1,656 research outputs found
The Boundary Cosmological Constant in Stable 2D Quantum Gravity
We study further the r\^ole of the boundary operator \O_B for macroscopic
loop length in the stable definition of 2D quantum gravity provided by the
formulation. The KdV flows are supplemented by an additional
flow with respect to the boundary cosmological constant . We
numerically study these flows for the , and models, solving for
the string susceptibility in the presence of \O_B for arbitrary coupling
. The spectrum of the Hamiltonian of the loop quantum mechanics is
continuous and bounded from below by . For large positive , the
theory is dominated by the `universal' topological phase present only in
the formulation. For large negative , the
non--perturbative physics approaches that of the definition, although
there is no path to the unstable solutions of the -even models.Comment: (Plain Tex, 11pp, 4 figures available on request) SHEP 91/92-2
The design and development of a self-commutating stepper motor
The system discussed adopts a well established and space proven motor, the 'stepper-motor' and shows that with simple commutation techniques it can be operated as a brushless dc motor at high speeds
Light-Cone Quantization of the c=2 Matrix Model
We study the large limit of an interacting \td\ matrix field theory,
whose perturbative expansion generates the sum over planar random graphs
embedded in two dimensions. In the \lc\ quantization the theory possesses
closed string excitations which become free as . If the
longitudinal momenta are discretized, then the calculation of the free string
spectrum reduces to finite matrix diagonalization, the size of the matrix
growing as the cut-off is removed. Our numerical results suggest that, for a
critical coupling, the \lc\ string spectrum becomes continuous. This would
indicate the massless dynamics of the Liouville mode of \td\ gravity, which
would constitute a {\it third} dimension of the string theory.Comment: 12 pages, (3 diagrams now available as postscript files from authors,
1 ref added), PUPT-133
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
String Spectrum of 1+1-Dimensional Large N QCD with Adjoint Matter
We propose gauging matrix models of string theory to eliminate unwanted
non-singlet states. To this end we perform a discretised light-cone
quantisation of large N gauge theory in 1+1 dimensions, with scalar or
fermionic matter fields transforming in the adjoint representation of SU(N).
The entire spectrum consists of bosonic and fermionic closed-string
excitations, which are free as N tends to infinity. We analyze the general
features of such bound states as a function of the cut-off and the gauge
coupling, obtaining good convergence for the case of adjoint fermions. We
discuss possible extensions of the model and the search for new non-critical
string theories.Comment: 20 pages (7 figures available from authors as postscipt files),
PUPT-134
Colour-Dielectric Gauge Theory on a Transverse Lattice
We investigate in some detail consequences of the effective colour-dielectric
formulation of lattice gauge theory using the light-cone Hamiltonian formalism
with a transverse lattice. As a quantitative test of this approach, we have
performed extensive analytic and numerical calculations for 2+1-dimensional
pure gauge theory in the large N limit. Because of Eguchi-Kawai reduction, one
effectively studies a 1+1-dimensional gauge theory coupled to matter in the
adjoint representation. We study the structure of coupling constant space for
our effective potential by comparing with the physical results available from
conventional Euclidean lattice Monte Carlo simulations of this system. In
particular, we calculate and measure the scaling behaviour of the entire
low-lying glueball spectrum, glueball wavefunctions, string tension, asymptotic
density of states, and deconfining temperature. We employ a new hybrid
DLCQ/wavefunction basis in our calculations of the light-cone Hamiltonian
matrix elements, along with extrapolation in Tamm-Dancoff truncation,
significantly reducing numerical errors. Finally we discuss, in light of our
results, what further measurements and calculations could be made in order to
systematically remove lattice spacing dependence from our effective potential a
priori.Comment: 48 pages, Latex, uses macro boxedeps.tex, minor errors corrected in
revised versio
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
Transverse lattice calculation of the pion light-cone wavefunctions
We calculate the light-cone wavefunctions of the pion by solving the meson
boundstate problem in a coarse transverse lattice gauge theory using DLCQ. A
large-N_c approximation is made and the light-cone Hamiltonian expanded in
massive dynamical fields at fixed lattice spacing. In contrast to earlier
calculations, we include contributions from states containing many gluonic
link-fields between the quarks.The Hamiltonian is renormalised by a combination
of covariance conditions on boundstates and fitting the physical masses M_rho
and M_pi, decay constant f_pi, and the string tension sigma. Good covariance is
obtained for the lightest 0^{-+} state, which we identify with the pion. Many
observables can be deduced from its light-cone wavefunctions.After perturbative
evolution,the quark valence structure function is found to be consistent with
the experimental structure function deduced from Drell-Yan pi-nucleon data in
the valence region x > 0.5. In addition, the pion distribution amplitude is
consistent with the experimental distribution deduced from the pi gamma^* gamma
transition form factor and diffractive dissociation. A new observable we
calculate is the probability for quark helicity correlation. We find a 45%
probability that the valence-quark helicities are aligned in the pion.Comment: 27 pages, 9 figure
Construction of bosonic string theory on infinitely curved Anti-de Sitter space
Free scalar field theory in the sector with a large number of particles can
be interpreted as bosonic string theory on anti-de Sitter space of vanishing
radius. Different ways of writing the field theory Hamiltonian translate to
different ways of reparametrizing the world-sheet sigma coordinate. Adding a
mass term in the field theory corresponds to cutting off the warped AdS
direction, with cut-off inversely proportional to the mass. The string theory
has neither tachyon, nor critical dimension.Comment: 18 pages, latex, using revte
Urine Calcium But Not Plasma Calcium or Urine Hydroxyproline Is Increased by a Systemic Acidosis in the Dairy Cow
Eight non-lactating, pregnant Holstein-Friesian cows were allocated to two treatments and individually offered diets differing in dietary cation-anion difference. Decreasing the dietary cation-anion difference reduced the urine pH within hours of anionic salt supplementation. Plasma calcium concentration was unaffected by dietary cation-anion difference but urine calcium concentration was significantly increased within 10 days of including anionic salts in the diet. Faecal calcium concentration was significantly reduced, indicating increased calcium absorption. Dietary calcium concentration or dietary cationanion difference did not significantly affect urinary hydroxyproline
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