arXiv subjects

O. P. Santillán

Publications and source records attributed to O. P. Santillán.

4 recordsLinked to original sources

arXiv2026

About possible measures in Quantum Gravity

There exist several different proposals for a measure in Quantum Gravity theories. Although sometimes being labelled as non covariant, the measure derived in [7] for GR has the particularity that, in the extremal, the volume divergences cancel out. The analogous for Quadratic Gravity [1]-[2] was considered in [44]-[45]. However, as far as the author knows, the issue of volume divergences was not considered for this last measure. The present work fills this gap and presents an analysis showing that, in the extremal, these divergences cancel as well. This is up to some subtleties related to superdeterminants. The possibility of employing non invariant measures may be accepted if the anomaly in the measure is compensated by counter term redefinitions of the model under analysis. This makes difficult to disprove, at the present times, some choices of measures. Quadratic Gravity[1]-[2], is known to be renormalizable in flat space, and there are a finite number of counter terms needed in order to renormalize its effective action. However, around a curved space this is not known, and this complicates considerably the analysis. These issues are reviewed in the text, together with an analysis of covariant measures. In particular, it is shown how these measures [47]-[49] can be found if one condition in [7] is relaxed.

gr-qc↗

arXiv2025

LSZ ghostbusters in the quadratic gravity stage

The present letter considers the quantization method developed in [1]-[9], which postulates that, in several situations, negative norm or ghost states can be avoided in order to give positive probabilities. These authors also postulate a candidate for a path integral for those theories, following pioneer works initiated by Dirac [10]} and Pauli \[11]. However, taking into account the non standard oscillator algebra inherent to this method, It is of interest the derivation of the LSZ rules in this context, since it may not be clear at first sight that has the usual form of the textbooks, due to the non standard oscillator algebra and the redefinitions of the states.This is done here, applied to Stelle gravity [12]-[13]. In addition, an equivalent but simpler way to deal with negative norm states is worked out, in which hermiticity is more explicit. As far as we understand, our conclusions fully agree with the arguments and expectations of those authors.

hep-th↗

arXiv2013

Probing global aspects of a geometry by the self-force on a charge: Spherical thin-shell wormholes

The self-interaction for a static point charge in the space-time of a thin-shell wormhole constructed connecting two identical Schwarzschild geometries is calculated in a series expansion. The electrostatic self-force is evaluated numerically. It is found to be attractive towards the throat except for some values of the throat radius proximate to the value of the Schwarzschild horizon for which the force is repulsive or attractive depending on the position of the charge. The result differs from the self-force in the space-time of the Schwarzschild black hole, where it is always repulsive from the center. Although these wormhole and black hole geometries are locally indistinguishable, the different topologies of both backgrounds are manifested in the electrostatic field of a point charge.

gr-qc↗

arXiv2012

Probing global aspects of a geometry by the self-force on a charge; cylindical thin-shell wormholes

We obtain the self-interaction for a point charge in the space-time of a cylindrical thin-shell wormhole connecting two identical locally flat geometries with a constant deficit angle. Although this wormhole geometry is locally indistinguishable from a cosmic string background, the corresponding self-forces are different even at the qualitative level. In fact in the cosmic string geometry the force is always repulsive while for the wormhole background we find that the force may point outwards or towards the wormhole throat depending on the parameters of the configuration. These results suggest that the study of the electromagnetic fields of charged particles is a useful tool for testing the global properties of a given background.

gr-qc↗