Gösta Mittag-Leffler

Magnus Gustaf "Gösta" Mittag-Leffler (16 March 1846 – 7 July 1927) was a Swedish mathematician whose work mainly dealt with function theory, now known as complex analysis. He established the highly respected journal *Acta Mathematica* and served as its editor for four decades. Mittag-Leffler actively supported women in intellectual fields during a time when their work was frequently ignored or wrongly credited to men. He worked hard to secure Sofia Kovalevskaya a full professorship in mathematics at Stockholm University. He also persuaded the Nobel committee to acknowledge Marie Curie as an equal partner with her husband Pierre in their discoveries about radiation. Mittag-Leffler started the effort to nominate Henrietta Swan Leavitt for the Nobel Prize in Physics for her work on Cepheid variable stars, which was essential to Edwin Hubble’s later findings on the universe’s scale; this nomination had to be dropped after Leavitt died of stomach cancer in 1921. Following World War I, Mittag-Leffler donated his Djursholm estate and its extensive mathematics library to the Royal Swedish Academy of Sciences, which became the basis for the modern Mittag-Leffler Institute.

Mittag-Leffler was born in Stockholm, the first son of schoolteacher John Olof Leffler and Gustava Wilhelmina, née Mittag. Shortly after his birth, his father became a school principal, and the family lived in the school building at "Katarina Schoolhouse." They later bought their own house. Gösta had three siblings: Anna-Maria, who became a well-known writer; Frits, a linguist; and Arthur, a civil engineer. The children remembered their parents’ home as open and welcoming, often filled with friends. As an adult, Gösta said much of his early learning came from listening to these guests. He also had fond memories of his maternal grandparents, spending summers at their house in Fågelås. At age 20, he added his mother’s maiden name to his father’s surname as a tribute.

In 1855, he attended Klara Elementary School in Stockholm, a respectable school for upper-class families. August Strindberg later described it as a harsh, Dickensian place with student fights, frequent teacher beatings, and a strict atmosphere. Still, Gösta was a gifted student and met Viktor Rydberg there. He entered Uppsala University when Göran Dillner led mathematics teaching. Under Dillner, Mittag-Leffler wrote and defended a thesis that biographers called "less than remarkable," earning his PhD in 1872 and becoming a docent that same year.

In 1873, he won a Byzantine stipend from a Swedish donor in Constantinople, requiring three years of study abroad. From 1873 to 1876, he studied at the University of Paris, Humboldt University of Berlin, and the University of Göttingen. In Paris in October 1873, he met Darboux, Joseph Liouville, Charles Auguste Briot, Jean Claude Bouquet, and others. He attended Charles Hermite’s lectures on elliptic functions but found them old-fashioned and hard to follow. In spring 1874, he moved to Berlin and attended Karl Weierstrass’s lectures on elliptic functions, which greatly influenced his thinking and methods. During this time, he also edited the Stockholm-based weekly newspaper *Ny Illustrerad Tidning*.

In 1877, Mittag-Leffler became professor of mathematics at the University of Helsinki, succeeding Lorenz Lindelöf. His thesis for the position was called brilliant, even by fellow applicant Ernst Leonard Lindelöf. In Helsinki, he taught elliptic functions and basic analysis and supervised many thesis students, some of whom later moved to Sweden to work with him. He resigned in 1881 and on June 11 became the first mathematics professor at the newly founded University College of Stockholm (later Stockholm University). In 1882, he married Signe Lindfors, who came from a wealthy Finnish family; her father was a major-general and businessman, and her mother was from a rich merchant family in Helsinki.

In 1889, Mittag-Leffler bought two half-hectare lots in Djursholm, later purchasing more land to become the biggest landlord in Midgård by the early 1890s. He built a family house by April 1891, designed by three leading architects: Rudolf Arborelius, Carl Westman, and Ferdinand Boberg. The house became famous for its hospitality, hosting many prominent mathematicians from around the world. Its remarkable library, containing volumes from the 16th century, was open for guests to work in. Mittag-Leffler himself worked there editing *Acta Mathematica*, making the Djursholm estate a center for mathematical research. By 1899, he was already a member of the Royal Swedish Academy of Sciences.