Abstract:Année de publication : 1999
A random Eulerian triangulation is a random triangulation where an {\it even} number of triangles meet at any given vertex. We argue that the central charge increases by one if the fully packed $O(n)$ model is defined on a random Eulerian triangulation instead of an ordinary random triangulation. Considering the case $n\rightarrow 0$, this implies that the system of random Eulerian triangulations equipped with Hamiltonian cycles describes a $c=-1$ matter field coupled to 2D quantum gravity as opposed to the system of usual random triangulations equipped with Hamiltonian cycles which has $c=-2$. Hence, in this case one should see a change in the entropy exponent from the value $\gamma=-1$ to the {\it irrational} value $\gamma=\frac{-1-\sqrt{13}}{6}$ when going from a usual random triangulation to an Eulerian one. A direct enumeration of configurations confirms this change in $\gamma$.
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