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Boson stars in f(T) extended theory of gravity

Spherically symmetric configurations of the non- interacting massive complex scalar field, representing non-rotating boson stars, are considered within the framework of the modified torsion based f(T) gravity, with f(T) = T + α T2/2. We find that with sufficiently large negative value of α the mass of the boson stars can be made arbitrarily large. This is in contrast to General Relativity where an upper bound, Mmax∼M2Planck/m, to the mass of the boson stars built from the non-interacting scalar field exists and where the masses of boson stars in the astrophysical regime can be obtained only with the introduction of the scalar field self- interaction. With sufficiently large negative α we also find negative gravitational binding energy for all masses, which can be seen as an indication of the stability of such configurations. In its positive regime, α can not be made arbitrarily large as a phase transition in the stress--energy components of the f(T)- fluid develops. This phenomenon has already been reported to occur in polytropic stars constructed within the f(T) gravity theory.

Gravity ; Torsion ; Boson star

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