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The g Function Values of Groups with Order 4p2  [PDF]
ZHANG Ning,CAO Hong-ping
Journal of Chongqing Normal University , 2010,
Abstract: Let be a finite group and be a positive integer, let . If and are two finite groups, , ,then and are groups that their order types are same. In this article we discuss a problem in relation to Thompson supposition, it is that when two finite groups with same order type ,they are isomorphic or not, and we define g(G) as the g function value of finite group ,it represents the number of isomorphic classes that groups with the same order type to . In this article we obtain the order type of groups with order by computing their constructions, and obtain their g function values. Particularly, we get a pair of groups with order ,whose order types are same and g function values are two, that is, there are two unisomorphic groups with order ,their order types are same.Here p is an odd prime number.
A Family of fusion systems related to the groups $\mathrm{Sp}_4(p^a)$ and $\mathrm{G}_2(p^a)$  [PDF]
Christopher Parker,Gernot Stroth
Mathematics , 2014,
Abstract: A family of exotic fusion systems generalizing the group fusion systems on Sylow $p$-subgroups of $\mathrm{G}_2(p^a)$ and $\mathrm{Sp}_4(p^a)$ is constructed.
Notes on affine isometric actions of discrete groups  [PDF]
Yurii A. Neretin
Mathematics , 1997,
Abstract: Consider a lattice $\Gamma$ in a group $G = SL_2(\R), SO(1,n), SU(1,n)$, $SL_2(\Q_p)$. We discuss actions of $\Gamma$ by affine isometric transformations of Hilbert spaces. We show that for irreducible affine isometric action of $G$ its restriction to $\Gamma$ is irreducible. We prove the existence of canonical irreducible affine isometric actions of $\Gamma$ associated to actions of $\Gamma$ on $\R$- trees. Using such actions we construct irreducible representations of semigroup of probabilistic measures on $\Gamma$ and construct the series of representations of the groups of diffeomorphisms of Riemann surfaces enumerated by the points of Thurston compactification of Teichm\"uller (Teichmuller) space.
Free actions on handlebodies  [PDF]
Darryl McCullough,Marcus Wanderley
Mathematics , 2001,
Abstract: The equivalence (or weak equivalence) classes of orientation-preserving free actions of a finite group G on an orientable 3-dimensional handlebody of genus g can be enumerated in terms of sets of generators of G. They correspond to the equivalence classes of generating n-vectors of elements of G, where n=1+(g-1)/|G|, under Nielsen equivalence (or weak Nielsen equivalence). For abelian and dihedral G, this allows a complete determination of the equivalence and weak equivalence classes of actions for all genera. Additional information is obtained for solvable groups and for the groups PSL(2,3^p) with p prime. For all G, there is only one equivalence class of actions on the genus g handlebody if g is at least 1+r(G)|G|, where r(G) is the maximal length of a chain of subgroups of G. There is a stabilization process that sends an equivalence class of actions to an equivalence class of actions on a higher genus, and some results about its effects are obtained.
Finitely Generated Groups $G$ such that $G/Z(G) \simeq C_p \times C_p$  [PDF]
Mariana Cornelissen,César Polcino Milies
Mathematics , 2012,
Abstract: Finite groups $G$ such that $G/Z(G) \simeq C_2 \times C_2$ where $C_2$ denotes a cyclic group of order 2 and $Z(G)$ is the center of $G$ were studied in \cite{casofinito} and were used to classify finite loops with alternative loop algebras. In this paper we extend this result to finitely generated groups such that $G/Z(G) \simeq C_p \times C_p$ where $C_p$ denotes a cyclic group of prime order $p$ and provide an explicit description of all such groups.
Large p-groups actions with a p-elementary abelian second ramification group  [PDF]
Magali Rocher
Mathematics , 2008,
Abstract: Let $k$ be an algebraically closed field of characteristic $p>0$ and $C$ a connected nonsingular projective curve over $k$ with genus $g \geq 2$. Let $(C,G)$ be a "big action", i.e. a pair $(C,G)$ where $G$ is a $p$-subgroup of the $k$-automorphism group of $C$ such that$\frac{|G|}{g} >\frac{2 p}{p-1}$. We denote by $G_2$ the second ramification group of $G$ at the unique ramification point of the cover $C \to C/G$. The aim of this paper is to describe the big actions whose $G_2$ is $p$-elementary abelian. In particular, we obtain a structure theorem by considering the $k$-algebra generated by the additive polynomials. We more specifically explore the case where there is a maximal number of jumps in the ramification filtration of $G_2$. In this case, we display some universal families.
Hyperbolic groups admit proper affine isometric actions on $l^p$-spaces  [PDF]
Guoliang Yu
Mathematics , 2004,
Abstract: In this paper, we show that hyperbolic groups admit proper affine isometric actions on $l^p$-spaces.
Modular group actions on algebras and p-local Galois extensions for finite groups  [PDF]
Peter Fleischmann,Chris Woodcock
Mathematics , 2015, DOI: 10.1016/j.jalgebra.2015.06.003
Abstract: Let k be a field of positive characteristic p and let G be a finite group. In this paper we study the category TsG of finitely generated commutative k-algebras A on which G acts by algebra automorphisms with surjective trace. If A = k[X], the ring of regular functions of a variety X, then trace-surjective group actions on A are characterized geometrically by the fact that all point stabilizers on X are p'-subgroups or, equivalently, that A is a Galois extension of the ring of P invariants for every Sylow p-group P of G. We investigate categorical properties, using a version of Frobenius-reciprocity for group actions on k-algebras, which is based on tensor induction for modules. We also describe projective generators in TsG , extending and generalizing the investigations started in [8], [7] and [9] in the case of p-groups. As an application we show that for an abelian or p-elementary group G and k large enough, there is always a faithful (possibly nonlinear) action on a polynomial ring such that the ring of invariants is also a polynomial ring. This would be false for linear group actions by a result of Serre. For p-solvable groups we obtain a structure theorem on trace-surjective algebras, generalizing the corresponding result for p-groups in [8].
Rigidity for group actions on homogeneous spaces by affine transformations  [PDF]
Mohamed Bouljihad
Mathematics , 2015,
Abstract: We give a criterion for the rigidity of actions on homogeneous spaces. Let $G$ be a real Lie group, $\Lambda$ a lattice in $G$, and $\Gamma$ a subgroup of the affine group Aff$(G)$ stabilizing $\Lambda$. Then the action of $\Gamma$ on $G/\Lambda$ has the rigidity property in the sense of S. Popa, if and only if the induced action of $\Gamma$ on $\mathbb{P}(\frak{g})$ admits no $\Gamma$-invariant probability measure, where $\frak{g}$ is the Lie algebra of $G$. This generalizes results of M. Burger, and A. Ioana and Y. Shalom. As an application, we establish rigidity for the action of a class of groups acting by automorphisms on nilmanifolds associated to step 2 nilpotent Lie groups.
On finite capable $p$-groups of class 2 with cyclic commutator subgroups  [PDF]
Manoj K. Yadav
Mathematics , 2010,
Abstract: We study finite capable $p$-groups $G$ of nilpotency class 2 such that the commutator subgroup $\gamma_2(G)$ of $G$ is cyclic and the center of $G$ is contained in the Frattini subgroup of $G$.
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