arXiv subjects

Thomas M. Sangy

Publications and source records attributed to Thomas M. Sangy.

4 recordsLinked to original sources

arXiv2026

On the Renormalization in Conformal Quantum Gravity

One-loop divergences in classically conformal theory in curved spacetime is a nontrivial issue if the theory under consideration possesses gauge invariance. In this case, quantization involves introducing the gauge-fixing term and the action of ghosts, both of which are not conformal. The formal proof of the conformal invariant renormalizability in this situation, including interacting theories, has been given in the paper from 1984 by one of the present authors. Owing to BRST symmetry, the contributions of the gauge-fixing and ghost sectors to the conformal variation of the effective action cancel each other. This cancellation does not hold in the finite part of the one-loop and higher-loops effective action, that results in the anomaly. In this paper, we extend the early results on conformal matter fields in external gravitational field and apply them to conformal quantum gravity, including the case of conformal gravity coupled to other conformal matter fields. The gauge-fixing in the Weyl-squared gravity is more complicated, nevertheless, the proof of the one-loop conformal invariant renormalization using BRST symmetry is possible. As a preliminary to conformal quantum gravity, we also present a detailed general proof of conformal invariant one-loop divergences in the corresponding semiclassical theory.

hep-th↗

arXiv2026

On the total derivative divergence for a nonminimal vector operator

We report on the calculation of the total derivative $\Box R$ term in the divergence of vacuum effective action for the nonminimal vector field operator in a curved space background. This term led to an interesting discussions in the literature, in particular because it defines the local part of anomaly-induced effective action in conformal quantum gravity and may be decisive for the renormalizability of this theory. The divergent term of our interest was previously derived several times. One of the main results is that the mentioned local term is gauge-fixing dependent in the case of electromagnetic field, that contradicts the general theorems about quantum corrections. We perform the derivation by using Riemann's normal coordinates and confirm the previous results. The discussion includes the possible role of the gauge-dependent IR regulators and the related ambiguity.

hep-th↗

arXiv2025

Effective delta sources and Newtonian limit in nonlocal gravity

We investigate the Newtonian limit of a class of nonlocal gravity models with exponential form factors $f_s (\Box) = \exp [(-\Box/μ_s^2)^{N_s}]$. Our main goal is to identify similarities and differences between models in this family in regard to weak-field solutions. To this end, we use the effective source formalism to compare the related effective delta sources, mass functions, and Newtonian potentials. We obtain a variety of representations for these quantities in terms of series, integrals, and special functions, as well as simple approximations that capture the relevant dependence on the parameters $N_s$ and $μ_s$ - which can be used to explore the weak-field phenomenology of nonlocal gravity. We explain why only for $N_s>1$ the Newtonian potential oscillates and prove that, despite the oscillations, the effective masses are positive. Moreover, we verify that these linearized solutions are regular (without curvature singularities). Finally, we also calculate the form of the leading logarithmic quantum correction to the Newtonian potential in these models. In all our considerations, we assume that $N_s$ is a positive real parameter. The cases of non-integer $N_s$ might be applied beyond nonlocal gravity, in effective approaches to implement quantum corrections in the weak field regime.

gr-qc↗

arXiv2025

Renormalizable quantum field theory in curved spacetime with external two-form field

We argue that the renormalizability of interacting quantum field theory on the curved-space background with an additional external antisymmetric tensor (two-form) field requires nonminimal interaction of the antisymmetric field with quantum fermions and scalars. The situation is qualitatively similar to the metric and torsion background. In both cases, one can explore the renormalization group running for the parameters of nonminimal interaction and see how this interaction behaves in the UV limit. General considerations are confirmed by the one-loop calculations in the well-known gauge model based on the $SU(2)$ gauge group.

hep-th↗