44,420 research outputs found
Contact process on a Voronoi triangulation
We study the continuous absorbing-state phase transition in the contact
process on the Voronoi-Delaunay lattice. The Voronoi construction is a natural
way to introduce quenched coordination disorder in lattice models. We simulate
the disordered system using the quasistationary simulation method and determine
its critical exponents and moment ratios. Our results suggest that the critical
behavior of the disordered system is unchanged with respect to that on a
regular lattice, i.e., that of directed percolation
Unintegrated parton distributions in nuclei
We study how unintegrated parton distributions in nuclei can be calculated
from the corresponding integrated partons using the EPS09 parametrization. The
role of nuclear effects is presented in terms of the ratio
for both large and small domains.Comment: 9 pages, 4 figure
Newtonian View of General Relativistic Stars
Although general relativistic cosmological solutions, even in the presence of
pressure, can be mimicked by using neo-Newtonian hydrodynamics, it is not clear
whether there exists the same Newtonian correspondence for spherical static
configurations. General relativity solutions for stars are known as the
Tolman-Oppenheimer-Volkoff (TOV) equations. On the other hand, the Newtonian
description does not take into account the total pressure effects and therefore
can not be used in strong field regimes. We discuss how to incorporate pressure
in the stellar equilibrium equations within the neo-Newtonian framework. We
compare the Newtonian, neo-Newtonian and the full relativistic theory by
solving the equilibrium equations for both three approaches and calculating the
mass-radius diagrams for some simple neutron stars equation of state.Comment: 6 pages, 3 figures. v2 matches accepted version (EPJC
Operational Classification and Quantification of Multipartite Entangled States
We formalize and extend an operational multipartite entanglement measure
introduced by T. R. Oliveira, G. Rigolin, and M. C. de Oliveira, Phys. Rev. A
73, 010305(R) (2006), through the generalization of global entanglement (GE)
[D. A. Meyer and N. R. Wallach, J. Math. Phys. 43, 4273 (2002)]. Contrarily to
GE the main feature of this measure lies in the fact that we study the mean
linear entropy of all possible partitions of a multipartite system. This allows
the construction of an operational multipartite entanglement measure which is
able to distinguish among different multipartite entangled states that GE
failed to discriminate. Furthermore, it is also maximum at the critical point
of the Ising chain in a transverse magnetic field, being thus able to detect a
quantum phase transition.Comment: 14 pages, RevTex4, published versio
The Conditions for Star Formation at Low Metallicity: Results from the LMC
We present our recent work on the conditions under which star formation
occurs in a metal-poor environment, the Large Magellanic Cloud ([Fe/H] ~ -0.4).
Water masers are used as beacons of the current star formation in HII regions.
Comparing their location with the dust morphology imaged with the Spitzer Space
Telescope, and additional Halpha imaging and groundbased near-infrared
observations, we conclude that the LMC environment seems favourable to
sequential star formation triggered by massive star feedback (Oliveira et al.
2006). Good examples of this are 30 Doradus and N 113. There are also HII
regions, such as N 105A, where feedback may not be responsible for the current
star formation although the nature of one young stellar object (YSO) suggests
that feedback may soon start making an impact. The chemistry in one YSO hints
at a stronger influence from irradiation effects in a metal-poor environment
where shielding by dust is suppressed (van Loon 2005)Comment: in "Triggered Star Formation in a Turbulent ISM", IAU symposium,
poster contribution; a better quality version of this manuscript can be found
at http://www.astro.keele.ac.uk/~jacco/papers/proc.ps a full version of the
poster can be found at
http://www.astro.keele.ac.uk/~jacco/papers/IAUS237_LMC_2006.pd
Comparação da composição florĂstica de capoeiras em trĂŞs faixas de idade no municĂpio de Bragança-PA.
Chaotic Interaction of Langmuir Solitons and Long Wavelength Radiation
In this work we analyze the interaction of isolated solitary structures and
ion-acoustic radiation. If the radiation amplitude is small solitary structures
persists, but when the amplitude grows energy transfer towards small spatial
scales occurs. We show that transfer is particularly fast when a fixed point of
a low dimensional model is destroyed.Comment: LaTex + 4 eps file
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