We investigate the possibility of D-term inflation within the framework of type-I string-inspired models. Although the D-term inflation model has the excellent property that it is free of the so-called $\eta$ problem, two serious problems appear when we embed D-term inflation in string theory: the magnitude of the FI term and the rolling motion of the dilaton. In the present paper, we analyze the potential of D-term inflation in type-I-inspired models and study the behavior of dilaton and twisted moduli fields. Adopting the nonperturbative superpotential induced by gaugino condensation, the twisted moduli can be stabilized. If the dilaton is in a certain range, it evolves very slowly and does not run away to infinity. Thus D-term-dominated vacuum energy becomes available for driving inflation. By studying the density perturbation generated by the inflation model, we derive the constraints on model parameters and give some implications on D-term inflation in type-I-inspired models.

We consider for the first time the ability of present-day cosmic microwave background (CMB) anisotropies data to determine the primordial helium mass fraction $Y_p.$ We find that CMB data alone give the confidence interval $0.160<\mathrm{}{Y}_p<0.501\mathrm{}$ (at 68% C.L.). We analyze the impact on the baryon abundance as measured by CMB and discuss the implications for big bang nucleosynthesis. We identify and discuss correlations between the helium mass fraction and both the redshift of reionization and the spectral index. We forecast the precision of future CMB observations, and find that Planck alone will measure $Y_p$ with error bars of 5%. We point out that the uncertainty in the determination of the helium fraction will have to be taken into account in order to correctly estimate the baryon density from Planck-quality CMB data.

Explicit expressions for the differential and total rates and emissivities of neutrino pairs from the photoneutrino process $e^{\pm }+\overrightarrow{\gamma }{e}^{\pm }+\nu +\overline{\nu }$ in hot and dense matter are derived. Full information about the emitted neutrinos is retained by evaluating the squared matrix elements for this process which was hitherto bypassed through the use of Lenard’s identity in obtaining the total neutrino emissivities. Accurate numerical results are presented for widely varying conditions of temperature and density. Analytical results helpful in understanding the qualitative behaviors of the rates and emissivities in limiting situations are derived. The corresponding production and absorption kernels in the source term of the Boltzmann equation for neutrino transport are developed. The appropriate Legendre coefficients of these kernels, in forms suitable for multigroup flux-limited diffusion schemes, are also provided.

The growth of large scale structure is studied in a universe containing both cold dark matter (CDM) and a generalized Chaplygin gas (GCG). The GCG is assumed to contribute only to the background evolution of the universe, while the CDM component collapses and forms structures. We present some new analytical as well as numerical results for linear and nonlinear growth in such a model. The model passes the standard cosmological distance test without the need of a cosmological constant. But we find that the scenario is severely constrained by current observations of large scale structure. Any small deviations of the GCG parameters away from the standard Lambda dominated cosmology produces substantial suppression for the growth of structures.

In this paper, we present results for large-angle cosmic microwave background anisotropies generated from high resolution simulations of cosmic string networks in a range of flat Friedmann-Robertson-Walker universes with a cosmological constant. Using an ensemble of all-sky maps, we compare with the Cosmic Background Explorer data to infer a normalization (or upper bound) on the string linear energy density $\mu .$ For a flat matter-dominated model $({\Omega }_M=1)$ we find $G\mu {/c}^2\approx 0.7\times {10}^{-6},$ which is lower than previous constraints probably because of the more accurate inclusion of string small-scale structure. For a cosmological constant within an observationally acceptable range, we find a relatively weak dependence with $G\mu {/c}^2$ less than 10% higher.

We study the evolution of Kaluza-Klein bubble spacetimes in vacuum and electrovac scenarios by numerical means. We find strong evidence against the formation of naked singularities in (i) scenarios with negative masses displaying initially collapsing conditions and (ii) scenarios with negative masses displaying initially expanding conditions, previously reported to give rise to such singularities. Additionally, we show that the presence of strong gauge fields implies that an initially collapsing bubble bounces back and expands. By fine-tuning the strength of the gauge field we find that the solution approaches a static bubble solution.

We consider spherically symmetric spacetimes with matter whose timelike flow is assumed to be shear-free. A number of results on the formation and visibility of spacetime singularities is proven, with the main one being that shear-free collapse cannot admit locally naked singularities (which implies the absence of globally naked singularities). We conjecture that shear is a necessary condition for the occurrence of locally naked singularities in generic gravitational collapse.

We study the decay ${\Lambda }_b\to \Lambda {\pi }^{+}{\pi }^{-}.$ The branching fraction is predicted to be about $4.4\times {10}^{-8}.$ Within the standard model, we compute the T-odd triple product asymmetries to be about 1.4, 4.3, 6.5, and 7.2 %, respectively, due to $s_{{\Lambda }_b,\Lambda }\cdot (p_{\Lambda }\times p_{\pi })$ and $p_{\Lambda ,\pi }\cdot (s_{\Lambda }\times s_{{\Lambda }_b}).\mathrm{}$

Recently, a type of grand unified theory model with an extra dimension in AdS space has successfully solved the doublet-triplet problem, maintaining proton stability, and allowing colored Higgs bosons and colored Higgsinos in the TeV mass region. We study the hadronic production and detection of these TeV colored Higgsinos and Higgs bosons. If the colored Higgsino is lighter than the colored Higgs boson, the colored Higgs boson will decay into a colored Higgsino and a gluino or a gravitino, and vice versa. The signatures would be stable massive charged particles with jets or missing energies.

We calculate the one-loop contribution from the $H^{\pm }{W}^{\mp }Z$ coupling to the static electromagnetic properties of the W boson. Although this coupling is absent at the tree level in all Higgs-doublet models, it can be induced at this order in models including Higgs-triplet representations. It is found that the $H^{\pm }{W}^{\mp }Z$ contribution can be as important as those arising from other couplings including Higgs bosons, such as the standard model coupling $W^{\pm }{W}^{\mp }H$ or two-Higgs-doublet model couplings $H^{\pm }{W}^{\mp }{\phi }^0$ and $W^{\pm }{W}^{\mp }{\phi }^0,$ with ${\phi }^0=h,H,$ A.

Recent data from the E925 Collaboration at Brookheaven National Laboratory show a significant energy dependence of the single-spin left-right asymmetry in inclusive hadron production in hadron-hadron collisions. We analyze the experimental results and show that the observed energy dependence can be reproduced naturally in the picture proposed in a previous Letter. We fix all the parameters at the Fermilab E704 energy and calculate the asymmetry at the BNL E925 energy. We compare the results with the data and make predictions for experiments at even higher energies.

We have previously shown that the decay of high-energy neutrinos from distant astrophysical sources would be revealed by flavor ratios that deviate strongly from the ${\phi }_{{\nu }_e}:{\phi }_{{\nu }_{\mu }}:{\phi }_{{\nu }_{\tau }}=1:1:1\mathrm{}$ expected from oscillations alone. Here we show that the deviations are significantly larger when the mixing angle ${\theta }_{13}$ and the CP phase $\delta$ are allowed to be nonzero. If neutrinos decay, this could allow measurement of ${\theta }_{13}$ and $\delta$ in IceCube and other near-term neutrino telescopes.

The observed strong phase difference of 30° between $I=\frac{3}{2}$ and $I=\frac{1}{2}$ final states for the decay $\overrightarrow{B}D\pi$ is analyzed in terms of rescattering like $D^{*}\overrightarrow{\rho }D\pi ,$ etc. It is concluded that for the decay $B^0\to D^{+}{\pi }^{-}$ the strong phase is only about 10°. Implications for the determination of $\sin (2\mathrm{}\beta +\gamma )$ are discussed.

A general formalism is presented for violations of Lorentz and CPT symmetry in the neutrino sector. The effective Hamiltonian for neutrino propagation in the presence of Lorentz and CPT violation is derived, and its properties are studied. Possible definitive signals in existing and future neutrino-oscillation experiments are discussed. Among the predictions are direction-dependent effects, including neutrino-antineutrino mixing, sidereal and annual variations, and compass asymmetries. Other consequences of Lorentz and CPT violation involve unconventional energy dependences in oscillation lengths and mixing angles. A variety of simple models both with and without neutrino masses are developed to illustrate key physical effects. The attainable sensitivities to coefficients for Lorentz violation in the Standard-Model Extension are estimated for various types of experiments. Many experiments have potential sensitivity to Planck-suppressed effects, comparable to the best tests in other sectors. The lack of existing experimental constraints, the wide range of available coefficient space, and the variety of novel effects imply that some or perhaps even all of the existing data on neutrino oscillations might be due to Lorentz and CPT violation.

We perform a systematic reevaluation of the constraints on the flavor-changing neutral current parameters in R-parity conserving and R-parity violating supersymmetric models. As a typical process, we study the constraints coming from measurements on the $B^0-{\overline{B}}^0$ system of the supersymmetric ${\delta }_{13}^d$ parameters, as well as on the products of ${\lambda }^{\prime }$ type R-parity violating couplings. Present data allow us to put constraints on both the real and imaginary parts of the relevant parameters.

In the minimal supersymmetric standard model (MSSM), the neutralinos, the spin-1/2 Majorana superpartners of the neutral gauge and Higgs bosons, are expected to be among the light supersymmetric particles that can be produced copiously at future high-energy colliders. We analyze two-body neutralino decays into a neutralino plus a Z boson or the lightest neutral Higgs boson h, allowing the relevant parameters to have complex phases. We show that the two-body tree-level decays of neutralinos are kinematically allowed in a large region of the MSSM parameter space and they can provide us with a powerful probe of the Majorana nature and CP properties of the neutralinos through the Z-boson polarization measured from Z-boson leptonic decays.

We reconstruct the standard model quark masses and the Cabibbo-Kobayashi-Maskawa (CKM) matrix from a five-dimensional model, with the fifth dimension compactified on an $S^1{/Z}_2$ orbifold. Fermions are localized only at the orbifold fixed points and the induced quark mass matrices are almost democratic. Two specific versions of our model with 15 and 24 parameters are presented, and for both versions we can reproduce the quark mass spectrum and CKM matrix correctly to the level they are observed in current experiments.

This paper studies models with extended electroweak gauge sectors of the form $\mathrm{SU}\left(2\right)\mathrm{}\times \mathrm{SU}\left(2\right)\mathrm{}\times U\left(1\right)\mathrm{}\times \left[\mathrm{SU}\right(2)\mathrm{}orU(1\left)\mathrm{}\right].$ We establish the general behavior of corrections to precision electroweak observables in this class of theories and connect our results to previous work on specific models whose electroweak sectors are special cases of our extended group.

We study numerically the length distributions of the infrared monopole clusters in pure SU(2) QCD. These distributions are Gaussian for all studied blocking steps of monopoles, lattice volumes and lattice coupling constant. We also investigate the monopole action for the infrared monopole clusters. The knowledge of both the length distribution and the monopole action allows us to determine the effective entropy of the monopole currents. The entropy is a descending function of blocking scale, indicating that the effective degrees of freedom of the extended monopoles are getting smaller as the blocking scale increases.