Symmetries, gravitation and strings

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Loop quantum effect and the fate of tachyon field collapse

Publication . Tavakoli, Yaser; Moniz, Paulo; Marto, João; Ziaie, Amir Hadi

We study the fate of gravitational collapse of a tachyon field matter. In presence of an inverse square potential a black hole forms. Loop quantum corrections lead to the avoidance of classical singularities, which is followed by an outward flux of energy.

2012Journal article

Open access

Gravitational collapse with tachyon field and barotropic fluid

Publication . Tavakoli, Yaser; Marto, João; Ziaie, Amir Hadi; Moniz, Paulo

A particular class of space-time, with a tachyon field, ϕ, and a barotropic fluid constituting the matter content, is considered herein as a model for gravitational collapse. For simplicity, the tachyon potential is assumed to be of inverse square form i.e., V(ϕ)∼ϕ^(−2). Our purpose, by making use of the specific kinematical features of the tachyon, which are rather different from a standard scalar field, is to establish the several types of asymptotic behavior that our matter content induces. Employing a dynamical system analysis, complemented by a thorough numerical study, we find classical solutions corresponding to a naked singularity or a black hole formation. In particular, there is a subset where the fluid and tachyon participate in an interesting tracking behaviour, depending sensitively on the initial conditions for the energy densities of the tachyon field and barotropic fluid. Two other classes of solutions are present, corresponding respectively, to either a tachyon or a barotropic fluid regime. Which of these emerges as dominant, will depend on the choice of the barotropic parameter, γ. Furthermore, these collapsing scenarios both have as final state the formation of a black hole.

2013Journal article

Restricted access

Semiclassical collapse with tachyon field and barotropic fluid

Publication . Tavakoli, Yaser; Marto, João; Ziaie, Amir Hadi; Moniz, Paulo

The purpose of this paper is to extend the analysis presented in Goswami et al. [Phys. Rev. Lett. 96, 031302 (2006)] by means of investigating how a specific type of loop (quantum) effect can alter the outcome of gravitational collapse. To be more concrete, a particular class of spherically symmetric spacetime is considered with a tachyon field ϕ and a barotropic fluid constituting the matter content; the tachyon potential V(ϕ) is assumed to be of the form ϕ^(−2). Within inverse triad corrections, we then obtain, for a semiclassical description, several classes of analytical as well as numerical solutions. Moreover, we identify a subset whose behavior corresponds to an outward flux of energy, thus avoiding either a naked singularity or a black hole formation.

2013Journal article

Restricted access