We find the most general supergravity solution in an $Ad{S}^3\times S^3$ background preserving an $Ad{S}_2\times S^2$ symmetry and half the supersymmetries. Contrary to previous expectations from boundary state arguments, it is shown that no solutions exist containing localized brane sources.

The mass of a scalar field mediating a fifth force is tightly constrained by experiments. We show, however, that adding a quartic self-interaction for such a scalar makes most tests much less constraining: the nonlinear equation of motion masks the coupling of the scalar to matter through the chameleon mechanism. We discuss consequences for fifth force experiments. In particular, we find that, with quartic coupling of order unity, a gravitational strength interaction with matter is allowed by current constraints. We show that our chameleon scalar field results in experimental signatures that could be detected through modest improvements of current laboratory set-ups.

We present a new calculation of the first Gegenbauer moment $a_1^K$ of the kaon light cone distribution amplitude. This moment is determined by the difference between the average momenta of strange and nonstrange valence quarks in the kaon. To calculate $a_1^K$, QCD sum rule for the diagonal correlation function of local and nonlocal axial-vector currents is used. Contributions of condensates up to dimension six are taken into account, including $O({\alpha }_s)$-corrections to the quark-condensate term. We obtain $a_1^K=0.05\pm 0.02$, differing by the sign and magnitude from the recent sum rule estimate from the nondiagonal correlation function of pseudoscalar and axial-vector currents. We argue that the nondiagonal sum rule is numerically not reliable. Furthermore, an independent indication for a positive $a_1^K$ is given, based on the matching of two different light cone sum rules for the $K\to \pi$ form factor. With the new interval of $a_1^K$, we update our previous numerical predictions for SU(3)-violating effects in $B_{(s)}\to K$ form factors and charmless $B$ decays.

The large decay rate observed by Belle for $B^{+}\to \psi (3770)K^{+}$, which is comparable to $B^{+}\to \psi (3686)K^{+}$, might indicate either an unexpectedly large S-D mixing angle $|\theta |\approx {40}^{°}$ or the leading role of the color-octet mechanism in D-wave charmonium production in $B$ decay. By calculating the production rate of $\psi (3770)$ in the continuum $e^{+}{e}^{-}$ annihilation at $\sqrt{s}=10.6\mathrm{G}\mathrm{e}\mathrm{V}$ with these two possible approaches (i.e., the large S-D mixing and the color-octet mechanism), we show that the measurement for this process at Belle and BABAR may provide a clear cut clarification for the two approaches. In addition, the radiative E1 transition ratio $\Gamma [\psi (3770)\to \gamma {\chi }_{c2}]/\Gamma [\psi (3770)\to \gamma {\chi }_{c1}]$ may dramatically change from $\sim$ 0.04 (for $\theta \approx 0^{°}$) to $\sim 200$ (for $\theta \approx -{40}^{°}$) due to the large S-D interference effect, thus the E1 transition measurement of $\psi (3770)$ at Beijing Spectrometer and CLEO-c will also be very useful in clarifying this issue.

We consider hadronic $CP$ violation induced by chromoelectric dipole moments (CEDMs) of light quarks and the QCD theta parameter ($\overline{\theta }$). We concentrate on the strange quark CEDM especially in this paper. Using effective $CP$ violating nucleon interactions induced by the CEDMs and $\overline{\theta }$ with the SU(3) chiral Lagrangian technique, we calculate the EDMs for the ${}^{199}\mathrm{H}\mathrm{g}$ atom, neutron, and deuteron. We also discuss supersymmetric (SUSY) contributions to the electric dipole moments with the mass insertion approximations and give constraints on the $CP$ phases of the flavor changing SUSY breaking terms.

The admissibility condition usually used to define the topological charge in lattice gauge theory is incompatible with a positive transfer matrix.

Recent observations and theoretical considerations have motivated the study of models for dark energy with equation of state characterized by a parameter $w=p/\rho <-1$. Such models, however, are usually believed to be inviable due to their instabilities against classical perturbations or potentially catastrophic vacuum decays. In this Brief Report, we show that a simple quintessential model with potential $V(\varphi )=A{e}^{-\sigma \varphi }$ and a gravitational coupling of the form $(1+|\xi |{\varphi }^2)R$ can exhibit, for large sets of initial conditions, asymptotic de Sitter behavior with $w<-1$ regimes. Nevertheless, the model is indeed stable at classical and quantum level.

The five dimensional version of the Green-Schwarz mechanism can be invoked to cancel U(1) anomalies on the boundaries of brane world models. In five dimensions there are two dual descriptions that employ either a two-form tensor field or a vector field. We present the supersymmetric extensions of these dual theories using four dimensional $N=1$ superspace. For the supersymmetrization of the five dimensional Chern-Simons three-form this requires the introduction of a new chiral Chern-Simons multiplet. We derive the supersymmetric vector/tensor duality relations and show that not only is the usual one-/two-form duality modified, but that there is also an interesting duality relation between the scalar components. Furthermore, the vector formulation always contains singular boundary mass terms which are absent in the tensor formulation. This apparent inconsistency is resolved by showing that in either formulation the four dimensional anomalous U(1) mass spectrum is identical, with the lowest lying Kaluza-Klein mode generically obtaining a finite nonzero mass.

Analytical approximations for $⟨{\phi }^2⟩$ of a quantized scalar field in ultrastatic asymptotically flat spacetimes are obtained. The field is assumed to be both massive and massless, with an arbitrary coupling $\xi$ to the scalar curvature, and in a zero or nonzero temperature vacuum state. The expression for $⟨{\phi }^2⟩$ is divided into low- and high-frequency parts. The expansion for the high-frequency contribution to this quantity is obtained. This expansion is analogous to the DeWitt-Schwinger one. As an example, the low-frequency contribution to $⟨{\phi }^2⟩$ is calculated on the background of the small perturbed flat spacetime in a quantum state corresponding to the Minkowski vacuum at the asymptotic. The limits of the applicability of these approximations are discussed.

Both scalar and Dirac quasinormal modes in Garfinkle-Horowitz-Strominger black hole spacetime are studied by using the WKB approximation and the Pöschl-Teller approximation. For scalar field, we find that the quasinormal modes (QNMs) with higher dilatons decay more rapidly than that with lower ones. However, this is not the case for mass $m$. Fields with higher mass will decay more slowly. Similar behaviors appear in the case of Dirac field. We also find that QNM frequencies evaluated by using WKB approximation and Pöschl-Teller approximation have good agreement with each other when mode number $n$ is small.

The Integrated Sachs-Wolfe (ISW) effect is a direct signature of the presence of dark energy in the universe, in the absence of spatial curvature. A powerful method for observing the ISW effect is through cross-correlation of the cosmic microwave background with a tracer of the matter in the low redshift universe. In this paper, we describe the dependence of the obtained cross-correlation signal on the geometry and other properties of a survey of the low redshift universe. We show that an all-sky survey with about $10\times {10}^6$ galaxies, almost uniformly distributed within $0<z<1$ should yield a near optimal ISW detection, at $\sim 5\sigma$ level. In order to achieve this level of signal-to-noise, the systematic anisotropies in the survey must be below $\sim 0.1\%$, on the scale of $\sim 10°$ on the sky, while the systematic error in redshift estimates must be less than 0.05. Then, we argue that, while an ISW detection will not be a good way of constraining the conventional properties of dark energy, it could be a valuable means of testing alternative theories of gravity on large physical scales.

In supersymmetric extensions of the particle physics standard model, gauge invariant combinations of squarks and sleptons (flat directions) can acquire large expectation values during a period of cosmological inflation. If the inflaton sector couples to matter fields via these flat directions, then new channels for efficient reheating, in particular, via parametric resonance instabilities, are opened up. These can lead to efficient reheating induced by the flat directions even if the bare coupling constants are small. In this Letter we discuss various channels which yield this “enhanced reheating” effect, and we address some cosmological consequences.

Cosmic strings arising from breaking of the $\mathrm{U}(1{)}_{B-L}$ gauge symmetry that occurs in a wide variety of unified models can carry zero modes of heavy Majorana neutrinos. Decaying and/or repeatedly self-interacting closed loops of these “$B-L$” cosmic strings can be a nonthermal source of heavy right-handed Majorana neutrinos whose decay can contribute to the observed baryon asymmetry of the Universe (BAU) via the leptogenesis route. The $B-L$ cosmic strings are expected in grand unified theory (GUT) models such as SO(10), where they can be formed at an intermediate stage of symmetry breaking well below the GUT scale $\sim {10}^{16}\mathrm{G}\mathrm{e}\mathrm{V}$; such light strings are not excluded by the cosmic microwave background (CMB) anisotropy data and may well exist. We estimate the contribution of $B-L$ cosmic string loops to the baryon-to-photon ratio of the Universe in the light of current knowledge on neutrino masses and mixings implied by atmospheric and solar neutrino measurements. We find that $B-L$ cosmic string loops can contribute significantly to the BAU for $\mathrm{U}(1{)}_{B-L}$ symmetry-breaking scale ${\eta }_{B-L}\gtrsim 1.7\times {10}^{11}\mathrm{G}\mathrm{e}\mathrm{V}$. At the same time, in order for the contribution of decaying $B-L$ cosmic string loops not to exceed the observed baryon-to-photon ratio inferred from the recent Wilkinson microwave anisotropy probe (WMAP) results, the lightest heavy right-handed Majorana neutrino mass $M_1$ must satisfy the constraint $M_1\le 2.4\times {10}^{12}({\eta }_{B-L}/{10}^{13}\mathrm{G}\mathrm{e}\mathrm{V}{)}^{1/2}\mathrm{G}\mathrm{e}\mathrm{V}$. This may have interesting implications for the associated Yukawa couplings in the heavy neutrino sector and consequently for the light neutrino masses generated through seesaw mechanism.

We analyze the decay laws of the kinetic and magnetic energies and the evolution of correlation lengths in freely decaying incompressible magnetohydrodynamic (MHD) turbulence. Scale invariance of MHD equations assures that, in the case of constant dissipation parameters (i.e., kinematic viscosity and resistivity) and null magnetic helicity, the kinetic and magnetic energies decay in time as $E\sim t^{-1}$, and the correlation lengths evolve as $\xi \sim t^{1/2}$. In the helical case, assuming that the magnetic field evolves towards a force-free state, we show that (in the limit of large magnetic Reynolds number) the magnetic helicity remains constant, and the kinetic and magnetic energies decay as $E_v\sim t^{-1}$ and $E_B\sim t^{-1/2}$ respectively, while both the kinetic and magnetic correlation lengths grow as $\xi \sim t^{1/2}$.

Extensions of the Standard Model of elementary particle physics to noncommutative geometries have been proposed as a low-energy limit of string models. Independent of this motivation, one may consider such a model as an effective field theory with higher-dimensional operators containing an antisymmetric rank-two background field. We study the signals of such a Noncommutative Standard Model (NCSM) and analyze the discovery potential of a future photon collider, considering angular distributions in fermion pair production.

A minimal SO(10) model with 126 Higgs field breaking $B-L$ symmetry has been shown recently to predict large solar and atmospheric mixings in agreement with observations if it is assumed that the neutrino mass follows from the triplet dominated type-II seesaw formula. No additional symmetries need to be assumed for this purpose. We discuss the conditions on the way SO(10) symmetry breaks down to the minimal supersymmetric standard model (MSSM) and the Higgs multiplets in the model, required for the triplet dominated type-II seesaw formula to hold. We find that (i) SO(10) must break to a nonminimal SU(5) before breaking to the standard model; (ii) $B-L$ symmetry must break at the time of SO(10) breaking and (iii) constraints of unification seem to require that the minimal model must have a 54 dimensional Higgs field together with a 210 and 126 to break the grand unified theory (GUT) symmetry.

Lattice Landau gauge and other related lattice gauge-fixing schemes are known to violate spectral positivity. The most direct sign of the violation is the rise of the effective mass as a function of distance. The origin of this phenomenon lies in the quenched character of the auxiliary field $g$ used to implement lattice gauge-fixing, and is similar to quenched QCD in this respect. This is best studied using the Parrinello Jona-Lasinio Zwanziger formalism, leading to a class of covariant gauges similar to the one-parameter class of covariant gauges commonly used in continuum gauge theories. Soluble models are used to illustrate the origin of the violation of spectral positivity. The phase diagram of the lattice theory, as a function of the gauge coupling $\beta$ and the gauge-fixing parameter $\alpha$, is similar to that of the unquenched theory, a Higgs model of a type first studied by Fradkin and Shenker. The gluon propagator is interpreted as yielding bound states in the confined phase, and a mixture of fundamental particles in the Higgs phase, but lattice simulation shows the two phases are connected. Gauge-field propagators from the simulation of an SU(2) lattice gauge theory on a ${20}^4$ lattice are well described by a quenched mass-mixing model. The mass of the lightest state, which we interpret as the gluon mass, appears to be independent of $\alpha$ for sufficiently large $\alpha$.

We present a lattice QCD calculation of phase shift including the chiral and continuum extrapolations in two-flavor QCD. The calculation is carried out for $I=2$ $S$-wave $\pi \pi$ scattering. The phase shift is evaluated for two momentum systems, the center of mass and laboratory systems, by using the finite-volume method proposed by Lüscher in the center of mass system and its extension to general systems by Rummukainen and Gottlieb. The measurements are made at three different bare couplings $\beta =1.80$, 1.95 and 2.10 using a renormalization group improved gauge and a tadpole improved clover fermion action, and employing a set of configurations generated for hadron spectroscopy in our previous work. The illustrative values we obtain for the phase shift in the continuum limit are $\delta (\mathrm{deg}.)=-3.50(64)$, $-9.5(30)$ and $-16.9(64)$ for $\sqrt{s}(\mathrm{G}\mathrm{e}\mathrm{V})=0.4$, 0.6 and 0.8, which are consistent with experiments.

We study the effect of representation mixing in the $\mathrm{S}\mathrm{U}(3)$ Skyrme model by diagonalizing exactly the representation-dependent part. It is observed that even without the next-to-leading-order symmetry breaking terms the low-lying baryon masses as well as the recently discovered ${\Theta }^{+}$ and ${\Xi }_{\overline{10}}$ can be fairly well reproduced within 3% accuracy. It is also demonstrated that the mixing effect is not negligible in decay processes of $\{\overline{10}\}$. In particular the effect of mixing with $\{27\}$ is found to be quite large. These results are compatible with the second-order perturbation scheme. The decay widths are found to be sensitive to the mass values. The decay widths of $\{\overline{10}\}$ are estimated to be smaller than those of $\{10\}$ by an order of magnitude due to the destructive interference between operators, although the kinematic factors are comparable.

To establish the Higgs mechanism experimentally, one has to determine the Higgs self-interaction potential responsible for the electroweak symmetry breaking. This requires a measurement of the trilinear and quadrilinear self-couplings of the Higgs particle, as predicted by the standard model. We propose that the trilinear Higgs self-coupling be measured in the process $\gamma \gamma \to \mathrm{H}\mathrm{H}$ just above the kinematic threshold of $2{\mathrm{M}}_{\mathrm{H}}$, where ${\mathrm{M}}_{\mathrm{H}}$ is the Higgs mass. Our calculation shows that the statistical sensitivity of the cross section ${\sigma }_{\gamma \gamma \to \mathrm{H}\mathrm{H}}$ to the Higgs self-coupling is maximal near the $2{\mathrm{M}}_{\mathrm{H}}$ threshold for ${\mathrm{M}}_{\mathrm{H}}$ between 115 and 150 GeV, and is larger than the statistical sensitivities of ${\sigma }_{e^{+}{e}^{-}\to \mathrm{Z}\mathrm{H}\mathrm{H}}$ and ${\sigma }_{e^{+}{e}^{-}\to \nu \overline{\nu }\mathrm{H}\mathrm{H}}$ to this coupling for $2{\mathrm{E}}_e\le 700\mathrm{G}\mathrm{e}\mathrm{V}$.