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For decades, H0 and q0 were the quest of cosmology, as they promised to characterize our “world model” without reference to a specific cosmological framework. Using Monte Carlo simulations, we show that q0 cannot be directly measured using distance indicators with both accuracy (without offset away from its true value) and precision (small error bar). While H0 can be measured with accuracy and precision, to avoid a small bias in its direct measurement (of order 5%) we demonstrate that the pair H0 and ΩM (assuming flatness and w = −1) is a better choice of two parameters, even if our world model is not precisely ΛCDM. We illustrate this with analysis of the Constitution set of supernovae and indirectly infer q0 = −0.57±−0.04. Finally, we show that it may be possible to directly determine q0 with both accuracy and precision using the time dependence of redshifts (“redshift drift”). [ABSTRACT FROM AUTHOR]

The thermal noise associated with mechanical dissipation is a ubiquitous limitation to the sensitivity of precision experiments ranging from frequency stabilization to gravitational wave interferometry. We report on the thermal noise limits to the performance of 1 gm mirror oscillators that are part of a cavity optomechanics experiment to observe quantum radiation pressure noise. Thermal noise limits the observed cavity displacement spectrum from 80 Hz to 5 kHz. We present a calculation of the thermal noise, based on finite element analysis of the dissipation due to structural damping, and find it to be in excellent agreement with the experimental result. We conclude with the predicted thermal noise for an improved oscillator design, which should be capable of revealing the noise that arises from quantum backaction in this system. [ABSTRACT FROM AUTHOR]