Charged string loops in Reissner–Nordström black hole background Tursinbay Oteev, Martin Kološ and Zdeněk Stuchlík Eur. Phys. J. C, 78 3 (2018) 261 Published online: 24 March 2018 DOI: 10.1140/epjc/s10052-018-5735-y