#### Vol. 12, No. 6, 2019

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Nonstandard existence proofs for reaction diffusion equations

### Connor Olson, Marshall Mueller and Sigurd B. Angenent

Vol. 12 (2019), No. 6, 1015–1034
##### Abstract

We give an existence proof for distribution solutions to a scalar reaction diffusion equation, with the aim of illustrating both the differences and the common ingredients of the nonstandard and standard approaches. In particular, our proof shows how the operation of taking the standard part of a nonstandard real number can replace several different compactness theorems, such as Ascoli’s theorem and the Banach–Alaoglu theorem on weak${}^{\ast }$-compactness of the unit ball in the dual of a Banach space.

 \vrule height 2.5pt depth -2pt width 26pt To the memory of Terry Millar \vrule height 2.5pt depth -2pt width 26pt
##### Keywords
nonstandard analysis, partial differential equations, reaction diffusion equations
##### Mathematical Subject Classification 2010
Primary: 26E35, 35K57