English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Global: Zendy Plus monthly

We examine the reduced density matrix of the centre of mass on position basisconsidering a one-dimensional system of $N$ non-interacting distinguishableparticles in a infinitely deep square potential well. We find a class of purestates of the system for which the off-diagonal elements of the matrix above goto zero as $N$ increases. This property holds too for the state vectors whichare factorized in the single particle wave functions. In this last case, if theaverage energy of each particle is less than a common bound, the diagonalelements are distributed according to the normal law with a mean squaredeviation which becomes smaller and smaller as $N$ increases towards infinity.Therefore when the state vectors are of the type considered we cannotexperience spatial superpositions of the centre of mass and we may concludethat position is a preferred basis for the collective variable.Comment: 11 pages, Latex, no figures. To appear on Foundations of Physics  Letter

On the Spatial Density Matrix for the Centre of Mass of a one dimensional Perfect Gas