259 research outputs found
Determinantal Characterization of Canonical Curves and Combinatorial Theta Identities
We characterize genus g canonical curves by the vanishing of combinatorial
products of g+1 determinants of Brill-Noether matrices. This also implies the
characterization of canonical curves in terms of (g-2)(g-3)/2 theta identities.
A remarkable mechanism, based on a basis of H^0(K_C) expressed in terms of
Szego kernels, reduces such identities to a simple rank condition for matrices
whose entries are logarithmic derivatives of theta functions. Such a basis,
together with the Fay trisecant identity, also leads to the solution of the
question of expressing the determinant of Brill-Noether matrices in terms of
theta functions, without using the problematic Klein-Fay section sigma.Comment: 35 pages. New results, presentation improved, clarifications added.
Accepted for publication in Math. An
Generalized boundary strata classes
We describe a generalization of the usual boundary strata classes in the Chow
ring of . The generalized boundary strata classes
additively span a subring of the tautological ring. We describe a
multiplication law satisfied by these classes and check that every double
ramification cycle lies in this subring.Comment: For the Proceedings of the 2017 Abel Symposium, 10 page
Computing top intersections in the tautological ring of
We derive effective recursion formulae of top intersections in the
tautological ring of the moduli space of curves of genus .
As an application, we prove a convolution-type tautological relation in
.Comment: 18 page
Lectures on the Asymptotic Expansion of a Hermitian Matrix Integral
In these lectures three different methods of computing the asymptotic
expansion of a Hermitian matrix integral is presented. The first one is a
combinatorial method using Feynman diagrams. This leads us to the generating
function of the reciprocal of the order of the automorphism group of a tiling
of a Riemann surface. The second method is based on the classical analysis of
orthogonal polynomials. A rigorous asymptotic method is established, and a
special case of the matrix integral is computed in terms of the Riemann
-function. The third method is derived from a formula for the
-function solution to the KP equations. This method leads us to a new
class of solutions of the KP equations that are
\emph{transcendental}, in the sense that they cannot be obtained by the
celebrated Krichever construction and its generalizations based on algebraic
geometry of vector bundles on Riemann surfaces. In each case a mathematically
rigorous way of dealing with asymptotic series in an infinite number of
variables is established
A new species of the deep-bodied actinopterygian Dapedium from the Middle Jurassic (Aalenian) o f southwestern Germany
Dapedium is one of the most abundant and diverse genera of ganoid fishes from the Early Jurassic fossil lagerstatte of Europe. In spite of its abundance, however, its timing of extinction is poorly constrained, with the youngest described material being Early Jurassic in age. We describe new diagnostic and relatively complete material of a large species of Dapedium (standard length estimated at 50 cm) from the Middle Jurassic (earliest Aalenian) Opalinuston Formation of Baden-Wurttemberg, Germany. The Aalenian material represents a distinct species, D. ballei sp. nov., differing from Early Jurassic species in a unique combination of characters pertaining to the shape of the dermal skull elements, pectoral fin position, and scale shape and ornamentation. However, although D. ballei sp. nov. exhibits a unique combination of characters, there are no autapomorphies with which to distinguish it from the Toarcian species of Dapedium. Dapedium ballei represents the geologically youngest species of Dapedium, extending the range of this genus into the Middle Jurassic. The Opalinuston Formation fills an important gap in the marine vertebrate fossil record, and finds from this horizon have the potential to greatly improve our understanding of evolutionary dynamics over this period of faunal transition
On third Poisson structure of KdV equation
The third Poisson structure of KdV equation in terms of canonical ``free
fields'' and reduced WZNW model is discussed. We prove that it is
``diagonalized'' in the Lagrange variables which were used before in
formulation of 2D gravity. We propose a quantum path integral for KdV equation
based on this representation.Comment: 6pp, Latex. to appear in ``Proceedings of V conference on
Mathematical Physics, String Theory and Quantum Gravity, Alushta, June 1994''
Teor.Mat.Fiz. 199
Conformal blocks and generalized theta functions
Let M(r) be the moduli space of rank r vector bundles with trivial
determinant on a Riemann surface X . This space carries a natural line bundle,
the determinant line bundle L . We describe a canonical isomorphism of the
space of global sections of L^k with a space known in conformal field theory as
the ``space of conformal blocks", which is defined in terms of representations
of the Lie algebra sl(r, C((z))).Comment: 43 pages, Plain Te
On some differential-geometric aspects of the Torelli map
In this note we survey recent results on the extrinsic geometry of the
Jacobian locus inside . We describe the second fundamental form
of the Torelli map as a multiplication map, recall the relation between totally
geodesic subvarieties and Hodge loci and survey various results related to
totally geodesic subvarieties and the Jacobian locus.Comment: To appear on Boll. UMI, special volume in memory of Paolo de
Bartolomei
Menelaus relation and Fay's trisecant formula are associativity equations
It is shown that the celebrated Menelaus relation and Fay's trisecant formula
similar to the WDVV equation are associativity conditions for structure
constants of certain three-dimensional algebra.Comment: Talk given at the Conference " Mathematics and Physics of Solitons
and Integrable Systems", Dijon, 28.6-2.7, 2009. Minor misprints correcte
Brill–Noether general K3 surfaces with the maximal number of elliptic pencils of minimal degree
We explicitly construct Brill–Noether general K3 surfaces of genus 4, 6 and 8 having the maximal number of elliptic pencils of degrees 3, 4 and 5, respectively, and study their moduli spaces and moduli maps to the moduli space of curves. As an application we prove the existence of Brill–Noether general K3 surfaces of genus 4 and 6 without stable Lazarsfeld–Mukai bundles of minimal c2.publishedVersio
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