Peierls bracket

In theoretical physics, the Peierls bracket is an equivalent description^{[clarification needed]} of the Poisson bracket. It can be defined directly from the action and does not require the canonical coordinates and their canonical momenta to be defined in advance.^{[clarification needed]}

The bracket^{[clarification needed]}

${\displaystyle [A,B]}$

is defined as

${\displaystyle D_{A}(B)-D_{B}(A)}$,

as the difference between some kind of action of one quantity on the other, minus the flipped term.

In quantum mechanics, the Peierls bracket becomes a commutator i.e. a Lie bracket.