4-Derivative gravity provides a renormalizable theory of quantum gravity at the price of introducing a physical ghost, which could admit a sensible positive-energy quantization. To understand its physics, we compute ghost-mediated scatterings among matter particles at tree-level, finding a new power-like infra-red enhancement typical of 4-derivative theories, that we dub 'ghostrahlung'. Super-Planckian scatterings get downgraded to Planckian by radiating hard gravitons and ghosts, which are weakly coupled and carry away the energy.
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| http://dx.doi.org/10.1140/epjc/s10052-018-6311-1 | DOI Listing |
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New infra-red enhancements in 4-derivative gravity.
Eur Phys J C Part Fields
October 2018
1Theoretical Physics Department, CERN, Geneva, Switzerland.
4-Derivative gravity provides a renormalizable theory of quantum gravity at the price of introducing a physical ghost, which could admit a sensible positive-energy quantization. To understand its physics, we compute ghost-mediated scatterings among matter particles at tree-level, finding a new power-like infra-red enhancement typical of 4-derivative theories, that we dub 'ghostrahlung'. Super-Planckian scatterings get downgraded to Planckian by radiating hard gravitons and ghosts, which are weakly coupled and carry away the energy.
View Article and Find Full Text PDFQuantum mechanics of 4-derivative theories.
Eur Phys J C Part Fields
April 2016
Dipartimento di Fisica dell'Università di Pisa and INFN, Pisa, Italy ; Theory Division, CERN, Geneva, Switzerland.
A renormalizable theory of gravity is obtained if the dimension-less 4-derivative kinetic term of the graviton, which classically suffers from negative unbounded energy, admits a sensible quantization. We find that a 4-derivative degree of freedom involves a canonical coordinate with unusual time-inversion parity, and that a correspondingly unusual representation must be employed for the relative quantum operator. The resulting theory has positive energy eigenvalues, normalizable wavefunctions, unitary evolution in a negative-norm configuration space.
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