This paper concerns with the modeling and construction of a fifth order method for two dimensional acoustic wave equation in heterogenous media. The method is based on a standard discretization of the problem on smooth regions and a nonstandard method for nonsmooth regions. The construction of the nonstandard method is based on the special treatment of the interface using suitable jump conditio...

We present a nonstandard hull construction for locally uniform groups in a spirit similar to Luxembourg’s construction of the nonstandard hull of a uniform space. Our nonstandard hull is a local group rather than a global group. We investigate how this construction varies as one changes the family of pseudometrics used to construct the hull. We use the nonstandard hull construction to give a no...

Recently, Dag Normann and the author have established a connection between higher-order computability theory and Nonstandard Analysis; new results in both fields are obtained by exploiting this connection ([28]). Now, on the side of computability theory, the technique known as Grilliot’s trick constitutes a template for explicitly defining the Turing jump functional (∃) in terms of a given effe...

In this paper, we highlight a new computational aspect of Nonstandard Analysis relating to higher-order computability theory. In particular, we prove that the Gandy-Hyland functional equals a primitive recursive functional involving nonstandard numbers inside Nelson’s internal set theory. From this classical and ineffective proof in Nonstandard Analysis, a term from Gödel’s system T can be extr...

In the past few decades, nonstandard methods, as a branch of mathematical logic, have been successfully applied to obtain new results in additive/combinatorial number theory (cf. [BJ, Ji1, Ji2, Ji3, Ji4, Ji5, Ji6, JK, Le1, Le2, Le3, Le4]). Although the nonstandard techniques in these applications are elementary from a nonstandard analyst’s point of view, it is extremely difficult for a reader w...

this paper concerns with the modeling and construction of a fifth order method for two dimensional acoustic wave equation in heterogenous media. the method is based on a standard discretization of the problem on smooth regions and a nonstandard method for nonsmooth regions.the construction of the nonstandard method is based on the special treatment of the interface using suitable jump condition...