1,850 research outputs found
A Study of Heavy-Light Mesons on the Transverse Lattice
We present results from a study of meson spectra and structure in the limit
where one quark is infinitely heavy. The calculations, based on the framework
of light-front QCD formulated on a transverse lattice, are the first
non-perturbative studies of B-mesons in light-front QCD. We calculate the
Isgur-Wise form factor, light-cone distribution amplitude, the heavy-quark
parton distribution function and the leptonic decay constant of B-mesons.Comment: 5 pages, 3 figures, Revtex, corrected typos, added references,
included moment
The Influence of Higher Fock States in Light-Cone Gauge Theories
In the light-cone Fock state expansion of gauge theories, the influence of
non-valence states may be significant in precision non-perturbative
calculations. In two-dimensional gauge theories, it is shown how these states
modify the behaviour of the light-cone wavefunction in significant ways
relative to endemic choices of variational ansatz. Similar effects in
four-dimensional gauge theories are briefly discussed.Comment: 4 pages, REVTE
The spectrum of states with one current acting on the adjoint vacuum of massless QCD2
We consider a ``one current'' state, which is obtained by the application of
a color current on the ``adjoint'' vacuum. This is done in , with the
underlying quarks in the fundamental representation. The quarks are taken to be
massless, in which case the theory on the light-front can be ``currentized'',
namely, formulated in terms of currents only. The adjoint vacuum is shown to be
the application of a current derivative, at zero momentum, on the singlet
vacuum. We apply the operator on these states and find that in
general they are not eigenstates of apart from the large limit.
Problems with infra-red regularizations are pointed out. We discuss the
fermionic structure of these states.Comment: 18 pages, no figures. v2: minor corrections. v3: added some
clarifications and remarks, mainly on the contribution of zero modes. Typos
corrected, references added. To appear in Nuclear Physics
CA2 Pyramidal Layer
This report contains a gene expression summary of the CA2 pyramidal cell layer (CA2sp), derived from the Allen Brain Atlas (ABA) in situ hybridization mouse data set. The structure's location and morphological characteristics in the mouse brain are described using the Nissl data found in the Allen Reference Atlas. Using an established algorithm, the expression values of the CA2sp were compared to the values of the macro/parent-structure, in this case the pyramidal layer of Ammon’s Horn, for the purpose of extracting regionally selective gene expression data. The genes with the highest ranking selectivity ratios were manually curated and verified. 50 genes were then selected and compiled for expression characterization. The experimental data for each gene may be accessed via the links provided; additional data in the sagittal plane may also be accessed using the ABA. Correlations between gene expression in the CA2sp and the rest of the brain, across all genes in the coronal dataset (~4300 genes), were derived computationally. A gene ontology table (derived from DAVID Bioinformatics Resources 2007) is also included, highlighting possible functions of the 50 genes selected for this report
Facial Motor Nucleus
This report contains a summary of expression patterns for genes that are enriched in the facial motor nucleus (VII) of the medulla. All data is derived from the Allen Brain Atlas (ABA) in situ hybridization mouse project. The structure's location and morphological characteristics in the mouse brain are described using the Nissl data found in the Allen Reference Atlas. Using an established algorithm, the expression values of the facial motor nucleus were compared to the values of its larger parent structure, in this case the medulla, for the purpose of extracting regionally selective gene expression data. The highest ranking genes were manually curated and verified. 50 genes were then selected and compiled for expression analysis. The experimental data for each gene may be accessed via the links provided; additional data in the sagittal plane may also be accessed using the ABA. Correlations between gene expression in the facial motor nucleus and the rest of the brain, across all genes in the coronal dataset (~4300 genes), were derived computationally. A gene ontology table (derived from DAVID Bioinformatics Resources 2007) is also included, highlighting possible functions of the 50 genes selected for this report
The spectrum of multi-flavor QCD_2 and the non-Abelian Schwinger equation
Massless is dominated by classical configurations in the large
limit. We use this observation to study the theory by finding solutions to
equations of motion, which are the non-Abelian generalization of the Schwinger
equation. We find that the spectrum consists of massive mesons with which correspond to Abelian solutions. We generalize previously
discovered non-Abelian solutions and discuss their interpretation. We prove a
no-go theorem ruling out the existence of soliton solutions. Thus the
semi-classical approximation shows no baryons in the case of massless quarks, a
result derived before in the strong-coupling limit only.Comment: 17 pages, Latex. 1 figur
Transverse Lattice Approach to Light-Front Hamiltonian QCD
We describe a non-perturbative procedure for solving from first principles
the light-front Hamiltonian problem of SU(N) pure gauge theory in D spacetime
dimensions (D>2), based on enforcing Lorentz covariance of observables. A
transverse lattice regulator and colour-dielectric link fields are employed,
together with an associated effective potential. We argue that the light-front
vacuum is necessarily trivial for large enough lattice spacing, and clarify why
this leads to an Eguchi-Kawai dimensional reduction of observables to
1+1-dimensions in the infinite N limit. The procedure is then tested by
explicit calculations for 2+1-dimensional SU(infinity) gauge theory, within a
first approximation to the lattice effective potential. We identify a scaling
trajectory which produces Lorentz covariant behaviour for the lightest
glueballs. The predicted masses, in units of the measured string tension, are
in agreement with recent results from conventional Euclidean lattice
simulations. In addition, we obtain the potential between heavy sources and the
structure of the glueballs from their light-front wavefunctions. Finally, we
briefly discuss the extension of these calculations to 3+1-dimensions.Comment: 55 pages, uses macro boxedeps.tex, minor corrections in revised
versio
Dentate Gyrus
This report contains a gene expression summary of the dentate gyrus (DG), derived from the Allen Brain Atlas (ABA) _in situ_ hybridization mouse data set. The structure's location and morphological characteristics in the mouse brain are described using the Nissl data found in the Allen Reference Atlas. Using an established algorithm, the expression values of the dentate gyrus were compared to the values of the macro/parent-structure, in this case the hippocampal region, for the purpose of extracting regionally selective gene expression data. The genes with the highest ranking selectivity ratios were manually curated and verified. 50 genes were then selected and compiled for expression characterization. The experimental data for each gene may be accessed via the links provided; additional data in the sagittal plane may also be accessed using the ABA. Correlations between gene expression in the dentate gyrus and the rest of the brain, across all genes in the coronal dataset (~4300 genes), were derived computationally. A gene ontology table (derived from DAVID Bioinformatics Resources 2007) is also included, highlighting possible functions of the 50 genes selected for this report
Glueball calculations in large-N_c gauge theory
We use the light-front Hamiltonian of transverse lattice gauge theory to
compute from first principles the glueball spectrum and light-front
wavefunctions in the leading order of the 1/N_c colour expansion. We find
0^{++}, 2^{++}, and 1^{+-} glueballs having masses consistent with N_c=3 data
available from Euclidean lattice path integral methods. The wavefunctions
exhibit a light-front constituent gluon structure.Comment: 4 pages, 2 figures, uses macro boxedeps.tex, minor corrections in
revised versio
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