Analyzing ${\rm Y}(nS)$ decays acquired with the CLEO detector operating at the CESR $e^{+}{e}^{-}$ collider, we measure for the first time the product branching fractions $\mathcal{B}[{\rm Y}(nS)\to \gamma {\chi }_{bJ}((n-1)P)]\mathcal{B}[{\chi }_{bJ}(n-1)P)\to X_i]$ for $n=2$ and 3, where $X_i$ denotes, for each $i$, one of the 14 exclusive light-hadron final states for which we observe significant signals in both ${\chi }_{bJ}(1P)$ and ${\chi }_{bJ}(2P)$ decays. We also determine upper limits for the electric dipole (E1) transitions ${\rm Y}(3S)\to \gamma {\chi }_{bJ}(1P)$.

We report a search for the decays $B^{-}\to K^{+}{\pi }^{-}{\pi }^{-}$ and $B^{-}\to K^{-}{K}^{-}{\pi }^{+}$, which are highly suppressed in the standard model. Using a sample of $(467\pm 5)\times {10}^6$ $B\overline{B}$ pairs collected with the BABAR detector, we do not see any evidence of these decays and determine 90% confidence level upper limits of $\mathcal{B}(B^{-}\to K^{+}{\pi }^{-}{\pi }^{-})<9.5\times {10}^{-7}$ and $\mathcal{B}(B^{-}\to K^{-}{K}^{-}{\pi }^{+})<1.6\times {10}^{-7}$ on the corresponding branching fractions, including systematic uncertainties.

We show that the $\mathcal{N}=8$ superconformal Bagger-Lambert theory based on the Lorentzian 3-algebra can be derived by taking a certain scaling limit of the recently proposed $\mathcal{N}=6$ superconformal $U(N)\times U(N)$ Chern-Simons-matter theories at level $(k,-k)$. The scaling limit (and Inönü-Wigner contraction) is to scale the trace part of the bifundamental fields as $X_0\to {\lambda }^{-1}{X}_0$ and an axial combination of the two gauge fields as $B_{\mu }\to \lambda B_{\mu }$. Simultaneously, we scale the level as $k\to {\lambda }^{-1}k$ and then take $\lambda \to 0$ limit. Interestingly, the same constraint equation ${\partial }^2{X}_0=0$ is derived by imposing finiteness of the action. In this scaling limit, M2 branes are located far from the origin of ${\mathbf{C}}^4/{\mathbf{Z}}_{\mathbf{k}}$ compared to their fluctuations and ${\mathbf{Z}}_{\mathbf{k}}$ identification becomes a circle identification. Hence, the scaled theory describes $\mathcal{N}=8$ supersymmetric theory of 2-branes with dynamical coupling. The coupling constant is promoted to a space-time dependent $SO(8)$ vector $X_0^I$ and we show that the scaled theory has a generalized conformal symmetry as well as manifest $SO(8)$ with the transformation of the background fields $X_0^I$.

The imminent start of the Large Hadron Collider, which is expected to produce $\sim {10}^8$ $t\overline{t}$ pairs per year, provides an unprecedented opportunity for top physics. As the top quark is widely expected to be rather sensitive to effects of new physics, a detailed study of its properties, including rare decays, is called for. A possible, experimentally distinctive decay is the case where a top decays to a light quark and a flavor-violating lepton-antilepton pair. We use an effective operator analysis to place model-independent bounds on contributions to the decays $t\to u{e}^{\pm }{\mu }^{\mp }$ and $t\to c{e}^{\pm }{\mu }^{\mp }$. We enumerate the dimension-six operators which contribute to these decays and which are invariant under the standard model gauge group. We separate these operators into two classes, one with operators where the top quark belongs to an $SU(2)$ doublet and thus can contribute at tree level to low-energy processes, and one class with operators where the top quark is a right-handed singlet and can only contribute to low-energy processes via loop diagrams. We use $B$ and $K$ decays to place limits on the coefficients of some of these operators, but find that several remain unconstrained and could potentially make observable contributions to top decay.

Some years ago, a new powerful technique, known as the classical effective field theory, was proposed to describe classical phenomena in gravitational systems. Here we show how this approach can be useful to investigate theoretically important issues, such as gravitational radiation in any spacetime dimension. In particular, we derive for the first time the Einstein-Infeld-Hoffman Lagrangian and we compute Einstein’s quadrupole formula for any number of flat spacetime dimensions.

We find candidate macroscopic gravity duals for scale-invariant but non-Lorentz invariant fixed points, which do not have particle number as a conserved quantity. We compute two-point correlation functions which exhibit novel behavior relative to their AdS counterparts, and find holographic renormalization group flows to conformal field theories. Our theories are characterized by a dynamical critical exponent $z$, which governs the anisotropy between spatial and temporal scaling $t\to {\lambda }^{z}t$, $x\to \lambda x$; we focus on the case with $z=2$. Such theories describe multicritical points in certain magnetic materials and liquid crystals, and have been shown to arise at quantum critical points in toy models of the cuprate superconductors. This work can be considered a small step towards making useful dual descriptions of such critical points.

A semiclassical picture of spontaneous symmetry breaking in light front field theory is formulated. It is based on a finite-volume quantization of self-interacting scalar fields obeying antiperiodic boundary conditions. This choice avoids a necessity to solve the zero-mode constraint and enables one to define unitary operators which shift the scalar field by a constant. The operators simultaneously transform the light front Fock vacuum to coherent states with lower energy than the Fock vacuum and with nonzero expectation value of the scalar field. The new vacuum states are noninvariant under the discrete or continuous symmetry of the Hamiltonian. Spontaneous symmetry breaking is described in this way in the two-dimensional $\lambda {\varphi }^4$ theory and in the three-dimensional $O(2)$-symmetric sigma model. A qualitative treatment of topological kink solutions in the first model and a derivation of the Goldstone theorem in the second one are given. Symmetry breaking in the case of periodic boundary conditions is also briefly discussed.

We consider an unstable bound system of two supersymmetric Dirichlet branes of different dimensionality ($p$, $p^{\prime }$ with $p^{\prime }<p$) embedded in a flat noncompactified IIA or IIB type background. We study the decay, via tachyonic condensation, of such unstable bound states leading to a pair of bound $\mathrm{D}(p-1)$, $\mathrm{D}{p}^{\prime }$-branes. We show that only when the gauge fields carried by the $\mathrm{D}p$-brane are localized perpendicular to the tachyon direction, then tachyon condensation will indeed take place. We perform our analysis by combining both the Hamiltonian and the Lagrangian approaches.

We shall investigate the properties of a congruence of geodesics in the framework of Palatini $f(\mathcal{R})$ theories. We shall evaluate the modified geodesic deviation equation and the Raychaudhuri’s equation and show that $f(\mathcal{R})$ Palatini theories do not necessarily lead to attractive forces. Also, we shall study energy condition for $f(\mathcal{R})$ Palatini gravity via a perturbative analysis of the Raychaudhuri’s equation.

We conduct a Markov Chain Monte Carlo study of the Dvali-Gabadadze-Porrati self-accelerating braneworld scenario given the cosmic microwave background (CMB) anisotropy, supernovae and Hubble constant data by implementing an effective dark energy prescription for modified gravity into a standard Einstein-Boltzmann code. We find no way to alleviate the tension between distance measures and horizon-scale growth in this model. Growth alterations due to perturbations propagating into the bulk appear as excess CMB anisotropy at the lowest multipoles. In a flat cosmology, the maximum likelihood Dvali-Gabadadze-Porrati model is nominally a $5.3\sigma$ poorer fit than $\Lambda \mathrm{CDM}$. Curvature can reduce the tension between distance measures but only at the expense of exacerbating the problem with growth leading to a $4.8\sigma$ result that is dominated by the low multipole CMB temperature spectrum. While changing the initial conditions to reduce large-scale power can flatten the temperature spectrum, this also suppresses the large angle polarization spectrum in violation of recent results from the five-year Wilkinson Microwave Anisotropy Probe. The failure of this model highlights the power of combining growth and distance measures in cosmology as a test of gravity on the largest scales.

Keeping the exact general relativistic treatment of light bending as a reference, we compare the accuracy of commonly used approximate lens equations. We conclude that the best approximate lens equation is the Ohanian lens equation, for which we present a new expression in terms of distances between observer, lens, and source planes. We also examine a realistic gravitational lensing case, showing that the precision of the Ohanian lens equation might be required for a reliable treatment of gravitational lensing and a correct extraction of the full information about gravitational physics.

Thermal fluctuations in the coatings used to make high reflectors are becoming significant noise sources in precision optical measurements and are particularly relevant to advanced gravitational-wave detectors. There are two recognized sources of coating thermal noise; mechanical loss and thermal dissipation. Thermal dissipation causes thermal fluctuations in the coating which produce noise via the thermoelastic and thermorefractive mechanisms. We treat these mechanisms coherently, give a correction for finite coating thickness, and evaluate the implications for Advanced LIGO.

We analyze inelastic $2\to 2$ scattering amplitudes for gauge bosons and Nambu-Goldstone bosons in deconstructed Higgsless models. Using the (KK) equivalence theorem in 4D (5D), we derive a set of general sum rules among the boson masses and multiboson couplings that are valid for arbitrary deconstructed models. Taking the continuum limit, our results naturally include the 5D Higgsless model sum rules for arbitrary 5D geometry and boundary conditions; they also reduce to the elastic sum rules when applied to the special case of elastic scattering. For the case of linear deconstructed Higgsless models, we demonstrate that the sum rules can also be derived from a set of general deconstruction identities and completeness relations. We apply these sum rules to the deconstructed 3-site Higgsless model and its extensions; we show that in 5D ignoring all higher KK modes ($n>1$) is inconsistent once the inelastic channels become important. Finally, we discuss how our results generalize beyond the case of linear Higgsless models.

The mass spectra of doubly heavy baryons are systematically calculated in the framework of QCD sum rules. With a tentative heavy-diquark–light-quark configuration, the interpolating currents representing the doubly heavy baryons are proposed. Contributions of the operators up to dimension six are included in operator product expansion. The numerical results are compatible with other theoretical predictions, which may support the $(QQ)-(q)$ structure of doubly heavy baryons.

We report a study of $B^{\pm }\to D^{*}{K}^{\pm }$ decays with $D^{*}$ decaying to $D{\pi }^0$ or $D\gamma$, using $383\times {10}^6$ $B\overline{B}$ pairs collected at the $\mathit{{\rm Y}}(4S)$ resonance with the BABAR detector at the SLAC PEP-II $B$ Factory. The $D$ meson decays under study include a non-$CP$ mode $(K^{\pm }{\pi }^{\mp })$, $CP$-even modes $(K^{\pm }{K}^{\mp },{\pi }^{\pm }{\pi }^{\mp })$, and $CP$-odd modes $(K_S^0{\pi }^0,K_S^0\varphi ,K_S^0\omega )$. We measure ratios ($R_{CP\pm }^{*}$) of branching fractions of decays to $CP$ eigenmode states and to flavor-specific states as well as $CP$ asymmetries ($A_{CP\pm }^{*}$). These measurements are sensitive to the unitarity triangle angle $\gamma$. We obtain $A_{CP+}^{*}=-0.11\pm 0.09\pm 0.01$, $R_{CP+}^{*}=1.31\pm 0.13\pm 0.04$, and $A_{CP-}^{*}=0.06\pm 0.10\pm 0.02$, $R_{CP-}^{*}=1.10\pm 0.12\pm 0.04$, where the first error is statistical and the second error is systematic. Translating our results into an alternative parametrization, widely used for related measurements, we obtain $x_{+}^{*}=0.11\pm 0.06\pm 0.02$ and $x_{-}^{*}=0.00\pm 0.06\pm 0.02$. No significant $CP$-violating charge asymmetry is found in either the flavor-specific mode $D\to K^{\pm }{\pi }^{\mp }$ or in $B^{\pm }\to D^{*}{\pi }^{\pm }$ decays.

The $osp(2n|2n)$ current algebra for a generic positive integer $n$ at general level $k$ is investigated. Its free-field representation and corresponding energy-momentum tensor are constructed. The associated screening currents of the first kind are also presented.

We are studying the dynamics of a one-dimensional field in a noncommutative Euclidean space. The noncommutative space we consider is the one that emerges in the context of three-dimensional Euclidean quantum gravity: it is a deformation of the classical Euclidean space ${\mathbb{E}}^3$ and the Planck length ${\ell }_P$ plays the role of the deformation parameter. The field is interpreted as a particle which evolves in a quantum background. When the dynamics of the particle are linear, the resulting motion is similar to the standard motion in the classical space ${\mathbb{E}}^3$. However, nonlinear dynamics on the noncommutative space are different from the corresponding nonlinear dynamics on the classical space. These discrepancies are interpreted as “quantum gravity” effects. Finally, we propose a background independent description of the propagation of the particle in the quantum geometry.

A general expression for quasilocal energy flux for spacetime perturbation is derived from covariant Hamiltonian formulation using functional differentiability and symplectic structure invariance, which is independent of the choice of the canonical variables and the possible boundary terms one initially puts into the Lagrangian in the diffeomorphism invariant theories. The energy flux expression depends on a displacement vector field and the 2-surface under consideration. We apply and test the expression in Vaidya spacetime. At null infinity the expression leads to the Bondi type energy flux obtained by Lindquist, Schwartz, and Misner. On dynamical horizons with a particular choice of the displacement vector, it gives the area balance law obtained by Ashtekar and Krishnan.

This paper aims at clarifying the link between loop quantum gravity and spin-foam models in four dimensions. Starting from the canonical framework, we construct an operator $P$ acting on the space of cylindrical functions $\mathrm{Cyl}(\Gamma )$, where $\Gamma$ is the four-simplex graph, such that its matrix elements are, up to some normalization factors, the vertex amplitude of spin-foam models. The spin-foam models we are considering are the topological model, the Barrett-Crane model, and the Engle-Pereira-Rovelli model. If one of these spin-foam models provides a covariant quantization of gravity, then the associated operator $P$ should be the so-called “projector” into physical states and its matrix elements should give the physical scalar product. We discuss the possibility to extend the action of $P$ to any cylindrical functions on the space manifold.