We study the Hamiltonian approach to Yang-Mills theory in Coulomb gauge in Rayleigh-Schrödinger perturbation theory. The static gluon and ghost propagator as well as the potential between static color sources are calculated to one-loop order. Furthermore, the one-loop $\beta$ function is calculated from both the ghost-gluon vertex and the static potential and found to agree with the result of covariant perturbation theory.

A particle produced in a hard collision can lose energy through bremsstrahlung. It has long been of interest to calculate the effect on bremsstrahlung if the particle is produced inside a finite-size QCD medium such as a quark-gluon plasma. For the case of very high-energy particles traveling through the background of a weakly coupled quark-gluon plasma, it is known how to reduce this problem to an equivalent problem in nonrelativistic two-dimensional quantum mechanics. Analytic solutions, however, have always resorted to further approximations. One is a harmonic oscillator approximation to the corresponding quantum mechanics problem, which is appropriate for sufficiently thick media. Another is to formally treat the particle as having only a single significant scattering from the plasma (known as the $N=1$ term of the opacity expansion), which is appropriate for sufficiently thin media. In a broad range of intermediate cases, these two very different approximations give surprisingly similar but slightly differing results if one works to leading logarithmic order in the particle energy, and there has been confusion about the range of validity of each approximation. In this paper, I sort out in detail the parametric range of validity of these two approximations at leading logarithmic order. For simplicity, I study the problem for small ${\alpha }_{\mathrm{s}}$ and large logarithms but ${\alpha }_{\mathrm{s}}\log \ll 1$.

We study the interior of a charged, nonrotating distorted black hole. We consider static and axisymmetric black holes, and focus on a special case when an electrically charged distorted solution is obtained by the Harrison-Ernst transformation from an uncharged one. We demonstrate that the Cauchy horizon of such a black hole remains regular, provided the distortion is regular at the event horizon. The shape and the inner geometry of both the outer and inner (Cauchy) horizons are studied. We demonstrate that there exists a duality between the properties of the horizons. Proper time of a free fall of a test particle moving in the interior of the distorted black hole along the symmetry axis is calculated. We also study the property of the curvature in the inner domain between the horizons. Simple relations between the 4D curvature invariants and the Gaussian curvature of the outer and inner horizon surfaces are found.

Previous theorems concerning Weyl type systems, including Majumdar-Papapetrou systems, are generalized in two ways, namely, we take these theorems into $d$ spacetime dimensions ($d\ge 4$), and we also consider the very interesting Weyl-Guilfoyle systems, i.e., general relativistic charged fluids with nonzero pressure. In particular within the Newton-Coulomb theory of charged gravitating fluids, a theorem by Bonnor (1980) in three-dimensional space is generalized to arbitrary $(d-1)>3$ space dimensions. Then, we prove a new theorem for charged gravitating fluid systems in which we find the condition that the charge density and the matter density should obey. Within general relativity coupled to charged dust fluids, a theorem by De and Raychaudhuri (1968) in four-dimensional spacetime is rendered into arbitrary $d>4$ dimensions. Then a theorem, new in $d=4$ and $d>4$ dimensions, for Weyl-Guilfoyle systems, is stated and proved, in which we find the condition that the charge density, the matter density, the pressure, and the electromagnetic energy density should obey. This theorem comprises, in particular cases, a theorem by Gautreau and Hoffman (1973) and results in four dimensions by Guilfoyle (1999). Upon connection of an interior charged solution to an exterior Tangherlini solution (i.e., a Reissner-Nordström solution in $d$ dimensions), one is able to give a general definition for gravitational mass for this kind of relativistic systems and find a mass relation with several quantities of the interior solution. It is also shown that for sources of finite extent the mass is identical to the Tolman mass.

Gravitational waves from coalescing compact binaries are one of the most promising sources for detectors such as LIGO, Virgo, and GEO600. If the components of the binary possess significant angular momentum (spin), as is likely to be the case if one component is a black hole, spin-induced precession of a binary’s orbital plane causes modulation of the gravitational-wave amplitude and phase. If the templates used in a matched-filter search do not accurately model these effects then the sensitivity, and hence the detection rate, will be reduced. We investigate the ability of several search pipelines to detect gravitational waves from compact binaries with spin. We use the post-Newtonian approximation to model the inspiral phase of the signal and construct two new template banks using the phenomenological waveforms of Buonanno, Chen, and Vallisneri [A. Buonanno, Y. Chen, and M. Vallisneri, Phys. Rev. D 67, 104025 (2003)]. We compare the performance of these template banks to that of banks constructed using the stationary phase approximation to the nonspinning post-Newtonian inspiral waveform currently used by LIGO and Virgo in the search for compact binary coalescence. We find that, at the same false alarm rate, a search pipeline using phenomenological templates is no more effective than a pipeline which uses nonspinning templates. We recommend the continued use of the nonspinning stationary phase template bank until the false alarm rate associated with templates which include spin effects can be substantially reduced.

Approximate solutions to the Einstein field equations are valuable tools to investigate gravitational phenomena. An important aspect of any approximation is to investigate and quantify its regime of validity. We present a study that evaluates the effects that approximate puncture initial data, based on skeleton solutions to the Einstein constraints as proposed by [G. Faye, P. Jaranowski, and G. Schäfer, Phys. Rev. D 69, 124029 (2004).], have on numerical evolutions. Using data analysis tools, we assess the effectiveness of these constraint-violating initial data for both initial and advanced LIGO and show that the matches of waveforms from skeleton data with the corresponding waveforms from constraint-satisfying initial data are $\gtrsim 0.97$ when the total mass of the binary is $\gtrsim 40{\mathrm{M}}_{\odot }$. In addition, we demonstrate that the differences between the skeleton and the constraint-satisfying initial data evolutions, and thus waveforms, are due to negative Hamiltonian constraint violations present in the skeleton initial data located in the vicinity of the punctures. During the evolution, the skeleton data develops both Hamiltonian and momentum constraint violations that decay with time, with the binary system relaxing to a constraint-satisfying solution with black holes of smaller mass and thus different dynamics.

We present new constraints on cosmic variations of Newton’s gravitational constant by making use of the latest CMB data from WMAP, BOOMERANG, CBI and ACBAR experiments and independent constraints coming from big bang nucleosynthesis. We found that current CMB data provide constraints at the $\sim 10\%$ level, that can be improved to $\sim 3\%$ by including big bang nucleosynthesis data. We show that future data expected from the Planck satellite could constrain $G$ at the $\sim 1.5\%$ level while an ultimate, cosmic variance limited, CMB experiment could reach a precision of about 0.4%, competitive with current laboratory measurements.

We present a Bayesian sampling algorithm called adaptive importance sampling or population Monte Carlo (PMC), whose computational workload is easily parallelizable and thus has the potential to considerably reduce the wall-clock time required for sampling, along with providing other benefits. To assess the performance of the approach for cosmological problems, we use simulated and actual data consisting of CMB anisotropies, supernovae of type Ia, and weak cosmological lensing, and provide a comparison of results to those obtained using state-of-the-art Markov chain Monte Carlo (MCMC). For both types of data sets, we find comparable parameter estimates for PMC and MCMC, with the advantage of a significantly lower wall-clock time for PMC. In the case of WMAP5 data, for example, the wall-clock time scale reduces from days for MCMC to hours using PMC on a cluster of processors. Other benefits of the PMC approach, along with potential difficulties in using the approach, are analyzed and discussed.

We provide conservative bounds on the dark matter cross section and lifetime from final state radiation produced by annihilation or decay into charged leptons, either directly or via an intermediate particle $\varphi$. Our analysis utilizes the experimental gamma-ray flux upper limits from four Milky Way dwarf satellites: HESS observations of Sagittarius and VERITAS observations of Draco, Ursa Minor, and Willman 1. Using 90% confidence level lower limits on the integrals over the dark matter distributions, we find that these constraints are largely unable to rule out dark matter annihilations or decays as an explanation of the PAMELA and ATIC/PPB-BETS excesses. However, if there is an additional Sommerfeld enhancement in dwarfs, which have a velocity dispersion $\sim 10$ to 20 times lower than that of the local Galactic halo, then the cross sections for dark matter annihilating through $\varphi$’s required to explain the excesses are very close to the cross-section upper bounds from Willman 1. Dark matter annihilation directly into $\tau$’s is also marginally ruled out by Willman 1 as an explanation of the excesses, and the required cross section is only a factor of a few below the upper bound from Draco. Finally, we make predictions for the gamma-ray flux expected from the dwarf galaxy Segue 1 for the Fermi Gamma-ray Space Telescope. We find that for a sizeable fraction of the parameter space in which dark matter annihilation into charged leptons explains the PAMELA excess, Fermi has good prospects for detecting a gamma-ray signal from Segue 1 after 1 yr of observation.

It has been recently shown that the presence of a vector field over cosmological scales could explain the observed accelerated expansion of the Universe without introducing either new scales or unnatural initial conditions in the early Universe, thus avoiding the coincidence problem. Here, we present a detailed analysis of the constraints imposed by supernova type Ia (SNIa), cosmic microwave background (CMB), and baryon acoustic oscillation (BAO) data on the vector dark energy model with general spatial curvature. We find that contrary to standard cosmology, CMB data exclude a flat universe for this model and, in fact, predict a closed geometry for the spatial sections. We see that CMB and SNIa Gold data are perfectly compatible at the 1-sigma level, however the SNIa Union data set exhibits a 3-sigma tension with CMB. The same level of tension is also found between SNIa and BAO measurements.

Under a longitudinal rescaling of coordinates $x^{0,3}\to \lambda x^{0,3}$, $\lambda \ll 1$, the classical QCD action simplifies dramatically. This is the high-energy limit, as $\lambda \sim s^{-1/2}$, where $s$ is the center-of-mass energy squared of a hadronic collision. We find the quantum corrections to the rescaled action at one loop, in particular, finding the anomalous powers of $\lambda$ in this action, with $\lambda <1$. The method is an integration over high-momentum components of the gauge field. This is a Wilsonian renormalization procedure, and counterterms are needed to make the sharp-momentum cutoff gauge invariant. Our result for the quantum action is found, assuming $|\ln \lambda |\ll 1$, which is essential for the validity of perturbation theory. If $\lambda$ is sufficiently small (so that $|\ln \lambda |\gg 1$), then the perturbative renormalization group breaks down. This is due to uncontrollable fluctuations of the longitudinal chromomagnetic field.

The Large Hadron Collider promises to discover new physics beyond the standard model. An exciting possibility is the formation of string resonances at the TeV scale. In this article, we show how string resonances may be detected at the LHC in the $pp\to \gamma +\mathrm{\text{jet}}$ channel. Our study is based on event-shape variables, missing energy and momentum, maximum transverse momentum of photons and dijet invariant mass. These observables provide interesting signatures which enable us to discriminate string events from the standard model background.

The connection between the neutrinoless double beta [$(\beta \beta {)}_{0\nu }$] decay effective Majorana mass $|M_{ee}|$, and the branching ratios of the decays $H^{\pm \pm }\to l^{\pm }{l}^{\prime \pm }$, $l$, $l^{\prime }=e$, $\mu$, of the doubly charged Higgs boson $H^{\pm \pm }$ is analyzed within the Higgs triplet model of neutrino mass generation. We work in the version of the model with explicit breaking of the total lepton charge conservation, in which $H^{\pm \pm }\to l^{\pm }{l}^{\prime \pm }$, $l$, $l^{\prime }=e$, $\mu$, $\tau$ are the dominant decay modes of $H^{\pm \pm }$. It is assumed also that $H^{\pm \pm }$ are relatively light so that they can be produced at the CERN LHC and the branching ratios of interest measured. Taking into account the current and prospective uncertainties in the values of the neutrino mixing parameters most relevant for the problem studied—the atmospheric neutrino mixing angle ${\theta }_{23}$ and the CHOOZ angle ${\theta }_{13}$, and allowing the lightest neutrino mass and the $CP$ violating Dirac and Majorana phases to vary in the intervals [0, 0.3 eV] and $[0,2\pi ]$, respectively, we derive the regions of values of $\mathrm{BR}(H^{\pm \pm }\to e^{\pm }{e}^{\pm })$ and $\mathrm{BR}(H^{\pm \pm }\to e^{\pm }{\mu }^{\pm })$ for which $|M_{ee}|\ge 0.05\mathrm{eV}$, or $|M_{ee}|<0.05\mathrm{eV}$. This is done for the normal mass ordering case, the inverted mass ordering case, and the case when the ordering has not been determined. The analysis is performed both without using possible additional data on $\mathrm{BR}(H^{\pm \pm }\to {\mu }^{\pm }{\mu }^{\pm })$, as well as using prospective data on these branching ratios. In the latter case, results for several values of $\mathrm{BR}(H^{\pm \pm }\to {\mu }^{\pm }{\mu }^{\pm })$ are presented.

We study QCD thermodynamics in the presence of two independent imaginary chemical potentials coupled to two degenerate flavors of staggered quarks. Analytic continuation is used to determine nonlinear susceptibilities, to test the hadron resonance gas (HRG) model below the zero density critical temperature, $T_c$, and to determine the average phase factor of the fermion determinant. Deviations from HRG predictions, of the order of a few percent, are clearly visible for temperatures $T>0.95T_c$. The determination of nonlinear susceptibilities, using different interpolating functions for analytic continuation, gives consistent results and in agreement with Taylor expansion computations, apart from some systematic effects at or right above $T_c$. Results for the average phase factor are compared with the predictions of chiral perturbation theory; below $T_c$ we are able to distinguish the contribution of different hadron states, which is positive (i.e. tends to mitigate the sign problem) in the case of baryons.

We compute the longitudinal proton structure function $F_L$ from the $k_T$ factorization scheme, using the unified DGLAP/BFKL resummation approach at small $x$ for the unintegrated gluon density. The differences between the $k_T$ factorization, collinear factorization, and dipole approaches are analyzed and discussed. The comparisons with the DESY collider HERA data are made and predictions for the proposed large hadron-electron collider are also provided.

In the framework of the $k_T$-factorization approach, we study the production of Higgs bosons associated with a heavy (beauty or top) quark pair at the CERN LHC collider conditions. Our consideration is based mainly on the off-shell gluon-gluon fusion subprocess $g^{*}{g}^{*}\to Q\overline{Q}H$. The corresponding matrix element squared has been calculated for the first time. We investigate the total and differential cross sections of $b\overline{b}H$ and $t\overline{t}H$ production taking into account also the non-negligible contribution from the $q\overline{q}\to Q\overline{Q}H$ mechanism. In the numerical calculations we use the unintegrated gluon distributions obtained from the Ciafaloni-Catani-Fiorani-Marchesini evolution equation. Our results are compared with the leading predictions of the collinear factorization of QCD.

We consider possible indications of very-short-baseline (VSBL) electron neutrino disappearance into sterile neutrinos in MiniBooNE neutrino data and Gallium radioactive source experiments. We discuss the compatibility of such a disappearance with reactor and MiniBooNE antineutrino data. We find a tension between neutrino and antineutrino data which could be due to: (1) statistical fluctuations; (2) underestimate of systematic uncertainties; (3) exclusion of our hypothesis of very-short-baseline ${\nu }_e$ disappearance; (4) a violation of $CPT$ symmetry. Considering the first possibility, we present the results of a combined fit of all data, which indicate that $P_{{\nu }_e\to {\nu }_e}<1$ with 97.04% CL. We consider also the possibility of $CPT$ violation, which leads to the best-fit value $A_{ee}^{CPT,\mathrm{bf}}=-0.17$ for the asymmetry of the ${\nu }_e$ and ${\overline{\nu }}_e$ survival probabilities and $A_{ee}^{CPT}<0$ at 99.71% CL.

Results are reported on the measurement of the atmospheric neutrino-induced muon flux at a depth of 2 kilometers below the Earth’s surface from 1229 days of operation of the Sudbury Neutrino Observatory (SNO). By measuring the flux of through-going muons as a function of zenith angle, the SNO experiment can distinguish between the oscillated and unoscillated portion of the neutrino flux. A total of 514 muonlike events are measured between $-1\le \cos {\theta }_{\mathrm{zenith}}\le 0.4$ in a total exposure of $2.30\times {10}^{14}{\mathrm{cm}}^2\mathrm{s}$. The measured flux normalization is $1.22\pm 0.09$ times the Bartol three-dimensional flux prediction. This is the first measurement of the neutrino-induced flux where neutrino oscillations are minimized. The zenith distribution is consistent with previously measured atmospheric neutrino oscillation parameters. The cosmic ray muon flux at SNO with zenith angle $\cos {\theta }_{\mathrm{zenith}}>0.4$ is measured to be $(3.31\pm 0.01(\mathrm{stat})\pm 0.09(\mathrm{sys}))\times {10}^{-10}\mu /\mathrm{s}/{\mathrm{cm}}^2$.