Does projectable Horava gravity reduce to general relativity at long distances?
In plain words
Horava gravity treats space and time differently at very short distances, which makes it calculable to arbitrarily high energies. Whether at everyday distances it turns back into Einstein's theory, despite an extra gravitational mode it carries, is open.
Precise statement
Projectable Horava gravity in $3+1$ dimensions is perturbatively renormalizable (Barvinsky, Blas, Herrero-Valea, Sibiryakov, Steinwachs 2016) and has asymptotically free UV fixed points with RG trajectories reaching the region where the kinetic coupling $\lambda$ takes its general-relativity value 1, with the gravitational coupling going to zero at both ends (Barvinsky, Kurov, Sibiryakov 2023). The theory also contains an extra scalar graviton that is unstable or strongly coupled near $\lambda = 1$. Determine whether the IR theory along these trajectories passes solar-system and gravitational-wave tests, including bounds on Lorentz violation in gravity. An answer is the IR effective theory including the scalar sector, compared with those bounds.
What would settle it
A computation of the IR limit of the asymptotically free trajectories, scalar sector included, confronted with observational bounds.
Status in the literature
Unverified note: it names recent work and was partly written without a live literature search; it awaits a check by an editor.
UV-to-IR trajectories found (Phys. Rev. D 108, L121503, 2023); viability of the IR scalar sector open as of 2026.
Parent problems
- Special case of Which theory completes general relativity at the Planck scale? · open · from revision 1 The parent was revised since revision 1: it now states another question.
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