Cascading gauge theories of Klebanov et al. provide a model within a framework of gauge theory/string theory duality for a four-dimensional nonconformal gauge theory with a spontaneously generated mass scale. Using the dual supergravity description, we study sound wave propagation in strongly coupled cascading gauge theory plasma. We analytically compute the speed of sound and the bulk viscosity of cascading gauge theory plasma at a temperature much larger than the strong coupling scale of the theory. The sound wave dispersion relation is obtained from the hydrodynamic pole in the stress-energy tensor two-point correlation function. The speed of sound extracted from the pole of the correlation function agrees with its value computed in Phys. Rev. D 72, 066003 (2005), using the equation of state. We find that the bulk viscosity of the hot cascading gauge theory plasma is nonzero at the leading order in the deviation from conformality.

In string theory realizations of inflation, the endpoint of inflation is often brane-antibrane annihilation. We consider the processes of reheating of the standard model universe after brane inflation. We identify the channels of inflaton energy decay, cascading from tachyon annihilation through massive closed string loops, KK modes, and brane displacement moduli to the lighter standard model particles. Cosmological data constrains scenarios by putting stringent limits on the fraction of reheating energy deposited in gravitons and nonstandard sector massive relics. We estimate the energy deposited into various light degrees of freedom in the open and closed string sectors, the timing of reheating, and the reheating temperature. Production of gravitons is significantly suppressed in warped inflation. However, we predict a residual gravitational radiation background at the level ${\Omega }_{\mathrm{GW}}\sim {10}^{-8}$ of the present cosmological energy density. We also extend our analysis to multiple throat scenarios. A viable reheating would be possible in a single throat or in a certain subclass of multiple throat scenarios of the KKLMMT type inflation model, but overproduction of massive Kaluza-Klein (KK) modes poses a serious problem. The problem is quite severe if some inner manifold comes with approximate isometries (angular KK modes) or if there exists a throat of modest length other than the standard model throat, possibly associated with some hidden sector (low-lying KK modes).

We discuss the fate of the $Z_2$ symmetry and the vacuum structure in a $\mathrm{SU}(N)\times \mathrm{SU}(N)$ gauge theory with one bifundamental Dirac fermion. This theory can be obtained from $\mathrm{SU}(2N)$ supersymmetric Yang-Mills theory by virtue of $Z_2$ orbifolding. We analyze dynamics of domain walls and argue that the $Z_2$ symmetry is spontaneously broken. Since unbroken $Z_2$ is a necessary condition for nonperturbative planar equivalence we conclude that the orbifold daughter is nonperturbatively nonequivalent to its supersymmetric parent. En route, our investigation reveals the existence of fractional domain walls, similar to fractional D-branes of string theory on orbifolds. We conjecture on the fate of these domain walls in the true solution of the $Z_2$-broken orbifold theory. We also comment on relation with nonsupersymmetric string theories and closed-string tachyon condensation.

We give a detailed and improved presentation of our recently proposed formalism for nonlinear perturbations in cosmology, based on a covariant and fully nonperturbative approach. We work, in particular, with a covector combining the gradients of the energy density and of the local number of e-folds to obtain a nonlinear generalization of the familiar linear uniform-density perturbation. We show that this covector obeys a remarkably simple conservation equation which is exact, fully nonlinear and valid at all scales. We relate explicitly our approach to the coordinate-based formalisms for linear perturbations and for second-order perturbations. We also consider other quantities, which are conserved on sufficiently large scales for adiabatic perturbations, and discuss the issue of gauge invariance.

The results of 720 hours of observation of transient solar events at ground level during the summer season of 2005 in the southern hemisphere are presented. Data were taken with the TUPI muon telescope working at a high counting rate of up to 100 KHz and always pointing to the IMF lines at 45 degrees of pitch angle. An anticorrelation between the arrival of the KeV protons observed by EPAM detector aboard the ACE spacecraft and sudden depressions in the muon flux at sea level has been observed. The phenomenon is discussed in the context that it can be considered as mini-Forbush, caused by a shielding effect of the passage of a disturbance (shock and plasma). It may be regarded as a signature of interplanetary manifestations of coronal mass ejections, as well as corotating high speed streams.

Decay rates and time-dependent and direct $CP$ asymmetries in the decays $B^0\to K^{+}{K}^{-}{K}_{S(L)}$ and $K_S{K}_S{K}_{S(L)}$ are studied. Resonant and nonresonant contributions to the three-body decays are carefully investigated. Nonresonant effects on two-body and three-body matrix elements are constrained by QCD counting rules. The predicted branching ratios are consistent with the data within the theoretical and experimental errors, though the theoretical central values are somewhat smaller than the experimental ones. Owing to the presence of color-allowed tree amplitudes in $B^0\to K^{+}{K}^{-}{K}_{S(L)}$, this penguin-dominated mode may be subject to a potentially significant tree pollution and the deviation of the mixing-induced $CP$ asymmetry from that measured in $B\to J/\psi K_S$, namely, $\Delta \sin 2{\beta }_{K^{+}{K}^{-}{K}_{S(L)}}\equiv \sin 2{\beta }_{K^{+}{K}^{-}{K}_{S(L)}}-\sin 2{\beta }_{J/\psi K_S}$, can be as large as $\mathcal{O}(0.10)$. In contrast, the $K_S{K}_S{K}_{S(L)}$ modes appear theoretically very clean in our picture with negligible theoretical errors in $\Delta \sin 2{\beta }_{K_S{K}_S{K}_{S(L)}}$. Direct $CP$ asymmetries in $K^{+}{K}^{-}{K}_{S(L)}$ and $K_S{K}_S{K}_{S(L)}$ modes are found to be very small.

In this paper, we discuss the transition to the semiclassical regime in excited hadrons, and consequently, the restoration of chiral symmetry for these states. We use a generalized Nambu–Jona-Lasinio model with the interaction between quarks in the form of the instantaneous Lorentz-vector confining potential. This model is known to provide spontaneous breaking of chiral symmetry in the vacuum via the standard self-energy loops for valence quarks. It has been shown recently that the effective single-quark potential is of the Lorentz-scalar nature, for the low-lying hadrons, while, for the high-lying states, it becomes a pure Lorentz vector and hence the model exhibits the restoration of chiral symmetry. We demonstrate explicitly the quantum nature of chiral symmetry breaking, the absence of chiral symmetry breaking in the classical limit, as well as the transition to the semiclassical regime for excited states, where the effect of chiral symmetry breaking becomes only a small correction to the classical contributions.

A previous calculation of electroweak $\mathcal{O}(\alpha )$ corrections to deep-inelastic neutrino scattering, as e.g. measured by NuTeV and NOMAD, is supplemented by higher-order effects. In detail, we take into account universal two-loop effects from $\Delta \alpha$ and $\Delta \rho$ as well as higher-order final-state photon radiation off muons in the structure function approach. Moreover, we make use of the recently released $\mathcal{O}(\alpha )$-improved parton distributions MRST2004QED and identify the relevant QED factorization scheme, which is DIS-like. As a technical by-product, we describe slicing and subtraction techniques for an efficient calculation of a new type of real corrections that are induced by the generated photon distribution. A numerical discussion of the higher-order effects suggests that the remaining theoretical uncertainty from unknown electroweak corrections is dominated by nonuniversal two-loop effects and is of the order 0.0003 when translated into a shift in ${sin}^2{\theta }_{\mathrm{W}}=1-M_{\mathrm{W}}^2/M_{\mathrm{Z}}^2$. The $\mathcal{O}(\alpha )$ corrections implicitly included in the parton distributions lead to a shift of about 0.0004.

We discuss the issue of parity violation in quantum gravity. In particular, we study the coupling of fermionic degrees of freedom in the presence of torsion and the physical meaning of the Immirzi parameter from the viewpoint of effective field theory. We derive the low-energy effective Lagrangian which turns out to involve two parameters: one measuring the nonminimal coupling of fermions in the presence of torsion, the other being the Immirzi parameter. In the case of nonminimal coupling the effective Lagrangian contains an axial-vector interaction leading to parity violation. Alternatively, in the case of minimal coupling there is no parity violation and the effective Lagrangian contains only the usual axial-axial interaction. In this situation the real values of the Immirzi parameter are not at all constrained. On the other hand, purely imaginary values of the Immirzi parameter lead to violations of unitarity for the case of nonminimal coupling. Finally, the effective Lagrangian blows up for the positive and negative unit imaginary values of the Immirzi parameter.

We compute the one loop self-mass of a charged massless, minimally coupled scalar in a locally de Sitter background geometry. The computation is done in two different gauges: the noninvariant generalization of Feynman gauge which gives the simplest expression for the photon propagator and the de Sitter invariant gauge of Allen and Jacobson. In each case dimensional regularization is employed and fully renormalized results are obtained. The result in the de Sitter invariant gauge exhibits an on-shell singularity which we show can be eliminated if the equation for the photon propagator is changed to include an antisource at the antipodal point. By using our result in the linearized, effective field equations one can infer how the scalar responds to the dielectric medium produced by inflationary particle production. We also work out the result for a conformally coupled scalar. Although the conformally coupled case is of no great physical interest the fact that we obtain a manifestly de Sitter invariant form for its self-mass-squared establishes that our noninvariant gauge introduces no physical breaking of de Sitter invariance at one loop order.

In models with universal extra dimensions, the isosinglet Kaluza-Klein (KK) quarks ($q^1$) have very narrow widths, of $O(5–10)\mathrm{MeV}$, and will thus hadronize. Studies of KK quarkonia (${\overline{q}}^1{q}^1$) show very sharp resonances and dramatic signatures at the linear collider. In this Brief Report, we consider the possibility of detecting KK mesons, $({\overline{q}}^{1}q)$, and show that detection at a linear collider is unlikely.

By referring to the underlying physics behind the color charge neutrality condition in quark matter, we discuss how this condition should be properly imposed in Nambu-Jona-Lasinio (NJL)-type models in a phenomenologically meaningful way. In particular, we show that the standard assumption regarding the use of two color chemical potentials, chosen in a very special way, is not justified in general. When used uncritically, such an approach leads to wrong or unphysical conclusions.

In the scaling regime, amplitudes for backward virtual Compton scattering and hadron annihilation into two photons depend on structure functions that describe the hadron-photon transition at the partonic level. We construct simple analytical models for the vector and axial-vector pion-photon transition distribution amplitudes based on double distributions. Via a sum rule, these models are tuned to reproduce the pion-photon transition form factors. To obtain reasonable estimates of the distributions at a low scale, we modify the models to saturate the positivity bounds using empirically parametrized parton distributions. We also determine a model-independent contribution to the axial-vector transition distribution using chiral perturbation theory.

We consider two polarization asymmetries in the process of top-antitop production at LHC. We show that the theoretical predictions for these two quantities, at the strong and electroweak partonic one-loop level, are free of QCD and QED effects. At this perturbative level we derive two sum rules, that relate measurable quantities of top-antitop production to genuinely weak inputs. This would allow to perform two independent tests of the candidate theoretical model, with a precision that will be fixed by the future experimental accuracies of the different polarization measurements. A tentative quantitative illustration of this statement for a specific minimal supersymmetric standard model (MSSM) scenario is enclosed, and a generalization to include two other future realistic measurements is also proposed.

We give predictions for the neutrinoless double beta decay rate in a simple variant of the $A_4$ family symmetry model. We show that there is a lower bound for the $\beta {\beta }_{0\nu }$ amplitude even in the case of normal hierarchical neutrino masses, corresponding to an effective mass parameter $|m_{ee}|\ge 0.17\sqrt{\Delta m_{\mathrm{ATM}}^2}$. This result holds both for the $CP$ conserving and $CP$ violating cases. In the latter case we show explicitly that the lower bound on $|m_{ee}|$ is sensitive to the value of the Majorana phase. We conclude therefore that in our scheme, $\beta {\beta }_{0\nu }$ may be accessible to the next generation of high sensitivity experiments.

In a recent article, W.-S. Hou and G.-G. Wong [Phys. Rev. D 67, 034 003 (2003)] have investigated the spectrum of two-gluon glueballs below 3 GeV in a potential model with a dynamical gluon mass. We point out that, among the 18 states calculated by the authors, only three are physical. The other states either are spurious or possess a finite mass only due to an arbitrary restriction of the variational parameter.

We investigate SU(2) gauge fields topology using new approach, which exploits the well known connection between SU(2) gauge theory and quaternionic projective $\sigma$-models and allows to formulate the topological charge density entirely in terms of $\sigma$-model fields. The method is studied in details and for thermalized vacuum configurations is shown to be compatible with overlap-based definition. We confirm that the topological charge is distributed in localized four-dimensional regions which, however, are not compatible with instantons. Topological density bulk distribution is investigated at different lattice spacings and is shown to possess some universal properties.

We study various channels of top and Higgs flavor changing neutral couplings in the two Higgs doublet model with natural flavor conservation (2HDM-I and 2HDM-II). We update known results about $t\to c\gamma ,cZ,cg$ and comment on $t\to c{h}^0$. The decays $t\to c{h}^0$ as well as $\{h^0,H^0\}\to \overline{t}c$ are sensitive both to the bottom Yukawa coupling as well as to the trilinear scalar couplings $h^0{H}^{+}{H}^{-}$ and $H^0{H}^{+}{H}^{-}$. After imposing unitarity constraints as well as vacuum stability conditions on scalar sector parameters, in 2HDM-II we found that for large $\tan \beta \gtrsim 40$ and rather light charged Higgs mass $M_{H\pm }\gtrsim 150\mathrm{GeV}$, the maximum values allowed for $\mathrm{Br}(t\to c{h}^0)$, $\mathrm{Br}(H^0\to \overline{t}c)$, and $\mathrm{Br}(h^0\to \overline{t}c)$ are: $8\times {10}^{-5}$, ${10}^{-3}$, and ${10}^{-4}$ respectively. For charged Higgs mass in the range $[200,300]\mathrm{GeV}$, which can accommodate $B\to X_s\gamma$ constraint if one takes into account large theoretical uncertainties, the branching ratio of both $H^0\to \overline{t}c$ and $h^0\to \overline{t}c$ can still be slightly larger than ${10}^{-5}$. For $A^0\to \overline{t}c$, its branching ratio is smaller than $\approx {10}^{-7}$ in both 2HDM-I and 2HDM-II. We study also the top-charm associated production at $e^{+}{e}^{-}$ colliders and its $\gamma \gamma$ option as well as at muon colliders. It is found that the cross section of $\gamma \gamma \to \overline{t}c$ can be of the order $0.01\to 0.1\mathrm{fb}$ near threshold region, while the cross section of $e^{+}{e}^{-}\to \overline{t}c$ is well below ${10}^{-2}\mathrm{fb}$. The situation is slightly better for muon colliders where a few fb cross section can be reached for large $\tan \beta$ and low center-of-mass energy $\sqrt{s}\lesssim 500\mathrm{GeV}$.

At high energies, the relevant degrees of freedom are Wilson lines—infinite gauge links ordered along straight lines collinear to the velocities of colliding particles. The effective action for these Wilson lines is determined by the scattering of QCD shock waves. I develop the symmetric expansion of the effective action in powers of strength of one of the shock waves and calculate the leading term of the series. The corresponding first-order effective action, symmetric with respect to projectile and target, includes both up and down fan diagrams and pomeron loops.