As a candidate of quantum gravity in ultrahigh energy, the $(3+1)$-dimensional Hořava-Lifshitz (HL) gravity with critical exponent $z\ne 1$ indicates anisotropy between time and space at short distance. In the paper, we investigate the most general $z=d$ Hořava-Lifshitz gravity in arbitrary spatial dimension $d$, with a generic dynamical Ricci flow parameter $\lambda$ and a detailed balance violation parameter $\epsilon$. In arbitrary dimensional generalized ${\mathrm{HL}}_{d+1}$ gravity with $z\ge d$ at long distance, we study the topological neutral black hole solutions with general $\lambda$ in $z=d$ ${\mathrm{HL}}_{d+1}$, as well as the topological charged black holes with $\lambda =1$ in $z=d$ ${\mathrm{HL}}_{d+1}$. The HL gravity in the Lagrangian formulation is adopted, while in the Hamiltonian formulation, it reduces to Dirac–De Witt’s canonical gravity with $\lambda =1$. In particular, the topological charged black holes in $z=5$ ${\mathrm{HL}}_6$, $z=4$ ${\mathrm{HL}}_5$, $z=3,4$ ${\mathrm{HL}}_4$, and $z=2$ ${\mathrm{HL}}_3$ with $\lambda =1$ are solved. Their asymptotical behaviors near the infinite boundary and near the horizon are explored, respectively. We also study the behavior of the topological black holes in the $(d+1)$-dimensional HL gravity with $U(1)$ gauge field in the zero temperature limit and finite temperature limit, respectively. Thermodynamics of the topological charged black holes with $\lambda =1$, including temperature, entropy, heat capacity, and free energy are evaluated.

The evolution of timelike geodesic congruences in a spherically symmetric, nonstatic, inhomogeneous spacetime representing gravitational collapse of a massless scalar field is studied. We delineate how initial values of the expansion, rotation, and shear of a congruence, as well as the spacetime curvature, influence the global behavior and focusing properties of a family of trajectories. Under specific conditions, the expansion scalar is shown to exhibit a finite jump (from negative to positive value) before focusing eventually occurs. This nonmonotonic behavior of the expansion, observed in our numerical work, is successfully explained through an analysis of the equation for the expansion. Finally, we bring out the role of the metric parameters (related to nonstaticity and spatial inhomogeneity) in shaping the overall behavior of geodesic congruences.

Large observatory for x-ray timing (LOFT) is a concept of a next-generation x-ray telescope considered in the context of the “Cosmic Vision” program of the European Space Agency. The Large Area Detector on board of LOFT will be a collimator-type telescope with an unprecedentedly large collecting area of about $10^5{\mathrm{cm}}^2$ in the energy band between 2 and 100 keV. We demonstrate that LOFT will be a powerful dark matter detector, suitable for the search of the x-ray line emission expected from decays of light dark matter particles in galactic halos. We show that LOFT will have sensitivity for dark matter line search more than an order of magnitude higher than that of all existing x-ray telescopes. In this way, LOFT will be able to provide a new insight into the fundamental problem of the nature of dark matter.

We report the results of extended high-resolution numerical integrations of the Vlasov-Poisson equation for the collapse of spherically symmetric warm dark matter (WDM) halos. For thermal relics with mass $m=1\mathrm{keV}/c^2$, we find collapsed halos with cores of size 0.1 to 0.6 kpc. The typical core is hollow, with the mass density decreasing towards the core center by almost three orders of magnitude from its maximum near the core radius $r_{\mathrm{c}}$. The core is in equilibrium with the diffused part of the halo but far from virialization. These properties are rooted in the conservation of the squared angular momentum and in the original excess, proper of WDM initial conditions, of kinetic energy in the core region. In a sample of more than one hundred simulated collapses, the values of $r_{\mathrm{c}}$ and of the core density ${\rho }_{\mathrm{c}}$ are in the range typical of dwarf spheroids, while the maximal circular velocities $V_{\max }$ are proper of small disk galaxies. The product ${\mu }_{\mathrm{c}}={\rho }_{\mathrm{c}}{r}_{\mathrm{c}}$ takes values between $116M_{\odot }/{\mathrm{pc}}^2$ and $283M_{\odot }/{\mathrm{pc}}^2$, while the surface density ${\mu }_0$, as determined from a Burkert fit, is roughly three times larger. From these data and data obtained at smaller values of $m$, we extrapolate for one particular halo ${\mu }_{\mathrm{c}}=263(308)M_{\odot }/{\mathrm{pc}}^2$ and ${\mu }_0=754(855)M_{\odot }/{\mathrm{pc}}^2$ at $m=2(3.3)\mathrm{keV}/c^2$, to be compared with the observed value $140_{-52}^{+83}{M}_{\odot }/{\mathrm{pc}}^2$. In view of the many improvements and enhancements available, we conclude that WDM is a viable solution for explaining the presence and the size of cores in low mass galaxies.

Models of inflation are tightly constrained by the PLANCK satellite data. Among them, Starobinsky’s model with an exponential type potential seems to be challenged by the recent BICEP2 results. The model is based on the existence of $R^2$ terms in the Einstein-Hilbert action, which have their origin in the conformal anomaly. Conformal (or Weyl) gravitational theories are relevant when matter fields become effectively massless; i.e. their masses are negligible in comparison with the spacetime curvature. These theories may include other, additional scalar fields. We show that their presence under general conditions does not destabilize the inflationary behavior encountered in the Starobinsky model, although the issue of the exact quantitative agreement with existing data, like the tensor to scalar ratio, rests on the choice of parameters.

In the era of second generation ground-based gravitational wave detectors, short gamma-ray bursts (GRBs) will be among the most promising astrophysical events for joint electromagnetic and gravitational wave observation. A targeted, coherent search for gravitational wave compact binary merger signals in coincidence with short GRBs was developed and used to analyze data from the first generation LIGO and Virgo instruments. In this paper, we present improvements to this search that enhance our ability to detect gravitational wave counterparts to short GRBs. Specifically, we introduce an improved method for estimating the gravitational wave background to obtain the event significance required to make detections; implement a method of tiling extended sky regions, as required when searching for signals associated to poorly localized GRBs from the Fermi Gamma-ray Burst Monitor or the InterPlanetary Network; and incorporate astrophysical knowledge about the beaming of GRB emission to restrict the search parameter space. We describe the implementation of these enhancements and demonstrate how they improve the ability to observe binary merger gravitational wave signals associated with short GRBs. A targeted, coherent GRB search provides a 25% increase in distance sensitivity, or a doubling of the event rate, for well-localized GRBs when compared with a nontargeted, coincident analysis.

A direct search for doubly charged Higgs bosons $H^{\pm \pm }$ is one of the most important probes in the Higgs triplet model, which is motivated by generation mechanisms of tiny neutrino masses. There are two major decay modes of $H^{\pm \pm }$, i.e., the same-sign dilepton decay $H^{\pm \pm }\to {\ell }^{\pm }{\ell }^{\pm }$ and the same-sign diboson decay $H^{\pm \pm }\to W^{\pm (*)}{W}^{\pm (*)}$. For the case where the former decay mode is dominant, the lower limit on the mass of $H^{\pm \pm }$ has been set at about 400 GeV by the ATLAS and CMS Collaborations. On the other hand, for the case where the latter decay mode is dominant, no dedicated search has been performed in the past. By taking into account characteristic signals of $H^{\pm \pm }$ in the diboson decay scenario at LEP and the LHC experiments, we find that the lower mass bound of 60–68 GeV can be obtained by using the same-sign dilepton search performed by the ATLAS Collaboration with $4.7{\mathrm{fb}}^{-1}$ data at the collision energy of 7 TeV. We also show that the limit can be extended up to about 85–90 GeV, assuming the integrated luminosity of $20{\mathrm{fb}}^{-1}$ and 7 TeV for the collision energy. We give detailed explanations on the decay properties of $H^{\pm \pm }$ for relatively small mass cases and also on production cross sections of $H^{\pm \pm }$ at the next-to-leading order of QCD at the LHC.

In a companion paper Detmold et al. [Phys. Rev. D 90, 114506 (2014)], lattice field theory methods are used to show that in two-color, two-flavor QCD there are stable nuclear states in the spectrum. As a commonly studied theory of composite dark matter, this motivates the consideration of possible nuclear physics in this and other composite dark sectors. In this work, early Universe cosmology and indirect detection signatures are explored for both symmetric and asymmetric dark matter, highlighting the unique features that arise from considerations of dark nuclei and associated dark nuclear processes. The present day dark matter abundance may be composed of dark nucleons and/or dark nuclei, where the latter are generated through dark nucleosynthesis. For symmetric dark matter, indirect detection signatures are possible from annihilation, dark nucleosynthesis, and dark nuclear capture and we present a novel explanation of the Galactic center gamma ray excess based on the latter. For asymmetric dark matter, dark nucleosynthesis may alter the capture of dark matter in stars, allowing for captured particles to be processed into nuclei and ejected from the star through dark nucleosynthesis in the core. Notably, dark nucleosynthesis realizes a novel mechanism for indirect detection signals of asymmetric dark matter from regions such as the Galactic center, without having to rely on a symmetric dark matter component.

We consider finite volume effects on the electromagnetic form factor of the pion. We compute the peudoscalar-vector-pseudoscalar correlator in the $\epsilon$ expansion of chiral perturbation theory up to the next-to-leading order and find a way to remove the dominant part, which comes from a contribution of the pion zero mode. Inserting nonzero momentum to relevant operators (or taking a subtraction of the correlators at different time slices), and taking an appropriate ratio of them, one can automatically cancel the zero mode’s contribution, which becomes nonperturbatively large, $\sim \mathcal{O}(100\%)$, in the $\epsilon$ regime. The remaining finite volume dependence, which comes from the nonzero momentum modes, is shown to be perturbatively small even in such an extremal case. Since the zero mode’s dominance is universal in any finite volume scaling, and we do not rely on any particular feature of the $\epsilon$ expansion, our method has a wide application to many other correlators of QCD.

Effective Polyakov line models, derived from SU(3) gauge-matter systems at finite chemical potential, have a sign problem. In this article I solve two such models, derived from SU(3) gauge-Higgs and heavy quark theories by the relative weights method, over a range of chemical potentials where the sign problem is severe. Two values of the gauge-Higgs coupling are considered, corresponding to a heavier and a lighter scalar particle. Each model is solved via the complex Langevin method, following the approach of Aarts and James, and also by a mean field technique. It is shown that where the results of mean field and complex Langevin agree, they agree almost perfectly. Where the results of the two methods diverge, it is found that the complex Langevin evolution has a branch cut crossing problem, associated with a logarithm in the action, that was pointed out by Møllgaard and Splittorff.

We consider two-color QCD with two flavors of quarks as a possible theory of composite dark matter and use lattice field theory methods to investigate nuclear spectroscopy in the spin $J=0$ and $J=1$ multibaryon sectors. We find compelling evidence that $J=1$ systems with baryon number $B=2,3$ (and their mixed meson-baryon counterparts) are bound states—the analogues of nuclei in this theory. In addition, we estimate the $\sigma$-terms of the $J=0$ and $J=1$ single baryon states which are important for the coupling of the theory to scalar currents that may mediate interactions with the visible sector.

We make a systematic investigation on the two-body nonleptonic decays $B_c\to J/\mathrm{\Psi }({\eta }_c),M$ by employing the perturbative QCD approach based on $k_T$ factorization, where $M$ is a light pseudoscalar or vector or a heavy charmed meson. We predict the branching ratios and direct $CP$ asymmetries of these $B_c$ decays and also the transverse polarization fractions of $B_c\to J/\mathrm{\Psi }V,J/\psi D_{(s)}^{*}$ decays. It is found that these decays have a large branching ratios of the order of ${10}^{-4}-{10}^{-2}$ and could be measured by the future LHCb experiment. Our predictions for the ratios of branching fractions $\frac{\mathcal{B}\mathcal{R}(B_c^{+}\to J/\mathrm{\Psi }{D}_s^{+})}{\mathcal{B}\mathcal{R}(B_c^{+}\to J/\mathrm{\Psi }{\pi }^{+})}$,$\frac{\mathcal{B}\mathcal{R}(B_c^{+}\to J/\mathrm{\Psi }{D}_s^{*+})}{\mathcal{B}\mathcal{R}(B_c^{+}\to J/\mathrm{\Psi }{D}_s^{+})}$ and $\frac{\mathcal{B}\mathcal{R}(B_c^{+}\to J/\mathrm{\Psi }{K}^{+})}{\mathcal{B}\mathcal{R}(B_c^{+}\to J/\mathrm{\Psi }{\pi }^{+})}$ are in good agreement with the data. A large transverse polarization fraction which can reach 48% is predicted in $B_c^{+}\to J/\mathrm{\Psi }{D}_s^{*+}$ decay, which is consistent with the data. We find a possible direct $CP$ violation in $B_c\to J/\psi D^{*}$ decays, which are helpful to test the $CP$ violating effects in $B_c$ decays.

We study the kinematic cusps and endpoints of processes with the “antler topology” as a way to measure the masses of the parity-odd missing particle and the intermediate parent at a high energy lepton collider. The fixed center-of-mass energy at a lepton collider makes many new physics processes suitable for the study of the antler decay topology. It also provides new kinematic observables with cusp structures, optimal for the missing mass determination. We also study realistic effects on these observables, including initial state radiation, beamstrahlung, acceptance cuts, and detector resolution. We find that the new observables, such as the reconstructed invariant mass of invisible particles and the summed energy of the observable final state particles, appear to be more stable than the commonly considered energy endpoints against realistic factors and are very efficient at measuring the missing particle mass. For the sake of illustration, we study smuon pair production and chargino pair production within the framework of the minimal supersymmetric standard model. We adopt the log-likelihood method to optimize the analysis. We find that at the 500 GeV international linear collider (ILC), a precision of approximately 0.5 GeV can be achieved in the case of smuon production with a leptonic final state, and approximately 2 GeV in the case of chargino production with a hadronic final state.

In this paper, we calculate the branching ratios and $CP$-violating asymmetries of the five ${\overline{B}}_s^0\to ({\pi }^0{\eta }^{(\prime )},{\eta }^{(\prime )}{\eta }^{(\prime )})$ decays, by employing the perturbative QCD (pQCD) factorization approach and with the inclusion of all currently known next-to-leading order (NLO) contributions. We find that (a) the NLO contributions can provide about 100% enhancements to the LO pQCD predictions for the decay rates of ${\overline{B}}_s^0\to \eta {\eta }^{\prime }$ and ${\eta }^{\prime }{\eta }^{\prime }$ decays, but result in small changes to $\mathrm{Br}({\overline{B}}_s\to {\pi }^0{\eta }^{(\prime )})$ and $\mathrm{Br}({\overline{B}}_s\to \eta \eta )$; (b) the newly known NLO twist-2 and twist-3 contributions to the relevant form factors can provide about 10% enhancements to the decay rates of the considered decays; (c) for ${\overline{B}}_s\to {\pi }^0{\eta }^{(\prime )}$ decays, their direct $CP$-violating asymmetries ${\mathcal{A}}_f^{\text{dir}}$ could be enhanced significantly by the inclusion of the NLO contributions; and (d) the pQCD predictions for $\mathrm{Br}({\overline{B}}_s\to \eta {\eta }^{(\prime )})$ and $\mathrm{Br}({\overline{B}}_s\to {\eta }^{\prime }{\eta }^{\prime })$ can be as large as $4\times {10}^{-5}$, which may be measurable at LHCb or the forthcoming Super-B experiments.

There exists a long-standing disagreement between bubble chamber measurements of the single pion production channel ${\nu }_{\mu }p\to {\mu }^{-}p{\pi }^{+}$ from the Argonne and Brookhaven National Laboratories. We digitize and reanalyze data from both experiments to produce cross-section ratios for various interaction channels, for which the flux uncertainties cancel, and find good agreement between the experiments. By multiplying the cross-section ratio by the well-understood charged-current quasielastic cross section on free nucleons, we extract single-pion production cross sections which do not depend on the flux normalization predictions. The ${\nu }_{\mu }p\to {\mu }^{-}p{\pi }^{+}$ cross sections we extract show good agreement between the ANL and BNL data sets.

Measurements of spin correlation in top quark pair production are presented using data collected with the ATLAS detector at the LHC with proton-proton collisions at a center-of-mass energy of 7 TeV, corresponding to an integrated luminosity of $4.6{\mathrm{fb}}^{-1}$. Events are selected in final states with two charged leptons and at least two jets and in final states with one charged lepton and at least four jets. Four different observables sensitive to different properties of the top quark pair production mechanism are used to extract the correlation between the top and antitop quark spins. Some of these observables are measured for the first time. The measurements are in good agreement with the Standard Model prediction at next-to-leading-order accuracy.

A measurement of the production processes of the recently discovered Higgs boson is performed in the two-photon final state using $4.5{\mathrm{fb}}^{-1}$ of proton-proton collisions data at $\sqrt{s}=7\mathrm{TeV}$ and $20.3{\mathrm{fb}}^{-1}$ at $\sqrt{s}=8\mathrm{TeV}$ collected by the ATLAS detector at the Large Hadron Collider. The number of observed Higgs boson decays to diphotons divided by the corresponding Standard Model prediction, called the signal strength, is found to be $\mu =1.17\pm 0.27$ at the value of the Higgs boson mass measured by ATLAS, $m_H=125.4\mathrm{GeV}$. The analysis is optimized to measure the signal strengths for individual Higgs boson production processes at this value of $m_H$. They are found to be ${\mu }_{\mathrm{ggF}}=1.32\pm 0.38$, ${\mu }_{\mathrm{VBF}}=0.8\pm 0.7$, ${\mu }_{WH}=1.0\pm 1.6$, ${\mu }_{ZH}={0.1}_{-0.1}^{+3.7}$, and ${\mu }_{t\overline{t}H}={1.6}_{-1.8}^{+2.7}$, for Higgs boson production through gluon fusion, vector-boson fusion, and in association with a $W$ or $Z$ boson or a top-quark pair, respectively. Compared with the previously published ATLAS analysis, the results reported here also benefit from a new energy calibration procedure for photons and the subsequent reduction of the systematic uncertainty on the diphoton mass resolution. No significant deviations from the predictions of the Standard Model are found.

We use $(121\pm 1)$ million $\mathrm{{\rm Y}}(3S)$ and $(98\pm 1)$ million $\mathrm{{\rm Y}}(2S)$ mesons recorded by the BABAR detector at the PEP-II $e^{+}{e}^{-}$ collider at SLAC to perform a study of radiative transitions involving the ${\chi }_{b\mathrm{J}}(1P,2P)$ states in exclusive decays with ${\mu }^{+}{\mu }^{-}\gamma \gamma$ final states. We reconstruct twelve channels in four cascades using two complementary methods. In the first we identify both signal photon candidates in the electromagnetic calorimeter (EMC), employ a calorimeter timing-based technique to reduce backgrounds, and determine branching-ratio products and fine mass splittings. These results include the best observational significance yet for the ${\chi }_{b0}(2P)\to \gamma \mathrm{{\rm Y}}(2S)$ and ${\chi }_{b0}(1P)\to \gamma \mathrm{{\rm Y}}(1S)$ transitions. In the second method, we identify one photon candidate in the EMC and one which has converted into an $e^{+}{e}^{-}$ pair due to interaction with detector material, and we measure absolute product branching fractions. This method is particularly useful for measuring $\mathrm{{\rm Y}}(3S)\to \gamma {\chi }_{b1,2}(1P)$ decays. Additionally, we provide the most up-to-date derived branching fractions, matrix elements and mass splittings for ${\chi }_b$ transitions in the bottomonium system. Using a new technique, we also measure the two lowest-order spin-dependent coefficients in the nonrelativistic QCD Hamiltonian.

We investigate the pressure of the pion, which should be equal to zero to ensure the stability of the pion, within the framework of the chiral quark model beyond the chiral limit. The pressure of the pion vanishes nontrivially by the Gell-Mann-Oakes-Renner relation within the present framework. This implies that the stability of the pion might be deeply rooted in spontaneous chiral symmetry breaking. We also discuss physical quantities relevant to the energy-momentum tensor operator.

We examine relative entropy in the context of the higher spin/CFT duality. We consider 3D bulk configurations in higher spin gravity which are dual to the vacuum and a high temperature state of a CFT with $\mathcal{W}$-algebra symmetries in the presence of a chemical potential for a higher spin current. The relative entropy between these states is then evaluated using the Wilson line functional for holographic entanglement entropy. In the limit of small entangling intervals, the relative entropy should vanish for a generic quantum system. We confirm this behavior by showing that the difference in the expectation values of the modular Hamiltonian between the states matches with the difference in the entanglement entropy in the short-distance regime. Additionally, we compute the relative entropy of states corresponding to smooth solutions in the $SL(2,\mathbb{Z})$ family with respect to the vacuum.