Multipole moments in Kaluza-Klein theories

This paper contains discussion of the problem of motion of extended i.e. non point test bodies in multidimensional space. Extended bodies are described in terms of so called multipole moments. Using approximated form of equations of motion for extended bodies deviation from geodesic motion is derived. Results are applied to special form of space-time.Comment: 11 pages, AMS-TeX, few misprints corrected, to appear in Classical and Quantum Gravit

Green functions and dimensional reduction of quantum fields on product manifolds

We discuss Euclidean Green functions on product manifolds P=NxM. We show that if M is compact then the Euclidean field on P can be approximated by its zero mode which is a Euclidean field on N. We estimate the remainder of this approximation. We show that for large distances on N the remainder is small. If P=R^{D-1}xS^{beta}, where S^{beta} is a circle of radius beta, then the result reduces to the well-known approximation of the D dimensional finite temperature quantum field theory to D-1 dimensional one in the high temperature limit. Analytic continuation of Euclidean fields is discussed briefly.Comment: 17 page

Optical Activity From Extra Dimension

Optical activity, like Faraday effect, is a rotation of the plane of polarization of propagating light in a medium and can be attributed to different sources with distinct signatures. In this note we discuss the effect of optical activity {\it{in vacuum}} due to Kaluza-Klein scalar field $\phi$, in the presence of an external electro-magnetic field. The astrophysical implication of this effect is indicated. We also point out the possibility of observing the same in laboratory conditions.Comment: Four Page

Particle creation in the presence of a warped extra dimension

Particle creation in spacetimes with a warped extra dimension is studied. In particular, we investigate the dynamics of a conformally coupled, massless scalar field in a five dimensional warped geometry where the induced metric on the 3--branes is that of a spatially flat cosmological model. We look at situations where the scale of the extra dimension is assumed (i) to be time independent or (ii) to have specific functional forms for time dependence. The warp factor is chosen to be that of the Randall--Sundrum model. With particular choices for the functional form of the scale factor (and also the function characterising the time evolution of the extra dimension) we obtain the ${| \beta_k|}^2$, the particle number and energy densities after solving (wherever possible, analytically but, otherwise, numerically) the conformal scalar field equations. The behaviour of these quantities for the massless and massive Kaluza--Klein modes are examined. Our results show the effect of a warped extra dimension on particle creation and illustrate how the nature of particle production on the brane depends on the nature of warping, type of cosmological evolution as well as the temporal evolution of the extra dimension.Comment: 21 pages, 10 figures, minor corrections, new references added, version to appear in JCA

Detectability of Strange Matter in Heavy Ion Experiments

We discuss the properties of two distinct forms of hypothetical strange matter, small lumps of strange quark matter (strangelets) and of hyperon matter (metastable exotic multihypernuclear objects: MEMOs), with special emphasis on their relevance for present and future heavy ion experiments. The masses of small strangelets up to A = 40 are calculated using the MIT bag model with shell mode filling for various bag parameters. The strangelets are checked for possible strong and weak hadronic decays, also taking into account multiple hadron decays. It is found that strangelets which are stable against strong decay are most likely highly negative charged, contrary to previous findings. Strangelets can be stable against weak hadronic decay but their masses and charges are still rather high. This has serious impact on the present high sensitivity searches in heavy ion experiments at the AGS and CERN facilities. On the other hand, highly charged MEMOs are predicted on the basis of an extended relativistic mean-field model. Those objects could be detected in future experiments searching for short-lived, rare composites. It is demonstrated that future experiments can be sensitive to a much wider variety of strangelets.Comment: 26 pages, 5 figures, uses RevTeX and epsf.st

Non-perturbative dynamics of hot non-Abelian gauge fields: beyond leading log approximation

Many aspects of high-temperature gauge theories, such as the electroweak baryon number violation rate, color conductivity, and the hard gluon damping rate, have previously been understood only at leading logarithmic order (that is, neglecting effects suppressed only by an inverse logarithm of the gauge coupling). We discuss how to systematically go beyond leading logarithmic order in the analysis of physical quantities. Specifically, we extend to next-to-leading-log order (NLLO) the simple leading-log effective theory due to Bodeker that describes non-perturbative color physics in hot non-Abelian plasmas. A suitable scaling analysis is used to show that no new operators enter the effective theory at next-to-leading-log order. However, a NLLO calculation of the color conductivity is required, and we report the resulting value. Our NLLO result for the color conductivity can be trivially combined with previous numerical work by G. Moore to yield a NLLO result for the hot electroweak baryon number violation rate.Comment: 20 pages, 1 figur

Nonforward Parton Distributions

Applications of perturbative QCD to deeply virtual Compton scattering and hard exclusive electroproduction processes require a generalization of usual parton distributions for the case when long-distance information is accumulated in nonforward matrix elements of quark and gluon light-cone operators. We describe two types of nonperturbative functions parametrizing such matrix elements: double distributions F(x,y;t) and nonforward distribution functions F_\zeta (X;t), discuss their spectral properties, evolution equations which they satisfy, basic uses and general aspects of factorization for hard exclusive processes.Comment: Final version, to be published in Phys.Rev.

The Cosmological Constant Problem and Quintessence

I briefly review the cosmological constant problem and the issue of dark energy (or quintessence). Within the framework of quantum field theory, the vacuum expectation value of the energy momentum tensor formally diverges as $k^4$. A cutoff at the Planck or electroweak scale leads to a cosmological constant which is, respectively, $10^{123}$ or $10^{55}$ times larger than the observed value, \l/8\pi G \simeq 10^{-47} GeV$^4$. The absence of a fundamental symmetry which could set the value of \l to either zero or a very small value leads to {\em the cosmological constant problem}. Most cosmological scenario's favour a large time-dependent \l-term in the past (in order to generate inflation at $z \gg 10^{10}$), and a small \l-term today, to account for the current acceleration of the universe at z \lleq 1. Constraints arising from cosmological nucleosynthesis, CMB and structure formation constrain \l to be sub-dominant during most of the intermediate epoch $10^{10} < z < 1$. This leads to the {\em cosmic coincidence} conundrum which suggests that the acceleration of the universe is a recent phenomenon and that we live during a special epoch when the density in \l and in matter are almost equal. Time varying models of dark energy can, to a certain extent, ameliorate the fine tuning problem (faced by \l), but do not resolve the puzzle of cosmic coincidence. I briefly review tracker models of dark energy, as well as more recent brane inspired ideas and the issue of horizons in an accelerating universe. Model independent methods which reconstruct the cosmic equation of state from supernova observations are also assessed. Finally, a new diagnostic of dark energy -- `Statefinder', is discussed.Comment: Minor typo's corrected, references added and updated. 15 pages, 5 figures. Invited review at ``The Early Universe and Cosmological Observations: a Critical Review'', UCT, Cape Town, July 2001, to appear in "Classical and Quantum Gravity

O(αsv2)O(\alpha_s v^2) correction to pseudoscalar quarkonium decay to two photons

We investigate the $O(\alpha_s v^2)$ correction to the process of pseudoscalar quarkonium decay to two photons in nonrelativistic QCD (NRQCD) factorization framework. The short-distance coefficient associated with the relative-order $v^2$ NRQCD matrix element is determined to next-to-leading order in $\alpha_s$ through the perturbative matching procedure. Some technical subtleties encountered in calculating the {O(\alpha_s) QCD amplitude are thoroughly addressed.Comment: v2, 28 pages, 2 figures and 2 tables, matching the published version; typos corrected, references added, as well as a "Note added in the proof

Search for a W' boson decaying to a bottom quark and a top quark in pp collisions at sqrt(s) = 7 TeV

Results are presented from a search for a W' boson using a dataset corresponding to 5.0 inverse femtobarns of integrated luminosity collected during 2011 by the CMS experiment at the LHC in pp collisions at sqrt(s)=7 TeV. The W' boson is modeled as a heavy W boson, but different scenarios for the couplings to fermions are considered, involving both left-handed and right-handed chiral projections of the fermions, as well as an arbitrary mixture of the two. The search is performed in the decay channel W' to t b, leading to a final state signature with a single lepton (e, mu), missing transverse energy, and jets, at least one of which is tagged as a b-jet. A W' boson that couples to fermions with the same coupling constant as the W, but to the right-handed rather than left-handed chiral projections, is excluded for masses below 1.85 TeV at the 95% confidence level. For the first time using LHC data, constraints on the W' gauge coupling for a set of left- and right-handed coupling combinations have been placed. These results represent a significant improvement over previously published limits.Comment: Submitted to Physics Letters B. Replaced with version publishe