Ultra-hyperbolic pde and F theory

1. Aug 19, 2014

MathematicalPhysicist

Is there a conncetion between Fritz john's ultra-hyperbolic pde, which is the equation:

$$u_{tt}+u_{\tau \tau} = u_{xx}+u_{yy}$$

I mean F theory has another dimension of time, and the above pde has also another time variable with regards to the simple wave pde.

Any literature on this?

Thanks.

2. Aug 20, 2014

MathematicalPhysicist

Btw, any introductory books in the net regarding F theory?, I don't mind 800-1000 pages books... :-D