A Vacuum-Gradient Microbalance: Torsion Readout of Vacuum Energy Density Gradients with a Computed Force Floor

If vacuum energy density varies in space, its gradient exerts a force on matter, and the instrument for that force is a torsion balance pushed to its thermal limit. This paper specifies a vacuum-gradient microbalance: a torsion pendulum of constant 1.0e-8 newton metres per radian whose test body is cycled between two vacuum landscapes defined by movable boundary plates. The computed thermal force noise is 1.44e-14 newtons per root hertz and the readout contribution 2.00e-16, giving a combined force floor of 1.44e-14 newtons per root hertz and, for a one-cubic-centimetre test body, a minimum detectable vacuum energy density gradient of 1.44e-08 joules per quartic metre per root hertz. The corresponding acceleration floor for a ten-gram test mass is 1.44e-12 metres per second squared per root hertz. SIMULATED, NOT MEASURED: all figures are computed from stated assumptions.