Barbero-Immirzi parameter as a scalar field: K-inflation from loop quantum gravity?

By V. Taveras, N. Yunes. 2008

135 citations recorded by the source corpus.

We consider a loop-quantum gravity inspired modification of general relativity, where the Holst action is generalized by making the Barbero-Immirzi (BI) parameter a scalar field, whose value could be dynamically determined. The modified theory leads to a nonzero torsion tensor that corrects the field equations through quadratic first derivatives of the BI field. Such a correction is equivalent to general relativity in the presence of a scalar field with nontrivial kinetic energy. This stress energy of this field is automatically covariantly conserved by its own dynamical equations of motion, thus satisfying the strong equivalence principle. Every general relativistic solution remains a solution to the modified theory for any constant value of the BI field. For arbitrary time-varying BI fields, a study of cosmological solutions reduces the scalar-field stress energy to that of a pressureless perfect fluid in a comoving reference frame, forcing the scale-factor dynamics to be equivalent to those of a stiff equation of state. Upon ultraviolet completion, this model could provide a natural mechanism for k inflation, where the role of the inflaton is played by the BI field and inflation is driven by its nontrivial kinetic energy instead of a potential.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics, Statistical and Nonlinear Physics

View Paper: https://www.semanticscholar.org/paper/29e923c0fb5fb04adf2b3a7a6f27e902706e5377

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Citations in the corpus

Varying Constants, Gravitation and Cosmology (2010, background): “• Models based on discrete quantum gravity [225] or on loop quantum gravity in which the Barbero-Immirzi parameter controls the minimum eigenvalue of the area operator and could be promoted to a field, leading to a classical coupling of Einstein gravity with a scalar-field stress-energy tensor [352,”
Search for New Physics with Atoms and Molecules (2017, background): “These include: discrete quantum gravity (Gambini and Pullin, 2003); loop quantum gravity (Taveras and Yunes, 2008); chameleon models (Khoury and Weltman, 2004a); dark energy models with a nonminimal coupling of a quintessence field (Avelino et al.”