• openAccess   A criterion for a normal subgroup to be hypercentral based on class sizes 

      Beltrán, Antonio Springer (2024)
      Let G be a finite group and N a normal subgroup of G. We prove that the knowledge of the sizes of the conjugacy classes of G that are contained in N and of their multiplicities provides information of N in relation to the ...
    • closedAccess   Class sizes of prime-power orden p'-elements and normal subgroups 

      Beltrán, Antonio; Felipe, Maria José; Sao, Changguo Springer (2014-06)
      We prove an extension of the renowned Itô’s theorem on groups having two class sizes in three different directions at the same time: normal subgroups, p' -elements and prime- power order elements. Let N be a normal subgroup ...
    • closedAccess   Landau's theorem on conjugacy classes for normal subgroups 

      Beltrán, Antonio; Felipe, Maria José; Melchor Borja, Carmen World Scientific (2016-10-10)
      Landau’s theorem on conjugacy classes asserts that there are only finitely many finite groups, up to isomorphism, with exactly k conjugacy classes for any positive integer k. We show that, for any positive integers n and ...
    • closedAccess   Simplicity of normal subgroups and conjugacy class sizes 

      Beltrán, Antonio; Felipe, Maria José Springer (2013)
      Given a finite group G which possesses a non-abelian simple normal subgroup N having exactly four G -class sizes, we prove that N is isomorphic to PSL (2,2a) with a≥2 . Thus, we obtain an extension for normal subgroups of ...
    • closedAccess   Structure of normal subgroups with three G-class sizes 

      Beltrán, Antonio; Felipe, Maria José; Akhlaghi, zeinab; Khatami, Maryam Springer-Verlag (2012)
      Let G be a finite group and N be a normal subgroup of G. Suppose that the set of G-conjugacy class sizes of N is {1, m, n}, with m < n and m does not divide n. In this paper, we show that N is solvable, and we determine ...
    • closedAccess   Triangles in the graph of conjugacy classes of normal subgroups 

      Beltrán, Antonio; Felipe, Maria José; Melchor Borja, Carmen Springer (2015-12)
      Let G be a finite group and N a normal subgroup of G. We determine the structure of N when the graph ΓG(N), which is the graph associated to the conjugacy classes of G contained in N, has no triangles and when the graph ...