julilili42/papers huggingface dataset:
Mirror Symmetry and Toric Degenerations of Partial Flag Manifolds
2022-03-19

In this paper we propose and discuss a mirror construction for complete intersections in partial flag manifolds . This construction includes our previous mirror construction for complete intersection in Grassmannians and the mirror construction of Givental for complete flag manifolds. The key idea of our construction is a degeneration of to a certain Gorenstein toric Fano variety which has been investigated by Gonciulea and Lakshmibai. We describe a natural small crepant desingularization of and prove a generalized version of a conjecture of Gonciulea and Lakshmibai on the singular locus of .
Symmetries and reversing symmetries of trace maps
2022-03-19

A (discrete) dynamical system may have various symmetries and reversing symmetries, which together form its so-called reversing symmetry group. We study the set of 3D trace maps (obtained from two-letter substitution rules) which preserve the Fricke-Vogt invariant I(x,y,z). This set of dynamical systems forms a group G isomorphic with the projective linear (or modular) group PGL(2,Z). For such trace maps, we give a complete characterization of the reversing symmetry group as a subgroup of the group A of all polynomial mappings that preserve I(x,y,z).
Representing Constraints with Automata
2022-03-19

In this paper we describe an approach to constraint-based syntactic theories in terms of finite tree automata. The solutions to constraints expressed in weak monadic second order (MSO) logic are represented by tree automata recognizing the assignments which make the formulas true. We show that this allows an efficient representation of knowledge about the content of constraints which can be used as a practical tool for grammatical theory verification. We achieve this by using the intertranslatability of formulas of MSO logic and tree automata and the embedding of MSO logic into a constraint logic programming scheme. The usefulness of the approach is discussed with examples from the realm of Principles-and-Parameters based parsing.
Vortex induced confinement and the Kugo-Ojima confinement criterion
2022-03-19

The SU(2) Yang-Mills gluon and ghost Green-functions are studied in Landau gauge by means of lattice gauge simulations. A focal point is their low energy behavior since in particular the Kugo-Ojima confinement criterion relates a diverging ghost form factor at vanishing momentum transfer to the confining capabilities of the theory. This divergence is verified by numerical simulations. Removing the confining vortices from the lattice ensembles converts SU(2) Yang-Mills theory in a non-confining theory. It is shown that in this modified theory the divergence of the ghost propagator disappears.
Calculating initial data for the conformal Einstein equations by pseudo-spectral methods
2022-03-19

We present a numerical scheme for determining hyperboloidal initial data sets for the conformal field equations by using pseudo-spectral methods. This problem is split into two parts. The first step is the determination of a suitable conformal factor which transforms from an initial data set in physical space-time to a hyperboloidal hypersurface in the ambient conformal manifold. This is achieved by solving the Yamabe equation, a non-linear second order equation. The second step is a division by the conformal factor of certain fields which vanish on , the zero set of the conformal factor. The challenge there is to numerically obtain a smooth quotient. Both parts are treated by pseudo-spectral methods. The non-linear equation is solved iteratively while the division problem is treated by transforming the problem to the coefficient space, solving it there by the QR-factorisation of a suitable matrix, and then transforming back. These hyperboloidal initial data can be used to generate general relativistic space-times by evolution with the conformal field equations.
A guide to mathematical quasicrystals
2022-03-19

This introductory survey deals with mathematical and physical properties of discrete structures such as point sets and tilings. The emphasis is on proper generalizations of concepts and ideas from classical crystallography. In particular, we focus on their interplay with various physically motivated equivalence concepts such as local indistinguishability and local equivalence. Various discrete patterns with non-crystallographic symmetries are described in detail, and some of their magic properties are introduced. This perfectly ordered world is augmented by a brief introduction to the stochastic world of random tilings.
Learning Computational Grammars
2022-03-19

This paper reports on the "Learning Computational Grammars" (LCG) project, a postdoc network devoted to studying the application of machine learning techniques to grammars suitable for computational use. We were interested in a more systematic survey to understand the relevance of many factors to the success of learning, esp. the availability of annotated data, the kind of dependencies in the data, and the availability of knowledge bases (grammars). We focused on syntax, esp. noun phrase (NP) syntax.
Stochastic Attribute-Value Grammars
2022-03-19

Probabilistic analogues of regular and context-free grammars are well-known in computational linguistics, and currently the subject of intensive research. To date, however, no satisfactory probabilistic analogue of attribute-value grammars has been proposed: previous attempts have failed to define a correct parameter-estimation algorithm. In the present paper, I define stochastic attribute-value grammars and give a correct algorithm for estimating their parameters. The estimation algorithm is adapted from Della Pietra, Della Pietra, and Lafferty (1995). To estimate model parameters, it is necessary to compute the expectations of certain functions under random fields. In the application discussed by Della Pietra, Della Pietra, and Lafferty (representing English orthographic constraints), Gibbs sampling can be used to estimate the needed expectations. The fact that attribute-value grammars generate constrained languages makes Gibbs sampling inapplicable, but I show how a variant of Gibbs sampling, the Metropolis-Hastings algorithm, can be used instead.
Quantitative Constraint Logic Programming for Weighted Grammar Applications
2022-03-19

Constraint logic grammars provide a powerful formalism for expressing complex logical descriptions of natural language phenomena in exact terms. Describing some of these phenomena may, however, require some form of graded distinctions which are not provided by such grammars. Recent approaches to weighted constraint logic grammars attempt to address this issue by adding numerical calculation schemata to the deduction scheme of the underlying CLP framework. Currently, these extralogical extensions are not related to the model-theoretic counterpart of the operational semantics of CLP, i.e., they do not come with a formal semantics at all. The aim of this paper is to present a clear formal semantics for weighted constraint logic grammars, which abstracts away from specific interpretations of weights, but nevertheless gives insights into the parsing problem for such weighted grammars. Building on the formalization of constraint logic grammars in the CLP scheme of Hoehfeld and Smolka 1988, this formal semantics will be given by a quantitative version of CLP. Such a quantitative CLP scheme can also be valuable for CLP tasks independent of grammars.
Extension of CR-functions on wedges
2022-03-19

Given a wedge V with generic edge in a submanifold M of , in general, CR-functions on V do not extend to a wedge in in the direction of each nontrivial value of the Levi form of M as was recently observed by Eastwood and Graham. In this paper we propose an invariant geometric way of selecting those Levi form directions that are responsible for the extension. These are the Levi form directions of the complex tangent vectors, whose complex planes intersect the tangent cone to the wedge in angles larger than . We show by several examples the optimality of this criterion. Applications to regularity of CR-functions are also given generalizing the edge-of-the-wedge theorem of Ajrapetyan-Henkin.
Reversing Symmetry Groups of Cat Maps
2022-03-19

Toral automorphisms are widely used (discrete) dynamical systems, the perhaps most prominent example (in 2D) being Arnold's cat map. Given such an automorphism M, its symmetries (i.e. all automorphisms that commute with M) and reversing symmetries (i.e. all automorphisms that conjugate M into its inverse) can be determined by means of number theoretic tools. Here, the case of GL(2,Z) is presented and the possible (reversing) symmetry groups are completely classified. Extensions to affine mappings and to k-(reversing) symmetries (i.e. (reversing) symmetries of the k-th power of M), and applications to the projective group PGL(2,Z) and to trace maps (compare math.DS/9901124), are briefly discussed.
Towards asteroseismology of the non-radial pulsating sdB star PG 1605+072
2022-03-19

The recently discovered new class of sdB pulsators (sdBV) offers a powerful possibility for the investigation of their interior and thus their evolutionary history. The first step towards applying asteroseismologic tools is the identification of pulsation modes. We reoport on simultaneous spectroscopic and multi-band photometric time series observations of PG 1605+072 and analyse its radial velocity and light curve.
Metal abundances in PG1159 stars from Chandra and FUSE spectroscopy
2022-03-19

We investigate FUSE spectra of three PG1159 stars and do not find any evidence for iron lines. From a comparison with NLTE models we conclude a deficiency of 1-1.5 dex. We speculate that iron was transformed into heavier elements. A soft X-ray Chandra spectrum of the unique H- and He-deficient star H1504+65 is analyzed. We find high neon and magnesium abundances and confirm that H1504+65 is the bare core of either a C-O or a O-Ne-Mg white dwarf.
Regular minimal nets on surfaces of constant negative curvature
2022-03-19

An embedded cubic graph consisting of segments of geodesics such that the angles at any vertex are equal to is a closed local minimal net. This net is regular if all segments of geodesics are equal. The problem of classification of closed local minimal nets on surfaces of constant negative curvature has been formulated in the context of the famous Plateau problem in the one-dimensional case. In this paper we prove an asymptotic for as where is genus and is the set of the regular single-face minimal nets on surfaces of curvature -1. Then we construct some examples of -face regular nets, .
A fast X-ray timing capability on XEUS
2022-03-19

The Rossi X-ray Timing Explorer has demonstrated that fast X-ray timing can be used to probe strong gravity fields around collapsed objects and constrain the equation of state of dense matter in neutron stars. These studies require extremely good photon statistics. In view of the huge collecting area of its mirrors, XEUS could make a unique contribution to this field. For this reason, it has been proposed to include a fast X-ray timing capability in the focal plane of the XEUS mirrors. We outline the scientific motivation for such a capability, present some sensitivity estimates, and discuss briefly a possible detector implementation.
Non-Equilibrium and Collective Flow Effects in Relativistic Heavy Ion Collisions
2022-03-19

We discuss the problems involved in extracting the nuclear equation-of-state from heavy-ion collisions. We demonstrate that the equation of state becomes effectively softer in non-equilibrium and this effect is observable in terms of collective flow effects. Thus, non-equilibrium effects must be included in transport descriptions on the level of the effective mean fields. A comparison with transverse momentum, rapidity, and centrality selected flow data show the reliability and limitations of the underlying interaction which was derived from microscopic Dirac-Brueckner (DB) results.
Timing analysis of the Seyfert-1 galaxy MCG-6-30-15 with XMM-Newton data
2022-03-19

We present the main results of a deep timing analysis (in the 0.2-10 keV energy band) of the bright Seyfert-1 galaxy MCG-6-30-15 performed on XMM-Newton data. The light-curves and hardness ratios show that the source has large flux and spectral variations on time-scales of a few kiloseconds at most. From the analysis of both the power spectra and the structure function of the light curves we detected a relevant source variability between time-scales of ~0.3 and ~10 ks. Based on this result, we extracted a characteristic size of the X-ray emitting region of the order of 10^13 cm.
Averaged shelling for quasicrystals
2022-03-19

The shelling of crystals is concerned with counting the number of atoms on spherical shells of a given radius and a fixed centre. Its straight-forward generalization to quasicrystals, the so-called central shelling, leads to non-universal answers. As one way to cope with this situation, we consider shelling averages over all quasicrystal points. We express the averaged shelling numbers in terms of the autocorrelation coefficients and give explicit results for the usual suspects, both perfect and random.
Algebraicity of local holomorphisms between real-algebraic submanifolds of complex spaces
2022-03-19

We prove that a germ of a holomorphic map between and sending one real-algebraic submanifold into another is algebraic provided contains no complex-analytic discs and is generic and minimal. We also propose an algorithm for finding complex-analytic discs in a real submanifold.
Modularizing Contexted Constraints
2022-03-19

This paper describes a method for compiling a constraint-based grammar into a potentially more efficient form for processing. This method takes dependent disjunctions within a constraint formula and factors them into non-interacting groups whenever possible by determining their independence. When a group of dependent disjunctions is split into smaller groups, an exponential amount of redundant information is reduced. At runtime, this means that an exponential amount of processing can be saved as well. Since the performance of an algorithm for processing constraints with dependent disjunctions is highly determined by its input, the transformation presented in this paper should prove beneficial for all such algorithms.
Diffraction from visible lattice points and k-th power free integers
2022-03-19

We prove that the set of visible points of any lattice of dimension at least 2 has pure point diffraction spectrum, and we determine the diffraction spectrum explicitly. This settles previous speculation on the exact nature of the diffraction in this situation, see math-ph/9903046 and references therein. Using similar methods we show the same result for the 1-dimensional set of k-th power free integers with k at least 2. Of special interest is the fact that neither of these sets is a Delone set --- each has holes of unbounded inradius. We provide a careful formulation of the mathematical ideas underlying the study of diffraction from infinite point sets.
Stringy Hodge numbers and Virasoro algebra
2022-03-19

Let be an arbitrary smooth -dimensional projective variety. It was discovered by Libgober and Wood that the product of the Chern classes depends only on the Hodge numbers of . This result has been used by Eguchi, Jinzenji and Xiong in their approach to the quantum cohomology of via a representation of the Virasoro algebra with the central charge . In this paper we define for singular varieties a rational number which is a stringy version of the number for smooth -folds. We show that the number can be expressed in the same way using the stringy Hodge numbers of . Our results provides an evidence for the existence of an approach to quantum cohomology of singular varieties via a representation of the Virasoro algebra whose central charge is the rational number which equals the stringy Euler number of .
Magic for Filter Optimization in Dynamic Bottom-up Processing
2022-03-19

Off-line compilation of logic grammars using Magic allows an incorporation of filtering into the logic underlying the grammar. The explicit definite clause characterization of filtering resulting from Magic compilation allows processor independent and logically clean optimizations of dynamic bottom-up processing with respect to goal-directedness. Two filter optimizations based on the program transformation technique of Unfolding are discussed which are of practical and theoretical interest.
Polynomial Time Data Reduction for Dominating Set
2022-03-19

Dealing with the NP-complete Dominating Set problem on undirected graphs, we demonstrate the power of data reduction by preprocessing from a theoretical as well as a practical side. In particular, we prove that Dominating Set restricted to planar graphs has a so-called problem kernel of linear size, achieved by two simple and easy to implement reduction rules. Moreover, having implemented our reduction rules, first experiments indicate the impressive practical potential of these rules. Thus, this work seems to open up a new and prospective way how to cope with one of the most important problems in graph theory and combinatorial optimization.
Transducers from Rewrite Rules with Backreferences
2022-03-19

Context sensitive rewrite rules have been widely used in several areas of natural language processing, including syntax, morphology, phonology and speech processing. Kaplan and Kay, Karttunen, and Mohri &amp; Sproat have given various algorithms to compile such rewrite rules into finite-state transducers. The present paper extends this work by allowing a limited form of backreferencing in such rules. The explicit use of backreferencing leads to more elegant and general solutions.
On crepant resolutions of 2-parameter series of Gorenstein cyclic quotient singularities
2022-03-19

An immediate generalization of the classical McKay correspondence for Gorenstein quotient spaces in dimensions would primarily demand the existence of projective, crepant, full desingularizations. Since this is not always possible, it is natural to ask about special classes of such quotient spaces which would satisfy the above property. In this paper we give explicit necessary and sufficient conditions under which 2-parameter series of Gorenstein cyclic quotient singularities have torus-equivariant resolutions of this specific sort in all dimensions.
Testing Dirac-Brueckner models in collective flow of heavy-ion collisions
2022-03-19

We investigate differential in-plane and out-of-plane flow observables in heavy ion reactions at intermediate energies from AGeV within the framework of relativistic BUU transport calculations. The mean field is based on microscopic Dirac-Brueckner-Hartree-Fock (DBHF) calculations. We apply two different sets of DBHF predictions, those of ter Haar and Malfliet and more recent ones from the Tübingen group, which are similar in general but differ in details. The latter DBHF calculations exclude spurious contributions from the negative energy sector to the mean field which results in a slightly softer equation of state and a less repulsive momentum dependence of the nucleon-nucleus potential at high densities and high momenta. For the application to heavy ion collisions in both cases non-equilibrium features of the phase space are taken into account on the level of the effective interaction. The systematic comparison to experimental data favours the less repulsive and softer model. Relative to non-relativistic approaches one obtains larger values of the effective nucleon mass. This produces a sufficient amount of repulsion to describe the differential flow data reasonably well.
Transition Radiation of Moving Abrikosov Vortices
2022-03-19

We show that Abrikosov vortices moving towards the surface of a superconductor emit electromagnetic radiation into free space. The frequency distribution of the radiated intensity displays a pronounced maximum at microwave frequencies around v_x/lambda, where lambda is the magnetic penetration length. Coherent motion of a lattice of flux lines leads to constructive interference and increases the strength of the radiated power by a large factor.
Domains of holomorphy with edges and lower dimensional boundary singularities
2022-03-19

Necessary and sufficient geometric conditions are given for domains with regular boundary points and edges to be domains of holomorphy provided the remainder boundary subset is of zero Hausdorff 1-codimensional measure.
Exclusive rare decays of B and B_c mesons in a relativistic quark model
2022-03-19

In these lectures we give, first, the model-independent analysis of the exclusive rare decays B -&gt; K l(bar) l and B_c -&gt; D(D*) l(bar) l with special emphasis on the cascade decay B_c -&gt; D(*)(-&gt; D pi) l(bar) l. We derive a four-fold angular decay distribution for this process in terms of helicity amplitudes including lepton mass effects. The four-fold angular decay distribution allows to define a number of physical observables which are amenable to measurement. Second, we calculate the relevant form factors within a relativistic constituent quark model, for the first time without employing the impulse approximation. The calculated form factors are used to evaluate differential decay rates and polarization observables. We present results on a set of observables with and without long-distance contributions. and compare them with the results of other studies.
The vortex blob method as a second-grade non-Newtonian fluid
2022-03-19

We show that a certain class of vortex blob approximations for ideal hydrodynamics in two dimensions can be rigorously understood as solutions to the equations of second-grade non-Newtonian fluids with zero viscosity, and initial data in the space of Radon measures . The solutions of this regularized PDE, also known as the averaged Euler or Euler- equations, are geodesics on the volume preserving diffeomorphism group with respect to a new weak right invariant metric. We prove global existence of unique weak solutions (geodesics) for initial vorticity in such as point-vortex data, and show that the associated coadjoint orbit is preserved by the flow. Moreover, solutions of this particular vortex blob method converge to solutions of the Euler equations with bounded initial vorticity, provided that the initial data is approximated weakly in measure, and the total variation of the approximation also converges. In particular, this includes grid-based approximation schemes of the type that are usually used for vortex methods.
All Abelian Quotient C.I.-Singularities Admit Projective Crepant Resolutions in All Dimensions
2022-03-19

For Gorenstein quotient spaces , a direct generalization of the classical McKay correspondence in dimensions would primarily demand the existence of projective, crepant desingularizations. Since this turned out to be not always possible, Reid asked about special classes of such quotient spaces which would satisfy the above property. We prove that the underlying spaces of all Gorenstein abelian quotient singularities, which are embeddable as complete intersections of hypersurfaces in an affine space, have torus-equivariant projective crepant resolutions in all dimensions. We use techniques from toric and discrete geometry.
Applying System Combination to Base Noun Phrase Identification
2022-03-19

We use seven machine learning algorithms for one task: identifying base noun phrases. The results have been processed by different system combination methods and all of these outperformed the best individual result. We have applied the seven learners with the best combinator, a majority vote of the top five systems, to a standard data set and managed to improve the best published result for this data set.
Germs of local automorphisms of real-analytic CR structures and analytic dependence on $k$-jets
2022-03-19

The topic of the paper is the study of germs of local holomorphisms between and such that and for and generic real-analytic CR submanifolds of arbitrary codimensions. It is proved that for minimal and finitely nondegenerate, such germs depend analytically on their jets. As a corollary, an analytic structure on the set of all germs of this type is obtained.