We develop worldline numerical methods, which combine string-inspired with Monte Carlo techniques, for the computation of the vacuum polarization tensor in inhomogeneous background fields for scalar QED. The algorithm satisfies the Ward identity exactly and operates on the level of renormalized quantities. We use the algorithm to study for the first time light propagation in a spatially varying magnetic field. Whereas a local derivative expansion applies to the limit of small variations compared to the Compton wavelength, the case of a strongly varying field can be approximated by a derivative expansion for the averaged field. For rapidly varying fields, the vacuum-magnetic refractive indices can exhibit a nonmonotonic dependence on the local field strength. This behavior can provide a natural limit on the self-focussing property of the quantum vacuum.

We investigate quantum longitudinal rescaling of electrodynamics, transforming coordinates as $x^{0,3}\to \lambda x^{0,3}$ and $x^{1,2}\to x^{1,2}$, to one loop. We do this by an aspherical Wilsonian renormalization, which was applied earlier to pure Yang-Mills theory. We find the anomalous powers of $\lambda$ in the renormalized couplings. Our result is only valid for $\lambda \lesssim 1$, because perturbation theory breaks down for $\lambda \ll 1$.

A Kerr black hole with mass $M$ and angular momentum $J$ satisfies the extremality inequality $|J|\le M^2$. In the presence of matter and/or gravitational radiation, this bound needs to be reformulated in terms of local measurements of the mass and the angular momentum directly associated with the black hole. The isolated and dynamical horizon framework provides such quasilocal characterization of black hole mass and angular momentum. With this framework, it is possible in axisymmetry to reformulate the extremality limit as $|J|\le 2M_H^2$, with $M_H$ the irreducible mass of the black hole computed from its apparent horizon area and $J$ obtained using a rotational Killing vector field on the apparent horizon. The $|J|\le 2M_H^2$ condition is also equivalent to requiring a non-negative black hole surface gravity. We present numerical experiments of an accreting black hole that temporarily violates this extremality inequality. The initial configuration consists of a single, rotating black hole surrounded by a thick, shell cloud of negative energy density. For these numerical experiments, we introduce a new matter-without-matter evolution method.

We simplify and extend semiclassical methods in inflationary cosmology that capture leading IR corrections to correlators. Such IR effects can be absorbed into a coordinate change when examining sufficiently local observables, but not when comparing observations at large separation in scales, such as seen by a late-time observer. The analysis is facilitated by definition of a scale-dependent metric and physical momentum. These assist definition of “IR-safe” observables seen by a postinflationary observer, which are contrasted to those based on the local geometry of the reheating surface. For the former observables, the observer’s horizon provides an effective IR cutoff. IR growth of fluctuations contributes to enhanced statistical inhomogeneities/anisotropies at short scales, observation of which by a present-day observer might be sought in 21 cm measurements. Such IR corrections are argued to become large for a very late-time observer.

We examine the global structure of colliding domain walls in AdS spacetime and come to the conclusion that singularities forming from such collisions are of the big-crunch type rather than that of a black brane.

In this paper we discuss the possibility that chiral phase transitions, analogous to those of QCD, occur in the vicinity of a black hole. If the black hole is surrounded by a gas of strongly interacting particles, an inhomogeneous condensate will form. We demonstrate this by explicitly constructing self-consistent solutions for the condensate. We discuss the relevance of our results in relation to the possibility of chromosphere formation. We argue that this is not expected, rather the configuration will be similar to the shock produced by stellar wind.

A color-singlet neutral vector boson is considered as a possible common origin of the top forward-backward asymmetry and the CDF dijet resonance. We identify chiral and flavor structures of the couplings of this new vector boson to the standard model quarks for which one could accommodate both data. We also demonstrate that nonvanishing observables involving longitudinal top polarizations can provide useful criteria for the possible existence of parity violating new physics in the $q\overline{q}\to t\overline{t}$ process, and discrimination between the flavor-conserving and flavor-violating cases.

Neutrino-neutrino interactions in dense neutrino streams, like those emitted by a core-collapse supernova, can lead to self-induced neutrino flavor conversions. While this is a nonlinear phenomenon, the onset of these conversions can be examined through a standard stability analysis of the linearized equations of motion. The problem is reduced to a linear eigenvalue equation that involves the neutrino density, energy spectrum, angular distribution, and matter density. In the single-angle case, we reproduce previous results and use them to identify two generic instabilities: The system is stable above a cutoff density (“cutoff mode”), or can approach an asymptotic instability for increasing density (“saturation mode”). We analyze multiangle effects on these generic types of instabilities and find that even the saturation mode is suppressed at large densities. For both types of modes, a given multiangle spectrum typically is unstable when the neutrino and electron densities are comparable, but stable when the neutrino density is much smaller or much larger than the electron density. The role of an instability in the SN context depends on the available growth time and on the range of affected modes. At large matter density, most modes are off resonance even when the system is unstable.

A measurement of the differential cross section for the inclusive production of isolated prompt photons in proton-proton collisions at a center-of-mass energy of 7 TeV is presented. The data sample corresponds to an integrated luminosity of $36{\mathrm{pb}}^{-1}$ recorded by the CMS detector at the LHC. The measurement covers the pseudorapidity range $|\eta |<2.5$ and the transverse energy range $25<E_{\mathrm{T}}<400\mathrm{GeV}$, corresponding to the kinematic region $0.007<x_{\mathrm{T}}<0.114$. Photon candidates are identified with two complementary methods, one based on photon conversions in the silicon tracker and the other on isolated energy deposits in the electromagnetic calorimeter. The measured cross section is presented as a function of $E_{\mathrm{T}}$ in four pseudorapidity regions. The next-to-leading-order perturbative QCD calculations are consistent with the measured cross section.

We report on a search for the production of the Higgs boson decaying to two bottom quarks accompanied by two additional quarks. The data sample used corresponds to an integrated luminosity of approximately $4{\mathrm{fb}}^{-1}$ of $p\overline{p}$ collisions at $\sqrt{s}=1.96\mathrm{TeV}$ recorded by the CDF II experiment. This search includes twice the integrated luminosity of the previous published result, uses analysis techniques to distinguish jets originating from light flavor quarks and those from gluon radiation, and adds sensitivity to a Higgs boson produced by vector boson fusion. We find no evidence of the Higgs boson and place limits on the Higgs boson production cross section for Higgs boson masses between $100\mathrm{GeV}/c^2$ and $150\mathrm{GeV}/c^2$ at the 95% confidence level. For a Higgs boson mass of $120\mathrm{GeV}/c^2$, the observed (expected) limit is 10.5 (20.0) times the predicted standard model cross section.

The relation for transition form factors of $\eta$ and ${\eta }^{\prime }$ is obtained by combining the exact nonperturbative QCD sum rule, following from the dispersive representation of axial anomaly, and quark-hadron duality. It is valid at all virtual photon momenta and allows one to express the transition form factors entirely in terms of meson decay constants. This relation is in a good agreement with experimental data.

We introduce four families of nonunitary coset conformal field theories which generalize the Wess-Zumino-Witten models on the supergroups $\mathrm{PSU}(n|n)$ and $\mathrm{OSP}(2n+2|2n)$. We show that these coset theories admit perturbations which are marginal at 2 loops and we argue in favor of their exact marginality. Finally, we discuss the implications of our findings for the sigma models on symmetric superspaces, affine Toda and Gross-Neveu models which are believed to arise as certain limits of the coset theories.

We study the conditions an arbitrary flux configuration must fulfill in order to construct a 4d space-time of the type ${\mathrm{AdS}}_2\times S^2$ from a type IIB supergravity flux compactification in which Neveu-Schwarz-Neveu-Schwarz (NS-NS) fluxes are included. We present a solution consisting on a compactification in the presence of 3-form NS-NS andRamond-Ramond (RR) fluxes. The internal manifold is a $SU(3)$ structure six-dimensional manifold, with null curvature and with torsion. By preserving two supersymmetries in the four-dimensional low energy theory, we find a way to obtain the ${\mathrm{AdS}}_2\times S^2$ geometry as a near-horizon solution by compactification in non-Calabi-Yau manifolds.

We study the critical gravity in two-dimensional anti–de Sitter (${\mathrm{AdS}}_2$) spacetimes, which was obtained from the cosmological topologically massive gravity (${\mathrm{TMG}}_{\Lambda }$) in three dimensions by using the Kaluza-Klein dimensional reduction. We perform the perturbation analysis around ${\mathrm{AdS}}_2$, which may correspond to the near-horizon geometry of the extremal Banados, Teitelboim, and Zanelli (BTZ) black hole obtained from the ${\mathrm{TMG}}_{\Lambda }$ with identification upon uplifting three dimensions. A massive propagating scalar mode $\delta F$ satisfies the second-order differential equation away from the critical point of $K=l$, whose solution is given by the Bessel functions. On the other hand, $\delta F$ satisfies the fourth-order equation at the critical point. We exactly solve the fourth-order equation, and compare it with the log gravity in two dimensions. Consequently, the critical gravity in two dimensions could not be described by a massless scalar $\delta F_{\mathrm{ml}}$ and its logarithmic partner $\delta F_{\log }^{4\mathrm{th}}$.

In this paper we present a path integral formulation of stochastic inflation. Volume weighting can be naturally implemented from this new perspective in a very straightforward way when compared to conventional Langevin approaches. With an in-depth study of inflation in a quartic potential, we investigate how the inflaton evolves and how inflation typically ends both with and without volume weighting. The calculation can be carried to times beyond those accessible to conventional Fokker-Planck approaches. Perhaps unexpectedly, complex histories sometimes emerge with volume weighting. The reward for this excursion into the complex plane is an insight into how volume-weighted inflation both loses memory of initial conditions and ends via slow roll. The slow-roll end of inflation mitigates certain “Youngness Paradox”-type criticisms of the volume-weighted paradigm. Thus it is perhaps time to rehabilitate proper-time volume weighting as a viable measure for answering at least some interesting cosmological questions.

We present results for the strong widths corresponding to the ${\Sigma }_b\to {\Lambda }_b\pi$ and ${\Sigma }_b^{*}\to {\Lambda }_b\pi$ decays. We apply our model from Phys. Rev. D 72, 094022 (2005), where we previously studied the corresponding transitions in the charmed sector. Our nonrelativistic constituent quark model uses wave functions that take advantage of the constraints imposed by heavy quark symmetry. The partial conservation of axial current hypothesis allows us to determine the strong vertices from an analysis of the axial current matrix elements.

We examine the extent to which it is possible to realize the NMSSM “ideal Higgs” models espoused in several papers by Gunion et al. in the context of partially universal GUT scale boundary conditions. To this end we use the powerful methodology of nested sampling. We pay particular attention to whether ideal-Higgs-like points not only pass LEP constraints but are also acceptable in terms of the numerous constraints now available, including those from the Tevatron and $B$-factory data, $(g-2{)}_{\mu }$ and the relic density $\Omega h^2$. In general for this particular methodology and range of parameters chosen, very few points corresponding to said previous studies were found, and those that were found were at best $2\sigma$ away from the preferred relic density value. Instead, there exist a class of points, which combine a mostly singlet-like Higgs with a mostly singlino-like neutralino coannihilating with the lightest stau, that are able to effectively pass all implemented constraints in the region $80<m_h<100$. It seems that the spin-independent direct detection cross section acts as a key discriminator between ideal Higgs points and the hard to detect singlino-like points.