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Embedding permutation groups into wreath products in product action  [PDF]
Cheryl E. Praeger,Csaba Schneider
Mathematics , 2011,
Abstract: The wreath product of two permutation groups G < Sym(Gamma) and H < Sym(Delta) can be considered as a permutation group acting on the set Pi of functions from Delta to Gamma. This action, usually called the product action, of a wreath product plays a very important role in the theory of permutation groups, as several classes of primitive or quasiprimitive groups can be described as subgroups of such wreath products. In addition, subgroups of wreath products in product action arise as automorphism groups of graph products and codes. In this paper we consider subgroups X of full wreath products Sym(Gamma) wr Sym(Delta) in product action. Our main result is that, in a suitable conjugate of X, the subgroup of Sym(Gamma) induced by a stabilizer of a coordinate delta in Delta only depends on the orbit of delta under the induced action of X on Delta. Hence, if the action of X on Delta is transitive, then X can be embedded into a much smaller wreath product. Further, if this X-action is intransitive, then X can be embedded into a direct product of such wreath products where the factors of the direct product correspond to the X-orbits in Delta. We offer an application of the main theorems to error-correcting codes in Hamming graphs.
Finite generation of iterated wreath products in product action  [PDF]
Matteo Vannacci
Mathematics , 2015,
Abstract: Let $\mathcal{S}$ be a sequence of finite perfect transitive permutation groups with uniformly bounded number of generators. We prove that the infinitely iterated wreath product in product action of the groups in $\mathcal{S}$ is topologically finitely generated, provided that the actions of the groups in $\mathcal{S}$ are not regular. We prove that our bound has the right asymptotic behaviour. We also deduce that other infinitely iterated mixed wreath products of groups in $\mathcal{S}$ are finitely generated. Finally we apply our methods to find explicitly two generators of infinitely iterated wreath products in product action of special sequences $\mathcal{S}$.
Innately transitive subgroups of wreath products in product action  [PDF]
Robert W. Baddeley,Cheryl E. Praeger,Csaba Schneider
Mathematics , 2003,
Abstract: A permutation group is innately transitive if it has a transitive minimal normal subgroup, which is referred to as a plinth. We study the class of finite, innately transitive permutation groups that can be embedded into wreath products in product action. This investigation is carried out by observing that such a wreath product preserves a natural Cartesian decomposition of the underlying set. Previously we classified the possible embeddings in the case where the plinth is simple. Here we extend that classification and identify several different types of Cartesian decompositions that can be preserved by an innately transitive group with a non-abelian plinth. These different types of decompositions lead to different types of embeddings of the acting group into wreath products in product action. We also obtain a full characterisation of embeddings of innately transitive groups with diagonal type into such wreath products.
Wreath product action on generalized Boolean algebras  [PDF]
Ashish Mishra,Murali K. Srinivasan
Mathematics , 2014,
Abstract: Let G be a finite group acting on the finite set X such that the corresponding (complex) permutation representation is multiplicity free. There is a natural rank and order preserving action of the wreath product G~S_n on the generalized Boolean algebra B_X(n). We explicitly block diagonalize the commutant of this action.
Transitive simple subgroups of wreath products in product action  [PDF]
Cheryl E. Praeger,Robert W. Baddeley,Csaba Schneider
Mathematics , 2002,
Abstract: A transitive simple subgroup of a finite symmetric group is very rarely contained in a full wreath product in product action. All such simple permutation groups are determined in this paper. This remarkable conclusion is reached after a definition and detailed examination of `Cartesian decompositions' of the permuted set, relating them to certain `Cartesian systemsof subgroups'. These concepts, and the bijective connections between them, are explored in greater generality, with specific future applications in mind.
Three types of inclusions of innately transitive permutation groups into wreath products in product action  [PDF]
Cheryl E. Praeger,Csaba Schneider
Mathematics , 2004,
Abstract: A permutation group is innately transitive if it has a transitive minimal normal subgroup, and this subgroup is called a plinth. In this paper we study three special types of inclusions of innately transitive permutation groups in wreath products in product action. This is achieved by studying the natural Cartesian decomposition of the underlying set that correspond to the product action of a wreath product. Previously we identified six classes of Cartesian decompositions that can be acted upon transitively by an innately transitive group with a non-abelian plinth. The inclusions studied in this paper correspond to three of the six classes. We find that in each case the isomorphism type of the acting group is restricted, and some interesting combinatorial structures are left invariant. We also show how to construct examples of inclusions for each type.
Inclusions of innately transitive groups into wreath products in product action with applications to $2$-arc-transitive graphs  [PDF]
Cai-Heng Li,Cheryl E. Praeger,Csaba Schneider
Mathematics , 2015,
Abstract: We study $(G,2)$-arc-transitive graphs for innately transitive permutation groups $G$ such that $G$ can be embedded into a wreath product $\sym\Gamma\wr\sy\ell$ acting in product action on $\Gamma^\ell$. We find two such connected graphs: the first is Sylvester's double six graph with 36 vertices, while the second is a graph with $120^2$ vertices whose automorphism group is $\aut\sp 44$. We prove that under certain conditions no more such graphs exist.
Invariant states on the wreath product  [PDF]
A. V. Dudko,N. I. Nessonov
Mathematics , 2009,
Abstract: Let $\mathfrak{S}_\infty$ be the infinity permutation group and $\Gamma$ be a separable topological group. The wreath product $\Gamma\wr \mathfrak{S}_\infty$ is the semidirect product $\Gamma^\infty_e \rtimes \mathfrak{S}_\infty$ for the usual permutation action of $\mathfrak{S}_\infty$ on $\Gamma^\infty_e=\{[\gamma_i]_{i=1}^\infty : \gamma_i\in \Gamma,\textit{only finitely many}\gamma_i\neq e\}$. In this paper we obtain the full description of indecomposable states $\varphi$ on the group $\Gamma\wr\mathfrak{S}_\infty,$ satisfying the condition: \varphi(sgs^{-1})= \varphi(g)\text{for each}g\in \Gamma\wr \mathfrak{S}_\infty,s\in\mathfrak{S}_\infty.
Wreath product of matrices  [PDF]
Daniele D'Angeli,Alfredo Donno
Mathematics , 2015,
Abstract: We introduce a new matrix product, that we call the wreath product of matrices. The name is inspired by the analogous product for graphs, and the following important correspondence is proven: the wreath product of the adjacency matrices of two graphs provides the adjacency matrix of the wreath product of the graphs. This correspondence is exploited in order to study the spectral properties of the famous Lamplighter random walk: the spectrum is explicitly determined for the "Walk or switch" model on a complete graph of any size, with two lamp colors. The investigation of the spectrum of the matrix wreath product is actually developed for the more general case where the second factor is a circulant matrix. Finally, an application to the study of generalized Sylvester matrix equations is treated.
ON WREATH PRODUCT OF PERMUTATION GROUPS
IBRAHIM,A. A; AUDU,M. S;
Proyecciones (Antofagasta) , 2007, DOI: 10.4067/S0716-09172007000100004
Abstract: this report is essentially an upgrade of the results of audu (see [1] and [2]) on some finite permutation groups. it consists of the basic procedure for computing wreath product of groups. we also discussed the conditions under which the wreath products of permutation groups are faithful, transitive and primitive. further, the centre of the stabilizer and the centre of wreath products was investigated, and finally, an illustration was supplied to support our findings
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