Elliptic-Hyperbolic Partial Differential Equations

This text is a concise introduction to the partial differential equations which change from elliptic to hyperbolic type across a smooth hypersurface of their domain. These are becoming increasingly important in diverse sub-fields of both applied mathematics and engineering, for example:
 
• The heating of fusion plasmas by electromagnetic waves
• The behaviour of light near a caustic
• Extremal surfac...