What is the "jump condition"?

[sassie]

I've been studying Green's function and I've come across something called the "jump condition". What is the "jump condition" and what it is used for (and perhaps an example)? Cheers.

[HallsofIvy]

It's referring to a "jump" discontinuity where the limits from above and below both exist but are different. For Green's function, I believe the "jump condition" you are talking about is a jump discontinuity in the derivative Gx at x= t.