Scalar-induced gravitational waves including isocurvature perturbations with lattice simulations

Abstract

Scalar-induced gravitational waves (SIGWs) open a unique window into early-universe physics. While their generation from adiabatic perturbations has been extensively studied, the contribution from isocurvature perturbations remains largely unexplored. In this work, we develop a lattice simulation framework to compute the stochastic gravitational wave background from both pure isocurvature and mixed initial conditions. Our numerical results show excellent agreement with semi-analytical predictions in the pure isocurvature case. We further analyze multi-peak structures under general initial conditions and find that they closely match those produced in purely adiabatic scenarios. Additionally, we examine SIGWs in early matter-dominated eras, revealing that the peak amplitude and spectral slope are sensitive to the microphysical properties of the dominant field, such as the primordial black hole mass, abundance, or soliton decay rate. This study establishes lattice simulations as a robust tool for predicting SIGW spectra from complex primordial perturbations, with important implications for interpreting current and future gravitational wave observations.

20 pages, 8 figures, accepted by JCAP

References in corpus (19)

• The NANOGrav 15-year Data Set: Evidence for a Gravitational-Wave Background
• Search for an isotropic gravitational-wave background with the Parkes Pulsar Timing Array
• Searching for the nano-Hertz stochastic gravitational wave background with the Chinese Pulsar Timing Array Data Release I
• The second data release from the European Pulsar Timing Array III. Search for gravitational wave signals
• Gravitational Wave Spectrum Induced by Primordial Scalar Perturbations
• The cosmological gravitational wave background from primordial density perturbations
• Gravitational waves induced from primordial black hole fluctuations: The effect of an extended mass function
• The Gravitational-Wave Physics II: Progress
• Resonant multiple peaks in the induced gravitational waves
• Gravitational waves from dark matter isocurvature
• Probing modified Hawking evaporation with gravitational waves from the primordial black hole dominated universe
• From formation to evaporation: Induced gravitational wave probes of the primordial black hole reheating scenario
• Universal Gravitational Waves from Interacting and Clustered Solitons
• Anisotropies in Scalar-Induced Gravitational-Wave Background from Inflaton-Curvaton Mixed Scenario with Sound Speed Resonance
• Multiple peaks in gravitational waves induced from primordial curvature perturbations with non-Gaussianity
• Anisotropies of cosmological gravitational wave backgrounds in non-flat spacetime
• Using Gravitational Wave Signals to Disentangle Early Matter Dominated Epochs
• Gravitational waves induced by matter isocurvature in general cosmologies
• Sound waves from primordial black hole formations

Cited by in corpus (1)

• Numerical simulations of primordial black hole formation via delayed first-order phase transitions