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Shocks in the Early Universe.
1Canadian Institute for Theoretical Astrophysics, 60 St George Street, Toronto, Ontario M5S 3H8, Canada.
Physical Review Letters
|October 8, 2016
Summary
Cosmological perturbations unexpectedly generate shocks in the early Universe, producing gravitational waves. This finding offers a new way to probe the primordial Universe using gravitational wave experiments.
Area of Science:
- Cosmology
- Astrophysics
- Particle Physics
Background:
- Standard cosmological models assume initial conditions for perturbations.
- These perturbations are typically Gaussian, linear, adiabatic, scalar, and in the growing mode.
- Acoustic oscillations are observed on large scales due to these perturbations.
Purpose of the Study:
- To investigate the unexpected consequences of standard initial conditions for cosmological perturbations.
- To explore the production of shocks and their implications in the early Universe.
- To determine if shock formation can be detected by gravitational wave experiments.
Main Methods:
- Analysis of cosmological perturbation theory.
- Investigation of shock formation in the radiation fluid.
- Modeling of gravitational wave emission from shocks.
- Comparison with observational constraints from gravitational wave detectors.
Main Results:
- Gaussian, linear, adiabatic, scalar, growing mode perturbations produce shocks in the early Universe.
- Shocks lead to departures from local thermal equilibrium, vorticity, and gravitational waves.
- For a scale-invariant spectrum, shocks form between 1 GeV and 10^7 GeV.
- Shock formation is linked to specific power spectra, relevant for primordial black hole formation.
Conclusions:
- Shock formation in the early Universe is a direct consequence of initial cosmological perturbations.
- Gravitational waves generated by these shocks provide a detectable signal for current and future experiments.
- This provides a powerful new tool to constrain conditions in the primordial Universe as early as 10^-30 seconds after the Big Bang.
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