Thus, κ κ can only be determined up to a transformation κ κ → → λ λ κ κ + ( 1 − − λ λ ) , which is known as the "mass sheet degeneracy." In principle, this degeneracy can be broken if an independent measurement of the magnification is available because the magnification is not invariant under the aforementioned degeneracy transformation. Specifically, μ μ scales with λ λ as μ μ ∝ ∝ λ λ − − 2 .