Let Γ be a congruence subgroup of SL(2,Z). The modular curve X(Γ) and its Jacobian variety J(Γ) are very important objects in number theory. For instance, the problem of determining all possible structures of (Q-)rational torsion subgroup of elliptic curves over Q is equivalent to that of determining whether the modular curves X1(N) have non-cuspidal rational points. Also, the celebrated theore...

Let F be a (topologically) finitely generated free pro-p-group, and ß an automorphism of F . If p ^ 2 and the order of ß is 2 , then there is some basis of F such that ß either fixes or inverts its elements. If p does not divide the order of ß , then the subgroup of F of all elements fixed by ß is (topologically) infinitely generated; however this is not always the case if p divides the order o...

The author has computed the class groups of all complex quadratic number fields Q(\f^~D) °f discriminant D for 0 < D < 4000000. In so doing, it was found that the first occurrences of rank three in the 3-Sylow subgroup are D = 3321607 = prime, class group C(3) x C(3) x C(9.7) (C(n) a cyclic group of order n), and D = 3640387 = 421.8647, class group C(3) X C(3) X C(9.2). The author has also foun...

in this article we introduce the notion of n-capable groups. it is shown that every group g admits a uniquely determined subgroup (〖z^n)〗^* (g) which is a characteristic subgroup and lies in the n-centre subgroup of the group g. this is the smallest subgroup of g whose factor group is n-capable. moreover, some properties of n-central extension will be studied.

Let G be a finite group. The spectrum of G is the set ω(G) of orders of all its elements. The subset of prime elements of ω(G) is called the prime spectrum ofG and is denoted by π(G). The spectrum ω(G) of a groupG defines its Grunberg–Kegel graph (or prime graph) Γ(G) with vertex set π(G), in which any two different vertices r and s are adjacent if and only if the number rs belongs to the set ω...

let $r$ be a commutative ring with identity‎. ‎a proper ideal $p$ of $r$ is a $(n-1,n)$-$phi_m$-prime ($(n-1,n)$-weakly prime) ideal if $a_1,ldots,a_nin r$‎, ‎$a_1cdots a_nin pbackslash p^m$ ($a_1cdots a_nin pbackslash {0}$) implies $a_1cdots a_{i-1}a_{i+1}cdots a_nin p$‎, ‎for some $iin{1,ldots,n}$; ($m,ngeq 2$)‎. ‎in this paper several results concerning $(n-1,n)$-$phi_m$-prime and $(n-1,n)$-...

By Mazur's Torsion Theorem, there are fourteen possibilities for the non-trivial torsion subgroup $T$ of a rational elliptic curve. For each $T$, such that $E$ may have additive reduction at prime $p$, we consider parameterized family $E_T$ curves with property they parameterize all $E/\mathbb{Q}$ which contain in their subgroup. Using these families, explicitly classify Kodaira-N\'{e}ron type,...

in this paper we introduce the concept of weakly prime ternary subsemimodules of a ternary semimodule over a ternary semiring and obtain some characterizations of weakly prime ternary subsemimodules. we prove that if $n$ is a weakly prime subtractive ternary subsemimodule of a ternary $r$-semimodule $m$, then either $n$ is a prime ternary subsemimodule or $(n : m)(n : m)n = 0$. if $n$ is a $q$-...

In this paper, we develop a simple method for computing the stabilizer subgroup of a subgroup of D(g) = {α ∈ Fq | there is a β ∈ Fq such that β = g(α)} in PSL2(Fq), where q is a large odd prime power, n is a positive integer dividing q − 1, and g(x) ∈ Fq [x]. As an application, we construct new infinite families of 3-designs (cf. Examples 3.4 and 3.5).