On Nikishin systems with discrete components and weak asymptotics of multiple orthogonal polynomials

This survey considers multiple orthogonal polynomials with respect to Nikishin systems generated by a pair $(\sigma_1,\sigma_2)$ of measures\linebreak with unbounded supports ($\operatorname{supp}(\sigma_1) \subseteq \mathbb{R}_+$, $\operatorname{supp}(\sigma_2)\subset \mathbb{R}_-$) and with $\sigma_2$ discrete. A Nikishin-type equilibrium problem in the presence of an external field acting on $\mathbb{R}_+$ and a constraint on $\mathbb{R}_-$ is stated and solved. The solution is used for deriving the contracted zero distribution of the associated multiple orthogonal polynomials.
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