Cross-correlation tomography: measuring dark energy evolution with weak lensing.

A cross-correlation technique of lensing tomography is developed to probe dark energy in the Universe. The variation of weak shear with redshift around foreground galaxies depends only on the angular distances and is robust to the dominant systematic error in lensing. We estimate the margin-alized accuracies that deep lensing surveys with photometric redshifts can provide on the dark energy density Omega(de), the equation of state parameter w, and its evolution w('): sigma(w) approximately equal 0.01f(-1/2)(sky) and sigma(w(')) approximately equal 0.03f(-1/2)(sky), where a prior of sigma(Omega(de))=0.03 is assumed in the marginalization.