36,317 research outputs found
Sex and recombination in the H\"otzel aging model
Why sex evolved and it prevails in nature remains one of the great puzzles of
evolution. Most biologists would explain that it promotes genetic variability,
however this explanation suffers from several difficulties. What advantages
might sex confer? The present communication aims at certain investigations
related to this question, in this way we introduce sexual recombination on the
H\"otzel model (with males and females) and we compare these results with those
from asexual reproduction without recombination.Comment: 10 pages, 6 figure
Charged Multiplicities at SPS and RHIC and consequences for suppression
Hadron multiplicities in nucleus--nucleus interactions are calculated in the
Dual Parton Model and its dependence on the number of collisions and the number
of participants is analyzed. Shadowing corrections are calculated as a function
of impact parameter and the multiplicity per participant as a funtion of
centrality is found to be in agreement with experiment at SPS and RHIC
energies. The obtained results are used to compute the suppression in
a comover approach.Comment: 4 pages, 4 postscript figures. Talk given at XXXVI Rencontres de
Moriond, Les Arcs, France, March 200
Canonical Formulation of Gravitational Teleparallelism in 2+1 Dimensions in Schwinger's Time Gauge
We consider the most general class of teleparallel gravitational {}{}theories
quadratic in the torsion tensor, in three space-time dimensions, and carry out
a detailed investigation of its Hamiltonian formulation in Schwinger's time
gauge. This general class is given by a family of three-parameter theories. A
consistent implementation of the Legendre transform reduces the original theory
to a one-parameter family of theories. By calculating Poisson brackets we show
explicitly that the constraints of the theory constitute a first-class set.
Therefore the resulting theory is well defined with regard to time evolution.
The structure of the Hamiltonian theory rules out the existence of the
Newtonian limit.Comment: 17 pages, Latex file, no figures; a numerical coefficient has been
corrected and a different result is achieve
Black Holes in 2+1 Teleparallel Theories of Gravity
We apply the Hamiltonian formulation of teleparallel theories of gravity in
2+1 dimensions to a circularly symmetric geometry. We find a family of
one-parameter black hole solutions. The BTZ solution fixes the unique free
parameter of the theory. The resulting field equations coincide with the
teleparallel equivalent of Einstein's three-dimensional equations. We calculate
the gravitational energy of the black holes by means of the simple expression
that arises in the Hamiltonian formulation and conclude that the resulting
value is identical to that calculated by means of the Brown-York method.Comment: 20 pages, Latex file, no figure
Phase transition in hierarchy model of Bonabeau et al
The model of Bonabeau explains the emergence of social hierarchies from the
memory of fights in an initially egalitarian society. Introducing a feedback
from the social inequality into the probability to win a fight, we find a sharp
transition between egalitarian society at low population density and
hierarchical society at high population density.Comment: 3 pages including two figs.; for Int. J. Mod. Phys.
Baryon and Antibaryon production at RHIC energies in the Dual Parton Model
We compute the mid-rapidity densities of pions, kaons, baryons and
antibaryons in -- collisions at = 130 GeV in the Dual Parton
Model supplemented with final state interactions, and we present a comparison
with available data.Comment: 4 pages, 2 figures. Talk given at XXXVII Rencontres de Moriond, Les
Arcs, France, March 200
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