The boundary stress tensor approach has proven extremely useful in defining mass and angular momentum in asymptotically anti-de Sitter spaces with CFT duals. An integral part of this method is the use of boundary counterterms to regulate the gravitational action and stress tensor. In the presence of matter, however, ambiguities may arise that are related to the addition of possible finite counterterms. We demonstrate this explicitly for $R$-charged black holes in ${\mathrm{AdS}}_5$, where introduction of a finite counterterm proportional to ${\varphi }^2$ is necessary to properly reproduce the expected mass/charge relation for the black holes.

We investigate the evolution of infinite strings as a part of a complete cosmic string network in flat space. We perform a simulation of the network which uses functional forms for the string position and thus is exact to the limits of computer arithmetic. Our results confirm that the wiggles on the strings obey a scaling law described by universal power spectrum. The average distance between long strings also scales accurately with the time. These results suggest that small-scale structure will also scale in an expanding universe, even in the absence of gravitational damping.

We consider the effect of compactification of extra dimensions on the onset of classical chaotic mixmaster behavior during cosmic contraction. Assuming a universe that is well-approximated as a four-dimensional Friedmann–Robertson–Walker model (with negligible Kaluza–Klein excitations) when the contraction phase begins, we identify compactifications that allow a smooth contraction and delay the onset of chaos until arbitrarily close to the big crunch. These compactifications are defined by the de Rham cohomology (Betti numbers) and Killing vectors of the compactification manifold. We find compactifications that control chaos in vacuum Einstein gravity, as well as in string theories with $\mathcal{N}=1$ supersymmetry and M-theory. In models where chaos is controlled in this way, the universe can remain homogeneous and flat until it enters the quantum gravity regime. At this point, the classical equations leading to chaotic behavior can no longer be trusted, and quantum effects may allow a smooth approach to the big crunch and transition into a subsequent expanding phase. Our results may be useful for constructing cosmological models with contracting phases, such as the ekpyrotic/cyclic and pre-big bang models.

Gaussianity is the very basis for derivation of the cosmological parameters from the cosmic microwave background (CMB) angular power spectrum. Non-Gaussian signal, whether originated from experimental error or primordial source, could mimic extra power in the power spectrum, thereby leading to a wrong set of parameters. In this paper we present a new Gaussianity analysis of the derived CMB signals. It is based on the trigonometric moments of phases, which can be concluded with a “mean angle,” allowing us to see the global trend of non-Gaussianity of the signals. These moments are also closely related to the Pearson’s random walks. We apply these analyses on the derived CMB maps and their different morphologies manifest themselves through these functions. We also comment on rotational invariance of the trigonometric moments of phases as a non-Gaussianity test.

We consider the problem of axion production by bremsstrahlung emission in a nuclear medium. The usual assumption of a massless axion is replaced by more general hypotheses, so that we can describe the emission process for axions with mass up to a few MeV. We point out that in certain physical situations the contribution from nonzero mass is non-negligible. In particular, in the mechanism for the production of gamma ray bursts via emission of heavy axions the axion mass ($m_a\sim 1\mathrm{MeV}$) is comparable with the temperature of the nuclear medium, and thus can not be disregarded. Looking at our results we find, in fact, a fairly considerable reduction of the axion luminosity in that mechanism.

The spectrum of meson and diquark excitations of dense color neutral cold quark matter is investigated in the framework of a two-flavored Nambu–Jona-Lasinio–type model, including a quark $\mu$- and color ${\mu }_8$-chemical potential. It was found that, in the color superconducting (2SC) phase, i.e. at $\mu >{\mu }_c=342\mathrm{MeV}$, ${\mu }_8$ acquires rather small values $\sim 10\mathrm{MeV}$ in order to ensure the color neutrality. In this phase the $\pi$ and $\sigma$ meson masses are evaluated around $\sim 330\mathrm{MeV}$. The spectrum of scalar diquarks in the color neutral 2SC phase consists of a heavy [${\mathrm{SU}}_c(2)$-singlet] resonance with mass $\sim 1100\mathrm{MeV}$, four light diquarks with mass $3|{\mu }_8|$, and one Nambu-Goldstone boson, which is in accordance with the Goldstone theorem. Moreover, in the 2SC phase there are five light stable particles as well as a heavy resonance in the spectrum of pseudoscalar diquarks. In the color symmetric phase, i.e. for $\mu <{\mu }_c$, a mass splitting of scalar diquarks and antidiquarks is shown to arise if $\mu \ne 0$, contrary to the case of $\mu =0$, where the masses of scalar antidiquarks and diquarks are degenerate at the value $\sim 700\mathrm{MeV}$. If the coupling strength in the pseudoscalar diquark channel is the same as in the scalar diquark one (as for QCD-inspired Nambu–Jona-Lasinio models), then in the color symmetric phase pseudoscalar diquarks are not allowed to exist as stable particles.

We compute the total cross section as well as angular and energy distributions for process $e^{+}{e}^{-}\to \gamma \gamma \gamma$ with both unpolarized and polarized beams in the framework of noncommutative quantum electrodynamics (NCQED). The calculation is performed in the center of mass of colliding electron and positron and is evaluated for energies and integrated luminosities appropriate to future linear colliders. We find that by using unpolarized beams it is possible to probe the Lorentz symmetry violating azimuthal dependence of the cross section. Furthermore, with polarized beams the left-right asymmetry of the $CP$ violating NCQED amplitudes can be used to obtain bounds on the noncommutative scale ${\Lambda }_{\mathrm{NC}}$ which exceed 1.0 TeV.

We study the one-loop sensitivity of the $WWV$ ($V=\gamma ,Z$) vertex to the new massive gauge bosons predicted by the minimal $S{U}_L(3)\times U_X(1)$ model, which have unusual couplings to the standard model (SM) gauge bosons. A gauge-fixing procedure covariant under the $S{U}_L(2)\times U_Y(1)$ group was introduced for these new gauge bosons (dubbed bileptons) in order to generate gauge-invariant Green functions. The similarities between this procedure and the unconventional quantization scheme of the background field method are discussed. It is found that, for relatively light bileptons, with a mass ranging from $2m_W$ to $6m_W$, the radiative corrections to the form factors associated with the $WWV$ vertex can be of the same order of magnitude than the SM one. In the case of heavier bileptons, their contribution is smaller by about one and 2 orders of magnitude than their SM counterpart.

This paper gives results for the spectrum, all allowed E1 radiative partial widths (and some important M1 widths) and all open-charm strong decay amplitudes of all 40 $c\overline{c}$ states expected up to the mass of the $4\mathrm{S}$ multiplet, just above 4.4 GeV. The spectrum and radiative widths are evaluated using two models, the relativized Godfrey-Isgur model and a nonrelativistic potential model. The electromagnetic transitions are evaluated using Coulomb plus linear plus smeared hyperfine wave functions, both in a nonrelativistic potential model and in the Godfrey-Isgur model. The open-flavor strong decay amplitudes are determined assuming harmonic oscillator wave functions and the ${{}^3\mathrm{P}}_0$ decay model. This work is intended to motivate future experimental studies of higher-mass charmonia, and may be useful for the analysis of high-statistics data sets to be accumulated by the BES, CLEO, and GSI facilities.

We examine the role that the gap dependence of the pairing interaction plays in the gap equation for a weakly coupled uniform superfluid of three-flavor massless quarks near the transition temperature $T_c$. We find that the feedback effects on Landau-damped transverse gluons mediating the pairing interaction alter the gap magnitude in a way dependent on the color structure of the gap. We estimate corrections by these effects to the parameters characterizing the fourth order terms in the Ginzburg-Landau free energy and ensure the stability of a color-flavor locked state near $T_c$.

We consider the effect of a six-fermion interaction of the t’Hooft form in the quark-quark channel on the ground state of matter at finite density. The coupling constant for this new term is varied within the limits suggested by naturalness. The flavor-mixing effects of the additional term destabilize the color-flavor-locked and, to a lesser extent, the two-flavor color-superconducting phases of quark matter, especially for positive values of the coupling. For some values of the coupling, the critical density for color-flavor-locked phase is nearly larger than the maximum density in the neutron stars. We comment on the implications for neutron-star evolution.

A Dalitz plot analysis of approximately 12 500 $D^0$ events reconstructed in the hadronic decay $D^0\to {\overline{K}}^0{K}^{+}{K}^{-}$ is presented. This analysis is based on a data sample of $91.5{\mathrm{fb}}^{-1}$ collected with the BABAR detector at the PEP-II asymmetric-energy $e^{+}{e}^{-}$ storage rings at SLAC running at center-of-mass energies on and 40 MeV below the ${\rm Y}(4S)$ resonance. The events are selected from $e^{+}{e}^{-}\to c\overline{c}$ annihilations using the decay $D^{*+}\to D^0{\pi }^{+}$. The following ratio of branching fractions has been obtained: $BR=\frac{\Gamma (D^0\to {\overline{K}}^0{K}^{+}{K}^{-})}{\Gamma (D^0\to {\overline{K}}^0{\pi }^{+}{\pi }^{-})}=(15.8\pm 0.1(\mathrm{stat}.)\pm 0.5(\mathrm{syst}.))\times {10}^{-2}.$ Estimates of fractions and phases for resonant and nonresonant contributions to the Dalitz plot are also presented. The $a_0(980)\to \overline{K}K$ projection has been extracted with little background. A search for $CP$ asymmetries on the Dalitz plot has been performed.

We report on a search for pair production of first-generation scalar leptoquarks (LQ) in $p\overline{p}$ collisions at $\sqrt{s}=1.96\mathrm{TeV}$ using an integrated luminosity of $203{\mathrm{pb}}^{-1}$ collected at the Fermilab Tevatron collider by the CDF experiment. We observe no evidence for LQ production in the topologies arising from $\mathrm{LQ}\overline{\mathrm{LQ}}\to eqeq$ and $\mathrm{LQ}\overline{\mathrm{LQ}}\to eq\nu q$, and derive 95% C.L. upper limits on the LQ production cross section. The results are combined with those obtained from a separately reported CDF search in the topology arising from $\mathrm{LQ}\overline{\mathrm{LQ}}\to \nu q\nu q$ and 95% C.L. lower limits on the LQ mass as a function of $\beta =\mathrm{BR}(\mathrm{LQ}\to eq)$ are derived. The limits are 236, 205 and $145\mathrm{GeV}/c^2$ for $\beta =1$, $\beta =0.5$ and $\beta =0.1$, respectively.

We report on a search for the rare decay ${\overline{B}}^0\to D^{*0}\gamma$, which in the standard model is dominated by $W$-exchange. The analysis is based on a data sample comprising $87.8\times {10}^6$ $B\overline{B}$ pairs collected with the BABAR detector at the PEP-II asymmetric-energy $B$ Factory at SLAC. No significant signal is observed, and an upper limit on the branching fraction of $2.5\times {10}^{-5}$ at the 90% confidence level is obtained.

In the Tolman model, there exist two quite different branches of solutions—generic Lemaître-Tolman-Bondi (LTB) ones and T-spheres as a special case. We show that, nonetheless, T-spheres can be obtained as a limit of the class of LTB solutions having no origin and extending to infinity with the areal radius approaching constant. It is shown that all singularities of T-models are inherited from those of corresponding LTB solutions. In doing so, the disk-type singularity of a T-sphere is the analog of shell-crossing.

Electromagnetic and (linearized) gravitational interactions of the Kalb-Ramond (KR) field, derived from an underlying ten-dimensional heterotic string in the zero slope limit, are studied in a five-dimensional background Randall-Sundrum I spacetime with standard model fields confined to the visible brane having negative tension. The warp factor responsible for generating the gauge hierarchy in the Higgs sector is seen to appear inverted in the KR field couplings, when reduced to four dimensions. This leads to dramatically enhanced rotation, far beyond observational bounds, of the polarization plane of electromagnetic and gravitational waves, when scattered by a homogeneous KR background. Possible reasons for the conflict between theory and observation are discussed.

Neutrino oscillations can be affected by decoherence induced e.g. by Planck scale suppressed interactions with the space-time foam predicted in some approaches to quantum gravity. We study the prospects for observing such effects at IceCube, using the likely flux of TeV antineutrinos from the Cygnus spiral arm. We formulate the statistical analysis for evaluating the sensitivity to quantum decoherence in the presence of the background from atmospheric neutrinos, as well as from plausible cosmic neutrino sources. We demonstrate that IceCube will improve the sensitivity to decoherence effects of $\mathcal{O}(E^2/M_{\mathrm{Pl}})$ by 17 orders of magnitude over present limits and, moreover, that it can probe decoherence effects of $\mathcal{O}(E^3/M_{\mathrm{Pl}}^2)$ which are well beyond the reach of other experiments.

It has been pointed out that it is impossible to obtain a unitary implementation of the dynamics for the polarized Gowdy $T^3$ cosmologies in an otherwise satisfactory, nonperturbative canonical quantization proposed for these spacetimes. By introducing suitable techniques to deal with deparametrized models in cosmology that possess an explicit time dependence (as it is the case for the toroidal Gowdy model), we present in this paper a detailed analysis about the roots of this failure of unitarity. We investigate the impediments to a unitary implementation of the evolution by considering modifications to the dynamics. These modifications may be regarded as perturbations. We show in a precise manner why and where unitary implementability fails in our system, and prove that the obstructions are extremely sensitive to modifications in the Hamiltonian that dictates the time evolution of the symmetry-reduced model. We are able to characterize to a certain extent how far the model is from unitarity. Moreover, we demonstrate that the dynamics can actually be approximated as much as one wants by means of unitary transformations.

Scalar fields coupled to three-dimensional gravity are considered. We uncover a scaling symmetry present in the black hole reduced action, and use it to prove a Smarr formula valid for any potential. We also prove that nonrotating hairy black holes exists only for positive total energy. The extension to higher dimensions is also considered.

The generalized Chaplygin gas is characterized by the equation of state $p=-A/{\rho }^{\alpha }$, with $\alpha >-1$ and $w>-1$. We generalize this model to allow for the cases where $\alpha <-1$ or $w<-1$. This generalization leads to three new versions of the generalized Chaplygin gas: an early phantom model in which $w\ll -1$ at early times and asymptotically approaches $w=-1$ at late times, a late phantom model with $w\approx -1$ at early times and $w\to -\infty$ at late times, and a transient model with $w\approx -1$ at early times and $w\to 0$ at late times. We consider these three cases as models for dark energy alone and examine constraints from type Ia supernovae and from the subhorizon growth of density perturbations. The transient Chaplygin gas model provides a possible mechanism to allow for a currently accelerating universe without a future horizon, while some of the early phantom models produce $w<-1$ without either past or future singularities.