We calculate the energy-momentum tensor due to electromagnetic vacuum fluctuations between two parallel hyperplanes in more than four dimensions, considering both metallic and MIT boundary conditions. Using the axial gauge, the problem can be mapped upon the corresponding problem with a massless, scalar field satisfying, respectively, Dirichlet or Neumann boundary conditions. The pressure between the plates is constant while the energy density is found to diverge at the boundaries when there are extra dimensions. This can be related to the fact that Maxwell theory is then no longer conformally invariant. A similar behavior is known for the scalar field where a constant energy density consistent with the pressure can be obtained by improving the energy-momentum tensor with the Huggins term. This is not possible for the Maxwell field. However, the change in the energy-momentum tensor with distance between boundaries is finite in all cases.

We study magnetohydrodynamic (MHD) effects arising in the collapse of magnetized, rotating, massive stellar cores to proto-neutron stars (PNSs). We perform axisymmetric numerical simulations in full general relativity with a hybrid equation of state. The formation and early evolution of a PNS are followed with a grid of $2500\times 2500$ zones, which provides better resolution than in previous (Newtonian) studies. We confirm that significant differential rotation results even when the rotation of the progenitor is initially uniform. Consequently, the magnetic field is amplified both by magnetic winding and the magnetorotational instability (MRI). Even if the magnetic energy $E_{\mathrm{EM}}$ is much smaller than the rotational kinetic energy $T_{\mathrm{rot}}$ at the time of PNS formation, the ratio $E_{\mathrm{EM}}/T_{\mathrm{rot}}$ increases to 0.1–0.2 by the magnetic winding. Following PNS formation, MHD outflows lead to losses of rest mass, energy, and angular momentum from the system. The earliest outflow is produced primarily by the increasing magnetic stress caused by magnetic winding. The MRI amplifies the poloidal field and increases the magnetic stress, causing further angular momentum transport and helping to drive the outflow. After the magnetic field saturates, a nearly stationary, collimated magnetic field forms near the rotation axis and a Blandford-Payne–type outflow develops along the field lines. These outflows remove angular momentum from the PNS at a rate given by $\dot{J}\sim \eta E_{\mathrm{EM}}{C}_B$, where $\eta$ is a constant of order $\sim 0.1$ and $C_B$ is a typical ratio of poloidal to toroidal field strength. As a result, the rotation period quickly increases for a strongly magnetized PNS until the degree of differential rotation decreases. Our simulations suggest that rapidly rotating, magnetized PNSs may not give rise to rapidly rotating neutron stars.

We investigate the neutrino masses and mixing pattern in a version of the $SU(3{)}_c\otimes SU(3{)}_L\otimes U(1{)}_X$ model with one extra exotic charged lepton per family as introduced by Ozer. It is shown that an extended scalar sector, together with a discrete $Z_2$ symmetry, is able to reproduce a consistent lepton mass spectrum without a hierarchy in the Yukawa coupling constants, the former as a consequence of a carefull balance between one universal see-saw and two radiative mechanisms.

In this paper the singlet and nonsinglet structure functions have been obtained by solving Dokshitzer, Gribov, Lipatov, Altarelli, Parisi (DGLAP) evolution equations in leading order and next to leading order at the small $x$ limit. Here we have used Taylor series expansion and then the method of characteristics to solve the evolution equations. We have also calculated $t$ and $x$ evolutions of the deuteron structure function and the results are compared with the New Muon Collaboration data.

Recently, gravitational microlensing has been investigated in the framework of the weak field limit of fourth order gravity theory. However, solar system data (i.e. planetary periods and light bending) can be used to put strong constraints on the parameters of this class of gravity theories. We find that these parameters must be very close to those corresponding to the Newtonian limit of the theory.

There is nothing to prevent a higher-dimensional anti–de Sitter bulk spacetime from containing various other branes in addition to hosting our universe, presumed to be a positive-tension 3-brane. In particular, it could contain closed, microscopic branes that form the boundary surfaces of void bubbles and thus violate the null energy condition in the bulk. The possible existence of such micro branes can be investigated by considering the properties of the ground state of a pseudo-Wheeler-DeWitt equation describing brane quantum dynamics in minisuperspace. If they exist, a concentration of these micro branes could act as a fluid of exotic matter able to support macroscopic wormholes connecting otherwise-distant regions of the bulk. Were the brane constituting our universe to expand into a region of the bulk containing such higher-dimensional macroscopic wormholes, they would likely manifest themselves in our brane as wormholes of normal dimensionality, whose spontaneous appearance and general dynamics would seem inexplicably peculiar. This encounter could also result in the formation of baby universes of a particular type.

Scalar self-interactions are known to weaken considerably the current constraints on scalar-mediated fifth forces. We consider a scalar field with a quartic self-interaction and gravitation-strength Yukawa couplings to matter particles. After discussing the phenomenology of this scalar field, we assess the ability of ongoing and planned experiments to detect the fifth force mediated by such a field. Assuming that the quartic and matter couplings are of order unity, the current-generation Eöt-Wash experiment at the University of Washington will be able to explore an interesting subset of parameter space. The next-generation Eöt-Wash experiment is expected to be able to detect, or to rule out, the fifth force due to such a scalar with unit quartic and matter couplings at the $3\sigma$ confidence level.

A new technique is presented for modifying the Einstein evolution equations off the constraint hypersurface. With this approach the evolution equations for the constraints can be specified freely. The equations of motion for the gravitational field variables are modified by the addition of terms that are linear and nonlocal in the constraints. These terms are obtained from solutions of the linearized Einstein constraints.

We derive conditions for stable tracker solutions for both quintessence and $k$-essence in a general cosmological background, $H^2\propto f(\rho )$. We find that tracker solutions are possible only when $\eta \equiv d\ln f/d\ln \rho \approx \mathrm{\text{constant}}$, aside from a few special cases, which are enumerated. Expressions for the quintessence or $k$-essence equation of state are derived as a function of $\eta$ and the equation of state of the dominant background component.

Using the published KTeV sample of $2\times {10}^6$ $K_L\to {\pi }^{\pm }{e}^{\mp }\nu$ decays [1] and a new form factor expansion with a rigorous bound on higher order terms [2], we present a new determination of the $K_L\to {\pi }^{\pm }{e}^{\mp }\nu$ form factor and phase space integral. Compared to the previous KTeV result [1], the uncertainty in the new form factor expansion is negligible and results in an overall uncertainty in the phase space integral ($I_K^e$) that is a factor of 2 smaller: $I_K^e=0.15392\pm 0.00048$.

We investigate the twist-3 pion and kaon distribution amplitudes of the pseudoscalar (${\varphi }_{\pi ,K}^p$) and pseudotensor (${\varphi }_{\pi ,K}^{\sigma }$) types, based on the effective chiral action from the instanton vacuum. Flavor $SU(3)$ symmetry breaking effects are explicitly taken into account. The Gegenbauer moments and the moments of the distribution amplitudes ($⟨{\xi }^m⟩$) are also computed. Our results are summarized as follows: $a_{2,\pi }^p\sim 0.4$, $a_{1,K}^p\sim 0.02$ and $a_{2,K}^p\sim 0.14$, and $a_{2,\pi }^{\sigma }\sim 0.02$ and $a_{1,K}^{\sigma }\sim a_{2,K}^{\sigma }\sim 0$; $⟨{\xi }^2{⟩}_{\pi }^p\sim ⟨{\xi }^2{⟩}_K^p\sim 0.37$ and $⟨\xi {⟩}_K^p\sim 0$, and $⟨{\xi }^2{⟩}_{\pi }^{\sigma }\sim ⟨{\xi }^2{⟩}_K^{\sigma }\sim 0.20$ and $⟨\xi {⟩}_K^{\sigma }\sim 0$. We compare our results with those from the QCD sum rules. We also discuss the relevant Wilson coefficients which were analyzed recently in chiral perturbation theory.

Rigorous bounds are established for the expansion coefficients governing the shape of semileptonic $K\to \pi$ form factors. The constraints enforced by experimental data from $\tau \to K\pi \nu$ eliminate uncertainties associated with model parametrizations in the determination of $|V_{\mathrm{us}}|$. The results support the validity of a powerful expansion that can be applied to other semileptonic transitions.

We investigate dark matter candidates emerging in recently proposed technicolor theories. We determine the relic density of the lightest, neutral, stable technibaryon having imposed weak thermal equilibrium conditions and overall electric neutrality of the Universe. In addition we consider sphaleron processes that violate baryon, lepton and technibaryon number. Our analysis is performed in the case of a first order electroweak phase transition as well as a second order one. We argue that, in both cases, the new technibaryon contributes to the dark matter in the Universe. Finally we examine the problem of the constraints on these types of dark matter components from earth based experiments.

The number of particles produced in high energy experiments is approximated by a negative binomial distribution. Deriving a representation of the distribution from a stochastic equation, conditions for the process to satisfy the distribution are clarified. Based on them, it is proposed that multiparticle production consists of spontaneous and induced production. The rate of the induced production is proportional to the number of existing particles. The ratio of the two production rates remains constant during the process. The “NBD space” is also defined where the number of particles produced in its subspaces follows negative binomial distributions with different parameters.

We consider a scalar field, such as the Higgs boson $H$, coupled to gluons via the effective operator $H\mathrm{tr}{G}_{\mu \nu }{G}^{\mu \nu }$ induced by a heavy-quark loop. We treat $H$ as the real part of a complex field $\varphi$ which couples to the self-dual part of the gluon field-strength, via the operator $\varphi \mathrm{tr}{G}_{\mathrm{SD}\mu \nu }{G}_{\mathrm{SD}}^{\mu \nu }$, whereas the conjugate field ${\varphi }^{†}$ couples to the anti-self-dual part. There are three infinite sequences of amplitudes coupling $\varphi$ to quarks and gluons that vanish at tree level, and hence are finite at one loop, in the QCD coupling. Using on-shell recursion relations, we find compact expressions for these three sequences of amplitudes and discuss their analytic properties.

We study the penguin-dominated $B\to PV$ decays, with $P$ ($V$) representing a pseudoscalar (vector) meson, in the next-to-leading-order (NLO) perturbative QCD (PQCD) formalism, concentrating on the $B\to K\varphi$, $\pi K^{*}$, $\rho K$, and $\omega K$ modes. It is found that the NLO corrections dramatically enhance the $B\to \rho K$, $\omega K$ branching ratios, which were estimated to be small under the naive factorization assumption. The patterns of the direct $CP$ asymmetries $A_{CP}(B^0\to {\rho }^{\mp }{K}^{\pm })\approx A_{CP}(B^{\pm }\to {\rho }^0{K}^{\pm })$ and $|A_{CP}(B^0\to {\pi }^{\mp }{K}^{*\pm })|>|A_{CP}(B^{\pm }\to {\pi }^0{K}^{*\pm })|$ are predicted, differing from $|A_{CP}(B^0\to {\pi }^{\mp }{K}^{\pm })|\gg |A_{CP}(B^{\pm }\to {\pi }^0{K}^{\pm })|$. The above patterns, if confirmed by data, will support the source of strong phases from the scalar penguin annihilation in PQCD. The results for the mixing-induced $CP$ asymmetries $S_f$ are consistent with those obtained in the literature, except that our $S_{{\rho }^0{K}_S}$ is as low as 0.5.

In the calculation of cross sections for infrared-safe observables in high energy collisions at next-to-leading order, one approach is to perform all of the integrations, including the virtual loop integration, numerically. One would use a subtraction scheme that removes infrared and collinear divergences from the integrand in a style similar to that used for real emission graphs. Then one would perform the loop integration by Monte Carlo integration along with the integrations over final state momenta. In this paper, we explore how one can perform the numerical integration. We study the $N$-photon scattering amplitude with a massless electron loop in order to have a case with a singular integrand that is not, however, so singular as to require the subtractions. We report results for $N=4$, $N=5$ with left-handed couplings, and $N=6$.

A Bayesian analysis of the probability of a signal in the presence of background is developed, and criteria are proposed for claiming evidence for, or the discovery of a signal. The method is general and, in particular, applicable to sparsely populated spectra. Monte Carlo techniques to evaluate the sensitivity of an experiment are described. As an example, the method is used to calculate the sensitivity of the GERDA experiment to neutrinoless double beta decay.

Using $13.3{\mathrm{fb}}^{-1}$ of $e^{+}{e}^{-}$ collision data taken in the ${\rm Y}(1S-4S)$ region with the CLEO III detector at the CESR collider, a search has been made for the new resonance $Y(4260)$ recently reported by the BABAR Collaboration. The production of $Y(4260)$ in initial state radiation (ISR), and its decay into ${\pi }^{+}{\pi }^{-}J/\psi$, are confirmed. A good quality fit to our data is obtained with a single resonance. We determine $M(Y(4260))=({4284}_{-16}^{+17}(\mathrm{stat})\pm 4(\mathrm{syst}))\mathrm{MeV}/c^2$, $\Gamma (Y(4260))=({73}_{-25}^{+39}(\mathrm{stat})\pm 5(\mathrm{syst}))\mathrm{MeV}/c^2$, and ${\Gamma }_{ee}(Y(4260))\times \mathcal{B}(Y(4260)\to {\pi }^{+}{\pi }^{-}J/\psi )=({8.9}_{-3.1}^{+3.9}(\mathrm{stat})\pm 1.8(\mathrm{syst}))\mathrm{eV}/c^2$.

We analyze mesons at finite temperature in a chiral, confining string dual. The temperature dependence of low-spin as well as high-spin meson masses is shown to exhibit a pattern familiar from the lattice. Furthermore, we find the dissociation temperature of mesons as a function of their spin, showing that at a fixed quark mass, mesons with larger spins dissociate at lower temperatures. The Goldstone bosons associated with chiral symmetry breaking are shown to disappear above the chiral symmetry restoration temperature. Finally, we show that holographic considerations imply that large-spin mesons do not experience drag effects when moving through the quark-gluon plasma. They do, however, have a maximum velocity for fixed spin, beyond which they dissociate.