Strings on AdS₂ and the high-energy limit of noncritical M-theory

Noncritical M-theory in 2+1 dimensions has been defined as a double-scaling limit of a nonrelativistic Fermi liquid on a flat two-dimensional plane. Here we study this noncritical M-theory in the limit of high energies, analogous to the α′ limit of string theory. In the related case of two-dimensional Type 0A strings, it has been argued that the conformal α′ limit leads to AdS₂ with a propagating fermion whose mass is set by the value of the RR flux. Here we provide evidence that in the high-energy limit, the natural ground state of noncritical M-theory similarly describes the AdS₂ × S¹ spacetime, with a massless propagating fermion. We argue that the spacetime effective theory in this background is captured by a topological higher-spin extension of conformal Chern-Simons gravity in 2+1 dimensions, consistently coupled to a massless Dirac field. Intriguingly, the two-dimensional plane populated by the original nonrelativistic fermions is essentially the twistor space associated with the symmetry group of the AdS₂ × S¹ spacetime; thus, at least in the high-energy limit, noncritical M-theory can be nonperturbatively described as a ''Fermi liquid on twistor space.''.