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- Svante Janson, Yannis C. Stamatiou, Malvina Vamvakari
- Random Struct. Algorithms
- 2000

We lower the upper bound for the threshold for random 3-SAT from 4.6011 to 4.596 through two different approaches, both giving the same result. (Assuming the threshold exists, as is generally believed but still not rigorously shown.) In both approaches, we start with a sum over all truth assignments that appears in an upper bound by Kirousis et al. to the… (More)

- Alexis C. Kaporis, Lefteris M. Kirousis, Yannis C. Stamatiou, Malvina Vamvakari, Michele Zito
- Electronic Notes in Discrete Mathematics
- 2001

The problem of determining the unsatisfiability threshold for random 3-SAT formulas consists in determining the clause to variable ratio that marks the experimentally observed abrupt change from almost surely satisfiable formulas to almost surely unsatisfiable. Up to now, there have been rigorously established increasingly better lower and upper bounds to… (More)

The problem of determining the unsatisfiability threshold for random 3-SAT formulas consists in determining the clause to variable ratio that marks the (experimentally observed) abrupt change from almost surely satisfiable formulas to almost surely unsatisfiable. Up to now, there have been rigorously established increasingly better lower and upper bounds to… (More)

- A. Kyriakoussis, Malvina Vamvakari
- Discrete Mathematics
- 2005

In this paper, we present generalization of matching extensions in graphs and we derive combi-natorial interpretation of wide classes of orthogonal and q-orthogonal polynomials. Specifically, we assign general weights to complete graphs, cycles and chains or paths defining matching extensions in these graphs. The generalized matching polynomials of these… (More)

- A. Kyriakoussis, Malvina Vamvakari
- Axioms
- 2014

From Kemp [1], we have a family of confluent q-Chu-Vandermonde distributions, consisted by three members I, II and III, interpreted as a family of q-steady-state distributions from Markov chains. In this article, we provide the moments of the distributions of this family and we establish a continuous limiting behavior for the members I and II, in the sense… (More)

In this article, we a derive an upper bound and an asymptotic formula for the q-binomial, or Gaussian, coefficients. The q-binomial coefficients, that are defined by the expression m n q = 1 − q m 1 − q m−1 · · · ·1 − q m−n+1 1 − q n 1 − q n−1 · · · ·1 − q are a generalization of the binomial coefficients, to which they reduce as q tends toward 1. In this… (More)

- A. Kyriakoussis, Malvina Vamvakari
- Fundam. Inform.
- 2012

- A. Kyriakoussis, Malvina Vamvakari
- Discrete Mathematics
- 1999

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