Physics Letters B 761 (2016) 462–468
Contents lists available at ScienceDirect
Physics Letters B
www.elsevier.com/locate/physletb
Classical electrodynamics in a space with spin noncommutativity
of coordinates
V.M. Vasyuta
∗
, V.M. Tkachuk
Department for Theoretical Physics, Ivan Franko National University of Lviv, 12, Drahomanov St., Lviv, UA-79005, Ukraine
a r t i c l e i n f o a b s t r a c t
Article history:
Received
19 July 2016
Accepted
1 September 2016
Available
online 6 September 2016
Editor:
N. Lambert
Keywords:
Noncommutativity
Electromagnetic
field
We propose a relativistic Lorentz-invariant spin-noncommutative algebra. Using the Weyl ordering of
noncommutative position operators, we find a mapping from a space of commutative functions into space
of noncommutative functions. The Lagrange function of an electromagnetic field in the space with spin
noncommutativity is constructed. In such a space electromagnetic field becomes non-abelian. Agauge
transformation law of this field is also obtained. Exact nonlinear field equations of noncommutative
electromagnetic field are derived from the least action principle. Within the perturbative approach we
consider field of a point charge in a constant magnetic field and interaction of two plane waves. An exact
solution of a plane wave propagation in a constant magnetic and electric fields is found.
© 2016 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. Introduction
Noncommutativity of position operators appears in string the-
ory
[1,2] and quantum gravity [3]. In [2] it was shown that coordi-
nates
on D-brane in a constant Neveu–Schwarz B-field satisfy the
following commutation relations
[X
i
, X
j
]=iθ
ij
, (1)
where θ
ij
is a constant antisymmetric tensor. This type of noncom-
mutativity
is called canonical noncommutativity. The same non-
commutativity
appears in compactifying the IKKT M-theory [1].
In quantum gravity the noncommutativity can be thought of as
a phenomenological effect from quantum space–time, which in-
corporates
the notion of the minimal length into ordinary physics.
Moreover, noncommutativity arises even in the pure classical me-
chanics.
It can be shown that coordinates of a charged particle
with a small mass in a strong magnetic field do not commute (the
corresponding Poisson bracket is non-zero) [4,5].
It
is interesting that, decades before string theory, in search-
ing
for a generalization of the ordinary commutation relations
between the operators of dynamical variables Snyder developed a
noncommutative Lorentz-invariant algebra of the following form
[X
μ
, X
ν
]=il
2
L
μν
, (2)
*
Corresponding author.
E-mail
addresses: waswasiuta@gmail.com (V.M. Vasyuta), voltkachuk@gmail.com
(V.M. Tkachuk).
where L
μν
are generators of the Lorentz rotation group, l is a small
parameter [6,7].
One
of the biggest problems of canonical noncommutativity (1)
with
a constant right-hand part of coordinate commutator is a vi-
olation
of a rotational symmetry and as a consequence existing of
a chosen direction.
Rotational
invariance (or more widely Lorentz-invariance) can
be restored in noncommutative spaces by replacing constants θ
ij
with some more complicated objects. There are already several ro-
tational
(Lorentz) invariant noncommutative algebras. First of all,
the above-mentioned Snyder algebra is Lorentz-invariant (2). The
other example of such an algebra can be built by assuming that
θ
ij
are operators commuting with each other and transforming as
components of tensor [3]. Objects θ
ij
can be composed from some
additional degrees of freedom. In this way by using coordinates of
an additional harmonic oscillator rotational invariant noncommu-
tativity
was introduced in [8,9].
Recently ,
there were proposed several rotational invariant non-
commutativities,
where coordinate commutators are postulated to
be proportional to some functions of spin operators. These algebras
are known in literature as spin noncommutativity or noncommu-
tativity
due to spin.
In
[10] the following algebra with spin noncommutativity was
proposed
X
i
, X
j
=
i
¯
hθ
2
ε
ijk
s
k
,
X
i
, P
j
=
i
¯
hδ
ij
,
P
i
, P
j
=
0,
s
i
, s
j
=
i
¯
hε
ijk
s
k
,
X
i
, s
j
=
i
¯
hθ ε
ijk
s
k
,
(3)
http://dx.doi.org/10.1016/j.physletb.2016.09.001
0370-2693/
© 2016 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
.