A Matrix Model for AdS2

A matrix quantum mechanics with potential $V={q^2 \over r^2}$ and an SL(2,R) conformal symmetry is conjectured to be dual to two-dimensional type 0A string theory on AdS$_2$ with $q$ units of RR flux.Comment: 12 page

Novel Energy Drink Improves Mood and Raises Blood Pressure, but has No Effect on Cardiac QTc Interval or Rate-Pressure Product in Young Adult Gamers

Novel energy drink formulations have been introduced to the market that are purported to have nootropic effects – including improving mood. Despite their rapidly growing popularity, especially among video gamers, there is minimal evidence supporting their efficacy or establishing their cardiovascular safety profiles. PURPOSE: We conducted a randomized, double-blind, placebo-controlled, crossover trial to investigate the effects of acute consumption of a non-caloric, novel energy drink (NED) containing 200 mg caffeine, citicoline, tyrosine, B-vitamins, and carboxylic acids on mood and cardiovascular safety outcomes. We hypothesized that NED would improve mood without significant adverse cardiovascular effects when compared to placebo. METHODS: Forty-five healthy young adults who routinely play video games (37M, 8F; mean ± SD, age = 25 ± 6 y) each completed two experimental study visits in randomized order where they consumed either NED or a placebo matched for volume, calories, taste, appearance, and mouthfeel. Resting systolic and diastolic blood pressure (SBP and DBP) and an electrocardiogram (ECG) were obtained from each participant after a 10-min quiescent period prior to and 45 minutes after consumption of NED or placebo. Resting heart rate (RHR) and corrected QT interval length (QTc) were derived from the ECG. Rate-pressure product (RPP) was determined as the product of HR and SBP. Mood was assessed using the Profile of Mood States at post-consumption after BP and ECG assessments. Paired t-tests or signed ranked tests (for non- normally distributed data) were used to examine between-condition differences in mood states, whereas 2 (condition) × 2 (time) ANOVAs were used to examine SBP, DBP, QTc, and RPP. RESULTS: Change scores are presented as mean absolute change ± 95% confidence interval. Relative changes are provided for mood data. Acute NED consumption improved fatigue-inertia (-1.4 ± 1.0 a.u. [+36%]; p = 0.004), vigor-activity (+2.4 ± 1.2 a.u. [+33%]; p \u3c 0.001), and friendliness (+0.7 ± 0.7 a.u. [+7%]; p = 0.04), without adverse effects on tension-anxiety, confusion-bewilderment, or depression-dejection (all p ≥ 0.27). RHR decreased from pre- to post-beverage consumption, and this decrease was greater following NED than placebo consumption (-6.0 ± 2.8 vs. -2.6 ± 1.4 bpm, p = 0.017). SBP (+3.7 ± 2.0 vs. -0.4 ± 2.0 mmHg; p = 0.002) and DBP (+3.7 ± 1.7 vs. -0.04 ± 1.4 mmHg; p = 0.003) increased following NED vs. placebo; however, RPP decreased independent of condition (-386.0 ± 229.0; p = 0.03), and there was no effect of beverage consumption on QTc (p = 0.44). CONCLUSION: Acute NED consumption improved mood states related to vigor, fatigue, and friendliness without affecting tension-anxiety, depression, or confusion in young adult gamers. While NED consumption produced mild increases in SBP and DBP, there were no effects on either QTc or RPP. Thus, overall, NED consumption produces mood-enhancing effects without markedly influencing cardiovascular safety outcomes

Missing energy in black hole production and decay at the Large Hadron Collider

Black holes could be produced at the Large Hadron Collider in TeV-scale gravity scenarios. We discuss missing energy mechanisms in black hole production and decay in large extra-dimensional models. In particular, we examine how graviton emission into the bulk could give the black hole enough recoil to leave the brane. Such a perturbation would cause an abrupt termination in Hawking emission and result in large missing-energy signatures.Comment: addressed reviewer comments and updated reference

Tensor-scalar gravity and binary-pulsar experiments

Some recently discovered nonperturbative strong-field effects in tensor-scalar theories of gravitation are interpreted as a scalar analog of ferromagnetism: "spontaneous scalarization". This phenomenon leads to very significant deviations from general relativity in conditions involving strong gravitational fields, notably binary-pulsar experiments. Contrary to solar-system experiments, these deviations do not necessarily vanish when the weak-field scalar coupling tends to zero. We compute the scalar "form factors" measuring these deviations, and notably a parameter entering the pulsar timing observable gamma through scalar-field-induced variations of the inertia moment of the pulsar. An exploratory investigation of the confrontation between tensor-scalar theories and binary-pulsar experiments shows that nonperturbative scalar field effects are already very tightly constrained by published data on three binary-pulsar systems. We contrast the probing power of pulsar experiments with that of solar-system ones by plotting the regions they exclude in a generic two-dimensional plane of tensor-scalar theories.Comment: 35 pages, REVTeX 3.0, uses epsf.tex to include 9 Postscript figure

Signatures of black holes at the LHC

Signatures of black hole events at CERN's Large Hadron Collider are discussed. Event simulations are carried out with the Fortran Monte Carlo generator CATFISH. Inelasticity effects, exact field emissivities, color and charge conservation, corrections to semiclassical black hole evaporation, gravitational energy loss at formation and possibility of a black hole remnant are included in the analysis.Comment: 13 pages, 7 figure

Equations of Motion for Massive Spin 2 Field Coupled to Gravity

We investigate the problems of consistency and causality for the equations of motion describing massive spin two field in external gravitational and massless scalar dilaton fields in arbitrary spacetime dimension. From the field theoretical point of view we consider a general classical action with non-minimal couplings and find gravitational and dilaton background on which this action describes a theory consistent with the flat space limit. In the case of pure gravitational background all field components propagate causally. We show also that the massive spin two field can be consistently described in arbitrary background by means of the lagrangian representing an infinite series in the inverse mass. Within string theory we obtain equations of motion for the massive spin two field coupled to gravity from the requirement of quantum Weyl invariance of the corresponding two dimensional sigma-model. In the lowest order in $\alpha'$ we demonstrate that these effective equations of motion coincide with consistent equations derived in field theory.Comment: 27 pages, LaTeX file, journal versio

A parameter sensitivity methodology in the context of HIV delay equation models

A sensitivity methodology for nonlinear delay systems arising in one class of cellular HIV infection models is presented. Theoretical foundations for a typical sensitivity investigation and illustrative computations are given.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46951/1/285_2004_Article_299.pd

Is string theory a theory of quantum gravity?

Some problems in finding a complete quantum theory incorporating gravity are discussed. One is that of giving a consistent unitary description of high-energy scattering. Another is that of giving a consistent quantum description of cosmology, with appropriate observables. While string theory addresses some problems of quantum gravity, its ability to resolve these remains unclear. Answers may require new mechanisms and constructs, whether within string theory, or in another framework.Comment: Invited contribution for "Forty Years of String Theory: Reflecting on the Foundations," a special issue of Found. Phys., ed. by G 't Hooft, E. Verlinde, D. Dieks, S. de Haro. 32 pages, 5 figs., harvmac. v2: final version to appear in journal (small revisions

Non-standard embedding and five-branes in heterotic M-Theory

We construct vacua of M-theory on S^1/Z_2 associated with Calabi-Yau three-folds. These vacua are appropriate for compactification to N=1 supersymmetry theories in both four and five dimensions. We allow for general E_8 x E_8 gauge bundles and for the presence of five-branes. The five-branes span the four-dimensional uncompactified space and are wrapped on holomorphic curves in the Calabi-Yau space. Properties of these vacua, as well as of the resulting low-energy theories, are discussed. We find that the low-energy gauge group is enlarged by gauge fields that originate on the five-brane world-volumes. In addition, the five-branes increase the types of new E_8 x E_8 breaking patterns allowed by the non-standard embedding. Characteristic features of the low-energy theory, such as the threshold corrections to the gauge kinetic functions, are significantly modified due to the presence of the five-branes, as compared to the case of standard or non-standard embeddings without five-branes.Comment: 34 pages, Latex 2e with amsmath, typos removed, factors corrected, refs improve

Phenomenology of flavor-mediated supersymmetry breaking

The phenomenology of a new economical SUSY model that utilizes dynamical SUSY breaking and gauge-mediation (GM) for the generation of the sparticle spectrum and the hierarchy of fermion masses is discussed. Similarities between the communication of SUSY breaking through a messenger sector, and the generation of flavor using the Froggatt-Nielsen (FN) mechanism are exploited, leading to the identification of vector-like messenger fields with FN fields, and the messenger U(1) as a flavor symmetry. An immediate consequence is that the first and second generation scalars acquire flavor-dependent masses, but do not violate FCNC bounds since their mass scale, consistent with effective SUSY, is of order 10 TeV. We define and advocate a minimal flavor-mediated model (MFMM), recently introduced in the literature, that successfully accommodates the small flavor-breaking parameters of the standard model using order one couplings and ratios of flavon field vevs. The mediation of SUSY breaking occurs via two-loop log-enhanced GM contributions, as well as several one-loop and two-loop Yukawa-mediated contributions for which we provide analytical expressions. The MFMM is parameterized by a small set of masses and couplings, with values restricted by several model constraints and experimental data. The next-to-lightest sparticle (NLSP) always has a decay length that is larger than the scale of a detector, and is either the lightest stau or the lightest neutralino. Similar to ordinary GM models, the best collider search strategies are, respectively, inclusive production of at least one highly ionizing track, or events with many taus plus missing energy. In addition, D^0 - \bar{D}^0 mixing is also a generic low energy signal. Finally, the dynamical generation of the neutrino masses is briefly discussed.Comment: 54 pages, LaTeX, 8 figure