String Theory
Ekpyrotic Universe
The Ekpyrotic Universe is a cosmological scenario introduced in 2001 in which the observable hot big bang results from the collision of higher-dimensional branes, preceded by a slow, ultra–stiff phase of contraction. Developed within brane-world extensions of M-theory, it offers an alternative to inflation for explaining large-scale homogeneity, flatness, and the origin of structure, with characteristic observational signatures such as negligible primordial tensor modes and specific non-Gaussianity patterns.
M-theory
M-theory is a proposed framework in theoretical physics that unifies the five consistent versions of superstring theory through dualities and is expected to have an eleven-dimensional low-energy limit described by eleven-dimensional supergravity. First articulated by Edward Witten in 1995, the framework incorporates extended objects such as two- and five-dimensional branes and has seen nonperturbative formulations proposed via matrix theory and holographic dualities.