19 research outputs found
New torsion black hole solutions in Poincar\'e gauge theory
We derive a new exact static and spherically symmetric vacuum solution in the
framework of the Poincar\'e gauge field theory with dynamical massless torsion.
This theory is built in such a form that allows to recover General Relativity
when the first Bianchi identity of the model is fulfilled by the total
curvature. The solution shows a Reissner-Nordstr\"om type geometry with a
Coulomb-like curvature provided by the torsion field. It is also shown the
existence of a generalized Reissner-Nordstr\"om-de Sitter solution when
additional electromagnetic fields and/or a cosmological constant are coupled to
gravity.Comment: 14 pages, 0 figures, minor changes, references adde
Extended Reissner-Nordstr\"om solutions sourced by dynamical torsion
We find a new exact vacuum solution in the framework of the Poincar\'e Gauge
field theory with massive torsion. In this model, torsion operates as an
independent field and introduces corrections to the vacuum structure present in
General Relativity. The new static and spherically symmetric configuration
shows a Reissner-Nordstr\"om-like geometry characterized by a spin charge. It
extends the known massless torsion solution to the massive case. The
corresponding Reissner-Nordstr\"om-de Sitter solution is also compatible with a
cosmological constant and additional U(1) gauge fields.Comment: 12 pages, 0 figures, minor changes, references adde
Einstein-Yang-Mills-Lorentz black holes
Different black hole solutions of the coupled Einstein-Yang-Mills equations
have been well known for a long time. They have attracted much attention from
mathematicians and physicists since their discovery. In this work, we analyze
black holes associated with the gauge Lorentz group. In particular, we study
solutions which identify the gauge connection with the spin connection. This
ansatz allows one to find exact solutions to the complete system of equations.
By using this procedure, we show the equivalence between the Yang-Mills-Lorentz
model in curved space-time and a particular set of extended gravitational
theories.Comment: 10 pages, 0 figures, minor changes, references added. It matches the
version published in Eur. Phys. J.
Correspondence between Einstein-Yang-Mills-Lorentz systems and dynamical torsion models
In the framework of Einstein-Yang-Mills theories, we study the gauge Lorentz
group and establish a particular correspondence between this case and a certain
class of theories with torsion within Riemann-Cartan space-times. This relation
is specially useful in order to simplify the problem of finding exact solutions
to the Einstein-Yang-Mills equations. The applicability of the method is
divided into two approaches: one associated with the Lorentz group SO(1,n-1) of
the space-time rotations and another one with its subgroup SO(n-2). Solutions
for both cases are presented by the explicit use of this correspondence and,
interestingly, for the last one by imposing on our ansatz the same kind of
rotation and reflection symmetry properties as for a nonvanishing space-time
torsion. Although these solutions were found in previous literature by a
different approach, our method provides an alternative way to obtain them and
it may be used in future research to find other exact solutions within this
theory.Comment: 10 pages, 0 figures, minor changes, references added. It matches the
version published in Phys. Rev.
Observational Constraints in Metric-Affine Gravity
We derive the main classical gravitational tests for a recently found vacuum
solution with spin and dilation charges in the framework of Metric-Affine gauge
theory of gravity. Using the results of the perihelion precession of the star
S2 by the GRAVITY collaboration and the gravitational redshift of Sirius B
white dwarf we constrain the corrections provided by the torsion and
nonmetricity fields for these effects.Comment: 16 page
Stability in quadratic torsion theories
We revisit the definition and some of the characteristics of quadratic
theories of gravity with torsion. We start from the most general Lagrangian
density quadratic in the curvature and torsion tensors. By assuming that
General Relativity should be recovered when torsion vanishes and investigating
the behaviour of the vector and pseudovector torsion fields in the weak-gravity
regime, we present a set of necessary conditions for the stability of these
theories. Moreover, we explicitly obtain the gravitational field equations
using the Palatini variational principle with the metricity condition
implemented via a Lagrange multiplier
Black hole solutions in scalar-tensor symmetric teleparallel gravity
Symmetric teleparallel gravity is constructed with a nonzero nonmetricity
tensor while both torsion and curvature are vanishing. In this framework, we
find exact scalarised spherically symmetric static solutions in scalar-tensor
theories built with a nonminimal coupling between the nonmetricity scalar and a
scalar field. It turns out that the Bocharova-Bronnikov-Melnikov-Bekenstein
solution has a symmetric teleparallel analogue (in addition to the recently
found metric teleparallel analogue), while some other of these solutions
describe scalarised black hole configurations that are not known in the
Riemannian or metric teleparallel scalar-tensor case. To aid the analysis we
also derive no-hair theorems for the theory. Since the symmetric teleparallel
scalar-tensor models also include gravity, we shortly discuss this case
and further prove a theorem which says that by imposing that the metric
functions are the reciprocal of each other (), the
gravity theory reduces to the symmetric teleparallel equivalent of general
relativity (plus a cosmological constant), and the metric takes the
(Anti)de-Sitter-Schwarzschild form.Comment: Matches published version in JCAP. 24 pages, 1 figur
Cosmological Perturbation Theory in Metric-Affine Gravity
We formulate cosmological perturbation theory around the spatially curved
FLRW background in the context of metric-affine gauge theory of gravity which
includes torsion and nonmetricity. Performing scalar-vector-tensor
decomposition of the spatial perturbations, we find that the theory displays a
rich perturbation spectrum with helicities 0, 1, 2 and 3, on top of the usual
scalar, vector and tensor metric perturbations arising from Riemannian
geometry. Accordingly, the theory provides a diverse phenomenology, e.g. the
helicity-2 modes of the torsion and/or nonmetricity tensors source helicity-2
metric tensor perturbation at the linear level leading to the production of
gravitational waves. As an immediate application, we study linear perturbation
of the nonmetricity helicity-3 modes for a general parity-preserving action of
metric-affine gravity which includes quadratic terms in curvature, torsion, and
nonmetricity. We then find the conditions to avoid possible instabilities in
the helicity-3 modes of the spin-3 field.Comment: 23+20 pages, 5 appendice
Singularities and n-dimensional black holes in torsion theories
In this work we have studied the singular behaviour of gravitational theories with non symmetric connections. For this purpose we introduce a new criteria for the appearance of singularities based on the existence of black/white hole regions of arbitrary codimension defined inside a spacetime of arbitrary dimension. We discuss this prescription by increasing the complexity of the particular torsion theory under study. In this sense, we start with Teleparallel Gravity, then we analyse Einstein-Cartan theory, and finally dynamical torsion models