Abel 1826 tautochrone problem: phi(x) = integral_0^x f(t)/sqrt(x-t) dt; fractional half-derivative; used in tomography (Abel inversion) + image-reconstruction.
Abel 1826 tautochrone problem: phi(x) = integral_0^x f(t)/sqrt(x-t) dt; fractional half-derivative; used in tomography (Abel inversion) + image-reconstruction.