1,702,764 research outputs found
Chiral SU(3) Symmetry and Strangeness
In this talk we review recent progress on the systematic evaluation of the
kaon and antikaon spectral functions in dense nuclear matter based on a chiral
SU(3) description of the low-energy pion-, kaon- and antikaon-nucleon
scattering data.Comment: 9 pages, 4 figures, invited talk given by M.F.M.L. at the SQM2001
conferenc
Genera of curves on a very general surface in
In this paper we consider the question of determining the geometric genera of
irreducible curves lying on a very general surface of degree at least 5
in (the cases are well known).
We introduce the set of all non-negative integers which are not
realized as geometric genera of irreducible curves on . We prove that
is finite and, in particular, that . The set
is the union of finitely many disjoint and separated integer
intervals. The first of them, according to a theorem of Xu, is . We show that the next one is for all .Comment: 16 page
Spindensities in Pseudo-classical kinetic theory
In this paper the classical limit of relativistic transport theories for spin
1/2 fermions is examined through a comparison with the classical kinetic theory
derived from N=1 supersymmetric classical mechanics. The conclusion is that in
the classical limit spindensities, i.e. the axial-vector contribution to the
relativistic Wigner-function, vanishes and dipole-densities, i.e. the
spin-tensor contributions to the relativistic Wigner function, may survive.Comment: Latex 22 pages, 63628 bytes. No figure
Elastic collapse in disordered isostatic networks
Isostatic networks are minimally rigid and therefore have, generically,
nonzero elastic moduli. Regular isostatic networks have finite moduli in the
limit of large sizes. However, numerical simulations show that all elastic
moduli of geometrically disordered isostatic networks go to zero with system
size. This holds true for positional as well as for topological disorder. In
most cases, elastic moduli decrease as inverse power-laws of system size. On
directed isostatic networks, however, of which the square and cubic lattices
are particular cases, the decrease of the moduli is exponential with size. For
these, the observed elastic weakening can be quantitatively described in terms
of the multiplicative growth of stresses with system size, giving rise to bulk
and shear moduli of order exp{-bL}. The case of sphere packings, which only
accept compressive contact forces, is considered separately. It is argued that
these have a finite bulk modulus because of specific correlations in contact
disorder, introduced by the constraint of compressivity. We discuss why their
shear modulus, nevertheless, is again zero for large sizes. A quantitative
model is proposed that describes the numerically measured shear modulus, both
as a function of the loading angle and system size. In all cases, if a density
p>0 of overconstraints is present, as when a packing is deformed by
compression, or when a glass is outside its isostatic composition window, all
asymptotic moduli become finite. For square networks with periodic boundary
conditions, these are of order sqrt{p}. For directed networks, elastic moduli
are of order exp{-c/p}, indicating the existence of an "isostatic length scale"
of order 1/p.Comment: 6 pages, 6 figues, to appear in Europhysics Letter
Generalization of the matrix product ansatz for integrable chains
We present a general formulation of the matrix product ansatz for exactly
integrable chains on periodic lattices. This new formulation extends the matrix
product ansatz present on our previous articles (F. C. Alcaraz and M. J. Lazo
J. Phys. A: Math. Gen. 37 (2004) L1-L7 and J. Phys. A: Math. Gen. 37 (2004)
4149-4182.)Comment: 5 pages. to appear in J. Phys. A: Math. Ge
Review on possible gravitational anomalies
This is an updated introductory review of 2 possible gravitational anomalies
that has attracted part of the Scientific community: the Allais effect that
occur during solar eclipses, and the Pioneer 10 spacecraft anomaly,
experimented also by Pioneer 11 and Ulysses spacecrafts. It seems that, to
date, no satisfactory conventional explanation exist to these phenomena, and
this suggests that possible new physics will be needed to account for them. The
main purpose of this review is to announce 3 other new measurements that will
be carried on during the 2005 solar eclipses in Panama and Colombia (Apr. 8)
and in Portugal (Oct.15).Comment: Published in 'Journal of Physics: Conferences Series of the American
Institute of Physics'. Contribution for the VI Mexican School on Gravitation
and Mathematical Physics "Approaches to Quantum Gravity" (Playa del Carmen,
Quintana Roo, Mexico, Nov. 21-27, 2004). Updates to this information will be
posted in http://www.lsc-group.phys.uwm.edu/~xavier.amador/anomalies.htm
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