Physics Letters B 781 (2018) 312–315
Contents lists available at ScienceDirect
Physics Letters B
www.elsevier.com/locate/physletb
Contact geometry and quantum mechanics
Gabriel Herczeg
a
, Andrew Waldron
b,∗
a
Department of Physics, University of California, Davis, CA 95616, USA
b
Center for Quantum Mathematics and Physics (QMAP), Department of Mathematics, University of California, Davis, CA 95616, USA
a r t i c l e i n f o a b s t r a c t
Article history:
Received
21 March 2018
Received
in revised form 3 April 2018
Accepted
5 April 2018
Available
online 6 April 2018
Editor:
M. Cveti
ˇ
c
We present a generally covariant approach to quantum mechanics in which generalized positions,
momenta and time variables are treated as coordinates on a fundamental “phase-spacetime”. We show
that this covariant starting point makes quantization into a purely geometric flatness condition. This
makes quantum mechanics purely geometric, and possibly even topological. Our approach is especially
useful for time-dependent problems and systems subject to ambiguities in choices of clock or observer.
As a byproduct, we give a derivation and generalization of the Wigner functions of standard quantum
mechanics.
© 2018 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license
(http://creativecommons.org/licenses/by/4.0/). Funded by SCOAP
3
.
1. Contact geometry
Mechanics is usually formulated in terms of an even 2n-dimen-
sional
phase-space (or symplectic manifold) with time treated as
an external parameter and dynamics determined by a choice of
Hamiltonian. Yet classical physics ought not depend on choices
of clocks. However, Einstein’s principle of general covariance can
be applied to this situation by introducing an odd (2n + 1)-
dimensional
phase-spacetime manifold Z . Dynamics is now en-
coded
by giving Z a (strict) contact structure—i.e., a one-form α
subject to a non-degeneracy condition on the (phase-spacetime)
volume form:
Vol
α
:= α ∧ (dα)
∧n
= 0 . (1.1)
Physical phase-spacetime trajectories γ are determined by extrem-
izing
the action
S =
γ
α . (1.2)
Since the integral of a one-form along a path γ is a coordinate
invariant quantity, general covariance (both worldline and target
space) is built in from the beginning [1]. The equations of motion
are
*
Corresponding author.
E-mail
addresses: Herczeg @ms .physics .ucdavis .edu (G. Herczeg),
wally @math .ucdavis .edu (A. Waldron).
ϕ(
˙
γ ,
·
) = 0 , (1.3)
where the two-form ϕ := dα is maximal rank by virtue of Eq. (1.1)
and
˙
γ is a tangent vector to the path γ in Z .
The
structure (Z , α) is called a (strict) contact geometry and
Eq. (1.3)determines its Reeb dynamics [2]. In addition to general
covariance, this formulation of mechanics enjoys a Darboux theo-
rem,
which implies the existence of local coordinates (ψ, π
A
, χ
A
)
such that α = π
A
dχ
A
− dψ (where A = 1, ..., n) that trivialize the
dynamics. Hence one might hope to treat classical and quantum
mechanics as contact topology problems.
2. Goal
We aim to develop a generally phase-spacetime covariant for-
mulation
of quantum mechanics. We find a formulation of quan-
tum
mechanics in terms of intrinsic geometric structures on a con-
tact
manifold. Our approach is similar to Fedosov’s quantization of
symplectic manifolds [3], and indeed we were partly inspired by
that work and subsequent applications of Fedosov quantization to
models of higher spins [4]. Quantization based on contact geom-
etry
has been studied before: For example, Rajeev [5] considers
quantization beginning with (classical) Lagrange brackets (the con-
tact
analog of Poisson brackets). Fitzpatrick [6] has extended this
work to a rigorous geometric quantization setting. There is also
earlier work by Kashiwara [7] that studies sheaves of pseudodiffer-
ential
operators over contact manifolds. Investigations motivated
by quantum cosmology of the so-called “clock ambiguity” in the
quantum dynamics of time reparameterization invariant theories
may be found in [8]. Contact geometry has also been employed in
studies of choices of quantum clocks in [9].
https://doi.org/10.1016/j.physletb.2018.04.008
0370-2693/
© 2018 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). Funded by
SCOAP
3
.