parameter orthogonality and approximate conditional inference on propose une statistique du rapport de vraisemblance construite a partir de la distribution conditionnelle des observations etant donne les estimateurs du maximum de vraisemblance pour les parametres de nuisance

estimating the parameters of a convolution by maximum likelihood abstract in the present age of computer sophistication computational difficulty is no longer a justification for seeking alternative and inefficient estimation procedures in place of maximum likelihood estimation particularly when there are only two or three parameters to be estimated convolution densities are an example where this has occurred it is shown that in a large class of such densities the maximum likelihood equations can be reduced by one thus for a two parameter family only a single equation need be solved iteratively the required formulas are derived the problem of basing inferences on the resulting maximum likelihood estimates is briefly discussed

poisson structures on moduli spaces of sheaves over poisson surfaces we introduce and study the notion of poisson surface we prove that the choice of a poisson structure on a surfaces canonically determines a poisson structure on the moduli space of stable sheaves ons this result generalizes previous results obtained by mukai 14 for abelian ork3 surfaces and by tyurin 16

gromov witten pairs correspondence for the quintic 3 fold we use the gromov witten pairs descendent correspondence for toric 3 folds and degeneration arguments to establish the gw p correspondence for several compact calabi yau 3 folds including all cy complete intersections in products of projective spaces a crucial aspect of the proof is the study of the gw p correspondence for descendents in relative geometries projective bundles over surfaces relative to a section play a special role the gw p correspondence for calabi yau complete intersections provides a structure result for the gromov witten invariants in a fixed curve class after change of variables the gromov witten series is a rational function in the variable q eiu invariant under q q 1

detection and localization of multiple sources via the stochastic signals model a method for the detection of coherent and noncoherent signals based on the application of j rissanen s 1978 minimum description length principle for model selection to the stochastic signals model is presented the detection and localization are done simultaneously with the location estimator coinciding with the maximum likelihood estimator derived by j f bohme 1986 the proposed method outperforms the method of m wax and i ziskind 1989 especially in the threshold region simulation results demonstrating the improved performance are included

motivic degree zero donaldson thomas invariants given a smooth complex threefold x we define the virtual motive operatorname hilb n x operatorname vir of the hilbert scheme of n points on x in the case when x is calabi yau operatorname hilb n x operatorname vir gives a motivic refinement of the n point degree zero donaldson thomas invariant of x the key example is x 3 where the hilbert scheme can be expressed as the critical locus of a regular function on a smooth variety and its virtual motive is defined in terms of the denef loeser motivic nearby fiber a crucial technical result asserts that if a function is equivariant with respect to a suitable torus action its motivic nearby fiber is simply given by the motivic class of a general fiber this allows us to compute the generating function of the virtual motives operatorname hilb n mathbb c 3 operatorname vir via a direct computation involving the motivic class of the commuting variety we then give a formula for the generating function for arbitrary x as a motivic exponential generalizing known results in lower dimensions the weight polynomial specialization leads to a product formula in terms of deformed macmahon functions analogous to gottsche s formula for the poincare polynomials of the hilbert schemes of points on surfaces

deformation obstruction theory for complexes via atiyah and kodaira spencer classes we give a universal approach to the deformation obstruction theory of objects of the derived category of coherent sheaves over a smooth projective family we recover and generalise the obstruction class of lowen and lieblich and prove that it is a product of atiyah and kodaira spencer classes this allows us to obtain deformation invariant virtual cycles on moduli spaces of objects of the derived category on threefolds

orientability for gauge theories on calabi yau manifolds abstract we study orientability issues of moduli spaces from gauge theories on calabi yau manifolds our results generalize and strengthen those for donaldson thomas theory on calabi yau manifolds of dimensions 3 and 4 we also prove a corresponding result in the relative situation which is relevant to the gluing formula in dt theory

parameter orthogonality for a family of discrete distributions abstract the standard contagious distributions see douglas 1980 have been used in such varied fields as biology and automobile insurance often to model various physical phenomena as well as provide a good fit to count data when other models are inadequate unfortunately the parameterizations often used when working with these distributions normally lead to extremely high correlations of the maximum likelihood estimators mle s this tends to lead to mathematical complexities and causes difficulty or even errors in their interpretation furthermore numerical difficulties may arise when using numerical procedures to locate the estimates some of these difficulties were discussed by douglas 1980 pp 171 204 205 who suggested that a reparameterization to reduce or even eliminate such correlation is desirable if the mle s are asymptotically uncorrelated the parameterization is orthogonal philpot 1964 derived an orthogonal parameterization for the neyman type a distribution stein zucchini an

parameter estimation for the sichel distribution and its multivariate extension abstract the sichel distribution is a three parameter compound poisson distribution it is a versatile model for highly skewed frequency distributions of observed counts and has proved useful in fields as diverse as mining engineering linguistics ecology industrial psychology and market research we propose a reparameterization of the sichel distribution and give an algorithm which can be implemented on a typical desktop microcomputer for computing the maximum likelihood estimates of the new parameters the reparameterization has a number of advantages over the old in the important two parameter special case of the sichel distribution known as the inverse gaussian poisson the new parameters are the population mean and a shape parameter and their maximum likelihood estimators are asymptotically uncorrelated the reparameterization also lends itself to the convenient multivariate extension presented here this distribution is well suited for modeling correlated count data whose marginal distribution

on the construction of a parameter orthogonal to the mean it is shown that for many parametric families the condition for a parameter to be orthogonal to the mean takes on a particularly simple form as a result it is often possible to obtain analytically an explicit orthogonal parameter thus providing insight into the many situations involving parametric families in which such a parameter is known to exist orthogonal parameterizations are then given for some other models

the orientation of yang mills moduli spaces and 4 manifold topology si x est une 4 variete lisse orientee fermee dont la forme intersection q h 2 x z torsion z est definie negative alors la forme est equivalente sur les entiers a la forme standard 1 1 1 soit x une 4 variete lisse orientee fermee avec les trois proprietes suivantes 1 h 1 x z n a pas de 2 torsion 2 la forme intersection q sur h 2 x torsion a une partie positive de rang 1 ou 2 3 la forme intersection est paire alors q est equivalente sur les entiers a une des formes 01 10 01 10 01 10

braid group actions on derived categories of coherent sheaves this paper gives a construction of braid group actions on the derived category of coherent sheaves on a variety x the motivation for this is m kontsevich s homological mirror conjecture together with the occurrence of certain braid group actions in symplectic geometry one of the main results is that when dim x geq 2 our braid group actions are always faithful we describe conjectural mirror symmetries between smoothings and resolutions of singularities which lead us to find examples of braid group actions arising from crepant resolutions of various singularities relations with the mckay correspondence and with exceptional sheaves on fano manifolds are given moreover the case of an elliptic curve is worked out in some detail

an application of gauge theory to four dimensional topology soit x une u variete compacte reguliere simplement connexe orientee avec la propriete que la forme associee q est definie positive alors cette forme est equivalente sur les entiers a la forme diagonale standard soit dans une base q u 1 u 2 u 2 u 2 1 u 2 2 u 2 2