handlebody construction of stein surfaces the topology of stein surfaces and contact 3 manifolds is studied by means of handle decompositions a simple characterization of homeomorphism types of stein surfaces is obtained they correspond to open handlebodies with all handles of index 2 an uncountable collection of exotic l4 s is shown to admit stein structures new invariants of contact 3 manifolds are produced including a complete and computable set of invariants for determining the homotopy class of a 2 plane field on a 3 manifold these invariants are applicable to seiberg witten theory several families of oriented 3 manifolds are examined namely the seifert fibered spaces and all surgeries on various links in s3 and in each case it is seen that most members of the family are the

fast dual mgs block factorization algorithm for dense mom matrices a robust method is introduced for efficiently compressing dense method of moments mom matrices using a dual modified gram schmidt block qr factorization algorithm based on low rank singular value decomposition the compression is achieved without generating the full matrix or even full subblocks of the matrix the compressed matrix may then be used in the iterative solution of the mom problem the method is very robust because it uses a reduced set of the original matrix entries to perform the compression furthermore it does not depend on the analytic form of the green s function so it may be applied to arbitrarily complex media

on symplectic cobordisms in this note we make several observations concerning symplectic cobordisms among other things we show that every contact 3 manifold has infinitely many concave symplectic fillings and that all overtwisted contact 3 manifolds are symplectic cobordism equivalent

solution of electrically large problems with multilevel characteristic basis functions we present a multilevel version to the characteristic basis function method cbfm this technique extends the range of applicability of the conventional cbfm and allows a direct solution of problems even when they exceed 250 000 degrees of freedom in this paper it is shown how we can use the multilevel cbfm which is a natural extension of the conventional approach and which saves both time and memory and yet retains excellent accuracy in the computed far fields also the adaptive cross algorithm is used for fast calculation of the interaction between the blocks in the process of generating the reduced matrix

on the classification of tight contact structures ii we present complete classification results for tight contact structures on two classes of 3 manifolds i torus bundles which fiber over the circle and ii circle bundles which fiber over closed surfaces

density of rational points on del pezzo surfaces of degree one we state conditions under which the set s k of k rational points on a del pezzo surface s of degree 1 over an infinite field k of characteristic not equal to 2 or 3 is zariski dense for example it suffices to require that the elliptic fibration s p 1 induced by the anticanonical map has a nodal fiber over a k rational point of p 1 it also suffices to require the existence of a point in s k that does not lie on six exceptional curves of s and that has order 3 on its fiber of the elliptic fibration this allows us to show that within a parameter space for del pezzo surfaces of degree 1 over r the set of surfaces s defined over q for which the set s q is zariski dense is dense with respect to the real analytic topology we also include conditions that may be satisfied for every del pezzo surface s and that can be verified with a finite computation for any del pezzo surface s that does satisfy them c 2014 elsevier inc all rights reserved

the contact invariant in sutured floer homology we describe an invariant of a contact 3 manifold with convex boundary as an element of juhasz s sutured floer homology our invariant generalizes the contact invariant in heegaard floer homology in the closed case due to ozsvath and szabo

admissible transverse surgery does not preserve tightness we produce the first examples of closed tight contact 3 manifolds which become overtwisted after performing admissible transverse surgeries along the way we clarify the relationship between admissible transverse surgery and legendrian surgery we use this clarification to study a new invariant of transverse knots namely the range of slopes on which admissible transverse surgery preserves tightness and to provide some new examples of knot types which are not uniformly thick our examples also illuminate several interesting new phenomena including the existence of hyperbolic universally tight contact 3 manifolds whose heegaard floer contact invariants vanish and which are not weakly fillable and the existence of open books with arbitrarily high fractional dehn twist coefficients whose compatible contact structures are not deformations of co orientable taut foliations

fast analysis of large antenna arrays using the characteristic basis function method and the adaptive cross approximation algorithm the characteristic basis function method cbfm has been hybridized with the adaptive cross approximation aca algorithm to construct a reduced matrix equation in a time efficient manner and to solve electrically large antenna array problems in core with a solve time orders of magnitude less than those in the conventional methods various numerical examples are presented that demonstrate that the proposed method has a very good accuracy computational efficiency and reduced memory storage requirement specifically we analyze large 1 d and 2 d arrays of electrically interconnected tapered slot antennas tsas the entire computational domain is subdivided into many smaller subdomains each of which supports a set of characteristic basis functions cbfs we also present a novel scheme for generating the cbfs that do not conform to the edge condition at the truncated edge of each subdomain and provide a minor overlap between the cbfs in adjacent subdomains as a result the cbfs preserve the continuity of the surface current across the subdomain interfaces thereby circumventing the need to use separate ldquoconnectionrdquo basis functions

a fast impedance and pattern computation scheme for finite antenna arrays a fast numerical method well suited to the analysis of moderate size arrays made of complex elements is presented it combines macro basis functions and multipole approaches without an iterative procedure this method is exploited to estimate the impedance matrix and active element patterns for the latter an efficient formulation is provided as a series of pattern multiplication problems examples are shown for arrays of broadband dipoles the computational gain obtained for the reduction of the original method of moments system of equations is briefly described

analysis of large complex structures with the synthetic functions approach an innovative procedure is presented that allows the method of moments mom analysis of large and complex antenna and scattering problems at a reduced memory and cpu cost bounded within the resources provided by a standard 32 bit personal computer the method is based on the separation of the overall geometry into smaller portions called blocks and on the degrees of freedom of the field the blocks need not be electrically unconnected on each block basis functions are generated with support on the entire block that are subsequently used as basis functions for the analysis of the complete structure only a small number of these functions is required to obtain an accurate solution therefore the overall number of unknowns is drastically reduced with consequent impact on storage and solution time these entire domain basis functions are called synthetic functions they are generated from the solution of the electromagnetic problem for the block in isolation under excitation by suitably defined sources the synthetic functions are obtained from the responses to all sources via a procedure based on the singular value decomposition because of the strong reduction of the global number of unknowns one can store the mom matrix and afford a direct solution the method is kernel free and can be implemented on existing mom codes

application of the characteristic basis function method utilizing a class of basis and testing functions defined on nurbs patches a novel implementation of the characteristic basis function method cbfm is given in which the high level basis functions called characteristic basis functions cbfs are represented in terms of curved rooftops generated from nonuniform rational b splines nurbs in the parametric u v domain the associated macro testing functions are defined by using curved razor blade functions corresponding to each rooftop the underlying objective of the cbfm is the reduction of the number of unknowns that arise from the discretization process when applying the conventional method of moments mom the result is therefore an approach which can handle many complex cases via direct solvers without suffering from convergence problems as many of the iterative techniques are known to do when dealing with ill conditioned matrices as a result of the combination of the cbfm with the special class of low level basis and testing functions directly located over nurbs surfaces complex and realistic geometries can be efficiently analyzed to yield accurate results while reducing the cpu time as well as required memory resources

on the thurston bennequin invariant of legendrian knots and non exactness of bennequin s inequality in this paper we show that bennequin s inequality is highly non exact with respect to legendrian simple closed curves of certain topological types

generation of excitation independent characteristic basis functions for three dimensional homogeneous dielectric bodies the aim of this paper is the development of characteristic basis functions cbfs for homogeneous dielectric bodies that are modeled with the surface equivalence principle this approach contributes to generalize the characteristic basis function method cbfm for any kind of material the foundations for the generation of these new basis functions are widely revised and the cbfm is adapted for this purpose the validity of the method is illustrated with the systematic analysis of canonical geometries as well as with the computation of the specific absorption rate inside a head like geometry in all the cases the error in the current distribution as well as in the near and far field is considered in addition a detailed comparison of the generation of the cbfs using plane waves and spherical waves is also carried out

an iteration free mom approach based on excitation independent characteristic basis functions for solving large multiscale electromagnetic scattering problems we describe a numerically efficient strategy for solving a linear system of equations arising in the method of moments for solving electromagnetic scattering problems this novel approach termed as the characteristic basis function method cbfm is based on utilizing characteristic basis functions cbfs special functions defined on macro domains blocks that include a relatively large number of conventional sub domains discretized by using triangular or rectangular patches use of these basis functions leads to a significant reduction in the number of unknowns and results in a substantial size reduction of the mom matrix this in turn enables us to handle the reduced matrix by using a direct solver without the need to iterate in addition the paper shows that the cbfs can be generated by using a sparse representation of the impedance matrix resulting in lower computational cost and that in contrast to the iterative techniques multiple excitations can be handled with only a small overhead another important attribute of the cbfm is that it is readily parallelized numerical results that demonstrate the accuracy and time efficiency of the cbfm for several representative scattering problems are included in the paper

right veering diffeomorphisms of compact surfaces with boundary we initiate the study of the monoid of right veering diffeomorphisms on a compact oriented surface with nonempty boundary the monoid strictly contains the monoid of products of positive dehn twists we explain the relationship to tight contact structures and open book decompositions

log fano varieties over function fields of curves consider a smooth log fano variety over the function field of a curve suppose that the boundary has positive normal bundle choose an integral model over the curve then integral points are zariski dense after removing an explicit finite set of points on the base curve

tight contact structures with no symplectic fillings we exhibit tight contact structures on 3 manifolds that do not admit any symplectic fillings