Non-Abelian topological string defects exist in QCD with the spontaneous chiral symmetry breaking ${U(N}_f{)}_L\times {U(N}_f{)}_R\to {U(N}_f{)}_V.$ Anomaly effects lead to domain walls connected to these strings. In the framework of the linear sigma model, we find the configuration of these defects. Also, we show that in this model metastable $\mathrm{CP}$ violating vacua exist. Strings as well as extended regions of metastable vacua may form during the chiral transition, which could have interesting effects.

We apply the closed-time path integral formalism to study the medium effects of nonequilibrium gluon matter. We derive the medium modified resummed gluon propagator to the one loop level in nonequilibrium in the covariant gauge. The gluon propagator we derive can be used to remove the infrared divergences in the secondary parton collisions to study the thermalization of minijet parton plasma at BNL RHIC and CERN LHC.

Experimenters report an upper limit if the signal they are trying to detect is nonexistent or below their experiment’s sensitivity. Such experiments may be contaminated with a background too poorly understood to subtract. If the background is distributed differently in some parameter from the expected signal, it is possible to take advantage of this difference to get a stronger limit than would be possible if the difference in distribution were ignored. We discuss the “maximum gap” method, which finds the best gap between events for setting an upper limit, and generalize to the “optimum interval” method, which uses intervals with especially few events. These methods, which apply to the case of relatively small backgrounds, do not use binning, are relatively insensitive to cuts on the range of the parameter, are parameter independent (i.e., do not change when a one-one change of variables is made), and provide true, though possibly conservative, classical one-sided confidence intervals.

We combine Witten’s renormalization group with the matching conditions of Bernreuther and Wetzel to calculate at next-to-leading order the complete heavy-quark contribution to the neutral-current axial-charge measurable in neutrino-proton elastic scattering. Our results are manifestly renormalization group invariant.

We consider aspects of holography in the $\mathrm{pp}$-wave limit of ${\mathrm{AdS}}_5\times S^5.$ This geometry contains two $R^4\mathrm{’}\mathrm{s},$ one obtained from ${\mathrm{AdS}}_5$ directions, and the other from the $S^5.$ We argue that the holographic direction in the $\mathrm{pp}$-wave background can be taken to be r, the radial direction in the first $R^4.$ Normalizable modes correspond to states, and non-normalizable modes correspond to deformations of the boundary theory. In the strict $\mathrm{pp}$-wave limit, there are additional non-normalizable modes in the second $R^4,$ which have no apparent super-Yang-Mills interpretation. We outline the procedure for calculating correlation functions holographically.

We study in some detail the properties of a previously proposed new class of string and brane models whose world-sheet (world-volume) actions are built with a modified reparametrization-invariant measure of integration and which do not contain any ad hoc dimensionful parameters. The ratio of the new and the standard Riemannian integration measure densities plays the role of a dynamically generated string or brane tension. The latter is identified as (the magnitude of) an effective (non-Abelian) electric field strength on the world-sheet or world-volume obeying the standard Gauss-law constraint. As a result a simple classical mechanism for confinement via modified-measure “color” strings is proposed where the colorlessness of the “hadrons” is an automatic consequence of the new string dynamics.

We argue that the gauge theory dual to the type IIB string theory in a ten-dimensional $\mathrm{pp}$-wave background resides on a Euclidean subspace spanning four of the eight transverse coordinates. We then show that the evolution of the string along one of the light cone directions in the bulk is identifiable as the RG flow of the gauge theory, a relation facilitating the “holography” of the $\mathrm{pp}$-wave background. The “holography” reorganizes the dual gauge theory into theories defined over Hilbert subspaces of fixed R charge. The reorganization breaks the $\mathrm{SO}\mathrm{}(4,2)\mathrm{}\times \mathrm{SO}\mathrm{}\left(6\right)\mathrm{}$ symmetry to a maximal subgroup $\mathrm{SO}\mathrm{}\left(4\right)\mathrm{}\times \mathrm{SO}\mathrm{}\left(4\right)\mathrm{}$ spontaneously. We argue that the low-energy string modes may be regarded as Goldstone modes resulting from such a symmetry breaking pattern.

The Polyakov world-line path integral describing the propagation of gluon field quanta is constructed by employing the background gauge fixing method and is subsequently applied to analytically compute the divergent terms of the one (gluonic) loop effective action to fourth order in perturbation theory. The merits of the proposed approach are that, to a given order, it reduces to performing two integrations, one over a set of Grassmann and one over a set of Feynman-type parameters, through which one manages to accommodate all Feynman diagrams entering the computation at once.

The low energy dynamics of vortices in self-dual Abelian Higgs theory in $\mathrm{}(2+1)\mathrm{}$-dimensional spacetime is of second order in vortex velocity and characterized by the moduli space metric. When the Chern-Simons term with a small coefficient is added to the theory, we show that a term linear in vortex velocity appears and can be consistently added to the second order expression. We provide an additional check of the first and second order terms by studying the angular momentum in field theory.

We reexamine a scenario in which photons and gravitons arise as Goldstone bosons associated with the spontaneous breaking of Lorentz invariance. We study the emergence of Lorentz invariant low energy physics in an effective field theory framework, with non-Lorentz invariant effects arising from radiative corrections and higher order interactions. Spontaneous breaking of the Lorentz group also leads to additional exotic but weakly coupled Goldstone bosons, whose dispersion relations we compute. The usual cosmological constant problem is absent in this context: being a Goldstone boson, the graviton can never develop a potential, and the existence of a flat spacetime solution to the field equations is guaranteed.

Using the $\kappa$-symmetric action for a D3-brane, we study the interaction between its world-volume fermions and a bosonic type IIB supergravity background preserving 4-dimensional Lorentz invariance. We find that the renormalizable terms in the action include only coupling between the fermions and the 3-form flux in the combination ${(*}_6{G}_{\mathrm{}\left(3\right)\mathrm{}}-{\mathrm{iG}}_{\mathrm{}\left(3\right)\mathrm{}}),$ which is zero for a class of supersymmetric and nonsupersymmetric solutions. We also find the magnetic and electric dipole moments for the fermions, which are proportional to the derivative of the dilaton axion. We show that different gauges to fix the $\kappa$ symmetry give the same interaction terms, and prove that these terms are also $SL(2,\mathbf{R})$ self-dual. We interpret our results in terms of $\mathcal{N}=1\mathrm{}$ supersymmetric gauge theory on the D-brane.

We study the general form of the possible kinetic terms for 2-form fields in four dimensions, under the restriction that they have a semibounded energy density. This is done by using covariant symplectic techniques and generalizes previous partial results in this direction.

We study the fate of U(1) strings embedded in a non-Abelian gauge theory with the hierarchical pattern of symmetry breaking $G\mathrm{U}\left(1\right)$ nothing, $V\gg v.\mathrm{}$ While in the low-energy limit the Abrikosov-Nielsen-Olesen string (flux tube) is perfectly stable, when considered in the full theory it is metastable. We consider the simplest example: the magnetic flux tubes in SU(2) gauge theory with adjoint and fundamental scalars. First, the adjoint scalar develops a vacuum expectation value V breaking SU(2) down to U(1). Then, at a much lower scale, the fundamental scalar (quark) develops a vacuum expectation value $v$ creating the Abrikosov-Nielsen-Olesen string. [We also consider an alternative scenario in which the second breaking, $\mathrm{U}\left(1\right)$ nothing, is due to an adjoint field.] We suggest an illustrative Ansatz describing an “unwinding” in SU(2) of the winding inherent in the Abrikosov-Nielsen-Olesen strings in U(1). This Ansatz determines an effective 2D theory for the unstable mode on the string world sheet. We calculate the decay rate (per unit length of the string) in this Ansatz and then derive a general formula. The decay rate is exponentially suppressed. The suppressing exponent is proportional to the ratio of the monopole mass squared to the string tension, which is quite natural in view of the string breaking through the monopole-antimonopole pair production. We compare our result with the one given by Schwinger’s formula dualized for describing monopole-antimonopole pair production in a magnetic field.

We prove the uniqueness of higher dimensional (dilatonic) charged black holes in static and asymptotically flat spacetimes for an arbitrary vector-dilaton coupling constant. An application to the uniqueness of a wide class of black p-branes is also given.

We compute the quasinormal modes associated with the decay of the massless scalar field around a small Schwarzschild–anti-de Sitter black hole. The computations show that when the horizon radius is much less than the anti–de Sitter radius, the imaginary part of the frequency goes to zero as $r_{+}^{d-2}$ while the real part of $\omega$ decreases to its minimum and then goes to $d-1.$ Thus the quasinormal modes approach the usual AdS modes in the limit $r_{+}\to 0.$ This agrees with suggestions of Horowitz and Hubeny [Phys. Rev. D 62, 024027 (2000)].

We consider a massless scalar field propagating in a weakly curved spacetime whose metric is a solution to the linearized Einstein field equations. The spacetime is assumed to be stationary and asymptotically flat, but no other symmetries are imposed—the spacetime can rotate and deviate strongly from spherical symmetry. We prove that the late-time behavior of the scalar field is identical to what it would be in a spherically symmetric spacetime: it decays in time according to an inverse power law, with a power determined by the angular profile of the initial wave packet (Price falloff theorem). The field’s late-time dynamics is insensitive to the nonspherical aspects of the metric, and it is governed entirely by the spacetime’s total gravitational mass; other multipole moments, and in particular the spacetime’s total angular momentum, do not enter in the description of the field’s late-time behavior. This extended formulation of Price’s falloff theorem appears to be at odds with previous studies of radiative decay in the spacetime of a Kerr black hole. We show, however, that the contradiction is only apparent, and that it is largely an artifact of the Boyer-Lindquist coordinates adopted in these studies.

Einstein’s equivalence principle in classical physics is a rule stating that the effect of gravitation is locally equivalent to the acceleration of an observer. The principle determines the motion of test particles uniquely (modulo very broad general assumptions). We show that the same principle applied to a quantum particle described by a wave function on a Newtonian gravitational background determines its motion with a similar degree of uniqueness.

We study adiabatic and isocurvature perturbation spectra produced by a period of cosmological inflation driven by two scalar fields. We show that there exists a model-independent consistency condition for all two-field models of slow-roll inflation, despite allowing for model-dependent linear processing of curvature and isocurvature perturbations during and after inflation on super-horizon scales. The scale dependence of all spectra are determined solely in terms of slow-roll parameters during inflation and the dimensionless cross-correlation between curvature and isocurvature perturbations. We present additional model-dependent consistency relations that may be derived in specific two-field models, such as the curvaton scenario.

The stability of scalar quintessence potentials under quantum fluctuations is investigated for both uncoupled models and models with a coupling to fermions. We find that uncoupled models are usually stable in the late universe. However, the coupling to fermions is severely restricted. We check whether a graviton induced fermion-quintessence coupling is compatible with this restriction.

We demonstrate the existence of shear-free cosmological models with rotation and expansion which support inflationary scenarios. The corresponding metrics belong to the family of spatially homogeneous models with the geometry of the closed universe (Bianchi type IX). We show that the global vorticity does not prevent inflation and can even accelerate it.