No arbitrage for a special class of filtration expansions

This paper provides a set of sufficient conditions for special classes of filtration expansions, such that the expanded information introduces no new arbitrage opportunities into a market. The information expansion corresponds to knowledge of the “true” price process. The theorem is based on comparing two distinct markets—the original and a fictitious—each associated with a different filtration, and employs the first fundamental theorem of asset pricing in both of these two markets.