Most compact binary systems are expected to circularize before the frequency of emitted gravitational waves (GWs) enters the sensitivity band of the ground based interferometric detectors. However, several mechanisms have been proposed for the formation of binary systems, which retain eccentricity throughout their lifetimes. Since no matched-filtering algorithm has been developed to extract continuous GW signals from compact binaries on orbits with low to moderate values of eccentricity, and available algorithms to detect binaries on quasicircular orbits are suboptimal to recover these events, in this paper we propose a search method for detection of gravitational waves produced from the coalescences of eccentric binary black holes (eBBH). We study the search sensitivity and the false alarm rates on a segment of data from the second joint science run of LIGO and Virgo detectors, and discuss the implications of the eccentric binary search for the advanced GW detectors.

The Cauchy horizon inside a perturbed Kerr black hole develops an instability that transforms it into a curvature singularity. We solve for the linearized Weyl scalars ${\psi }_0$ and ${\psi }_4$ and for the curvature scalar $R_{\alpha \beta \gamma \delta }{R}^{\alpha \beta \gamma \delta }$ along outgoing null rays approaching the Cauchy horizon in the interior of perturbed Kerr black holes using the Teukolsky equation, and compare our results with those found in perturbation analysis. Our results corroborate the previous perturbation analysis result that at its early parts the Cauchy horizon evolves into a deformationally weak, null, scalar-curvature singularity. We find excellent agreement for ${\psi }_0(u=\text{const},v)$, where $u$, $v$ are advanced and retarded times, respectively. We do find, however, that the exponential growth rate of $R_{\alpha \beta \gamma \delta }{R}^{\alpha \beta \gamma \delta }(u=\text{const},v)$ approaching the singularity is dramatically slower than that found in perturbation analysis, and that the angular frequency is in excellent agreement.

The Standard Model’s accidental and anomaly-free currents, $B-L$, $L_e-L_{\mu }$, $L_e-L_{\tau }$, and $L_{\mu }-L_{\tau }$, could be indicative of a hidden gauge structure beyond the Standard Model. Additionally, neutrino masses can be generated by a dimension-5 operator that generically breaks all of these symmetries. It is therefore important to investigate the compatibility of a gauged $U^{\prime }(1)$ and neutrino phenomenology. We consider gauging each of the symmetries above with a minimal extended matter content. This includes the $Z^{\prime }$, an order parameter to break the $U^{\prime }(1)$, and three right-handed neutrinos. We find all but $B-L$ require additional matter content to explain the measured neutrino oscillation parameters. We also discuss the compatibility of the measured neutrino textures with a nonthermal dark matter production mechanism involving the decay of the $Z^{\prime }$. Finally, we present a parametric relation that implies that any sterile neutrino dark matter candidate should not be expected to contribute to neutrino masses beyond ten parts per million.

We propose a new possible explanation of the ATLAS diboson excess: that it is due to heavy resonant slepton production, followed by decay into dismuons. The smuon has a mass not too far from the $W$ and $Z$ masses, and so it is easily confused with $W$ or $Z$ bosons after its subsequent decay into dijets, through a supersymmetry violating and $R$-parity violating interaction. Such a scenario is not currently excluded by other constraints and remains to be definitively tested in Run II of the LHC. Such light smuons can easily simultaneously explain the discrepancy between the measurement of the anomalous magnetic moment of the muon and the Standard Model prediction.

We consider nucleon-decay-like signatures of hylogenesis, a variant of the antibaryonic dark matter model. For the interaction between visible and dark matter sectors through the neutron portal, we calculate the rates of dark matter scatterings off a neutron which mimic neutron-decay processes $n\to \nu \gamma$ and $n\to \nu e^{+}{e}^{-}$ with richer kinematics. We obtain bounds on the model parameters from nonobservation of the neutron decays by applying the kinematical cuts adopted in the experimental analyses. The bounds are generally (much) weaker than those coming from the recently performed study of events with a single jet of high transverse momentum and missing energy observed at the LHC. Then we suggest several new nucleon-decay-like processes with two mesons in the final state and estimate (accounting for the LHC constraints) the lower limits on the nucleon lifetime with respect to these channels. The obtained values appear to be promising for probing the antibaryonic dark matter at future underground experiments like HyperK and DUNE.

Production of the doubly heavy-flavored hadrons ($B_c$ meson, doubly heavy baryons ${\mathrm{\Xi }}_{cc}$, ${\mathrm{\Xi }}_{bc}$, ${\mathrm{\Xi }}_{bb}$, their excited states, and antiparticles of them as well) at $e^{+}{e}^{-}$ colliders is investigated under two different approaches: LO (leading-order QCD complete calculation) and LL (leading-logarithm fragmentation calculation). The results for the production obtained by the LO and LL approaches, including the angle distributions of the produced hadrons with unpolarized and polarized incoming beams, the behaviors on the energy fraction of the produced doubly heavy-flavored hadron, and comparisons of results between the two approaches, are presented in tables and figures. Thus, characteristics of the production and uncertainties of the approaches are shown precisely, and it is concluded that only if the colliders run at the energies around the $Z$ pole (which may be called the $Z$ factories) and the luminosity of the colliders is as high as possible is the study of the doubly heavy-flavored hadrons completely accessible.

We study the effect of scalar leptoquarks on the exclusive rare $B$-meson decays ${\overline{B}}_d^0\to {\overline{K}}^{*0}(\to K^{-}{\pi }^{+})l^{+}{l}^{-}$ in the full kinematically accessible physical region. We work out the constraints on leptoquark parameter space using the measured branching ratio of the $B_s\to {\mu }^{+}{\mu }^{-}$ process by the CMS and LHCb collaborations. We compute the branching ratio, forward-backward asymmetry, and isospin asymmetry distribution using the constrained parameter space. We also look into various form-factor-independent and $CP$-violating observables in the scalar leptoquark model.

We obtain the thermal photon and dilepton production rates in a strongly coupled quark-gluon plasma (QGP) at both zero and nonzero baryon chemical potentials using a bottom-up Einstein-Maxwell-dilaton holographic model that is in good quantitative agreement with the thermodynamics of ($2+1$)-flavor lattice QCD around the crossover transition for baryon chemical potentials up to 400 MeV, which may be reached in the beam energy scan at RHIC. We find that increasing the temperature $T$ and the baryon chemical potential ${\mu }_B$ enhances the peak present in both spectra. We also obtain the electric charge susceptibility, the dc and ac electric conductivities, and the electric charge diffusion as functions of $T$ and ${\mu }_B$. We find that electric diffusive transport is suppressed as one increases ${\mu }_B$. At zero baryon density, we compare our results for the dc electric conductivity and the electric charge diffusion with the latest lattice data available for these observables and find reasonable agreement around the crossover transition. Therefore, our holographic results may be used to constraint the magnitude of the thermal photon and dilepton production rates in a strongly coupled QGP, which we found to be at least 1 order of magnitude below perturbative estimates.

We study the charmed meson pair (${\overline{D}}^0{D}^0$ and $D^{+}{D}^{-}$) production in $\overline{p}p$ annihilation within an effective Lagrangian model that has only the baryon-meson degrees of freedom and involves the physical hadron masses. The reaction amplitudes include terms corresponding to the $t$-channel ${\mathrm{\Lambda }}_c^{+}$, ${\mathrm{\Sigma }}_c^{+}$, and ${\mathrm{\Sigma }}_c^{++}$ baryon exchanges and the $s$-channel excitation, propagation and decay of the $\mathrm{\Psi }(3770)$ resonance into the charmed mesons. The initial- and final-state distortion effects have been accounted for by using a simple eikonal approximation-based procedure in the same way as was done in our previous study of the $\overline{p}p\to {\overline{\mathrm{\Lambda }}}_c^{-}{\mathrm{\Lambda }}_c^{+}$ reaction within a similar model. The ${\overline{D}}^0{D}^0$ production reaction is dominated by the ${\mathrm{\Lambda }}_c^{+}$ baryon exchange process and the corresponding total cross sections are predicted to be in the range of $0.18-0.7\mu \mathrm{b}$ for antiproton beam momenta varying between threshold and $20\mathrm{GeV}/\mathrm{c}$. The $\mathrm{\Psi }(3770)$ resonance contributions have a large influence on the differential cross sections of the $D^{-}{D}^{+}$ production reaction.

We apply the phenomenological Reggeon field theory framework to investigate the relative importance of perturbative and nonperturbative multiparton correlations for the treatment of double parton scattering in proton-proton collisions. We obtain a significant correction to the so-called effective cross section for double parton scattering due to nonperturbative parton splitting. When combined with the corresponding perturbative contribution, this results in a rather weak energy and transverse momentum dependence of the effective cross section, in agreement with experimental observations at the Tevatron and the Large Hadron Collider. In addition, we observe that color fluctuations have a sizable impact on the calculated rate of double parton scattering and on the relative importance of the perturbative parton splitting mechanism.

We study $\mathrm{\Lambda }$ and $\overline{\mathrm{\Lambda }}$ production asymmetries in $p\overline{p}\to \mathrm{\Lambda }(\overline{\mathrm{\Lambda }})X$, $p\overline{p}\to J/\psi \mathrm{\Lambda }(\overline{\mathrm{\Lambda }})X$, and $p\overline{p}\to {\mu }^{\pm }\mathrm{\Lambda }(\overline{\mathrm{\Lambda }})X$ events recorded by the D0 detector at the Fermilab Tevatron collider at $\sqrt{s}=1.96\mathrm{TeV}$. We find an excess of $\mathrm{\Lambda }$’s ($\overline{\mathrm{\Lambda }}$’s) produced in the proton (antiproton) direction. This forward-backward asymmetry is measured as a function of rapidity. We confirm that the $\overline{\mathrm{\Lambda }}/\mathrm{\Lambda }$ production ratio, measured by several experiments with various targets and a wide range of energies, is a universal function of “rapidity loss,” i.e., the rapidity difference of the beam proton and the lambda.

Despite its success in the weak gravity regime, general relativity (GR) has yet to be verified in the regime of strong gravity. In this paper, we present the results of detailed ray-tracing simulations aiming at clarifying if the combined information from x-ray spectroscopy, timing, and polarization observations of stellar mass and supermassive black holes can be used to test GR’s no-hair theorem. The latter states that stationary astrophysical black holes are described by the Kerr family of metrics, with the black hole mass and spin being the only free parameters. We use four “non-Kerr metrics,” some phenomenological in nature and others motivated by alternative theories of gravity, and study the observational signatures of deviations from the Kerr metric. Particular attention is given to the case when all the metrics are set to give the same innermost stable circular orbit in quasi–Boyer-Lindquist coordinates. We give a detailed discussion of similarities and differences of the observational signatures predicted for black holes in the Kerr metric and the non-Kerr metrics. We emphasize that even though some regions of the parameter space are nearly degenerate even when combining the information from all observational channels, x-ray observations of very rapidly spinning black holes can be used to exclude large regions of the parameter space of the alternative metrics. Although it proves difficult to distinguish between the Kerr and non-Kerr metrics for some portions of the parameter space, the observations of very rapidly spinning black holes like Cyg X-1 can be used to rule out large regions for several black hole metrics.

Neutron star mergers are among the most promising sources of gravitational waves for advanced ground-based detectors. These mergers are also expected to power bright electromagnetic signals, in the form of short gamma-ray bursts, infrared/optical transients powered by r-process nucleosynthesis in neutron-rich material ejected by the merger, and radio emission from the interaction of that ejecta with the interstellar medium. Simulations of these mergers with fully general relativistic codes are critical to understand the merger and postmerger gravitational wave signals and their neutrinos and electromagnetic counterparts. In this paper, we employ the Spectral Einstein Code to simulate the merger of low mass neutron star binaries (two $1.2M_{\odot }$ neutron stars) for a set of three nuclear-theory-based, finite temperature equations of state. We show that the frequency peaks of the postmerger gravitational wave signal are in good agreement with predictions obtained from recent simulations using a simpler treatment of gravity. We find, however, that only the fundamental mode of the remnant is excited for long periods of time: emission at the secondary peaks is damped on a millisecond time scale in the simulated binaries. For such low mass systems, the remnant is a massive neutron star which, depending on the equation of state, is either permanently stable or long lived (i.e. rapid uniform rotation is sufficient to prevent its collapse). We observe strong excitations of $l=2$, $m=2$ modes, both in the massive neutron star and in the form of hot, shocked tidal arms in the surrounding accretion torus. We estimate the neutrino emission of the remnant using a neutrino leakage scheme and, in one case, compare these results with a gray two-moment neutrino transport scheme. We confirm the complex geometry of the neutrino emission, also observed in previous simulations with neutrino leakage, and show explicitly the presence of important differences in the neutrino luminosity, disk composition, and outflow properties between the neutrino leakage and transport schemes.

General criteria for the existence of conformally flat Riemannian solutions in three-dimensional Poincaré gauge theory without matter are formulated. Using these criteria, we show that the Oliva-Tempo-Troncoso black hole, a solution of the Bergshoeff-Hohm-Townsend gravity, is also an exact vacuum solution of the Poincaré gauge theory. The related conserved charges, calculated from the Hamiltonian boundary term, are shown to satisfy the first law of black hole thermodynamics. The form of the boundary term is verified by using the covariant Hamiltonian approach.

We investigate the spectral dimension obtained from nonlocal continuum d’Alembertians derived from causal sets. We find a universal dimensional reduction to two dimensions, in all dimensions. We conclude by discussing the validity and relevance of our results within the broader context of quantum field theories based on these nonlocal dynamics.

Large field inflation can be sensitive to perturbative and nonperturbative quantum corrections that spoil slow roll. A large number $N$ of light species in the theory, which occur in many string constructions, can amplify these problems. One might even worry that in a de Sitter background, light species will lead to a violation of the covariant entropy bound at large $N$. If so, requiring the validity of the covariant entropy bound could limit the number of light species and their couplings, which in turn could severely constrain axion-driven inflation. Here we show that there is no such problem when we correctly renormalize models with many light species, taking the physical Planck scale to be $M_{pl}^2\gtrsim N{\mathcal{M}}_{\mathrm{UV}}^2$, where ${\mathcal{M}}_{\mathrm{UV}}$ is the cutoff for the quantum field theory coupled to semiclassical quantum gravity. The number of light species then cancels out of the gravitational entropy of de Sitter or near-de Sitter backgrounds at leading order. Working in detail with $N$ scalar fields in de Sitter space, renormalized to one loop order, we show that the gravitational entropy automatically obeys the covariant entropy bound. Furthermore, while the axion decay constant is a strong coupling scale for the axion dynamics, we show that it is not in general the cutoff of 4d semiclassical gravity. After renormalizing the two point function of the inflaton, we note that it is also controlled by scales much below the cutoff. We revisit $N$-flation and Kachru-Kallosh-Linde-Trivedi-type compactifications in this light, and show that they are perfectly consistent with the covariant entropy bound. Thus, while quantum gravity might yet spoil large field inflation, holographic considerations in the semiclassical theory do not obstruct it.

We report on constraints to the cosmological jerk parameter ($j$) and to possible variability of the fine-structure constant ($\mathrm{\Delta }\alpha /\alpha$) based on stochastic quintessence models of dark energy, discussed by Chongchitnan and Efstathiou [Phys. Rev. D 76, 043508 (2007)]. We confirm the results by these authors in the sense that many viable solutions can be obtained, obeying current observational constraints in low redshifts. We add the observables $j$ and $\mathrm{\Delta }\alpha /\alpha$ to this conclusion. However, we find peculiarities that may produce, in the nearby universe, potential observational imprints in future cosmological data. We conclude, for redshifts $z\lesssim 3$, that (i) $j(z)$ fluctuates due to the stochasticity of the models, reaching an amplitude of up to 5% relatively to the $\mathrm{\Lambda }$ cold dark matter model value ($j_{\mathrm{\Lambda }\mathrm{CDM}}=1$); and (ii) by contrasting two distinct (“extreme”) types of solutions, variabilities in $\alpha (z)$, linked to a linear coupling ($\zeta$) between the dark energy and electromagnetic sectors, are weakly dependent on redshift, for couplings of the order $|\zeta |\sim 10^{-4}$, even for large variations in the equation of state parameter at relatively low redshifts. Nonlinear couplings produce an earlier and steeper onset of the evolution in $\mathrm{\Delta }\alpha /\alpha (z)$, but can still accommodate the data for weak enough couplings.

We explore the physics and observational consequences of tidal compression events (TCEs) of dark-matter clumps (DMCs) by supermassive black holes (SMBHs). Our analytic calculations show that a DMC approaching a SMBH much closer than the tidal radius undergoes significant compression along the axis perpendicular to the orbital plane, shortly after pericenter passage. For DMCs composed of self-annihilating dark-matter particles, we find that the boosted DMC density and velocity dispersion lead to a flaring of the annihilation rate, most pronounced for a velocity-dependent annihilation cross section. If the end products of the annihilation are photons, this results in a gamma-ray flare, detectable (and possibly already detected) by the Fermi telescope for a range of model parameters. If the end products of dark-matter annihilation are relativistic electrons and positrons and the local magnetic field is large enough, TCEs of DMCs can lead to flares of synchrotron radiation. Finally, TCEs of DMCs lead to a burst of gravitational waves, in addition to the ones radiated by the orbital motion alone, and with a different frequency spectrum. These transient phenomena provide interesting new avenues to explore the properties of dark matter.

The delayed cosmology [D. Choudhury et al., J. Cosmol. Astropart. Phys. 02 (2012) 046] assumes that the evolution of geometries is delayed relative to that of matter and/or energy. This idea allows inflation to occur without inflaton fields or vacuum energies of any kind. We consider the production and evolution of primordial perturbations in this model. The results indicate that we could obtain a nearly scale-free power spectrum consistent with observations starting from a totally radiation-dominated early universe.