that every $$L$$ -BLD-mapping in a domain of $$\mathbb {R}^{n}$$ is a local homeomorphism if $$L < \sqrt{2}$$ or $$K_I(f) < 2$$ . These bounds are sharp as shown by a winding map.

Lipschitz classes and the Hardy-Littlewood property

1993

We study the geometry of plane domains and the uniform Holder continuity properties of analytic functions.

Logarithmic Vector Fields and the Severi Strata in the Discriminant

2017

The discriminant, D, in the base of a miniversal deformation of an irreducible plane curve singularity, is partitioned according to the genus of the (singular) fibre, or, equivalently, by the sum of the delta invariants of the singular points of the fibre. The members of the partition are known as the Severi strata. The smallest is the δ-constant stratum, D(δ), where the genus of the fibre is 0. It is well known, by work of Givental’ and Varchenko, to be Lagrangian with respect to the symplectic form Ω obtained by pulling back the intersection form on the cohomology of the fibre via the period mapping. We show that the remaining Severi strata are also co-isotropic with respect to Ω, and mor…

Frobenius polynomials for Calabi–Yau equations

2008

We describe a variation of Dwork’ s unit-root method to determine the degree 4 Frobenius polynomial for members of a 1-modulus Calabi–Yau family over P1 in terms of the holomorphic period near a point of maximal unipotent monodromy. The method is illustrated on a couple of examples from the list [3]. For singular points, we find that the Frobenius polynomial splits in a product of two linear factors and a quadratic part 1− apT + p3T 2. We identify weight 4 modular forms which reproduce the ap as Fourier coefficients.

Skeleta of affine hypersurfaces

2014

A smooth affine hypersurface Z of complex dimension n is homotopy equivalent to an n-dimensional cell complex. Given a defining polynomial f for Z as well as a regular triangulation of its Newton polytope, we provide a purely combinatorial construction of a compact topological space S as a union of components of real dimension n, and prove that S embeds into Z as a deformation retract. In particular, Z is homotopy equivalent to S.

Approximation by uniform domains in doubling quasiconvex metric spaces

2020

We show that any bounded domain in a doubling quasiconvex metric space can be approximated from inside and outside by uniform domains.

A construction of equivariant bundles on the space of symmetric forms

2021

We construct stable vector bundles on the space of symmetric forms of degree d in n+1 variables which are equivariant for the action of SL_{n+1}(C), and admit an equivariant free resolution of length 2. For n=1, we obtain new examples of stable vector bundles of rank d-1 on P^d, which are moreover equivariant for SL_2(C). The presentation matrix of these bundles attains Westwick's upper bound for the dimension of vector spaces of matrices of constant rank and fixed size.