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Moscow, Russia

Akhmedov E.T.,ITEP
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. Source

MacHet B.,University Pierre and Marie Curie | Vysotsky M.I.,ITEP
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. Source

Simonov Yu.A.,ITEP
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. Source

Zubkov M.A.,ITEP
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. Source

Mironov A.,RAS Lebedev Physical Institute | Morozov A.,ITEP
Nuclear Physics B | Year: 2010

We consider the AGT relation (Alday et al., 2009 [1]), 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. Source

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