150th Birthday of Josip Plemelj

Elements of the equation that Josip Plemelj was the first in the world to solve. Numbers and symbols rotate in circles that evoke the movement of planets, motion through space, and the bringing together of individual intractable elements into a whole. The design links Plemelj's two fields of work and research: mathematics and astronomy. Worked into the rings of numbers and letters are the issuing state 'SLOVENIJA', the year '2023', and the commemorative inscription 'JOSIP PLEMELJ 1873'.

Josip Plemelj was one of the most important mathematicians Slovenia has produced. Born in Bled in 1873, he worked mainly at the University of Vienna and later as founding rector of the University of Ljubljana, playing a decisive role in its establishment. Scientifically, he is best known for his work on the Riemann problem: in 1908, Plemelj was the first to provide a proof of the so-called Riemann-Hilbert problem (Hilbert's 21st problem), one of the famous 23 problems that David Hilbert posed to mathematics as research challenges in 1900. In addition, he developed the Plemelj formulas named after him, fundamental equations of complex function theory that are still applied today in mathematical physics and potential theory.

Slovenia honors him as a key figure in its scientific history. Over the course of his career, Plemelj bridged two worlds: abstract foundational research in mathematics and its application in astronomy and mechanics. He taught and researched in Ljubljana for decades, shaping generations of Slovenian mathematicians and, through his academic work, laying a cornerstone for the development of an independent Slovenian scientific culture. His influence reaches far beyond the country's borders and is documented in the international history of mathematics. On the 150th anniversary of Josip Plemelj's birth in 2023, Slovenia honored his life's work with the issue of a 2-euro commemorative coin.