19 research outputs found
Note on the smallest root of the independence polynomial
One can define the independence polynomial of a graph G as follows. Let i(k)(G) denote the number of independent sets of size k of G, where i(0)(G) = 1. Then the independence polynomial of G is I(G,x) = Sigma(n)(k=0)(-1)(k)i(k)(G)x(k). In this paper we give a new proof of the fact that the root of I(G,x) having the smallest modulus is unique and is real
On the growth of deviations
The deviations of a graded algebra are a sequence of integers that determine
the Poincare series of its residue field and arise as the number of generators
of certain DG algebras. In a sense, deviations measure how far a ring is from
being a complete intersection. In this paper we study extremal deviations among
those of algebras with a fixed Hilbert series. In this setting, we prove that,
like the Betti numbers, deviations do not decrease when passing to an initial
ideal and are maximized by the Lex-segment ideal. We also prove that deviations
grow exponentially for Golod rings and for certain quadratic monomial algebras.Comment: Corrected some minor typos in the version published in PAM
A local transform for trace monoids
10 pagesWe introduce a transformation for functions defined on the set of cliques of a trace monoid. We prove an inversion formula related to this transformation. It is applied in a probabilistic context in order to obtain a necessary normalization condition for the probabilistic parameters of invariant processes---a class of probabilistic processes introduced elsewhere, and intended to model an asynchronous and memoryless behavior
Möbius inversion formula for the trace group
A trace group (monoid) is the quotient of a free group (monoid) by relations of commutation between some pairs of generators. We prove an analog for the trace group of the Möbius inversion formula for the trace monoid (Cartier and Foata, 1969)