2026/07/20 by Gabriela Barenboim, Anne-Katherine Burns
Physics and Astronomy · #hep-ph #astro-ph.CO #gr-qc
We map the observational predictions of cosmological stasis in the inflationary gravitational wave background onto the sensitivity bands of current and planned gravitational wave detectors. Using the closed-form piecewise spectral template derived in the companion paper, we generate detectability maps for four stasis scenarios: canonical, dynamical scalar, vacuum-energy/matter, and vacuum-energy/radiation across the frequency bands probed by NANOGrav, SKA, LISA, DECIGO, BBO, the Einstein Telescope, and Cosmic Explorer. For scenarios in which the spectrum is suppressed, ws < 1/3, the stasis feature is detectable by BBO in the region of (ws,ΔN) parameter space in which ws\gtrsim 0.2 for tensor-to-scalar ratios close to the Planck upper limit, r = 0.036. For scenarios in which the spectrum is enhanced, ws > 1/3, the stasis feature is detectable by BBO across the entire (ws,ΔN) parameter space for tensor-to-scalar ratios of O(0.01). We characterize the Standard Model (SM) g_* fine structure of the IGWB, showing that SM phase transitions introduce spectral steps of ≈ 20% (electroweak, at ∼ 2.6×10-6~Hz) and ≈ 53% (QCD, at ∼ 3.6× 10-9~Hz). For stasis scenarios with end-of-stasis temperatures below the QCD scale these steps fall inside the stasis band and constitute additional spectral features that complement the primary signature. Finally, we model the finite-width end-of-stasis transition phenomenologically, demonstrating that the spectral break at fend is smoothed over a log-frequency window ΔNtrans× 3(1+ws)/4, and that the consistency relation C2=C2(α) remains testable provided ΔNstasis≫ ΔNtrans, a condition easily satisfied for all scenarios of phenomenological interest.