Complex extension of quantum mechanics
Abstract:
This talk examines Hamiltonians H that are not Hermitian but
do exhibit space-time reflection (PT) symmetry. If the (PT)
symmetry of H is not spontaneously broken, then the spectrum of
H is entirely real and positive. Examples of PT-symmetric
non-Hermitian Hamiltonians are H = p2 + ix3
and H = p2 - x4. The apparent
shortcoming of quantum theories arising from PT-symmetric Hamiltonians
is that the PT norm is not positive definite. This suggests that
it may be difficult to develop a quantum theory based on such Hamiltonians.
In this talk it is shown that these difficulties can be overcome by introducing
a previously unnoticed underlying physical symmetry C of Hamiltonians
having an unbroken PT symmetry. Using C, it is shown how
to construct an inner product whose associated norm is positive
definite. The result is a new class of fully consistent complex quantum
theories. Observables in these theories exhibit CPT symmetry, probabilities
are positive, and the dynamics is governed by unitary time evolution.