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Luca Buoninfante (Nordita in Sweden)

Date: Tue. October 31st, 2023, 11:30 am-12:30 pm
Location: Rock 221 Foldy Room

Massless and Partially Massless Limits in Quadratic Gravity 
In the context of perturbative quantum field theory, the addition of quadratic-curvature invariants to the Einstein-Hilbert action makes it possible to achieve strict renormalizability in four dimensions. The additional quadratic terms are multiplied by dimensionless coefficients that are related to the masses of the extra gravitational degrees of freedom and to the interaction couplings. The aim of this talk is to analyse the limit of the theory in which the Weyl-squared coefficient tends to infinity. Remarkably, the result of this limit turns out to be sensitive to the presence of a cosmological constant:  when the latter is zero we have a massless limit for the spin-2 ghost, while when the cosmological constant is different from zero we obtain a partially massless limit. We show that the renormalizability property and the  ghost-like nature of the massive spin-2 field  ensure that the two limits do not hit strong couplings, unlike standard ghost-free theories of massive gravity. In particular, in the partially massless limit the interactions mediated by the spin-2 sector vanish. We argue that our results can be useful for understanding the high-energy limit of Quadratic Gravity. This talk is based on arXiv:2308.11324.
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