No description available.

No description available.

Roughly speaking, a group G is omnipotent if orders of finitely many elements can be controlled independently in some finite quotients of G. We proved that pi1(S) is omnipotent when S is a surface other than P2,T2 or K2 . This generalizes the fact, previously known, that free groups are omnipotent. The proofs primarily utilize geometric techniques involving graphs of spaces with the aim of retracting certain spaces onto graphs. / Approximativement, on peut dire qu'un groupe G est omnipotent si les ordresquantité d'élements d'une quantite finie d'elements peuvent etre controles independamment dans unquotient fini de Nous avons prouve que 7Ti(5) est omnipotent quand S estune surface autre que P2, T2 ou K2. Cela generalise le fait, deja connu, que lesgroupes libres sont omnipotents. La preuve utilise principalement des techniquesgeometriques impliquant des graphiques d'espaces ayant pour but de retractercertains espaces en graphiques.

We prove that any finitely generated group which splits as a graph of free groups with cyclic edge groups is hyperbolic relative to certain finitely generated subgroups, known as the peripheral subgroups. Each peripheral subgroup splits as a graph of cyclic groups. Any graph of free groups with cyclic edge groups is the fundamental group of a graph of spaces X where vertex spaces are graphs, edge spaces are cylinders and attaching maps are immersions. We approach our theorem geometrically using this graph of spaces. / We apply a "coning-off" process to peripheral subgroups of the universal cover X̃ → X obtaining a space Cone(X̃) in order to prove that Cone (X̃) has a linear isoperimetric function and hence satisfies weak relative hyperbolicity with respect to peripheral subgroups. / We then use a recent characterisation of relative hyperbolicity presented by D.V. Osin to serve as a bridge between our linear isoperimetric function for Cone(X̃) and a complete proof of relative hyperbolicity. This characterisation allows us to utilise geometric properties of X in order to show that pi1( X) has a linear relative isoperimetric function. This property is known to be equivalent to relative hyperbolicity. / Keywords. Relative hyperbolicity; Graphs of free groups with cyclic edge groups, Relative isoperimetric function, Weak relative hyperbolicity.

No description available.

No description available.

Thesis (Ph. D.)--Oregon State University, 2003. / Typescript (photocopy). Includes bibliographical references (leaves 59-60). Also available on the World Wide Web.

Thesis (Ph.D.)--Tufts University, 2001. / Advisers: Mauricio Gutierrez; Zbigniew Nitecki. Submitted to the Dept. of Mathematics. Includes bibliographical references (leaves 73-74). Access restricted to members of the Tufts University community. Also available via the World Wide Web;

Thesis (M.S.)--Brigham Young University. Dept. of Mathematics, 2005. / Includes bibliographical references (p. 98-99).

For various values of n and m we investigate homomorphisms from Out(F_n) to Out(F_m) and from Out(F_n) to GL_m(K), i.e. the free and linear representations of Out(F_n) respectively. By means of a series of arguments revolving around the representation theory of finite symmetric subgroups of Out(F_n) we prove that each homomorphism from Out(F_n) to GL_m(K) factors through the natural map p_n from Out(F_n) to GL(H_1(F_n,Z)) = GL_n(Z) whenever n=3, m < 7 and char(K) is not an element of {2,3}, and whenever n>5, m< n(n+1)/2 and char(K) is not an element of {2,3,...,n+1}. We also construct a new infinite family of linear representations of Out(F_n) (where n > 2), which do not factor through p_n. When n is odd these have the smallest dimension among all known representations of Out(F_n) with this property. Using the above results we establish that the image of every homomorphism from Out(F_n) to Out(F_m) is finite whenever n=3 and n < m < 6, and of cardinality at most 2 whenever n > 5 and n < m < n(n-1)/2. We further show that the image is finite when n(n-1)/2 -1 < m < n(n+1)/2. We also consider the structure of normal finite index subgroups of Out(F_n). If N is such then we prove that if the derived subgroup of the intersection of N with the Torelli subgroup T_n < Out(F_n) contains some term of the lower central series of T_n then the abelianisation of N is finite.