We study the observability for a heavy Majorana neutrino $N$ along with a new charged gauge boson $W^{\prime }$ at the LHC. We emphasize the complementarity of these two particles in their production and decay to unambiguously determine their properties. We show that the Majorana nature of $N$ can be verified by the lepton number violating like-sign dilepton process, and by polar and azimuthal angular distributions. The chirality of the $W^{\prime }$ coupling to leptons and to quarks can be determined by a polar angle distribution in the reconstructed frame and an azimuthal angle distribution.

We show that the smooth hybrid inflation is naturally realized in a framework of a supersymmetric axion model. Identifying the Peccei-Quinn scalar fields as a part of the inflaton sector, successful inflation takes place reproducing the amplitude and spectral index of the curvature perturbation observed by WMAP. A relatively large axion isocurvature perturbation and its non-Gaussianity are predicted in our model. The saxion coherent oscillation has a large amplitude and dominates the Universe. The subsequent decay of the saxion produces a huge amount of entropy, which dilutes unwanted relics. Winos, the lightest supersymmetric particles in this scenario, are produced nonthermally in the decay and account for dark matter.

We present a new observable, $\Delta \varphi$, an azimuthal angle difference between $t$ and $\overline{t}$ quarks in $t\overline{t}$ pair production at hadron colliders as an interesting probe of the radiative quantum chromodynamics process as well as a high-order correction in the high-mass regime. This variable also enables good discrimination on some new physics models that may explain the forward-backward charge asymmetry of $t\overline{t}$ production measured at the Tevatron. With a reliable estimation of the data set obtained up to 2011 at the Tevatron and Large Hadron Collider, we present an opportunity for testing the standard model as well as searching new physics models with the $\Delta \varphi$ observable in the $\mathrm{\text{lepton}}+\mathrm{\text{jets}}$ decay channel.

Recent advances in our understanding of tree-level QCD amplitudes in the massless limit exploiting an effective (maximal) supersymmetry have led to the complete analytic construction of tree amplitudes with up to four external quark-antiquark pairs. In this work we compare the numerical efficiency of evaluating these closed analytic formulas to a numerically efficient implementation of the Berends-Giele recursion. We compare calculation times for color-ordered tree amplitudes with parton numbers ranging from 4 to 25 with no, one, two, and three external quark lines. We find that the analytic results are generally faster in the case of maximally helicity-violating and next-to-maximally helicity-violating amplitudes. Starting with the next-to-next-to-maximally helicity-violating amplitudes the Berends-Giele recursion becomes more efficient. In addition to the runtime we also compare the numerical accuracy. The analytic formulas are on average more accurate than the off-shell recursion relations, though both are well-suited for complicated phenomenological applications. In both cases we observe a reduction in the average accuracy when phase-space configurations close to singular regions are evaluated. In summary, our findings show that for up to nine gluons the closed analytic formulas perform best.

Recently, Herdeiro et al. [Phys. Rev. D 84, 124048 (2011)] have established that solutions of Einstein’s gravity admitting foliations with a certain geometric condition are also solutions of $n$-DBI gravity, Herdeiro and Hirano [J. Cosmol. Astropart. Phys. 05 (2012) 031]. Here we observe that, in vacuum, the required geometric condition is fulfilled by the well known maximal slicing, often used in numerical relativity. As a corollary, we establish that the Kerr geometry is a solution of $n$-DBI gravity in the foliation adapted to Boyer-Lindquist coordinates.

We generalize previous work by considering a novel gravitational model with an action given by an arbitrary function of the Ricci scalar, the matter Lagrangian density, a scalar field and a kinetic term constructed from the gradients of the scalar field, respectively. The gravitational field equations in the metric formalism are obtained, as well as the equations of motion for test particles, which follow from the covariant divergence of the stress-energy tensor. Specific models with a nonminimal coupling between the scalar field and the matter Lagrangian are further explored. We emphasize that these models are extremely useful for describing an interaction between dark energy and dark matter, and for explaining the late-time cosmic acceleration.

In this short note we use holographic methods to study the response of quantum critical points with hyperscaling violation to a disturbance caused by a massive charged particle. We give analytical expressions for the two-point functions of the fluctuations of the massive probe as a function of arbitrary (allowed) values of the hyperscaling violation exponent $\theta$ and the dynamical exponent $z$. We point out the existence of markedly different behaviors of the two-point functions in the parameter space of $\theta$ and $z$ at late times. In particular, as expected, the late-time dynamics of the probe becomes independent of its inertial mass in the range $z+2\theta /d>2$.

We construct a simple class of compactified five-dimensional metrics which admits closed timelike curves (CTCs), and derive the resulting CTCs as analytic solutions to the geodesic equations of motion. The associated Einstein tensor satisfies all the null, weak, strong and dominant energy conditions. In particular, no negative-energy “tachyonic” matter is required. In extra-dimensional models where gauge charges are bound to our brane, it is the Kaluza-Klein modes of gauge singlets that may travel through the CTCs. From our brane point of view, many of these Kaluza-Klein modes would appear to travel backward in time. We give a simple model in which time-traveling Higgs singlets can be produced by the LHC, either from decay of the Standard Model Higgs or through mixing with the Standard Model Higgs. The signature of these time-traveling singlets is a secondary decay vertex preappearing before the primary vertex which produced them. The two vertices are correlated by momentum conservation. We demonstrate that preappearing vertices in the Higgs singlet-doublet mixing model may well be observable at the LHC.

The quantum charged rigid membrane model, which is a higher derivative theory, has been considered to explore its gauge symmetries using a recently developed first order formalism [R. Banerjee et al., J. High Energy Phys. 08 (2011) 085]. Hamiltonian analysis has been performed and the gauge symmetry of the model is identified as reparametrization symmetry. First class constraints are shown to have a truncated Virasoro algebraic structure. An exact correspondence between the higher derivative theory and the first order formalism has been shown from the point of view of equations of motion.

We investigate some aspects of the renormalization group flow of gravity in the presence of fermions, which have remained somewhat puzzling so far. The first is the sign of the fermionic contribution to the running of Newton’s constant, which depends on details of the cutoff. We argue that only one of the previously used schemes correctly implements the cutoff on eigenvalues of the Dirac operator, and it acts in the sense of screening Newton’s constant. We also show that Kähler fermions give the same contribution to the running of the cosmological and Newton constant as four Dirac spinors. We then calculate the graviton contributions to the beta functions by imposing the cutoffs on the irreducible spin components of the tetrad. In this way we can probe the gauge dependence of the off-shell flow. The results resemble closely those of the metric formalism, except for an increased scheme—and (off shell) gauge dependence.

In this paper, we study the phase structure and equilibrium state space geometry of charged topological Gauss-Bonnet black holes in $d$-dimensional anti–de Sitter spacetime. Several critical points are obtained in the canonical ensemble, and the critical phenomena and critical exponents near them are examined. We find that the phase structures and critical phenomena drastically depend on the cosmological constant $\Lambda$ and dimensionality $d$. The result also shows that there exists an analogy between the black hole and the van der Waals liquid gas system. Moreover, we explore the phase transition and possible property of the microstructure using the state space geometry. It is found that the Ruppeiner curvature diverges exactly at the points where the heat capacity at constant charge of the black hole diverges. This black hole is also found to be a multiple system, i.e., it is similar to the ideal gas of fermions in some range of the parameters, while to the ideal gas of bosons in another range.

We study the Fock quantization of scalar fields of Klein-Gordon type in nonstationary scenarios propagating in spacetimes with compact spatial sections, allowing for different field descriptions that are related by means of certain nonlocal linear canonical transformations that depend on time. More specifically, we consider transformations that do not mix eigenmodes of the Laplace-Beltrami operator, which are supposed to be dynamically decoupled. In addition, we assume that the canonical transformations admit an asymptotic expansion for large eigenvalues (in norm) of the Laplace-Beltrami operator in the form of a series of half integer powers. Canonical transformations of this kind are found in the study of scalar perturbations in inflationary cosmologies, relating, for instance, the physical degrees of freedom of these perturbations after gauge fixing with gauge-invariant canonical pairs of Bardeen quantities. We characterize all possible transformations of this type and show that, independently of the initial field description, the combined criterion of requiring (i) invariance of the vacuum under the spatial symmetries and (ii) a unitary implementation of the dynamics leads to a unique equivalence class of Fock quantizations, all of them related by unitary transformations. This conclusion provides even further robustness to the validity of the proposed criterion, completing the results that have already appeared in the literature about the uniqueness of the Fock quantization under changes of field description when one permits exclusively local time-dependent canonical transformations that scale the field configuration.

We address the issue of constraining the class of $f(\mathcal{R})$ gravity able to reproduce the observed cosmological acceleration, by using the so-called cosmography of the Universe. We consider a model independent procedure to build up a $f(z)$ series in terms of the measurable cosmographic coefficients; we therefore derive cosmological late time bounds on $f(z)$ and its derivatives up to the fourth order, by fitting the luminosity distance directly in terms of such coefficients. We perform a Monte Carlo analysis, by using three different statistical sets of cosmographic coefficients, in which the only assumptions are the validity of the cosmological principle and that the class of $f(\mathcal{R})$ gravity reduces to $\Lambda \mathrm{CDM}$ when $z\ll 1$. We use the updated union 2.1 for supernovae Ia, the constraint on the $H_0$ value imposed by the measurements of the Hubble space telescope and the Hubble data set, with measures of $H$ at different $z$. We find a statistically good agreement of the $f(\mathcal{R})$ class under examination with the cosmological data; we thus propose a candidate for $f(\mathcal{R})$ gravity, which is able to pass our cosmological test, reproducing the late time acceleration in agreement with observations.

We generalize our first analysis of the wave equation for a massive vector boson in the background of a $D$-dimensional Schwarzschild black hole [C. Herdeiro, M. O. P. Sampaio, and M. Wang, Phys. Rev. D 85, 024005 (2012)], by adding charge to both the field and the black hole, on the ($3+1$)-dimensional Standard Model brane. A detailed numerical study is performed to obtain the transmission factor for the coupled (as well as decoupled) system of equations describing the Proca field modes, varying the angular momentum number, mass, charge, and space-time dimensions. A qualitatively new feature arising from the introduction of charge is the appearance of superradiant modes, which we investigate. We then compute the Hawking fluxes and analyze the effect of the charge. In particular, we observe an inverted charge splitting effect for small energies and for two or more extra dimensions. For neutral fields, we compare the emission of massive particles with spins up to one and also compare the Proca bulk-to-brane ratio of energy emission, showing that, as for a scalar field, most of the energy is emitted on the brane.

We present a relativistic model describing a thin disk surrounded by a halo in the presence of an electromagnetic field. The model is obtained by solving the Einstein-Maxwell equations on a particular conformastatic spacetime background and by using the distributional approach for the energy-momentum tensor. A class of solutions is obtained in which the gravitational and electromagnetic potentials are completely determined by a harmonic function only. A particular solution is given that is asymptotically flat and singularity free, and satisfies all the energy conditions.

We calculate the gravitational waveform for spinning, precessing compact binary inspirals through second post-Newtonian order in the amplitude. When spins are collinear with the orbital angular momentum and the orbits are quasicircular, we further provide explicit expressions for the gravitational-wave polarizations and the decomposition into spin-weighted spherical-harmonic modes. Knowledge of the second post-Newtonian spin terms in the waveform could be used to improve the physical content of analytical templates for data analysis of compact binary inspirals and for more accurate comparisons with numerical-relativity simulations.

Matched filtering for the identification of compact object mergers in gravitational wave antenna data involves the comparison of the data stream to a bank of template gravitational waveforms. Typically the template bank is constructed from phenomenological waveform models, since these can be evaluated for an arbitrary choice of physical parameters. Recently it has been proposed that singular value decomposition (SVD) can be used to reduce the number of templates required for detection. As we show here, another benefit of SVD is its removal of biases from the phenomenological templates along with a corresponding improvement in their ability to represent waveform signals obtained from numerical relativity (NR) simulations. Using these ideas, we present a method that calibrates a reduced SVD basis of phenomenological waveforms against NR waveforms in order to construct a new waveform approximant with improved accuracy and faithfulness compared to the original phenomenological model. The new waveform family is given numerically through the interpolation of the projection coefficients of NR waveforms expanded onto the reduced basis and provides a generalized scheme for enhancing phenomenological models.

In this paper we investigate a steady accretion within the Einstein-Straus vacuole, in the presence of the cosmological constant. The dark energy damps the mass accretion rate and—above a certain limit—completely stops the steady accretion onto black holes, which, in particular, is prohibited in the inflation era and after (roughly) ${10}^{12}$ years from the big bang (assuming the presently known value of the cosmological constant). Steady accretion would not exist in the late phases of the Penrose’s scenario—known as the Weyl curvature hypothesis—of the evolution of the Universe.

Information about the collapsed matter in a black hole will be lost if Hawking radiations are truly thermal. Recent studies discover that information can be transmitted from a black hole by Hawking radiations, due to their spectrum deviating from exact thermality when backreaction is considered. In this paper, we focus on the spectroscopic features of Hawking radiation from a Schwarzschild black hole, contrasting the differences between the nonthermal and thermal spectra. Of great interest, we find that the energy covariances of Hawking radiations for the thermal spectrum are exactly zero, while the energy covariances are nontrivial for the nonthermal spectrum. Consequently, the nonthermal spectrum can be distinguished from the thermal one by counting the energy covariances of successive emissions, which provides an avenue towards experimentally testing the long-standing “information loss paradox.”

Inflation models can have an early phase of inflation where the evolution of the inflaton is driven by quantum fluctuations before entering the phase driven by the slope of the scalar field potential. For a Coleman-Weinberg potential this quantum phase lasts ${10}^{7–8}$ e-foldings. A long period of fluctuation driven growth of the inflation field can possibly take the inflaton past ${\varphi }_{*}$, the value of the field where our current horizon scale crosses the horizon; alternatively, even if the field does not cross ${\varphi }_{*}$, the inflaton could have high kinetic energy at the end of this phase. Therefore, we study these issues in the context of different models of inflation. In scenarios where cosmological relevant scales leave during the quantum phase, we obtain large curvature perturbations of $O(10)$. We also apply our results to quadratic curvaton models and to quintessence models. In curvaton models we find that inflation must last longer than required to solve the horizon problem, that the curvaton models are incompatible with small field inflation models, and that there may be too large non-Gaussianity. A new phase of thermal fluctuation driven inflation is proposed, in which during inflation the inflaton evolution is governed by fluctuations from a sustained thermal radiation bath rather than by a scalar field potential.