1,692 research outputs found
Introduction to transverse lattice gauge theory
I review a new treatment of an old idea for light-front quantization of
lattice gauge theories and give new results from some illustrative
calculations: [I] transverse lattice gauge theory; [II] pure glue; [III] heavy
sources and winding modes; [IV] an example -- large-N QCD in 2+1 dimensions.Comment: 4 invited lectures, 21 pages, 7 figures, uses aipproc.st
The Weingarten Model a la Polyakov
The Weingarten lattice gauge model of Nambu-Goto strings is generalised to
allow for fluctuations of an intrinsic worldsheet metric through a dynamical
quadrilation. The continuum limit is taken for matter, reproducing the
results of hermitian matrix models to all orders in the genus expansion. For
the compact case the vortices are Wilson lines, whose exclusion leads to
the theory of non-interacting fermions. As a by-product of the analysis one
finds the critical behaviour of SOS and vertex models coupled to 2D quantum
gravity.Comment: 16 pages (5 illustrations not included
Generalised Parton Distributions of the Pion on the Transverse Lattice
The quark generalised parton distributions of the pion are calculated from
lightcone wavefunctions in transverse lattice gauge theory at large N_c. The
pion effective size is found to decrease with increasing momentum transfer. An
analytic ansatz, consistent with finite boundstate lightcone energy conditions,
is given for the lightcone momentum dependence of the wavefunctions. This leads
to simple, universal predictions for the behaviour of the distributions near
the endpoints, complementing numerical DLCQ data.Comment: 9 pages, invited talk at Light-Cone 2004, Amsterdam, 16-20 August,
2004, to appear in proceedings; v2 resolves T-violation issu
Adjoint QCD2 and the Non-Abelian Schwinger Mechanism
Massless Majorana fermions in the adjoint representation of SU(N_c) are
expected to screen gauge interactions in 1+1 dimensions, analogous to a similar
Higgs phenomena known for 1+1-dimensional U(1) gauge theory with massless
fundamental fermions (Schwinger model). Using the light-cone formalism and
large-N_c limit, a non-abelian analogue of the Schwinger boson is shown to be
responsible for the screening between heavy test charges. This adjoint boson
does not exist simply as a physical state, but boundstates are built entirely
from this particle.Comment: 10 pages LaTeX, uses boxedeps.tex. Figures clarified no
Collinear QCD Models
The small momentum fraction x behaviour of quarks in mesons is analysed in
the 1+1-dimensional reduced model of large-N QCD by light-cone quantisation.Comment: 6 pages, LaTeX, uses boxedeps.tex (included). Invited talk at `New
Non-Perturbative Methods and Quantisation on the Light-Cone', Les Houches 24
Feb - 4 Mar 1997. (To appear in proceedings). Replaced version has a (sign)
typo corrected in very last sentenc
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
c>1 Non-Critical Strings and Large-N Matrix Field Theory
Motivated by a possible relativistic string description of hadrons we use a
discretised light-cone quantisation and Lanczos algorithm to investigate the
phase structure of phi^3 matrix field theory in the large N limit. In 1+1
dimensions we confirm the existence of Polyakov's non-critical string theory at
the boundary between parton-like and string-like phases, finding critical
exponents for longitudinal oscillations equal to or consistent with those given
by a mean field argument. The excitation spectrum is finite, possibly discrete.
We calculate light-cone structure functions and find evidence that the
probability Q(x) of a parton in the string carrying longitudinal momentum
fraction between x and x+dx has support on all 0<x<1, despite the average
number of partons being infinite.Comment: 9 pages LateX + 7 figures uuencode
Transverse Lattice
The transverse lattice approach to non-perturbative light-front hamiltonian
QCD is described. Preliminary results on the pi-rho system are presented, at
fixed DLCQ and Tamm-Dancoff cut-offs. A renormalised, approximately Lorentz
covariant light-front hamiltonian is found to leading order of the
colour-dielectric expansion, compatible with a massless pion. The pi
light-front wavefunction is compared with experiment. Exclusive processes agree
reasonably well, given the approximations, but inclusive processes, sensitive
to higher Fock state structure, still exhibit large cut-off artifacts.Comment: 11 pages, Invited talk at Xth International Light-Cone Meeting on
Non-Perturbative QCD and Hadron Phenomenology, Heidelberg 12-17 June 200
A (1+1)-Dimensional Reduced Model of Mesons
We propose an extension of 't Hooft's large- light-front QCD in two
dimensions to include helicity and physical gluon degrees of freedom, modelled
on a classical dimensional reduction of four dimensional QCD. A
non-perturbative renormalisation of the infinite set of coupled integral
equations describing boundstates is performed. These equations are then solved,
both analytically in a phase space wavefunction approximation and numerically
by discretising momenta, for (hybrid) meson masses and (polarized) parton
structure functions.Comment: LaTex 13 pages; 2 figures, uuencoded file (PostScript
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