Integrals involving the Heaviside function

*To*: mathgroup at yoda.physics.unc.edu*Subject*: Integrals involving the Heaviside function*From*: Roque Donizete de Oliveira <oliveria at engin.umich.edu>*Date*: Fri, 2 Oct 92 17:26:52 -0400

I need to perform (many) integrals whose simplest example is Integrate[Heaviside[x-2] Exp[-x], {x,0,Infinity}] where Heaviside is the step function (not available in Mma). Does anyone have a suitable Mma implementation of the Heaviside function or suggestion that would allow me to do integrals like the one above ? Manually splitting the interval of integration is not what I want. I need some automated way (my integrands are defined in terms of Heaviside[x], actually Heaviside[y^2 -(x^2 -a^2)], where both x and y are the variables of integration (double integral) and a > 0 ). Thanks for any help. Roque oliveria at caen.engin.umich.edu Nuclear Eng Dept, The University of Michigan