The classical theory of strain in material continua is reviewed and
generalized to space-time. Strain is attributed to "external" (matter/energy
fields) and intrinsic sources fixing the global symmetry of the universe
(defects in the continuum). A Lagrangian for space-time is worked out, adding
to the usual Hilbert term an "elastic" contribution from intrinsic strain. This
approach is equivalent to a peculiar tensor field, which is indeed part of the
metric tensor. The theory gives a configuration of space-time accounting both
for the initial inflation and for the late acceleration. Considering also the
contribution from matter the theory is used to fit the luminosity data of type
Ia supernovae, giving satisfactory results.Comment: Revised to match the version accepted for publication in Class.
Quantum Gra
