title: 
Variational principles on polyhedral surfaces

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abstract: We will discuss some of the recent work on variational
principles associated to polyhedral surfaces. These include the
work of Colin de Verdiere, Rivin, Leibon and few others. The
relationship 2-dimensional variational principles, the cosine law,
the 3-dimensional hyperbolic geometry and the Schlaefli formula
will be addressed in details.