Within the low-energy effective minimal supersymmetric extension of the standard model (effMSSM) we calculate the neutralino relic density taking into account slepton-neutralino and neutralino-chargino or neutralino-neutralino coannihilation channels. We perform a comparative study of these channels and conclude that both of them give sizable contributions to the reduction of the relic density. Because of these coannihilation processes, some models (mostly with large neutralino masses) enter into the cosmologically interesting region for relic density, but other models leave this region. Nevertheless, in general, the predictions for direct and indirect dark matter detection rates are not strongly affected by these coannihilation channels in the effMSSM.

We investigate an $O\left(a\right)\mathrm{}$ improved quark action on anisotropic lattices as a potential framework for heavy quark physics, which may enable high precision computations of hadronic matrix elements for heavy-light mesons. The relativity relations of heavy-light mesons as well as of heavy quarkonium are examined on a quenched lattice with a spatial lattice cutoff $a_{\sigma }^{-1}\simeq 1.6\hspace{0.5em}\mathrm{GeV}$ and a (renormalized) anisotropy $\xi =4.\mathrm{}$ We find that the corresponding bare anisotropy parameter, once tuned for the massless quark, describes both heavy-heavy and heavy-light mesons within 2% accuracy for a quark mass $a_{\sigma }{m}_Q<0.8,$ a range which covers the charm quark. This bare anisotropy parameter also successfully describes the heavy-light mesons alone even in the quark mass region $a_{\sigma }{m}_Q<~1.2$ within the same accuracy. Beyond this region, the discretization effects seem to grow gradually. The renormalized anisotropy $\xi$ turns out to be roughly equal to the factor stretching the quark mass region in which the parameters in the action are applicable for heavy-light systems with well controlled systematic errors.

We study quenched QCD at finite chemical potential ${\mu }_I$ for the third component of isospin and quenched two-color QCD at finite chemical potential $\mu$ for quark number. In contrast with the quenched approximation to QCD at finite quark-number chemical potential, the quenched approximations to these theories behave similarly to the full theories. The reason is that these theories have real positive fermion determinants. In both of these theories there is some critical chemical potential above which the charge coupled to the chemical potential is spontaneously broken. In each case, the transition appears to be second order. We study the scaling properties near the critical point using scaling functions suggested by effective (chiral) Lagrangians and find evidence for scaling with mean-field critical exponents in each case. The subtleties associated with observing the critical scaling of these theories are discussed.

We calculate the photon production cross section in $\mathrm{pA}$ collisions under the assumption that the nucleus has reached the saturation regime, while the proton can be described by the standard parton distribution functions. We show that, due to the strong classical field $O(1/g)\mathrm{}$ of the nucleus, bremsstrahlung diagrams become dominant over the direct photon diagrams. In particular, we show that $\gamma$-jet transverse momentum spectrum and correlations are very sensitive to gluon saturation effects in the nucleus.

We present a systematical study of two-body and three-body charmless baryonic B decays. The branching ratios for two-body modes are in general very small, typically less than ${10}^{-6},$ except that $\mathcal{B}{(B}^{-}\to p{\overline{\Delta }}^{--})\sim 1\times {10}^{-6}.$ In general, $\overline{B}\to N\overline{\Delta }>\overline{B}\to N\overline{N}$ due to the large coupling constant for ${\Sigma }_b\to B\Delta .$ For three-body modes we focus on octet baryon final states. The leading three-dominated modes are $B^0\to p\mathrm{n̄}{\pi }^{-}\left({\rho }^{-}\right),$ $n\overline{p}{\pi }^{+}\left({\rho }^{+}\right)$ with a branching ratio of order $3\times {10}^{-6}$ for $B^0\to p\mathrm{n̄}{\pi }^{-}$ and $8\times {10}^{-6}$ for $B^0\to p\mathrm{n̄}{\rho }^{-}.$ The penguin-dominated decays with strangeness in the meson, e.g., $B^{-}\to p\overline{p}{K}^{-\left(*\right)}$ and $B^0\to p\mathrm{n̄}{K}^{-\left(*\right)},$ $n\mathrm{n̄}{K}^{0\left(*\right)},$ have appreciable rates and the $N\overline{N}$ mass spectrum peaks at low mass. The penguin-dominated modes containing a strange baryon, e.g., $B^0\to {\Sigma }^0\overline{p}{\pi }^{+},$ ${\Sigma }^{-}\mathrm{n̄}{\pi }^{+},$ have branching ratios of the order of $(1\mathrm{}–4)\times {10}^{-6}.$ In contrast, the decay rate of $B^0\to \Lambda \overline{p}{\pi }^{+}$ is smaller. We explain why some of the charmless three-body final states in which baryon-antibaryon pair production is accompanied by a meson have a larger rate than their two-body counterparts: either the pole diagrams for the former have an antitriplet bottom baryon intermediate state, which has a large coupling to the B meson and the nucleon, or they are dominated by the factorizable external W-emission process.

We calculate the coefficients in the chiral Lagrangian approximately from QCD based on a previous study of deriving the chiral Lagrangian from the first principles of QCD in which the chiral Lagrangian coefficients are defined in terms of certain Green’s functions in QCD. We first show that, in the large-$N_c$ limit, the anomaly part contributions to the coefficients are exactly cancelled by certain terms in the normal part contributions, and the final results of the coefficients only concern the remaining normal part contributions depending on QCD interactions. We then do the calculation in a simple approach with the approximations of taking the large-$N_c$ limit, the leading order in dynamical perturbation theory, and the improved ladder approximation; thereby the relevant Green’s functions are expressed in terms of the quark self-energy $\Sigma {(p}^2).\mathrm{}$ By solving the Schwinger-Dyson equation for $\Sigma {(p}^2),$ we obtain the approximate QCD predicted coefficients and quark condensate which are consistent with the experimental values.

The unitarity correction effects encoded in the Glauber-Mueller approach are taken into account to calculate the differential cross sections in the Drell-Yan process in the rest frame. A detailed study of the Drell-Yan process in terms of the ${\gamma }^{*}q$ transverse separation and the color dipole size, and of the effective dipole cross section, is performed and compared with the available small x data. Estimates for the Drell-Yan cross section at BNL RHIC energies are presented and discussed.

In this paper we show how gauge symmetries in an effective theory can be used to simplify proofs of factorization formulas in highly energetic hadronic processes. We use the soft-collinear effective theory, generalized to deal with back-to-back jets of collinear particles. Our proofs do not depend on the choice of a particular gauge, and the formalism is applicable to both exclusive and inclusive factorization. As examples we treat the $\pi -\gamma$ form factor $(\gamma {\gamma }^{*}\to {\pi }^0),$ light meson form factors $\left({\gamma }^{*}\overrightarrow{M}M\right),$ as well as deep inelastic scattering ${(e}^{-}\overrightarrow{p}{e}^{-}X),$ the Drell-Yan process $(p\overline{p}\to {\mathrm{Xl}}^{+}{l}^{-}),$ and deeply virtual Compton scattering $\left({\gamma }^{*}\overrightarrow{p}{\gamma }^{\left(*\right)}p\right).\mathrm{}$

The shapes of the inclusive photon spectra in the processes $J/\overrightarrow{\psi }\gamma X$ and $\overrightarrow{{\rm Y}}\gamma X$ have been analyzed using all available experimental data. Relativistic, higher order QCD, and gluon mass corrections were taken into account in the fitted functions. Only on including the gluon mass corrections were consistent and acceptable fits obtained. Values of ${0.721}_{-0.068}^{+0.016\mathrm{}}\hspace{0.5em}\mathrm{GeV}$ and ${1.18}_{-0.29}^{+0.09\mathrm{}}\hspace{0.5em}\mathrm{GeV}$ were found for the effective gluon masses (corresponding to Born level diagrams) for $J/\psi$ and ${\rm Y},$ respectively. The width ratios $\Gamma \left(\overrightarrow{V}\mathrm{hadrons}\right)/\Gamma (\overrightarrow{V}\gamma +\mathrm{hadrons})V=J/\psi ,{\rm Y},$ were used to determine ${\alpha }_s\left(1.5\mathrm{}\hspace{0.5em}\mathrm{GeV}\right)$ and ${\alpha }_s\left(4.9\mathrm{}\hspace{0.5em}\mathrm{GeV}\right).\mathrm{}$ Values consistent with the current world average ${\alpha }_s$ were obtained only when gluon mass correction factors, calculated using the fitted values of the effective gluon mass, were applied. A gluon mass $\simeq 1\hspace{0.5em}\mathrm{GeV},$ as suggested by these results, is consistent with previous analytical theoretical calculations and independent phenomenological estimates, as well as with a recent, more accurate, lattice calculation of the gluon propagator in the infrared region.

The Antarctic muon and neutrino detector array (AMANDA) began collecting data with ten strings in 1997. Results from the first year of operation are presented. Neutrinos coming through the Earth from the Northern Hemisphere are identified by secondary muons moving upward through the array. Cosmic rays in the atmosphere generate a background of downward moving muons, which are about ${10}^6$ times more abundant than the upward moving muons. Over 130 days of exposure, we observed a total of about 300 neutrino events. In the same period, a background of $1.05\times {10}^9$ cosmic ray muon events was recorded. The observed neutrino flux is consistent with atmospheric neutrino predictions. Monte Carlo simulations indicate that 90% of these events lie in the energy range 66 GeV to 3.4 TeV. The observation of atmospheric neutrinos consistent with expectations establishes AMANDA-B10 as a working neutrino telescope.

In this paper we take the first step towards a nondiagrammatic formulation of the pinch technique. In particular we proceed into a systematic identification of the parts of the one-loop and two-loop Feynman diagrams that are exchanged during the pinching process in terms of unphysical ghost Green’s functions; the latter appear in the standard Slavnov-Taylor identity satisfied by the tree-level and one-loop three-gluon vertex. This identification allows for the consistent generalization of the intrinsic pinch technique to two loops, through the collective treatment of entire sets of diagrams, instead of the laborious algebraic manipulation of individual graphs, and sets up the stage for the generalization of the method to all orders. We show that the task of comparing the effective Green’s functions obtained by the pinch technique with those computed in the background field method Feynman gauge is significantly facilitated when employing the powerful quantization framework of Batalin and Vilkovisky. This formalism allows for the derivation of a set of useful nonlinear identities, which express the background field method Green’s functions in terms of the conventional (quantum) ones and auxiliary Green’s functions involving the background source and the gluonic antifield; these latter Green’s functions are subsequently related by means of a Schwinger-Dyson type of equation to the ghost Green’s functions appearing in the aforementioned Slavnov-Taylor identity.

We present the formalism of q-stars with local or global $U\left(1\right)\mathrm{}$ symmetry. The equations we formulate are solved numerically and provide the main features of the soliton star. We study its behavior when the symmetry is local in contrast with the global case. A general result is that the soliton remains stable and does not decay into free particles and the electrostatic repulsion preserves it from gravitational collapse. We also investigate the case of a q-star with a nonminimal energy-momentum tensor and find that the soliton is stable even in some cases of collapse when the coupling to gravity is absent.

We study a Grassmannian σ model coupled to a Chern-Simons term. In the presence of a novel topological term the model admits exact self-dual vortex solutions which are identical to those of a pure Grassmannian model, but the topological charge has a physical meaning as a magnetic flux since the gauge field is no longer auxiliary. We also extend the theory to a noncommutative plane and analyze the BPS solutions.

We investigate the possibility of generating sizable dipole radiation in relativistic theories of gravity. Optimal parameters to observe their effects through the orbital period decay of binary star systems are discussed. Constraints on gravitational couplings beyond general relativity are derived.

We study black hole evaporation of near-extremal black holes in spherically reduced models with asymptotically Minkowskian spacetime, with the effects of the back reaction on the geometry included semiclassically. The stress-energy tensor is calculated for null in-falling observers. It is shown that the evaporation proceeds smoothly and there are no instabilities of the outer or inner apparent horizon before the end point of evaporation.

A scalar field approach to the Jeans mass calculation is discussed. Considering a massive scalar field arbitrarily coupled to a gravitational background, the stress-energy tensor expectation values are computed in a coherent state. The density matrix is used to represent the expectation values. The energy density and pressure associated with the density perturbations are evaluated. Using these results, the exact expressions for the Jeans length and Jeans mass are evaluated.

We construct the Hamiltonian of the super-five-brane in terms of its physical degrees of freedom. It does not depend on the inverse of the induced metric. Consequently, some singular configurations are physically admissible, implying an interpretation of the theory as a multiparticle one. The symmetries of the theory are analyzed from the canonical point of view in terms of the first and second class constraints. In particular it is shown how the chiral sector may be canonically reduced to its physical degrees of freedom.

If spacetime possesses extra dimensions of size and curvature radii much larger than the Planck or string scales, the dynamics of these extra dimensions should be governed by classical general relativity. We argue that in general relativity it is nontrivial to obtain solutions where the extra dimensions are static and are dynamically stable to small perturbations. We also illustrate that intuition on equilibrium and stability built up from nongravitational physics can be highly misleading. For all static, homogeneous solutions satisfying the null energy condition, we show that the Ricci curvature of space must be non-negative in all directions. Much of our analysis focuses on a class of spacetime models where space consists of a product of homogeneous and isotropic geometries. A dimensional reduction of these models is performed, and their stability to perturbations that preserve the spatial symmetries is analyzed. We conclude that the only physically realistic examples of classically stabilized large extra dimensions are those in which the extra-dimensional manifold is positively curved.

We consider the behavior of a quintessence field during an inflationary epoch, in order to learn how inflation influences the likely initial conditions for quintessence. We use the stochastic inflation formalism to study quantum fluctuations induced in the quintessence field during the early stages of inflation, and conclude that these drive its mean to large values $\left(\gtrsim {0.1m}_{\mathrm{Pl}}\right).\mathrm{}$ Consequently we find that tracker behavior typically starts at low redshift, long after nucleosynthesis and most likely also after decoupling.

It is shown that the dynamics of cosmologies sourced by a mixture of perfect fluids and self-interacting scalar fields are described by the nonlinear, Ermakov-Pinney equation. The general solution of this equation can be expressed in terms of particular solutions to a related, linear differential equation. This characteristic is employed to derive exact cosmologies in the inflationary and quintessential scenarios. The relevance of the Ermakov-Pinney equation to the braneworld scenario is discussed.