Professor Iosif Khriplovich
The Silver Dirac Medal for the Advancement of Theoretical Physics
is awarded to commemorate the visit to the University in 1975 of
Professor P.A.M. Dirac, one of the greatest theoretical physicists
of the twentieth century. Two medals were awarded in 2004.
The first medal was awarded to Professor Edward Shuryak, the Director
of the Institute for Nuclear Theory at the State University of New
York at Stonybrook. He proposed the so-called ‘instanton liquid’
model of the QCD vacuum, considering the “vacuum” (ground
state) as an ensemble of interacting non-linear fluctuations called
instantons. This picture has recently been shown to predict the
spectrum of elementary particles very well. Another theme of his
research has been the behaviour of matter at extreme temperatures
and pressures, when ‘elementary’ particles melt to form
a completely new phase of matter, called the ‘Quark-Gluon
Plasma’ (QGP), He showed that under such conditions the ‘colour’
charges of the quarks are screened rather than confined.
Professor Shuryak gave a public Dirac lecture on the topic ‘Quark-Gluon
Plasma: Part of the Big Bang Recreated in the Laboratory’.
To observe and study the Quark-Gluon Plasma (QGP), a dedicated collider
complex RHIC has been built, at Brookhaven National Laboratory.
Two gold nuclei, accelerated to 200 GeV per nucleon each, are smashed
together, producing a small fireball of QGP. It was found that it
explodes hydrodynamically, in what was called a Little Bang, with
many amusing parallels to the Big Bang.
The second medal was awarded to Professor Iosif B. Khriplovich,
Chief Scientist at the Budker Insititute of Nuclear Physics at Novosibirsk
in Russia, and Chair of Theoretical Physics at Novosibirsk University.
Professor Khriplovich is a Member of the Russian Academy of Science.
His most striking discovery is that in so-called non-Abelian gauge
theories the interaction is reduced at small distances (‘asymptotic
freedom’). The Standard Model of elementary particles was
constructed on the basis of these theories. Khriplovich published
his calculation in 1969 for the SU(2) theory describing the weak
interaction part of the Standard Model. Four years later a similar
result was obtained for the strong interaction part of the Standard
Model (Quantum Chromodynamics) by Politzer, Gross and Wilczek. The
discovery of asymptotic freedom made a revolution in high energy
physics, and last year Politzer, Gross and Wilczek were awarded
the Nobel Prize for this work. Khriplovich has also made an important
contribution to the discovery of violations of the fundamental symmetry
– parity – in atoms, and the discovery of an electromagnetic
moment violating fundamental symmetries – the nuclear anapole
moment. He gave a public Dirac Lecture on ‘Black Holes, Classical
and Quantum’, demonstrating that black holes should possess
entropy and temperature. Thus, black holes should radiate.