Теория потенциала на плоскости, специальные функции, аналитические функции одной переменной, теория аппроксимации, неравенства.
Основные публикации:
D. Karp, “Square summability with geometric weight for classical orthogonal expansions”, Advances in Analysis, Proceedings of the 4th International ISAAC Conference, eds. H. G. W. Begehr et al., 2005, 407–421
D. Karp, “Hypergeometric reproducing kernels and analytic continuation from a half-line”, Integral Transforms and Special Functions, 14:6 (2003), 485–498
D. Karp, “Capacity of a condenser whose plates are circular arcs”, Complex Variables and Elliptic Equations, 50:2 (2005), 103–122
D. Karp and S. M. Sitnik, “Asymptotic approximations for the first incomplete elliptic integral near logarithmic singularity”, Journal of Computational and Applied Mathematics, 205:1 (2007), 186–206
D. Karp and S. M. Sitnik, “Inequalities and monotonicity of ratios for generalized hypergeometric function”, Journal of Approximation Theory, 2009, no. 161, 337–352