  We give a new, flow-type convex program describing equilibrium solutions to
linear Arrow-Debreu markets. Whereas convex formulations were previously known
[Nenakov, Primak 83; Jain 07; Cornet '89], our program exhibits several new
features. It gives a simple necessary and sufficient condition and a concise
proof of the existence and rationality of equilibria, settling an open question
raised by Vazirani. As a consequence we also obtain a simple new proof of
Mertens's result that the equilibrium prices form a convex polyhedral set.

Data Structures and Algorithms;Computer Science and Game Theory