The Bethe-Salpeter equation is used to comprehensively study mesons with $J=0$, 1 and equal-mass constituents for quark masses from the chiral limit to the $b$-quark mass. The survey contains masses of the ground states in all corresponding $J^{PC}$ channels including those with “exotic” quantum numbers. The emphasis is put on each particular state’s sensitivity to the low- and intermediate-momentum, i.e., long-range part of the strong interaction.

Color magnetic flux tubes appear in the color-flavor locked phase of high density QCD, which exhibits color superconductivity as well as superfluidity. They are non-Abelian superfluid vortices and are accompanied by orientational zero modes in the internal space associated with the color-flavor locked symmetry spontaneously broken in the presence of the vortex. We show that those zero modes are localized around the vortex in spite of the logarithmic divergence of its tension and derive the low-energy effective theory of them on the world sheet of the vortex string.

In this paper, we reassess a particular $R^2$-type gravity action in D dimensions, recently studied by Nakasone and Oda, now taking torsion effects into account. Considering that the vielbein and the spin connection carry independent propagating degrees of freedom, we conclude that ghosts and tachyons are absent only if torsion is nonpropagating, and we also conclude that there is no room for massive gravitons. To include these excitations, we understand how to enlarge Nakasone-Oda’s model by means of explicit torsion terms in the action and we discuss the unitarity of the enlarged model for arbitrary dimensions.

Cosmic superstring loops generically contain strings of different tensions that meet at Y-junctions. These loops evolve nonperiodically in time, and have cusps and kinks that interact with the junctions. We study the effect of junctions on the gravitational wave signal emanating from cosmic string cusps and kinks. We find that earlier results on the strength of individual bursts from cusps and kinks on strings without junctions remain largely unchanged, but junctions give rise to additional contributions to the gravitational wave signal coming from strings expanding at the speed of light at a junction and kinks passing through a junction.

The combination of current large-scale structure and cosmic microwave background anisotropies data can place strong constraints on the sum of the neutrino masses. Here we show that future cosmic shear experiments, in combination with cosmic microwave background constraints, can provide the statistical accuracy required to answer questions about differences in the mass of individual neutrino species. Allowing for the possibility that masses are nondegenerate we combine Fisher matrix forecasts for a weak lensing survey like Euclid with those for the forthcoming Planck experiment. Under the assumption that neutrino mass splitting is described by a normal hierarchy we find that the combination Planck and Euclid will possibly reach enough sensitivity to put a constraint on the mass of a single species. Using a Bayesian evidence calculation we find that such future experiments could provide strong evidence for either a normal or an inverted neutrino hierarchy. Finally we show that if a particular neutrino hierarchy is assumed then this could bias cosmological parameter constraints, for example, the dark energy equation of state parameter, by $\gtrsim 1\sigma$, and the sum of masses by $2.3\sigma$. We finally discuss the impact of uncertainties on the theoretical modeling of nonlinearities. The results presented in this analysis are obtained under an approximation to the nonlinear power spectrum. This significant source of uncertainty needs to be addressed in future work.

We recompute the invisible Higgs decay width arising from Higgs-graviscalar mixing in the Arkani-Hamed, Dimopoulos, Dvali model, comparing the original derivation in the nondiagonal mass basis to that in a diagonal mass basis. The results obtained are identical (and differ by a factor of 2 from the original calculation) but the diagonal-basis derivation is pedagogically useful for clarifying the physics of the invisible width from mixing. We emphasize that both derivations make it clear that a direct scan in energy for a process such as $WW\to WW$ mediated by Higgs plus graviscalar intermediate resonances would follow a single Breit-Wigner form with total width given by ${\Gamma }^{\mathrm{tot}}={\Gamma }_h^{\mathrm{SM}}+{\Gamma }_{\mathrm{invisible}}$. We also compute the additional contributions to the invisible width due to direct Higgs to graviscalar-pair decays. We find that the invisible width due to the latter is relatively small, unless the Higgs mass is comparable to or larger than the effective extra-dimensional Planck mass.

It has been suggested that dark matter particles which scatter inelastically from detector target nuclei could explain the apparent incompatibility of the DAMA modulation signal (interpreted as evidence for particle dark matter) with the null results from CDMS-II and XENON10. Among the predictions of inelastically interacting dark matter are a suppression of low-energy events, and a population of nuclear recoil events at higher nuclear recoil equivalent energies. This is in stark contrast to the well-known expectation of a falling exponential spectrum for the case of elastic interactions. We present a new analysis of XENON10 dark matter search data extending to $E_{nr}=75\mathrm{keV}$ nuclear recoil equivalent energy. Our results exclude a significant region of previously allowed parameter space in the model of inelastically interacting dark matter. In particular, it is found that dark matter particle masses $m_{\chi }\gtrsim 150\mathrm{GeV}$ are disfavored.

The dipole and the Dokshitzer-Gribov-Lipatov-Altarelli-Parisi (DGLAP) approximations are combined with the $k_t$ factorization theorem to demonstrate the fundamental property of perturbative QCD: the smaller the size of the colorless quark-gluon configurations in the fragmentation region, the more rapid is the increase of its interaction with the target as a function of energy. First, we consider two closely related properties of the wave function of the projectile: (i) the transverse momenta of the quark(antiquark) within the $q\overline{q}$ pair, produced in the fragmentation region by the strongly virtual photon, increase with the decrease of $x$ for fixed $Q^2$, (ii) the relative contribution of perturbative QCD to the structure functions increases as compared to the soft QCD contribution at central impact parameters due to a rapid increase with energy of the cross section of interaction of small dipoles. Practical consequences of these effects are presented for the cases of the cross sections of deep inelastic scattering (DIS) and double virtual compton scattering (DVCS). We predict that the ratio of DVCS to DIS amplitudes should very slowly approach one from above at very large collision energies. Second, we study a closely related phenomenon of the increase of the transverse momenta with the energy of the characteristic transverse momenta of the gluon/quark configurations responsible for the transition to the black disk regime. We discuss the impact of this phenomenona on the slowing of the dependence on the initial energy of the coherence length. We demonstrate that a rapid projectile has the biconcave shape, which is different from the expectations of the pre-QCD parton model where a fast hadron has a pancake shape. We show that the increase of the transverse momenta leads to a new expression for the total cross section of a DIS at very large energies, relevant to LHeC and LHC. We discuss the impact of the discovered phenomena on the hard processes in $pp$ collisions, and on the dominance of different phases of chiral and conformal symmetries in the central and peripheral $pp$, $pA$, and $AA$ collisions.

Using the exact propagators in a constant magnetic field, the neutrino self-energy has been calculated to all orders in the field strength $B$ within the minimal extension of the Weinberg-Salam model with massive Dirac neutrinos. A simple and very accurate formula for the self-energy is obtained, that is valid for $0\le B\ll m_W^2/e$ and for neutrino transverse momentum to the magnetic field $p_{\perp }\ll m_W$. I discuss the implications of this finding to the dispersion of massless neutrinos in vacuum and in a charge-symmetric medium, and to the magnetic field induced resonance transitions of massive neutrinos inside supernovae and magnetars, and calculate the neutrino magnetic moment.

We present updated measurements of the branching fractions for $B^0$ meson decays to $\eta K^0$, $\eta \eta$, $\eta \varphi$, $\eta \omega$, ${\eta }^{\prime }{K}^0$, ${\eta }^{\prime }{\eta }^{\prime }$, ${\eta }^{\prime }\varphi$, and ${\eta }^{\prime }\omega$, and branching fractions and $CP$-violating charge asymmetries for $B^{+}$ decays to $\eta {\pi }^{+}$, $\eta K^{+}$, ${\eta }^{\prime }{\pi }^{+}$, and ${\eta }^{\prime }{K}^{+}$. The data represent the full data set of $467\times {10}^6$ $B\overline{B}$ pairs collected with the BABAR detector at the PEP-II asymmetric-energy $e^{+}{e}^{-}$ collider at the SLAC National Accelerator Laboratory. Besides large signals for the four charged $B$ decay modes and for $B^0\to {\eta }^{\prime }{K}^0$, we find evidence for three $B^0$ decay modes at greater than $3.0\sigma$ significance. We find $\mathcal{B}(B^0\to \eta K^0)=({1.15}_{-0.38}^{+0.43}\pm 0.09)\times {10}^{-6}$, $\mathcal{B}(B^0\to \eta \omega )=({0.94}_{-0.30}^{+0.35}\pm 0.09)\times {10}^{-6}$, and $\mathcal{B}(B^0\to {\eta }^{\prime }\omega )=({1.01}_{-0.38}^{+0.46}\pm 0.09)\times {10}^{-6}$, where the first (second) uncertainty is statistical (systematic). For the $B^{+}\to \eta K^{+}$ decay mode, we measure the charge asymmetry ${\mathcal{A}}_{\mathrm{ch}}(B^{+}\to \eta K^{+})=-0.36\pm 0.11\pm 0.03$.

We study the low-energy theorems of QCD from the point of view of the dual AdS/QCD models and demonstrate that these models are compatible with the theorems in the chiral limit, i.e. the arising expressions have the same analytical behavior at the pole when the quark mass tends to zero. Low-energy theorems are formulated in terms of the spectral density of the Dirac operator. In order to calculate the spectral density in the dual holographic models we express it in terms of a partition function of a QCD-like theory.

A time-varying fine structure constant $\alpha (t)$ could give rise to Lorentz- and $CPT$-violating changes to the vacuum polarization, which would affect photon propagation. Such changes to the effective action can violate gauge invariance, but they are otherwise permitted. However, in the minimal theory of varying $\alpha$, no such terms are generated at lowest order. At second order, vacuum polarization can generate an instability—a Lorentz-violating analogue of a negative photon mass squared $-m_{\gamma }^2\propto \alpha (\frac{\dot{\alpha }}{2\alpha }{)}^2\log ({\Lambda }^2)$, where $\Lambda$ is the cutoff for the low-energy effective theory.

In the context of $f(R)$ theories of gravity, we address the problem of finding static and spherically symmetric black hole solutions. Several aspects of constant curvature solutions with and without electric charge are discussed. We also study the general case (without imposing constant curvature). Following a perturbative approach around the Einstein-Hilbert action, it is found that only solutions of the Schwarzschild-(anti) de Sitter type are present up to second order in perturbations. Explicit expressions for the effective cosmological constant are obtained in terms of the $f(R)$ function. Finally, we have considered the thermodynamics of black holes in anti-de Sitter space-time and found that this kind of solution can only exist provided the theory satisfies $R_0+f(R_0)<0$. Interestingly, this expression is related to the condition which guarantees the positivity of the effective Newton’s constant in this type of theories. In addition, it also ensures that the thermodynamical properties in $f(R)$ gravities are qualitatively similar to those of standard general relativity.

Several improvements in numerical methods and gauge choice are presented that make it possible now to perform simulations of the merger and ringdown phases of “generic” binary black hole evolutions using the pseudospectral evolution code SpEC. These improvements include the use of a new damped-wave gauge condition, a new grid structure with appropriate filtering that improves stability, and better adaptivity in conforming the grid structures to the shapes and sizes of the black holes. Simulations illustrating the success of these new methods are presented for a variety of binary black hole systems. These include fairly generic systems with unequal masses (up to $2:1$ mass ratios), and spins (with magnitudes up to $0.4M^2$) pointing in various directions.

We consider the Freund-Rubin-Englert mechanism of compactification of $N=1$ supergravity in 11 dimensions. We systematically investigate both well-known and some new solutions of the classical equations of motion in 11 dimensions. In particular, we show that any threeform potential in 11 dimension is given locally by the structure constants of a geodesic loop in an affinely connected space.

Speculation that the fine-structure constant $\alpha$ varies in spacetime has a long history. We derive, in 4-D general relativity and in isotropic coordinates, the solution for a charged spherical black hole according to the framework for dynamical $\alpha$ J. D. Bekenstein, Phys. Rev. D 25, 1527 (1982).. This solution coincides with a previously known one-parameter extension of the dilatonic black hole family. Among the notable properties of varying-$\alpha$ charged black holes are adherence to a “no hair” principle, the absence of the inner (Cauchy) horizon of the Reissner-Nordström black holes, the nonexistence of precisely extremal black holes, and the appearance of naked singularities in an analytic extension of the relevant metric. The exteriors of almost extremal electrically (magnetically) charged black holes have simple structures which makes their influence on applied magnetic (electric) fields transparent. We rederive the thermodynamic functions of the modified black holes; the otherwise difficult calculation of the electric potential is done by a shortcut. We confirm that variability of $\alpha$ in the wake of expansion of the universe does not threaten the generalized second law.

We show that, by adding a gauge singlet scalar $S$ to the standard model which is nonminimally coupled to gravity, $S$ can act both as the inflaton and as thermal relic dark matter. We obtain the allowed region of the $(m_s,m_h)$ parameter space which gives a spectral index in agreement with observational bounds and also produces the observed dark matter density while not violating vacuum stability or nonperturbativity constraints. We show that, in contrast to the case of Higgs inflation, once quantum corrections are included the spectral index is significantly larger than the classical value ($n=0.966$ for $N=60$) for all allowed values of the Higgs mass $m_h$. The range of Higgs mass compatible with the constraints is $145\mathrm{GeV}\lesssim m_h\lesssim 170\mathrm{GeV}$. The $S$ mass lies in the range $45\mathrm{GeV}\lesssim m_s\lesssim 1\mathrm{TeV}$ for the case of a real $S$ scalar with large quartic self-coupling ${\lambda }_s$, with a smaller upper bound for smaller ${\lambda }_s$. A region of the parameter space is accessible to direct searches at the LHC via $h\to SS$, while future direct dark matter searches should be able to significantly constrain the model.

There are the two common candidates as the viable energy source for the central engine of long gamma-ray bursts (GRBs) and hypernovae (HNe), neutrino annihilation and magnetic fields. We investigate gravitational wave (GW) emission accompanied by these two mechanisms. Especially, we focus on GW signals produced by neutrinos from a hyper-accreting disk around a massive black hole. We show that neutrino-induced GWs are detectable for $\sim 1\mathrm{Mpc}$ events by LISA and $\sim 100\mathrm{Mpc}$ by DECIGO/BBO, if the central engine is powered by neutrinos. The GW signals depend on the viewing angle and they are anticorrelated with neutrino ones. But, simultaneous neutrino detections are also expected, and helpful for diagnosing the explosion mechanism when later electromagnetic observations enable us to identify the source. GW and neutrino observations are potentially useful for probing choked jets that do not produce prompt emission, as well as successful jets. Even in nondetection cases, observations of GWs and neutrinos could lead to profitable implications for the central engine of GRBs and HNe.

We revisit the predictions for the expected cosmic microwave background bispectrum signal from the cross-correlation of the primary-lensing-Rees-Sciama signal; we point out that it can be a significant contaminant to the bispectrum signal from primordial non-Gaussianity of the local type. This non-Gaussianity, usually parametrized by the non-Gaussian parameter $f_{NL}$, arises, for example, in multifield inflation. In particular both signals are frequency-independent, and are maximized for nearly squeezed configurations. While their detailed scale-dependence and harmonic imprints are different for generic bispectrum shapes, we show that, if not included in the modeling, the primary-lensing-Rees-Sciama contribution yields an effective $f_{NL}$ of 10 when using a bispectrum estimator optimized for local non-Gaussianity. Considering that expected $1\mathrm{\text{−}}\sigma$ errors on $f_{NL}$ are $<10$ from forthcoming experiments, we conclude that the contribution from this signal must be included in future constraints on $f_{NL}$ from the cosmic microwave background bispectrum.

We study the strong gravity regime in viable models of so-called $f(R)$ gravity that account for the observed cosmic acceleration. In contrast with recent works suggesting that very relativistic stars might not exist in these models, we find numerical solutions corresponding to static star configurations with a strong gravitational field. The choice of the equation of state for the star is crucial for the existence of solutions. Indeed, if the pressure exceeds 3 times the energy density in a large part of the star, static configurations do not exist. In our analysis, we use a polytropic equation of state, which is not plagued with this problem and, moreover, provides a better approximation for a realistic neutron star.