Died: 4 September 1984 in Geneva, Switzerland

First let us look at Ernst Stueckelberg's name. He was baptised Johann Melchior Ernst Karl Gerlach Stückelberg but in later life he gave his name as Ernst Carl Gerlach Stückelberg. However, it is more complicated than this. His father was Alfred Stückelberg, who was a lawyer, and Alfred's father was the Swiss artist Ernst Stückelberg (1831-1903), painter of Tell's chapel. Legend says that Wilhelm Tell saved himself with a leap out of Gessler's boat at a corner of the Lake of Uri. A chapel to commemorate this stood from the 14^th century but in 1879-80 a new chapel was built (which still stands) and decorated with four marvellous frescos showing scenes of Tell's life painted by Ernst Stückelberg. The mother of Ernst Stueckelberg, the subject of this biography, was Alice Breidenbach and as her father had no male children, her children were allowed to use the title von Breidenbach zu Breidenstein und Melsbach after his death in 1911. Then Ernst Stueckelberg's full name became Johann Melchior Ernst Karl Gerlach Stückelberg von Breidenbach zu Breidenstein und Melsbach.

Ernst had a strict upbringing and, as Philip Morse writes, Stueckelberg [2]:-

... could not help his name, nor could he help his mannerisms, which had been drilled into him by his father. He once told me his father would not allow him to take off his coat or tie even when he was studying by himself in his own room.

Stueckelberg was brought up and educated in Basel where he attended the Humanistic Gymnasium, a 16^th century secondary school in the Cathedral Square of Basel. In 1930, only a few years after Stueckelberg graduated from the school, it changed its name to Gymnasium am Münsterplatz. He began his university studies at the University of Basel and at this stage his interests were in experimental rather than theoretical physics. He moved from his home town of Basel to Munich where he undertook research with Arnold Sommerfeld. Sommerfeld is, of course, known as a theoretical physicist, but after he came to Munich in 1906 he wanted to be able to direct experimental work aimed at checking his theories. In fact he supervised a large number of students at Munich in programmes of experimental research as well as theoretical physics. Stueckelberg worked in the Institute which had been set up for Sommerfeld, with rooms for seminars, rooms for assistants, and laboratories for experimental work. He submitted his doctoral thesis on his experimental results on the properties of cathode rays to the University of Basel in 1926 and he was awarded the degree of Dr. phil. in the following year.

It was only after completing his doctoral thesis that Stueckelberg moved from experimental physics to theoretical physics. He also moved countries, going to the United States in 1927 to study at Princeton University. Philip Morse met Stueckelberg at this time. He writes [2]:-

I also came to know a rather stiff young man, tall and thin, with an aristocratic profile and a Prussian manner and carriage. His full name was Ernst Carl Gerlach Melchior Stueckelberg von Breidenbach zu Breidenstein. ... he really wanted to become a physicist, and he had come to study under Compton. We came to be close friends, perhaps because opposites attract.

The Michigan summer physics programme was held every year and, in 1928, Kramers lectured on quantum theory and Ehrenfest on statistical physics. Also lecturing were Sam Goudsmit and George Uhlenbeck. Stueckelberg arrived halfway through the summer and from then on Morse, Kramers and Stueckelberg would go on outings and spend time together drinking beer [2]:-

It didn't take much urging, on Ernst's and my part, to get Kramers to talk physics during our evening meals with beer. In fact, these meals turned into a series of tutorials on the quantum mechanics. A marathon session took place during the day Kramers was getting ready to go back to Holland. Stueckelberg and I helped with the packing while Kramers lectured. Occasionally all three of us would gather around the table while Kramers wrote out a few equations, illustrating how they fitted together to explain some atomic property or other. These casual lectures started both Ernst and me off in new research directions.

Back at Princeton [2]:-

Stueckelberg and I had laid out a whole series of calculations we wanted to attempt. We saw a chance to get in on the ground floor of research in quantum mechanics.

They were helped by Edward U Condon, a pioneer in quantum mechanics, and Howard P Robertson, who was appointed as professor of physics at Princeton in 1929. In 1930 Stueckelberg was appointed as a research associate and assistant professor at Princeton. He gave a paper at the New York meeting of the Physical Society held at Columbia University then in the autumn of 1930 then, along with Morse who was collaborating on various research topics, he went to spend time at Sommerfeld's Institute in Munich. There Stueckelberg and Morse worked together on high energy collisions. In the spring Stueckelberg, together with Morse, moved to England to spend time at Cambridge.

However, these were difficult times with signs of the Great Depression evident in Europe during his visit. By the time he returned to Princeton economic conditions were deteriorating and his employment at Princeton came to an end in 1932 as funding became increasingly tight. He returned to Switzerland where he became a Privatdozent at the University of Zurich in 1933. Gregor Wentzel held the Chair for Theoretical Physics at the University of Zurich at this time and Wolfgang Pauli was professor at the Eidgenössische Technische Hochschule Zurich, so Zurich had a high reputation for theoretical physics. Stueckelberg submitted his habilitation thesis to the University of Zurich and gained the right to become a lecturer.

In September 1934 Stueckelberg submitted the paper Relativistisch invariante Störungstheorie des Diracschen Elektrons (The relativistically invariant perturbation theory of the direct electron) to Annalen der Physik. It looks at high energy collision phenomena between electrons and nuclei. Pauli wrote to Heisenberg about this paper on 5 February 1937 (over two years after its publication):-

Concerning the formalisation of scattering theory, I wish to draw your attention to a paper of Stueckelberg (1934). This paper is not written very well, but the basic idea (which goes back to Wentzel) seems to me reasonable; it consists of establishing relativistic invariance by the fact that one removes space and time totally from the theory, and directly examines the coefficients of the four-dimensional Fourier expansion of the wave function.

Arthur Schidlof, who held the chair of theoretical physics at the University of Geneva, died in 1934. Stueckelberg was appointed to succeed him in the following year. In this same year, 1935, he gave an explanation of nuclear interactions as being due to the exchange of vector bosons. He did not publish his ideas on this since Pauli told him it was ridiculous. Hideki Yukawa received the Nobel prize in 1949 for giving a similar explanation of nuclear interactions. Lacki, Ruegg and Telegdi write [6]:-

The contribution of Stueckelberg ... constitutes the first complete and easily generalizable instance of a manifest relativistically invariant perturbative calculus. It is of interest in many respects, both technical and epistemological. The "modernity" of this contribution is striking and characteristic of Stueckelberg's original turn of mind.

A big advance in theoretical physics was the renormalization programme in quantum field theory. At the 1948 Solvay congress, Oppenheimer insisted on preserving covariance in all steps of the calculation if one wants to eliminate the infinities which otherwise occur. He then quoted Stueckelberg's 1934 paper as giving an example of such a covariant theory. This was not Stueckelberg's only contribution to the renormalization programme, however, for in the early 1940s he wrote a long paper outlining a complete and correct description of the renormalization procedure for quantum electrodynamics. He sent it to the Physical Review, but it was rejected. As Stueckelberg later recalled:-

They said it was not a paper, it was a programme, an outline, a proposal ...

He then set about filling in all the details but Schwinger and Feynman published their version first and Stueckelberg received no recognition for his remarkable contributions. In 1965 Sin-Itiro Tomonaga, Julian Schwinger and Richard P Feynman were jointly awarded the Nobel Prize for Physics:-

... for their fundamental work in quantum electrodynamics, with deep-ploughing consequences for the physics of elementary particles.

After receiving the Nobel Prize, Feynman lectured at CERN to an audience which included Stueckelberg. Jagdish Mehra writes [7]:-

After the lecture, Stueckelberg was making his way out alone ... from the CERN ampitheatre, when Feynman - surrounded by admirers - made the remark: "He [Stueckelberg] did the work and walks alone toward the sunset; and, here I [Feynman] am, covered in all the glory, which rightfully should be his!"

In 1951 Stueckelberg and Andre Petermann invented the renormalization group. In 1982 Kenneth G Wilson was awarded the Nobel Prize for Physics:-

... for his theory for critical phenomena in connection with phase transitions.

The Press Release for this award states that:-

Wilson built his theory on an essential modification of a method in theoretical physics called renormalization group theory, which was developed already during the fifties and was applied with varying success to different problems.

In his Nobel Lecture, Wilson said:-

Stueckelberg and Petermann observed that transformation groups could be defined which relate different reparametrizations - they called these groups "groupes de normalization" which is translated "renormalization group".

André Petermann recalls working with Stueckelberg [5]:-

I was not really a student of Stueckelberg, but a recently graduate mathematician working on direct products of generalized functions and on the space on which they can be defined. Stueckelberg, having such a problem with his student T A Green, in the work they were doing in S-matrix theory, asked me if I would be interested in working at the Swiss Atomic Energy Commission, in order to deal with this problem in a mathematical way, according to Schwartz, Sobolev and others. I took the job, and Stueckelberg became more my boss than my professor and later my beloved friend. I worked there during three years, leaving (on the advice of Stueckelberg) to go to Niels Bohr in Copenhagen.

Stueckelberg continued to hold the chair at Geneva until he retired in 1975. However, he was also appointed professor at the University of Lausanne in 1956, again holding this position until he retired. He suffered mental health problems and was given the treatment which was common at that time, namely administered electric shocks. Although the problems continued to recur, Stueckelberg was able to carry out his duties. A few months before his death the struggle was becoming too much for him. He said:-

I look forward every day to my eventual journey to Heaven ... We live too long ...

He is buried in the Cimetière de Plainpalais, Rue des Rois, Geneva (where the reformer John Calvin is also buried).

Books:

1. J Lacki (ed.), Selected Works of Ernst C G Stueckelberg (Birkhäuser, 2008).
2. P M Morse, In at the Beginnings: A Physicist's Life (MIT Press, 1977).

Articles:

1. F Cianfrani and O M Lecian, E C G Stueckelberg: a forerunner of modern physics, roceedings of the I Stueckelberg Workshop, Pescara, June 2006, Nuovo Cimento - B 122 (2) (2007), 123-143.
2. F Cianfrani and O M Lecian, E C G Stueckelberg: a forerunner of modern physics II, Proceedings of the II Stueckelberg Workshop, Int. J. Mod. Phys. A (2008), 1105-1112.
3. Ernst Carl Gerlach Stueckelberg, University of Basel
   http://quasar.physik.unibas.ch/~aste/stueckelberg.html
4. J Lacki, H Ruegg and V Telegdi, The Road to Stueckelberg's Covariant Perturbation Theory as Illustrated by Successive Treatments of Compton Scattering, Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics 30 (4) ( 1999), 457-518.
5. J Mehra, The Beat of a Different Drum : The Life and Science of Richard Feynman (Oxford 1994), 573-577.