Nikita Alexeevich Sveshnikov, Associate Professor at the Department of Physics
of
Moscow State University, a brilliant scientist and educator, untimely died on
July 29 1997, aged 44.
As a graduate of the Chair of Quantum Statistics in the Department of Physics of
MSU, headed by Professor N.N. Bogoliubov, Nikita Sveshnikov started his
scientific
endeavors early in his undergraduate years. In his Diploma work and then PhD
thesis under the supervision of Professor D.V. Shirkov he studied the problem of
infrared divergences in Quantum Field Theory. Such divergences known since 1930s
have acquired a special interest in connection with the problem of confinement
of
quarks in Quantum Chromodynamics. N.A. Sveshnikov was the first to realise that
a
consistent application of the method of asymptotic dynamics, which exactly
describes interaction processes of particles at asymptotically large times, to
massless models of non-Abelian symmetry may give rise to nontrivial restrictions
on
the spectrum of the theory. In a series of works in late 1970s - early 1980s he
has
shown that in a model charge symmetric theory there are no states with non-zero
non-Abelian charge, and in the framework of perturbative Quantum
Chromodynamics there are no asymptotic states corresponding to free quarks, what
may be interpreted as an indication for confinement. Later on during his
scientific
career, Nikita Alexeevich turned again to these related problems of infrared
divergences, asymptotic dynamics and confinement, and continued to work on them
productively to the last day of his life.
An important contribution by N.A. Sveshnikov to the Quantum Gauge Field Theory
was in recognition of the special role of surface terms and delocalised
observables
(variables at infinity) in Quantum Gluodyna-
mics formulated in the physical
Fock-Schwinger gauge. He also developed elegant functional integration
techniques
for adequately taking such variables into account and studying the dependence of
the partition function on the boundary conditions. This has allowed him to
explain the
mechanism of the confinement-deconfinement phase transition in
SU(N)-gluodynamics. He has shown that below the critical temperature only the
zero
value of the colour charge flux in any angular cone at spatial infinity is
statistically
realisable. The latter is equivalent to the `no-escape' condition of colour in
any
angular direction and mathematically expresses the singletness of physical
observables with respect to the subgroup of gauge transformations at infinity,
which
in turn ensures fulfillment of the Wilson confinement criterion. The numerical
value
for the string tension coefficient predicted by this theory is close to that
from Monte
Carlo lattice simulations.
These works had a natural development in later results for the theory of jet
reactions
at high energies obtained in mid-1990s. In particular, the connection of the
main
class of observables to the energy-momentum tensor was established.
It should be noteed that the supreme theoretical abilities of Nikita Alexeevich
enabled him to construct consistent theories in fields which until then were
only
amenable to half-phenomenological treatments. The mathematical gift was perhaps
one of his strongest points - one is tempted to think of a genetic
predisposition.
Sometimes it might even seem that mathematics obscures the physical side for
him.
However, such an impression is certainly wrong - the physics of any phenomenon
was always on the forefront of his thinking.
As time went on, the scope of Nikita Alexeevich's scientific interests expanded.
His
extensive erudition and superlative skill allowed him to work successfully on a
few
pivotal theoretical problems from different branches of physics, and not physics
alone, simultaneously. For example, he studied propagation of information in
distributed systems. In particular, he demonstrated that a population of neurons
not
directly interacting with each other, but only via secreting a special chemical
into
their common environment and responding to local variations in its
concentration,
are capable of carrying out rather complex functions in transferring
information.
Also, more complicated systems with large organic molecules as active units and
messenger-molecules carrying information about the addressee code were studied.
Sadly, untimely death interrupted the diverse scientific studies of Nikita
Alexeevich.
He left many unpublished or partially published results at different stages of
completion, which will continue to be submitted to press by his colleagues and
students. Among his late works it is interesting to mention the original study
of
special non-Pauli states in three-body systems, the development of the theory of
quantum bound states embedded in continuum, the study of classical analogues of
such states: bound states without classical turning points, and the development
of
methods for construction of isospectral Hamiltonians.
For Nikita Alexeevich scientific research was always inseparable from teaching.
The
latter was one of the most important sides of his activity. It would be no
exaggeration
to say that he put his heart into teaching students from the Chair of Quantum
Theory
and High Energy Physics in the Department of Physics of MSU, headed by Professor
A.A. Logunov, and the Division of Nuclear Physics as a whole, where he was
Deputy
Head for many years. He liked and knew how to teach well, and his pedagogical
talent matured with every year. For the current generation of students of the
Department of Physics Nikita Alexeevich was one of the best loved lecturers.
Anyone, who had the privilege of knowing him, will remember how rapidly Nikita
Alexeevich perfected as a University teacher and researcher. This was clear to
his
undergraduate and postgraduate students, the number of which constantly
increased. During the past few years he was giving a full-year special course on
Quantum Field Theory. His contribution to the organisation of various other
topical
courses, such as e.g. the course `Quantum Field Theory for Experimentalists'
given
by Professor D.V. Shirkov, was also invaluable. Nikita Alexeevich had a striking
ability to carry the weight of organisational and public duties with elegance
and ease,
and every job was invariably done in the most efficient and comprehensive
manner.
One such duty, closely related to research and teaching, was the job into which
Nikita
Alexeevich put his heart during the last 12 years. In 1985 he helped organising
the
first Summer School for Young Scientists on Quantum Field Theory and High Energy
Physics convened by the Nuclear Physics Institute of MSU. Gradually, this Summer
School grew into an annual international event, widely known in Russia and
worldwide as the QFTHEP Workshop. Since the first School and every year Nikita
Alexeevich was the key figure in the Organising Committee. His admirable
presentations and numerous discussions he organised will be long remembered by
many participants of QFTHEP. As usual, he played a most active role in the
preparation of the 12-th QFTHEP Workshop, which took place already after his
demise in September 1997 in Samara and was dedicated to his memory.
N.A. Sveshnikov was, despite his young age, a person to whom people came for
advice and opinion. His sharp wit, deep knowledge, and importantly, outgoing
personality helped to many in their problems. Nikita Alexeevich was also a
rather
modest and self-disciplined person. He was a man of many talents, among which
the
art of human relations was intrinsic to him. It was no accident that he always
played
an important role in the social life of the Department of Physics in Moscow
State
University.
Nikita Alexeevich, our dear colleague and good friend, was generously blessed
with
many talents. The words `TALENT' and `CHARM' would perhaps characterise him
best of all. It would be wrong to say that he left this life, for his
accomplishments,
scientific results, ideas and dreams will stay with us for ever.
Friends, colleagues and disciples will cherish the grateful memory of this
remarkable
man.
V.A. Rubakov, V.I. Savrin, A.A. Slavnov,
V.I. Trukhin, O.A. Khrustalev, D.V. Shirkov