Iosif Bentzionovich Khriplovich

Iosif Khriplovich, a renowned Soviet/Russian physicist, died on 26 September 2024 at the age of 87. He was born in 1937 in Kiev (Ukraine) into a Jewish family. After graduating from Kiev University, he moved to Siberia, to the newly built Academgorodok. From 1959 until 2014, he was a prominent member of the theory department at the Budker Institute of Nuclear Physics. He combined his research activity with teaching at Novosibirsk University, where he also held a professorship in theoretical physics in 1983–2009. In 2014, he moved to St. Petersburg to take up a professorial position at St. Petersburg University. Since 2000, Khriplovich had been a corresponding member of the Russian Academy of Sciences. He was awarded the Silver Dirac Medal by the University of New South Wales (Sydney) and the Pomeranchuk Prize by the Institute for Theoretical and Experimental Physics (Moscow).

In his paper published in 1969, he was the first to discover the phenomenon of antiscreening in the SU(2) Yang–Mills theory by calculating the first loop correction to the charge renormalization. This immediately translates into the crucial first coefficient (-22/3) of the Gell-Mann–Low function and asymptotic freedom of the theory. Regretfully, Khriplovich did not follow this interpretation of his result, even after the key SLAC experiment on deep inelastic (e,p) scattering, with Bjorken scaling and its subsequent partonic interpretation by Feynman. So the honor of discovery of asymptotic freedom in QCD went to three Nobel laureates for their famous papers, published in 1973, but who seemingly did not know about Khriplovich’s calculations.

The originality of Khriplovich’s approach was the Yang–Mills quantization in the “physical” Coulomb gauge, requiring neither Faddeev–Popov ghosts nor the vertex renormalization. Besides the SU(2) triplet of transverse gluons, there is the triplet of Coulomb fields providing instantaneous, non-dispersive interactions. The negative charge renormalization (antiscreening) was shown to come from just one diagram, with a loop made of Coulomb exchange and one transverse gluon. This diagram has a vanishing imaginary part, so the contribution is not dispersive.

In the early 1970s, Khriplovich’s interests turned to the fundamental questions on the way toward the standard model. One of them was whether the electroweak theory is described by the Weinberg–Salam model, with neutral currents interacting with Z bosons, or the Georgi–Glashow model without them. While the neutrino scattering on nucleons was confirmed pretty soon, the electron interaction with nucleons was still unchecked. One practical way to find out was to study atomic spectroscopy, looking for any mixing between states of opposite parity. Actively entering this new area for him, Khriplovich and his (then) students worked out quantitative predictions for the rotation of laser light polarization due to the weak interaction of electrons with nucleons. Their predictions were triumphantly confirmed in experiments, firstly by Barkov and Zolotarev, at the Budker Institute. The same parity-violating interaction was later observed by the SLAC experiment of 1978, proving the Z-exchange and the Weinberg–Salam model beyond any doubts.

The work of Khriplovich and his group in this area significantly advanced the theory of many-electron atoms and contributed to the subsequent studies of the violation of fundamental symmetries in processes involving elementary particles, atoms, molecules, and atomic nuclei. His students and later close collaborators, such as Victor Flambaum, Oleg Sushkov, and Maxim Pospelov, grew in strong physicists with new ideas and important achievements in various subfields of theoretical physics. At the same time, he could sharply cut his relations with scientists of any rank if he felt their behavior did not fit his high ethical standards.

Yulik—as his family and friends affectionately called him—had his own style in physics: He was feisty, tried to avoid mainstream crowds, and focused on issues where he could become a trailblazer. This is why he became engaged in Yang–Mills theories in the 1960s, at a time when very few people were interested in them. At the dawn of the Weinberg–Salam model, in 1973, Khriplovich and Vainshtein derived the first solid limit on the mass of the charm quark that was unexpectedly discovered the next year, 1974.

Yulik is survived by his wife Eva and his children from previous marriages: Marina, Vladimir, Inna, and stepson Eugene. Our condolences go to them and to Yulik’s friends and colleagues.

We conclude by referring to the picture in which Yulik is smiling, as we would like to remember him.

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