The boundary behavior of amplitudes—the amplitudes’ behavior under a large Britto-Cachazo-Feng-Witten (BCFW) momenta deformation for a pair of legs—in Yang-Mills theory is of great interest recently. In this article we analyze the boundary behavior of off-shell Yang-Mills amplitudes in Feynman gauge. The deformed legs can be either adjacent or nonadjacent. We find that a set of reduced vertices can be used to simplify the analysis and calculation of the boundary behavior of amplitudes. Boundary behavior for amplitudes with adjacent BCFW deformation is read off from the reduced vertices. Then we discover a relationship between a permutation sum with fixed color ordering of the legs and the improved boundary behavior for the off-shell amplitudes with a nonadjacent BCFW momenta deformation. Based on the boundary behavior, we generalize the BCFW recursion relation to calculate general tree-level off-shell amplitudes and analyze the relations between them.

We study inflation, perturbations, non-Gaussianity, and late-time cosmological dynamics of a tachyon field both minimally and nonminimally coupled to gravity. By analyzing the parameter space of the model, the viability of the model in confrontation with recent observational data is considered. In a dynamical system technique, we study the phase space dynamics of both a minimally and nonminimally coupled tachyon field. We find the fixed points (lines in our setup) and explore their stability. Also, we perform a statefinder diagnostic to both cases and show that the trajectories of the statefinder pairs reach a stable state which corresponds to a Lambda cold dark matter scenario.

Constraints on the nonstandard top-gluon couplings composed of the chromomagnetic- and chromoelectric-dipole moments of the top quark are updated by combining the latest data of top-pair productions from the Tevatron, 7-TeV LHC, and 8-TeV LHC. We find that adding the recent 8-TeV data to the analysis is effective to get a stronger constraint on the chromoelectric-dipole moment than the one from the Tevatron and 7-TeV LHC alone. We also discuss how those constraints on the nonstandard couplings could be further improved when the 14-TeV LHC results become available in the near future.

In this paper we present for the first time a detailed Monte Carlo study of measuring $W^{\pm }Z\gamma$ production with pure leptonic decays and probing anomalous quartic gauge-boson $WWZ\gamma$ couplings at the $\sqrt{s}=14\mathrm{TeV}$ LHC, with parton shower and detector simulation effects taken into account. We find that with an integrated luminosity of $100{\mathrm{fb}}^{-1}$ and proper selection cuts, the Standard Model $W^{\pm }Z\gamma$ signal significance can be improved to as much as $3\sigma$. After reviewing previous parametrizations on anomalous $WWZ\gamma$ couplings [see e.g. $a_n/{\Lambda }^2$ or $k_2^m/{\Lambda }^2$ as shown in Belanger et al. Eur. Phys. J. C 13, 283 (2000)], we propose a more general parametrization scheme with four free inputs leading only to genuine $WWZ\gamma$ aQGC couplings. Finally, our numerical results show that one can reaches constraints at 95% confidence level of $-5.7\times {10}^{-5}{\mathrm{GeV}}^{-2}<k_2^m/{\Lambda }^2<5.5\times {10}^{-5}{\mathrm{GeV}}^{-2}$ and $-2.2\times {10}^{-5}{\mathrm{GeV}}^{-2}<a_n/{\Lambda }^2<2.4\times {10}^{-5}{\mathrm{GeV}}^{-2}$, which are more stringent than LEP’s results by three orders of magnitude.

The method of ratios was applied to search for geometrical scaling in charm production in deep inelastic scattering. Recent combined data from the H1 and ZEUS experiments were used. Two forms of geometrical scaling were tested: an originally proposed scaling that results from the Golec-Biernat-Wusthoff model and scaling motivated by a dipole representation, which takes into account charm mass. It turns out that in both cases some residual scaling is present and charm mass inclusion improves scaling quality.

We have constructed numerically non-Abelian vortices in an $SU(2)$ Chern-Simons-Higgs theory with a quartic Higgs potential. We have analyzed these solutions in detail by means of improved numerical codes and found some unexpected features we did not find when a sixth-order Higgs potential was used. The generic non-Abelian solutions have been generated by using their corresponding Abelian counterparts as initial guess. Typically, the energy of the non-Abelian solutions is lower than that of the corresponding Abelian one (except in certain regions of the parameter space). Regarding the angular momentum, the Abelian solutions possess the maximal value, although there exist non-Abelian solutions which reach that maximal value too. In order to classify the solutions it is useful to consider the non-Abelian solutions with asymptotically vanishing $A_t$ component of the gauge potential, which may be labeled by an integer number $m$. For vortex number $n=3$ and above, we have found uniqueness violation: two different non-Abelian solutions with all the global charges equal. Finally, we have investigated the limit of infinite Higgs self-coupling parameter and found a piecewise Regge-like relation between the energy and the angular momentum.

We calculate the leading radiative corrections to the axial current in the chiral separation effect in dense QED in a magnetic field. Contrary to the conventional wisdom suggesting that the axial current should be exactly fixed by the chiral anomaly relation and is described by the topological contribution on the lowest Landau level in the free theory, we find in fact that the axial current receives nontrivial radiative corrections. The direct calculations performed to the linear order in the external magnetic field show that the nontrivial radiative corrections to the axial current are provided by the Fermi surface singularity in the fermion propagator at nonzero fermion density.

We construct the duality-symmetric actions for a large class of six-dimensional models describing hierarchies of non-Abelian scalar, vector and tensor fields related to one another by first-order (self-)duality equations that follow from these actions. In particular, this construction provides a Lorentz invariant action for non-Abelian self-dual tensor fields. The class of models includes the bosonic sectors of the $6d$ (1,0) superconformal models of interacting non-Abelian self-dual tensor, vector, and hypermultiplets.

Particle production due to a quantized, massless, minimally coupled scalar field in two-dimensional flat spacetime with an accelerating mirror is investigated, with a focus on the time dependence of the process. We analyze first the classes of trajectories previously investigated by Carlitz and Willey and by Walker and Davies. We then analyze four new classes of trajectories, all of which can be expressed analytically and for which several ancillary properties can be derived analytically. The time dependence is investigated through the use of wave packets for the modes of the quantized field that are in the out vacuum state. It is shown for most of the trajectories studied that good time resolution of the particle production process can be obtained.

The presence of noncyclic geometric invariant is revealed in all the phenomena where particle generation from vacuum or vacuum condensates appear. Aharonov-Anandan invariants then can help to study such systems and can represent a new tool to be used in order to provide laboratory evidence of phenomena particulary hard to be detected, such as Hawking and Unruh effects and some features of quantum field theory in curved space simulated by some graphene morphologies. It is finally suggested that a very precise quantum thermometer can be built by exploiting geometric invariants properties.

We propose an expression for the entropy density associated with the local causal horizons in any diffeomorphism-invariant theory of gravity. If the black-hole entropy of the theory satisfies the physical process version of the first law of thermodynamics, then our proposed entropy satisfies the Clausius relation. Thus, our study shows that the thermodynamic nature of the spacetime horizons is not restricted to the black holes; it also applies to the local causal horizons in the neighborhood of any point in the spacetime.

Coalescing compact binary systems consisting of neutron stars and/or black holes should be detectable with upcoming advanced gravitational-wave detectors such as LIGO, Virgo, GEO and KAGRA. Gravitational-wave experiments to date have been riddled with non-Gaussian, nonstationary noise that makes it challenging to ascertain the significance of an event. A popular method to estimate significance is to time shift the events collected between detectors in order to establish a false coincidence rate. Here we propose a method for estimating the false alarm probability of events using variables commonly available to search candidates that does not rely on explicitly time shifting the events while still capturing the non-Gaussianity of the data. We present a method for establishing a statistical detection of events in the case where several silver-plated ($3–5\sigma$) events exist but not necessarily any gold-plated ($>5\sigma$) events. We use LIGO data and a simulated, realistic, blind signal population to test our method.

In the two-dimensional framework, the surface gravity of a (classical) black hole is independent of its mass $M$. As a consequence, the Hawking temperature and outflux are also independent of $M$ at the large-$M$ limit. (This contrasts with the four-dimensional framework, in which the surface gravity and temperature scale as $1/M$.) However, when the semiclassical backreaction effects on the black-hole geometry are taken into account, the surface gravity is no longer $M$ independent, and the same applies to the Hawking temperature and outflux. This effect, which vanishes at the large-$M$ limit, increases with decreasing $M$. Here we analyze the semiclassical field equations for a two-dimensional static black hole, and calculate the leading-order backreaction effect ($\propto 1/M$) on the Hawking temperature and outflux. We then confirm our analytical result by numerically integrating the semiclassical field equations.

We study cosmological perturbations around self-accelerating solutions to two extensions of nonlinear massive gravity: the quasi-dilaton theory and the mass-varying theory. We examine stability of the cosmological solutions, and the extent to which the vanishing of the kinetic terms for scalar and vector perturbations of self-accelerating solutions in massive gravity is generic when the theory is extended. We find that these kinetic terms are in general nonvanishing in both extensions, though there are constraints on the parameters and background evolution from demanding that they have the correct sign. In particular, the self-accelerating solutions of the quasi-dilaton theory are always unstable to scalar perturbations with wavelength shorter than the Hubble length.

We examine the evolution of a closed, homogeneous and anisotropic cosmology subject to a variation of the fine structure “constant” $\alpha$ within the context of the theory introduced by Bekenstein and Sandvik et al. which generalizes Maxwell’s equations and general relativity The variation of $\alpha$ permits an effective ghost scalar field, whose negative energy density becomes dominant at small length scales, leading to a bouncing cosmology. A thermodynamically motivated coupling that describes energy exchange between the effective ghost field and the radiation field leads to an expanding, isotropizing sequence of bounces. In the absence of entropy production, we also find solutions with stable anisotropic oscillations around a static universe.

Cosmological perturbations due to statistical thermal fluctuations in a single fluid characterized by an arbitrary equation of state are computed. Formulas to predict the scalar and tensor perturbation spectra and non-Gaussianity parameters at a given temperature are derived. These results are relevant to cosmological scenarios, such as cyclic or emergent universes, where cosmic structures may have been seeded thermally instead of originating purely from quantum vacuum fluctuations.

We compute the power spectrum of the stochastic gravitational wave background generated by cosmic string networks, described by the velocity-dependent one-scale (VOS) model for a wide range of macroscopic and microscopic parameters. The VOS model—which has been shown to provide an accurate macroscopic description of the evolution of cosmic string networks—is used to demonstrate that cosmic string networks are unable to rapidly attain scale-invariant evolution after the transition between the radiation and matter eras. However, in computations of the stochastic gravitational wave background, it is often assumed that the networks experience scale-invariant evolution throughout cosmological history. We demonstrate that this assumption leads to an underestimation of the amplitude and broadness of the peak of the spectrum. As a result, the total energy density of gravitational waves at the present day obtained using the VOS model may be up to 70% larger than that obtained under the linear scaling assumption.

In order to decode the neutrino burst signal from a Galactic core-collapse supernova (ccSN) and reveal the complicated inner workings of the explosion we need a thorough understanding of the neutrino flavor evolution from the proto-neutron star outwards. The flavor content of the signal evolves due to both neutrino collective effects and matter effects which can lead to a highly interesting interplay and distinctive spectral features. In this paper we investigate the supernova neutrino flavor evolution in three different progenitors and include collective flavor effects, the evolution of the Mikheyev, Smirnov & Wolfenstein (MSW) conversion due to the shock wave passage through the star, and the impact of turbulence. We consider both normal and inverted neutrino mass hierarchies and a value of ${\theta }_{13}$ close to the current experimental measurements. In the Oxygen-Neon-Magnesium (ONeMg) supernova we find that the impact of turbulence is both brief and slight during a window of 1–2 seconds post bounce. This is because the shock races through the star extremely quickly and the turbulence amplitude is expected to be small, less than 10%, since these stars do not require multidimensional physics to explode. Thus the spectral features of collective and shock effects in the neutrino signals from Oxygen-Neon-Magnesium supernovae may be almost turbulence free making them the easiest to interpret. For the more massive progenitors we again find that small amplitude turbulence, up to 10%, leads to a minimal modification of the signal, and the emerging neutrino spectra retain both collective and MSW features. However, when larger amounts of turbulence is added, 30% and 50%, which is justified by the requirement of multidimensional physics in order to make these stars explode, the features of collective and shock wave effects in the high ($H$) density resonance channel are almost completely obscured at late times. Yet at the same time we find the other mixing channels—the low ($L$) density resonance channel and the nonresonant channels—begin to develop turbulence signatures. Large amplitude turbulent motions in the outer layers of more massive, iron core-collapse supernovae may obscure the most obvious fingerprints of collective and shock wave effects in the neutrino signal but cannot remove them completely, and additionally bring about new features in the signal.

A light vector boson, $Z_d$, associated with a “dark sector” $U(1{)}_d$ gauge group has been introduced to explain certain astrophysical observations as well as low energy laboratory anomalies. In such models, the Higgs boson may decay into $X+Z_d$, where $X=Z$, $Z_d$ or $\gamma$. Here, we provide estimates of those decay rates as functions of the $Z_d$ coupling through either mass mixing (e.g., via an enlarged Higgs mechanism) or through heavy new fermion loops and examine the implied LHC phenomenology. Our studies focus on the higher $m_{Z_d}$ case, $\gtrsim \mathrm{\text{several}}\mathrm{GeV}$, where the rates are potentially measurable at the LHC, for interesting regions of parameter spaces, at a level complementary to low energy experimental searches for the $Z_d$. We also show how measurement of the $Z_d$ polarization (longitudinal vs transverse) can be used to distinguish the physics underlying these rare decays.