We use the Type Ia Supernova gold sample data of Riess et al in order to constrain three models of dark energy. We study the Cardassian model, the Dvali-Turner gravity modified model, and the generalized Chaplygin gas model of dark energy–dark matter unification. In our best-fit analysis for these three dark energy proposals we consider the flat model and the nonflat model priors. We also discuss the degeneracy of the models with the XCDM model through the computation of the so-called jerk parameter.

We show that current surveys have at least as much signal to noise in higher-order statistics as in the power spectrum at weakly nonlinear scales. We discuss how one can use this information to determine the mean of the galaxy halo-occupation distribution (HOD) using only large-scale information, through galaxy bias parameters determined from the galaxy bispectrum and trispectrum. After introducing an averaged, reasonably fast to evaluate, trispectrum estimator, we show that the expected errors on linear and quadratic bias parameters can be reduced by at least 20%–40%. Also, the inclusion of the trispectrum information, which is sensitive to “three-dimensionality” of structures, helps significantly in constraining the mass dependence of the HOD mean. Our approach depends only on adequate modeling of the abundance and large-scale clustering of halos and thus is independent of details of how galaxies are distributed within halos. This provides a consistency check on the traditional approach of using two-point statistics down to small scales, which necessarily makes more assumptions. We present a detailed forecast of how well our approach can be carried out in the case of the Sloan Digital Sky Survey (SDSS).

Recently BABAR and Belle Collaborations have measured direct $CP$ asymmetry $A_{CP}=-0.114\pm 0.020$ in ${\overline{B}}^0\to K^{-}{\pi }^{+}$. The experimental value is substantially different from the QCD factorization prediction. We show that supersymmetry flavor changing neutral current interaction via gluonic dipole can explain the difference. $CP$ asymmetries in other $B\to K\pi$ decays are predicted to be sizable. Taking this asymmetry as a constraint, we find that the allowed supersymmetry parameter space is considerably reduced compared with constraint from $B\to X_s\gamma$ alone. We also find the allowed time-dependent $CP$ asymmetries $S_f$ in ${\overline{B}}^0\to {\overline{K}}^{*0}\gamma \to {\pi }^0{K}_S\gamma$ and ${\overline{B}}^0\to \varphi K_S$ to be large. These predictions are quite different than those predicted in the standard model and can be tested in the near future.

We calculate the cross section for diffractive photoproduction of opposite-charge pseudoscalar meson pairs $M^{+}{M}^{-}={\pi }^{+}{\pi }^{-}$, $K^{+}{K}^{-}$, $D^{+}{D}^{-}$, and $B^{+}{B}^{-}$ in a broad range of center of mass energies relevant for GlueX/Hall D, FOCUS, COMPASS, and HERA experiments. In the case of ${\pi }^{+}{\pi }^{-}$ production we find that the interference of the ${\rho }^0$ resonance and the two-pion continuum leads to a considerable deformation of the shape of ${\rho }^0$ in agreement with the data from the ZEUS Collaboration. We also discuss the spectral shape of the ${\rho }^0$ as a function of the momentum transfer and the contribution of higher partial waves to the ${\pi }^{+}{\pi }^{-}$ mass spectrum. We predict a sizeable energy-dependent forward-backward asymmetry in the Gottfried-Jackson frame. For the heavy meson production we find that the cross section for diffractive production increases much slower than the one for open charm or bottom production. We estimate the cross sections for diffractive production of $D^{+}{D}^{-}$ and $B^{+}{B}^{-}$ pairs.

We present technical aspects of next-to-next-to-leading order calculations for heavy-to-light decays such as top quark decay, semileptonic $b$ quark decay into a $u$ quark, muon decay, and radiative decays like $b\to s\gamma$. Algebraic reduction of integrals to a set of master integrals is described, methods of determining the master integrals are presented, and a complete list of master integrals is given. As a sample application, the top quark decay width is calculated to $\mathcal{O}({\alpha }_s^2)$ accuracy.

Thermal color superconducting phase transitions in three-flavor quark matter at high baryon density are investigated in the Ginzburg-Landau (GL) approach. We constructed the GL potential near the boundary with a normal phase by taking into account nonzero quark masses, electric charge neutrality, and color charge neutrality. We found that the density of states averaged over paired quarks plays a crucial role in determining the phases near the boundary. By performing a weak coupling calculation of the parameters characterizing the GL potential terms of second order in the pairing gap, we show that three successive second-order phase transitions take place as the temperature increases: a modified color-flavor locked phase ($ud$, $ds$, and $us$ pairings) $\to$ a dSC phase ($ud$ and $ds$ pairings) $\to$ an isoscalar pairing phase ($ud$ pairing) $\to$ a normal phase (no pairing). The Meissner masses of the gluons and the number of gapless quark modes are also studied analytically in each of these phases.

For the exploration of flavor physics, $b\to d$ penguin processes are an important aspect, with the prominent example of ${\overline{B}}_d^0\to K^0{\overline{K}}^0$. We recently derived lower bounds for the CP-averaged branching ratio of this channel in the standard model; they were found to be very close to the corresponding experimental upper limits, thereby suggesting that ${\overline{B}}_d^0\to K^0{\overline{K}}^0$ should soon be observed. In fact, the BABAR Collaboration subsequently announced the first signals of this transition. Here we point out that it is also possible to derive lower bounds for $\overline{B}\to \rho \gamma$ decays, which are again surprisingly close to the current experimental upper limits. We show that these bounds are realizations of a general bound that holds within the standard model for $b\to d$ penguin processes, allowing further applications to decays of the kind $B^{\pm }\to K^{(*)\pm }{K}^{(*)}$ and $B^{\pm }\to {\pi }^{\pm }{\ell }^{+}{\ell }^{-}$, ${\rho }^{\pm }{\ell }^{+}{\ell }^{-}$.

We consider a 5-dimensional scalar-tensor theory which is a direct generalization of the original 4-dimensional Brans-Dicke theory to five dimensions. By assuming that there is a hypersurface-orthogonal spacelike Killing vector field in the underlying 5-dimensional spacetime, the theory is reduced to a 4-dimensional theory where the 4-metric is coupled with two scalar fields. The cosmological implication of this reduced theory is then studied in the Robertson-Walker model. It turns out that the two scalar fields may account naturally for the present accelerated expansion of our universe. The observational restriction of the reduced cosmological model is also analyzed.

We present a scaling analysis in the 1-flavor Schwinger model with the full overlap and the rooted staggered determinant. In the latter case the chiral and continuum limit of the scalar condensate do not commute, while for overlap fermions they do. For the topological susceptibility a universal continuum limit is suggested, as is for the partition function and the Leutwyler-Smilga sum rule. In the heavy-quark force no difference is visible even at finite coupling. Finally, a direct comparison between the complete overlap and the rooted staggered determinant yields evidence that their ratio is constant up to $O(a^2)$ effects.

A nonzero $CP$-violating $\theta$ parameter is treated in the domain model which assumes a clusterlike vacuum structure whose units are characterized, in particular, by a topological charge which is not necessarily an integer number. In the present paper we restrict consideration to rational values of the charge. The model has previously been shown to manifest confinement, spontaneous chiral symmetry breaking and the absence of an axial $U(1)$ Goldstone boson. We find that the specific structure of the minima of the free energy density of the domain ensemble forces a $2\pi$ periodicity of observables in $\theta$ for any number of light quarks, that vacuum doubling occurs at $\theta =\pi$ for any $N_f>1$ and any value of topological charge $q$. These features are in agreement with expectations based on anomalous Ward identities and large $N_c$ effective theories. We find also additional values of $\theta$ depending on $q$ for which vacuum doubling occurs.

Spatially flat loitering universe models have recently been shown to arise in the context of brane world scenarios. Such models allow more time for structure formation to take place at high redshifts, easing, e.g., the tension between the observed and predicted evolution of the quasar population with redshift. While having the desirable effect of boosting the growth of structures, we show that in such models the position of the first peak in the power spectrum of the cosmic microwave background anisotropies severely constrain the amount of loitering at high redshifts.

Using the leading twist approach to nuclear shadowing, which is based on the relationship between nuclear shadowing and diffraction on a nucleon, we calculate next-to-leading order nuclear parton distribution functions (nPDFs) and structure functions in the region $0.2>x>{10}^{-5}$ and $Q^2\ge 4{\mathrm{G}\mathrm{e}\mathrm{V}}^2$. The uncertainties of our predictions due to the uncertainties of the experimental input and the theory are quantified. We determine the relative role of the small ($\sim Q^2$) and large ($\gg Q^2$) diffractive masses in nuclear shadowing as a function of $x$ and find that the large mass contribution, which is an analog of the triple Pomeron exchange, becomes significant only for $x\le {10}^{-4}$. Comparing our predictions to the available fixed-target nuclear deep inelastic scattering data, we argue, based on the current experimental studies of the leading twist diffraction, that the data at moderately small $x\sim 0.01$ and $Q^2\sim 2{\mathrm{G}\mathrm{e}\mathrm{V}}^2$ could contain significant higher twist effects hindering the extraction of nPDFs from that data. Also, we find that the next-to-leading order effects in nuclear shadowing in the ratio of the nucleus to nucleon structure functions $F_2$ are quite sizable. Within the same formalism, we also present results for the impact parameter dependence of nPDFs. We also address the problem of extracting the neutron $F_{2n}(x,Q^2)$ from the deuteron and proton data. We suggest a simple and nearly model-independent procedure of correcting for nuclear shadowing effects using $F_2^A/F_2^D$ ratios.

We consider the generation of a nonperturbative superpotential in F-theory compactifications with flux. We derive a necessary condition for the generation of such a superpotential in F theory. For models with a single volume modulus, we show that the volume modulus is never stabilized by either Abelian instantons or gaugino condensation. We then comment on how our analysis extends to a larger class of compactifications. From our results, it appears that among large volume string compactifications, metastable de Sitter vacua (should any exist) are nongeneric.

In this paper we study the gravitational dielectric phenomena of a D2 brane in the background of Kaluza-Klein monopoles and D6 branes. In both cases the spherical D2 brane with nonzero radius becomes classical solution of the D2-brane action. We also investigate the gravitational Myers effect in the background of D6 branes. This phenomenon occurs since the tension of the D2-brane balances with the repulsive force between D0 branes and D6 branes.

In the previous paper [H. Aoki, S. Iso, and K. Nagao, Nucl. Phys. B 684, 162 (2004)] we studied the ’t Hooft-Polyakov (TP) monopole configuration in the U(2) gauge theory on the fuzzy 2-sphere and showed that it has a nonzero topological charge in the formalism based on the Ginsparg-Wilson relation. In this paper, by showing that the TP monopole configuration is stabler than the U(2) gauge theory without any condensation in the Yang-Mills-Chern-Simons matrix model, we will present a mechanism for dynamical generation of a nontrivial index. We further analyze the instability and decay processes of the U(2) gauge theory and the TP monopole configuration.

When energies or angles of gluons emitted in a gauge-theory process are small and strongly ordered, the emission factorizes in a simple way to all orders in perturbation theory. I show how to unify the various strongly ordered soft, mixed soft-collinear, and collinear limits using antenna factorization amplitudes, which are generalizations of the Catani-Seymour dipole factorization function.

We extend the notion of phantom energy, which is generally accepted for homogeneously distributed matter with $w<-1$ in the universe, on inhomogeneous spherically symmetric spacetime configurations. A spherically symmetric distribution of phantom energy is shown to be able to support the existence of static wormholes. We find an exact solution describing a static spherically symmetric wormhole with phantom energy and show that a spatial distribution of the phantom energy is mainly restricted by the vicinity of the wormhole’s throat. The maximal size of the spherical region, surrounding the throat and containing the most part of the phantom energy, depends on the equation-of-state parameter $w$ and cannot exceed some upper limit.

We consider a quantization of scalar perturbations about a de Sitter brane in a 5-dimensional anti-de Sitter (AdS) bulk spacetime. We first derive the second order action for a master variable $\Omega$ for 5-dimensional gravitational perturbations. For a vacuum brane, there is a continuum of normalizable Kaluza-Klein (KK) modes with $m>3H/2$. There is also a light radion mode with $m=\sqrt{2}H$ which satisfies the junction conditions for two branes, but is non-normalizable for a single brane model. We perform the quantization of these bulk perturbations and calculate the effective energy density of the projected Weyl tensor on the barne. If there is a test scalar field perturbation on the brane, the $m^2=2H^2$ mode together with the zero-mode and an infinite ladder of discrete tachyonic modes become normalizable in a single brane model. This infinite ladder of discrete modes as well as the continuum of KK modes with $m>3H/2$ introduce corrections to the scalar field perturbations at first-order in a slow-roll expansion. We derive the second order action for the Mukhanov-Sasaki variable coupled to the bulk perturbations which is needed to perform the quantization and determine the amplitude of scalar perturbations generated during inflation on the brane.