Critical collapse in K-essence models
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Springer
Received: April 11, Revised: June 2, Accepted: June 21, Published: July 21,
2020 2020 2020 2020
Radouane Gannoujia and Yolbeiker Rodr´ıguez Baezb,1 a
Instituto de F´ısica, Pontificia Universidad Cat´ olica de Valpara´ıso, Av. Brasil 2950, Valpara´ıso, Chile b Universidad T´ecnica Federico Santa Mar´ıa, Av. Espa˜ na 1680, Valpara´ıso, Chile
E-mail: [email protected], [email protected] Abstract: We study gravitational collapse in K-essence model with shift symmetry. For these models, we have the formation of two types of horizons, event and sonic. For the particular case K(X) = X +βX 2 we found three different regimes. In the weak field regime the scalar field disperses to infinity, in the very strong regime both horizons form at the same time and finally for the intermediate regime, the sonic horizon could form first or both horizons form at the same time. The threshold of formation of the horizon is found in the regime where the sonic horizon forms first. We observe a universal behavior with a scaling parameter γ ' 0.51. Interestingly this universal behavior is encoded in the sonic horizon even if an event horizon is expected to never form because of loss of hyperbolicity of the equations. Keywords: Black Holes, Classical Theories of Gravity ArXiv ePrint: 2003.13730
1
Corresponding author.
c The Authors. Open Access, Article funded by SCOAP3 .
https://doi.org/10.1007/JHEP07(2020)132
JHEP07(2020)132
Critical collapse in K-essence models
Contents 1
2 K-essence
2
3 Model and equations
4
4 Characteristics
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5 Numerical results 5.1 Weak field regime 5.2 Strong field regime
7 7 8
6 Conclusions
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A Stealth scalar field in K-essence
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1
Introduction
During the last decades our knowledge of gravity has extremely been improved with general relativity (GR) remaining our best classical theory to describe it. Some inconsistencies or debates in the cosmology community rise from time to time, such as the Hubble constant tension nowadays, but they are in no way a direct test of GR. All direct tests are consistent with the theory, see e.g. [1]. On the other hand, GR is a classical theory and therefore partial. It is for example geodesically incomplete for most of its solutions [2] like black holes which contain spacetime singularity. Also, some theoretical arguments challenge our knowledge in cosmology and the existence of the cosmological constant. Recently, a lot of attention has focused on the String Swampland [3, 4] which rejects any de Sitter solution [5] and therefore the existence of the cosmological constant. The origin of the recent acceleration of the universe could be due to a scalar field. This would be a very interesting promotion of the relevance of scalar fields in the dynamics of the universe. At the same time, many studies try to see if scalar fields could be locally observed, and what are their effects around black holes. For example, we can ask if we could observe any deviation from Kerr black hole by measurement of quasi-normal modes [6]. Even if the ans
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