In the large-$N_c$ limit of QCD, the expansion of the vacuum polarization at low energies determines the whole function at any arbitrarily large (but finite) energy. This result is an immediate consequence of the theory of Pade approximants to Stieltjes functions.

We show that, in frameworks of the economical 3-3-1 model, all fermions get masses. At the tree level, one up-quark and two down-quarks are massless, but the one-loop corrections give all quarks the consistent masses. This conclusion is in contradiction to the previous analysis in which the third scalar triplet has been introduced. This result is based on the key properties of the model: First, there are three quite different scales of vacuum expectation values: $\omega \sim \mathcal{O}(1)\mathrm{TeV}$, $v\approx 246\mathrm{GeV}$, and $u\sim \mathcal{O}(1)\mathrm{GeV}$. Second, there exist two types of Yukawa couplings with different strengths: the lepton-number conserving couplings $h$’s and the lepton-number violating ones $s$’s satisfying the condition in which the second are much smaller than the first ones: $s\ll h$. With the acceptable set of parameters, numerical evaluation shows that in this model, masses of the exotic quarks also have different scales, namely, the $U$ exotic quark ($q_U=2/3$) gains mass $m_U\approx 700\mathrm{GeV}$, while the $D_{\alpha }$ exotic quarks ($q_{D_{\alpha }}=-1/3$) have masses in the TeV scale: $m_{D_{\alpha }}\in 10–80\mathrm{TeV}$.

We construct smooth BPS three-charge geometries that resolve the zero-entropy singularity of the $U(1)\times U(1)$ invariant black ring. This singularity is resolved by a geometric transition that results in geometries without any branes sources or singularities but with nontrivial topology. These geometries are both ground states of the black ring, and nontrivial microstates of the D1-D5-P system. We also find the form of the geometries that result from the geometric transition of $N$ zero-entropy black rings, and argue that, in general, such geometries give a very large number of smooth bound-state three-charge solutions, parametrized by $6N$ functions. The generic microstate solution is specified by a four-dimensional hyper-Kähler geometry of a certain signature, and contains a “foam” of nontrivial two-spheres. We conjecture that these geometries will account for a significant part of the entropy of the D1-D5-P black hole, and that Mathur’s conjecture might reduce to counting certain hyper-Kähler manifolds.

We determine the fermionic collective modes of a quark-gluon plasma which is anisotropic in momentum space. We calculate the fermion self-energy in both the imaginary- and real-time formalisms and find that numerically and analytically (for two special cases) there are no unstable fermionic modes. In addition we demonstrate that in the hard-loop limit the Kubo-Martin-Schwinger condition, which relates the off-diagonal components of the real-time fermion self-energy, holds even for the anisotropic, and therefore nonequilibrium, quark-gluon plasma considered here. The results obtained here set the stage for the calculation of the nonequilibrium photon production rate from an anisotropic quark-gluon plasma.

The geometrical meaning of the Eddington-Finkelstein coordinates of Schwarzschild spacetime is well understood: (i) the advanced-time coordinate $v$ is constant on incoming light cones that converge toward $r=0$, (ii) the angles $\theta$ and $\varphi$ are constant on the null generators of each light cone, (iii) the radial coordinate $r$ is an affine-parameter distance along each generator, and (iv) $r$ is an areal radius, in the sense that $4\pi r^2$ is the area of each two-surface $(v,r)=\mathrm{\text{constant}}$. The light-cone gauge of black-hole perturbation theory, which is formulated in this paper, places conditions on a perturbation of the Schwarzschild metric that ensure that properties (i)–(iii) of the coordinates are preserved in the perturbed spacetime. Property (iv) is lost, in general, but it is retained in exceptional situations that are identified in this paper. Unlike other popular choices of gauge, the light-cone gauge produces a perturbed metric that is expressed in a meaningful coordinate system; this is a considerable asset that greatly facilitates the task of extracting physical consequences. We illustrate the use of the light-cone gauge by calculating the metric of a black hole immersed in a uniform magnetic field. We construct a three-parameter family of solutions to the perturbative Einstein-Maxwell equations and argue that it is applicable to a broader range of physical situations than the exact, two-parameter Schwarzschild-Melvin family.

Continuing work initiated in an earlier publication [Phys. Rev. D 69, 084007 (2004)], we construct a system of light-cone coordinates based at a geodesic world line of an arbitrary curved spacetime. The construction involves (i) an advanced-time or a retarded-time coordinate that labels past or future light cones centered on the world line, (ii) a radial coordinate that is an affine parameter on the null generators of these light cones, and (iii) angular coordinates that are constant on each generator. The spacetime metric is calculated in the light-cone coordinates, and it is expressed as an expansion in powers of the radial coordinate in terms of the irreducible components of the Riemann tensor evaluated on the world line. The formalism is illustrated in two simple applications, the first involving a comoving world line of a spatially flat cosmology, the other featuring an observer placed on the axis of symmetry of Melvin’s magnetic universe.

This paper presents a comprehensive study of the fundamental quasinormal modes of all standard model fields propagating on a brane embedded in a higher-dimensional rotating black-hole spacetime. The equations of motion for fields with spin $s=0$, $1/2$ and 1 propagating in the induced-on-the-brane background are solved numerically, and the dependence of their QN spectra on the black-hole angular momentum and dimensionality of spacetime is investigated. It is found that the brane-localized field perturbations are longer-lived when the higher-dimensional black hole rotates faster, while an increase in the number of transverse-to-the-brane dimensions reduces their lifetime. Finally, the quality factor $Q$, that determines the best oscillator among the different field perturbations, is investigated and found to depend on properties of both the particular field studied (spin, multipole numbers) and the gravitational background (dimensionality, black-hole angular momentum parameter).

An electrically charged black hole solution with scalar hair in four dimensions is presented. The self-interacting scalar field is real and it is minimally coupled to gravity and electromagnetism. The event horizon is a surface of negative constant curvature and the asymptotic region is locally an AdS spacetime. The asymptotic falloff of the fields is slower than the standard one. The scalar field is regular everywhere except at the origin and is supported by the presence of electric charge which is bounded from above by the AdS radius. In turn, the presence of the real scalar field smooths the electromagnetic potential everywhere. Regardless the value of the electric charge, the black hole is massless and has a fixed temperature. The entropy follows the usual area law. It is shown that there is a nonvanishing probability for the decay of the hairy black hole into a charged black hole without scalar field. Furthermore, it is found that an extremal black hole without scalar field is likely to undergo a spontaneous dressing up with a nontrivial scalar field, provided the electric charge is below a critical value.

We consider asymptotically anti-de Sitter gravity coupled to tachyonic scalar fields with mass at or slightly above the Breitenlohner-Freedman bound in $d\ge 4$ spacetime dimensions. The boundary conditions in these “designer gravity” theories are defined in terms of an arbitrary function $W$. We give a general argument that the Hamiltonian generators of asymptotic symmetries for such systems will be finite, and proceed to construct these generators using the covariant phase space method. The direct calculation confirms that the generators are finite and shows that they take the form of the pure gravity result plus additional contributions from the scalar fields. By comparing the generators to the spinor charge, we derive a lower bound on the gravitational energy when $W$ has a global minimum and the Breitenlohner-Freedman bound is not saturated.

It is believed that soon after the Planck era, spacetime should have a semiclassical nature. In this context we consider quantum fields propagating in a classical gravitational field and study the backreaction of these fields, using the expected value of the energy-momentum tensor as source of the gravitational field. According to this theory, the escape from general relativity theory is unavoidable. Two geometric counter-term are needed to regularize the divergences which come from the expected value. There is a parameter associated to each counter-term and in this work we found numerical solutions of this theory to particular initial conditions, for general Bianchi Type I spaces. We show that even though there are spurious solutions some of them can be considered physical. These physical solutions include de Sitter and Minkowski that are obtained asymptotically.

The tight coupling expansion, appropriately generalized to include large-scale magnetic fields, allows the estimate of the brightness perturbations of CMB anisotropies for typical wavelengths that are larger than the Hubble radius after matter-radiation equality. After discussing the basic features of the predecoupling initial conditions in the presence of fully inhomogeneous magnetic fields, the tight coupling expansion is studied both analytically and numerically. From the requirement that the amplitudes and phases of Sakharov oscillations are (predominantly) adiabatic and from the inferred value of the plateau in the temperature autocorrelation, the effects of the magnetized contribution can be systematically investigated and constrained.

We constrain the post-Newtonian gravity parameter $\gamma$ on kiloparsec scales by comparing the masses of 15 elliptical lensing galaxies from the Sloan Lens ACS Survey as determined in two independent ways. The first method assumes only that Newtonian gravity is correct and is independent of $\gamma$, while the second uses gravitational lensing which depends on $\gamma$. More specifically, we combine Einstein radii and radial surface-brightness gradient measurements of the lens galaxies with empirical distributions for the mass concentration and velocity anisotropy of elliptical galaxies in the local universe to predict $\gamma$-dependent probability distributions for the lens-galaxy velocity dispersions. By comparing with observed velocity dispersions, we derive a maximum-likelihood value of $\gamma =0.98\pm 0.07$ (68% confidence). This result is in excellent agreement with the prediction of general relativity that $\gamma =1$, which has previously been verified to this accuracy only on solar-system length scales.

Limits are set on anomalous $WW\gamma$ and $WWZ$ trilinear gauge couplings using $W^{+}{W}^{-}\to e^{+}{\nu }_e{e}^{-}{\overline{\nu }}_e$, $W^{+}{W}^{-}\to e^{\pm }{\nu }_e{\mu }^{\mp }{\nu }_{\mu }$, and $W^{+}{W}^{-}\to {\mu }^{+}{\nu }_{\mu }{\mu }^{-}{\overline{\nu }}_{\mu }$ events. The data set was collected by the Run II D0 detector at the Fermilab Tevatron Collider and corresponds to approximately $250{\mathrm{pb}}^{-1}$ of integrated luminosity at $\sqrt{s}=1.96\mathrm{TeV}$. Under the assumption that the $WW\gamma$ couplings are equal to the $WWZ$ couplings and using a form factor scale of $\Lambda =2.0\mathrm{TeV}$, the combined 95% C.L. one-dimensional coupling limits from all three channels are $-0.32<\Delta \kappa <0.45$ and $-0.29<\lambda <0.30$.

A generator with ${\alpha }^2$ order radiative correction effects, including both the initial state radiative corrections and the photon vacuum polarization corrections, is built for the full simulation of $e^{+}{e}^{-}\to \mathrm{\text{hadrons}}$ in a cross section scan experiment in the quarkonium energy region. The contributions from the hadron production structures including the resonances of $1^{--}$ quarkonium families and the light hadrons spectrum below 2 GeV as well as the QED continuum hadron spectrum are all taken into account in the event generation. It was employed successfully to determine the detection efficiency for selection of the events of $e^{+}{e}^{-}\to \mathrm{\text{hadrons}}$ from the data taken in the energy region from 3.650 GeV to 3.872 GeV covering both the $\psi (3686)$ and $\psi (3770)$ resonances in BES experiment. The generator reproduces the properties of hadronic event production and inclusive decays well.

We investigate parity-violating electroweak asymmetries in the elastic scattering of polarized electrons off protons within the framework of the chiral quark-soliton model ($\chi \mathrm{QSM}$). We use as input the former results of the electromagnetic and strange form factors and newly calculated SU(3) axial-vector form factors, all evaluated with the same set of four parameters adjusted several years ago to general mesonic and baryonic properties. Based on this scheme, which yields positive electric and magnetic strange form factors with ${\mu }_s=(0.08–0.13){\mu }_N$, we determine the parity-violating asymmetries of elastic polarized electron-proton scattering. The results are in a good agreement with the data of the A4, HAPPEX, and SAMPLE experiments and reproduce the full $Q^2$ range of the G0 data. We also predict the parity-violating asymmetries for the backward G0 experiment.

We study the relative contribution of partonic subprocesses to $D$ meson production and $D$ meson-triggered inclusive di-hadrons to lowest order in perturbative QCD. While gluon fusion dominates the creation of large angle $D\overline{D}$ pairs, charm on light parton scattering determines the yield of single inclusive $D$ mesons. The distinctly different nonperturbative fragmentation of $c$ quarks into $D$ mesons versus the fragmentation of quarks and gluons into light hadrons results in a strong transverse momentum dependence of anticharm content of the away side charm-triggered jet. In $p+A$ reactions, we calculate and resum the coherent nuclear-enhanced power corrections from the final-state partonic scattering in the medium. We find that single and double inclusive open charm production can be suppressed as much as the yield of neutral pions from dynamical high-twist shadowing. Effects of energy loss in $p+A$ collisions are also investigated phenomenologically and may lead to significantly weaker transverse momentum dependence of the nuclear attenuation.

Kohn and Luttinger showed that a many body system of fermions interacting via short range forces becomes superfluid even if the interaction is repulsive in all partial waves. In gauge theories such as QCD the interaction between fermions is long range and the assumptions of Kohn and Luttinger are not satisfied. We show that in a $U(1)$ gauge theory the Kohn-Luttinger phenomenon does not take place. In QCD attractive channels always exist, but there are cases in which the primary pairing channel leaves some fermions ungapped. As an example we consider the unpaired fermion in the 2SC phase of QCD with two flavors. We show that it acquires a very small gap via a mechanism analogous to the Kohn-Luttinger effect. The gap is too small to be phenomenologically relevant.

We obtain bounds on the anomalous magnetic and electric dipole moments of the tau-neutrino through the reaction $e^{+}{e}^{-}\to \nu \overline{\nu }\gamma$ at the $Z_1$-pole in the framework of a Left-Right symmetric model and a class of $E_6$ inspired models with an additional neutral vector boson $Z_{\theta }$. We use the data collected by the L3 Collaboration at LEP. For the parameters of the $E_6$ model we consider the mixing angle ${\theta }_{E_6}=37.8°$ and $M_{Z_{\theta }}=7M_{Z_1}$. We find that our bounds are of the same order of magnitude as those obtained in other extensions of the standard model.

We present model independent measurements of the helicity basis form factors in the decay $D^{+}\to K^{-}{\pi }^{+}{e}^{+}{\nu }_e$ obtained from about 2 800 decays reconstructed from a $281{\mathrm{pb}}^{-1}$ data sample collected at the $\psi (3770)$ center-of-mass energy with the CLEO-c detector. We confirm the existence of a previously observed spin-zero $K^{-}{\pi }^{+}$ component interfering with the ${\overline{K}}^{*0}$ amplitude. We see no evidence for additional $d$- or $f$-wave contributions.

We report the first observation of $B^{\pm }\to {\chi }_{c1}{\pi }^{\pm }$, a Cabibbo- and color-suppressed decay in a data sample of $386\times {10}^6$ $B\overline{B}$ events collected at the ${\rm Y}(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^{+}{e}^{-}$ collider. We observe $55\pm 10$ signal events with a statistical significance of $6.3\sigma$ including systematic uncertainties. The measured branching fraction and charge-asymmetry is $\mathcal{B}(B^{\pm }\to {\chi }_{c1}{\pi }^{\pm })=(2.2\pm 0.4\pm 0.3)\times {10}^{-5}$ and ${\mathcal{A}}_{\pi }=0.07\pm 0.18\pm 0.02$, respectively. We also determine the ratio $\mathcal{B}(B^{\pm }\to {\chi }_{c1}{\pi }^{\pm })/\mathcal{B}(B^{\pm }\to {\chi }_{c1}{K}^{\pm })=(4.3\pm 0.8\pm 0.3)\%$.