Effective QFT and what it tells us about dynamical torsion

The covariantly constant spacetime torsion is one of the fields which may break Lorentz and CPT symmetry. We review the previous works on the dynamical torsion in the framework of effective quantum field theory (QFT). It turns out that the existence of propagating torsion is strongly restricted by the QFT principles. In particular, the torsion mass must be much greater than the masses of all fermionic particles. In this situation, the main chance to observe torsion is due to some symmetry breaking which may, in principle, produce almost constant background torsion field.Comment: 5 pages, Accepted for publication in the Proceedings of the Fifth Meeting on CPT and Lorentz Symmetry, Bloomington, Indiana, U.S.A., June 28-July 2, 201

Renormalization in QED and QFT with a Lorentz- and CPT-violating backgrounds

The general features of renormalization and the renormalization group in QED and in general quantum field theories in curved spacetime with additional Lorentz- and CPT-violating background fields are reviewed.Comment: 4 pages, WS styles, Presented at the Sixth Meeting on CPT and Lorentz Symmetry,Bloomington, Indiana, June 17-21, 201

Effective field theory and fundamental interactions

There are many possible gravitational applications of an effective approach to Quantum Field Theory (QFT) in curved space. We present a brief review of effective approach and discuss its impact for such relevant issues as the cosmological constant (CC) problem and inflation driven by vacuum quantum effects. Furthermore it is shown how one can impose significant theoretical constraints on a non-metric gravity using only theoretical effective field theory framework.Comment: LaTeX, 11 pages, 2 figures. Based o talks given at the following meetings: 1. CONFERENCE ON Fundamental Symmetries and Fundamental Constants, ICTP, Trieste, Italy. September 15-18, 2004; 2. Colloquium "Theory and Experiment in Cosmology and Gravitation", in honor of Prof. Jose Plinio Baptista on the occasion of his 70th birthday. (UFES, Vitoria, Brazil. September 22-24, 2004). To be published in the proceeding

Anomaly-induced effective action and Chern-Simons modification of general relativity

Recently it was shown that the quantum vacuum effects of massless chiral fermion field in curved space-time leads to the parity-violating Pontryagin density term, which appears in the trace anomaly with imaginary coefficient. In the present work the anomaly-induced effective action with the parity-violating term is derived. The result is similar to the Chern-Simons modified general relativity, which was extensively studied in the last decade, but with the kinetic terms for the scalar different from those considered previously in the literature. The parity-breaking term makes no effect on the zero-order cosmology, but it is expected to be relevant in the black hole solutions and in the cosmological perturbations, especially gravitational waves.Comment: 15 pages, LaTeX, no Figures. Two references added, correction in the Acknowledgements. Fits the manuscript accepted in Physics Letters

Light bending in F[g(□)R]F\left[g(\square)R\right] extended gravity theories

We show that in the weak field limit the light deflection alone cannot distinguish between different $R + F[g(\square)R]$ models of gravity, where $F$ and $g$ are arbitrary functions. This does not imply, however, that in all these theories an observer will see the same deflection angle. Owed to the need to calibrate the Newton constant, the deflection angle may be model-dependent after all necessary types of measurements are taken into account.Comment: 17 pages, 1 figur