A precise measurement of the cross section for the process $e^{+}{e}^{-}\to K^{+}{K}^{-}(\gamma )$ from threshold to an energy of 5 GeV is obtained with the initial-state radiation (ISR) method using $232{\mathrm{fb}}^{-1}$ of data collected with the BABAR detector at $e^{+}{e}^{-}$ center-of-mass energies near 10.6 GeV. The measurement uses the effective ISR luminosity determined from the $e^{+}{e}^{-}\to {\mu }^{+}{\mu }^{-}(\gamma ){\gamma }_{\mathrm{ISR}}$ process with the same data set. The corresponding lowest-order contribution to the hadronic vacuum polarization term in the muon magnetic anomaly is found to be $a_{\mu }^{KK,\mathrm{LO}}=(22.93\pm {0.18}_{\mathrm{stat}}\pm {0.22}_{\mathrm{syst}})\times {10}^{-10}$. The charged kaon form factor is extracted and compared to previous results. Its magnitude at large energy significantly exceeds the asymptotic QCD prediction, while the measured slope is consistent with the prediction.

We present the results of a search for the rare flavor-changing neutral-current decays $B\to \pi {\ell }^{+}{\ell }^{-}$ ($\pi ={\pi }^{\pm }$, ${\pi }^0$ and $\ell =e$, $\mu$) and $B^0\to \eta {\ell }^{+}{\ell }^{-}$ using a sample of $e^{+}{e}^{-}\to {\rm Y}(4S)\to B\overline{B}$ decays corresponding to $428{\mathrm{fb}}^{-1}$ of integrated luminosity collected by the BABAR detector. No significant signal is observed, and we set an upper limit on the isospin and lepton-flavor averaged branching fraction of $\mathcal{B}(\mathcal{B}\to \pi {\ell }^{+}{\ell }^{-})<5.9\times {10}^{-8}$ and a lepton-flavor averaged upper limit of $\mathcal{B}({\mathcal{B}}^0\to \eta {\ell }^{+}{\ell }^{-})<6.4\times {10}^{-8}$, both at the 90% confidence level. We also report 90% confidence level branching fraction upper limits for the individual modes $B^{+}\to {\pi }^{+}{e}^{+}{e}^{-}$, $B^0\to {\pi }^0{e}^{+}{e}^{-}$, $B^{+}\to {\pi }^{+}{\mu }^{+}{\mu }^{-}$, $B^0\to {\pi }^0{\mu }^{+}{\mu }^{-}$, $B^0\to \eta e^{+}{e}^{-}$, and $B^0\to \eta {\mu }^{+}{\mu }^{-}$.

We report results of a search for weakly interacting massive particles (WIMPs) with the Si detectors of the CDMS II experiment. This report describes a blind analysis of the first data taken with CDMS II’s full complement of detectors in 2006–2007; results from this exposure using the Ge detectors have already been presented. We observed no candidate WIMP-scattering events in an exposure of 55.9 kg-days before analysis cuts, with an expected background of $\sim 1.1$ events. The exposure of this analysis is equivalent to 10.3 kg-days over a recoil energy range of 7–100 keV for an ideal Si detector and a WIMP mass of $10\mathrm{GeV}/{\mathrm{c}}^2$. These data set an upper limit of $1.7\times {10}^{-41}{\mathrm{cm}}^2$ on the WIMP-nucleon spin-independent cross section of a $10\mathrm{GeV}/{\mathrm{c}}^2$ WIMP. These data exclude parameter space for spin-independent WIMP-nucleon elastic scattering that is relevant to recent searches for low-mass WIMPs.

QCD sum rules are employed to determine whether the $X(3872)$ can be described as a mixed state that couples to $J^{PC}=1^{++}$ charmonium hybrid and $\overline{D}{D}^{*}$ molecular currents. After calculating the mixed correlator of hybrid and molecular currents, we formulate the sum rule in terms of a mixing parameter that interpolates between the pure molecular and hybrid scenarios. As the mixing parameter is increased from the pure molecular case, the predicted mass increases until it reaches a maximum value in good agreement with the $X(3872)$ and the resulting sum-rule analysis appears more robust than the pure molecular case.

We observe that the Faddeev-Skyrme model emerges as a low-energy limit of scalar QED with two charged scalar fields and a self-interaction potential of a special form (inspired by supersymmetric QED). Then we discuss possible Hopf solitons of the “twisted-toroidal” type.

In this paper we study the Casimir energy of QCD within the Gribov-Zwanziger approach. In this model nonperturbative effects of gauge copies are properly taken into account. We show that the computation of the Casimir energy for the MIT bag model within the (refined) Gribov-Zwanziger approach not only can give the correct sign but it also gives an estimate for the radius of the bag.

The effective potential of the order parameter for confinement is calculated for $\mathrm{SU}(N)$ Yang-Mills theory in the Hamiltonian approach. Compactifying one spatial dimension and using a background gauge fixing, this potential is obtained within a variational approach by minimizing the energy density for given background field. In this formulation the inverse length of the compactified dimension represents the temperature. Using Gaussian trial wave functionals we establish an analytic relation between the propagators in the background gauge at finite temperature and the corresponding zero-temperature propagators in Coulomb gauge. In the simplest truncation, neglecting the ghost and using the ultraviolet form of the gluon energy, we recover the Weiss potential. Neglecting the ghost and using for the gluon energy $\omega (p)$ the approximate Gribov formula $\omega (p)\simeq p+M^2/p$ one finds a critical temperature of $\sqrt{3}M/\pi$. We explicitly show that the omission of the ghost drastically increases the transition temperature. From the full nonperturbative potential (with the ghost included) we extract a critical temperature of the deconfinement phase transition of 269 MeV for the gauge group SU(2) and 283 MeV for SU(3).

Within the superfield method, we extend the formulation of the Lorentz-breaking aether superspace for supergauge theories, in both three- and four-dimensional cases.

Over the past few years much attention has been given to the study of modified gravity theories in order to find a more natural explanation for the late time acceleration of the Universe. Nevertheless, a comparison of the matter power spectrum predictions made by these theories with available data has not yet been subjected to a detailed analysis. In the context of $f(R)$ theories of gravity we study the predicted power spectra using both a dynamical systems approach for the background and solving for the matter perturbations without using the quasistatic approximation, comparing the theoretical results with several Sloan Digital Sky Survey data. The importance of studying the first order perturbed equations by assuming the correct background evolution and the relevance of the initial conditions are also stressed. We determine the statistical significance in relation to the observational data and demonstrate their conflict with existing observations.

Diffeomorphisms preserve spacetime singularities, whereas higher spin symmetries need not. Since three-dimensional de Sitter space has quotients that have big-bang/big-crunch singularities and since ${\mathrm{dS}}_3$-gravity can be written as an $SL(2,\mathbb{C})$ Chern-Simons theory, we investigate $SL(3,\mathbb{C})$ Chern-Simons theory as a higher-spin context in which these singularities might get resolved. As in the case of higher spin black holes in ${\mathrm{AdS}}_3$, the solutions are invariantly characterized by their holonomies. We show that the ${\mathrm{dS}}_3$ quotient singularity can be desingularized by an $SL(3,\mathbb{C})$ gauge transformation that preserves the holonomy: this is a higher spin resolution the cosmological singularity. Our work deals exclusively with the bulk theory, and is independent of the subtleties involved in defining a ${\mathrm{CFT}}_2$ dual to ${\mathrm{dS}}_3$ in the sense of dS/CFT.

We investigate the cosmological solutions of $f(R,T)$ modified theories of gravity for a perfect fluid in a spatially Friedmann-Lemaître-Robertson-Walker metric through the phase-space analysis, where $R$ is the Ricci scalar and $T$ denotes the trace of the energy-momentum tensor of the matter content. We explore and analyze the three general theories with the Lagrangians of minimal $g(R)+h(T)$, pure nonminimal $g(R)h(T)$, and nonminimal $g(R)(1+h(T))$ couplings through the dynamical systems approach. We introduce a few variables and dimensionless parameters to simplify the equations to more concise forms. The conservation of the energy-momentum tensor leads to a constraint equation that, in the minimal gravity, confines the functionality of $h(T)$ to a particular form, and hence relates the dynamical variables. In this case, acceptable cosmological solutions that contain a long enough matter-dominated era followed by a late-time accelerated expansion are found. To support the theoretical results, we also obtain numerical solutions for a few functions of $g(R)$, and the results of the corresponding models confirm the predictions. We separate the solutions into six classes which demonstrate more acceptable solutions and there is more freedom to have the matter-dominated era than in $f(R)$ gravity. In particular, there is a new fixed point which can represent the late-time acceleration. We draw different diagrams of the matter densities (consistent with the present values), the related scale factors, and the effective equation of state. The corresponding diagrams of the parameters illustrate that there is a saddle acceleration era which is a middle era before the final stable-acceleration de Sitter era for some models. All presented diagrams determine radiation, matter, and late-time acceleration eras very well. The pure nonminimal theory suffers from the absence of a standard matter era, though we illustrate that the nonminimal theory can have acceptable cosmological solutions.

We provide an in-depth investigation of quasinormal-mode oscillations of Kerr black holes with nearly extremal angular momenta. We first discuss in greater detail the two distinct types of quasinormal-mode frequencies presented in a recent paper [H. Yang et al., Phys. Rev. D 87, 041502 (2013)]. One set of modes that we call “zero-damping modes” has vanishing imaginary part in the extremal limit and exists for all corotating perturbations (i.e. modes with azimuthal index $m\ge 0$). The other set (the “damped modes”) retains a finite decay rate even for extremal Kerr black holes and exists only for a subset of corotating modes. As the angular momentum approaches its extremal value, the frequency spectrum bifurcates into these two distinct branches when both types of modes are present. We discuss the physical reason for the mode branching by developing and using a bound-state formulation for the perturbations of generic Kerr black holes. We also numerically explore the specific case of the fundamental $l=2$ modes, which have the greatest astrophysical interest. Using the results of these investigations, we compute the quasinormal-mode response of a nearly extremal Kerr black hole to perturbations. We show that many superimposed overtones result in a slow power-law decay of the quasinormal ringing at early times, which later gives way to exponential decay. This exceptional early-time power-law decay implies that the ringdown phase is long lived for black holes with large angular momentum, which could provide a promising strong source for gravitational-wave detectors.

We study the universal nature of the product of the entropies of all horizons of charged rotating black holes. We argue, by examining further explicit examples, that when the maximum number of rotations and/or charges are turned on, the entropy product is expressed in terms of angular momentum and/or charges only, which are quantized. (In the case of gauged supergravities, the entropy product depends on the gauge-coupling constant also.) In two-derivative gravities, the notion of the “maximum number” of charges can be defined as being sufficiently many nonzero charges that the Reissner-Nordström black hole arises under an appropriate specialization of the charges. (The definition can be relaxed somewhat in charged anti-de Sitter black holes in $D\ge 6$.) In higher-derivative gravity, we use the charged rotating black hole in Weyl-Maxwell gravity as an example for which the entropy product is still quantized, but it is expressed in terms of the angular momentum only, with no dependence on the charge. This suggests that the notion of maximum charges in higher-derivative gravities requires further understanding.

We give a simple discussion of ghosts, unitarity violation, negative norm states, and quantum vs classical behavior in the simplest model with a four-derivative action—the Pais-Uhlenbeck oscillator. We also point out that the normalizable “vacuum state” (in the sense defined below) of this model can be understood as a spontaneous breaking of the emergent conformal symmetry. We provide an example of an interacting system that couples the “particle” and “ghost” degrees of freedom and nevertheless remains unitary on both the classical and quantum levels.

We obtain a new solution of rotating black string coupled to a nonlinear electromagnetic field in the background of anti-de Sitter spaces. We consider two types of nonlinear electromagnetic Lagrangians, namely, logarithmic and exponential forms. We investigate the geometric effects of nonlinearity parameter and find that for large $r$, these solutions recover the rotating black string solutions of Einstein-Maxwell theory. We calculate the conserved and thermodynamic quantities of the rotating black string. We also analyze thermodynamics of the spacetime and verify the validity of the first law of thermodynamics for the obtained solutions.

We derive distance priors from Planck first data release, and examine their impact on dark energy constraints from current observational data. We give the mean values and covariance matrix of $\{R,l_a,{\Omega }_b{h}^2,n_s\}$, which give an efficient summary of Planck data. The cosmic microwave background shift parameters are $R=\sqrt{{\Omega }_m{H}_o^2}r(z_{*})$, and $l_a=\pi r(z_{*})/r_s(z_{*})$, where $z_{*}$ is the redshift at the last scattering surface, and $r(z_{*})$ and $r_s(z_{*})$ denote our comoving distance to $z_{*}$ and sound horizon at $z_{*}$ respectively. We find that Planck distance priors are significantly tighter than those from WMAP9. However, adding Planck distance priors does not lead to significantly improved dark energy constraints using current data, compared to adding WMAP9 distance priors. This is because Planck data appear to favor a higher matter density and lower Hubble constant, in tension with most of the other current cosmological data sets. Adding Planck distance priors to current data leads to a marginal inconsistency with a cosmological constant in a flat universe.

There is growing interest in testing alternative gravity theories using the subtle gravitational redshifts in clusters of galaxies. However, current models all neglect a transverse Doppler redshift of similar magnitude, and some models are not self-consistent. An equilibrium model would fix the gravitational and transverse Doppler velocity shifts to be about $6{\sigma }^2/c$ and $3{\sigma }^2/2c$ in order to fit the observed velocity dispersion $\sigma$ self-consistently. This result comes from the virial theorem for a spherical isotropic cluster, and is insensitive to the theory of gravity. A gravitational redshift signal also does not directly distinguish between the Einsteinian and $f(R)$ gravity theories, because each theory requires a different dark halo mass function to keep the clusters in equilibrium. When this constraint is imposed, the gravitational redshift has no sensitivity to theory. Indeed, our $N$-body simulations show that the halo mass function differs in $f(R)$, and that the transverse Doppler effect is stronger than analytically predicted due to nonequilibrium.

A number of theoretically well-motivated additions to the standard cosmological model predict weak signatures in the form of spatially localized sources embedded in the cosmic microwave background (CMB) fluctuations. We present a hierarchical Bayesian statistical formalism and a complete data analysis pipeline for testing such scenarios. We derive an accurate approximation to the full posterior probability distribution over the parameters defining any theory that predicts sources embedded in the CMB, and perform an extensive set of tests in order to establish its validity. The approximation is implemented using a modular algorithm, designed to avoid a posteriori selection effects, which combines a candidate-detection stage with a full Bayesian model-selection and parameter-estimation analysis. We apply this pipeline to theories that predict cosmic textures and bubble collisions, extending previous analyses by using: (1) adaptive-resolution techniques, allowing us to probe features of arbitrary size, and (2) optimal filters, which provide the best possible sensitivity for detecting candidate signatures. We conclude that the WMAP 7-year data do not favor the addition of either cosmic textures or bubble collisions to $\Lambda \mathrm{CDM}$, and place robust constraints on the predicted number of such sources. The expected numbers of bubble collisions and cosmic textures on the CMB sky within our detection thresholds are constrained to be fewer than 4.0 and 5.2 at 95% confidence, respectively.

We expand on our study of the gravitational and electromagnetic emissions from the late stage of an inspiraling neutron star binary as presented in Palenzuela et al. [Phys. Rev. Lett. 111, 061105 (2013)]. Interactions between the stellar magnetospheres, driven by the extreme dynamics of the merger, can yield considerable outflows. We study the gravitational and electromagnetic waves produced during the inspiral and merger of a binary neutron star system using a full relativistic, resistive magnetohydrodynamics evolution code. We show that the interaction between the stellar magnetospheres extracts kinetic energy from the system and powers radiative Poynting flux and heat dissipation. These features depend strongly on the configuration of the initial stellar magnetic moments. Our results indicate that this power can strongly outshine pulsars in binaries and have a distinctive angular and time-dependent pattern. Our discussion provides more detail than Palenzuela et al., showing clear evidence of the different effects taking place during the inspiral. Our simulations include a few milliseconds after the actual merger and study the dynamics of the magnetic fields during the formation of the hypermassive neutron star. We also briefly discuss the possibility of observing such emissions.

We calculate the scalar-gravitational quasinormal modes of equal angular momenta Myers-Perry black holes in odd dimensions. We find a new bar-mode (non-axisymmetric) classical instability for $D\ge 7$. These black holes were previously found to be unstable to axisymmetric perturbations for spins very near extremality. The bar-mode instability we find sets in at much slower spins, and is therefore the dominant instability of these black holes. This instability has important consequences for the phase diagram of black holes in higher dimensions.