124 research outputs found
A Class of String Backgrounds as a Semiclassical Limit of WZW Models
A class of string backgrounds associated with non semi-simple groups is
obtained as a special large level limit of ordinary WZW models. The models have
an integer Virasoro central charge and they include the background recently
studied by Nappi and Witten.Comment: 9 page
Prevalence of gambling disorder among prisoners: a systematic review
This article presents the first systematic review of studies on the prevalence of gambling disorder among prisoners across international jurisdictions. Only original studies that were published in English and employed reliable and valid screening tools are included in this analysis. The review finds that rates of problem or pathological gambling in prison populations are highly variable, ranging from 5.9% to 73% of male and female inmates surveyed. Nevertheless, recorded rates of problem and pathological gambling among inmates are consistently and significantly higher than rates of problem and pathological gambling recorded among the general population. The review indicates that the institution of problem gambling treatment programmes in carceral settings is necessary, to aid community re-entry and reduce the likelihood of re-offending. Moreover, it is suggested that the screening of inmates should become standard practice across penal institutions and other criminal justice organisations, with a view to better addressing the needs of offenders
On the Solution to the Polonyi Problem with (10~TeV) Gravitino Mass in Supergravity
We study the solution to the Polonyi problem where the Polonyi field weighs
as and decays just before the primordial nucleosynthesis. It
is shown that in spite of a large entropy production by the Polonyi field
decay, one can naturally explain the present value of the baryon-to-entropy
ratio, if the Affleck-Dine mechanism for
baryogenesis works. It is pointed out, however, that there is another
cosmological problem related to the abundance of the lightest superparticles
produced by the Polonyi decay
Moduli Inflation from Dynamical Supersymmetry Breaking
Moduli fields, which parameterize perturbative flat directions of the
potential in supersymmetric theories, are natural candidates to act as
inflatons. An inflationary potential on moduli space can result if the scale of
dynamical SUSY breaking in some sector of the theory is determined by a moduli
dependent coupling. The magnitude of density fluctuations generated during
inflation then depends on the scale of SUSY breaking in this sector. This can
naturally be hierarchically smaller than the Planck scale in a dynamical model,
giving small fluctuations without any fine tuning of parameters. It is also
natural for SUSY to be restored at the minimum of the moduli potential, and to
leave the universe with zero cosmological constant after inflation. Acceptable
reheating can also be achieved in this scenario.Comment: 14 pages, latex, improved discussion of reheating for composite
inflaton
Solutions of Extended Supersymmetric Matrix Models for Arbitrary Gauge Groups
Energy eigenstates for N=2 supersymmetric gauged quantum mechanics are found
for the gauges groups SU(n) and U(n). The analysis is aided by the existence of
an infinite number of conserved operators. The spectum is continuous.
Perturbative eigenstates for are also presented, a case which is relevant
for the conjectured description of M theory in the infinite momentum frame.Comment: 10 pages, LATEX, no figure
Introduction to D-branes
D-branes are string theory solitons defined by boundary conditions on open
strings that end on them. They play an important role in the non-perturbative
dynamics of string theory and have found a wide range of applications. These
lectures give a basic introduction to D-branes and their dynamics.Comment: 13 pages, 4 figures, Latex, espcrc2.sty. Lectures presented at the
33rd Karpacz Winter School of Theoretical Physics, Karpacz, Poland, 13-22
February 199
Is it e or is it c? Experimental Tests of Varying Alpha
Is the recent evidence for a time-varying fine structure 'constant'
to be interpreted as a varying , , , or a combination thereof? We
consider the simplest varying electric charge and varying speed of light
theories (VSL) and prove that for the same type of dark matter they predict
opposite senses of variation in over cosmological times. We also show
that unlike varying theories, VSL theories do not predict violations of the
weak equivalence principle (WEP). Varying theories which explain
astronomical inferences of varying predict WEP violations only an
order of magnitude smaller than existing E\"otv\"os experiment limits but could
be decisively tested by STEP. We finally exhibit a set of atomic-clock and
related experiments for which {\it all} (hyperbolic) varying theories
predict non-null results. They provide independent tests of the recent
astronomical evidence
Unusual Features of Varying Speed of Light Cosmologies
We contrast features of simple varying speed of light (VSL) cosmologies with
inflationary universe models. We present new features of VSL cosmologies and
show that they face problems explaining the cosmological isotropy problem. We
also find that if c falls fast enough to solve the flatness and horizon
problems then the quantum wavelengths of massive particle states and the radii
of primordial black holes can grow to exceed the scale of the particle horizon.
This may provide VSL cosmologies with a self-reproduction property. The
constraint of entropy increase is also discussed. The new problems described in
the this letter provide a set of bench tests for more sophisticated VSL
theories to pass.Comment: expanded version, 12 page
Implications of Gauge Unification for Time Variation of the Fine Structure Constant
Unification of the gauge couplings would imply that time variations of the
fine structure constant are accompanied by calculable and very significant time
variations in the QCD scale parameter . Since is
the dominant factor in setting the hadron masses, estimates made by simple
variations of the fine structure constant may not provide meaningful limits.
There may also be related variations in Yukawa couplings and the electroweak
scale. Implications for the 21 cm hyperfine transition, big bang
nucleosynthesis, and the triple alpha process are discussed. We find that the
first of these already provides strong constraints on the underlying theory. It
is emphasized more generally that time (and space) variations of fundamental
couplings and their correlations may be a significant probe of
ultra-high-energy physics.Comment: 13 pages, uses JHEP.cl
Astrophysical and cosmological considerations on a string dilaton of a least coupling
String-loop effects may generate very weak matter couplings for a (massless)
dilaton. We examine limits on the shift of such a dilaton toward its present
equilibrium value from big-bang nucleosynthesis and the binary pulsar. On the
other hand, the approach of the dilaton toward its present value can be
realized in the early universe in a quick and efficient way if an inflationary
period is present. We comment briefly on some implications.Comment: Revised version to appear in Astropart.Phys., numerical correction of
the binary pulsar constraint. 18 pages, late
- …