What problem does it solve?
Enhanced primordial scalar fluctuations generate gravitational waves at second order. Predicting that signal can require solving inflationary perturbation equations, evaluating cosmological transfer kernels, and repeatedly integrating the resulting spectrum during Bayesian inference. SIGWAY organizes those stages into composable components instead of tying the calculation to one fixed primordial template.
The package grew out of the LISA Cosmology Working Group analysis of how well LISA could reconstruct small-scale primordial curvature perturbations. It supports the three complementary strategies used there: flexible binned spectra, physically motivated analytic templates, and first-principles inflationary models.
Core capabilities
- Analytic or user-defined primordial curvature spectra.
- Single-field Mukhanov–Sasaki evolution for ultra-slow-roll inflationary models.
- Scalar-induced gravitational-wave spectra for radiation domination and early matter domination.
- JAX-compatible models and Jacobians for accelerated, differentiable inference.
- Precomputed bilinear coefficients for fast binned-spectrum reconstruction.
How the model is structured
A calculation composes three explicit pieces: a scalar-perturbation model, a cosmological kernel, and a numerical integrator. This makes it possible to exchange the inflationary physics, thermal history, or integration strategy without rewriting the full pipeline.
Research context
SIGWAY underpins Reconstructing Primordial Curvature Perturbations via Scalar-Induced Gravitational Waves with LISA. The package is a collaborative project with Gabriele Franciolini, Aya Ghaleb, Gabriele Perna, and Mauro Pieroni.