New posts in Hilbert Space

Equivalent definitions of total angular momentum

Interpretation of density matrix

Is idempotency, $\rho^2=\rho$, a necessary and sufficient condition for $\rho$ to be a pure state?

Why can't every quantum state be expressed as a density matrix/operator?

Do infinite dimensional systems make sense?

Can the Hamiltonian operator act on a bra, if it was once acting on a ket?

What is the link between the rotating wave approximation and the algebraic representation of a dynamical system?

How does an outer product really work?

In a spherically symmetric central potential why do we look for eigenfunctions of the angular momentum operator?

What is the difference between a Hilbert space of state vectors and a Hilbert space of square integrable wave functions?