5,868 research outputs found
Saturation and shadowing in high-energy proton-nucleus dilepton production
We discuss the inclusive dilepton cross section for proton (quark)-nucleus
collisions at high energies in the very forward rapidity region. Starting from
the calculation in the quasi-classical approximation, we include low-x
evolution effects in the nucleus and predict leading twist shadowing together
with anomalous scaling behaviour.Comment: 32 pages, LaTex, 6 figures, a few modifications of the tex
Renormalization and Essential Singularity
In usual dimensional counting, momentum has dimension one. But a function
f(x), when differentiated n times, does not always behave like one with its
power smaller by n. This inevitable uncertainty may be essential in general
theory of renormalization, including quantum gravity. As an example, we
classify possible singularities of a potential for the Schr\"{o}dinger
equation, assuming that the potential V has at least one class eigen
function. The result crucially depends on the analytic property of the eigen
function near its 0 point.Comment: 12 pages, no figures, PTPTeX with amsfonts. 2 pages added for detail
Multiple State Representation Scheme for Organic Bulk Heterojunction Solar Cells: A Novel Analysis Perspective
The physics of organic bulk heterojunction solar cells is studied within a
six state model, which is used to analyze the factors that affect
current-voltage characteristics, power-voltage properties and efficiency, and
their dependence on nonradiative losses, reorganization of the nuclear
environment, and environmental polarization. Both environmental reorganization
and polarity is explicitly taken into account by incorporating Marcus
heterogeneous and homogeneous electron transfer rates. The environmental
polarity is found to have a nonnegligible influence both on the stationary
current and on the overall solar cell performance. For our organic bulk
heterojunction solar cell operating under steady-state open circuit condition,
we also find that the open circuit voltage logarithmically decreases with
increasing nonradiative electron-hole recombination processes.Comment: 6 pages, 4 figure
Bosonization solution of the Falicov-Kimball model
We use a novel approach to analyze the one dimensional spinless
Falicov-Kimball model. We derive a simple effective model for the occupation of
the localized orbitals which clearly reveals the origin of the known ordering.
Our study is extended to a quantum model with hybridization between the
localized and itinerant states; we find a crossover between the well-known
weak- and strong-coupling behaviour. The existence of electronic polarons at
intermediate coupling is confirmed. A phase diagram is presented and discussed
in detail.Comment: RevTex, 10 pages, 1 figur
Does parton saturation at high density explain hadron multiplicities at LHC?
An addendum to our previous papers in Phys. Lett. B539 (2002) 46 and Phys.
Lett. B502 (2001) 51, contributed to the CERN meeting "First data from the LHC
heavy ion run", March 4, 2011Comment: 6 pages, contribution to the CERN meeting "First data from the LHC
heavy ion run", March 4, 201
Feasibility study for a secondary Na/S battery
The feasibility of a moderate temperature Na battery was studied. This battery is to operate at a temperature in the range of 100-150 C. Two kinds of cathode were investigated: (1) a soluble S cathode consisting of a solution of Na2Sn in an organic solvent and (2) an insoluble S cathode consisting of a transition metal dichalcogenide in contact with a Na(+)ion conducting electrolyte. Four amide solvents, dimethyl acetamide, diethyl acetamide, N-methyl acetamide and acetamide, were investigated as possible solvents for the soluble S cathode. Results of stability and electrochemical studies using these solvents are presented. The dialkyl substituted amides were found to be superior. Although the alcohol 1,3-cyclohexanediol was found to be stable in the presence of Na2Sn at 130 C, its Na2Sn solutions did not appear to have suitable electrochemical properties
Quenching of hadron spectra in media
We determine how the yield of large transverse momentum hadrons is modified
due to induced gluon radiation off a hard parton traversing a QCD medium. The
quenching factor is formally a collinear- and infrared-safe quantity and can be
treated perturbatively. In spite of that, in the region of practical
interest, its value turns out to be extremely sensitive to large distances and
can be used to unravel the properties of dense quark-gluon final states
produced in heavy ion collisions. We also find that the standard modelling of
quenching by shifting in the hard parton cross section by the mean
energy loss is inadequate.Comment: 20 pp, 5 eps figure
How many electrons are needed to flip a local spin?
Considering the spin of a local magnetic atom as a quantum mechanical
operator, we illustrate the dynamics of a local spin interacting with a
ballistic electron represented by a wave packet. This approach improves the
semi-classical approximation and provides a complete quantum mechanical
understanding for spin transfer phenomena. Sending spin-polarized electrons
towards a local magnetic atom one after another, we estimate the minimum number
of electrons needed to flip a local spin.Comment: 3 figure
Hydrogen production by photoelectrolytic decomposition of H2O using solar energy
Photoelectrochemical systems for the efficient decomposition of water are discussed. Semiconducting d band oxides which would yield the combination of stability, low electron affinity, and moderate band gap essential for an efficient photoanode are sought. The materials PdO and Fe-xRhxO3 appear most likely. Oxygen evolution yields may also be improved by mediation of high energy oxidizing agents, such as CO3(-). Examination of several p type semiconductors as photocathodes revealed remarkable stability for p-GaAs, and also indicated p-CdTe as a stable H2 photoelectrode. Several potentially economical schemes for photoelectrochemical decomposition of water were examined, including photoelectrochemical diodes and two stage, four photon processes
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