Fr.: Univers ekpyrotique
A cosmological model in which the → Big Bang is not the beginning of the → Universe, but a transitory phase in a more global scenario. The ekpyrotic Universe model is fundamentally different from the → standard cosmology and offers radically different explanations for the cosmological problems (→ homogeneity, → isotropy, → flatness, → magnetic monopoles, etc.). In this highly speculative model → space-time has five dimensions, four spatial and one temporal. Two three-dimensional → branes, one visible and one hidden, collide following the contraction of the extra dimension. The contraction produces a blue shift effect that converts gravitational energy into brane kinetic energy. Some fraction of this kinetic energy is converted into matter and radiation that can fuel the Big Bang. The resulting temperature is finite, so the hot Big Bang phase begins without a → singularity. Apart from being speculative, this model suffers from several fine tunings (J. Khoury et al. 2001, Phys. Rev. D64, 123522 (hep-th/0103239); P. J. Steinhardt & N. Turok, 2002, Phys. Rev. D65, 126003 (hep-th/0111098), and references therein).
Ekpyrotic is inspired by the ancient Stoic doctrine according to which the world ends in a supreme conflagration, called ekpyrosis, and then reborns from the fire (palingenesis), only to be destroyed again at the end of the new cycle; ekpyrosis, from Gk. ek- "out of," → ex-, + → pyro- combining form of pyr, → fire, + -sis a suffix used to form nouns of action, process, state, condition, such as thesis, analysis, catharsis; → Universe.