An analysis is given of the Stueckelberg extension of the standard model with a hidden sector gauge group $U(1{)}_X$ where the mass growth for the extra gauge boson occurs via the Stueckelberg mechanism, and where the kinetic mixing in the $U(1{)}_X\times U(1{)}_Y$ sector is included. Such a kinetic mixing is generic in a broad class of supergravity and string models. We carry out a detailed global fit of the model with the precision CERN LEP data on and off the $Z$ pole, with ${\chi }^2$ within 1% of the ${\chi }^2$ of the standard model fit. Further, it is shown that, in the absence of matter in the hidden sector, there is a single effective parameter that controls the deviations from the standard model predictions, and the dependence on the kinetic mixing emerges only when matter in the hidden sector is included. An analysis is also given of millicharged dark matter arising from the hidden sector, where it is shown that such dark matter from the Stueckelberg extension can satisfy WMAP-3 data while allowing for a sharp $Z^{\prime }$ resonance which can be detected at the Tevatron and at the CERN LHC via a dilepton signal generated by the Drell-Yan process.

We evaluate the energy-momentum tensor of a massive quark as it moves through an $\mathcal{N}=4$ SYM quark-gluon plasma at constant velocity. We find that in the near-quark region, where the dynamics is expected to be dominated by dissipative behavior, the energy density may be quantitatively characterized by a transient at velocities above the speed of sound of the plasma.

We explore some general consequences of a proper, full enforcement of the “twisted Poincaré” covariance of Chaichian et al., Wess, Koch et al., and Oeckl upon many-particle quantum mechanics and field quantization on a Moyal-Weyl noncommutative space(time). This entails the associated braided tensor product with an involutive braiding (or $\star$-tensor product in the parlance of Aschieri et al.) prescription for any coordinate pair of $x$, $y$ generating two different copies of the space(time); the associated nontrivial commutation relations between them imply that $x-y$ is central and its Poincaré transformation properties remain undeformed. As a consequence, in quantum field theory (QFT) (even with space-time noncommutativity) one can reproduce notions (like spacelike separation, time- and normal-ordering, Wightman or Green’s functions, etc.), impose constraints (Wightman axioms), and construct free or interacting theories which essentially coincide with the undeformed ones, since the only observable quantities involve coordinate differences. In other words, one may thus well realize quantum mechanics (QM) and QFT’s where the effect of space(time) noncommutativity amounts to a practically unobservable common noncommutative translation of all reference frames.

In this paper we have studied the nature of kinematical and dynamical laws in $\kappa$-Minkowski spacetime from a new perspective: the canonical phase space approach. We discuss a particular form of $\kappa$-Minkowski phase space algebra that yields the $\kappa$-extended finite Lorentz transformations derived in [D. Kimberly, J. Magueijo, and J. Medeiros, Phys. Rev. D 70, 084007 (2004).]. This is a particular form of a deformed special relativity model that admits a modified energy-momentum dispersion law as well as noncommutative $\kappa$-Minkowski phase space. We show that this system can be completely mapped to a set of phase space variables that obey canonical (and not $\kappa$-Minkowski) phase space algebra and special relativity Lorentz transformation (and not $\kappa$-extended Lorentz transformation). The complete set of deformed symmetry generators are constructed that obeys an unmodified closed algebra but induce deformations in the symmetry transformations of the physical $\kappa$-Minkowski phase space variables. Furthermore, we demonstrate the usefulness and simplicity of this approach through a number of phenomenological applications both in classical and quantum mechanics. We also construct a Lagrangian for the $\kappa$-particle.

We study the evaporation process of black strings which are typical examples of Kaluza-Klein black holes. Taking into account the backreaction of the Hawking radiation, we deduce the evolution equation for the radion field. By solving the evolution equation, we find that the shape of the internal space is necked by the Hawking radiation and the amount of the deformation becomes large as the evaporation proceeds. Based on this analysis, we speculate that the Kaluza-Klein black holes would be excised from the Kaluza-Klein spacetime before the onset of the Gregory-Laflamme instability and therefore before the evaporation.

We study the collision of two flat, parallel end-of-the-world branes in heterotic M theory. By insisting that there is no divergence in the Riemann curvature as the collision approaches, we are able to single out a unique solution possessing the local geometry of (2d compactified Milne)/${\mathbb{Z}}_2\times {\mathbb{R}}_3$, times a finite-volume Calabi-Yau manifold in the vicinity of the collision. At a finite time before and after the collision, a second type of singularity appears momentarily on the negative-tension brane, representing its bouncing off a zero of the bulk warp factor. We find this singularity to be remarkably mild and easily regularized. The various different cosmological solutions to heterotic M theory previously found by other authors are shown to merely represent different portions of a unique flat cosmological solution to heterotic M theory.

We calculate the thermal conductivity of electrons and muons ${\kappa }_{e\mu }$ produced due to electromagnetic interactions of charged particles in neutron star cores and show that these interactions are dominated by the exchange of transverse plasmons (via the Landau damping of these plasmons in nonsuperconducting matter and via a specific plasma screening in the presence of proton superconductivity). For normal protons, the Landau damping strongly reduces ${\kappa }_{e\mu }$ and makes it temperature independent. Proton superconductivity suppresses the reduction and restores the Fermi-liquid behavior ${\kappa }_{e\mu }\propto T^{-1}$. Comparing with the thermal conductivity of neutrons ${\kappa }_n$, we obtain ${\kappa }_{e\mu }\gtrsim {\kappa }_n$ for $T\gtrsim 2\times {10}^9\mathrm{K}$ in normal matter and for any $T$ in superconducting matter with proton critical temperatures $T_{cp}\gtrsim 3\times {10}^9\mathrm{K}$. The results are described by simple analytic formulae.

We analyze the interaction of the plane ‘$+$’-polarized gravitational waves with a Fabry-Perot cavity in the local Lorentz frame of the cavity’s input mirror outside of the range of long-wave approximation with the force of radiation pressure taken into account. The obtained detector’s response signal is represented as a sum of two parts: (i) the phase shift due to displacement of a movable mirror under the influence of a gravitational wave and the force of light pressure, and (ii) the phase shift due to the direct interaction of a gravitational wave with light wave inside the cavity. We obtain the formula for the movable mirror’s law of motion paying close attention to the phenomena of optical rigidity, radiative friction, and direct coupling of a gravitational wave to light wave. Some issues concerning the detection of high-frequency gravitational waves and the role of optical rigidity in it are discussed. We also examine in detail special cases of optical resonance and small detuning from it and compare our results with the known ones.

TeV scale mirage mediation has been proposed as a supersymmetry-breaking scheme reducing the fine-tuning for electroweak symmetry breaking in the minimal supersymmetric extension of the standard model. We discuss a moduli stabilization setup for TeV scale mirage mediation which allows an extradimensional interpretation for the origin of supersymmetry breaking and naturally gives a weak-scale size of the Higgs $B$ parameter. The setup utilizes the holomorphic gauge kinetic functions depending on both the heavy dilaton and the light volume modulus whose axion partners are assumed to be periodic fields. We also examine the low-energy phenomenology of TeV scale mirage mediation, particularly the constraints from electroweak symmetry breaking and flavor changing neutral current processes.

Using a multicanonical Metropolis algorithm we have performed Monte Carlo simulations of the 3D 3-state Potts model on $L^3$ lattices with $L=20$, 30, 40, 50. Covering a range of inverse temperatures from ${\beta }_{\min }=0$ to ${\beta }_{\max }=0.33$ we calculated the infinite volume limit of the entropy density $s(\beta )$ with its normalization obtained from $s(0)=\ln 3$. At the transition temperature the entropy and energy endpoints in the ordered and disordered phase are estimated employing a novel reweighting procedure. We also evaluate the transition temperature and the order-disorder interface tension. The latter estimate increases when capillary waves are taken into account.

We report results for the interaction measure, pressure, and energy density for nonzero-temperature QCD with $2+1$ flavors of improved staggered quarks. In our simulations, we use a Symanzik improved gauge action and the Asqtad $O(a^2)$ improved staggered quark action for lattices with temporal extent $N_t=4$ and 6. The heavy quark mass $m_s$ is fixed at approximately the physical strange quark mass and the two degenerate light quarks have masses $m_{ud}\approx 0.1m_s$ or $0.2m_s$. The calculation of the thermodynamic observables employs the integral method where energy density and pressure are obtained by integration over the interaction measure.

We present a study of the pseudoscalar and vector meson form factors, calculated using the fat-link irrelevant clover (FLIC) action in the framework of quenched lattice QCD. Of particular interest is the determination of a negative quadrupole moment, indicating that the $\rho$ meson is not spherically symmetric.

We study $pp$ and $p\overline{p}$ collisions which lead to the exclusive production of $J/\psi$ or ${\rm Y}$ from the pomeron-odderon and the pomeron-photon fusion. We calculate scattering amplitudes of these processes in the lowest-order approximation and in the framework of $k_{\perp }$ factorization. We present estimates of cross sections for the kinematic conditions of the Tevatron and of the LHC.

Phenomenological models of the dipole cross section that enters in the description of for instance deep inelastic scattering at very high energies have had considerable success in describing the available small-$x$ data in both the saturation region and the so-called extended geometric scaling (EGS) region. We investigate to what extent such models are compatible with the numerical solutions of the Balitsky-Kovchegov (BK) equation which is expected to describe the nonlinear evolution in $x$ of the dipole cross section in these momentum regions. We find that in the EGS region the BK equation yields results that are qualitatively different from those of phenomenological studies. In particular, geometric scaling around the saturation scale is only obtained at asymptotic rapidities. We find that in this limit the anomalous dimension $\gamma (r,x)$ of phenomenological models approaches a limiting function that is universal for a large range of initial conditions. At the saturation scale, this function equals approximately 0.44, in contrast to the value 0.628 commonly used in the models. We further investigate the dependence of these results on the starting distribution, the small-$r$ limit of the anomalous dimension for fixed rapidities and the $x$-dependence of the saturation scale.

In this work we estimate the differential and total cross sections for the high-energy deeply virtual Compton scattering in the weak sector. In the weak neutral sector one considers neutrino scattering off an unpolarized proton target through the exchange of $Z^0$. We numerically compute the process $Z^{*}p\to \gamma p$ within the QCD color dipole formalism, which successfully describes the current high-energy electromagnetic DVCS experimental data. We also discuss possible applications for the weak charged sector and perform predictions for scattering on nuclear targets.

We present improved measurements of the branching fraction and $CP$ asymmetry for the process $B^{\pm }\to {\rho }^{\pm }{\pi }^0$. The data sample corresponding to $211{\mathrm{fb}}^{-1}$ comprises $232\times {10}^6$ $\mathit{{\rm Y}}(4S)\to B\overline{B}$ decays collected with the BABAR detector at the PEP-II asymmetric $B$ Factory at SLAC. The yield and $CP$ asymmetry are measured using an extended maximum likelihood fitting method. The branching fraction and $CP$ asymmetry are found to be $\mathcal{B}(B^{\pm }\to {\rho }^{\pm }{\pi }^0)=[10.2\pm 1.4(\mathrm{stat})\pm 0.9(\mathrm{syst})]\times {10}^{-6}$ and ${\mathcal{A}}_{CP}(B^{\pm }\to {\rho }^{\pm }{\pi }^0)=-0.01\pm 0.13(\mathrm{stat})\pm 0.02(\mathrm{syst})$.

We continue to investigate properties of the worldsheet conformal field theories (CFTs) which are conjectured to be dual to free large $N$ gauge theories, using the mapping of Feynman diagrams to the worldsheet suggested in [R. Gopakumar, Phys. Rev. D 70, 025009 (2004); R. GopakumarPhys. Rev. D70, 025010 (2004); R. GopakumarC. R. Physique 5, 1111 (2004); R. GopakumarPhys. Rev. D 72, 066008 (2005)]. The modular invariance of these CFTs is shown to be built into the formalism. We show that correlation functions in these CFTs which are localized on subspaces of the moduli space may be interpreted as delta-function distributions, and that this can be consistent with a local worldsheet description given some constraints on the operator product expansion coefficients. We illustrate these features by a detailed analysis of a specific four-point function diagram. To reliably compute this correlator, we use a novel perturbation scheme which involves an expansion in the large dimension of some operators.

The equation of motion for massive particles in $f(R)$ modified theories of gravity is derived. By considering an explicit coupling between an arbitrary function of the scalar curvature, $R$, and the Lagrangian density of matter, it is shown that an extra force arises. This extra force is orthogonal to the four-velocity and the corresponding acceleration law is obtained in the weak-field limit. Connections with MOND and with the Pioneer anomaly are further discussed.

The comprehensive analyses are presented in the model with the inverted mass hierarchy for neutrinos, which follows from a geometrical structure of a ($1+5$) dimensional space-time where two extra dimensions are compactified on the ${\mathbf{T}}^{\mathbf{2}}/{\mathbf{Z}}_{\mathbf{3}}$ orbifold. The model gives two large lepton flavor mixings due to the $S_3$ structure in the ($1+5$) dimensional space-time. It also predicts the lightest neutrino mass as $m_3=(1–50)\times {10}^{-5}\mathrm{eV}$ and the effective neutrino mass responsible for neutrinoless double beta decays as $⟨m{⟩}_{ee}\simeq 50\mathrm{meV}$. The low energy $CP$ violation, $J_{CP}$ could be 0.02. On the other hand, the observed baryon asymmetry in the present universe is produced by the nonthermal leptogenesis, which works even at the reheating temperature $T_R={10}^4–{10}^6\mathrm{GeV}$. The correlation between the baryon asymmetry and the low energy $CP$ violation is examined in this model.

We use results by Kirilin to comment that in general relativity the nonleading terms in the energy-momentum tensor of a particle depends on the parameterization of the gravitational field. The classical observables are parameterization independent after a change in coordinates. The quantum effects that emerge within the same calculation of the metric also depend on the parameterization and a full quantum calculation requires the inclusion of further diagrams. However, within a given parameterization the quantum effects calculated by us in a previous paper are well defined. Flaws of Kirilin’s proposed alternate metric definition are described and we explain why the diagrams that we calculated are the appropriate ones.