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Updated: Jun 3, 2026
11:03
An Analog Macroscopic Technique for Studying Molecular Hydrodynamic Processes in Dense Gases and Liquids
Published on: December 4, 2017
Dynamical selection of the primordial density fluctuation amplitude
Jean-Luc Lehners1, Paul J Steinhardt
1Perimeter Institute for Theoretical Physics, 31 Caroline Street N, Waterloo, Ontario N2L 2Y5, Canada.
Physical Review Letters
|March 17, 2011
Summary
Ekpyrotic cosmological models, based on heterotic M theory, naturally explain the observed amplitude of primordial density perturbations. This avoids the fine-tuning and anthropic selection often needed in inflationary models.
Area of Science:
- Cosmology
- Theoretical Physics
- String Theory
Background:
- Inflationary models often predict a much larger amplitude of primordial density perturbations (Q) than observed.
- Anthropic selection is frequently invoked to reconcile these predictions with observational data, particularly with complex energy landscapes in microphysics.
Purpose of the Study:
- To investigate alternative cosmological models that naturally explain the observed value of Q.
- To explore ekpyrotic models derived from heterotic M theory as a potential solution.
Main Methods:
- Analysis of ekpyrotic cosmological models derived from heterotic M theory.
- Investigation of dynamical selection mechanisms within these models.
Main Results:
- Ekpyrotic models based on heterotic M theory naturally favor the observed value of Q (approximately 10^-5).
- These models circumvent the need for fine-tuning and anthropic selection required by many inflationary models.
Conclusions:
- Ekpyrotic models offer a compelling alternative to inflationary cosmology for explaining the amplitude of primordial density perturbations.
- Dynamical selection in heterotic M-theory-based ekpyrotic models provides a natural mechanism for the observed cosmic structure.
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