39,187 research outputs found
From propagators to glueballs in the Gribov-Zwanziger framework
Over the last years, lattice calculations in pure Yang-Mills gauge theory
seem to have come more or less to a consensus. The ghost propagator is not
enhanced and the gluon propagator is positivity violating, infrared suppressed
and non-vanishing at zero momentum. From an analytical point of view, several
groups are agreeing with these results. Among them, the refined
Gribov-Zwanziger (RGZ) framework also accommodates for these results. The
question which rises next is, if our models hold the right form for the
propagators, how to extract information on the real physical observables, i.e.
the glueballs? How do the operators which represent glueballs look like? We
review the current status of this matter within the RGZ framework.Comment: 3 pages, Conference contribution for Confinement IX, Madrid 2010
(30/08-03/09), to appear in American Institute of Physics (AIP
Degree-dependent intervertex separation in complex networks
We study the mean length of the shortest paths between a vertex of
degree and other vertices in growing networks, where correlations are
essential. In a number of deterministic scale-free networks we observe a
power-law correction to a logarithmic dependence, in a wide range of network
sizes. Here is the number of vertices in the network, is the
degree distribution exponent, and the coefficients and depend on a
network. We compare this law with a corresponding dependence obtained
for random scale-free networks growing through the preferential attachment
mechanism. In stochastic and deterministic growing trees with an exponential
degree distribution, we observe a linear dependence on degree, . We compare our findings for growing networks with those for
uncorrelated graphs.Comment: 8 pages, 3 figure
Emergentism and musicology: an alternative perspective to the understanding of dissonance.
In this paper we develop an approach to musicology within the
discussion of emergentism. First of all, we claim that some theories of
musicology could be insufficient in describing and explaining musical
phenomena when emergent properties are not taken into account. Actually,
musicology usually considers just syntactical elements, structures and
processes and puts only a little emphasis, if any, over perceptual aspects of
human hearing. On the other hand, recent research efforts are currently being
directed towards an understanding of the emergent properties of auditory
perception, especially in fields such as cognitive science. Such research leads
to other views concerning old issues in musicology and could create a fruitful
approach, filling the gap between musicology and auditory perception
Wyman's solution, self-similarity and critical behaviour
We show that the Wyman's solution may be obtained from the four-dimensional
Einstein's equations for a spherically symmetric, minimally coupled, massless
scalar field by using the continuous self-similarity of those equations. The
Wyman's solution depends on two parameters, the mass and the scalar charge
. If one fixes to a positive value, say , and let
take values along the real line we show that this solution exhibits critical
behaviour. For the space-times have eternal naked singularities,
for one has a Schwarzschild black hole of mass and finally
for one has eternal bouncing solutions.Comment: Revtex version, 15pages, 6 figure
An Interesting Fitting of Quark Masses
In this note we show an empirical formula of quark masses, which is found by
implementing a least squares fit. In this formula the measured QCD coupling is
almost a "best fitting coupling".Comment: 5 pages, 2 figure
Collapse of Primordial Clouds
We present here studies of collapse of purely baryonic Population III objects
with masses ranging from to . A spherical Lagrangian
hydrodynamic code has been written to study the formation and evolution of the
primordial clouds, from the beginning of the recombination era () until the redshift when the collapse occurs. All the relevant processes
are included in the calculations, as well as, the expansion of the Universe. As
initial condition we take different values for the Hubble constant and for the
baryonic density parameter (considering however a purely baryonic Universe), as
well as different density perturbation spectra, in order to see their influence
on the behavior of the Population III objects evolution. We find, for example,
that the first mass that collapses is for ,
and with the mass scale . For
we obtain for the first
mass that collapses. The cooling-heating and photon drag processes have a key
role in the collapse of the clouds and in their thermal history. Our results
show, for example, that when we disregard the Compton cooling-heating, the
collapse of the objects with masses occurs earlier. On
the other hand, disregarding the photon drag process, the collapse occurs at a
higher redshift.Comment: 10 pages, MN plain TeX macros v1.6 file, 9 PS figures. Also available
at http://www.iagusp.usp.br/~oswaldo (click "OPTIONS" and then "ARTICLES").
MNRAS in pres
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