https://doi.org/10.1140/epjp/i2018-11841-3
Regular Article
Nonlocal modified Einstein’s field equation and geometric origin of a small cosmological constant
Athens Institute for Education and Research, Mathematics and Physics Divisions, 8 Valaoritou Street, 10671, Athens, Greece
Received:
22
October
2017
Accepted:
5
December
2017
Published online:
5
January
2018
Abstract.: We show that the description of the spacetime in terms of backward-forward extension of its corresponding metric leads to the geometric origin of a small cosmological constant. The nonlocal cosmological constant appears in the Einstein’s field equation and its mathematical expression depends on the nonlocal metric, Ricci scalar and the infinitesimal nonlocal parameter introduced in the theory. The modified theory has interesting consequences in FRW cosmology, mainly a nonsingular universe, the occurrence of a late-time accelerated expansion of the universe and an early universe dominated by a negative energy density and a positive pressure. Our model can explain the acceleration of the universe without a fine-tuned cosmological constant 
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© Società Italiana di Fisica and Springer-Verlag GmbH Germany, part of Springer Nature 2018
