Below is the ascii version of the abstract for 14-63. The html version should be ready soon.

P. Butera, P. Federbush, M. Pernici
Dimer entropy of a graph and a positivity property
(52K, LaTeX)

ABSTRACT.   The entropy of a monomer-dimer system on an infinite bipartite 
 lattice can be written as a mean-field part plus a series expansion 
 in the dimer density. In a previous paper it has been conjectured 
 that all coefficients of this series are positive. Analogously on a 
 connected regular graph with v vertices, the ``entropy'' of the 
 graph ln N(i)/v, where N(i) is the number of ways of 
 setting down i dimers on the graph, can be written as a part 
 depending only on the count of the dimer configuration over the 
 completed graph plus a Newton series in the dimer density on the 
 graph. In this paper, we investigate for which connected regular 
 graphs all the coefficients of the Newton series are positive (for 
 short, these graphs will be called positive). In the class of 
 connected regular bipartite graphs, up to v=20, all the non 
 positive graphs have vertices of degree 3. From v=14 to v=28, 
 and degree 3, a few violations of the positivity occur, but their 
 frequency decreases with increasing v. We conjecture that 
 for each degree r the frequency of violations, in the class of the 
 r-regular bipartite graphs, goes to zero as v tends to 
 infinity.