Implications of Planck2015 for inflationary, ekpyrotic and anamorphic bouncing cosmologies

TL;DR

The paper discusses how Planck2015 data challenges classic inflationary models, favoring alternative theories like ekpyrotic and anamorphic bouncing cosmologies that better fit observations.

Contribution

It analyzes the implications of Planck2015 results for various cosmological models, highlighting the viability of ekpyrotic and anamorphic bouncing scenarios over traditional inflation.

Findings

Planck2015 disfavors classic inflationary models.

Ekpyrotic models remain consistent with observations.

Anamorphic cosmology offers distinctive testable predictions.

Abstract

The results from Planck2015, when combined with earlier observations from WMAP, ACT, SPT and other experiments, were the first observations to disfavor the "classic" inflationary paradigm. To satisfy the observational constraints, inflationary theorists have been forced to consider plateau-like inflaton potentials that introduce more parameters and more fine-tuning, problematic initial conditions, multiverse-unpredictability issues, and a new 'unlikeliness problem.' Some propose turning instead to a "postmodern" inflationary paradigm in which the cosmological properties in our observable universe are only locally valid and set randomly, with completely different properties (and perhaps even different physical laws) existing in most regions outside our horizon. By contrast, the new results are consistent with the simplest versions of ekpyrotic cyclic models in which the universe is smoothed and flattened during a period of slow contraction followed by a bounce, and another promising bouncing theory, anamorphic cosmology, has been proposed that can produce distinctive predictions.