Lajos Jánossy

This article is about the astrophysicist Lajos Jánossy. For other Jánossy Lajos, see Lajos Jánossy (disambiguation).
The native form of this personal name is Jánossy Lajos. This article uses the Western name order.

Lajos Jánossy (Budapest, 1912 March 2 – Budapest, 1978 March 2) was a Hungarian physicist, astrophysicist and mathematician and a member of the Hungarian Academy of Sciences. He carried out research in astrophysics, nuclear physics, quantum mechanics, mathematical physics and statistics, as well as electrodynamics and optics.

Biography

He was the adopted son of the philosopher György Lukács (1885–1971); brother of the economist and engineer Ferenc Jánossy (1914–1997); and father of Mihály Jánossy (1942–2004), András Jánossy (1944), István Jánossy (1945) (all three physicists), and Jánossy Anna, medical researcher.

From the age of 6, he lived abroad: he attended university in Vienna and, later, in Berlin. For a few years, he worked with Kohlhörster in Berlin, and, then, with P.M.S. Blackett — who later became a Nobel Prize winner in 1948 — in the field of cosmic radiation at Birkbeck College in London and, later, at Manchester University. In 1947, he moved to Ireland and was appointed to a professorship at the Dublin Institute for Advanced Studies. He worked there as the leader of the Cosmic Radiation Laboratory for nearly three years.

After the 1919 fall of the early Hungarian Soviet Republic, his mother and stepfather, Borstieber Gertrúddal and György Lukács, left the country together, and moved to Vienna where he attended secondary school. He was studied at the Vienna (1930–1934) and at the Humboldt University in Berlin. He worked in the laboratory of Werner Kolhörster in Berlin (1934–1936), in astrophysics .

In 1936, fleeing Nazism, he moved to London, until 1938, carrying out research at Birkbeck College. From 1938 on he worked at the University of Manchester under the subsequent Nobel laureate Patrick Blackett on astrophysics, heading the cosmic radiation research group. In 1947 invited by Walter Heitler and Erwin Schrödinger he joined the Dublin Institute for Advanced Studies as a professor and group leader of the cosmic rays research laboratory.

Invited by the Hungarian government, Jánossy returned home in 1950, not only for reasons of promised scientific possibilities, but also because his foster father and his mother had also returned there from their emigration in Moscow.

Jánossy was charged with the task of managing the Cosmic Radiation Department at the Central Research Institute for Physics (Hungarian abbreviation: KFKI) founded in 1950. He was very active in scientific organisation, education and public life. He was appointed deputy director of the KFKI from 1950 to 1956, and the director from 1956 to 1970. In addition, he was also active in university education; the Department of Nuclear Physics at Loránd Eötvös University was established for him. He was the first head of the Department of Nuclear Physics from 1957 to 1970.

His political engagement is attested by his membership, from 1962 until his death, in the Hungarian Socialist Workers 'Party, the Hungarian Socialist Workers' Party Central Committee.

Work

At the beginning of his career in Germany, England, and Ireland, Jánossy focussed on cosmic rays, both experiment and theory.[1] His name is linked to Geiger's coincidence detector development with special application to cosmic-ray secondary components created in the upper layers of the atmosphere (mesons such as kaons, muons, gamma rays). He demonstrated how primary cosmic rays colliding with the Earth's atmosphere produced secondary penetrating showers cascading to the surface of the earth (1940–1941).

From an early age to his death, he had a wide-ranging interest in the mathematical and statistical aspects of physical analysis, and, in particular, the application of probability and calculus to experimental results in nuclear physics and particle physics. He is known for his statistical analysis methods for cosmic rays. Specifically, during his stay in Dublin, he completed his classic monograph on cosmic rays (1948)[2] and published important monographs on particle showers (1950), introducing the eponymous joint probability densities—now called Jánossy densities—in the theory of random point processes.[3]

Until the 1950s, the most important field in the research of high-energy particles was the investigation of cosmic radiation. But as the large accelerators started to take over the leading role, Jánossy turned away from the investigation of cosmic radiation and focussed on theoretical problems of quantum mechanics, the dual character of light, as well as the theory of relativity.

Together with KFKI colleagues, he carried out a famous low-intensity interference experiment, a quantum-mechanical process in which low-intensity photon beams interfere with themselves—although the experiments originally sought to refute this possibility. These interference results involving a small number of photons are significant for appreciating the quantum nature of light. The measurements he carried out in connection with the dual character of light (self-interference of few photons) supplied results that were expected on the basis of quantum mechanics; yet, due to the requirements of extremely high accuracy, measurements of this kind had not been carried out before Jánossy. Spurred by this famous photon experiment, Schrödinger was quick to write a letter, in which he emphasized the importance of the result. In both the measurement of cosmic radiation and the low intensity interference experiment, precision of the correct results is of fundamental importance, which justified Jánossy's interest in the statistical evaluation of measurements.

In the last one and a half decades of his theoretical activity, he was engaged in the hydrodynamic model of quantum mechanics and the interpretation problems of the theory of relativity. He had an interest in the physics philosophy of interpretation, and practical aspects of physics education and the promotion of physics as well. He was also active in the organization of public scientific. From 1953 until his death, he co-edited the Hungarian Physical Journal, and he was a member of the editorial board of Acta Physica Hungarica and Hungarian Science, as well as Foundations of Physics.

Memberships and awards

Member (1950) and, later, vice-president (1961 to 1973) of the Hungarian Academy of Sciences; member of the Bulgarian Academy of Sciences (1961), the Royal Irish Academy of Sciences (1948), the Mongolian Academy of Sciences and the Academy of Sciences of the German Democratic Republic (1954).

Awarded the Kossuth Prize (1951); Academic Gold Medal (1972); Vice chair of the Eötvös Physical Society (1950–1969); chair of the National Atomic Energy Commission. From 1966 till his death, president of the Hungarian Stamp Collectors' Association.

The Eötvös Physical Society in 1994 established the Jánossy Lajos Award, for outstanding research in the field of theoretical and experimental physics.

Main works

See also

References

  1. ↑ Király, P. T. (2013). "Two centenaries: The discovery of cosmic rays and the birth of Lajos Jánossy". Journal of Physics: Conference Series 409: 012001. doi:10.1088/1742-6596/409/1/012001.
  2. ↑ Janossy, L. (1948): Cosmic Rays, Oxford, Clarendon Press, p. 424 Online copy
  3. ↑ Janossy, L. (1950): "On the absorption of a nucleon cascade", Proc. Roy. Irish Acad. Sci., A53, 181–188; Janossy, L. (1952): "Studies on the Theory of Cascades," Acta phys. Acad. sci. Hung., 2 289–333; Janossy, L. and Messel, H. (1950): "Fluctuations of the electron – photon cascade – moments of the distribution", Proc. Phys. Soc. (London)., A63, 1101–1115.     Soshnikov, A. (2004). "Janossy Densities of Coupled Random Matrices". Communications in Mathematical Physics 251 (3): 447–471. arXiv:math-ph/0309019. Bibcode:2004CMaPh.251..447S. doi:10.1007/s00220-004-1177-5.; Borodin, A.; Soshnikov, A. (2003). "Janossy Densities. I. Determinantal Ensembles". Journal of Statistical Physics 113 (3/4): 595. doi:10.1023/A:1026025003309.

Further reading

External links