Search results for "Scalar theories of gravitation"
showing 5 items of 5 documents
Induced scalarization in boson stars and scalar gravitational radiation
2012
The dynamical evolution of boson stars in scalar-tensor theories of gravity is considered in the physical (Jordan) frame. We focus on the study of spontaneous and induced scalarization, for which we take as initial data configurations on the well-known S-branch of a single boson star in general relativity. We show that during the scalarization process a strong emission of scalar radiation occurs. The new stable configurations (S-branch) of a single boson star within a particular scalar-tensor theory are also presented.
Dynamical formation of a Reissner-Nordström black hole with scalar hair in a cavity
2016
In a recent Letter [Sanchis-Gual et al., Phys. Rev. Lett. 116, 141101 (2016)], we presented numerical relativity simulations, solving the full Einstein--Maxwell--Klein-Gordon equations, of superradiantly unstable Reissner-Nordstr\"om black holes (BHs), enclosed in a cavity. Low frequency, spherical perturbations of a charged scalar field trigger this instability. The system's evolution was followed into the nonlinear regime, until it relaxed into an equilibrium configuration, found to be a hairy BH: a charged horizon in equilibrium with a scalar field condensate, whose phase is oscillating at the (final) critical frequency. Here, we investigate the impact of adding self-interactions to the …
Classical Field Theory of Gravitation
2012
The classical field theories developed in the preceding chapters all have in common that they are formulated on a flat spacetime, i.e. on a four-manifold which is a Euclidean space and which locally is decomposable into a direct product M 4 = ℝR3 ℝR of a physical space ℝR3 x of motions, and a time axis ℝRt. The first factor is the threedimensional space as it is perceived by an observer at rest while the time axis displays the (coordinate) time that he/she measures on his/her clocks. This spacetime is endowed with the Poincare group as the invariance group of physical laws and inherits the corresponding specific causality structure.
Wormholes supported by hybrid metric-Palatini gravity
2012
Recently, a modified theory of gravity was presented, which consists of the superposition of the metric Einstein-Hilbert Lagrangian with an $f(\cal R)$ term constructed \`{a} la Palatini. The theory possesses extremely interesting features such as predicting the existence of a long-range scalar field, that explains the late-time cosmic acceleration and passes the local tests, even in the presence of a light scalar field. In this brief report, we consider the possibility that wormholes are supported by this hybrid metric-Palatini gravitational theory. We present here the general conditions for wormhole solutions according to the null energy conditions at the throat and find specific examples…
Star-product approach to quantum field theory: The free scalar field
1990
The star-quantization of the free scalar field is developed by introducing an integral representation of the normal star-product. A formal connection between the Feynman path integral in the holomorphic representation and the star-exponential is established for the interacting scalar fields.