We construct and study market models admitting optimal arbitrage. We say that
a model admits optimal arbitrage if it is possible, in a zero-interest rate
setting, starting with an initial wealth of 1 and using only positive
portfolios, to superreplicate a constant c>1. The optimal arbitrage strategy is
the strategy for which this constant has the highest possible value. Our
definition of optimal arbitrage is similar to the one in Fernholz and Karatzas
(2010), where optimal relative arbitrage with respect to the market portfolio
is studied. In this work we present a systematic method to construct market
models where the optimal arbitrage strategy exists and is known explicitly. We
then develop several new examples of market models with arbitrage, which are
based on economic agents' views concerning the impossibility of certain events
rather than ad hoc constructions. We also explore the concept of fragility of
arbitrage introduced in Guasoni and Rasonyi (2012), and provide new examples of
arbitrage models which are not fragile in this sense