Out of the White Hole: A Holographic Origin for the Big Bang

TL;DR

This paper proposes a holographic braneworld model where the universe emerges from a 5D black hole, potentially resolving the big bang singularity and explaining primordial perturbations without inflation.

Contribution

It introduces a novel braneworld cosmology model with a white hole origin, linking the big bang to a 5D black hole and providing a new mechanism for primordial perturbations.

Findings

Universe emerges from a 5D Schwarzschild black hole

Holographic pressure singularity occurs inside the white hole horizon

Thermal atmosphere induces scale-invariant primordial perturbations

Abstract

While most of the singularities of General Relativity are expected to be safely hidden behind event horizons by the cosmic censorship conjecture, we happen to live in the causal future of the classical big bang singularity, whose resolution constitutes the active field of early universe cosmology. Could the big bang be also hidden behind a causal horizon, making us immune to the decadent impacts of a naked singularity? We describe a braneworld description of cosmology with both 4d induced and 5d bulk gravity (otherwise known as Dvali-Gabadadze-Porati, or DGP model), which exhibits this feature: The universe emerges as a spherical 3-brane out of the formation of a 5d Schwarzschild black hole. In particular, we show that a pressure singularity of the holographic fluid, discovered earlier, happens inside the white hole horizon, and thus need not be real or imply any pathology. Furthermore, we outline a novel mechanism through which any thermal atmosphere for the brane, with comoving temperature of 20% of the 5D Planck mass can induce scale-invariant primordial curvature perturbations on the brane, circumventing the need for a separate process (such as cosmic inflation) to explain current cosmological observations. Finally, we note that 5D space-time is asymptotically flat, and thus potentially allows an S-matrix or (after minor modifications) AdS/CFT description of the cosmological big bang.