Before revision: We study no arbitrage conditions for financial models in which either the stocks itself or its log returns are continuous Ito processes. More precisely , we derive deterministic conditions for the existence and nonexistence of equivalent (local) martingale measures and strict martingale densities.
After revision: We derive integral tests for the existence and absence of arbitrage in a financial market with one risky asset which is either modeled as stochastic exponential of an Ito process or a positive diffusion with Markov switching. In particular , we derive deterministic conditions for the existence and nonexistence of equivalent (local) martingale measures and strict martingale densities.