In this paper, we study the Chaplygin gas Hořava-Lifshitz quantum cosmology. Using Schutz formalism and Arnowitt-Deser-Misner decomposition, we obtain the corresponding Schrödinger-Wheeler-DeWitt equation. We obtain exact classical and quantum mechanical solutions and construct wave packets to study the time evolution of the expectation value of the scale factor for two cases. We show that unlike classical solutions and upon choosing appropriate initial conditions, the expectation value of the scale factor never tends to the singular point which exhibits the singularity-free behavior of the solutions in the quantum domain.

Modified gravity theories often contain a scalar field of gravitational strength which interacts with matter. We examine constraints on the range and the coupling strength of a scalar gravitational degree of freedom using a subset of current data that can be safely analyzed within the linear perturbation theory. Using a model-independent implementation of scalar-tensor theories in mgcamb in terms of two functions of the scale factor describing the mass and the coupling of the scalar degree of freedom, we derive constraints on the $f(R)$, generalized chameleon, symmetron and dilaton models. Since most of the large scale structure data available today is from relatively low redshifts, only a limited range of observed scales is in the linear regime, leading to relatively weak constraints. We then perform a forecast for a future large scale structure survey, such as the Large Synoptic Survey Telescope (LSST), which will map a significant volume at higher redshifts, and show that it will produce much stronger constraints on scalar interactions in specific models. We also perform a principal component analysis and find that future surveys should be able to provide tight constraints on several eigenmodes of the scalar mass evolution.

Entropic cosmology assumes several forms of entropy on the horizon of the universe, where the entropy can be considered to behave as if it were related to the exchange (the transfer) of energy. To discuss this exchangeability, the consistency of the two continuity equations obtained from two different methods is examined, focusing on a homogeneous, isotropic, spatially flat, and matter-dominated universe. The first continuity equation is derived from the first law of thermodynamics, whereas the second equation is from the Friedmann and acceleration equations. To study the influence of forms of entropy on the consistency, a phenomenological entropic-force model is examined, using a general form of entropy proportional to the $n$th power of the Hubble horizon. In this formulation, the Bekenstein entropy (an area entropy), the Tsallis-Cirto black-hole entropy (a volume entropy), and a quartic entropy are represented by $n=2$, 3, and 4, respectively. The two continuity equations for the present model are found to be consistent with each other, especially when $n=2$, i.e., the Bekenstein entropy. The exchange of energy between the bulk (the universe) and the boundary (the horizon of the universe) should be a viable scenario consistent with the holographic principle.

The annihilation of nonrelativistic dark matter particles at tree level can be strongly enhanced by the radiation of an additional gauge boson. This is particularly true for the helicity-suppressed annihilation of Majorana particles, like neutralinos, into fermion pairs. Surprisingly, and despite the potentially large effect due to the strong coupling, this has so far been studied in much less detail for the internal bremsstrahlung of gluons than for photons or electroweak gauge bosons. Here, we aim at bridging that gap by presenting a general analysis of neutralino annihilation into quark anti-quark pairs and a gluon, allowing e.g. for arbitrary neutralino compositions and keeping the leading quark mass dependence at all stages in the calculation. We find in some cases largely enhanced annihilation rates, especially for scenarios with squarks being close to degenerate in mass with the lightest neutralino, but also notable distortions in the associated antiproton and gamma-ray spectra. Both effects significantly impact limits from indirect searches for dark matter and are thus important to be taken into account in, e.g., global scans. For extensive scans, on the other hand, full calculations of QCD corrections are numerically typically too expensive to perform for each point in parameter space. We present here for the first time an efficient, numerically fast implementation of QCD corrections, extendable in a straightforward way to nonsupersymmetric models, which avoids computationally demanding full one-loop calculations or event generator runs and yet fully captures the leading effects relevant for indirect dark matter searches. In this context, we also present updated constraints on dark matter annihilation from cosmic-ray antiproton data. Finally, we comment on the impact of our results on relic density calculations.

We consider the application of group invariant transformations in order to constrain a flat isotropic and homogeneous cosmological model, containing a Brans-Dicke scalar field and a perfect fluid with a constant equation of state parameter $w$, where the latter is not interacting with the scalar field in the gravitational action integral. The requirement that the Wheeler-DeWitt equation be invariant under one-parameter point transformations provides us with two families of power-law potentials for the Brans-Dicke field, in which the powers are functions of the Brans-Dicke parameter ${\omega }_{\mathrm{BD}}$ and the parameter $w$. The existence of the Lie symmetry in the Wheeler-DeWitt equation is equivalent to the existence of a conserved quantity in field equations and with oscillatory terms in the wave function of the Universe. This enables us to solve the field equations. For a specific value of the conserved quantity, we find a closed-form solution for the Hubble factor, which is equivalent to a cosmological model in general relativity containing two perfect fluids. This provides us with different models for specific values of the parameters ${\omega }_{\mathrm{BD}}$, and $w$. Finally, the results hold for the specific case where the Brans-Dicke parameter ${\omega }_{\mathrm{BD}}$ is zero, that is, for the O’Hanlon massive dilaton theory and, consequently, for $f(R)$ gravity in the metric formalism.

We report results of a wideband search for periodic gravitational waves from isolated neutron stars within the Orion spur towards both the inner and outer regions of our Galaxy. As gravitational waves interact very weakly with matter, the search is unimpeded by dust and concentrations of stars. One search disk (A) is 6.87° in diameter and centered on $20^{\mathrm{h}}10^{\mathrm{m}}54.71^{\mathrm{s}}+33°33^{\prime }25.29^{\prime \prime }$, and the other (B) is 7.45° in diameter and centered on $8^{\mathrm{h}}35^{\mathrm{m}}20.61^{\mathrm{s}}-46°49^{\prime }25.151^{\prime \prime }$. We explored the frequency range of 50–1500 Hz and frequency derivative from 0 to $-5\times {10}^{-9}\mathrm{Hz}/\mathrm{s}$. A multistage, loosely coherent search program allowed probing more deeply than before in these two regions, while increasing coherence length with every stage. Rigorous follow-up parameters have winnowed the initial coincidence set to only 70 candidates, to be examined manually. None of those 70 candidates proved to be consistent with an isolated gravitational-wave emitter, and 95% confidence level upper limits were placed on continuous-wave strain amplitudes. Near 169 Hz we achieve our lowest 95% C.L. upper limit on the worst-case linearly polarized strain amplitude $h_0$ of $6.3\times {10}^{-25}$, while at the high end of our frequency range we achieve a worst-case upper limit of $3.4\times {10}^{-24}$ for all polarizations and sky locations.

The prospects are explored for testing Lorentz and $CPT$ symmetry in the top-quark sector. We present the relevant Lagrange density, discuss physical observables, and describe the signals to be sought in experiments. For top-antitop pair production via quark or gluon fusion with subsequent semileptonic or hadronic decays, we obtain the matrix element in the presence of Lorentz violation using the narrow-width approximation. The issue of testing $CPT$ symmetry in the top-quark sector is also addressed. We demonstrate that single-top production and decay is well suited to a search for $CPT$ violation, and we present the matrix elements for single-top production in each of the four tree-level channels. Our results are applicable to searches for Lorentz violation and studies of $CPT$ symmetry in collider experiments, including notably high-statistics top-antitop and single-top production at the Large Hadron Collider.

We study in a bottom-up approach the theoretically consistent description of additional resonances in the electroweak sector beyond the discovered Higgs boson as simplified models. We focus on scalar and tensor resonances. Our formalism is suited for strongly coupled models, but can also be applied to weakly interacting theories. The spurious degrees of freedom of tensor resonances that would lead to bad high-energy behavior are treated using a generalization of the Stückelberg formalism. We calculate scattering amplitudes for vector-boson and Higgs boson pairs. The high-energy region is regulated by the T-matrix unitarization procedure, leading to amplitudes that are well behaved on the whole phase space. We present numerical results for complete partonic processes that involve resonant vector-boson scattering for the current and upcoming runs of LHC.

We present the scalar leptoquark pair production process at the LHC computed at the next-to-leading order in QCD, matched to the Pythia parton shower using the MC@NLO formalism. We consider the leading order decay of a leptoquark to a lepton ($e$, $\mu$, $\tau$ or ${\nu }_e$, ${\nu }_{\mu }$, ${\nu }_{\tau }$) and a jet and observe the effects of parton shower on the final states. For demonstration, we display the kinametical distributions of a selection of observables along with their scale uncertainties for the 13 TeV LHC. We also present pair production cross sections and $K$-factors using a massless five-quark flavor scheme for different LHC center-of-mass energies. The complete stand-alone code is available online.

The next-to-minimal supersymmetric extension of the Standard Model (NMSSM) with a Higgs boson of mass 125 GeV can be compatible with stop masses of order of the electroweak scale, thereby reducing the degree of fine-tuning necessary to achieve electroweak symmetry breaking. Moreover, in an attractive region of the NMSSM parameter space, corresponding to the “alignment limit” in which one of the neutral Higgs fields lies approximately in the same direction in field space as the doublet Higgs vacuum expectation value, the observed Higgs boson is predicted to have Standard-Model–like properties. We derive analytical expressions for the alignment conditions and show that they point toward a more natural region of parameter space for electroweak symmetry breaking, while allowing for perturbativity of the theory up to the Planck scale. Moreover, the alignment limit in the NMSSM leads to a well-defined spectrum in the Higgs and Higgsino sectors and yields a rich and interesting Higgs boson phenomenology that can be tested at the LHC. We discuss the most promising channels for discovery and present several benchmark points for further study.

A detailed analysis to find a missing $\psi (4S)$ is made by utilizing the recent precise measurements of the cross section for the process $e^{+}{e}^{-}\to \psi (2S){\pi }^{+}{\pi }^{-}$ by Belle. Assuming three resonances $Y(4360)$, $Y(4660)$, and $\psi (4S)$ to fit the data, we obtain the resonance parameters for $\psi (4S)$ as $m=4243\mathrm{MeV}$ and $\mathrm{\Gamma }=16\pm 31\mathrm{MeV}$, showing a narrow state as predicted before. A combined fit to the data $e^{+}{e}^{-}\to \psi (2S){\pi }^{+}{\pi }^{-}$, $h_c{\pi }^{+}{\pi }^{-}$, and ${\chi }_{c0}\omega$ is also performed to obtain the similar resonance parameters of $\psi (4S)$. The upper limit of the branching ratio is fitted to be $\mathcal{B}(\psi (4S)\to \psi (2S){\pi }^{+}{\pi }^{-})<3\times {10}^{-3}$, which can be understood by hadronic loop contributions within a reasonable range of parameters. In addition, the ratios of the branching ratios of the $\psi (4S)$ dipion transition to that of $\psi (4S)\to {\chi }_{c0}\omega$ are fitted, which can be further measured by BESIII and the forthcoming BelleII to confirm the existence of $\psi (4S)$.

In the presence of both direct and indirect unitarity violation in the lepton mixing matrix, we derive a complete set of series expansion formulas for neutrino oscillation probabilities in matter of constant density. Expansions in the mass hierarchy parameter $\alpha \equiv \mathrm{\Delta }{m}_{21}^2/\mathrm{\Delta }{m}_{31}^2$ and those unitarity violation parameters $s_{ij}^2$ (for $i=1$, 2, 3 and $j=4$, 5, 6) up to the first order are studied in this paper. We analyze the accuracy of the analytical series expansion formulas in different regions of $L/E$. A detailed numerical analysis is also performed, of which the different effects of the direct and the indirect unitarity violation are particularly emphasized. We also study in this paper the summed ${\nu }_{\alpha }\to {\nu }_{e,\nu ,\tau }$ probabilities, whose deviation from the unity provides a definite signal of the unitarity violation.

We present constraints on the nature of axions and axionlike particles (ALPs) by analyzing gamma-ray data from neutron stars using the Fermi Large Area Telescope. In addition to axions solving the strong $CP$ problem of particle physics, axions and ALPs are also possible dark matter candidates. We investigate axions and ALPs produced by nucleon-nucleon bremsstrahlung within neutron stars. We derive a phenomenological model for the gamma-ray spectrum arising from subsequent axion decays. By analyzing five years of gamma-ray data (between 60 and 200 MeV) for a sample of four nearby neutron stars, we do not find evidence for an axion or ALP signal; thus we obtain a combined 95% confidence level upper limit on the axion mass of $7.9\times {10}^{-2}\mathrm{eV}$, which corresponds to a lower limit for the Peccei-Quinn scale $f_a$ of $7.6\times {10}^7\mathrm{GeV}$. Our constraints are more stringent than previous results probing the same physical process, and are competitive with results probing axions and ALPs by different mechanisms.

We calculate the radiation accompanying the gravitational collision of a domain wall and a point particle in five-dimensional spacetime. This process—which can be regarded as brane-particle bremsstrahlung, here called branestrahlung—has unusual features. Since the brane has intrinsic dynamics, it gets excited in the course of collision, and, in particular, at the moment of perforation the shock branon wave is generated, which then expands with the velocity of light. Therefore, apart from the time-like source whose radiation can be computed in a standard way, the total radiation source contains a light-like part whose retarded field is quite nontrivial, exhibiting interesting retardation and memory effects. We analyze this field in detail, showing that—contrary to the claims that the light-like sources should not radiate at all—the radiation is nonzero and has a classically divergent spectrum. We estimate the total radiation power introducing appropriate cutoffs. In passing, we explain how the sum of the nonlocal (with the support inside the light cone) and the local (supported on the cone) singular parts of the Green’s function of the five-dimensional d’Alembert equation together defines a regular functional.

Asymptotic safety is an attractive scenario for the dynamics of quantum spacetime. Here, we work from a phenomenologically motivated point of view and emphasize that a viable dynamics for quantum gravity in our Universe must account for the existence of matter. In particular, we explore the scale dependence of a scalar matter-gravity vertex, and investigate whether an interacting fixed point exists for the so-defined Newton coupling. We find a viable fixed point in the pure-gravity system, disregarding scalar quantum fluctuations. We explore its extensions to the case with dynamical scalars, and find indications of asymptotic safety in the matter-gravity system. We moreover examine the anomalous dimensions for different components of the metric fluctuations, and find significant differences between the transverse traceless and scalar component.

We study slowly rotating, asymptotically flat black holes in Einstein-æther theory and show that solutions that are free from naked finite area singularities form a two-parameter family. These parameters can be thought of as the mass and angular momentum of the black hole, while there are no independent æ ther charges. We also show that the æ ther has nonvanishing vorticity throughout the spacetime, as a result of which there is no hypersurface that resembles the universal horizon found in static, spherically symmetric solutions. Moreover, for experimentally viable choices of the coupling constants, the frame-dragging potential of our solutions only shows percent-level deviations from the corresponding quantities in General Relativity and Hořava gravity. Finally, we uncover and discuss several subtleties in the correspondence between Einstein-æther theory and Hořava gravity solutions in the $c_{\omega }\to \infty$ limit.