Arbitrage and hedging in model-independent markets with frictions

We provide a fundamental theorem of asset pricing and a superhedging theorem for a model indepen- dent discrete time financial market with proportional transaction costs. We consider a probability- free version of the robust no arbitrage condition introduced by Schachermayer in [Math. Finance, 14 (2004), pp. 1948] and show that this is equivalent to the existence of consistent price systems. More- over, we prove that the superhedging price for a claim g coincides with the frictionless superhedging price of g for a suitable process in the bid-ask spread.