News Article | February 15, 2017
Ovsat Abdinov, member of the Azerbaijan National Academy of Sciences (ANAS), died on 29 October at the age of 72, after a long illness. He was born in Belokan city, Azerbaijan, graduated from Baku State University in 1966, and defended his PhD thesis in 1972. It is impossible to overstate the impact that Abdinov had in the creation and development of high-energy physics in Azerbaijan. His wide knowledge, inexhaustible energy, talent in organisation and search for young specialists led to the creation of his own school in this field that serves as an example for future generations. Scientifically, Abdinov’s main interest was the theoretical description of hadron-nuclear interaction processes. He was the first to propose a hypothesis of the cluster formation in light nuclei, which was later experimentally proven. The laboratory he headed at ANAS Institute of Physics collaborated initially with the Joint Institute for Nuclear Research (JINR) in Dubna and the Institute of High Energy Physics (IHEP) in Serpukhov, both in Russia, followed by CERN. The creation and expansion of relations between Azerbaijan and CERN paved the way for the participation of Azerbaijan scientists in the LHC, but this did not interrupt connections with Dubna: Abdinov was a staff member of JINR, deputy of authorised representative of the government of Azerbaijan Republic in JINR, and a member of JINR Scientific Council. The creation of Azerbaijan’s first Worldwide LHC Computing Grid segment also owes its thanks to Abdinov. Abdinov was a famous scientific representative of the Azerbaijan intelligentsia. He was an organiser and invited speaker at international conferences, a presenter of high-level reports and the winner of numerous research grants both in the former Soviet Union and in Azerbaijan. He dedicated almost 20 years of his scientific activity to investigations carried out within the ATLAS collaboration. We hope that his work will be continued by his scientific heirs and further benefit Azerbaijan high-energy physics. Malcolm Derrick, a long-time leader in the Argonne high-energy physics (HEP) division, passed away on 31 October after a long illness. Born in Hull, UK, in 1933, Malcolm received his BSc and PhD degrees in physics from the University of Birmingham. After working on the cyclotron at Carnegie Tech, he moved to Oxford University in 1962 to help establish a bubble-chamber group working at CERN. In 1963 he moved to Argonne National Laboratory to work on the 12 GeV ZGS synchrotron then in construction. While working on several bubble-chamber experiments with the 30 inch chamber, Malcolm’s main interest was in establishing a programme of neutrino physics using the 12 foot bubble-chamber then being built. He was spokesman for the first experiment using the deuterium-filled chamber, which produced several important results including the first measurement of the axial-vector form factor in muon neutrino–neutron quasi-elastic scattering. This result was verified by later BNL and FNAL experiments. Malcolm served on two occasions as HEP division director and was always a source of good career advice. He enthusiastically supported the division's collaboration with the University of Minnesota to build an underground detector to search for proton decay in the Soudan Mine in Minnesota. This resulted in a rich programme of neutrino physics with a series of multi-kiloton detectors and in new underground laboratories at Soudan, using both atmospheric neutrinos and Fermilab neutrino beams. The important physics produced by the MINOS programme is the direct result of these early experiments. After the closure of the ZGS programme, Malcolm initiated Argonne participation in two important experiments: HRS at the PEP collider at SLAC, where he proposed using the superconducting magnet of the 12 foot bubble chamber as the solenoid for the HRS spectrometer, and the ZEUS experiment at the HERA collider in DESY. Malcolm took sabbatical leave at University College London and later at DESY, where he served as physics chairman and oversaw such activities as physics publications. A gifted speaker, he served on several review committees and was a HEPAP member and an active participant in the Snowmass Conferences. He retired in 2006. Besides being a brilliant physicist, Malcolm had a knack for entertaining his guests with stories about his life and endless anecdotes about history and philosophy. His spare time was spent reading good books, fine dining and listening to classical music. Malcolm leaves behind his wife Eva and his many children and grandchildren. He will be missed by all who knew and loved him. Russian physicist Valery Dmitrievich Khovanskiy passed away in Moscow on 7 September. A veteran of Russian experimental high-energy physics and long-time leader of the ITEP team in ATLAS, he will be remembered not only as an energetic contributor to the CERN neutrino and LHC programmes, but also as an honest and principled person who loved science and life. Valery was born in Sverdlovsk in the former USSR, and received his PhD (for the study of cumulative effects in πN-interactions) at the Institute of Experimental and Theoretical Physics (ITEP, Moscow) in 1969. Since then, his main scientific interests were in the fields of neutrino physics, novel particle-detection methods and hadron collider physics. In the first Russian accelerator neutrino experiment at the Serpukhov 70 GeV proton synchrotron (IHEP-ITEP, 1970–1978), Valery lead the detector construction and studied neutrino and antineutrino interactions to validate the then very young quark-parton model. In the late 1970s, Valery joined the CERN experimental neutrino programme at the SPS and PS, and became one of the senior scientists of the CHARM, PS-181, CHARM-2 and CHORUS experiments devoted to a systematic study of neutral currents, and the search for new particles and neutrino oscillations. From 1990 onwards, he participated in the ATLAS experiment. His group was active in the preparation of the Letter of Intent, working on the concept of radiation-resistant forward calorimeters, and, from 1995 to 2009, worked on the construction and commissioning of the ATLAS liquid-argon forward calorimeters, providing the major part of the tungsten electrodes. From 1995 to 2012, Valery was the leader of the neutrino-physics laboratory at ITEP. He served on the LHCC from 1992 to 1994 and for a long period on the Russian government’s commission on fundamental research. He was also one of the founders and lecturers of the famous ITEP Winter School of Physics. Valery had a vivid individuality and was invariably good humoured. His many pupils, colleagues and friends admired him and he will be very much missed. Edmund (Ted) Wilson, a well-known figure in the world of particle accelerators and former director of the CERN Accelerator School (CAS), died after a short illness on 3 November. The son of a schoolteacher in Liverpool, UK, he graduated in physics at the University of Oxford in 1959 and immediately joined the nearby Rutherford Appleton Laboratory. His first stay at CERN was in 1962–1963 and he returned in 1967 as a fellow, working in Werner Hardt’s group on the design of the booster for the new large synchrotron: the “300 GeV” machine, later to become the Super Proton Synchrotron (SPS). He became the right-hand man of John Adams in 1969, helping him to prepare the project for approval by CERN Council, which was given in 1971. He became one of the first staff members of the new “300 GeV laboratory” set up for the construction of the SPS. In 1973–1974, at the request of Adams, Ted spent a sabbatical year at Fermilab to work on the commissioning of the “main ring”, a machine very similar to the SPS. The lessons he learnt there would prove essential for the smooth commissioning of the SPS, for which he was responsible a few years later. Following the approval in 1978 of the bold proposal of Carlo Rubbia to turn the SPS into a part-time proton–antiproton collider, Ted started working on how to convert the machine from a synchrotron to a storage ring. He later worked on the design and construction of CERN’s antiproton complex: first the antiproton accumulator, to which a second ring, the antiproton collector, was later added. Ted was a natural and gifted teacher. During the days of SPS construction he ran a series of courses on accelerator theory for members of the 300 GeV laboratory, which evolved into the book An Introduction to Particle Accelerators. Following his appointment as CAS director in 1992, he was responsible for organising 25 schools, in addition to special schools in India, China and Japan. He also coauthored a fascinating book on the history of particle accelerators and their applications: Engines of Discovery, a Century of Particle Accelerators. On his retirement, Ted renewed his association with Oxford University by becoming a guest professor at the John Adams Institute of Accelerator Physics, where he taught and supervised students. He has helped to bring on a new generation of machine builders. Ted Wilson will be sorely missed by the world’s accelerator community. He will always be remembered for his impish smile and his dry sense of humour. He is survived by his wife Monika, his three children and five grandchildren.
Dolotin V.,ITEP |
Nuclear Physics B | Year: 2014
We continue to develop the tensor-algebra approach to knot polynomials with the goal to present the story in elementary and comprehensible form. The previously reviewed description of Khovanov cohomologies for the gauge group of rank N-. 1. = 1 was based on the cut-and-join calculus of the planar cycles, which are involved rather artificially. We substitute them by alternative and natural set of cycles, not obligatory planar. Then the whole construction is straightforwardly lifted from SL(2) to SL(N) and reproduces Khovanov-Rozansky (KR) polynomials, simultaneously for all values of N. No matrix factorization and related tedious calculations are needed in such approach, which can therefore become not only conceptually, but also practically useful. © 2013 The Authors.
MacHet B.,University Pierre and Marie Curie |
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2011
We obtain the following analytical formula which describes the dependence of the electric potential of a pointlike charge on the distance away from it in the direction of an external magnetic field B: Φ(z)=e/|z|[1-exp(- √6me2|z|)+exp(-√(2/π)e3B+6me2|z|)]. The deviation from Coulomb's law becomes essential for B>3πBcr/α=3πme2/ e36×1016G. In such superstrong fields, electrons are ultrarelativistic except those which occupy the lowest Landau level (LLL) and which have the energy ε02=me2+pz2. The energy spectrum on which LLL splits in the presence of the atomic nucleus is found analytically. For B>3πB cr/α it differs substantially from the one obtained without accounting for the modification of the atomic potential. © 2011 American Physical Society.
Modern Physics Letters A | Year: 2010
Using properly defined Feynman propagator we obtain nonzero imaginary contribution to the scalar field effective action in even-dimensional de Sitter space. Such a propagator follows from the path integral in de Sitter space and obeys composition principle proposed in arXiv:0709.2899. The obtained expression for the effective action shows particle production with the GibbonsHawking rate. © 2010 World Scientific Publishing Company.
Mironov A.,RAS Lebedev Physical Institute |
Nuclear Physics B | Year: 2010
We consider the AGT relation (Alday et al., 2009 ), expressing conformal blocks for the Virasoro and W-algebras in terms of Nekrasov's special functions, in the simplest case of the 4-point functions for the first non-trivial W3 algebra. The standard set of Nekrasov functions is sufficient only if additional null-vector restriction is imposed on a half of the external W-primaries and this is just the case when the conformal blocks are fully dictated by W-symmetry and do not depend on a particular model. Explicit checks confirm that the AGT relation survives in this restricted case, as expected. © 2009 Elsevier B.V. All rights reserved.
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2012
The definition of topological invariants N 4, N 5 suggested in M.A. Zubkov and G.E. Volovik, Nucl. Phys.NUPBBO0550-3213 B860, 295 (2012)10.1016/j.nuclphysb.2012.03.002 is extended to the case when there are zeros and poles of the Green function in momentum space. It is shown how to extend the index theorem suggested by Zubkov and Volovik to this case. The nonanalytical exceptional points of the Green function appear in the intermediate vacuum, which exists at the transition line between the massive vacua with different values of topological invariants. Their number is related to the jump ΔN 4 across the transition. The given construction is illustrated by momentum space topology of the lattice model with overlap fermions. The fermion excitations that appear in the vicinities of the given points cannot be considered as usual fermion particles. We, therefore, feel it is appropriate to call them generalized unparticles. This notion is, in the general case, different from the Georgi's unparticle. However, in the case of lattice overlap fermions, the propagator of such excitations is indeed that of the fermionic unparticle suggested in M. Luo and G. Zhu, Phys. Lett. B 659, 341 (2008)PYLBAJ0370-269310.1016/j.physletb.2007.10.058. © 2012 American Physical Society.
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2012
A new mechanism of baryon-antibaryon production via nonperturbative double-pair creation in intermediate mesons is proposed, and the theory contains no fitting parameters. It is shown that near-threshold resonances are responsible for enhancements in electroproduction cross sections: ψ(4S) for Λc+Λc- and Υ(6S) for Λ bΛ ̄b. An admixture of intermediate D-wave resonances produces angular dependence in the differential cross section and can explain unusual behavior of the ratio G E/G M for the proton. © 2012 American Physical Society.
Nuclear Physics B | Year: 2011
We propose a numerical method for resummation of perturbative series, which is based on the stochastic perturbative solution of Schwinger-Dyson equations. The method stochastically estimates the coefficients of perturbative series, and incorporates Borel resummation in a natural way. Similarly to the "worm" algorithm, the method samples open Feynman diagrams, but with an arbitrary number of external legs. As a test of our numerical algorithm, we study the scale dependence of the renormalized coupling constant in a theory of one-component scalar field with quartic interaction. We confirm the triviality of this theory in four and five space-time dimensions, and the instability of the trivial fixed point in three dimensions. © 2011 Elsevier B.V.
Buividovich P.V.,University of Regensburg |
Physical Review B - Condensed Matter and Materials Physics | Year: 2012
We study the effect of Coulomb interaction between charge carriers on the properties of graphene monolayer, assuming that the strength of the interaction is controlled by the dielectric permittivity of the substrate on which the graphene layer is placed. To this end, we consider the tight-binding model on the hexagonal lattice coupled to the noncompact gauge field. The action of the latter is also discretized on the hexagonal lattice. Equilibrium ensembles of gauge field configurations are obtained using the hybrid Monte Carlo algorithm. Our numerical results indicate that at sufficiently strong coupling, that is, at sufficiently small substrate dielectric permittivities ε 4 and at sufficiently small temperatures T 104K, the symmetry between simple sublattices of hexagonal lattice breaks down spontaneously and the low-frequency conductivity gradually decreases down to 20-30% of its weak-coupling value. On the other hand, in the weak-coupling regime (with ε 4), the conductivity practically does not depend on ε and is close to the universal value σ0=1/4. © 2012 American Physical Society.
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2010
We investigate the lattice Weinberg-Salam model without fermions numerically for the realistic choice of coupling constants correspondent to the value of the Weinberg angle θW∼30°, and bare fine structure constant around α∼1150. We consider the values of the scalar self-coupling corresponding to Higgs mass MH∼100, 150, 270 GeV. It has been found that nonperturbative effects become important while approaching continuum physics within the lattice model. When the ultraviolet cutoff Λ=πa (where a is the lattice spacing) is increased and achieves the value around 1 TeV, one encounters the fluctuational region (on the phase diagram of the lattice model), where the fluctuations of the scalar field become strong. The classical Nambu monopole can be considered as an embryo of the unphysical symmetric phase within the physical phase. In the fluctuational region quantum Nambu monopoles are dense, and therefore, the use of the perturbation expansion around the trivial vacuum in this region is limited. Further increase of the cutoff is accompanied by a transition to the region of the phase diagram, where the scalar field is not condensed (this happens at the value of Λ around 1.4 TeV for the considered lattice sizes). Within this region further increase of the cutoff is possible, although we do not observe this in detail due to the strong fluctuations of the gauge boson correlator. Both above mentioned regions look unphysical. Therefore we come to the conclusion that the maximal value of the cutoff admitted within lattice electroweak theory cannot exceed the value of the order of 1 TeV. © 2010 The American Physical Society.