The soft pion correction at high energy may play a crucial role in nonperturbative parts of sea quark distributions. In this paper, we show that, while the soft pion correction for the strange sea quark distribution is suppressed in the large and the medium x region compared with that for the up and the down sea quark one, it can become large and $\mathrm{SU}\mathrm{}\left(3\right)\mathrm{}$ flavor symmetric in the very small x region. This gives us a good reason for the symmetry restoration of light sea quark distributions required by the mean charge sum rule for the light sea quarks. Then, by estimating this sum rule with the help of the results obtained by the soft pion correction, it is argued that there is a large symmetry restoration of the strange sea quark in the region from ${x=10\mathrm{}}^{-2}$ to ${10}^{-6}$ at $Q^2\sim 1\mathrm{GeV}.$

In a recently suggested method for measuring the weak phase $\gamma$ in $B^{\pm }\to K^{\pm }{(KK}^{*}{)}_D$ decays, the relative strong phase ${\delta }_D$ in $D^0\to K^{*+}{K}^{-}$ and $D^0\to K^{*-}{K}^{+}$ decays (equivalently, in $D^0\to K^{*+}{K}^{-}$ and $D^0\to K^{*+}{K}^{-})$ plays a role. It is shown how a study of the Dalitz plot in $D^0\to K^{+}{K}^{-}{\pi }^0$ can yield information on this phase, and the size of the data sample which would give a useful measurement is estimated.

We demonstrate how Sen’s singular kink solution of the Born-Infeld tachyon action can be constructed by taking the appropriate limit of initially regular profiles. It is shown that the order in which different limits are taken plays an important role in determining whether or not such a solution is obtained for a wide class of potentials. Indeed, by introducing a small parameter into the action, we are able circumvent the results of a recent paper which derived two conditions on the asymptotic tachyon potential such that the singular kink could be recovered in the large amplitude limit of periodic solutions. We show that this is explained by the non-commuting nature of two limits, and that Sen’s solution is recovered if the order of the limits is chosen appropriately.

We continue the development of a systematic procedure for deriving closed string pp wave string field theory (SFT) from the large N Berenstein-Maldacena-Nastase (BMN) limit. In the present paper the effects of the Yang-Mills interaction are considered in detail for general BMN states. The SFT interaction with the appropriate operator insertion at the interaction point is demonstrated.

We show that puncture data for quasicircular binary black hole orbits allow a special gauge choice that realizes some of the necessary conditions for the existence of an approximate helical Killing vector field. Introducing free parameters for the lapse at the punctures we can satisfy the condition that the Komar and Arnowitt-Deser-Misner mass agree at spatial infinity. Several other conditions for an approximate Killing vector are then automatically satisfied, and the 3-metric evolves on a time scale smaller than the orbital time scale. The time derivative of the extrinsic curvature, however, remains significant. Nevertheless, quasicircular puncture data are not as far from possessing a helical Killing vector as one might have expected.

We derive an expression for the quasinormal modes of scalar perturbations in near extreme d-dimensional Schwarzschild–de Sitter and Reissner–Nordström–de Sitter black holes. We show that, in the near extreme limit, the dynamics of the scalar field is characterized by a Pöschl-Teller effective potential. The results are qualitatively independent of the spacetime dimension and field mass.

Cold dark matter may be made of superweakly interacting massive particles, super-WIMP’s, that naturally inherit the desired relic density from late decays of metastable WIMP’s. Well-motivated examples are weak-scale gravitinos in supergravity and Kaluza-Klein gravitons from extra dimensions. These particles are impossible to detect in all dark matter experiments. We find, however, that super-WIMP dark matter may be discovered through cosmological signatures from the early Universe. In particular, super-WIMP dark matter has observable consequences for big bang nucleosynthesis and the cosmic microwave background (CMB), and may explain the observed underabundance of ${}^7\mathrm{Li}$ without upsetting the concordance between deuterium and CMB baryometers. We discuss the implications for future probes of CMB blackbody distortions and collider searches for new particles. In the course of this study, we also present a model-independent analysis of entropy production from late-decaying particles in light of Wilkinson microwave anisotropy probe data.

We show that entropy perturbations can eliminate instabilities and oscillations in the mass power spectrum of the quartessence Chaplygin models. Our results enlarge the current parameter space of models compatible with large-scale structure and cosmic microwave background observations.

The neutral Higgs sector of the minimal supersymmetric standard model in an explicit $\mathrm{CP}$ violation scenario is investigated at the one-loop level. Within the context of the effective potential formalism, the masses of the neutral Higgs bosons are calculated at the one-loop level by taking into account the contributions of the following loops of ordinary particles and superpartners: the top quark, the scalar top quarks, the bottom quark, the scalar bottom quarks, the tau lepton, the scalar tau leptons, the W boson, the charged Higgs boson, the charginos, the Z boson, the scalar and pseudoscalar Higgs bosons, and the neutralinos. Our calculation is an improvement in the sense that both the terms which are quartic in the electroweak coupling constants are taken into account, and the pseudoscalar Higgs loop contribution is explicitly included.

We derive the Abelian-like expression for the lattice $\mathrm{SU}\mathrm{}\left(N\right)\mathrm{}$ Wilson loop in an arbitrary irreducible representation. The continuum Abelian representation of the $\mathrm{SU}\mathrm{}\left(N\right)\mathrm{}$ Wilson loop (for the loop without self-intersections) that has been obtained by Diakonov and Petrov appears to be a continuum limit of this expression. We also obtain the lattice variant of a non-Abelian Stokes theorem and present the explicit expression for the matrix $\mathcal{H}$ used in the Diakonov-Petrov approach.

We note that the phenomenon of perturbative saturation leads to transverse momentum broadening in the spectrum of partons produced in hadronic collisions. This broadening has a simple interpretation as the parton level Cronin effect for systems in which saturation is generated by the “tree level” Glauber-Mueller mechanism. For systems where the broadening results form the nonlinear QCD evolution to high energy, the presence or absence of the Cronin effect depends crucially on the quantitative behavior of the gluon distribution functions at transverse momenta $k_t$ outside the so called scaling window. We discuss the relation of this phenomenon to the recent analysis by Kharzeev, Levin, and McLerran of the momentum and centrality dependence of particle production in nucleus-nucleus collisions at BNL RHIC.

We calculate inclusive photoproduction cross sections for both proton and nuclei targets, using a saturation model derived from an approximate solution to the Balitsky-Kovchegov nonlinear evolution equation. This paper extends our hypothesis that one can successfully use the dipole picture and saturation models to describe soft processes, instead of the soft Pomeron Regge parametrization. Our fit is compatible with our previous fit to deep inelastic scattering data, and utilizes the same phenomenological parameters as in our paper devoted to soft hadronic interactions. Using the Glauber formalism and no additional parameters, we calculate the cross sections for photoproduction on various nuclei, and compare our results with the relevant data.

Recent studies have shown that (a) quantum effects may be sufficient to support a wormhole throat and (b) the total amount of “exotic matter” can be made arbitrarily small. Unfortunately, using only small amounts of exotic matter may result in a wormhole that flares out too slowly to be traversable in a reasonable length of time. Combined with the Ford-Roman constraints, the wormhole may also come close to having an event horizon at the throat. This Brief Report examines a model that overcomes these difficulties, while satisfying the usual traversability conditions. This model also confirms that the total amount of exotic matter can indeed be made arbitrarily small.

The construction of dual theories for linearized gravity in four dimensions is considered. Our approach is based on the parent Lagrangian method previously developed for the massive spin-two case, but now considered for the zero mass case. This leads to a dual theory described in terms of a rank two symmetric tensor, analogous to the usual gravitational field, and an auxiliary antisymmetric field. This theory has an enlarged gauge symmetry, but with an adequate partial gauge fixing it can be reduced to a gauge symmetry similar to the standard one of linearized gravitation. We present examples illustrating the general procedure and the physical interpretation of the dual fields. The zero mass case of the massive theory dual to the massive spin-two theory is also examined, but we show that it only contains a spin-zero excitation.

We apply Kleinert’s variational method to field theory and calculate the effective potential of the $\lambda {\phi }^4$ theory in $4-\epsilon$ dimensions. The potential is regularized in the standard way using dimensional regularization, but we use a nonconventional renormalization scheme to subtract the divergences. This scheme emerges in a natural way when one tries to renormalize the potential before calculating the optimum value of the variational parameter. In order to do this we also have to renormalize the variational parameter. We have demonstrated that this alternative renormalization scheme eliminates the divergences to all orders in the cumulant expansion of the effective potential. We have also tested its compatibility with critical phenomena by calculating critical exponents and the equation of state to order $\epsilon .$ We have shown how to obtain an exact implicit form of the equation of state, which can be solved after performing an $\epsilon$ expansion. The equation of state and the critical exponents coincide to order $\epsilon$ with the usual ones calculated through the loop expansion. The renormalization scheme proposed is also applied to the one-loop effective potential. Even though we obtain the same critical behavior in $4-\epsilon$ dimensions as in more conventional approaches, our renormalization scheme yields a $\beta$ function that goes to zero in the limit $\overrightarrow{\epsilon }0.$ This is an indication that variational techniques and the loop expansion, depending on the renormalization method employed, may be sensitive to the triviality of the $\lambda {\phi }^4$ theory in four dimensions.

Lower bounds on the magnitude of the spectrum of the Hermitian Wilson-Dirac operator $H\left(m\right)\mathrm{}$ have previously been derived for $0<m<\mathrm{}2\mathrm{}$ when the lattice gauge field satisfies a certain smoothness condition. In this paper lower bounds are derived for $2p-2<m<\mathrm{}2p$ for general $p=1,2,\dots ,d$ where d is the spacetime dimension. The bounds can alternatively be viewed as localization bounds on the real spectrum of the usual Wilson-Dirac operator. They are needed for the rigorous evaluation of the classical continuum limit of the axial anomaly and the index of the overlap Dirac operator at general values of m, and provide information on the topological phase structure of overlap fermions. They are also useful for understanding the instanton size dependence of the real spectrum of the Wilson-Dirac operator in an instanton background.

Four-dimensional cylindrically symmetric spacetimes with homothetic self-similarity are studied in the context of Einstein’s theory of gravity, and a class of exact solutions to the Einstein-massless scalar field equations is found. Their local and global properties are investigated and it is found that they represent gravitational collapse of a massless scalar field. In some cases the collapse forms black holes with cylindrical symmetry, while in the other cases it does not. The linear perturbations of these solutions are also studied and given in closed form. From the spectra of the unstable eigenmodes, it is found that there exists one solution that has precisely one unstable mode, which may represent a critical solution, sitting on a boundary that separates two different basins of attraction in the phase space.

We study the distribution of dark matter versus visible matter using a set of data obtained from strong gravitational lensing in the galaxy cluster $\mathrm{CL}0024+1654$ and another set of data inferred from the universal rotation curves in spiral galaxies. The important feature of these two dramatically different observations is that the mass density profile of both visible and dark components can be estimated. From these measurements we deduce the mass of the dark matter particle and our estimate of the mass for the dark matter particle is ${\mu }_d\approx 200–700\mathrm{MeV}.$ We contrast our estimates from $\mathrm{CL}0024+1654$ data and the universal rotation curves of the spiral galaxies and discuss their consistency.

We examine observational constraints on chaotic inflation models in the Randall-Sundrum type II braneworld. If inflation takes place in the high-energy regime, the perturbations produced by the quadratic potential are further from scale invariance than in the standard cosmology, in the quartic case more or less unchanged, while for potentials of greater exponent the trend is reversed. We test these predictions against a data compilation including the Wilkinson Microwave Anisotropy Probe measurements of microwave anisotropies and the two degree field galaxy power spectrum. While in the standard cosmology the quartic potential is at the border of what the data allow and all higher powers excluded, we find that in the high-energy regime of braneworld inflation even the quadratic case is under strong observational pressure. We also investigate the intermediate regime where the brane tension is comparable to the inflationary energy scale, where the deviations from scale invariance prove to be greater.

Generalizations of the Randall-Sundrum model containing a bulk scalar field $\Phi$ interacting with the curvature R through the general coupling $Rf\left(\Phi \right)$ are considered. We derive the general form of the effective 4D potential for the spin-zero fields and show that in the mass matrix the radion mixes with the Kaluza-Klein (KK) modes of the bulk scalar fluctuations. We demonstrate that it is possible to choose a nontrivial background form ${\Phi }_0\mathrm{}\left(y\right)\mathrm{}$ (where y is the extra dimension coordinate) for the bulk scalar field such that the exact Randall-Sundrum metric is preserved (i.e. such that there is no back reaction). We compute the mass matrix for the radion and the KK modes of the excitations of the bulk scalar relative to the background configuration ${\Phi }_0\mathrm{}\left(y\right).$ We find that for any (consistent) ${\Phi }_0\mathrm{}\left(y\right)\mathrm{}$ the expected mass for the radionlike eigenstate is suppressed relative to the Planck scale by the standard warp factor needed to explain the hierarchy puzzle, implying that $\sim 1\mathrm{TeV}$ is a natural order of magnitude for this mass. The general considerations are illustrated in the case of a model containing an $R{\Phi }^2$ interaction term.