Coupling to
-spin variables
s
(l) located on edges
l
was considered by Ambjørn et al [15], who added a Wilson loop term
to the action. The matter sector behaves largely as expected
when
is varied between the crumpled and the elongated gravity phase.
However, in the common critical region of both sectors, where
a priori
one might have expected interesting effects, the critical
behaviour seems to agree with that of the pure gravity
system.
More recently, Bilke et al [52] have reported a non-trivial back-reaction of matter on
geometry, when considering coupling to several non-compact
U
(1)-gauge fields. Their study was in part motivated by a
continuum analysis of the dynamics of the conformal factor of
Antoniadis et al [21]. Including three fields
U
(1)-fields seems to lead to a total suppression of the branched
polymer phase, which is replaced by a new weak-coupling phase
with negative susceptibility exponent
and a fractal dimension
. These are clearly interesting results, but should be treated
with some caution because of the small lattice sizes involved (
).
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Discrete Approaches to Quantum Gravity in Four Dimensions
Renate Loll http://www.livingreviews.org/lrr-1998-13 © Max-Planck-Gesellschaft. ISSN 1433-8351 Problems/Comments to livrev@aei-potsdam.mpg.de |