Abstract
Astonishing cancellations take place in the calculation of high-energy scattering cross sections in quantum quadratic gravity, a quantum field theory for gravity. Tree-level differential cross sections that are minimally inclusive behave as $1/E^2$, as desired for a well-behaved UV completion. Such cross sections are calculated for the various spin states of the massless and massive graviparticles. These describe the hard scattering processes that occur in a picture involving the gravitational analog of parton showers. The structure of some of the simpler amplitudes is also explored. Unitarity without positivity is the key property of the perturbative theory.
Highlights
The action of quantum quadratic gravity (QQG) has RμνRμν and R2 terms in addition to the Einstein term. This theory was proposed early as a quantum field theory (QFT) for gravity when it was found to display some of the desired characteristics of a UV-complete theory; namely, renormalizability and asymptotic freedom [1,2,3]
The main obstacle for QQG has been the existence of negative norm states, or ghosts, in the perturbative spectrum
The negative norm for the ghost is synonymous with the wrong overall sign of the ghost propagator, and the perturbation theory becomes populated with odd minus signs
Summary
The action of quantum quadratic gravity (QQG) has RμνRμν and R2 terms in addition to the Einstein term. This leads to a renormalizable perturbation theory where ghosts propagate with positive energy. For a thorough discussion of backward in time decay see [4,5] At this point one is tempted to more directly take into account the true nature of ghost propagation within perturbation theory, which must be reformulated in terms of the dressed propagator. The high-energy scattering of protons at the LHC for instance is largely described in terms of the interactions of quarks and gluons, the fundamental degrees of freedom of perturbative QCD; like the ghosts, quarks and gluons are not asymptotic states. It is necessary to produce good high-energy behavior
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
