Pulsar Timing Residuals as a Bound on Bounce Shear

This paper converts the hundred-nanosecond timing stability of the best millisecond pulsars into an explicit bound on a steady shear rate, compares that bound with the shear ceiling implied by the density bound of a bounced cosmology, and determines which bounce variants pulsar timing can and cannot reach. The headline results are as follows. Shear-rate bound from a 100 ns residual over 10 years: 6.02e-24 per s; Equivalent dimensionless shear accumulated over 10 years: 1.9e-15; Ratio of the timing shear bound to the present expansion rate: 2.76e-06; Bounce shear-rate ceiling from the density bound: 8.05e+23 per s; Residual a shear at one part in a billion of the ceiling would produce in 10 years: 1.34e+31 s; Baseline needed to reach a shear of one part in a trillion of the ceiling: 2.74e-17 yr. All values are computed from the stated assumptions and published inputs; the study is simulated and computed, not measured.