We study the decay $B^0\to D^{*+}{D}^{*-}{K}_S^0$ using $(230\pm 2)\times {10}^{6}B\overline{B}$ pairs collected by the BABAR detector at the PEP-II $B$ factory. We measure a branching fraction $\mathcal{B}(B^0\to D^{*+}{D}^{*-}{K}_S^0)=(4.4\pm 0.4\pm 0.7)\times {10}^{-3}$ and find evidence for the decay $B^0\to D^{*-}{D}_{s1}^{+}(2536)$ with a significance of $4.6\sigma$. A time-dependent $CP$ asymmetry analysis is also performed to study the possible resonant contributions to $B^0\to D^{*+}{D}^{*-}{K}_S^0$ and the sign of $\cos 2\beta$. Our measurement indicates that there is a sizable resonant contribution to the decay $B^0\to D^{*+}{D}^{*-}{K}_S^0$ from an unknown $D_{s1}^{+}$ state with large width, and that $\cos 2\beta$ is positive at the 94% confidence level under certain theoretical assumptions.

We use the AdS/CFT correspondence to perform a numerical study of a phase transition in strongly-coupled large-$N_c$ $\mathcal{N}=4$ Super-Yang-Mills theory on a 3-sphere coupled to a finite number $N_f$ of massive $\mathcal{N}=2$ hypermultiplets in the fundamental representation of the gauge group. The gravity dual system is a number $N_f$ of probe D7-branes embedded in ${\mathrm{AdS}}_5\times S^5$. We draw the phase diagram for this theory in the plane of hypermultiplet mass versus temperature and identify for temperatures above the Hawking-Page deconfinement temperature a first-order phase transition line across which the chiral condensate jumps discontinuously.

The Adler-Bell-Jackiw (ABJ) anomaly of a $3+1$ dimensional QED is calculated in the presence of a strong magnetic field. It is shown that in the regime with the lowest Landau level (LLL) dominance a dimensional reduction from $D=4$ to $D=2$ dimensions occurs in the longitudinal sector of the low energy effective field theory. In the chiral limit, the resulting anomaly is therefore comparable with the axial anomaly of a two-dimensional massless Schwinger model. It is further shown that the $U_A(1)$ anomaly of QED in a strong magnetic field is closely related to the nonplanar axial anomaly of a conventional noncommutative $U(1)$ gauge theory.

We consider the quantum correlations, i.e. the entanglement, between two systems uniformly accelerated with identical acceleration $a$ in opposite Rindler quadrants which have reached thermal equilibrium with the Unruh heat bath. To this end we study an exactly soluble model consisting of two oscillators coupled to a massless scalar field in $1+1$ dimensions. We find that for some values of the parameters the oscillators get entangled shortly after the moment of closest approach. Because of boost invariance there are an infinite set of pairs of positions where the oscillators are entangled. The maximal entanglement between the oscillators is found to be approximately 1.4 entanglement bits.

Maximal depth, partially massless, higher spin excitations can mediate charged matter interactions in a de Sitter universe. This result is motivated by similarities between these theories and their traditional Maxwell counterpart: their propagation is lightlike and corresponds to the same Laplacian eigenmodes as the de Sitter photon; they are conformal in four dimensions; their gauge invariance has a single scalar parameter and actions can be expressed as squares of single derivative curvature tensors. We study this effect in detail for its simplest spin 2 example: It is possible to construct a natural and consistent interaction scheme with conserved vector electromagnetic currents primarily coupled to the helicity 1 partially massless modes. The resulting current-current single “partial-photon” exchange amplitude is the (very unCoulombic) sum of contact and shorter-range terms, so the partial photon cannot replace the traditional one, but rather modifies short range electromagnetic interactions. We also write the gauge invariant fourth-derivative effective actions that might appear as effective corrections to the model, and give their contributions to the tree amplitude.

A finite action principle for Einstein-Gauss-Bonnet anti–de Sitter gravity is achieved by supplementing the bulk Lagrangian by a suitable boundary term, whose form substantially differs in odd and even dimensions. For even dimensions, this term is given by the boundary contribution in the Euler theorem with a coupling constant fixed, demanding the spacetime to have constant (negative) curvature in the asymptotic region. For odd dimensions, the action is stationary under a boundary condition on the variation of the extrinsic curvature. A well-posed variational principle leads to an appropriate definition of energy and other conserved quantities using the Noether theorem, and to a correct description of black hole thermodynamics. In particular, this procedure assigns a nonzero energy to anti–de Sitter spacetime in all odd dimensions.

The spherically symmetric, static space-time generated by a crossflow of noninteracting radiation streams, treated in the geometrical optics limit (null dust), is equivalent to an anisotropic fluid forming a radiation atmosphere of a star. This reference fluid provides a preferred/internal time, which is employed as a canonical coordinate. Among the advantages we encounter a new Hamiltonian constraint, which becomes linear in the momentum conjugate to the internal time (therefore yielding a functional Schrödinger equation after quantization), and a strongly commuting algebra of the new constraints.

The evolution of gauge invariant second-order scalar perturbations in a general single field inflationary scenario are presented. Different second-order gauge-invariant expressions for the curvature are considered. We evaluate perturbatively one of these second order curvature fluctuations and a second-order gauge-invariant scalar field fluctuation during the slow-roll stage of a massive chaotic inflationary scenario, taking into account the deviation from a pure de Sitter evolution and considering only the contribution of super-Hubble perturbations in mode-mode coupling. The spectra resulting from their contribution to the second order quantum correlation function are nearly scale-invariant, with additional logarithmic corrections with respect to the first order spectrum. For all scales of interest the amplitude of these spectra depends on the total number of e-folds. We find, on comparing first and second order perturbation results, an upper limit to the total number of e-folds beyond which the two orders are comparable.

We calculate the flavor-singlet contribution to the $B\to {\eta }^{(\prime )}$ transition form factors from the gluonic content of the ${\eta }^{(\prime )}$ meson in the large-recoil region using the perturbative QCD approach. The formulation for the $\eta \mathrm{\text{−}}{\eta }^{\prime }$ mixing in the quark-flavor and singlet-octet schemes is compared, and employed to determine the chiral enhancement scales associated with the two-parton twist-3 ${\eta }^{(\prime )}$ meson distribution amplitudes. It is found that the gluonic contribution is negligible (around 5%) in the $B\to \eta$ form factors, but reaches 10%–40% in the $B\to {\eta }^{\prime }$ ones. Its impact on the accommodation of the measured $B\to {\eta }^{(\prime )}K$ branching ratios in the perturbative QCD and QCD-improved factorization approaches is elaborated.

We consider chiral loop corrections to the effective couplings which describe the strong interactions of two heavy mesons of even or odd parities and a light pseudoscalar meson, within a framework which combines heavy quark effective theory and chiral perturbation theory. The strong couplings are extracted from the experimental results for the decay widths, after including chiral corrections. We find that the introduction of positive parity heavy meson fields into the framework gives relevant contributions to the chiral loop corrections of the effective couplings. The counterterms’ contributions are studied by making a randomized fit distribution of the relevant couplings at $\mu \simeq 1\mathrm{GeV}$. Then we discuss the chiral extrapolation based on calculated loop contributions. The inclusion of positive parity mesons in the chiral loops is found to be important for the lattice QCD studies of charm meson properties, where the knowledge of chiral limit behavior is required.

We consider in the soft-collinear effective theory semi-inclusive hadronic $B$ decays, $B\to XM$, in which an energetic light meson $M$ near the endpoint recoils against an inclusive jet $X$. We focus on a subset of decays where the spectator quark from the $B$ meson ends up in the jet. The branching ratios and direct $CP$ asymmetries are computed to next-to-leading order accuracy in ${\alpha }_s$ and to leading order in $1/m_b$. The contribution of charming penguins is extensively discussed, and a method to extract it in semi-inclusive decays is suggested. Subleading $1/m_b$ corrections and $SU(3)$ breaking effects are discussed.

We perform a complete and detailed analysis of the flavor changing neutral current rare top quark decays $t\to c{l}^{+}{l}^{-}$ and $t\to c{\nu }_i{\overline{\nu }}_i$ at one-loop level in the standard model, two Higgs doublet models (I and II), and in minimal supersymmetric standard model (MSSM). The branching ratios are very small in all models, $\mathcal{O}({10}^{-14})$, except for the case of the unconstrained MSSM, where they can reach $\mathcal{O}({10}^{-6})$ for $e^{+}{e}^{-}$, ${\mu }^{+}{\mu }^{-}$, and ${\nu }_i{\overline{\nu }}_i$, and $\mathcal{O}({10}^{-5})$ for ${\tau }^{+}{\tau }^{-}$. This branching ratio is comparable to the ones for $t\to cV,cH$. We also study the production rates of single top and the forward-backward asymmetry in $e^{+}{e}^{-}\to t\overline{c}$ and comment on the observability of such a signal at the International Linear Collider.

In this work we present nonlinear models in two-dimensional space-time of two interacting scalar fields in the Lorentz and $CPT$ violating scenarios. We discuss the soliton solutions for these models as well as the question of stability for them. This is done by generalizing a model recently published by Barreto and collaborators and also by getting new solutions for the model introduced by them.

In this short note we present a Lagrangian formulation for free bosonic Higher Spin fields which belong to massless reducible representations of $\mathcal{D}$-dimensional anti–de Sitter group using an ambient space formalism.

We propose a construction of a 2-dimensional lattice chiral gauge theory. The construction may be viewed as a particular limit of an infinite warped 3-dimensional theory. We also present a “single-site” construction using Ginsparg-Wilson fermions which may avoid, in both 2 and 4 dimensions, the problems of waveguide-Yukawa models.

We construct a gauge-fixing procedure in the path integral for gravitational models with branes and boundaries. This procedure incorporates a set of gauge conditions which gauge away effectively decoupled diffeomorphisms acting in the ($d+1$)-dimensional bulk and on the $d$-dimensional brane. The corresponding gauge-fixing factor in the path integral factorizes as a product of the bulk and brane (surface-theory) factors. This factorization underlies a special bulk wave function representation of the brane effective action. We develop the semiclassical expansion for this action and explicitly derive it in the one-loop approximation. The one-loop brane effective action can be decomposed into the sum of the gauge-fixed bulk contribution and the contribution of the pseudodifferential operator of the brane-to-brane propagation of quantum gravitational perturbations. The gauge dependence of these contributions is analyzed by the method of Ward identities. By the recently suggested method of the Neumann-Dirichlet reduction the bulk propagator in the semiclassical expansion is converted to the Dirichlet boundary conditions preferable from the calculational viewpoint.

The field equations in $f(R)$ gravity derived from the Palatini variational principle and formulated in the Einstein conformal frame yield a cosmological term which varies with time. Moreover, they break the conservation of the energy-momentum tensor for matter, generating the interaction between matter and dark energy. Unlike phenomenological models of interacting dark energy, $f(R)$ gravity derives such an interaction from a covariant Lagrangian which is a function of a relativistically invariant quantity (the curvature scalar $R$). We derive the expressions for the quantities describing this interaction in terms of an arbitrary function $f(R)$, and examine how the simplest phenomenological models of a variable cosmological constant are related to $f(R)$ gravity. Particularly, we show that $\Lambda c^2=H^2(1-2q)$ for a flat, homogeneous and isotropic, pressureless universe. For the Lagrangian of form $R-1/R$, which is the simplest way of introducing current cosmic acceleration in $f(R)$ gravity, the predicted matter-dark energy interaction rate changes significantly in time, and its current value is relatively weak (on the order of 1% of $H_0$), in agreement with astronomical observations.

We investigate the stability of a new class of BPS cosmic strings in $N=1$ supergravity with $D$-terms recently proposed by Blanco-Pillado, Dvali and Redi. These have been conjectured to be the low energy manifestation of $D$-strings that might form from tachyon condensation after $D$- anti-$D$-brane annihilation in type IIB superstring theory. There are three one-parameter families of cylindrically symmetric one-vortex solutions to the BPS equations (tachyonic, axionic and hybrid). We find evidence that the zero mode in the axionic case, or $s$-strings, can be excited. Its evolution leads to the decompactification of four-dimensional spacetime at late times, with a rate that decreases with decreasing brane tension.

We analyze the spectrum and properties of a highly deconstructed Higgsless model with only three sites. Such a model contains sufficient complexity to incorporate interesting physics issues related to fermion masses and electroweak observables, yet remains simple enough that it could be encoded in a Matrix Element Generator program for use with Monte Carlo simulations. The gauge sector of this model is equivalent to that of the Breaking Electroweak Symmetry Strongly (BESS) model; the new physics of interest here lies in the fermion sector. We analyze the form of the fermion Yukawa couplings required to produce the ideal fermion delocalization that causes tree-level precision electroweak corrections to vanish. We discuss the size of one-loop corrections to $b\to s\gamma$, the weak-isospin violating parameter $\alpha T$ and the decay $Z\to b\overline{b}$. We find that the new fermiophobic vector states (the analogs of the gauge-boson Kaluza-Klein modes in a continuum model) can be reasonably light, with a mass as low as 380 GeV, while the extra (approximately vectorial) quark and lepton states (the analogs of the fermion Kaluza-Klein modes) must be heavier than 1.8 TeV.

We study a systematic improvement of perturbation theory for gauge fields on the lattice; the improvement entails resumming, to all orders in the coupling constant, a dominant subclass of tadpole diagrams. This method, originally proposed for the Wilson gluon action [H. Panagopoulos and E. Vicari, Phys. Rev. D 58, 114501 (1998)], is extended here to encompass all possible gluon actions made of closed Wilson loops; any fermion action can be employed as well. The effect of resummation is to replace various parameters in the action (coupling constant, Symanzik coefficients, clover coefficient) by “dressed” values; the latter are solutions to certain coupled integral equations, which are easy to solve numerically. Some positive features of this method are (a) it is gauge invariant, (b) it can be applied to improve (to all orders) results obtained at any given order in perturbation theory, (c) it does indeed absorb in the dressed parameters the bulk of tadpole contributions. Two different applications are presented: the additive renormalization of fermion masses, and the multiplicative renormalization $Z_V$ ($Z_A$) of the vector (axial) current. In many cases where nonperturbative estimates of renormalization functions are also available for comparison, the agreement with improved perturbative results is consistently better as compared to results from bare perturbation theory.