Particle motion in the field of a five-dimensional charged black hole

In this paper, we have investigated the geodesics of neutral particles near a five-dimensional charged black hole using a comparative approach. The effective potential method is used to determine the location of the horizons and to study radial and circular trajectories. This also helps us to analyze the stability of radial and circular orbits. The radius of the innermost stable circular orbits have also been determined. Contrary to the case of massive particles for which, the circular orbits may have up to eight possible values of specific radius, we find that the photons will only have two distinct values for the specific radii of circular trajectories. Finally we have used the dynamical systems analysis to determine the critical points and the nature of the trajectories for the timelike and null geodesics.Comment: 15 pages, accepted for publication in Astrophysics and Space Scienc

M-Theory Moduli Space and Cosmology

We conduct a systematic search for a viable string/M-theory cosmology, focusing on cosmologies that include an era of slow-roll inflation, after which the moduli are stabilized and the Universe is in a state with an acceptably small cosmological constant. We observe that the duality relations between different cosmological backgrounds of string/M-theory moduli space are greatly simplified, and that this simplification leads to a truncated moduli space within which possible cosmological solutions lie. We review some known challenges to four dimensional models in the "outer", perturbative, region of moduli space, and use duality relations to extend them to models of all of the (compactified) perturbative string theories and 11D supergravity, including brane world models. We conclude that cosmologies restricted to the outer region are not viable, and that the most likely region of moduli space in which to find realistic cosmology is the "central", non-perturbative region, with coupling and compact volume both of order unity, in string units.Comment: 42 pages, 3 figure

Quintessential Maldacena-Maoz Cosmologies

Maldacena and Maoz have proposed a new approach to holographic cosmology based on Euclidean manifolds with disconnected boundaries. This approach appears, however, to be in conflict with the known geometric results [the Witten-Yau theorem and its extensions] on spaces with boundaries of non-negative scalar curvature. We show precisely how the Maldacena-Maoz approach evades these theorems. We also exhibit Maldacena-Maoz cosmologies with [cosmologically] more natural matter content, namely quintessence instead of Yang-Mills fields, thereby demonstrating that these cosmologies do not depend on a special choice of matter to split the Euclidean boundary. We conclude that if our Universe is fundamentally anti-de Sitter-like [with the current acceleration being only temporary], then this may force us to confront the holography of spaces with a connected bulk but a disconnected boundary.Comment: Much improved exposition, exponent in Cai-Galloway theorem fixed, axionic interpretation of scalar explained, JHEP version. 33 pages, 3 eps figure

Disappearing Dark Matter in Brane World Cosmology: New Limits on Noncompact Extra Dimensions

We explore cosmological implications of dark matter as massive particles trapped on a brane embedded in a Randall-Sundrum noncompact higher dimension $AdS_5$ space. It is an unavoidable consequence of this cosmology that massive particles are metastable and can disappear into the bulk dimension. Here, we show that a massive dark matter particle (e.g. the lightest supersymmetric particle) is likely to have the shortest lifetime for disappearing into the bulk. We examine cosmological constraints on this new paradigm and show that disappearing dark matter is consistent (at the 95% confidence level) with all cosmological constraints, i.e. present observations of Type Ia supernovae at the highest redshift, trends in the mass-to-light ratios of galaxy clusters with redshift, the fraction of X-ray emitting gas in rich clusters, and the spectrum of power fluctuations in the cosmic microwave background. A best $2 \sigma$ concordance region is identified corresponding to a mean lifetime for dark matter disappearance of $15 \le \Gamma^{-1} \le 80$ Gyr. The implication of these results for brane-world physics is discussed.Comment: 7 pages, 7 figures, new cosmological constraints added, accepted for publication in PR

Scalar brane backgrounds in higher order curvature gravity

We investigate maximally symmetric brane world solutions with a scalar field. Five-dimensional bulk gravity is described by a general lagrangian which yields field equations containing no higher than second order derivatives. This includes the Gauss-Bonnet combination for the graviton. Stability and gravitational properties of such solutions are considered, and we particularily emphasise the modifications induced by the higher order terms. In particular it is shown that higher curvature corrections to Einstein theory can give rise to instabilities in brane world solutions. A method for analytically obtaining the general solution for such actions is outlined. Genericaly, the requirement of a finite volume element together with the absence of a naked singularity in the bulk imposes fine-tuning of the brane tension. A model with a moduli scalar field is analysed in detail and we address questions of instability and non-singular self-tuning solutions. In particular, we discuss a case with a normalisable zero mode but infinite volume element.Comment: published versio

Measurement of open charm production in dd+Au collisions at sNN\sqrt{s_{NN}}=200 GeV

We present the first comprehensive measurement of $D^{0}, D^{+}, D^{*+}$ and their charge conjugate states at mid-rapidity in $d$+Au collisions at $\sqrt{s_{_{NN}}}$=200 GeV using the STAR TPC. The directly measured open charm multiplicity distribution covers a broad transverse momentum region of 0$<p_{T}<11$ GeV/$c$. The measured $dN/dy$ at mid-rapidity for $D^{0}$ is $0.0265\pm 0.0036 (stat.) \pm 0.0071 (syst.)$ and the measured $D^{*+}/D^{0}$ and $D^{+}/D^{0}$ ratios are approximately equal with a magnitude of $0.40\pm 0.09(stat.) \pm 0.13(syst.)$. The total $c\bar{c}$ cross section per nucleon-nucleon collision extracted from this study is $1.18 \pm 0.21(stat.) \pm 0.39(syst.)$mb. The direct measurement of open charm production is consistent with STAR single electron data. This cross section is higher than expectations from PYTHIA and other pQCD calculations. The measured $p_{T}$ distribution is harder than the pQCD prediction using the Peterson fragmentation function.Comment: Quark Matter 2004 Proceeding

Azimuthal anisotropy: the higher harmonics

We report the first observations of the fourth harmonic (v_4) in the azimuthal distribution of particles at RHIC. The measurement was done taking advantage of the large elliptic flow generated at RHIC. The integrated v_4 is about a factor of 10 smaller than v_2. For the sixth (v_6) and eighth (v_8) harmonics upper limits on the magnitudes are reported.Comment: 4 pages, 6 figures, contribution to the Quark Matter 2004 proceeding

Azimuthal anisotropy and correlations in p+p, d+Au and Au+Au collisions at 200 GeV

We present the first measurement of directed flow ($v_1$) at RHIC. $v_1$ is found to be consistent with zero at pseudorapidities $\eta$ from -1.2 to 1.2, then rises to the level of a couple of percent over the range $2.4 < |\eta| < 4$. The latter observation is similar to data from NA49 if the SPS rapidities are shifted by the difference in beam rapidity between RHIC and SPS. Back-to-back jets emitted out-of-plane are found to be suppressed more if compared to those emitted in-plane, which is consistent with {\it jet quenching}. Using the scalar product method, we systematically compared azimuthal correlations from p+p, d+Au and Au+Au collisions. Flow and non-flow from these three different collision systems are discussed.Comment: Quark Matter 2004 proceeding, 4 pages, 3 figure

An Integrated TCGA Pan-Cancer Clinical Data Resource to Drive High-Quality Survival Outcome Analytics

For a decade, The Cancer Genome Atlas (TCGA) program collected clinicopathologic annotation data along with multi-platform molecular profiles of more than 11,000 human tumors across 33 different cancer types. TCGA clinical data contain key features representing the democratized nature of the data collection process. To ensure proper use of this large clinical dataset associated with genomic features, we developed a standardized dataset named the TCGA Pan-Cancer Clinical Data Resource (TCGA-CDR), which includes four major clinical outcome endpoints. In addition to detailing major challenges and statistical limitations encountered during the effort of integrating the acquired clinical data, we present a summary that includes endpoint usage recommendations for each cancer type. These TCGA-CDR findings appear to be consistent with cancer genomics studies independent of the TCGA effort and provide opportunities for investigating cancer biology using clinical correlates at an unprecedented scale. Analysis of clinicopathologic annotations for over 11,000 cancer patients in the TCGA program leads to the generation of TCGA Clinical Data Resource, which provides recommendations of clinical outcome endpoint usage for 33 cancer types

Non-identical particle correlations in 130 and 200 AGeV collisions at STAR

STAR has performed a correlation analyses of pion-kaon and pion-proton pairs for sqrt(s_NN)=130 AGeV and sqrt(s_NN)=200 AGeV and kaon-proton, proton-Lambda and pion-Cascade pairs for AuAu collisions sqrt(s_NN)=200 AGeV. They show that average emission space-time points of pions, kaons and protons are not the same. These asymmetries are interpreted as a consequence of transverse radial expansion of the system; emission time differences explain only part of the asymmetry. Therefore our measurements independently confirm the existence of transverse radial flow. Furthermore, correlations of strange hyperons is investigated by performing proton-Lambda and pion-Cascade analyses, giving estimates of source size at high m_{T}. The strong interaction potential between (anti-)proton and lambda as well as kaon and proton is investigated.Comment: 5 pages, 3 figures, Quark Matter 04 proceedings, submitted to J. Phys. G: Nucl. Phy