Cauchy vs. Dirichelt/Neumann Condition for PDE

[ginarific]

Hi,

Can anybody tell me the difference between a Cauchy Boundary condition and a combined Dirichlet/Neumann Boundary Condition for PDEs?

The reason why I'm asking is because Cauchy boundary conditions can be used to solve Open Hyperbolic PDEs, whereas Dirichlet/Neumann can only be used to solve Elliptic and Parabolic PDEs.

My textbook says:

Cauchy Conditions: have u and du/dn given on C

Dirichlet Conditions: have u given on C

Neumann Conditions: du/dn given on C

So if you have a combination of Dirichlet and Neumann conditions, is that a Cauchy condition?

Any help would be much appreciated!

Thanks,
Gina

[velvexor]

If it helps at all, I think I've seen some discussion on these BC's in Susskind's String Theory Lectures (http://youtu.be/-BleG7PBwEA).