1,954 research outputs found
Casimir-Polder interaction between an atom and a conducting wall in cosmic string spacetime
The Casimir-Polder interaction potential is evaluated for a polarizable
microparticle and a conducting wall in the geometry of a cosmic string
perpendicular to the wall. The general case of the anisotropic polarizability
tensor for the microparticle is considered. The corresponding force is a
function of the wall-microparticle and cosmic string-microparticle distances.
Depending on the orientation of the polarizability tensor principal axes the
force can be either attractive or repulsive. The asymptotic behavior of the
Casimir-Polder potential is investigated at large and small separations
compared to the wavelength of the dominant atomic transitions. We show that the
conical defect may be used to control the strength and the sign of the
Casimir-Polder force.Comment: 17 pages, 3 figure
Self-Forces on Electric and Magnetic Linear Sources in the Space-Time of a Cosmic String
In this paper we calculate the magnetic and electric self-forces, induced by
the conical structure of a cosmic string space-time, on a long straight wire
which presents either a constant current or a linear charge density. We also
show how these self-forces are related by a Lorentz tranformation and, in this
way, explain what two different inertial observers detect in their respective
frames.Comment: 10 pages, LaTeX, to be published in Phys. Rev. D
Relativistic Quantum Scattering on a Cone
We study the relativistic quantum mechanical scattering of a bosonic particle
by an infinite straight cosmic string, considering the non-minimal coupling
between the bosonic field and the scalar curvature. In this case, an effective
two-dimensional delta-function interaction takes place besides the usual
topological scattering and a renormalization procedure is necessary in order to
treat the problem that appears in connection with the delta-function.Comment: 22 pages, LATEX fil
Desenvolvimento inicial do clone BRS 275 de cajueiro sob irrigação com diferentes nĂveis salinos.
Desenvolvimento inicial do clone BRS 275 de cajueiro sob irrigação com diferentes nĂveis salinos.
Black hole formation in bidimensional dilaton gravity coupled to scalar matter systems
This work deals with the formation of black hole in bidimensional dilaton
gravity coupled to scalar matter fields. We investigate two scalar matter
systems, one described by a sixth power potential and the other defined with
two scalar fields containing up to the fourth power in the fields. The
topological solutions that appear in these cases allow the formation of black
holes in the corresponding dilaton gravity models.Comment: Latex, 9 pages. Published in Mod. Phys. Lett. A14 (1999) 268
A DIESEL ENGINE CONVERTED INTO OTTO CYCLE ENGINE: THE INFLUENCE OF THE SPARK ADVANCE ON ITS PERFORMANCE AND ON NOx EMISSIONS
This paper analyzes the performance of a diesel engine converted into an Otto cycle engine and its Nitrogen dioxide emissions in terms of the spark advance variation. The tests were conducted on a Perkins diesel engine 1104C - 44TAG turbocharged, whose compression ratio was reduced to 9.33:1. After conversion the engine started operating with liquefied petroleum gas (LPG) and running just with stoichiometric mixtures. The tests have been limited to 10 to 40 kW, always at 1800 rpm. During the experiments the ignition advance angle ranged from 5º up to 27º (BTDC), using the increment of 5°, whenever possible. Particularly at 40 kW, the range of the ignition advance was 15º to 20º. The results showed a significant influence of the spark advance angle on the fuel consumption, on the temperature and on the NOx emissions, as well as on the magnitude of the generated power
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