We study the nonperturbative production of gluon pairs from a constant SU(3) chromo-electric background field via the Schwinger mechanism. We fix the covariant background gauge with an arbitrary gauge parameter $\alpha$. We determine the transverse momentum distribution of the gluons, as well as the total probability of creating pairs per unit space time volume. We find that the result is independent of the covariant gauge parameter $\alpha$ used to define arbitrary covariant background gauges. We find that our nonperturbative result is both gauge invariant and gauge parameter $\alpha$ independent.

In center-vortex theory, beyond the simplest picture of confinement several conceptual problems arise that are the subject of this paper. Recall that confinement arises through configuration averaging of phase factors associated with the gauge center group, raised to powers depending on the total Gauss link number of a vortex ensemble with a given Wilson loop. The simplest approach to confinement counts this link number by counting the number of vortices, considered in $d=3$ as infinitely long closed self-avoiding random walks of fixed step length, piercing any surface spanning the Wilson loop. Problems arise because a given vortex may pierce a given spanning surface several times without being linked or without contributing a nontrivial phase factor, or it may contribute a nontrivial phase factor appropriate to a smaller number of pierce points. We estimate the dilution factor $\alpha$, due to these inert or partially inert vortices, that reduces the ratio of fundamental string tension $K_F$ to the areal density $\rho$ of vortices from the ratio given by elementary approaches and find $\alpha =0.6\pm 0.1$. Then we show how inert vortices resolve the problem that the link number of a given vortex-Wilson-loop configuration is the same for any spanning surface of whatever area, yet a unique area (of a minimal surface) appears in the area law. Third, we discuss semiquantitatively a configuration of two distinct Wilson loops separated by a variable distance, and show how inert vortices govern the transition between two possible forms of the area law (one at small loop separation, the other at large), and point out the different behaviors in $SU(2)$ and higher groups, notably $SU(3)$. The result is a finite-range van der Waals force between the two loops. Finally, in a problem related to the double-loop problem, we argue that the analogs of inert vortices do not affect the fact that, in the $SU(3)$ baryonic area law, the mesonic string tension appears.

Future missions of gravitational-wave astronomy will be operated by space-based interferometers, covering a very wide range of frequencies. Search for stochastic gravitational-wave backgrounds (GWBs) is one of the main targets for such missions, and we here discuss the prospects for direct measurement of isotropic and anisotropic components of (primordial) GWBs around the frequency 0.1–10 Hz. After extending the theoretical basis for correlation analysis, we evaluate the sensitivity and the signal-to-noise ratio for the proposed future space interferometer missions, like Big-Bang Observer (BBO), Deci-Hertz Interferometer Gravitational-wave Observer (DECIGO), and the recently proposed Fabry-Perot type DECIGO. The astrophysical foregrounds which are expected at low frequency may be a big obstacle and may significantly reduce the signal-to-noise ratio of GWBs. As a result, the minimum detectable amplitude may reach $h^2{\Omega }_{\mathrm{gw}}={10}^{-15}\sim {10}^{-16}$, as long as foreground point sources are properly subtracted. Based on correlation analysis, we also discuss measurement of anisotropies of GWBs. As an example, the sensitivity level required for detecting the dipole moment of GWB induced by the proper motion of our local system is closely examined.

The measurement of the Shapiro time delay in binary pulsar systems with highly-inclined orbit can be affected both by the motion of the pulsar’s companion because of the finite time it takes a photon to cross the binary, and by the gravitational light bending if the orbit is sufficiently edge-on relative to the line of sight. Here we calculate the effect of retardation due to the companion’s motion on various time delays in pulsar binaries, including the Shaipro delay, the geometric lensing delay, and the lens-induced delays associated with the pulsar rotation. Our results can be applied to systems so highly inclined that near conjunction gravitational lensing of the pulsar radiation by the companion becomes important (the recently discovered double pulsar system J0737-3039 may exemplify such a system). To the leading order, the effect of retardation is to shift all the delay curves backward in time around the orbit conjunction, without affecting the shape and amplitude of the curves. The time shift is of order the photon orbit crossing time, and ranges from a second to a few minutes for the observed binary pulsar systems. In the double pulsar system J0737-3039, the motion of the companion may also affect the interpretation of the recent correlated interstellar scintillation measurements. Finally, we show that lensing sets an upper limit on the magnitude of the frame-dragging time delay caused by the companion’s spin, and makes this delay unobservable in stellar-mass binary pulsar systems.

The ${\sin }^2{\theta }_{\mathrm{W}}$ result from NuTeV falls three standard deviations from the value determined by global electroweak fits. It has been suggested that one possible explanation for this result could be the oscillation of electron neutrinos in the NuTeV beam to sterile neutrinos. This article examines several cases of masses and mixings for $3+2$ neutrino oscillation models which fit the current oscillation data at $99\%$ C.L. We conclude that electron to sterile neutrino oscillations can account for only up to a third of a standard deviation between the NuTeV determination of ${\sin }^2{\theta }_{\mathrm{W}}$ and the standard model.

We comment on the Lee-Yang zero analysis for the study of the phase structure of QCD at high temperature and baryon number density by Monte-Carlo simulations. We find that the sign problem for nonzero density QCD induces a serious problem in the finite volume scaling analysis of the Lee-Yang zeros for the investigation of the order of the phase transition. If the sign problem occurs at large volume, the Lee-Yang zeros will always approach the real axis of the complex parameter plane in the thermodynamic limit. This implies that a scaling behavior which would suggest a crossover transition will not be obtained. To clarify this problem, we discuss the Lee-Yang zero analysis for SU(3) pure gauge theory as a simple example without the sign problem, and then consider the case of nonzero density QCD. It is suggested that the distribution of the Lee-Yang zeros in the complex parameter space obtained by each simulation could be more important information for the investigation of the critical endpoint in the $(T,{\mu }_q)$ plane than the finite volume scaling behavior.

We present a complete calculation of weak boson fusion production of colorless supersymmetric particles at the LHC, using the new matrix element generator susy-madgraph . The cross sections are small, generally at the attobarn level, with a few notable exceptions which might provide additional supersymmetric parameter measurements. We discuss in detail how to consistently define supersymmetric weak couplings to preserve unitarity of weak gauge boson scattering amplitudes to fermions, and derive sum rules for weak supersymmetric couplings.

We provide a comprehensive study of the cosmic-ray muon flux and induced activity as a function of overburden along with a convenient parametrization of the salient fluxes and differential distributions for a suite of underground laboratories ranging in depth from $\sim 1$ to 8 km.w.e.. Particular attention is given to the muon-induced fast neutron activity for the underground sites and we develop a depth-sensitivity relation to characterize the effect of such background in experiments searching for WIMP dark matter and neutrinoless double-beta decay.

We investigate the prospects for neutrinoless double beta decay, texture zeros. and equalities between neutrino mass matrix elements in scenarios with vanishing determinant mass matrices for vanishing and finite ${\theta }_{13}$ mixing angles in normal and inverse mass hierarchies. For normal hierarchy and both zero and finite ${\theta }_{13}$ it is found that neutrinoless double beta decay cannot be observed by any of the present or next generation experiments, while for inverse hierarchy it is, on the contrary, accessible to experiments. Regarding texture zeros and equalities between mass matrix elements, we find that in both normal and inverse hierarchies with ${\theta }_{13}=0$ no texture zeros nor any such equalities can exist apart from the obvious ones. For ${\theta }_{13}\ne 0$ some texture zeros become possible. In normal hierarchy two texture zeros occur if $8.1\times {10}^{-2}\le |\sin {\theta }_{13}|\le 9.1\times {10}^{-2}$ while in inverse hierarchy three are possible, one with $|\sin {\theta }_{13}|\ge 7\times {10}^{-3}$ and two others with $|\sin {\theta }_{13}|\ge 0.18$. All equalities between mass matrix elements are impossible with ${\theta }_{13}\ne 0$.

We report on precision measurements of the masses and widths of the narrow, orbitally excited states $D_1^0$ and $D_2^{*0}$ using the CDF II detector at the Fermilab Tevatron. Both states (collectively called $D^{**}$) are reconstructed in the decay channel $D^{**}\to D^{*+}{\pi }^{-}$. The $D_2^{*0}$ is also reconstructed in the $D^{**}\to D^{+}{\pi }^{-}$ channel. Using a data set with an integrated luminosity of $210{\mathrm{pb}}^{-1}$, the measured masses and widths for the $D_1^0$ are $2421.7\pm 0.7\pm 0.6\mathrm{MeV}/c^2$ and $20.0\pm 1.7\pm 1.3\mathrm{MeV}/c^2$ respectively, while for the $D_2^{*0}$ they are $2463.3\pm 0.6\pm 0.8\mathrm{MeV}/c^2$ and $49.2\pm 2.3\pm 1.2\mathrm{MeV}/c^2$. These values are currently the single best measurements available.

The manifestly gauge invariant exact renormalization group provides a framework for performing continuum computations in $SU(N)$ Yang-Mills theory, without fixing the gauge. We use this formalism to compute the two-loop $\beta$ function in a manifestly gauge invariant way, and without specifying the details of the regularization scheme.

We study the index of the Ginsparg-Wilson Dirac operator on a noncommutative torus numerically. To do this, we first formulate an admissibility condition which suppresses the fluctuation of gauge fields. Assuming this condition, we generate gauge configurations randomly, and find various configurations with nontrivial indices. We show one example of configurations with index 1 explicitly. This result provides the first evidence that nontrivial indices can be naturally defined on the noncommutative torus by utilizing the Ginsparg-Wilson relation and the admissibility condition.

The Lazarus project was designed to make the most of limited 3D binary black-hole simulations, through the identification of perturbations at late times, and subsequent evolution of the Weyl scalar ${\Psi }_4$ via the Teukolsky formulation. Here we report on new developments, employing the concept of the “quasi-Kinnersley” (transverse) frame, valid in the full nonlinear regime, to analyze late-time numerical space-times that should differ only slightly from Kerr. This allows us to extract the essential information about the background Kerr solution, and through this, to identify the radiation present. We explicitly test this procedure with full-numerical evolutions of Bowen-York data for single spinning black holes, head-on and orbiting black holes near the ISCO regime. These techniques can be compared with previous Lazarus results, providing a measure of the numerical-tetrad errors intrinsic to the method, and giving as a by-product a more robust wave extraction method for numerical elativity.

The scalar field contribution to entropy is studied in an arbitrary $D$ dimensional one parameter rotating spacetime by semiclassical methods. By introducing a zenith angle dependent cutoff parameter, the generalized area law is derived. The nonrotating limit can be taken smoothly and it yields known results. The derived area law is then applied to the Bañados-Teitelboim-Zanelli black hole in $(2+1)$ dimensions and the Kerr-Newman black hole in $(3+1)$ dimensions. The generalized area law is reconfirmed by the Euclidean path integral method for the quantized scalar field. The scalar field mass contribution is discussed briefly.

Recent work, which treats the Hawking radiation as a semiclassical tunneling process at the horizon of the Schwarzschild and Reissner-Nordström spacetimes, indicates that the exact radiant spectrum is no longer pure thermal after considering the black hole background as dynamical and the conservation of energy. In this paper, we extend the method to investigate Hawking radiation as massless particles tunneling across the event horizon of the Kerr black hole and that of charged particles from the Kerr-Newman black hole by taking into account the energy conservation, the angular momentum conservation, and the electric charge conservation. Our results show that when self-gravitation is considered, the tunneling rate is related to the change of Bekenstein-Hawking entropy and the derived emission spectrum deviates from the pure thermal spectrum, but is consistent with an underlying unitary theory.

The current knowledge of cosmological structure formation suggests that Cold Dark Matter (CDM) halos possess a nonspherical density profile, implying that cosmic structures can be potential sources of gravitational waves via power transfer from scalar perturbations to tensor metric modes in the nonlinear regime. By means of a previously developed mathematical formalism and a triaxial collapse model, we numerically estimate the stochastic gravitational-wave background generated by CDM halos during the fully nonlinear stage of their evolution. Our results suggest that the energy density associated with this background is comparable to that produced by primordial tensor modes at frequencies $\nu \approx {10}^{-18}–{10}^{-17}\mathrm{Hz}$ if the energy scale of inflation is $V^{1/4}\approx 1–2\times {10}^{15}\mathrm{GeV}$, and that these gravitational waves could give rise to several cosmological effects, including secondary CMB anisotropy and polarization.

The physics potential of beta beams is investigated from low to very high gamma values and it is compared to superbeams and neutrino factories. The gamma factor and the baseline are treated as continuous variables in the optimization of the beta beam, while a fixed mass water Cherenkov detector or a totally active scintillator detector is assumed. We include in our discussion also the gamma dependence of the number of ion decays per year. For low gamma, we find that a beta beam could be a very interesting alternative to a superbeam upgrade, especially if it is operated at the second oscillation maximum to reduce correlations and degeneracies. For high gamma, we find that a beta beam could have a potential similar to a neutrino factory. In all cases, the sensitivity of the beta beams to $CP$ violation is very impressive if similar neutrino and antineutrino event rates can be achieved.

We present the first measurement of the $A_2$ and $A_3$ angular coefficients of the $W$ boson produced in proton-antiproton collisions. We study $W\to e{\nu }_e$ and $W\to \mu {\nu }_{\mu }$ candidate events produced in association with at least one jet at CDF, during Run Ia and Run Ib of the Tevatron at $\sqrt{s}=1.8\mathrm{TeV}$. The corresponding integrated luminosity was $110{\mathrm{pb}}^{-1}$. The jet balances the transverse momentum of the $W$ and introduces QCD effects in $W$ boson production. The extraction of the angular coefficients is achieved through the direct measurement of the azimuthal angle of the charged lepton in the Collins-Soper rest-frame of the $W$ boson. The angular coefficients are measured as a function of the transverse momentum of the $W$ boson. The electron, muon, and combined results are in good agreement with the standard model prediction, up to order ${\alpha }_s^2$ in QCD.

We present the standard model prediction for the eight angular coefficients of the $W$ boson, which completely describes its differential cross section in hadron collisions. These coefficients are ratios of the $W$ helicity cross sections and the total unpolarized cross section. We also suggest a technique to experimentally extract the coefficients, which we demonstrate in the Collins-Soper azimuthal-angle analysis.