9,058 research outputs found
Generalized Gross--Perry--Sorkin--Like Solitons
In this paper, we present a new solution for the effective theory of
Maxwell--Einstein--Dilaton, Low energy string and Kaluza--Klein theories, which
contains among other solutions the well known Kaluza--Klein monopole solution
of Gross--Perry--Sorkin as special case. We show also the magnetic and electric
dipole solutions contained in the general one.Comment: 10 latex pages, no figures. To appear in Class. Quant. Gravity
On the Space Time of a Galaxy
We present an exact solution of the averaged Einstein's field equations in
the presence of two real scalar fields and a component of dust with spherical
symmetry. We suggest that the space-time found provides the characteristics
required by a galactic model that could explain the supermassive central object
and the dark matter halo at once, since one of the fields constitutes a central
oscillaton surrounded by the dust and the other scalar field distributes far
from the coordinate center and can be interpreted as a halo. We show the
behavior of the rotation curves all along the background. Thus, the solution
could be a first approximation of a ``long exposition photograph'' of a galaxy.Comment: 8 pages REVTeX, 11 eps figure
Oscillatons revisited
In this paper, we study some interesting properties of a spherically
symmetric oscillating soliton star made of a real time-dependent scalar field
which is called an oscillaton. The known final configuration of an oscillaton
consists of a stationary stage in which the scalar field and the metric
coefficients oscillate in time if the scalar potential is quadratic. The
differential equations that arise in the simplest approximation, that of
coherent scalar oscillations, are presented for a quadratic scalar potential.
This allows us to take a closer look at the interesting properties of these
oscillating objects. The leading terms of the solutions considering a quartic
and a cosh scalar potentials are worked in the so called stationary limit
procedure. This procedure reveals the form in which oscillatons and boson stars
may be related and useful information about oscillatons is obtained from the
known results of boson stars. Oscillatons could compete with boson stars as
interesting astrophysical objects, since they would be predicted by scalar
field dark matter models.Comment: 10 pages REVTeX, 10 eps figures. Updated files to match version
published in Classical and Quantum Gravit
Behaviour Monitorization of a 13m High Gabions Wall
The paper refers a gabions retaining wall, located at Belas, about 30 km Northeast of Lisbon, in the North perimeter of an Organic Valorisation Central (Valorsul). After the wall completion some pathology occurred and it was detected that it had been partially executed with marl limestone blocks that loose mechanical resistance under rainy water. The wall was then demolished and rebuilt with adequate material. During the earth fill execution the wall was monitorized with a superficial topographical survey. The results obtained and the respective conclusions are referred
A Case of Soil Sliding in the Pathology of Retaining Structure
Sesimbra is a village located on the Portuguese West coastline 70 Km South of Lisbon. It is a site of high cliffs, overlooking the sea, mainly formed by clays. The rainwater that penetrates the soil through permeable layers originates the clays sliding. Recent construction site in the area started with the execution of a retaining wall with counterforts. Some time later after a long rainy period the soil sliding created a high earth pressure on the retaining wall that originated the separation between the wall and its counterforts. The paper describes the pathology and its repair
Quintessence and Scalar Dark Matter in the Universe
Continuing with previous works, we present a cosmological model in which dark
matter and dark energy are modeled by scalar fields and ,
respectively, endowed with the scalar potentials and . This model contains 95% of
scalar field. We obtain that the scalar dark matter mass is The solution obtained allows us to recover the success of the
standard CDM. The implications on the formation of structure are reviewed. We
obtain that the minimal cutoff radio for this model is Comment: 4 pages REVTeX, 3 eps color figures. Minor changes and references
updated. To appear in Classical and Quantum Gravity as a Letter to the
Editor. More information at http://www.fis.cinvestav.mx/~siddh/PHI
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