19,531 research outputs found
Multipolar expansion of the electrostatic interaction between charged colloids at interfaces
The general form of the electrostatic potential around an arbitrarily charged
colloid at an interface between a dielectric and a screening phase (such as air
and water, respectively) is analyzed in terms of a multipole expansion. The
leading term is isotropic in the interfacial plane and varies with
where is the in--plane distance from the colloid. The electrostatic
interaction potential between two arbitrarily charged colloids is likewise
isotropic and , corresponding to the dipole--dipole interaction
first found for point charges at water interfaces. Anisotropic interaction
terms arise only for higher powers with .Comment: 6 pages, mathematical details adde
Comment on current correlators in QCD at finite temperature
We address some criticisms by Eletsky and Ioffe on the extension of QCD sum
rules to finite temperature. We argue that this extension is possible, provided
the Operator Product Expansion and QCD-hadron duality remain valid at non-zero
temperature. We discuss evidence in support of this from QCD, and from the
exactly solvable two- dimensional sigma model O(N) in the large N limit, and
the Schwinger model.Comment: 10 pages, LATEX file, UCT-TP-208/94, April 199
Electromagnetic nucleon form factors from QCD sum rules
The electromagnetic form factors of the nucleon, in the space-like region,
are determined from three-point function Finite Energy QCD Sum Rules. The QCD
calculation is performed to leading order in perturbation theory in the chiral
limit, and to leading order in the non-perturbative power corrections. The
results for the Dirac form factor, , are in very good agreement with
data for both the proton and the neutron, in the currently accessible
experimental region of momentum transfers. This is not the case, though, for
the Pauli form factor , which has a soft -dependence
proportional to the quark condensate .Comment: Replaced Version. An error has been corrected in the numerical
evaluation of the Pauli form factor. This changes the results for F_2(q^2),
as well as the conclusion
Finite Temperature QCD Sum Rules: a Review
The method of QCD sum rules at finite temperature is reviewed, with emphasis
on recent results. These include predictions for the survival of charmonium and
bottonium states, at and beyond the critical temperature for de-confinement, as
later confirmed by lattice QCD simulations. Also included are determinations in
the light-quark vector and axial-vector channels, allowing to analyse the
Weinberg sum rules, and predict the dimuon spectrum in heavy ion collisions in
the region of the rho-meson. Also in this sector, the determination of the
temperature behaviour of the up-down quark mass, together with the pion decay
constant, will be described. Finally, an extension of the QCD sum rule method
to incorporate finite baryon chemical potential is reviewed.Comment: Minor typos corrected. To be published in the review section of
Advances in High Energy Physic
Transport properties and structures of vortex matter in layered superconductors
In this paper we analyze the structure, phase transitions and some transport
properties of the vortex system when the external magnetic field lies parallel
to the planes in layered superconductors. We show that experimental results for
resistivity are qualitatively consistent with numerical simulations that
describe the melting of a commensurate rotated lattice. However for some
magnetic fields, the structure factor indicates the occurrence of smectic peaks
at an intermediate temperature regime.Comment: 8 pages, 8 eps figure
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