1,055 research outputs found
On the Poincare Gauge Theory of Gravitation
We present a compact, self-contained review of the conventional gauge
theoretical approach to gravitation based on the local Poincare group of
symmetry transformations. The covariant field equations, Bianchi identities and
conservation laws for angular momentum and energy-momentum are obtained.Comment: v2: minor changes, references added; 18 pages, no figure
The extended uncertainty principle inspires the R\'{e}nyi entropy
We use the extended uncertainty principle (EUP) in order to obtain the
R\'{e}nyi entropy for a black hole (BH). The result implies that the
non-extensivity parameter, appeared in the R\'{e}nyi entropy formalism, may be
evaluated from the considerations which lead to EUP. It is also shown that, for
excited BHs, the R\'{e}nyi entropy is a function of the BH principal quantum
number, i.e. the BH quantum excited state. Temperature and heat capacity of the
excited BHs are also investigated addressing two phases while only one of them
can be stable. At this situation, whereas entropy is vanished, temperature may
take a non-zero positive minimum value, depending on the value of the
non-extensivity parameter. The evaporation time of excited BH has also been
studied
Initiating the effective unification of black hole horizon area and entropy quantization with quasi-normal modes
Black hole (BH) quantization may be the key to unlocking a unifying theory of
quantum gravity (QG). Surmounting evidence in the field of BH research
continues to support a horizon (surface) area with a discrete and uniformly
spaced spectrum, but there is still no general agreement on the level spacing.
In this specialized and important BH case study, our objective is to report and
examine the pertinent groundbreaking work of the strictly thermal and
non-strictly thermal spectrum level spacing of the BH horizon area quantization
with included entropy calculations, which aims to tackle this gigantic problem.
In particular, this work exemplifies a series of imperative corrections that
eventually permits a BH's horizon area spectrum to be generalized from strictly
thermal to non-strictly thermal with entropy results, thereby capturing
multiple preceding developments by launching an effective unification between
them. Moreover, the identified results are significant because quasi-normal
modes (QNM) and "effective states" characterize the transitions between the
established levels of the non-strictly thermal spectrum.Comment: 23 pages, review paper. Final version to appear in Advances in High
Energy Physic
Tuning the stochastic background of gravitational waves using the WMAP data
The cosmological bound of the stochastic background of gravitational waves is
analyzed with the aid of the WMAP data, differently from lots of works in
literature, where the old COBE data were used. From our analysis, it will
result that the WMAP bounds on the energy spectrum and on the characteristic
amplitude of the stochastic background of gravitational waves are greater than
the COBE ones, but they are also far below frequencies of the earth-based
antennas band. At the end of this letter a lower bound for the integration time
of a potential detection with advanced LIGO is released and compared with the
previous one arising from the old COBE data. Even if the new lower bound is
minor than the previous one, it results very long, thus for a possible
detection we hope in the LISA interferometer and in a further growth in the
sensitivity of advanced projects.Comment: 9 pages, 2 figures, published in Modern Physics Letters A. arXiv
admin note: substantial text overlap with arXiv:0901.119
A non-geodesic motion in the R^-1 theory of gravity tuned with observations
In the general picture of high order theories of gravity, recently, the R^-1
theory has been analyzed in two different frameworks. In this letter a third
context is added, considering an explicit coupling between the R^-1 function of
the Ricci scalar and the matter Lagrangian. The result is a non-geodesic motion
of test particles which, in principle, could be connected with Dark Matter and
Pioneer anomaly problems.Comment: Accepted for Modern Physics Letters
The production of matter from curvature in a particular linearized high order theory of gravity and the longitudinal response function of interferometers
The strict analogy between scalar-tensor theories of gravity and high order
gravity is well known in literature. In this paper it is shown that, from a
particular high order gravity theory known in literature, it is possible to
produce, in the linearized approch, particles which can be seen like massive
scalar modes of gravitational waves and the response of interferometers to this
type of particles is analyzed. The presence of the mass generates a
longitudinal force in addition of the transverse one which is proper of the
massless gravitational waves and the response of an arm of an interferometer to
this longitudinal effect in the frame of a local observer is computed. This
longitudinal response function is directly connected with the function of the
Ricci scalar in the particular action of this high order theory. Important
conseguences from a theoretical point of view could arise from this approach,
because it opens to the possibility of using the signals seen from
interferometers to understand which is the correct theory of gravitation.Comment: Accepted for Journal of Cosmology and Astroparticle Physic
Some exact solutions of F(R) gravity with charged (a)dS black hole interpretation
In this paper we obtain topological static solutions of some kind of pure
gravity. The present solutions are two kind: first type is uncharged
solution which corresponds with the topological (a)dS Schwarzschild solution
and second type has electric charge and is equivalent to the
Einstein--conformally invariant Maxwell solution. In other word,
starting from pure gravity leads to (charged) Einstein- solutions
which we interpreted them as (charged) (a)dS black hole solutions of pure
gravity. Calculating the Ricci and Kreschmann scalars show that there is
a curvature singularity at . We should note that the Kreschmann scalar of
charged solutions goes to infinity as , but with a rate slower
than that of uncharged solutions.Comment: 21 pages, 4 figures, generalization to higher dimensions, references
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