The CMB temperature power spectrum offers ambiguous evidence for the existence of horizon-scale power in the primordial power spectrum due to uncertainties in spatial curvature and the physics of cosmic acceleration as well as the observed low quadrupole. Current polarization data from WMAP provide evidence for horizon-scale power that is robust to these uncertainties. Polarization on the largest scales arises mainly from scattering at $z\lesssim 6$ when the Universe is fully ionized, making the evidence robust to ionization history variations at higher redshifts as well. A cutoff in the power spectrum is limited to $C=k_C/{10}^{-4}{\mathrm{Mpc}}^{-1}<5.2$ (95% C.L.) by polarization, only slightly weaker than joint temperature and polarization constraints in flat $\Lambda \mathrm{CDM}$ ($C<4.2$). Planck should improve the polarization limit to $C<3.6$ for any model of the acceleration epoch and ionization history as well as provide tests for foreground and systematic contamination.

A fully explicit renormalized quantum action functional is constructed for the $O(N)$ model in the auxiliary field formulation at next-to-leading order (NLO) of the $1/N$ expansion. Counterterms are consistently and explicitly derived for arbitrary constant vacuum expectation value of the scalar and auxiliary fields. The renormalized NLO pion propagator is exact at this order and satisfies Goldstone’s theorem. Elimination of the auxiliary field sector at the level of the functional provides with $\mathcal{O}(N^0)$ accuracy the renormalized effective action of the model in terms of the original variables. Alternative elimination of the pion and sigma propagators provides the renormalized NLO effective potential for the expectation values of the $N$ vector and of the auxiliary field with the same accuracy.

In this paper, we study the deformed statistics and oscillator algebras of quantum fields defined in $\kappa$-Minkowski spacetime. The twisted flip operator obtained from the twist associated with the star product requires an enlargement of the Poincaré algebra to include the dilatation generators. Here we propose a novel notion of a fully covariant flip operator and show that to the first order in the deformation parameter it can be expressed completely in terms of the Poincaré generators alone. The $R$ matrices corresponding to the twisted and the covariant flip operators are compared up to first order in the deformation parameter and they are shown to be different. We also construct the deformed algebra of the creation and annihilation operators that arise in the mode expansion of a scalar field in $\kappa$-Minkowski spacetime. We obtain a large class of such new deformed algebras which, for certain choice of realizations, reduce to results known in the literature.

In the context of spin-foam models for quantum gravity, we investigate the asymptotical behavior of the $\{6j\}$-symbol at next-to-leading order. This gives the first quantum gravity correction to the (3d) Regge action. We compute it analytically and check our results against numerical calculations. The $\{6j\}$-symbol is the building block of the Ponzano-Regge amplitudes for 3d quantum gravity, and the present analysis is directly relevant to deriving the quantum corrections to gravitational correlations in the spin-foam formalism.

The charged Bañados-Teitelboim-Zanelli (BTZ) black hole is plagued by several pathologies: (a) Divergent boundary terms are present in the action; hence, we have a divergent black-hole mass. (b) Once a finite, renormalized, mass $M$ is defined, black-hole states exist for arbitrarily negative values of $M$. (c) There is no upper bound on the charge $Q$. We show that these pathological features are an artifact of the renormalization procedure. They can be completely removed by using an alternative renormalization scheme leading to a different definition $M_0$ of the black-hole mass, which is the total energy inside the horizon. The new mass satisfies a BPS-like bound $M_0\ge \frac{\pi }{2}{Q}^2$, and the heat capacity of the hole is positive. We also discuss the black-hole thermodynamics that arises when $M_0$ is interpreted as the internal energy of the system. We show, using three independent approaches (black-hole thermodynamics, Einstein equations, and Euclidean action formulation), that $M_0$ satisfies the first law if a term describing the mechanical work done by the electrostatic pressure is introduced.

We study of the appearance of geometric quantum phases in the dynamics of a neutral particle that possess a permanent magnetic dipole moment in rotating frames in a cosmic string spacetime. The relativistic dynamics of spin-$1/2$ particle in this frame is investigated and we obtain several contributions to relativistic geometric phase due rotation and topology of spacetime. We also study the geometric phase in the nonrelativistic limit. We obtain effects analogous to the Sagnac effect and Mashhoon effect in a rotating frame in the background of a cosmic string.

In previous work [L. Blanchet and A. Le Tiec, Phys. Rev. D 78, 024031 (2008)], a model of dark matter and dark energy based on the concept of gravitational polarization was investigated. This model was shown to recover the concordance cosmological scenario ($\Lambda$-cold dark matter) at cosmological scales, and the phenomenology of the modified Newtonian dynamics at galactic scales. In this article we prove that the model can be formulated with a simple and physically meaningful matter action in general relativity. We also provide alternative derivations of the main results of the model, and some details on the variation of the action.

The density fluctuations that we observe in the universe today are thought to originate from quantum fluctuations produced during a phase of the early universe called inflation. By evolving a wave function describing two coupled Fourier modes of a scalar field forward through an inflationary epoch, we demonstrate that nonlinear effects can result in a generation of entanglement entropy between modes with different momenta in a scalar field during the inflationary period when just one of the modes is observed. Through this mechanism, the field would experience decoherence and appear more like a classical distribution today; however the mechanism is not sufficiently efficient to explain classicality. We find that the amount of entanglement entropy generated scales roughly as a power law $S\propto {\lambda }^{1.75}$, where $\lambda$ is the coupling coefficient of the nonlinear potential term. We also investigate how the entanglement entropy scales with the duration of inflation and compare various entanglement measures from the literature with the von Neumann entropy. This demonstration explicitly follows particle creation and interactions between modes; consequently, the mechanism contributing to the generation of the von Neumann entropy can be easily seen.

Distinctive patterns are predicted by quenched quark models and unquenched quark models for the lowest SU(3) baryon nonet with spin parity $J^P=1/2^{-}$. While the quenched quark models predict the lowest $1/2^{-}$ ${\Sigma }^{*}$ resonance to be above 1600 MeV, the unquenched quark models predict it to be around ${\Sigma }^{*}(1385)$ energy. Here we reexamine some old data of the $K^{-}p\to \Lambda {\pi }^{+}{\pi }^{-}$ reaction and find that besides the well-established ${\Sigma }^{*}(1385)$ with $J^P=3/2^{+}$, there is indeed some evidence for the possible existence of a new ${\Sigma }^{*}$ resonance with $J^P=1/2^{-}$ around the same mass but with broader decay width. Higher statistic data on relevant reactions are needed to clarify the situation.

Neutrino telescopes with cubic kilometer volumes have the potential to discover new particles. Among them are next to lightest supersymmetric (NLSPs) and next to lightest Kaluza-Klein (NLKPs) particles. Two NLSPs or NLKPs will transverse the detector simultaneously producing parallel charged tracks. The track separation inside the detector can be a few hundred meters. As these particles might propagate a few thousand kilometers before reaching the detector, multiple scattering could enhance the pair separation at the detector. We find that the multiple scattering will alter the separation distribution enough to increase the number of NLKP pairs separated by more than 100 meters (a reasonable experimental cut) by up to 46% depending on the NLKP mass. Vertical upcoming NLSPs will have their separation increased by 24% due to multiple scattering.

We investigate the combined effect of the repulsive vector interaction and the positive electric chemical potential on the chiral phase transition by considering neutral color superconductivity. The chiral condensate, diquark condensate, and quark number densities are solved in both two-flavor and two-plus-one-flavor Nambu-Jona-Lasinio models with the so called Kobayashi-Maskawa-’t Hooft term under the charge-neutrality constraint. We demonstrate that multiple chiral critical-point structures always exist in the Nambu-Jona-Lasinio model within the self-consistent mean-field approximation, and that the number of chiral critical points can vary from zero to four, which is dependent on the magnitudes of vector interaction and the diquark coupling. The difference between the dynamical chemical potentials induced by vector interaction for $u$ and $d$ quarks can effectively reduce the Fermi sphere disparity between the two flavors of diquark pairing. Thus the vector interaction works to significantly suppress the unstable region associated with chromomagnetic instability in the phase of neutral asymmetric homogeneous color superconductivity.

We discuss the phenomenology of the most general effective Lagrangian, up to operators of dimension five, built with standard model fields and interactions including right-handed neutrinos. In particular, we find there is a dimension five electroweak moment operator of right-handed neutrinos, not discussed previously in the literature, which could have interesting phenomenological consequences.

Using ${\alpha }^{\prime 3}$ terms of type IIB supergravity action we study higher order corrections to the nonrelativistic nonextremal D3-brane. Utilizing the corrected solution we evaluate corrections to temperature, entropy, and shear viscosity. We also compute the $\eta /s$ ratio which although within the range of validity of the supergravity approximation and in the lowest order of the correction the universal bound is respected, there is a possibility for a violation of the bound when higher terms in the expansion are taken into account.

The issue of the Becchi-Rouet-Stora-Tyutin (BRST) symmetry in the presence of the Gribov horizon is addressed in Euclidean Yang-Mills theories in the Landau gauge. The positivity of the Faddeev-Popov operator within the Gribov region enables us to convert the soft breaking of the BRST invariance exhibited by the Gribov-Zwanziger action into a nonlocal exact symmetry, displaying explicit dependence from the nonperturbative Gribov parameter. Despite its nonlocality, this symmetry turns out to be useful in order to establish nonperturbative Ward identities, allowing us to evaluate the vacuum expectation value of quantities which are BRST exact. These results are generalized to the refined Gribov-Zwanziger action introduced in Dudal et al. [Phys. Rev. D 77, 071501 (2008)], which yields a gluon propagator which is nonvanishing at the origin in momentum space, and a ghost propagator which is not enhanced in the infrared.

We consider a sterile neutrino to be an unparticle, namely, an unsterile neutrino, with anomalous dimension $\eta$ and study its mixing with a canonical active neutrino via a seesaw mass matrix. We show that there is no unitary transformation that diagonalizes the mixed propagator and a field redefinition is required. The propagating or “mass” states correspond to an unsterilelike and activelike mode. The unsterile mode features a complex pole or resonance for $0\le \eta <1/3$ with an “invisible width” which is the result of the decay of the unsterile mode into the active mode and the massless particles of the hidden conformal sector. For $\eta \ge 1/3$, the complex pole disappears, merging with the unparticle threshold. The active mode is described by a stable pole, but “inherits” a nonvanishing spectral density above the unparticle threshold as a consequence of the mixing. We find that the radiative decay width of the unsterile neutrino into the active neutrino (and a photon) via charged current loops, is suppressed by a factor $\sim [2{sin}^2({\theta }_0)\frac{M^2}{{\Lambda }^2}{]}^{\eta /(1-\eta )}$, where ${\theta }_0$ is the mixing angle for $\eta =0$, $M$ is approximately the mass of the unsterile neutrino, and $\Lambda \gg M$ is the unparticle scale. The suppression of the radiative (visible) decay width of the sterile neutrino weakens the bound on the mass and mixing angle from the x-ray or soft gamma-ray background.

Perturbative expansions of quantum field theories typically lead to ultraviolet (short-distance) divergences requiring regularization and renormalization. Many different regularization techniques have been developed over the years, but most regularizations require severe mutilation of the logical foundations of the theory. In contrast, breaking Lorentz invariance, while it is certainly a radical step, at least does not damage the logical foundations of the theory. I shall explore the features of a Lorentz symmetry breaking regulator in a simple polynomial scalar field theory and discuss its implications. In particular, I shall quantify just “how much” Lorentz symmetry breaking is required to fully regulate the quantum theory and render it finite. This scalar field theory provides a simple way of understanding many of the key features of Hořava’s recent article [Phys. Rev. D 79, 084008 (2009)] on $3+1$ dimensional quantum gravity.

We study numerically the effects of loop quantum gravity motivated corrections on massless scalar field collapse in Painlevé-Gullstrand coordinates. Near criticality the system exhibits Choptuik scaling with a mass gap and a new scaling relationship dependant upon the quantum length scale. Classical singularities are resolved by a radiationlike phase in the quantum collapse: the black hole consists of a compact region of spacetime bounded by a single, smooth trapping horizon. The “evaporation” is not complete but leaves behind a small expanding shell that disperses to infinity.

During the past century, there has been considerable discussion and analysis of the motion of a point charge in an external electromagnetic field in special relativity, taking into account “self-force” effects due to the particle’s own electromagnetic field. We analyze the issue of “particle motion” in classical electromagnetism in a rigorous and systematic way by considering a one-parameter family of solutions to the coupled Maxwell and matter equations corresponding to having a body whose charge-current density $J^a(\lambda )$ and stress-energy tensor $T_{ab}(\lambda )$ scale to zero size in an asymptotically self-similar manner about a worldline $\gamma$ as $\lambda \to 0$. In this limit, the charge, $q$, and total mass, $m$, of the body go to zero, and $q/m$ goes to a well-defined limit. The Maxwell field $F_{ab}(\lambda )$ is assumed to be the retarded solution associated with $J^a(\lambda )$ plus a homogeneous solution (the “external field”) that varies smoothly with $\lambda$. We prove that the worldline $\gamma$ must be a solution to the Lorentz force equations of motion in the external field $F_{ab}(\lambda =0)$. We then obtain self-force, dipole forces, and spin force as first-order perturbative corrections to the center-of-mass motion of the body. We believe that this is the first rigorous derivation of the complete first-order correction to Lorentz force motion. We also address the issue of obtaining a self-consistent perturbative equation of motion associated with our perturbative result, and argue that the self-force equations of motion that have previously been written down in conjunction with the “reduction of order” procedure should provide accurate equations of motion for a sufficiently small charged body with negligible dipole moments and spin. (There is no corresponding justification for the non-reduced-order equations.) We restrict consideration in this paper to classical electrodynamics in flat spacetime, but there should be no difficulty in extending our results to the motion of a charged body in an arbitrary globally hyperbolic curved spacetime.

We develop a five-dimensional model for electroweak physics based on a noncompact warped extra dimension of finite length, known as the soft wall scenario, where all the dynamical degrees of freedom propagate in the five-dimensional bulk. We solve the equations of motion and find the allowed spectra, showing that the mass of the lightest fermionic mode behaves as a power law of the effective four-dimensional Yukawa coupling constant, with the exponent being the corresponding fermionic five-dimensional bulk mass. Precisely this nonuniversal behavior allows us to reproduce the hierarchy between the standard model fermion masses (from neutrinos to the top quark) with nonhierarchical fermionic bulk masses.

During cosmological inflation, quasiclassical perturbations are permanently generated on super-Hubble spatial scales, their power spectrum being determined by the fundamental principles of quantum field theory. By the end of inflation, they serve as primeval seeds for structure formation in the universe. At early stages of inflation, such perturbations break homogeneity and isotropy of the inflationary background. In the present paper, we perturbatively take into account this quasiclassical background inhomogeneity of the inflationary universe while considering the evolution of small-scale (sub-Hubble) quantum modes. As a result, the power spectrum of primordial perturbations develops statistical anisotropy, which can subsequently manifest itself in the large-scale structure and cosmic microwave background. The statistically anisotropic contribution to the primordial power spectrum is predicted to have almost scale-invariant form dominated by a quadrupole. Theoretical expectation of the magnitude of this anisotropy depends on the assumptions about the physics in the trans-Planckian region of wave numbers.