a finite group g is said to be a pos-group if for each x in g the cardinality of the set {y in g | o(y) = o(x)} is a divisor of the order of g. in this paper we study the structure of pos-groups with some cyclic sylow subgroups.

‎in this paper we give a characterization of unmixed tripartite‎ ‎graphs under certain conditions which is a generalization of a‎ ‎result of villarreal on bipartite graphs‎. ‎for bipartite graphs two‎ ‎different characterizations were given by ravindra and villarreal‎. ‎we show that these two characterizations imply each other‎.

a finite group g is said to be a pos-group if for each x in g the cardinality of the set {y in g | o(y) = o(x)} is a divisor of the order of g. in this paper we study the structure of pos-groups with some cyclic sylow subgroups.

The theory of incomplete contracts has been recently questioned using or extending the subgame perfect implementation approach of Moore and Repullo (1988). We consider the robustness of this mechanism to the introduction of small amounts of asymmetric information. Our main result is that the mechanism may not yield (even approximately) truthful revelation as the amount of asymmetric information...

A lattice Delaunay polytope D is called perfect if it has the property that there is a unique circumscribing ellipsoid with interior free of lattice points, and with the surface containing only those lattice points that are the vertices of D. An inhomogeneous quadratic form is called perfect if it is determined by such a circumscribing ”empty ellipsoid” uniquely up to a scale factorComplete pro...

We call n a near-perfect number if n is the sum of all of its proper divisors, except for one of them, which we term the redundant divisor. For example, the representation 12 = 1 + 2 + 3 + 6 shows that 12 is near-perfect with redundant divisor 4. Near-perfect numbers are thus a very special class of pseudoperfect numbers, as defined by Sierpiński. We discuss some rules for generating near-perfe...

A graph G is clique-perfect if the cardinality of a maximum cliqueindependent set of H is equal to the cardinality of a minimum cliquetransversal of H, for every induced subgraph H of G. When equality holds for every clique subgraph of G, the graph is c–clique-perfect. A graph G is K-perfect when its clique graph K(G) is perfect. In this work, relations are described among the classes of perfec...

Perfect lattice actions are exiting with several respects: they provide new insight into conceptual questions of the lattice regularization, and quasi-perfect actions could enable a great leap forward in the non-perturbative solution of QCD. We try to transmit a flavor of them, also beyond the lattice community.