In this article we consider the second law of black holes (and other causal horizons) in theories where the gravitational action is an arbitrary function of the Lovelock densities. We show that there exists an entropy which increases locally, for linearized perturbations to regular Killing horizons. In addition to a classical increase theorem, we also prove a generalized second law for semiclassical, minimally coupled matter fields.

We show that there is a direct relation between upper limits on (or potential future measurements of) the $m=2$ quadrupole moments of slowly rotating neutron stars and the $l=m=2$ deformation of the star’s surface, in full general relativity, to first order in the perturbation. This relation only depends on the star’s structure through its mass and radius. All one has to assume about the star’s constituents is that the stress-energy tensor at its surface is that of a perfect fluid, which will be true with good accuracy in almost all the situations of interest, and that the magnetic field configuration there is force free, which is likely to be a good approximation. We then apply this relation to the stars which have direct LIGO/Virgo bounds on their $m=2$ quadrupole moment, below the spin-down limit, and compare with the expected surface deformations due to rotation. In particular, we find that LIGO observations have constrained the Crab pulsar’s $l=m=2$ surface deformation to be smaller than its $l=2$, $m=0$ deformation due to rotation, for all the causal equations of state we consider, a statement that could not have been made just using the upper bounds on the $l=m=2$ deformation from electromagnetic observations.

We explore the systematic uncertainties of using type Ia supernovae (SNe Ia) as cosmological probes, using the Supernova Legacy Survey Three Year data (SNLS3). We focus on studying the possible evolution of the stretch-luminosity parameter $\alpha$ and the color-luminosity parameter $\beta$, by allowing $\alpha$ and $\beta$ to be function of redshift, $z$. We find no evidence for the redshift evolution of $\alpha$. We find that without flux-averaging SNe, $\beta$ is consistent with being a constant when only statistical uncertainties are included, but it increases significantly with $z$ when systematic uncertainties are also included. The evolution of $\beta$ becomes marginal when all the SNe are flux-averaged, and $\beta$ is consistent with being a constant when only SNe at $z\ge 0.04$ are flux-averaged. Our results are insensitive to the light-curve fitter used to derive the SNLS3 sample, or the functional form of $\alpha (z)$ and $\beta (z)$ assumed. It is likely that the apparent evolution of $\beta$ with $z$ for SNe without flux-averaging is a consequence of unknown systematic effects; flux-averaging reduces the impact of these effects by averaging them within each redshift bin. Assuming constant $\alpha$ and $\beta$, we find that the flux-averaging of SNe has a significant impact on the distance-redshift relation.

The current accelerated expansion of our Universe could be due to an unknown energy component with negative pressure (dark energy) or a modification to general relativity (modified gravity). On the other hand, recently, warm dark matter remarkably rose as an alternative of cold dark matter. Obviously, it is of interest to distinguish these different types of models. In fact, many attempts have been made in the literature. However, in the present work, we show that warm dark matter, modified gravity, and coupled cold dark matter form a trinity; namely, they are indistinguishable by using the cosmological observations of both cosmic expansion history and growth history. Therefore, to break this degeneracy, the other complementary probes beyond the ones of cosmic expansion history and growth history are required.

We present an exhaustive analysis on the background inflationary solutions of the chromo-natural model. We show that starting from an arbitrary axion field value ${\chi }_0\in (0,f\pi )$, it is possible to have slow-roll inflation with enough number of e-folds and determine the allowed region of the parameters corresponding to each ${\chi }_0$ value. Having the available parameter space, we then study the behavior of the solutions with respect to the initial value of the axion field.

Light scalar fields present during inflation can lead to interesting observable signatures, especially in models with nonequilibrium reheating dynamics. We study a supersymmetric hybrid inflation model with a third scalar whose lightness is protected by symmetry, using analytical and numerical techniques, and demonstrate that the amplitude, the spectral index and the non-Gaussianity parameter $f_{\mathrm{NL}}$ of the primordial curvature perturbation are within the Planck observational bounds for suitable parameter values.

Grating reflectors have been repeatedly discussed to improve the noise performance of metrological applications due to the reduction or absence of any coating material. So far, however, no quantitative estimate on the thermal noise of these reflective structures exists. In this work we present a theoretical calculation of a grating reflector’s noise. We further apply it to a proposed third generation gravitational wave detector. Depending on the grating geometry, the grating material, and the temperature, we obtain a thermal noise decrease by up to a factor of 10 compared to conventional dielectric mirrors. Thus the use of grating reflectors can substantially improve the noise performance in metrological applications.

We consider the imprint of super-radiant instabilities of nonevaporating primordial black holes (PBHs) on the spectrum of the cosmic microwave background (CMB). In the radiation-dominated era, PBHs are surrounded by a roughly homogeneous cosmic plasma which endows photons with an effective mass through the plasma frequency. In this setting, spinning PBHs are unstable to a spontaneous spindown through the well-known “black hole bomb” mechanism. At the linear level, the photon density is trapped by the effective photon mass and grows exponentially in time due to super-radiance. As the plasma density declines due to cosmic expansion, the associated energy around PBHs is released and dissipated in the CMB. We evaluate the resulting spectral distortions of the CMB in the redshift range ${10}^3\lesssim z\lesssim 2\times {10}^6$. Using the existing COBE/FIRAS bounds on CMB spectral distortions, we derive upper limits on the fraction of dark matter that can be associated with spinning PBHs in the mass range ${10}^{-8}{M}_{\odot }\lesssim M\lesssim 0.2M_{\odot }$. For maximally spinning PBHs, our limits are much tighter than those derived from microlensing or other methods. Future data from the proposed PIXIE mission could improve our limits by several orders of magnitude.

We discuss both the minimal supersymmetric Standard Model (MSSM) and next to MSSM scenarios in which the lightest Higgs boson with $m_h=98\mathrm{GeV}$ is consistent with the small excess ($\sim 2.3\sigma$) observed at the LEP in $e^{+}{e}^{-}\to Zh$, with the $h\to b\overline{b}$ process and the heavier Higgs boson of mass close to 125 GeV as the observed candidate of the SM Higgs-like particle at the LHC. We show the allowed regions in the nondecoupling Higgs zone of MSSM parameter space which are consistent with several low energy constraints coming from heavy flavor physics, the latest experimental data on Higgs signals, and the lower limit on superparticle masses from 7 and 8 TeV LHC runs. We also implement the constraints from the relic density of the cold dark matter as obtained from the recent PLANCK data. Additionally, we discuss the possibility of observing the light Higgs boson of mass 98 GeV at the 14 TeV LHC run via $pp\to Vh$, with $h\to b\overline{b}$ using the technique of jet substructure. Our analysis shows that at a 14 TeV LHC run with $300{\mathrm{fb}}^{-1}$ luminosity the signal efficiency of such a light Higgs boson is at most $2.5\sigma$. Finally, we make a comment on the prospect of the proposed $e^{+}{e}^{-}$ International Linear Collider to discover/exclude this light Higgs boson.

New vectorlike quarks with electric charge $2/3$ and $-1/3$ can be singly produced at hadron colliders through the exchange of a color octet vector resonance in models of strong electroweak symmetry breaking. We show that electroweak symmetry breaking effects can have a significant impact on the decay pattern of these new quarks. In particular, single production of charge $-1/3$ fermion resonances, mediated by a color octet vector resonance, typically results in an $Hb\overline{b}$ final state with a sizeable cross section and very distinctive kinematics. We consider the leading $H\to b\overline{b}$ decay and show that the $4b$ signal can be very efficiently disentangled from the background: heavy octet masses of up to 3 TeV can be tested with the data already collected at the LHC and up to 5 TeV with an integrated luminosity of $100{\mathrm{fb}}^{-1}$ at $\sqrt{s}=14\mathrm{TeV}$. We also discuss the kinematical differences between the $Hb\overline{b}$ production in models of strong electroweak symmetry breaking and supersymmetric models and the implications on the phenomenology of nonminimal composite Higgs models.

The Belle Collaboration recently discovered two resonances, $Z_b(10610)$ and $Z_b(10650)$—denoted $Z_b$ and $Z_b^{\prime }$—in the decays ${\rm Y}(5S)\to {\rm Y}(nS){\pi }^{+}{\pi }^{-}$ for $n=1$, 2, or 3, and ${\rm Y}(5S)\to h_b(mP){\pi }^{+}{\pi }^{-}$ for $m=1$ or 2. These resonances lie very close to the $B^{*}\overline{B}$ and $B^{*}{\overline{B}}^{*}$ thresholds, respectively. A recent Belle analysis of the three-body decays ${\rm Y}(5S)\to [B^{(*)}{\overline{B}}^{(*)}{]}^{\mp }{\pi }^{\pm }$ gives further evidence for the existence of these states. In this paper we analyze this decay using an effective theory of $B$ mesons interacting via strong short-range interactions. Some parameters in this theory are constrained using existing data on ${\rm Y}(5S)\to B^{(*)}{\overline{B}}^{(*)}$ decays, which requires the inclusion of heavy quark spin symmetry violating operators. We then calculate the differential distribution for ${\rm Y}(5S)\to B^{(*)}{\overline{B}}^{(*)}\pi$ as a function of the invariant mass of the $B^{(*)}{\overline{B}}^{(*)}$ pair, obtaining qualitative agreement with experimental data. We also calculate angular distributions in the decay ${\rm Y}(5S)\to Z_b^{(\prime )}\pi$ which are sensitive to the molecular character of the $Z_b^{(\prime )}$.

We investigate the energy evolution of the azimuthal spin asymmetries in semi-inclusive hadron production in deep inelastic scattering (SIDIS) and Drell-Yan lepton pair production in $pp$ collisions. The scale dependence is evaluated by applying an approximate solution to the Collins-Soper-Sterman evolution equation at one-loop order, which is adequate for moderate $Q^2$ variations. This describes well the unpolarized cross sections for the SIDIS and Drell-Yan process in the $Q^2$ range of $2.4–100{\mathrm{GeV}}^2$. A combined analysis of the Sivers asymmetries in SIDIS from HERMES and COMPASS experiments and the predictions for the Drell-Yan process at RHIC at $\sqrt{S}=200\mathrm{GeV}$ are presented. We further extend to the Collins asymmetries and find, for the first time, a consistent description for HERMES/COMPASS and BELLE experiments with the evolution effects. We emphasize an important test of the evolution effects by studying di-hadron azimuthal asymmetry in $e^{+}{e}^{-}$ annihilation at moderate energy range, such as at BEPC at $\sqrt{S}=4.6\mathrm{GeV}$.

The Froissart-Martin bound for total $\pi \pi$ scattering cross sections is reconsidered in the light of QCD properties such as spontaneous chiral symmetry breaking and the counting rules for a large number of colors ${\mathrm{N}}_{\mathrm{c}}$.

Effective $\Delta S=1$ four-fermion operators involving left- and right-handed currents are relevant in left-right gauge extensions of the Standard Model and scalar extension of the Yukawa sector. They induce $K\to \pi \pi$ decays which are strictly constrained by experimental data, typically resulting in strong bounds on the new physics scales or parameters. We evaluate the $K\to \pi \pi$ hadronic matrix elements of such operators within the phenomenological framework of the chiral quark model. The results are consistent with the estimates used in a previous work on TeV scale left-right symmetry, thus confirming the conclusions obtained there.

Currently, not enough is known to determine the hadron distribution amplitudes (DAs)—which are universal physical quantities in the high-energy processes involving hadrons—in order to apply perturbative QCD to exclusive processes. Even for the simplest pion, one cannot discriminate between different DA models. Conversely, one expects that processes involving pions can in principle provide strong constraints on the pion DA. For example, the pion-photon transition form factor (TFF) can get accurate information about the pion wave function or DA due to the single pion in this process. However, the data from Belle and BABAR show a big difference regarding this TFF in high-$Q^2$ regions; at present, they are unable to determine the pion DA. In the present paper, we think it is still possible to determine the pion DA as long as we perform a combined analysis of the existing data of the processes involving pions, such as $\pi \to \mu \overline{\nu }$, ${\pi }^0\to \gamma \gamma$, $B\to \pi l\nu$, $D\to \pi l\nu$, etc. Based on the revised light-cone harmonic oscillator model, a convenient DA model is suggested, whose parameter $B$—which dominates its longitudinal behavior for ${\varphi }_{\pi }(x,{\mu }^2)$—can be determined in a definite range by these processes. A light-cone sum rule analysis of the semileptonic processes $B\to \pi l\nu$ and $D\to \pi l\nu$ leads to a narrow region $B=[0.01,0.14]$, which indicates a slight deviation from the asymptotic DA. Then, one can predict the behavior of the pion-photon TFF in high-$Q^2$ regions which can be tested in future experiments. This method provides the possibility that the pion DA will be finally determined by a global fit.

The production of a single top quark in association with an isolated photon probes the electromagnetic coupling structure of the top quark. We investigate the sensitivity of kinematical distributions at the LHC in single-top-plus-photon production in view of a detection of anomalous electric and magnetic dipole moments of the top quark.

The energy dependence of the single-transverse-spin asymmetry, $A_N$, and the cross section for neutron production at very forward angles were measured in the PHENIX experiment at the Relativistic Heavy Ion Collider for polarized $p+p$ collisions at $\sqrt{s}=200\mathrm{GeV}$. The neutrons were observed in forward detectors covering an angular range of up to 2.2 mrad. We report results for neutrons with a momentum fraction of $x_F=0.45$ to 1.0. The energy dependence of the measured cross sections were consistent with $x_F$ scaling, compared to measurements by an experiment at the Intersecting Storage Ring, which measured neutron production in unpolarized $p+p$ collisions at $\sqrt{s}=30.6–62.7\mathrm{GeV}$. The cross sections for large $x_F$ neutron production for $p+p$ collisions, as well as those in $e+p$ collisions measured at the Hadron-Electron Ring Accelerator, are described by a pion exchange mechanism. The observed forward neutron asymmetries were large, reaching $A_N=-0.08\pm 0.02$ for $x_F=0.8$; the measured backward asymmetries, for negative $x_F$, were consistent with zero. The observed asymmetry for forward neutron production is discussed within the pion exchange framework, with interference between the spin-flip amplitude due to the pion exchange and nonflip amplitudes from all Reggeon exchanges. Within the pion exchange description, the measured neutron asymmetry is sensitive to the contribution of other Reggeon exchanges even for small amplitudes.

We present a search for the decay $B^{+}\to {\tau }^{+}\nu$ using $467.8\times {10}^6$ $B\overline{B}$ pairs collected at the ${\rm Y}(4S)$ resonance with the BABAR detector at the SLAC PEP-II $B$-Factory. We select a sample of events with one completely reconstructed $B^{-}$ in the hadronic decay mode ($B^{-}\to D^{(*)0}{X}^{-}$ and $B^{-}\to J/\psi X^{-}$). We examine the rest of the event to search for a $B^{+}\to {\tau }^{+}\nu$ decay. We identify the ${\tau }^{+}$ lepton in the following modes: ${\tau }^{+}\to e^{+}\nu \overline{\nu }$, ${\tau }^{+}\to {\mu }^{+}\nu \overline{\nu }$, ${\tau }^{+}\to {\pi }^{+}\overline{\nu }$ and ${\tau }^{+}\to {\rho }^{+}\overline{\nu }$. We find an excess of events with respect to the expected background, which excludes the null signal hypothesis at the level of $3.8\sigma$ (including systematic uncertainties) and corresponds to a branching fraction value of $\mathcal{B}(B^{+}\to {\tau }^{+}\nu )=({1.83}_{-0.49}^{+0.53}(\mathrm{stat})\pm 0.24(\mathrm{syst}))\times {10}^{-4}$.

The electronic density in the Sun’s inner core is inferred from the ${}^8\mathrm{B}$, ${}^7\mathrm{Be}$ and pep neutrino flux measurements of the Super-Kamiokande, SNO and Borexino experiments. We have developed a new method in which we use the KamLAND detector determinations of the neutrino fundamental oscillation parameters: the mass difference and the vacuum oscillation angle. Our results suggest that the solar electronic density in the Sun’s inner core (for a radius smaller than 10% of the solar radius) is well above the current prediction of the standard solar model, and by as much as 25%. A potential confirmation of these preliminary findings can be achieved when neutrino detectors are able to reduce the error of the electron-neutrino survival probability by a factor of 15.