Four-Dimensional Null Energy Condition as a Swampland Conjecture
Heliudson Bernardo (Department of Physics, McGill University, Montréal, Quebec H3A 2T8, Canada); Suddhasattwa Brahma (Department of Physics, McGill University, Montréal, Quebec H3A 2T8, Canada); Keshav Dasgupta (Department of Physics, McGill University, Montréal, Quebec H3A 2T8, Canada); Mir Mehedi Faruk (Department of Physics, McGill University, Montréal, Quebec H3A 2T8, Canada); Radu Tatar (Department of Mathematical Sciences, University of Liverpool, Liverpool, L69 7ZL, United Kingdom)
We analyze four-dimensional Friedmann-Lemaître-Robertson-Walker cosmologies in type IIB, arising from a M-theory dual, and find that the null energy condition (NEC) has to be obeyed by them (except for the negatively curved case) in order for the M-theory action to have a Wilsonian effective description. However, this does not imply that the M-theory metric has to obey the 11D NEC. Thus, we propose a new swampland conjecture—the 4D NEC is a consistency condition for any theory to have a completion within M theory—with an explicit derivation of it for cosmological backgrounds from a top-down perspective. We briefly discuss the cosmological consequences of such a condition derived from M theory.
