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Semenov A.G.,Pn Lebedev Physics Institute | Semenov A.G.,National Research University Higher School of Economics
Physics Letters, Section A: General, Atomic and Solid State Physics | Year: 2016

In this letter we investigate the phenomenon of macroscopic quantization and consider particle on the ring interacting with the dissipative bath as an example. We demonstrate that even in presence of environment, there is macroscopically quantized observable which can take only integer values in the zero temperature limit. This fact follows from the total angular momentum conservation combined with momentum quantization for bare particle on the ring. The nontrivial thing is that the model under consideration, including the notion of quantized observable, can be mapped onto the Ambegaokar-Eckern-Schon model of the single-electron box (SEB). We evaluate SEB observable, originating after mapping, and reveal new physics, which follows from the macroscopic quantization phenomenon and the existence of additional conservation law. Some generalizations of the obtained results are also presented. © 2016.

Adorno T.C.,University of Sao Paulo | Gitman D.M.,University of Sao Paulo | Shabad A.E.,Pn Lebedev Physics Institute | Vassilevich D.V.,Federal University of ABC | Vassilevich D.V.,Saint Petersburg State University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2011

It has been argued that in noncommutative field theories, the sizes of physical objects cannot be taken smaller than an "elementary length" related to noncommutativity parameters. By gauge covariantly extending field equations of noncommutative U(1) theory to cover the presence of external sources, we find electric and magnetic fields produced by an extended static charge. We find that such a charge, apart from being an ordinary electric monopole, is also a magnetic dipole. By writing off the existing experimental clearance in the value of the lepton magnetic moments for the present effect, we get the bound on noncommutativity at the level of 104TeV. © 2011 American Physical Society.

Shabad A.E.,Pn Lebedev Physics Institute | Usov V.V.,Weizmann Institute of Science
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2011

In nonlinear electrodynamics, by implementing the causality principle as the requirement that the group velocity of elementary excitations over a background field should not exceed the speed of light in the vacuum c=1, and the unitarity principle as the requirement that the residue of the propagator should be nonnegative, we establish the positive convexity of the effective Lagrangian on the class of constant fields, also the positivity of all characteristic dielectric and magnetic permittivity constants that are derivatives of the effective Lagrangian with respect to the field invariants. Violation of the general principles by the one-loop approximation in QED at exponentially large magnetic field is analyzed, resulting in complex energy ghosts that signal the instability of the magnetized vacuum. Superluminal excitations (tachyons) appear, too, but for the magnetic field exceeding its instability threshold. Also other popular Lagrangians are tested to establish that the ones leading to spontaneous vacuum magnetization possess wrong convexity. © 2011 American Physical Society.

Galaktionov A.V.,Pn Lebedev Physics Institute | Zaikin A.D.,Karlsruhe Institute of Technology
Physical Review B - Condensed Matter and Materials Physics | Year: 2010

We derive a microscopic effective action for superconducting contacts with arbitrary transmission distribution of conducting channels. Provided fluctuations of the Josephson phase remain sufficiently small our formalism allows to fully describe fluctuation and interaction effects in such systems. As compared to the well-studied tunneling limit our analysis yields a number of qualitatively distinct features which occur due to the presence of subgap Andreev bound states in the system. We investigate the equilibrium supercurrent noise and evaluate the electron-electron interaction correction to the Josephson current across superconducting contacts. At T=0 this correction is found to vanish for fully transparent contacts indicating the absence of Coulomb effects in this limit. © 2010 The American Physical Society.

Golubev D.S.,Karlsruhe Institute of Technology | Zaikin A.D.,Karlsruhe Institute of Technology | Zaikin A.D.,Pn Lebedev Physics Institute
Physical Review B - Condensed Matter and Materials Physics | Year: 2010

We argue that Coulomb interaction can strongly influence nonlocal electron transport in normal-superconducting-normal structures and emphasize direct relation between Coulomb effects and nonlocal shot noise. In the tunneling limit nonlocal differential conductance is found to have an S-like shape and can turn negative at nonzero bias. At high transmissions crossed Andreev reflection yields positive noise cross correlations and Coulomb antiblockade of nonlocal electron transport. © 2010 The American Physical Society.

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