R < 0.01 Tensor Limit

The tensor-to-scalar ratio r quantifies the amplitude of primordial gravitational waves relative to the scalar density perturbations in the CMB. Inflationary models generically predict a nonzero r, with the simplest large-field models predicting r ~ 0.1–0.2. The BICEP/Keck series of experiments has constrained r < 0.036 at 95% confidence, and combined analyses with Planck CMB data push the limit to r < 0.032. This increasingly tight upper limit has ruled out or severely constrained many of the simplest inflationary models, creating a growing tension between the theoretical preference for detecting a gravitational wave background from inflation and the observational constraint that it must be extremely small. Models that survive predict r at the level of 0.001–0.01, right at the edge of next-generation detector sensitivity.

Successive Collision Theory predicts a tensor-to-scalar ratio that is naturally small — consistent with the current upper limits — without requiring fine-tuned inflation models, because SCT does not invoke inflation at all. In SCT, the large-scale uniformity of the CMB is explained by the simultaneous thermalization of the entire collision overlap volume, not by exponential inflationary expansion. There is therefore no epoch of accelerated expansion that amplifies quantum vacuum fluctuations into a classical tensor spectrum — the mechanism that produces a large r in inflationary models. Instead, the tensor perturbations in SCT arise from two physically smaller sources: the gravitational wave emission from the collision event itself, which deposits tensor modes at frequencies set by the pocket dimensions and collision velocity, and the ongoing tensor mesh dissipation from frame orbital decay at all hierarchy levels.

The tensor modes from the SCT collision event are set by the characteristic frequencies of the pocket collision — wavelengths comparable to the pocket dimensions, which are far larger than our Hubble radius and therefore project onto very long-wavelength, unobservably small-amplitude tensor modes at CMB scales. The tensor mesh dissipation contribution at cosmological scales is suppressed by the slow rate of orbital decay relative to the Hubble rate, producing r values well below the current upper limits. SCT therefore predicts r in the range of 10⁻⁴ to 10⁻³ — far below inflationary predictions but above absolute zero, placing the signal within the sensitivity range of ultimate-sensitivity CMB experiments such as CMB-S4 and LiteBIRD. Detecting this very small but nonzero r would distinguish SCT from models where no tensor background is produced.