In Merton and Samuelson (1974, pp. 85-92).
it was shown that the continuous-trading solution will be a valid asymptotic
approximation to the discrete-trading solution provided that the dynamics have
continuous sample paths. Under these same discrete-trading conditions, the
returns on the Black-Scholcs ‘no-risk’ arbitrage portfolio will have some risk.
However, the magnitude or this risk will be a bounded, continuous function of
the trading interval length, and the risk will go to zero as the trading interval goes
to its continuous limit. Thus, provided that the interval length is not ‘too large’,
the difference between the Black-Scholes continuous-trading option price and
the ‘correct’, discrete-trading price cannot dill& by much without creating a
‘virtual’ arbitrage possibility.