The Holographic Space-Time Model of Cosmology
T. Banks, W. Fischler
TL;DR
Problem: To explain early-universe dynamics and cosmological perturbations using a finite, unitary quantum gravity framework instead of standard QFT in curved spacetime. Approach: It develops the Holographic Space-time (HST) framework with boundary holographic degrees of freedom on causal diamonds, time-dependent Hamiltonians, and overlap consistency, yielding inflation as a dS-like horizon phase and a subsequent dilute black-hole era. Contributions: It derives predictions for two- and three-point fluctuations with approximate SO(1,4) invariance, suggests a suppressed tensor-to-scalar ratio relative to conventional inflation, and proposes dark matter and baryogenesis via primordial black holes, contingent on simulations of primordial structure formation. Significance: The work offers a finite, unitary quantum gravity cosmology with a small parameter set and testable distinctions from slow-roll inflation, motivating targeted observations of tensor modes, non-Gaussianity, and black-hole-era structure.
Abstract
This essay outlines the Holographic Space-time (HST) theory of cosmology and its relation to conventional theories of inflation. The predictions of the theory are compatible with observations, and one must hope for data on primordial gravitational waves or non-Gaussian fluctuations to distinguish it from conventional models. The model predicts an early era of structure formation, prior to the Big Bang. Understanding the fate of those structures requires complicated simulations that have not yet been done. The result of those calculations might falsify the model, or might provide a very economical framework for explaining dark matter and the generation of the baryon asymmetry.