8 research outputs found
A study of the quenched bc mass spectrum at beta=6.2
We present an analysis of the mass spectrum of heavy quarkonia with
non-degenerate quark masses. The heavier (bottom) valence quark is treated in a
non-relativistic fashion and the other (charm) is a relativistic Wilson-like
quark using the improved SW action. Such states provide and interesting probe
between the relativistic B meson states and the non-relativistic bottomonium
states.Comment: 4 pages LaTeX, 4 postscript figures. requires espcrc2.sty and
epsf.sty. To be published in the proceedings of Lattice 97, Edinburgh,
Scotlan
Spectroscopy from Lattice QCD
We present first results for spectroscopy using Lattice
Non-Relativistic QCD (NRQCD). For the NRQCD action the leading order
spin-dependent and next to leading order spin-independent interactions have
been included with tadpole-improved coefficients. We use multi-exponential fits
to multiple correlation functions to extract ground and excited states and
give accurate values for the state hyperfine splitting and the P state
() fine structure, including the effects of mixing.Comment: 12 pages uuencoded latex file + 1 postscript figur
The Primordial Perturbation Spectrum from Various Expanding and Contracting Phases
In this paper, focusing on the case of single scalar field, we discuss
various expanding and contracting phases generating primordial perturbations,
and study the relation between the primordial perturbation spectrum from these
phases and the parameter w of state equation in details. Furthermore, we offer
an interesting classification for the primordial perturbation spectrum from
various phases, which may have important implications for building an early
universe scenario embedded in possible high energy theories.Comment: 5 pages, 3 eps figure
Renormalization group and nonequilibrium action in stochastic field theory
We investigate the renormalization group approach to nonequilibrium field
theory. We show that it is possible to derive nontrivial renormalization group
flow from iterative coarse graining of a closed-time-path action. This
renormalization group is different from the usual in quantum field theory
textbooks, in that it describes nontrivial noise and dissipation. We work out a
specific example where the variation of the closed-time-path action leads to
the so-called Kardar-Parisi-Zhang equation, and show that the renormalization
group obtained by coarse graining this action, agrees with the dynamical
renormalization group derived by directly coarse graining the equations of
motion.Comment: 33 pages, 3 figures included in the text. Revised; one reference
adde
Cosmological Perturbations Through a General Relativistic Bounce
The ekpyrotic and cyclic universe scenarios have revived the idea that the
density perturbations apparent in today's universe could have been generated in
a `pre-singularity' epoch before the big bang. These scenarios provide explicit
mechanisms whereby a scale invariant spectrum of adiabatic perturbations may be
generated without the need for cosmic inflation, albeit in a phase preceding
the hot big bang singularity. A key question they face is whether there exists
a unique prescription for following perturbations through the bounce, an issue
which is not yet definitively settled. This goal of this paper is more modest,
namely to study a bouncing Universe model in which neither General Relativity
nor the Weak Energy Condition is violated. We show that a perturbation which is
pure growing mode before the bounce does not match to a pure decaying mode
perturbation after the bounce. Analytical estimates of when the comoving
curvature perturbation varies around the bounce are given. It is found that in
general it is necessary to evaluate the evolution of the perturbation through
the bounce in detail rather than using matching conditions.Comment: 15 pages, 6 figures. Added more details showing how and when the
comoving curvature perturbation varies on large scales during the bounc