Older Babies - More Active Mothers?: How Maternal Labor Supply Changes as the Child Grows

Female labor market activity is dependent on the presence and the age of a child, but how do the determinants develop in magnitude and significance with the child's age? Using German SOEP data from 1991 to 2006 for mothers with young children, the change in maternal labor supply when the child is one, two, and three years old is explicitly addressed. According to the tobit regression results for precise working hours, maternal labor supply becomes increasingly responsive to economic incentives - mainly to imputed wages - as the child grows.Female labor supply, childbirth, parental leave

Majorana solution of the Thomas-Fermi equation

We report on an original method, due to Majorana, leading to a semi-analytical series solution of the Thomas-Fermi equation, with appropriate boundary conditions, in terms of only one quadrature. We also deduce a general formula for such a solution which avoids numerical integration, but is expressed in terms of the roots of a given polynomial equation.Comment: RevTex, 5 pages, 1 figur

Three tests of general relativity via Fermat's principle and the phase of Bessel functions

Fermat's principle applied to a flat metric in the plane yields the phase of a Bessel function in the periodic domain for a constant index of refraction. Gravitational forces cause the index of refraction to vary and lead to a modified phase of the Bessel function. A distinction is made between the forces that cause acceleration: the gravitational force affects the optical properties of the medium whereas the centrifugal force does not, the latter being built into the phase of oscillations of the Bessel function. The time delay in radar echoes from planets is determined from Fermat's principle where the velocity of light is the phase velocity and the index of refraction varies on account of the gravitational potential. The deflection of light by a massive body is shown to be produced by a quadrupole interaction, and the perihelion shift requires both the gravitational potential, producing a closed orbit, and the quadrupole, causing the perihelion to rotate.Comment: 16 page