TY - JOUR
T1 - Comment on "extended Born-Infeld theory and the bouncing magnetic universe"
AU - García-Salcedo, Ricardo
AU - Gonzalez, Tame
AU - Horta-Rangel, Antonio
AU - Quiros, Israel
N1 - Publisher Copyright:
© 2014 American Physical Society.
PY - 2014/12/1
Y1 - 2014/12/1
N2 - In a recent paper [Phys. Rev. D 85, 023528 (2012)PRVDAQ1550-799810.1103/PhysRevD.85.023528] the authors proposed a generalized Born-Infeld electrodynamics coupled to general relativity which produces a nonsingular bouncing universe. For a magnetic universe the resulting cosmic evolution inevitably interpolates between asymptotic de Sitter states. Here we show that (i) the conclusion about the inevitability of the asymptotic vacuum regime in a magnetic universe is wrong, (ii) a sudden curvature singularity - not better than the big bang - arises, but for spaces of positive curvature, (iii) the square sound speed can be a negative quantity, signaling instability against small perturbations of the background energy density, and (iv) the speed of sound can exceed the speed of light, which raises a causality issue.
AB - In a recent paper [Phys. Rev. D 85, 023528 (2012)PRVDAQ1550-799810.1103/PhysRevD.85.023528] the authors proposed a generalized Born-Infeld electrodynamics coupled to general relativity which produces a nonsingular bouncing universe. For a magnetic universe the resulting cosmic evolution inevitably interpolates between asymptotic de Sitter states. Here we show that (i) the conclusion about the inevitability of the asymptotic vacuum regime in a magnetic universe is wrong, (ii) a sudden curvature singularity - not better than the big bang - arises, but for spaces of positive curvature, (iii) the square sound speed can be a negative quantity, signaling instability against small perturbations of the background energy density, and (iv) the speed of sound can exceed the speed of light, which raises a causality issue.
UR - http://www.scopus.com/inward/record.url?scp=84914695523&partnerID=8YFLogxK
U2 - 10.1103/PhysRevD.90.128301
DO - 10.1103/PhysRevD.90.128301
M3 - Artículo
SN - 1550-7998
VL - 90
JO - Physical Review D - Particles, Fields, Gravitation and Cosmology
JF - Physical Review D - Particles, Fields, Gravitation and Cosmology
IS - 12
M1 - 128301
ER -