We study singlet and triplet correlation functions of a static quark-antiquark pair defined through gauge invariant timelike Wilson loops and Polyakov loop correlators in finite temperature $SU(2)$ gauge theory. We use the Lüscher-Weisz multilevel algorithm, which allows us to calculate these correlators at very low temperatures. We observe that the naive separation of singlet and triplet states, in general, does not hold nonperturbatively; however, it is recovered in the limit of small separation, and the temperature dependence of the corresponding correlators is indeed very different.

We study the constraints on possible new physics contributions to the forward-backward asymmetry of muons, $A_{\mathrm{FB}}(q^2)$, in $B\to K{\mu }^{+}{\mu }^{-}$. New physics in the form of vector/axial-vector operators does not contribute to $A_{\mathrm{FB}}(q^2)$, whereas new physics in the form of scalar/pseudoscalar operators can enhance $A_{\mathrm{FB}}(q^2)$ only by a few percent. However, new physics in the form of tensor operators can take the peak value of $A_{\mathrm{FB}}(q^2)$ to as high as 40% near the high-$q^2$ end point. In addition, if both scalar/pseudoscalar and tensor operators are present, then $A_{\mathrm{FB}}(q^2)$ can be more than 15% for the entire high-$q^2$ region $q^2>15{\mathrm{GeV}}^2$. The observation of significant $A_{\mathrm{FB}}$ would imply the presence of new physics tensor operators, whereas its $q^2$ dependence could further indicate the presence of new scalar/pseudoscalar physics.

The leading twist transverse momentum dependent parton distribution function $h_{1T}^{\perp }$ is studied. We review the theoretical properties of this function, and compute it in the bag model. We find in the bag model an interesting relation, and observe it to hold also in other relativistic models: The difference between helicity and transversity distributions, often said to be a ’measure of relativistic effects’ in the nucleon, is related to $h_{1T}^{\perp }$. This function is chirally odd and can be accessed in combination with the Collins effect in semi-inclusive deep-inelastic scattering, where it gives rise to an azimuthal single spin asymmetry proportional to $\sin (3\varphi -{\varphi }_S)$. We discuss preliminary COMPASS data on that observable and make predictions for future experiments on various targets at JLab, COMPASS, and HERMES.

We explore an alternative process for diffractive Higgs boson production in peripheral $pp$ collisions arising from double Pomeron exchange in photon-proton interaction. We introduce the impact factor formalism in order to enable the gluon ladder exchange in the photon-proton subprocess, and to permit central Higgs production. The event rate for diffractive Higgs production in central rapidity is estimated to be about 0.6 pb at Tevatron and LHC energies. This result is higher than predictions from other approaches of diffractive Higgs production, showing that the alternative production process leads to an enhanced signal for the detection of the Higgs boson at hadron colliders. Our results are compared with those obtained from a similar approach proposed by the Durham Group. In this way, we may examine future developments in its application to $pp$ and $AA$ collisions.

We calculate the shear viscosity of field theories with gravity duals using Kubo formula by calculating the Green function of dual transverse gravitons and confirm that the value of the shear viscosity is fully determined by the effective coupling of transverse gravitons on the horizon. We calculate the effective coupling of transverse gravitons for Einstein and Gauss-Bonnet gravities coupled with matter fields, respectively. Then we apply the resulting formula to the case of AdS Gauss-Bonnet gravity with $F^4$ term corrections of Maxwell field and discuss the effect of $F^4$ terms on the ratio of the shear viscosity to entropy density.

We consider renormalization of the central charge and the mass of the $\mathcal{N}=2$ supersymmetric Abelian vortices in $2+1$ dimensions. We obtain $\mathcal{N}=2$ supersymmetric theory in $2+1$ dimensions by dimensionally reducing the $\mathcal{N}=1$ supersymmetric QED in $3+1$ dimensions with two chiral fields carrying opposite charges. Then we introduce a mass for one of the matter multiplets without breaking $\mathcal{N}=2$ supersymmetry. This massive multiplet is viewed as a regulator in the large mass limit. We show that the mass and the central charge of the vortex get the same nonvanishing quantum corrections, which preserves Bogomol’nyi-Prasad-Sommerfield saturation at the quantum level. Comparison with the operator form of the central extension exhibits fractionalization of a global U(1) charge; it becomes $\pm 1/2$ for the minimal vortex. The very fact of the mass and charge renormalization is due to a “reflection” of an unbalanced number of the fermion and boson zero modes on the vortex in the regulator sector.

We evaluate the tree level four fermion string amplitudes in the TeV string mass scale models with intersecting $D6$-branes. The coefficient functions of contact interactions subsuming the contributions of string Regge resonance and winding mode excitations are obtained by subtracting out the contributions from the string massless and massive momentum modes. Numerical applications are developed for the standard-model-like solution of Cremades, Ibanez, and Marchesano for a toroidal orientifold with four intersecting $D6$-brane stacks. The chirality conserving contact interactions of the quarks and leptons are considered in applications to high-energy collider and flavor changing neutral current phenomenology. The two main free parameters consist of the string and compactification mass scales, $m_s$ and $M_c$. Useful constraints on these parameters are derived from predictions for the Bhabha scattering differential cross section and for the observables associated to the mass shifts of the neutral meson systems $K-\overline{K}$, $B-\overline{B}$, $D-\overline{D}$ and the lepton number violating three-body leptonic decays of the charged leptons $\mu$ and $\tau$.

Analytic methods show stability of the stationary accretion of test fluids but they are inconclusive in the case of self-gravitating stationary flows. We investigate numerically stability of those stationary flows onto compact objects that are trans-sonic and rich in gas. In all studied examples solutions appear stable. Numerical investigation suggests also that the analogy between sonic and event horizons holds for small perturbations of compact support but fails in the case of finite perturbations.

Numerical relativity has recently yielded a plethora of results about kicks from spinning mergers which has, in turn, vastly increased our knowledge about the spin interactions of black hole systems. In this work we use black hole perturbation theory to calculate accurately the gravitational waves emanating from the end of the plunging stage of an extreme mass ratio merger in order to further understand this phenomenon. This study focuses primarily on spin induced effects with emphasis on the maximally spinning limit and the identification of possible causes of generic behavior. We find that gravitational waves emitted during the plunging phase exhibit damped oscillatory behavior, corresponding to a coherent excitation of quasinormal modes by the test particle. This feature is universal in the sense that the frequencies and damping time do not depend on the orbital parameters of the plunging particle. Furthermore, the observed frequencies are distinct from those associated with the usual free quasinormal ringing. Our calculation suggests that a maximum in radiated energy and momentum occurs at spin parameters equal to $a/M=0.86$ and $a/M=0.81$, respectively, for the plunge stage of a polar orbit. The dependence of linear momentum emission on the angle at which a polar orbit impacts the horizon is quantified. One of the advantages of the perturbation approach adopted here is that insight into the actual mechanism of radiation emission and its relationship to black hole ringing is obtained by carefully identifying the dominant terms in the expansions used.

The full metric describing two counter-rotating identical Kerr black holes separated by a massless strut is derived in the explicit analytical form. It contains three arbitrary parameters which are the Komar mass $M$, Komar angular momentum per unit mass $a$ of one of the black holes (the other has the same mass and equal but opposite angular momentum) and the coordinate distance $R$ between the centers of the horizons. In the limit of extreme black holes, the metric becomes a special member of the Kinnersly-Chitre five-parameter family of vacuum solutions generalizing the Tomimatsu-Sato $\delta =2$ spacetime, and we present the complete set of metrical fields defining this limit.

A quasi-black hole, either nonextremal or extremal, can be broadly defined as the limiting configuration of a body when its boundary approaches the body’s quasihorizon. We consider the mass contributions and the mass formula for a static quasi-black hole. The analysis involves careful scrutiny of the surface stresses when the limiting configuration is reached. It is shown that there exists a strict correspondence between the mass formulas for quasi-black holes and pure black holes. This perfect parallelism exists in spite of the difference in derivation and meaning of the formulas in both cases. For extremal quasi-black holes the finite surface stresses give zero contribution to the total mass. This leads to a very special version of Abraham-Lorentz electron in general relativity in which the total mass has pure electromagnetic origin in spite of the presence of bare stresses.

We carry out a suite of cosmological simulations of modified action $f(R)$ models where cosmic acceleration arises from an alteration of gravity instead of dark energy. These models introduce an extra scalar degree of freedom which enhances the force of gravity below the inverse mass or Compton scale of the scalar. The simulations exhibit the so-called chameleon mechanism, necessary for satisfying local constraints on gravity, where this scale depends on environment, in particular, the depth of the local gravitational potential. We find that the chameleon mechanism can substantially suppress the enhancement of power spectrum in the nonlinear regime if the background field value is comparable to or smaller than the depth of the gravitational potentials of typical structures. Nonetheless power spectrum enhancements at intermediate scales remain at a measurable level for models even when the expansion history is indistinguishable from a cosmological constant, cold dark matter model. Simple scaling relations that take the linear power spectrum into a nonlinear spectrum fail to capture the modifications of $f(R)$ due to the change in collapsed structures, the chameleon mechanism, and the time evolution of the modifications.

We introduce the method and the implementation of a cosmological simulation of a class of metric-variation $f(R)$ models that accelerate the cosmological expansion without a cosmological constant and evade solar-system bounds of small-field deviations to general relativity. Such simulations are shown to reduce to solving a nonlinear Poisson equation for the scalar degree of freedom introduced by the $f(R)$ modifications. We detail the method to efficiently solve the nonlinear Poisson equation by using a Newton-Gauss-Seidel relaxation scheme coupled with the multigrid method to accelerate the convergence. The simulations are shown to satisfy tests comparing the simulated outcome to analytical solutions for simple situations, and the dynamics of the simulations are tested with orbital and Zeldovich collapse tests. Finally, we present several static and dynamical simulations using realistic cosmological parameters to highlight the differences between standard physics and $f(R)$ physics. In general, we find that the $f(R)$ modifications result in stronger gravitational attraction that enhances the dark matter power spectrum by $\sim 20\%$ for large but observationally allowed $f(R)$ modifications. A more detailed study of the nonlinear $f(R)$ effects on the power spectrum are presented in a companion paper.

We extend the results of a previous paper where a model of interacting dark energy, with a cosmological term decaying linearly with the Hubble parameter, is tested against the observed mass power spectrum. In spite of the agreement with observations of type Ia supernovas, baryonic acoustic oscillations, and the cosmic microwave background, we had shown previously that no good concordance is achieved if we include the mass power spectrum. However, our analysis was based on the ad hoc assumption that the interacting cosmological term is strictly homogeneous. Now we perform a more complete analysis, by perturbing such a term. Although our conclusions are still based on a particular, scale-invariant choice of the primordial spectrum of dark energy perturbations, we show that a cosmological term decaying linearly with the Hubble parameter is indeed disfavored as compared to the standard model.

We determine characteristic time scales for the viscous damping of $r$-mode oscillations in rapidly rotating compact stars that contain quark matter. We present results for the color-flavor-locked (CFL) phase of dense quark matter, in which the up, down, and strange quarks are gapped, as well as the normal (ungapped) quark phase. While the ungapped quark phase supports a temperature window ${10}^8\mathrm{K}\le T\le 5\times {10}^9\mathrm{K}$ where the $r$ mode is damped even for rapid rotation, the $r$ mode in a rapidly rotating pure CFL star is not damped in the temperature range ${10}^{10}\mathrm{K}\le T\le {10}^{11}\mathrm{K}$. Rotating hybrid stars with quark matter cores display an instability window whose width is determined by the amount of quark matter present, and they can have large spin frequencies outside this window. Except at high temperatures $T\ge {10}^{10}\mathrm{K}$, the presence of a quark phase allows for larger critical frequencies and smaller spin periods compared to rotating neutron stars. If low-mass x-ray binaries contain a large amount of ungapped or CFL quark matter, then our estimates of the $r$-mode instability suggest that there should be a population of rapidly rotating binaries at $\nu \gtrsim 1000\mathrm{Hz}$ which have not yet been observed.

We derive the equations of motion of test bodies for a theory with nonminimal coupling by means of a multipole method. The propagation equations for pole-dipole particles are worked out for a gravity theory with a very general coupling between the curvature scalar and the matter fields. Our results allow for a systematic comparison with the equations of motion of general relativity and other gravity theories.

We propose an extension of the standard model with a $U(1{)}_{\mathrm{B}-\mathrm{L}}$ global symmetry that accommodates radiative neutrino masses along with dark matter and leptogenesis. The observed matter-antimatter asymmetry of the Universe is generated through the leptogenesis route keeping the $U(1{)}_{\mathrm{B}-\mathrm{L}}$ symmetry intact. The B-L global symmetry is then softly broken, providing the subeV neutrino masses. The model then incorporates a MeV scale sterile-neutrino-like dark matter.

In this work we investigate the contribution to $B_{d,s}$ mixing from both scalar and vector unparticles in a number of scenarios. The emphasis of this work is to show the impact of the recently discovered $3\sigma$ evidence for new physics found in the $CP$ phase of $B_s$ mixing. Here we show that the inclusion of the $CP$ phase constraints for both $B_d$ and $B_s$ mixing improves the bounds set on the unparticle couplings by a factor of $2\sim 4$, and one particular scenario of scalar unparticles is found to be excluded by the $3\sigma$ measurement of ${\varphi }_s$.

A model for the $p(e,e^{\prime }{\pi }^{+})n$ reaction which combines an improved treatment of gauge invariant meson-exchange currents and hard deep-inelastic scattering (DIS) of virtual photons off nucleons is proposed. It is shown that DIS dominates and explains the transverse response at moderate and high photon virtualities $Q^2$, whereas the longitudinal response is dominated by hadronic degrees of freedom and the pion electromagnetic form factor. This leads to a combined description of the longitudinal and transverse components of the cross section in a wide range of photon virtuality $Q^2$ and momentum transfer to the target $t$ and solves the longstanding problem of the observed large transverse cross sections. The latter are shown to be sensitive to the intrinsic transverse momentum distribution of partons.

The phase diagram of a two-flavor Polyakov-loop Nambu–Jona-Lasinio model is analyzed imposing the constraint of color charge neutrality. The main effect of this constraint is a coexistence of the chiral symmetry breaking ($\chi \mathrm{SB}$) and two-flavor superconducting phases. Additional effects are a shrinking of the $\chi \mathrm{SB}$ domain in the $T-\mu$ plane and a shift of the end point to lower temperatures, but their quantitative importance is shadowed by the intrinsic uncertainties of the model. The effects can be understood in view of the presence of a nonvanishing color chemical potential ${\mu }_8$, which is introduced to compensate the color charge density ${\rho }_8$ induced by a background color gauge mean field ${\varphi }_3$. At low temperatures and large chemical potentials the model exhibits a quarkyonic phase, which gets additional support from the diquark condensation.