By taking into account both quantum mechanical and general relativistic effects, I derive an equation that describes limitations on the measurability of space-time distances as defined by a material reference system. OUTP-96-09-P February 1996

We give characterizations for the (in ZFC unprovable) sentences “Every Σ12–set is measurable” and “Every ∆ 1 2–set is measurable” for various notions of measurability derived from well–known forcing partial orderings.

We obtain upper bounds on the number of sign changes of linear combnatlons of derivatives and convolutions of Plya frequency functions using the variation diminishing properties of totally positive functions. These constitute extensions of earlier results of Karlin and Proschan.