Cancelling out systematic uncertainties
  We present a method to minimize, or even cancel out, the nuisance parameters
affecting a measurement. Our approach is general and can be applied to any
experiment or observation. We compare it with the bayesian technique used to
deal with nuisance parameters: marginalization, and show how the method
compares and improves by avoiding biases. We illustrate the method with several
examples taken from the astrophysics and cosmology world: baryonic acoustic
oscillations, cosmic clocks, Supernova Type Ia luminosity distance, neutrino
oscillations and dark matter detection. By applying the method we recover some
known results but also find some interesting new ones. For baryonic acoustic
oscillation (BAO) experiments we show how to combine radial and angular BAO
measurements in order to completely eliminate the dependence on the sound
horizon at radiation drag. In the case of exploiting SN1a as standard candles
we show how the uncertainty in the luminosity distance by a second parameter
modeled as a metallicity dependence can be eliminated or greatly reduced. When
using cosmic clocks to measure the expansion rate of the universe, we
demonstrate how a particular combination of observables nearly removes the
metallicity dependence of the galaxy on determining differential ages, thus
removing the age-metallicity degeneracy in stellar populations. We hope that
these findings will be useful in future surveys to obtain robust constraints on
the dark energy equation of state.
