Compact binary mergers are the strongest candidates for the progenitors of short gamma ray bursts (SGRBs). If a gravitational wave signal from the compact binary merger is observed in association with a SGRB, such a synergy can help us understand many interesting aspects of these bursts. We examine the accuracies with which a worldwide network of gravitational wave interferometers would measure the inclination angle (the angle between the angular momentum axis of the binary and the observer’s line of sight) of the binary. We compare the projected accuracies of gravitational wave detectors to measure the inclination angle of double neutron star and neutron star–black hole binaries for different astrophysical scenarios. We find that a five-detector network can measure the inclination angle to an accuracy of $\sim 5.1$ (2.2) deg for a double neutron star (neutron star–black hole) system at 200 Mpc if the direction of the source as well as the redshift is known electromagnetically. We argue as to how an accurate estimation of the inclination angle of the binary can prove to be crucial in understanding off-axis GRBs, the dynamics and the energetics of their jets, and help the searches for (possible) orphan afterglows of the SGRBs.

This paper studies a generic fourth-order theory of gravity with Lagrangian density $f(R,R_c^2,R_m^2,{\mathcal{L}}_m)$, where $R_c^2$ and $R_m^2$ respectively denote the square of the Ricci and Riemann tensors. By considering explicit $R^2$ dependence and imposing the “coherence condition” $f_{R^2}=f_{R_m^2}=-f_{R_c^2}/4$, the field equations of $f(R,R^2,R_c^2,R_m^2,{\mathcal{L}}_m)$ gravity can be smoothly reduced to that of $f(R,\mathcal{G},{\mathcal{L}}_m)$ generalized Gauss-Bonnet gravity with $\mathcal{G}$ denoting the Gauss-Bonnet invariant. We use Noether’s conservation law to study the $f({\mathcal{R}}_1,{\mathcal{R}}_2\dots ,{\mathcal{R}}_n,{\mathcal{L}}_m)$ model with nonminimal coupling between ${\mathcal{L}}_m$ and Riemannian invariants ${\mathcal{R}}_i$, and conjecture that the gradient of nonminimal gravitational coupling strength ${\nabla }^{\mu }{f}_{{\mathcal{L}}_m}$ is the only source for energy-momentum nonconservation. This conjecture is applied to the $f(R,R_c^2,R_m^2,{\mathcal{L}}_m)$ model, and the equations of continuity and nongeodesic motion of different matter contents are investigated. Finally, the field equation for Lagrangians including the traceless-Ricci square and traceless-Riemann (Weyl) square invariants is derived, the $f(R,R_c^2,R_m^2,{\mathcal{L}}_m)$ model is compared with the $f(R,R_c^2,R_m^2,T)+2\kappa {\mathcal{L}}_m$ model, and consequences of nonminimal coupling for black hole and wormhole physics are considered.

We propose a new way of analyzing, and analytically representing, the ringdown part of the gravitational wave signal emitted by coalescing black hole binaries. By contrast with the usual linear decomposition of the multipolar complex waveform $h(t)$ in a sum of quasinormal modes, our procedure relies on a multiplicative decomposition of $h(t)$ as the product of the fundamental quasinormal mode with a remaining time-dependent complex factor whose amplitude and phase are separately fitted. As an illustrative example, we apply our analysis and fitting procedure to the ringdown part of a sample of sixteen $\ell =m=2$ equal-mass, spinning, nonprecessing, numerical waveforms computed with the ${\mathrm{SP}}_{\mathrm{E}}\mathrm{C}$ code, now publicly available in the SXS catalog. Our approach yields an efficient and accurate way to represent the ringdown waveform, thereby offering a new way to complete the analytical effective-one-body inspiral-plus-plunge waveform.

We investigate the effects of using the full waveform (FWF) over the conventional restricted waveform of the inspiral signal from a coalescing compact binary system in extracting the parameters of the source, using a global network of second generation interferometric detectors. We study a hypothetical population of $(1.4–10)M_{\odot }$ neutron star–black hole binaries (uniformly distributed and oriented in the sky) by employing the full post-Newtonian waveforms, which not only include contributions from various harmonics other than the dominant one (quadrupolar mode) but also the post-Newtonian amplitude corrections associated with each harmonic, of the inspiral signal expected from this system. It is expected that the GW detector network consisting of the two LIGO detectors and a Virgo detector will be joined by KAGRA (a Japanese detector) and by proposed LIGO-India. We study the problem of parameter estimation with all 16 possible detector configurations. Comparing medians of error distributions obtained using FWFs with those obtained using restricted waveforms (which only include contributions from the dominant harmonic with Newtonian amplitude) we find that the measurement accuracies for luminosity distance and the cosine of the inclination angle improve almost by a factor of 1.5–2 depending upon the network under consideration. We find that this improvement can be attributed to the presence of additional inclination angle dependent terms, which appear in the amplitude corrections to various harmonics, which break the strong degeneracy between the luminosity distance and inclination angle. Although the use of FWF does not improve the source localization accuracy much, the global network consisting of five detectors will improve the source localization accuracy by a factor of 4 as compared to the estimates using a three-detector LIGO-Virgo network for the same waveform model.

To shed light on the fundamental problems posed by dark energy and dark matter, a large number of experiments have been performed and combined to constrain cosmological models. We propose a novel way of quantifying the information gained by updates on the parameter constraints from a series of experiments which can either complement earlier measurements or replace them. For this purpose, we use the Kullback-Leibler divergence or relative entropy from information theory to measure differences in the posterior distributions in model parameter space from a pair of experiments. We apply this formalism to a historical series of cosmic microwave background experiments ranging from Boomerang to WMAP, SPT, and Planck. Considering different combinations of these experiments, we thus estimate the information gain in units of bits and distinguish contributions from the reduction of statistical errors and the “surprise” corresponding to a significant shift of the parameters’ central values. For this experiment series, we find individual relative entropy gains ranging from about 1 to 30 bits. In some cases, e.g. when comparing WMAP and Planck results, we find that the gains are dominated by the surprise rather than by improvements in statistical precision. We discuss how this technique provides a useful tool for both quantifying the constraining power of data from cosmological probes and detecting the tensions between experiments.

First-order phase transitions are a source of stochastic gravitational radiation. Precision calculations of the gravitational waves emitted during these processes sourced by both the degrees of freedom undergoing the transition and the anisotropic stress of the ambient constituents have reached an age of maturity. Here we present numerical simulations of a scalar field coupled to a fluid for a set of models that represent different types of first-order phase transitions. We parametrize the final gravitational wave spectrum as a function of the ratio of the energies of the constituents and the coupling between the two sectors. In most of the cases we study, the field sector is the dominant source of gravitational radiation, but it is possible in certain scenarios for the fluid to have the most important contribution.

Previous attempts at explaining the gamma-ray excess near the Galactic Center have focused on dark matter annihilating directly into Standard Model particles. This results in a preferred dark matter mass of 30–40 GeV (if the annihilation is into $b$ quarks) or 10 GeV (if it is into leptons). Here we show that the gamma-ray excess is also consistent with heavier dark matter particles; in models of secluded dark matter, dark matter with mass up to 76 GeV provides a good fit to the data. This occurs if the dark matter first annihilates to an on-shell particle that subsequently decays to Standard Model particles through a portal interaction. This is a generic process that works in models with annihilation, semi-annihilation or both. We explicitly demonstrate this in a model of hidden vector dark matter with an SU(2) gauge group in the hidden sector.

By incorporating both the tensor-to-scalar ratio and the measured value of the spectral index, we set a bound on solo small field inflation of $\mathrm{\Delta }\varphi /m_{\text{Pl}}\ge 1.00\sqrt{r/0.1}$. Unlike previous bounds which require monotonic ${\epsilon }_V$, $|{\eta }_V|<1$, and 60 $e$-folds of inflation, the bound remains valid for nonmonotonic ${\epsilon }_V$, $|{\eta }_V|\gtrsim 1$, and for inflation which occurs only over the eight $e$-folds which have been observed on the cosmic microwave background. The negative value of the spectral index over the observed eight $e$-folds is what makes the bound strong; we illustrate this by surveying single field models and finding that for $r\gtrsim 0.1$ and eight $e$-folds of inflation, there is no simple potential which reproduces observed cosmic microwave background perturbations and remains sub-Planckian. Models that are sub-Planckian after eight $e$-folds must be patched together with a second epoch of inflation that fills out the remaining $\sim 50$ $e$-folds. This second, post–cosmic microwave background epoch is characterized by extremely small ${\epsilon }_V$ and therefore an increasing scalar power spectrum. Using the fact that large power can overabundantly produce primordial black holes, we bound the maximum energy level of the second phase of inflation.

Scenarios of the cosmological evolution are studied by using an equation of state (EoS) having points where the specific enthalpy of the cosmological fluid vanishes. A large class of barotropic equations of state admits, depending upon initial conditions, analogues of the “Big Rip” [, Phys. Rev. Lett. 91, 071301 (2003)], as well as solutions describing exponential inflation followed by usual matter dominance; their classification is proposed. We discuss extensions to a more general two-parametric EoS dealing with a preinflationary evolution and yielding stages with both increasing and decreasing energy density as a function of time. Possible cosmological scenarios with transitions from collapse to an expanding Universe or a closed oscillating one, without reaching a singularity, are included.

We investigate the late-time cosmological behavior of scalar-tensor theories with a universal multiplicative coupling between the scalar field and the matter Lagrangian in the matter era. This class of theory encompasses the case of the massless string dilaton [see Damour and Polyakov, General Relativity and Gravitation 26, 1171 (1994)] as well as a theory with an intrinsic decoupling mechanism in the solar system [see Minazzoli and Hees, Phys. Rev. D 88, 041504 (2013)]. The cosmological evolution is studied in the general relativity limit justified by solar system constraints on the gravitation theory. The behavior of these cosmological evolutions are then compared to two types of observations: the constraints on temporal variations of the constants of nature and the distance-luminosity measurements. In particular, the nonminimal coupling implies that the distance-luminosity relation is modified compared to general relativity. Theories producing a cosmological behavior in agreement with these observations are identified.

The present work describes our investigation of the navigation anomaly of the Pioneer 10 and 11 probes which became known as the Pioneer Anomaly. It appeared as a linear drift in the Doppler data received by the spacecraft, which has been ascribed to an approximately constant Sunward acceleration of about $8.5\times 10^{-13}\mathrm{km}/{\mathrm{s}}^2$. Since then, the existence of the anomaly has been confirmed independently by several groups and a large effort was devoted to find its origin. Recently, different analyses were published where the authors claimed the acceleration due to anisotropic thermal emission to be the most likely cause of the unexplained acceleration. Here we report the methodology and the results of an independent study carried out in the last years, aimed at supporting the thermal origin of the anomaly. This work consists of two main parts: thermal modeling of the spacecraft throughout its trajectory, and orbit determination analysis. Based on existing documentation and published telemetry data, we built a thermal finite element model of the spacecraft, whose complexity has been constrained to a degree allowing for sensitivity analysis, leading to the computation of its formal uncertainty. The trajectory analysis and orbit determination were carried out using NASA/JPL’s Orbit Determination Program, and our results show that orbital solutions are achieved that do not require the addition of any “unknown” acceleration other than that of thermal origin.

Inclusive charged hadron cross sections, $d\sigma /d\eta$, and the mean transverse momenta, $⟨p_T⟩$, are considered within the two component model, which combines the powerlike and the exponential terms in $p_T$. The observed dependences of the spectra shape on energy and the event multiplicity qualitatively agree with that expected from the Regge theory with the perturbative QCD Pomeron. Finally, the dependences observed are used to make predictions on the mean transverse momenta, $⟨p_T⟩$, as function of multiplicity at LHC energies, which are tested on available experimental data.

If grand unification is real, searches for baryon-number violation should be included on the list of observables that may reveal information regarding the origin of neutrino masses. Making use of an effective-operator approach and assuming that nature is $SU(5)$ invariant at very short distances, we estimate the consequences of different scenarios that lead to light Majorana neutrinos for low-energy phenomena that violate baryon number minus lepton number ($B-L$) by two (or more) units, including neutron-antineutron oscillations and $B-L$ violating nucleon decays. We find that, among all possible effective theories of lepton-number violation that lead to nonzero neutrino masses, only a subset is, broadly speaking, consistent with grand unification.

We reexamine the models with gauge mediation in view of the minimality and the Higgs boson mass. As a result, we arrive at a very simple model of direct gauge mediation which does not suffer from the flavor problems nor the $CP$ problems. The minimal supersymmetric Standard Model spectrum is determined by only three parameters, the size of the effective supersymmetry breaking, the messenger scale, and the messenger number. Surprisingly, such a very simple model is not only consistent with all the current constraints but also is testable at the upgraded LHC experiments. In particular, we show that the parameter space which is consistent with the Higgs boson mass at around 126 GeV can be tested through the stable stau searches at the 14 TeV run of the LHC. The gravitino is a viable candidate for a dark matter. We also give a short discussion on a possible connection of our model to the recently discovered x-ray line signal at 3.5 keV in the X-ray Multi-Mirror Mission Newton x-ray observatory data.

We consider models where a hidden $U(1{)}^{\prime }$ interacts with the Standard Model via kinetic mixing. We assume the dark matter is neutral under this $U(1{)}^{\prime }$, but interacts with it via higher-dimensional operators. In particular, we consider a hidden dipole operator for fermionic dark matter, and charge radius and Rayleigh operators for scalar dark matter. These models naturally explain the absence of direct detection signals, but allow for a thermal cosmology. LHC searches for the $Z^{\prime }$ represent a powerful probe.

We propose a model in which the origin of neutrino mass is dependent on the existence of dark matter. Neutrinos acquire mass at the three-loop level and the dark matter is the neutral component of a fermion triplet. We show that experimental constraints are satisfied and that the dark matter can be tested in future direct-detection experiments. Furthermore, the model predicts a charged scalar that can be within reach of collider experiments like the LHC.

It has been suggested that cold dark matter (CDM) has difficulties in explaining tentative evidence for noncuspy halo profiles in small galaxies, and the low velocity dispersions observed in the largest Milky Way satellites (“too-big-to-fail” problem). Strongly self-interacting dark matter has been noted as a robust solution to these problems. The elastic cross sections required are much larger than predicted by generic CDM models, but could naturally be of the right size if dark matter is composite. We explore in a general way the constraints on models where strongly interacting CDM is in the form of dark “atoms” or “molecules,” or bound states of a confining gauge interaction (“hadrons”). These constraints include considerations of relic density, direct detection, big bang nucleosynthesis, the cosmic microwave background, and LHC data.

We study a grand unified $SU(5)\times SU(5{)}^{\prime }$ model supplemented by $D_2$ parity. The $D_2$ greatly reduces the number of parameters and is important for phenomenology. The model, we present, has various novel and interesting properties. Because of the specific pattern of grand unification symmetry breaking and emerged strong dynamics at low energies, the Standard Model leptons, along with right-handed/sterile neutrinos, come out as composite states. The generation of the charged fermion and neutrino masses are studied within the considered scenario. Moreover, the issues of gauge coupling unification and nucleon stability are investigated in details. Various phenomenological implications are also discussed.

Motivated by the sign problem, we calculate the effective Polyakov line action corresponding to certain SU(3) lattice gauge theories on a $16^3\times 6$ lattice via the “relative weights” method introduced in our previous papers. The calculation is carried out at $\beta =5.6$, 5.7 for the pure gauge theory and at $\beta =5.6$ for the gauge field coupled to a relatively light scalar particle. In the latter example we determine the effective theory also at finite chemical potential and show how observables relevant to phase structure can be computed in the effective theory via mean field methods. In all cases a comparison of Polyakov line correlators in the effective theory and the underlying lattice gauge theory, computed numerically at zero chemical potential, shows accurate agreement down to correlator magnitudes of order $10^{-5}$. We also derive the effective Polyakov line action corresponding to a gauge theory with heavy quarks and large chemical potential and apply mean field methods to extract observables.