The weighted Grammar constraint

We introduce the WeightedGrammar constraint and propose propagation algorithms based on the CYK parser and the Earley parser. We show that the traces of these algorithms can be encoded as a weighted negation normal form (WNNF), a generalization of NNF that allows nodes to carry weights. Based on this connection, we prove the correctness and complexity of these algorithms. Specifically, these algorithms enforce domain consistency on the WeightedGrammar constraint in time O(n ³). Further, we propose that the WNNF constraint can be decomposed into a set of primitive arithmetic constraint without hindering propagation.     

Search for color singlet technicolor particles in p&pmacr; collisions at radicals = 1.8 TeV

We search for color singlet technirho and technipion production in p&pmacr; collisions at sqrt[s] = 1.8 TeV recorded with the Collider Detector at Fermilab. These exotic technimesons are present in a model of walking technicolor. The signatures studied are lepton plus two jets plus E(T) and multijet final states. No excess of events is seen in either final state. We set an upper limit on the technirho production cross section and exclude a region in the technipion mass versus technirho mass plane.     

Observation of diffractive b-quark production at the fermilab tevatron

We report a measurement of the fraction of b quarks produced diffractively in &pmacr;p collisions at sqrt[s] = 1.8 TeV. Diffraction is identified by the absence of particles in a forward pseudorapidity region. From events with an electron of transverse momentum 9.5相似文献   

Diffractive dijets with a leading antiproton in &pmacr;p collisions at sqrt

We report results from a study of events with a leading antiproton of beam momentum fraction 0.9057 GeV. Using the dijet events, we evaluate the diffractive structure function of the antiproton and compare it with expectations based on results obtained in diffractive deep inelastic scattering experiments at the DESY ep collider HERA.     

Examples of cell-like decompositions of the infinite-dimensional manifolds σ and Σ

Denote by σ the subspace of Hilbert space {(x_i)?l₂:x_i=0 for all but finitely many i}. Examples of cell-like decompositions of σ are constructed that have decomposition spaces that are not homeomorphic to σ. At one extreme is a cell-like decomposition G of σ produced using ghastly finite dimensional examples such that the decomposition space σ?G contains no embedded 2-cell but (σ?G)×$\text{R}$ is homeomorphic to σ. At the other extreme is a cell-like decomposition G of σ satisfying: (a) the nondegeneracy set N_G={g?G:g≠point} consists of countably many arcs (necessarily tame); (b) the nondegeneracy set N_G is a closed subset of the decomposition space σ?G; (c) each map f:B²→σ?G of a 2-cell into σ?G can be approximated arbitrarily closely by an embedding; (d) σ?G is not homeomorphic to σ but (σ?G)×$\text{R}$ is homeomorphic to σ. The fact that both conditions (a) and (b) can be satisfied (and have (d) hold) is directly attributable to σ’s incompleteness as a topological space.     

Characterizing Hilbert cube manifolds by their homological structure

A hierarchy of disjoint ?ech carriers properties is introduced; and each is shown to be characteristic of ANR's whose products with 2-cells are Hilbert cube manifolds.     

The kinetics of pyrolysis of barrelene[1]: A concerted process on the C8H8 energy surface

The static vessel pyrolysis of bicyclo[2.2.2]octa-2,5,7-triene (barrelene) has been studied between 483 and 523 K. The products were acetylene and benzene (in equal quantities) with no other detectable C₈H₈ isomer (down to less than 1% of total). The time dependence fitted first-order kinetics, and the data are consistent with a homogeneous unimolecular reaction close to, if not at, its high-pressure limit at 0.25 torr. The rate constant was fitted to the Arrhenius equation These Arrhenius parameters are shown to imply a concerted single-step process. Alternative mechanisms are discussed and a comparison is made with the retro-Diels—Alder reactions of other bicyclo[2.2.2]octa-olefin systems.