CARLITZ DIFFERENTIAL EQUATIONS WITH REGULAR SINGULARITY OVER A FUNCTION FIELD


Anatoly N. Kochubei

Institute of Mathematics,
National Academy of Sciences of Ukraine,
Tereshchenkivska 3, Kiev, 01601 Ukraine
E-mail: ank@ank.kiev.ua


Let K be the field of formal Laurent series with coefficients from the Galois field Fq. We study some classes of equations with Carlitz derivatives for Fq-linear functions on subsets of K, which are the natural function field counterparts of linear ordinary differential equations with a regular singularity. In particular, an analog of the equation for the power function, the Fuchs and Euler type equations, and Thakur's hypergeometric equation are considered. Some properties of the above equations are similar to the classical case while others are different. For example, a simple model equation shows a possibility of existence of a non-trivial continuous locally analytic Fq-linear solution which vanishes on an open neighbourhood of the initial point.