In 1989, Shanks introduced the NUCOMP algorithm [10] for computing the reduced composite of two positive definite binary quadratic forms of discriminant ∆. Essentially by applying reduction before composing the two forms, the intermediate operands are reduced from size O(∆) to O(∆) in most cases and at worst to O(∆). Shanks made use of this to extend the capabilities of his hand-held calculator...

Quadratic forms over division algebras over local or global fields of characteristic 2 are classified by an invariant derived from the Clifford algebra construction. Quadratic forms over skew fields were defined by Tits in [14] to investigate twisted forms of orthogonal groups in characteristic 2, and by C.T.C. Wall [16] in a topological context. The purpose of this paper is to obtain a classif...

Piecewise-isometries are zero-entropy dynamical systems with very complex behaviour. In one-dimension they are intervalexchange transformations (IET), which are connected to diophantine arithmetic by the Boshernitzan and Carrol theorem: in any IET defined over a quadratic number field, the process of induction results, after scaling, in an eventually periodic sequence of IETs. This can be viewe...

1463-5003/$ see front matter 2011 Elsevier Ltd. A doi:10.1016/j.ocemod.2011.06.003 ⇑ Corresponding author. E-mail address: [email protected] (B. Wang Applying the semi-Lagrangian method to discretize the advection of momentum eliminates the Courant number constraint associated with explicit Eulerian momentum advection in coastal ocean models. Key steps of the semi-Lagrangian method include ...

We prove that Z is diophantine over the ring of algebraic integers in any totally real number field or quadratic extension of a totally real number field.

The quadratic Poisson Gel’fand-Kirillov problem asks whether the field of fractions of a Poisson algebra is Poisson birationally equivalent to a Poisson affine space, i.e. to a polynomial algebra K[X1, . . . , Xn] with Poisson bracket defined by {Xi, Xj} = λijXiXj for some skew-symmetric matrix (λij) ∈ Mn(K). This problem was studied in [9] over a field of characteristic 0 by using a Poisson ve...

An attempt is made for the first time to solve the quadratic and cubic model of magneto hydrodynamic Poiseuille flow of Phan-Thein-Tanner (PTT). A series solution of magneto hydrodynamic (MHD) flow is developed by using homotopy perturbation method (HPM). The results are presented graphically and the effects of non-dimensional parameters on the flow field are analyzed. The results reveal many i...

We study the problem of scalar particle production after inflation by an in-flaton field which is oscillating rapidly relative to the expansion of the universe. We use the framework of the chaotic inflation scenario with quartic and quadratic inflaton potentials. Particles produced are described by a quantum scalar field χ, which is coupled to the inflaton via linear and quadratic couplings. Th...

A square-ordered field, also called Hilbert field of type (A), is understood to be an ordered field all of whose positive elements are squares. The problem of classifying, up to isomorphism, all 4-dimensional quadratic division algebras over a square-ordered field k is shown to be equivalent to the problem of finding normal forms for all pairs (X, Y ) of 3× 3-matrices over k, X being antisymmet...

let $f$ be a finite extension of $bbb q$‎, ‎${bbb q}_p$ or a global‎ ‎field of positive characteristic‎, ‎and let $e/f$ be a galois extension‎. ‎we study the realization fields of‎ ‎finite subgroups $g$ of $gl_n(e)$ stable under the natural‎ ‎operation of the galois group of $e/f$‎. ‎though for sufficiently large $n$ and a fixed‎ algebraic number field $f$ every its finite extension $e$ is‎ ‎re...