With the goal of taking a step toward the construction of astrophysically realistic initial data for numerical simulations of black holes, we for the first time derive a family of fully general relativistic initial data based on post-2-Newtonian expansions of the 3-metric and extrinsic curvature without spin. It is expected that such initial data provide a direct connection with the early inspiral phase of the binary system. We discuss a straightforward numerical implementation, which is based on a generalized puncture method. Furthermore, we suggest a method to address some of the inherent ambiguity in mapping post-Newtonian data onto a solution of the general relativistic constraints.

In this paper we study a type of one-field model for open inflationary universe models in the context of the Jordan-Brans-Dicke theory. In the scenario of a one-bubble universe model we determine and characterize the existence of the Coleman–De Luccia instanton, together with the period of inflation after tunneling has occurred. Our results are analogous to those found in the Einstein general relativity models.

We pursue applications of the light-front reduction of current matrix elements in the Bethe-Salpeter formalism. The normalization of the reduced wave function is derived from the covariant framework and related to nonvalence probabilities using familiar Fock space projection operators. Using a simple model, we obtain expressions for generalized parton distributions that are continuous. The nonvanishing of these distributions at the crossover between kinematic regimes (where the plus component of the struck quark’s momentum is equal to the plus component of the momentum transfer) is tied to higher Fock components. Moreover continuity holds due to relations between Fock components with vanishing plus momentum. Finally, we apply the light-front reduction to timelike form factors and derive expressions for the generalized distribution amplitudes in this model.

We apply the light-front reduction of the Bethe-Salpeter equation to bound-state matrix elements of the plus component of the electromagnetic current. Using a simple $\mathrm{}(1+1)\mathrm{}$-dimensional model to calculate form factors, we focus on two cases. In one case, the interaction is dominated by a term instantaneous in light-cone time. Here effects of higher Fock states are negligible and the form factor can be effectively expressed using non-wave-function vertices and crossed interactions. If the interaction is not instantaneous, non-wave-function vertices are replaced by contributions from higher Fock states. These higher Fock components arise from the covariant formalism via the energy poles of the Bethe-Salpeter vertex and the electromagnetic vertex. The replacement of non-wave-function vertices in time-ordered perturbation theory is a theorem which directly extends to generalized parton distributions, e.g., in 3+1 dimensions.

We discuss the Gubser-Klebanov-Polyakov proposal for the gauge-string theory correspondence for gauge theories in curved space. Specifically, we consider Klebanov-Tseytlin cascading gauge theory compactified on $S^3.$ We explain the regime when this gauge theory is a small deformation of the superconformal $\mathcal{N}=1\mathrm{}$ gauge theory on the world volume of regular D3-branes at the tip of the conifold. We study closed string states on the leading Regge trajectory in this background, and attempt to identify the dual gauge theory twist 2 operators.

In three-dimensional quantum electrodynamics $\left({\mathrm{QED}}_3\right)$ with a massive gauge boson, we investigate the Dyson-Schwinger equation for the fermion self-energy in the Landau gauge and find that chiral symmetry breaking (CSB) occurs when the gauge boson mass $\xi$ is smaller than a finite critical value ${\xi }_{\mathrm{cv}}$ but is suppressed when $\xi >{\xi }_{\mathrm{cv}}.$ We further show that the critical value ${\xi }_{\mathrm{cv}}$ does not qualitatively change after considering higher order corrections from the wave function renormalization and vertex function. Based on the relation between CSB and the gauge boson mass $\xi ,$ we give a field theoretical description of the competing antiferromagnetic and superconducting orders and, in particular, the coexistence of these two orders in high temperature superconductors. When the gauge boson mass $\xi$ is generated via the instanton effect in a compact ${\mathrm{QED}}_3$ of massless fermions, our result shows that CSB coexists with the instanton effect in a wide region of $\xi ,$ which can be used to study the confinement-deconfinement phase transition.

Gravitational lensing in metric theories of gravity is discussed. I introduce a generalized approximate metric element, inclusive of both post-post-Newtonian contributions and a gravitomagnetic field. Following Fermat’s principle and standard hypotheses, I derive the time delay function and deflection angle caused by an isolated mass distribution. Several astrophysical systems are considered. In most of the cases, the gravitomagnetic correction offers the best perspectives for an observational detection. Actual measurements distinguish only marginally different metric theories from each other.

Hestenes has shown that a bispinor field on a Minkowski space-time is equivalent to an orthonormal tetrad of one-forms together with a complex scalar field. More recently, the Dirac and Einstein equations were unified in a tetrad formulation of a Kaluza-Klein model which gives precisely the usual Dirac-Einstein Lagrangian. In this model, Dirac’s bispinor equation is obtained in the limit for which the radius of higher compact dimensions of the Kaluza-Klein manifold becomes vanishingly small compared with the Planck length. For a small but finite radius, the Kaluza-Klein model predicts the velocity splitting of single fermion wave packets. That is, the model predicts that a single fermion wave packet will split into two wave packets with slightly different group velocities. The observation of such wave packet splits would determine the size of the Kaluza-Klein radius. If wave packet splits were not observed in experiments with currently achievable accuracies, the Kaluza-Klein radius would be bounded by at most ${10}^{-25}$ times the Planck length.

We study the dependence of the location of the cosmic microwave background radiation peaks on the parameters of the generalized Chaplygin gas model, whose equation of state is given by $p=-A/{\rho }^{\alpha },$ where A is a positive constant and $0<\mathrm{}\alpha <~1.$ We find, in particular, that observational data arising from Archeops, BOOMERANG, supernova and high-redshift observations allow constraining significantly the parameter space of the model. Our analysis indicates that the emerging model is clearly distinguishable from the $\alpha =1\mathrm{}$ Chaplygin case and the $\Lambda \mathrm{CDM}$ model.

Hadron collider cross sections for $t\overline{t}$ production and dilepton, single-lepton and all-jet decays with up to 2 additional jets are calculated using complete LO matrix elements with 6-, 7-, and 8-particle final states. The fixed-width, complex-mass, and overall-factor schemes (FWS, CMS, and OFS) are employed and the quality of narrow-width and double-pole approximations (NWA and DPA) is investigated for inclusive production and suppressed backgrounds to new particle searches. NWA and DPA cross sections differ by 1% or less. The inclusion of sub- and nonresonant amplitudes effects a cross section increase of 5–8 % at $\mathrm{pp}$ supercolliders, but only minor changes at the Fermilab Tevatron. On-shell $t\overline{t}/Wtb$ backgrounds for the $\overrightarrow{H}\mathrm{WW}$ decay in weak boson fusion, the hadronic $\tau$ decay of a heavy $H^{\pm }$ and the $\overrightarrow{\phi }h\overrightarrow{h}\tau \tau b\overline{b}$ radion decay at the CERN LHC are updated, with corrections ranging from 3% to 30%. FWS and CMS cross sections are uniformly consistent, but OFS cross sections are up to 6% smaller for some backgrounds.

We present expressions for shape variables of B decay distributions in several different mass schemes, to order ${\alpha }_s^2{\beta }_0$ and ${\Lambda }_{\mathrm{QCD}}^3{/m}_b^3.$ Such observables are sensitive to the b quark mass and matrix elements in the heavy quark effective theory, and recent measurements allow precision determinations of some of these parameters. We perform a combined fit to recent experimental results from CLEO, BABAR, and DELPHI, and discuss the theoretical uncertainties due to nonperturbative and perturbative effects. We discuss the possible discrepancy between the OPE prediction, recent BABAR results and the measured branching fraction to D and $D^{*}$ states. We find $|V_{\mathrm{cb}}|=(40.8\mathrm{}\pm 0.9)\times {10}^{-3}$ and $m_b^{1S}=4.74\mathrm{}\pm 0.10\mathrm{GeV},$ where the errors are dominated by experimental uncertainties.

We analyze the renormalization properties of quantum field theories in de Sitter space and show that at most two of the maximally invariant vacuum states of free fields lead to consistent perturbation expansions. One is the Euclidean vacuum. The other is consistent with an interpretation as an antipodal orbifold of de Sitter space. We provide a Hamiltonian quantization in which this vacuum is viewed as living on the future half of global de Sitter space with boundary conditions on fields at the origin of time. We argue that the perturbation series in this case has divergences at the origin which render the future evolution of the system indeterminate, without a better understanding of high energy physics.

We propose that, for every event in de Sitter space, there is a CPT-conjugate event at its antipode. Such an “elliptic” $Z_2$ identification of de Sitter space provides a concrete realization of observer complementarity: every observer has complete information. It is possible to define the analogue of an S matrix for quantum gravity in elliptic de Sitter space that is measurable by all observers. In a holographic description, S-matrix elements may be represented by correlation functions of a dual (conformal field) theory that lives on the single boundary sphere. S-matrix elements are de Sitter invariant, but have different interpretations for different observers. We argue that Hilbert states do not necessarily form representations of the full de Sitter group, but just of the subgroup of rotations. As a result, the Hilbert space can be finite dimensional and still have a positive norm. We also discuss the elliptic interpretation of de Sitter space in the context of type ${\mathrm{IIB}}^{*}$ string theory.

In the framework of nonrelativistic quantum chromodynamics and the parton model, we estimate, in detail, the production cross section for polarized $J/\psi$ from B meson decays. In order to contrast with data, we also take into account additional $J/\psi$ production due to the decay of excited charmonium states. We calculate the helicity parameter $\alpha$ and, as an application, we study our results for the Fermilab Tevatron. This is in contrast with the earlier studies which were performed for prompt $J/\psi$ production from $p\overline{p}$ collisions. Our estimates are, for $J/\psi$ from B decays, ${\alpha }_{J/\psi }=-0.04\pm 0.06$ and, for B decays to ${\psi }^{\prime },$ ${\alpha }_{{\psi }^{\prime }}=-0.03\pm \mathrm{0.07.}$ These results have been evaluated in the $J/\psi$ transverse momentum interval $10\mathrm{GeV}<~k_T<~30\mathrm{GeV}.$ In the limit of the color singlet model, $\alpha$ shows a direct dependence on the Peterson parameter, thereby reflecting the dynamics of the b quark hadronization. With run II of the Tevatron, it is expected that the fits for $\alpha$ will improve by about a factor of 50, leading to better limits on the matrix elements.

We hunt for and discuss manifestly CP-violating effects which are mediated by Majorana phases. These phases are present if the standard model neutrinos are Majorana particles. We argue that while Majorana phases do affect the strength of neutrinoless double beta decay (a well known fact), they do so in a way that involves no manifest violation of CP. The conditions for manifestly CP-violating phenomena—differences between the rates for CP-mirror-image processes—are presented, and three examples are discussed: (i) neutrino $\leftrightarrow$ antineutrino oscillation; (ii) rare decays of K and B mesons and their antiparticles; and (iii) the lepton asymmetry generated by the decay of hypothetical very heavy right-handed “seesaw” neutrinos. We also find that, for the case of degenerate light neutrinos, manifestly CP-violating effects in neutrino $\leftrightarrow$ antineutrino oscillation vanish, although flavor-changing transitions do not. Finally, we comment on leptogenesis with degenerate right-handed neutrinos, and contrast it with the neutrino $\leftrightarrow$ antineutrino oscillation case.

This short note considers, within the external field approach outlined in a previous paper, the role of the lowest lying gluon Landau mode in QCD in the high temperature limit. Its influence on a temperature- and field-dependent running coupling constant is examined. The thermal imaginary part of the mode is temperature independent in our approach and exactly cancels the well-known zero temperature imaginary part, thus rendering the Savvidy vacuum stable. Combining the real part of the mode with the contributions from the higher lying Landau modes and the vacuum contribution, a field-independent coupling ${\alpha }_s\mathrm{}\left(T\right)\mathrm{}$ is obtained. It can be interpreted as the ordinary zero temperature running coupling constant with average thermal momenta $〈k〉\approx 2\pi T$ for gluons and $〈k〉\approx \pi T$ for quarks.

We study, at the one loop level, the dominant contributions from a single universal extra dimension to the process $\overrightarrow{Z}b\overline{b}.$ By resorting to the gaugeless limit of the theory we explain why the result is expected to display a strong dependence on the mass of the top quark, not identified in the early literature. A detailed calculation corroborates this expectation, giving rise to a lower bound for the compactification scale which is comparable to that obtained from the $\rho$ parameter. An estimate of the subleading corrections is furnished, together with a qualitative discussion on the difference between the present results and those derived previously for the nonuniversal case.

We study the effects of chiral logs on the heavy→light pseudoscalar meson transition form factors by using standard and quenched chiral perturbation theory combined with the static heavy quark limit. The resulting expressions are used to indicate the size of uncertainties due to the use of the quenched approximation in the current lattice studies. They may also be used to assess the size of systematic uncertainties induced by missing chiral log terms in extrapolating toward the physical pion mass. We also provide the coefficient multiplying the quenched chiral log, which may be useful if the quenched lattice studies are performed with very light mesons.

We discuss the perturbative QCD approach for the exclusive two body B meson decays to light mesons. We briefly review its ingredients and some important theoretical issues on the factorization approach. We show numerical results which are compatible with present experimental data for charmless B meson decays. In particular, we predict the possibility of large direct $\mathrm{CP}$ violation effects in $B^0\to {\pi }^{+}{\pi }^{-}\left[\right(23\mathrm{}\pm 7\%\left)\right]$ and $B^0\to K^{+}{\pi }^{-}\left[\right(-17\pm 5\%\left)\right].$ In the last section we investigate two methods to determine the weak phases ${\phi }_2$ and ${\phi }_3$ from $\overrightarrow{B}\pi \pi ,K\pi$ processes. We obtain bounds on ${\phi }_2$ and ${\phi }_3$ from present experimental measurements.