Massive Higher-Spin Multiplets and Asymptotic Freedom in Quantum Gravity

Abstract

We consider massive higher-spin multiplets coupled to quantum gravity and compute their contributions to the gravitational beta functions at one loop. Such theories, if quantized with the Feynman prescription, would contain ghosts. Instead, those degrees of freedom are turned into purely virtual particles by means of the fakeon prescription and the resulting theories are both renormalizable and unitary. We extract the necessary number of fields to obtain asymptotic freedom by solving the relevant renormalization-group equations in the ultraviolet limit. We show that in the case of irreducible rank-$s$ bosons with minimal kinetic term only a certain number of fields with $0\le s\le 3$ is compatible with asymptotic freedom. No solution involving fermionic rank-$s$ fields are found. We also consider the cases of rank-$1$ and symmetric rank-$2$ tensor fields with nonminimal kinetic terms and repeat the analysis, finding that the allowed number of fields is enlarged. Possible implications for metric affine theories of gravity are pointed out.

30 pages, 2 figures; v2: expanded introduction, minor changes, PRD

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Cited by in corpus (5)

• Metric-Affine Gravity as an Effective Field Theory
• Radiatively stable ghost and tachyon freedom in Metric Affine Gravity
• Einstein-Proca theory from the Einstein-Cartan formulation
• Purely Virtual Particles in Quantum Gravity, Inflationary Cosmology and Collider Physics
• Heat kernel of non-minimal second-order operators