4,619 research outputs found
Asymptotic behaviour of gossip processes and small world networks
Both small world models of random networks with occasional long range
connections and gossip processes with occasional long range transmission of
information have similar characteristic behaviour. The long range elements
appreciably reduce the effective distances, measured in space or in time,
between pairs of typical points. In this paper, we show that their common
behaviour can be interpreted as a product of the locally branching nature of
the models. In particular, it is shown that both typical distances between
points and the proportion of space that can be reached within a given distance
or time can be approximated by formulae involving the limit random variable of
the branching process.Comment: 30 page
The shortest distance in random multi-type intersection graphs
Using an associated branching process as the basis of our approximation, we
show that typical inter-point distances in a multitype random intersection
graph have a defective distribution, which is well described by a mixture of
translated and scaled Gumbel distributions, the missing mass corresponding to
the event that the vertices are not in the same component of the graph.Comment: 32 page
Isolation and cultivation of Lyme disease spirochetes.
The successful isolation and cultivation of Lyme disease spirochetes traces its lineage to early attempts at cultivating relapsing fever borreliae. Observations on the growth of Lyme disease spirochetes under different in vitro conditions may yield important clues to both the metabolic characteristics of these newly discovered organisms and the pathogenesis of Lyme disease
Immunochemical analysis of Lyme disease spirochetes.
Sera from patients with Lyme disease (LD) originating in the United States and Europe were examined by western blot analysis for antibodies to LD spirochete components. Whereas some components reacted with antibodies from the majority of patients, other components, notably an abundant cellular protein with an apparent molecular weight of 34,000 were less commonly bound. This latter proteinaceous component was in a region of the polyacrylamide gel electrophoresis profile which demonstrated variability between different LD spirochete isolates. Thus, there may be more than one serotype of LD spirochete, and the 34,000-range proteins may be a basis for such a distinction
Finite density QCD with heavy quarks
In the large fermion mass limit of QCD at finite density the structure of the
partition function greatly simplifies and can be studied analytically. We show
that, contrary to general wisdom, the phase of the Dirac determinant is
relevant only at finite temperature and can be neglected for zero temperature
fields.Comment: LATTICE98(hightemp), 3 pages, 3 figure
Frustration in Finite Density QCD
We present a detailed analysis of the QCD partition function in the Grand
Canonical formalism. Using the fugacity expansion we find evidence for
numerical instabilities in the standard evaluation of its coefficients. We
discuss the origin of this problem and propose an issue to it. The correct
analysis shows no evidence for a discontinuity in the baryonic density in the
strong coupling limit. The moderate optimism that was inspired by the Grand
Canonical Partition Function calculations in the last years has to be
considered ill-founded.Comment: 9 pages, 6 Postscript figures; some comments adde
Phase transition(s) in finite density QCD
The Grand Canonical formalism is generally used in numerical simulations of
finite density QCD since it allows free mobility in the chemical potential
. We show that special care has to be used in extracting numerical results
to avoid dramatic rounding effects and spurious transition signals. If we
analyze data correctly, with reasonable statistics, no signal of first order
phase transition is present and results using the Glasgow prescription are
practically coincident with the ones obtained using the modulus of the
fermionic determinant.Comment: 6 pages, 5 ps figs. To appear in Proceedings of "QCD at Finite Baryon
Density" workshop, Bielefeld, 27-30 April 199
Three and Two Colours Finite Density QCD at Strong Coupling: A New Look
Simulations in finite density, beta=0 lattice QCD by means of the
Monomer-Dimer-Polymer algorithm show a signal of first order transition at
finite temporal size. This behaviour agrees with predictions of the mean field
approximation, but is difficult to reconcile with infinite mass analytical
solution. The MDP simulations are considered in detail and severe convergence
problems are found for the SU(3) gauge group, in a wide region of chemical
potential. Simulations of SU(2) model show discrepancies with MDP results as
well.Comment: 18 pages, 9 figures, to appear in Nucl. Phys.
Rigorous arguments against current wisdoms in finite density QCD
QCD at finite chemical potential is analytically investigated in the region
of large bare fermion masses. We show that, contrary to the general wisdom, the
phase of the fermion determinant is irrelevant at zero temperature. However if
the system is put at finite temperature, the contribution of the phase is
finite. We also discuss on the quenched approximation and suggest that the
origin of the failure of this approximation in finite density QCD could relay
on the fundamental role that Pauli exclusion principle plays in this case.Comment: 16 pages, 5 figure
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