Green’s Functions at Zero Temperature

Abstract

When we discussed one-particle states in the second quantization representation, from the formally mathematical point of view any complete set of functions dependent on the coordinates (spin, etc.) of one particle would work. But from the point of view of physics it is not so: the set must be chosen in a “physically reasonable way.” That is, since we virtually never can solve our equations exactly and can not always provide an “epsilon-delta” -style estimate of the approximations involved, the initial setup must be as close as possible to the solution that we are striving to reach.

Article Note

Men say that the Bodhisat Himself drew it with grains of rice upon dust, to teach His disciples the cause of things. Many ages have crystallized it into a most wonderful convention crowded with hundreds of little figures whose every line carries a meaning. Rudyard Kipling. “Kim.”