We present a class of spherically symmetric hypersurfaces in the Kruskal extension of the Schwarzschild space-time. The hypersurfaces have constant negative scalar curvature, so they are hyperboloidal in the regions of space-time which are asymptotically flat.

We construct some classes of electrically charged, static and spherically symmetric black hole solutions of the four-dimensional Einstein-Born-Infeld-dilaton gravity in the absence and presence of Liouville-type potential for the dilaton field and investigate their properties. These solutions are neither asymptotically flat nor (anti)-de Sitter. We show that in the presence of the Liouville-type potential, there exist two classes of solutions. We also compute temperature, entropy, charge and mass of the black hole solutions, and find that these quantities satisfy the first law of thermodynamics. We find that in order to fully satisfy all the field equations consistently, there must be a relation between the electric charge and other parameters of the system.

A calculation of the entropy of static, electrically charged, black holes with spherical, toroidal, and hyperbolic-compact and oriented horizons, in $D$ spacetime dimensions, is performed. These black holes live in an anti–de Sitter spacetime, i.e., a spacetime with negative cosmological constant. To find the entropy, the approach developed by Solodukhin is followed. The method consists in a redefinition of the variables in the metric, by considering the radial coordinate as a scalar field. Then one performs a $2+(D-2)$ dimensional reduction, where the ($D-2$) dimensions are in the angular coordinates, obtaining a 2-dimensional effective scalar field theory. This theory is a conformal theory in an infinitesimally small vicinity of the horizon. The corresponding conformal symmetry will then have conserved charges, associated with its infinitesimal conformal generators, which will generate a classical Poisson algebra of the Virasoro type. Shifting the charges and replacing Poisson brackets by commutators, one recovers the usual form of the Virasoro algebra, obtaining thus the level zero conserved charge eigenvalue $L_0$, and a nonzero central charge $c$. The entropy is then obtained via the Cardy formula.

Following Dirac’s brane variation prescription, the brane must not be deformed during the variation process, or else the linearity of the variation may be lost. Alternatively, the variation of the brane is done, in a special Dirac frame, by varying the bulk coordinate system itself. Imposing appropriate Dirac-style boundary conditions on the constrained “sandwiched” gravitational action, we show how Israel junction conditions get relaxed, but remarkably, all solutions of the original Israel equations are still respected. The Israel junction conditions are traded, in the $Z_2$-symmetric case, for a generalized Regge-Teitelboim type equation (plus a local conservation law), and in the generic $Z_2$-asymmetric case, for a pair of coupled Regge-Teitelboim equations. The Randall-Sundrum model and its derivatives, such as the Dvali-Gabadadze-Porrati and the Collins-Holdom models, get generalized accordingly. Furthermore, Randall-Sundrum and Regge-Teitelboim brane theories appear now to be two different faces of the one and the same unified brane theory. Within the framework of unified brane cosmology, we examine the dark matter/energy interpretation of the effective energy/momentum deviations from general relativity.

The mean spectrum and burst statistics of gravitational waves produced by a cosmological population of cosmic string loops are estimated using analytic approximations, calibrated with earlier simulations. Formulas are derived showing the dependence of observables on the string tension $G\mu$, in the regime where newly-formed loops are relatively large, not very much smaller than the horizon. Large loops form earlier, are more abundant, and generate a more intense stochastic background and more frequent bursts than assumed in earlier background estimates, enabling experiments to probe lighter cosmic strings of interest to string theory. Predictions are compared with instrument noise from current and future experiments, and with confusion noise from known astrophysical gravitational-wave sources such as stellar and massive black hole binaries. In these large-loop models, current data from millisecond pulsar timing already suggests that $G\mu$ is less than about ${10}^{-10}$, close to the minimum value where bursts might be detected by Advanced LIGO, and a typical value expected in strings from brane inflation. Because of confusion noise expected from massive black hole binaries, pulsar techniques will not be able to go below about $G\mu \approx {10}^{-11}$. LISA will be sensitive to stochastic backgrounds created by strings as light as $G\mu \approx {10}^{-15}$, at frequencies where it is limited by confusion noise of Galactic stellar populations; however, for those lightest detectable strings, bursts are rarely detectable. For $G\mu >{10}^{-11}$, the stochastic background from strings dominates the LISA noise by a large factor, and burst events may also be detectable by LISA, allowing detailed study of loop behavior. Astrophysical confusion might be low enough at 0.1 to 1 Hz to eventually reach $G\mu \approx {10}^{-20}$ with future interferometer technology.

We numerically investigate density perturbations generated in the smooth hybrid new inflation model, a kind of double inflation model that is designed to reproduce the running spectral index suggested by the WMAP results. We confirm that this model provides the running spectral index within $1\sigma$ range of the 3 yr WMAP result. In addition, we find a sharp and strong peak on the spectrum of primordial curvature perturbation at small scales. This originates from amplification of fluctuation in the first inflaton fields due to parametric resonance, which takes place in the oscillatory phase between two inflationary regime. Formation probability of primordial black holes (PBHs) is discussed as a consequence of such peak.

We cross correlate the new 3 year Wilkinson Microwave Anistropy Probe (WMAP) cosmic microwave background data with the NRAO VLA Sky Survey radio galaxy data and find further evidence of late integrated Sachs-Wolfe (ISW) effect taking place at late times in cosmic history. Our detection makes use of a novel statistical method (P. Baldi, G. Kerkyacharian, D. Marinucci, and D. Picard, math.ST/0606154 and P. Baldi, G. Kerkyacharian, D. Marinucci, D. Picard, math.ST/0606599) based on a new construction of spherical wavelets, called needlets. The null hypothesis (no ISW) is excluded at more than 99.7% confidence. When we compare the measured cross correlation with the theoretical predictions of standard, flat cosmological models with a generalized dark energy component parameterized by its density, ${\Omega }_{\mathrm{DE}}$, equation of state $w$ and speed of sound $c_s^2$, we find $0.3\le {\Omega }_{\mathrm{DE}}\le 0.8$ at 95% C.L., independently of $c_s^2$ and $w$. If dark energy is assumed to be a cosmological constant ($w=-1$), the bound on density shrinks to $0.41\le {\Omega }_{\mathrm{DE}}\le 0.79$. Models without dark energy are excluded at more than $4\sigma$. The bounds on $w$ depend rather strongly on the assumed value of $c_s^2$. We find that models with more negative equation of state (such as phantom models) are a worse fit to the data in the case $c_s^2=1$ than in the case $c_s^2=0$.

Superfields provide a compact description of supersymmetry representations. Loop corrections with superfield formalism are simpler and much more manageable than the calculation in terms of component fields. In this paper we calculate the contribution of the Kaluza-Klein (KK) states, associated with extra dimensions, to the renormalization group beta function. These Kaluza-Klein particles circulate in the virtual loop, hence affecting the overall corrections at any order. We obtain the one-loop correction, which checks with the result previously obtained using the more laborious component field method. In addition, we calculate the two-loop correction coming from chiral KK states.

We calculate the new physics contributions to the rare semileptonic decay $B\to X_s{l}^{+}{l}^{-}$ $(l=e,\mu )$ induced by the charged-Higgs loop diagrams appeared in the top quark two-Higgs doublet model (T2HDM). Within the considered parameter space, we found that (a) the effective Wilson coefficients ${\tilde{C}}_i^{\mathrm{eff}}(m_b)$ ($i=7\gamma$, $9V$ and $10A$) in the T2HDM are always standard model-like; (b) the new physics contributions to ${\tilde{C}}_{7\gamma }^{\mathrm{eff}}$ and ${\tilde{C}}_{9V}^{\mathrm{eff}}$ can be significant in magnitude, but they tend to cancel each other; and (c) the T2HDM predictions for $\mathrm{Br}(B\to X_s{l}^{+}{l}^{-})$ agree well with the measured value within 1 standard deviation.

We consider extra dimensional field theory descriptions of backgrounds with $N$ different throats where one of the extra dimensions in each throat is much larger than the others. Such backgrounds can be described by field theory on $N$ 5D warped spaces which intersect on a ultraviolet (UV) brane. Given a field that propagates in all $N$ throats there are $N$ boundary conditions on the UV brane (which are determined by the effective Lagrangian on the UV brane) in addition to the boundary conditions on the $N$ infrared branes. We derive a general set of UV boundary conditions and give examples of how they are applied to particular situations. Three simple example applications are given: in the first the number of families is determined by the number of throats and the SUSY flavor problem is solved via an $S_3$ symmetry of the throats; in the second we embed this scenario in a SUSY GUT with a solution of the doublet-triplet splitting problem based on the product group approach; while in the final example we show a simple geometric implementation of a SUSY trinification model on three throats.

This is the second of a pair of articles on scattering of glue by glue, in which we give the light-cone gauge calculation of the one-loop on-shell helicity conserving scattering amplitudes for gluon-gluon scattering (neglecting quark loops). The $1/p^{+}$ factors in the gluon propagator are regulated by replacing $p^{+}$ integrals with discretized sums omitting the $p^{+}=0$ terms in each sum. We also employ a novel ultraviolet regulator that is convenient for the light-cone worldsheet description of planar Feynman diagrams. The helicity conserving scattering amplitudes are divergent in the infrared. The infrared divergences in the elastic one-loop amplitude are shown to cancel, in their contribution to cross sections, against ones in the cross section for unseen bremsstrahlung gluons. We include here the explicit calculation of the latter, because it assumes an unfamiliar form due to the peculiar way discretization of $p^{+}$ regulates infrared divergences. In resolving the infrared divergences we employ a covariant definition of jets, which allows a transparent demonstration of the Lorentz invariance of our final results. Because we use an explicit cutoff of the ultraviolet divergences in exactly four spacetime dimensions, we must introduce explicit counterterms to achieve this final covariant result. These counterterms are polynomials in the external momenta of the precise order dictated by power counting. We discuss the modifications they entail for the light-cone worldsheet action that reproduces the bare planar diagrams of the gluonic sector of QCD. The simplest way to do this is to interpret the QCD string as moving in six spacetime dimensions.

We apply the formalism of quantum cosmology to models containing a phantom field. Three models are discussed explicitly: a toy model, a model with an exponential phantom potential, and a model with phantom field accompanied by a negative cosmological constant. In all these cases we calculate the classical trajectories in configuration space and give solutions to the Wheeler-DeWitt equation in quantum cosmology. In the cases of the toy model and the model with exponential potential we are able to solve the Wheeler-DeWitt equation exactly. For comparison, we also give the corresponding solutions for an ordinary scalar field. We discuss, in particular, the behavior of wave packets in minisuperspace. For the phantom field these packets disperse in the region that corresponds to the big-rip singularity. This thus constitutes a genuine quantum region at large scales, described by a regular solution of the Wheeler-DeWitt equation. For the ordinary scalar field, the big-bang singularity is avoided. Some remarks on the arrow of time in phantom models as well as on the relation of phantom models to loop quantum cosmology are given.

The relation between generalized parton distributions (GPDs) and color transparency is explored. Computing the effective size of a hadron yields equations that relate the potential observation of color transparency with specific features of the GPD and the related form factor. Measurement of the effective size allows one to distinguish between different GPDs that yield the same form factor, and therefore provides a further test of any model of the pion form factor. It is also true that the discovery of color transparency in pionic diffractive dissociation reactions gives specific predictions for the behavior of the pion generalized parton distribution, and allows us to rule out some models.

Supersymmetry breaking by constant (field independent) superpotentials localized at boundaries is studied in a supersymmetric warped space model. We calculate the Kaluza-Klein mass spectrum of the hypermultiplet. We take into account of the radion and the compensator supermultiplets, as well as the bulk mass $c$ for the hypermultiplet. The mass splitting is similar to that of the Scherk-Schwarz supersymmetry breaking (in flat space) for large $|c|$, and has an interesting dependence on the bulk mass parameter $c$. We show that the radius is stabilized by the presence of the constant boundary superpotentials.

We present a new method for the evaluation of the perturbative expansion of the QCD pressure which is valid at all values of the temperature and quark chemical potentials in the deconfined phase and which we work out up to and including order $g^4$ accuracy. Our calculation is manifestly four-dimensional and purely diagrammatic—and thus independent of any effective theory descriptions of high temperature or high density QCD. In various limits, we recover the known results of dimensional reduction and the hard dense/thermal loop (HDL/HTL) resummation schemes, as well as the equation of state of zero-temperature quark matter, thereby verifying their respective validity. To demonstrate the overlap of the various regimes, we furthermore show how the predictions of dimensional reduction and HDL resummed perturbation theory agree in the regime $T\sim \sqrt{g}\mu$. At parametrically smaller temperatures $T\sim g\mu$, we find that the dimensional reduction result agrees well with those of the nonstatic resummations down to the remarkably low value $T\approx 0.2m_{\mathrm{D}}$, where $m_{\mathrm{D}}$ is the Debye mass at $T=0$. Beyond this, we see that only the latter methods connect smoothly to the $T=0$ result of Freedman and McLerran, to which the leading small-$T$ corrections are given by the so-called non-Fermi-liquid terms, first obtained through HDL resummations. Finally, we outline the extension of our method to the next order, where it would include terms for the low-temperature entropy and specific heats that are unknown at present.

The stress-energy tensor for the classical nonminimally coupled scalar field is known not to satisfy the pointwise energy conditions of general relativity. In this paper we show, however, that local averages of the classical stress-energy tensor satisfy certain inequalities. We give bounds for averages along causal geodesics and show, e.g., that in Ricci-flat background spacetimes, ANEC and AWEC are satisfied. Furthermore we use our result to show that in the classical situation we have an analogue to the phenomenon of quantum interest. These results lay the foundations for analogous energy inequalities for the quantized nonminimally coupled fields, which will be discussed elsewhere.

We consider colliding wave packets consisting of hybrid mixtures of electromagnetic, gravitational, and scalar waves. Irrespective of the scalar field, the electromagnetic wave still reflects from the gravitational wave. Some reflection processes are given for different choice of packets in which the Coulomb-like component ${\Psi }_2$ vanishes. Exact solution for multiple reflection of an electromagnetic wave from successive impulsive gravitational waves is obtained in a closed form. It is shown that a successive sign flip in the Maxwell spinor arises as a result of encountering with an impulsive train (i.e. the Dirac’s comb curvature) of gravitational waves. Such an observable effect may be helpful in the detection of gravitational wave bursts.

Any one-field inflation is actually realized in a multifield configuration because the inflaton must have couplings with other fields to reheat the universe and is coupled to all other fields at least gravitationally. In all single inflaton models, it is explicitly or implicitly assumed that the heavier fields are stuck to their potential minima during inflation, which are time-dependent in general. We present a formalism to calculate curvature perturbations in such a time-dependent background and show that the proper expression can be obtained using a single-field analysis with a reduced potential in which all these heavy fields are situated at their respective, time-dependent minima. Our results provide a firm ground on the conventional calculation.

In the first part of this work we discuss possible effects of stochastic space-time foam configurations of quantum gravity on the propagation of “flavored” (Klein-Gordon and Dirac) neutral particles, such as neutral mesons and neutrinos. The formalism is not the usually assumed Lindblad one, but it is based on random averages of quantum fluctuations of space-time metrics over which the propagation of the matter particles is considered. We arrive at expressions for the respective oscillation probabilities between flavors which are quite distinct from the ones pertaining to Lindblad-type decoherence, including in addition to the (expected) Gaussian decay with time, a modification to oscillation behavior, as well as a power-law cutoff of the time-profile of the respective probability. In the second part we consider space-time foam configurations of quantum-fluctuating charged-black holes as a way of generating (parts of) neutrino mass differences, mimicking appropriately the celebrated Mikheyev-Smirnov-Wolfenstein (MSW) effects of neutrinos in stochastically fluctuating random media. We pay particular attention to disentangling genuine quantum-gravity effects from ordinary effects due to the propagation of a neutrino through ordinary matter. Our results are of interest to precision tests of quantum-gravity models using neutrinos as probes.