The existence of additive conserved quantities implies, as is well known, unavoidable deviations from the ideal von Neumann scheme in the measurement of those observables which do not commute with the conserved quantities. We introduce a formal procedure which allows the derivation of a lower...

The bid and ask curves give the demand and supply prices as functions of the instantaneously traded volume. The aim of this paper is the definition, interpretation and intraday analysis of such bid-ask curves. We provide some illustrations from the Paris Bourse quote by quote data.