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 OO(10~TeV) Gravitino Mass in Supergravity

We study the solution to the Polonyi problem where the Polonyi field weighs as $O(10{\rm TeV})$ 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, $n_B/s \sim (10^{-10}-10^{-11})$ 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 $N>2$ 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' $\alpha$ to be interpreted as a varying $e$, $c$, $\hbar$, 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 $\alpha$ over cosmological times. We also show that unlike varying $e$ theories, VSL theories do not predict violations of the weak equivalence principle (WEP). Varying $e$ theories which explain astronomical inferences of varying $\alpha$ 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 $\alpha$ 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 $\Lambda_{QCD}$. Since $\Lambda_{QCD}$ 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