24,992 research outputs found
Recovery of potable water from human wastes in below-G conditions Patent
Potable water reclamation from human wastes in zero-G environmen
Water reclamation and conservation in a closed ecological system
Water recovery and conservation in closed ecological systems for manned space fligh
Nonlinearity of vacuum reggeons and exclusive diffractive production of vector mesons at HERA
The processes of exclusive photo- and electroproduction of vector mesons
(770), (1020) and (3096) at collision energies and transferred momenta squared are considered in
the framework of a phenomenological Regge-eikonal scheme with nonlinear Regge
trajectories in which their QCD asymptotic behavior is taken into account
explicitly. By comparison of available experimental data from ZEUS and H1
Collaborations with the model predictions it is demonstrated that corresponding
angular distributions and integrated cross-sections in the above-mentioned
kinematical range can be quantitatively described with use of two -even
vacuum Regge trajectories. These are the "soft" pomeron dominating the high
energy reactions without a hard scale and the "hard" pomeron giving an
essential contribution to photo- and electroproduction of heavy vector mesons
and deeply virtual electroproduction of light vector mesons.Comment: 25 pages, 12 figure
Gravireggeons and transplanckian scattering in models with one extra dimension
The inelastic scattering of the brane fields induced by -channel
gravireggeons exchanges in the RS model with a small curvature is
considered, and the imaginary part of the eikonal is analytically calculated.
It is demonstrated that the results can be obtained from the corresponding
formulae previously derived in the ADD model with one extra dimension of the
size by formal replacement . The inelastic
cross section for the scattering of ultra-high neutrino off the nucleon is
numerically estimated for the case TeV, where
is a reduced Planck scale in five warped dimensions.Comment: 17 pages, LaTeX2e, 3 eps figure
A modified triplet-wave expansion method applied to the alternating Heisenberg chain
An alternative triplet-wave expansion formalism for dimerized spin systems is
presented, a modification of the 'bond operator' formalism of Sachdev and
Bhatt. Projection operators are used to confine the system to the physical
subspace, rather than constraint equations. The method is illustrated for the
case of the alternating Heisenberg chain, and comparisons are made with the
results of dimer series expansions and exact diagonalization. Some discussion
is included of the phenomenon of 'quasiparticle breakdown', as it applies to
the two-triplon bound states in this model.Comment: 16 pages, 12 figure
Collins Asymmetry at Hadron Colliders
We study the Collins effect in the azimuthal asymmetric distribution of
hadrons inside a high energy jet in the single transverse polarized proton
proton scattering. From the detailed analysis of one-gluon and two-gluon
exchange diagrams contributions, the Collins function is found the same as that
in the semi-inclusive deep inelastic scattering and e^+e^- annihilations. The
eikonal propagators in these diagrams do not contribute to the phase needed for
the Collins-type single spin asymmetry, and the universality is derived as a
result of the Ward identity. We argue that this conclusion depends on the
momentum flow of the exchanged gluon and the kinematic constraints in the
fragmentation process, and is generic and model-independent.Comment: 23 pages, 6 figure
Double transverse spin asymmetries in vector boson production
We investigate a helicity non-flip double transverse spin asymmetry in vector
boson production in hadron-hadron scattering, which was first considered by
Ralston and Soper at the tree level. It does not involve transversity functions
and in principle also arises in W-boson production for which we present the
expressions. The asymmetry requires observing the transverse momentum of the
vector boson, but it is not suppressed by explicit inverse powers of a large
energy scale. However, as we will show, inclusion of Sudakov factors causes
suppression of the asymmetry, which increases with energy. Moreover, the
asymmetry is shown to be approximately proportional to x_1 g_1(x_1) x_2 \bar
g_1(x_2), which gives rise to additional suppression at small values of the
light cone momentum fractions. This implies that it is negligible for Z or W
production and is mainly of interest for \gamma^* at low energies. We also
compare the asymmetry with other types of double transverse spin asymmetries
and discuss how to disentangle them.Comment: 12 pages, Revtex, 2 Postscript figures, uses aps.sty, epsf.sty;
figures replaced, a few minor other correction
Single spin asymmetries in DIS
We consider possible mechanisms for single spin asymmetries in inclusive Deep
Inelastic Scattering (DIS) processes with unpolarized leptons and transversely
polarized nucleons. Tests for the effects of non-zero \bfk_\perp, for the
properties of spin dependent quark fragmentations and for quark helicity
conservation are suggested.Comment: 5 pages, LaTeX, no figures. Revised version, to be published in Phys.
Rev. D. Some equations and statements added to clarify text and notation
Adapting Real Quantifier Elimination Methods for Conflict Set Computation
The satisfiability problem in real closed fields is decidable. In the context
of satisfiability modulo theories, the problem restricted to conjunctive sets
of literals, that is, sets of polynomial constraints, is of particular
importance. One of the central problems is the computation of good explanations
of the unsatisfiability of such sets, i.e.\ obtaining a small subset of the
input constraints whose conjunction is already unsatisfiable. We adapt two
commonly used real quantifier elimination methods, cylindrical algebraic
decomposition and virtual substitution, to provide such conflict sets and
demonstrate the performance of our method in practice
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