We investigate the ideal structures of the C∗-algebras arising from topological graphs. We give the complete description of ideals of such C∗-algebras which are invariant under the so-called gauge action, and give the condition on topological graphs so that all ideals are invariant under the gauge action. We get conditions for our C∗algebras to be simple, prime or primitive. We completely deter...

We study conditions on a C∗-dynamical system (A,G,α) under which induction of primitive ideals (resp. irreducible representations) from stabilizers for the action of G on the primitive ideal space Prim(A) give primitive ideals (resp. irreducible representations) of the crossed product A⋊α G. The results build on earlier results of Sauvageot [17] and others, and will correct a (possibly overly o...

For an ideal I of O(D), we will denote its image in the ideal class monoid by [I]. In particular, composing the map f 7→ I(f) with the map which sends an ideal to its class, we get a map which sends a primitive, positive definite quadratic form f of discriminant D to the ideal class [I(f)]. This has remarkable properties. Indeed, we have the following important and beautiful result (unlike some...

We look at the relationships between class numbers of quadratic structures (orders and fields) and the solutions of exponential Diophantine equations. We conclude with necessary and sufficient conditions for a class group to have an element of a given order. 1. Notation and Preliminaries If D is a squarefree integer, then its discriminant is given by ( ) ( )    ≡ ≡/ = ∆ . 4 mod 1 if , 4 mod ...

In this paper, we extend the Banach-Stone theorem to the non commutative case, i.e, we prove that the structure of the liminal C *-algebras A determines the topology of its primitive ideal space.

where 3 is the centre of 51 and cl denotes closure in the norm topology. When 5t is a von Neumann algebra this result is already known (see [7; Lemma 9, p. 255], where the method requires only trivial modification to deal with the case of a left ideal), and the proof in that situation involves the restriction of an operator in M to a subspace on which it can be inverted. The proof given here fo...

For a ring R, endomorphism α of R and positive integer n we define a skew triangular matrix ring Tn(R,α). By using an ideal theory of a skew triangular matrix ring Tn(R,α) we can determine prime, primitive, maximal ideals and radicals of the ring R[x;α]/〈xn〉, for each positive integer n, where R[x;α] is the skew polynomial ring, and 〈xn〉 is the ideal generated by xn.

A cryptographic primitive or a security mechanism can be specified in a variety of ways, such as a condition involving a game against an attacker, construction of an ideal functionality, or a list of properties that must hold in the face of attack. One reason that an ideal functionality is appealing is that if an implementation cannot be distinguished from an ideal functionality, by any feasibl...