On the Gauge Invariance of Secondary Gravitational Waves
arXiv:2501.13691 · doi:10.1088/1475-7516/2025/07/016
Abstract
Second-order tensor perturbations induced by primordial fluctuations play a crucial role in probing small-scale physics, but gauge dependence of their energy density has remained a fundamental challenge in cosmological perturbation theory. We address this issue by introducing a boundary condition-based filtering method that extracts physical radiation through the Sommerfeld criterion. We demonstrate that after filtering non-physical modes, the energy density of secondary gravitational waves becomes gauge-invariant and exhibits physically consistent behavior in the sub-horizon limit. This approach provides a unified framework for both adiabatic and isocurvature perturbations, enhancing theoretical predictions and observational signatures of early universe physics.
v3, 15 pages, 2 figures, JCAP accepted
References in corpus (10)
- GWTC-2: Compact Binary Coalescences Observed by LIGO and Virgo During the First Half of the Third Observing Run
- GWTC-3: Compact Binary Coalescences Observed by LIGO and Virgo During the Second Part of the Third Observing Run
- NANOGrav Hints to Primordial Black Holes as Dark Matter
- Did NANOGrav see a signal from primordial black hole formation?
- Gauge Independence of Induced Gravitational Waves
- Approximate gauge independence of the induced gravitational wave spectrum
- Gravitational waves from dark matter isocurvature
- Gauge transformation of scalar induced tensor perturbation during matter domination
- From formation to evaporation: Induced gravitational wave probes of the primordial black hole reheating scenario
- On the energy of gravitational waves