Abstract
For a graph G = (V,E) and x: E → ℜ+ satisfying Σ e∋υ x e = 1 for each υ ∈ V, set h(x) = Σ e x e log(1/x e ) (with log = log2). We show that for any n-vertex G, random (not necessarily uniform) perfect matching f satisfying a mild technical condition, and x e =Pr(e∈f),
(where H is binary entropy). This implies a similar bound for random Hamiltonian cycles.
Specializing these bounds completes a proof, begun in [6], of a quite precise determination of the numbers of perfect matchings and Hamiltonian cycles in Dirac graphs (graphs with minimum degree at least n/2) in terms of h(G):=maxΣ e x e log(1/x e ) (the maximum over x as above). For instance, for the number, Ψ(G), of Hamiltonian cycles in such a G, we have
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References
N. Alon and S. Friedland: The maximum number of perfect machings in graphs with a given degree sequence, Elec. J. Combinatorics 15 (2008), #N13.
L. Brégman: Some properties of nonnegative matrices and their permanents, Math. Doklady 14 (1973), 945–949.
F. R. K. Chung, P. Frankl, R. Graham and J. B. Shearer: Some intersection theorems for ordered sets and graphs, J. Combin. Theory Ser. A 48 (1986), 23–37.
I. Csiszár and J. Körner: Information theory. Coding theorems for discrete memoryless systems; Akadémiai Kiadó, Budapest, 1981.
B. Cuckler: Hamiltonian cycles in regular tournaments and Dirac graphs, Ph.D. thesis, Rutgers University, 2006.
B. Cuckler and J. Kahn: Hamiltonian cycles in Dirac graphs, Combinatorica 29(3) (2009), 299–326.
G. A. Dirac: Some theorems on abstract graphs, Proc. London Math. Soc., Third Series 2 (1952), 69–81.
G. P. Egorychev: Permanents (Russian), Krasnoyarsk, SFU, 2007.
J. Kahn: An entropy approach to the hard-core model on bipartite graphs, Combinatorics, Probability and Computing 10 (2001), 219–237.
R. J. McEliece: The theory of information and coding, Addison-Wesley, London, 1977.
J. Radhakrishnan: An entropy proof of Bregman’s Theorem, J. Combin. Theory Ser. A 77 (1997), 161–164.
G. Sárközy, S. Selkow and E. Szemerédi: On the number of Hamiltonian cycles in Dirac graphs, Discrete Math. 265 (2003), 237–250.
A. Schrijver: A short proof of Minc’s conjecture, J. Combin. Theory Ser. A 25(1) (1978), 80–83.
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Cuckler, B., Kahn, J. Entropy bounds for perfect matchings and Hamiltonian cycles. Combinatorica 29, 327–335 (2009). https://doi.org/10.1007/s00493-009-2366-9
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DOI: https://doi.org/10.1007/s00493-009-2366-9