The renormalizable coloron model is the minimal extension of the standard model color sector, in which the color gauge group is enlarged to $SU(3{)}_{1c}\times SU(3{)}_{2c}$. In this paper we discuss the constraints on this model derived from the requirements of vacuum stability, tree-level unitarity, and electroweak precision measurements from LHC measurements of the properties of the observed Higgs-like scalar boson and from LHC limits on additional Higgs-like bosons decaying to dibosons. The combination of these theoretical and experimental considerations strongly constrains the allowed parameter space.

If heavy neutrinos with mass $m_{{\nu }_H}\ge 2m_e$ are produced in the Sun via the decay ${}^8\mathrm{B}\to {}^8\mathrm{Be}+e^{+}+{\nu }_H$ in a side branch of the $pp$ chain, they would undergo the observable decay into an electron, a positron and a light neutrino ${\nu }_H\to {\nu }_L+e^{+}+e^{-}$. In the present work Borexino data are used to set a bound on the existence of such decays. We constrain the mixing of a heavy neutrino with mass $1.5\mathrm{MeV}\le m_{{\nu }_H}\le 14\mathrm{MeV}$ to be $|U_{eH}{|}^2\le ({10}^{-3}-4\times {10}^{-6})$, respectively. These are tighter limits on the mixing parameters than obtained in previous experiments at nuclear reactors and accelerators.

We show that the requirement that a SU(N) Yang-Mills action (gauge fixed in a linear covariant gauge) is invariant under both the Becchi-Rouet-Stora-Tyutin (BRST) symmetry as well as the corresponding anti-BRST symmetry, automatically implies that the theory is quantized in the (linear covariant) background field method (BFM) gauge. Thus, the BFM and its associated background Ward identity naturally emerge from anti-BRST invariance of the theory and need not be introduced as an ad hoc gauge fixing procedure. Treating ghosts and antighosts on an equal footing, as required by a BRST-anti-BRST invariant formulation of the theory, gives also rise to a local antighost equation that together with the local ghost equation completely resolves the algebraic structure of the ghost sector for any value of the gauge fixing parameter. We finally prove that the background fields are stationary points of the background effective action obtained when the quantum fields are integrated out.

We study, in the framework of open quantum systems, the dynamics of a radially polarizable two-level atom in multipolar coupling to fluctuating vacuum electromagnetic fields which is placed at a fixed radial distance outside a radiating Schwarzschild black hole, and we analyze the transition rates between atomic energy levels and the steady state the atom is driven to. We find that the atom always thermalizes toward a steady state at an effective temperature between zero and the Hawking temperature of the black hole. Remarkably, the thermalization temperature depends on the transition frequency of the atom, so that atoms with different transition frequencies essentially thermalize to different temperatures. This counterintuitive behavior is however in close analogy to what happens for a two-level atom in a stationary environment out of thermal equilibrium near a dielectric body of certain geometry and dielectric permittivity. Our results thereby suggest in principle a possible analogue system, using engineered materials with certain desired dielectric properties to verify features of Hawking radiation in tabletop experiments.

We present a quantum theory of black hole (and other) horizons, in which the standard assumptions of complementarity are preserved without contradicting information theoretic considerations. After the scrambling time, the quantum mechanical structure of a black hole becomes that of an eternal black hole at the microscopic level. In particular, the stretched horizon degrees of freedom and the states entangled with them can be mapped into the near-horizon modes in the two exterior regions of an eternal black hole, whose mass is taken to be that of the evolving black hole at each moment. Salient features arising from this picture include (i) the number of degrees of freedom needed to describe a black hole is $e^{\mathcal{A}/2l_{\mathrm{P}}^2}$, where $\mathcal{A}$ is the area of the horizon; (ii) black hole states having smooth horizons, however, span only an $e^{\mathcal{A}/4l_{\mathrm{P}}^2}$-dimensional subspace of the relevant $e^{\mathcal{A}/2l_{\mathrm{P}}^2}$-dimensional Hilbert space; (iii) internal dynamics of the horizon is such that an infalling observer finds a smooth horizon with a probability of 1 if a state stays in this subspace. We identify the structure of local operators responsible for describing semiclassical physics in the exterior and interior spacetime regions and show that this structure avoids the arguments for firewalls—the horizon can keep being smooth throughout the evolution. We discuss the fate of infalling observers under various circumstances, especially when the observers manipulate degrees of freedom before entering the horizon, and we find that an observer can never see a firewall by making a measurement on early Hawking radiation. We also consider the presented framework from the viewpoint of an infalling reference frame and argue that Minkowski-like vacua are not unique. In particular, the number of true Minkowski vacua is infinite, although the label discriminating these vacua cannot be accessed in usual nongravitational quantum field theory. An application of the framework to de Sitter horizons is also discussed.

Based on a physical argument, we derive a new analytic formula for the amplitude of density perturbation at the threshold of primordial black hole formation in the Universe dominated by a perfect fluid with the equation of state $p=w\rho c^2$ for $w\ge 0$. The formula gives ${\delta }_{Hc}^{\mathrm{UH}}={sin}^2[\pi \sqrt{w}/(1+3w)]$ and ${\tilde{\delta }}_c=[3(1+w)/(5+3w)]{sin}^2[\pi \sqrt{w}/(1+3w)]$, where ${\delta }_{Hc}^{\mathrm{UH}}$ and ${\tilde{\delta }}_c$ are the amplitude of the density perturbation at the horizon crossing time in the uniform Hubble slice and the amplitude measure used in numerical simulations, respectively, while the conventional one gives ${\delta }_{Hc}^{\mathrm{UH}}=w$ and ${\tilde{\delta }}_c=3w(1+w)/(5+3w)$. Our formula shows a much better agreement with the result of recent numerical simulations both qualitatively and quantitatively than the conventional formula. For a radiation fluid, our formula gives ${\delta }_{Hc}^{\mathrm{UH}}={sin}^2(\sqrt{3}\pi /6)\simeq 0.6203$ and ${\tilde{\delta }}_c=(2/3){sin}^2(\sqrt{3}\pi /6)\simeq 0.4135$. We also discuss the maximum amplitude and the cosmological implications of the present result.

One of the most remarkable phenomena in loop quantum cosmology is that, at least for homogeneous cosmological models, the big bang is replaced with a big bounce that connects our Universe with a previous branch without passing through a cosmological singularity. The goal of this work is to study the existence of singularities in loop quantum cosmology, including inhomogeneities, and check whether the behavior obtained in the purely homogeneous setting continues to be valid. With this aim, we focus our attention on the three-torus Gowdy cosmologies with linearly polarized gravitational waves and use effective dynamics to carry out the analysis. For this model, we prove that all the potential cosmological singularities are avoided, generalizing the results about resolution of singularities to this scenario with inhomogeneities. We also demonstrate that, if a bounce in the (Bianchi background) volume occurs, the inhomogeneities increase the value of this volume at the bounce with respect to its counterpart in the homogeneous case.

We study the partition function of the free $\mathrm{Sp}(N)$ conformal field theory (CFT) recently conjectured to be dual to asymptotically de Sitter higher-spin gravity in four dimensions. We compute the partition function of this CFT on a round sphere as a function of a finite mass deformation, on a squashed sphere as a function of the squashing parameter, and on an ${\mathrm{S}}^2\times {\mathrm{S}}^1$ geometry as a function of the relative size of ${\mathrm{S}}^2$ and ${\mathrm{S}}^1$. We find that the partition function is divergent at large negative mass in the first case, and for small ${\mathrm{S}}^1$ in the third case. It is globally peaked at zero squashing in the second case. Through the duality this partition function contains information about the wave function of the universe. We show that the divergence at small ${\mathrm{S}}^1$ occurs also in Einstein gravity if certain complex solutions are included, but the divergence in the mass parameter is new. We suggest an interpretation for this divergence as indicating an instability of de Sitter space in higher-spin gravity, consistent with general arguments that de Sitter space cannot be stable in quantum gravity.

We present a series of new solutions in five-dimensional Einstein-Maxwell-Chern-Simons theory with an arbitrary Chern-Simons coupling $\gamma$ and a cosmological constant $\Lambda$. For general $\gamma$ and $\Lambda$ we give various generalizations of the Bertotti-Robinson solutions supported by electric and magnetic fluxes, some of which presumably describe the near-horizon regions of black strings or black rings. Among them there is a solution which could apply to the horizon of a topological anti–de Sitter black ring in gauged minimal supergravity. Others are horizonless and geodesically complete. We also construct extremal asymptotically flat multistring solutions for $\Lambda =0$ and arbitrary $\gamma$.

By the use of the gauge-invariant variables proposed by Kodama and Ishibashi, we obtain the most general perturbation equations in the ($m+n$)-dimensional spacetime with a warped product metric. These equations do not depend on the spectral expansions of the Laplace-type operators on the $n$-dimensional Einstein manifold. These equations enable us to have a complete gauge-invariant perturbation theory and a well-defined spectral expansion for all modes, and the gauge invariance is kept for each mode. By studying perturbations of some projections of Weyl tensor in the case of $m=2$, we define three Teukolsky-like gauge-invariant variables and obtain the perturbation equations of these variables by considering the perturbations of the Penrose wave equations in the ($2+n$)-dimensional Einstein spectime. In particular, we find the relations between the Teukolsky-like gauge-invariant variables and the Kodama–Ishibashi gauge-invariant variables. These relations imply that the Kodama–Ishibashi gauge-invariant variables all come from the perturbations of the Weyl tensor of the spacetime.

Radio observations of the Ursa Major II dwarf spheroidal galaxy obtained using the Green Bank Telescope are used to place bounds on weakly interacting massive particle (WIMP) dark matter properties. Dark matter annihilation releases energy in the form of charged particles which emit synchrotron radiation in the magnetic field of the dwarf galaxy. We compute the expected synchrotron radiation intensity from WIMP annihilation to various primary channels. The predicted synchrotron radiation is sensitive to the distribution of dark matter in the halo, the diffusion coefficient $D_0$, the magnetic field strength $B$, the particle mass $m_{\chi }$, the annihilation rate $⟨{\sigma }_{\mathrm{a}}v⟩$, and the annihilation channel. Limits on $⟨{\sigma }_{\mathrm{a}}v⟩$, $m_{\chi }$, $B$, and $D_0$ are obtained for the $e^{+}{e}^{-}$, ${\mu }^{+}{\mu }^{-}$, ${\tau }^{+}{\tau }^{-}$, and $b\overline{b}$ channels. Constraints on these parameters are sensitive to uncertainties in the measurement of the dark matter density profile. For the best fit halo parameters derived from stellar kinematics, we exclude 10 GeV WIMPs annihilating directly to $e^{+}{e}^{-}$ at the thermal rate $⟨{\sigma }_{\mathrm{a}}v⟩=2.18\times {10}^{-26}{\mathrm{cm}}^3/\mathrm{s}$ at the $2\sigma$ level, for $B>0.6\mu \mathrm{G}$ ($1.6\mu \mathrm{G}$) and $D_0=0.1(1.0)\times$ the Milky Way diffusion value.

An entropic-force scenario, i.e., entropic cosmology, assumes that the horizon of the Universe has an entropy and a temperature. In the present paper, in order to examine entropic cosmology, we derive entropic-force terms not only from the Bekenstein entropy but also from a generalized black-hole entropy proposed by Tsallis and Cirto [Eur. Phys. J. C 73, 2487 (2013)]. Unlike the Bekenstein entropy, which is proportional to area, the generalized entropy is proportional to volume because of appropriate nonadditive generalizations. The entropic-force term derived from the generalized entropy is found to behave as if it were an extra driving term for bulk viscous cosmology, in which a bulk viscosity of cosmological fluids is assumed. Using an effective description similar to bulk viscous cosmology, we formulate the modified Friedmann, acceleration, and continuity equations for entropic cosmology. Based on this formulation, we propose two entropic-force models derived from the Bekenstein and generalized entropies. In order to examine the properties of the two models, we consider a homogeneous, isotropic, and spatially flat universe, focusing on a single-fluid-dominated universe. The two entropic-force models agree well with the observed supernova data. Interestingly, the entropic-force model derived from the generalized entropy predicts a decelerating and accelerating universe, as for a fine-tuned standard $\Lambda \mathrm{CDM}$ (lambda cold dark matter) model, whereas the entropic-force model derived from the Bekenstein entropy predicts a uniformly accelerating universe.

We investigate what can be said about the interaction of scalar fields with Abelian gauge fields during a quasi-de Sitter phase of expansion and under the assumption that the electric and the magnetic susceptibilities do not coincide. The duality symmetry, transforming the magnetic susceptibility into the inverse of the electric susceptibility, exchanges the magnetic and electric power spectra. The mismatch between the two susceptibilities determines an effective refractive index affecting the evolution of the canonical fields. The constraints imposed by the duration of the inflationary phase and by the magnetogenesis requirements pin down the rate of variation of the susceptibilities that is consistent with the observations of the magnetic field strength over astrophysical and cosmological scales but avoids backreaction problems. The parameter space of this magnetogenesis scenario is wider than in the case in which the susceptibilities are equal, as it happens when the inflaton or some other spectator field is solely coupled to the standard gauge kinetic term.

We construct a model for galactic dark matter that arises as a solution of Einstein gravity and is a Bertrand space-time matched with an external Schwarzschild metric. This model can explain galactic rotation curves. Further, we study gravitational lensing in these space-times, and in particular we consider Einstein rings using the strong lensing formalism of Virbhadra and Ellis. Our results are in good agreement with observational data and indicate that under certain conditions, gravitational lensing effects from galactic dark matter may be similar to that from Schwarzschild backgrounds.

We have studied charged current ${\overline{\nu }}_l$ induced one pion production from ${}^{12}\mathrm{C}$ and ${}^{16}\mathrm{O}$ nuclear targets at MiniBooNE and atmospheric antineutrino energies. The calculations have been done for the incoherent pion production process as well as for the pions coming from the hyperons in the quasielastic production of $\Lambda$ and $\Sigma$. The calculations are done in the local density approximation. For the inelastic processes the calculations have been done in the $\Delta$ dominance model, and we take into account the effect of Pauli blocking, Fermi motion of the nucleon, and renormalization of $\Delta$ properties in the nuclear medium. The effect of final state interaction (FSI) of pions is also taken into account. For the hyperon production, the nuclear medium effects due to Fermi motion and FSI effects due to hyperon-nucleon scattering have been taken into account. These results may be quite useful in the analysis of SciBooNE, MicroBooNE, $\mathrm{MINER}\nu \mathrm{A}$, and ArgoNeuT experiments when the pion analysis is done by using antineutrino beams.

We propose a renormalizable multi-Higgs model with $A_4\otimes Z_2\otimes Z_2^{\prime }$ symmetry accounting for the experimental deviation from the tribimaximal mixing pattern of the neutrino mixing matrix. In this framework we study the charged lepton and neutrino masses and mixings. The light neutrino masses are generated via a radiative seesaw mechanism, which involves a single heavy Majorana neutrino and neutral scalars running in the loops. The obtained neutrino mixings and mass squared splittings are in good agreement with the neutrino oscillation experimental data for both normal and inverted hierarchy. The model predicts an effective Majorana neutrino mass $m_{\beta \beta }=4$ and 50 meV for the normal and the inverted neutrino spectrum, respectively. The model also features a suppression of $CP$ violation in neutrino oscillations, a low scale for the heavy Majorana neutrino (few TeV) and, due to the unbroken $Z_2$ symmetry, a natural dark matter candidate.

We discuss novel effects in the phenomenology of a light Higgs boson within the context of composite models. We show that large modifications may arise in the decay of a composite Nambu-Goldstone boson Higgs to a photon and a $Z$ boson, $h\to Z\gamma$. These can be generated by the exchange of massive composite states of a strong sector that breaks a left-right symmetry, which we show to be the sole symmetry structure responsible for governing the size of these new effects in the absence of Goldstone-breaking interactions. In this paper we consider corrections to the decay $h\to Z\gamma$ obtained either by integrating out vectors at tree level, or by integrating out vectorlike fermions at loop level. In each case, the pertinent operators that are generated are parametrically enhanced relative to other interactions that arise at loop level in the Standard Model such as $h\to gg$ and $h\to \gamma \gamma$. Thus we emphasize that the effects of interest here provide a unique possibility to probe the dynamics underlying electroweak symmetry breaking, and do not depend on any contrivance stemming from carefully chosen spectra. The effects we discuss naturally lead to concerns of compatibility with precision electroweak measurements, and we show with relevant computations that these corrections can be kept well under control in our general parameter space.

We examine the status of dark matter (heavy photon) in the littlest Higgs model with $T$ parity (LHT) in light of the new results from the LHC Higgs search, the Planck dark matter relic density, and the XENON100 limit on the dark matter scattering off the nucleon. We obtain the following observations: (i) For the LHC Higgs data, the LHT can well be consistent with the CMS results but disfavored by the ATLAS observation of diphoton enhancement; (ii) for the dark matter relic density, the heavy photon in the LHT can account for the Planck data for the small mass splitting of mirror lepton and heavy photon; (iii) for the dark matter scattering off the nucleon, the heavy photon can give a spin-independent cross section below the XENON100 upper limit for $m_{A_H}>95\mathrm{GeV}$ ($f>665\mathrm{GeV}$); (iv) a fit using the CMS Higgs data gives the lowest chi square of 2.63 (the standard model value is 4.75) at $f\simeq 1120\mathrm{GeV}$ and $m_{A_H}\simeq 170\mathrm{GeV}$ (at this point, the dark matter constraints from Planck and XENON100 can also be satisfied). Such a best point and its nearby favored region (even for an $f$ value up to 3.8 TeV) can be covered by the future XENON1T (2017) experiment.

We study the inclusive production of $J/\psi$ and $\psi (2S)$ mesons originating from the decays of bottom-flavored hadrons produced in $p\overline{p}$ collisions at the Fermilab Tevatron and in $pp$ collisions at the CERN LHC. We work at next-to-leading order in the general-mass variable-flavor-number scheme implemented with nonperturbative fragmentation functions fitted to $e^{+}{e}^{-}$ data of inclusive $b$-hadron production exploiting their universality. The three-momentum distributions of the charmonia used were extracted from $B$-decay data in the framework of nonrelativistic-QCD factorization. Comparing the theoretical predictions thus obtained with transverse-momentum distributions measured by the CDF II, ALICE, ATLAS, CMS, and LHCb collaborations, we find excellent overall agreement as for both absolute normalization and line shape, which provides a nontrivial test of the general-mass variable-flavor-number scheme over wide ranges of center-of-mass energy, transverse momentum, and rapidity.

We study the features of nonlocal SU(3) chiral quark models with wave function renormalization. Model parameters are determined from meson phenomenology, considering different nonlocal form factor shapes. In this context we analyze the characteristics of the deconfinement and chiral restoration transitions at finite temperature, introducing the couplings of fermions to the Polyakov loop. We analyze the results obtained for various thermodynamical quantities considering different Polyakov loop potentials and nonlocal form factors, in comparison with data obtained from lattice QCD calculations.