Aether, Dark Energy, and String Compactifications

Understand

The 19th century Aether died with Special Relativity but was resurrected by General Relativity in the form of dark energy; a tensile material with tension equal to its energy density.

• Such a material is provided by the D-branes of string-theory; these can support the fields of supersymmetric particle-physics, although their energy density is cancelled by orientifold singularities upon compactification.
• Dark energy can still arise from supersymmetry-breaking anti-D-branes but it is probably time-dependent.
• Recent results on time-dependent compactifications to an FLRW universe with late-time accelerated expansion are reviewed.