189 research outputs found
Theory of Lee-Naughton-Lebed\u27s Oscillations in Moderately Strong Electric Fields in Layered Quasi-One-Dimensional Conductors
No full textIn framework of some extension of the quasi-classical Boltzmann kinetic equation, we show that a moderately strong electric field splits the so-called Lee-Naughton-Lebed\u27s magnetoconductivity maxima in a layered quasi-one-dimensional conductor, if we use some reasonable approximation to the equation. By means of the above mentioned approximation, we obtain analytical formula for conductivity in high magnetic and moderately high electric fields and show that it coincides with the hypothetical formula as well as adequately describes the pioneering experimental data by Kobayashi et al. [K. Kobayashi, M. Saito, E. Omichi, and T. Osada, Phys. Rev. Lett. \textbf{96}, 126601 (2006)].1 figur
Gravity at Finite Temperature, Equivalence Principle, and Local Lorentz Invariance
No full textIn this Chapter we illustrate the close connection between the violation of
the weak equivalence principle typical of gravitational interactions at finite
temperature, and similar violations induced by a breaking of the local Lorentz
symmetry. We also discuss the physical implications of the effective repulsive
forces possibly arising in such a generalized gravitational context, by
considering, for an illustrative purpose, a quasi-Riemannian model of gravity
with rotational symmetry as the local gauge group in tangent space
Quantum limit in a quasi-one-dimensional conductor in a high tilted magnetic field
No full textRecently, we have suggested Fermi-liquid-non-Fermi-liquid angular crossovers that may exist in quasi-one-dimensional (Q1D) conductors in high tilted magnetic fields (see A. G. Lebed, Phys. Rev. Lett. 115, 157001 (2015)). All calculations in the Letter were done by using the quasiclassical Peierls substitution method, whose applicability in high magnetic fields was questionable. Here, we solve a fully quantum mechanical problem and show that the main qualitative conclusions of the work cited above are correct. In particular, we show that in high magnetic fields, applied along one of the two main crystallographic axis, we have 2D electron spectrum, whereas, for directions of high magnetic fields far from the axes, we have 1D electron spectrum. The latter is known to promote non-Fermi-liquid properties. As a result, we expect the existence of Fermi-liquid-non-Fermi-liquid angular crossovers or phase transitions. Electronic parameters of Q1D conductor (Per)(2)Pt(mnt)(2) show that such transitions can appear in feasible high magnetic fields of the order of H similar or equal to 20-25 T.12 month embargo; published online: 17 October 2017This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]
Method to Reveal and Investigate Almost 2D Fermi Surfaces in Layered Conductors: Universal Resistivity in a Parallel Magnetic Field
No full textWe suggested an original method to investigate the Fermi surfaces (FSs) in the quasi-two-dimensional conductors some time ago [A.G. Lebed and N.N. Bagmet, Phys. Rev. B 55, R8654 (1997)]. It was based on a consideration of a perpendicular conductivity in quasi-two-dimensional metals in parallel magnetic fields in the framework of the Boltzmann kinetic equation, where it was shown that the conductivity was independent on impurities. In this paper, we demonstrate that the above mentioned result is much more general than the kinetic equation and can be obtained even in a fully quantum mechanical case. We suggest to investigate this possible phenomenon in the quasi-two-dimensional organic, high- Tc , and some others superconductors in a metallic phase to judge if the Fermi liquid picture is valid for them or not. If the Fermi liquid picture is valid, then study of the perpendicular resistivity in the rotated parallel magnetic field allows to extract important information about the two-dimensional Fermi surfaces. © 2023, The Author(s).Open access articleThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]
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Violation of the Einstein's equivalence principle for a composite quantum body
No full textRecently, we have started to investigate behavior of a composite quantum body in an external gravitational field in the framework of General Relativity [see, for a review, A. G. Lebed, Mod. Phys. Lett. A, 35, 2030010 (2020)]. As the simplest example, we have considered a hydrogen atom in a weak gravitational field. Our results are the following. The Einstein's Equivalence Principle survives for the most of macroscopic ensembles of the atoms, containing the stationary quantum states. On the other hand, we have demonstrated that this principle is sometimes broken. In particular, it is broken for the so-called Gravitational demons, which are the coherent macroscopic ensembles of two or more stationary quantum states in the hydrogen atoms. In the above cited paper we have considered the Gedanken experiment, where the gravitational field is suddenly switched on in a free from gravitation space. In the current paper we consider the much more realistic from experimental point of view Gedanken experiment and come to the same conclusion about violations of the Einstein's Equivalence Principle for the Gravitational demons. © 2023 Author(s).12 month embargo; first published 28 September 2023This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]
Violation of the Einstein's Equivalence Principle for a Composite Quantum Body
No full textRecently, we have started to investigate behavior of a composite quantum body
in an external gravitational field in the framework of General Relativity [see,
for a review, A. G. Lebed, Mod. Phys. Lett. A, {\bf 35}, 2030010 (2020)]. As
the simplest example, we have considered a hydrogen atom in a weak
gravitational field. Our results are the following. The Einstein's Equivalence
Principle survives for the most of macroscopic ensembles of the atoms,
containing the stationary quantum states. On the other hand, we have
demonstrated that this principle is sometimes broken. In particular, it is
broken for the so-called Gravitational demons, which are the coherent
macroscopic ensembles of two or more stationary quantum states in the hydrogen
atoms. In the above cited paper we have considered the Gedanken experiment,
where the gravitational field is suddenly switched on in a free from
gravitation space. In the current paper we consider the much more realistic
from experimental point of view Gedanken experiment and come to the same
conclusion about violations of the Einstein's Equivalence Principle for the
Gravitational demons.Comment: 4 page
Orbital effect for the Fulde-Ferrell-Larkin-Ovchinnikov phase in a quasi-two-dimensional superconductor in a parallel magnetic field
No full textWe theoretically study the orbital destructive effect against superconductivity in a parallel magnetic field in the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO or LOFF) phase at zero temperature in a quasi-two-dimensional (Q2D) conductor. We demonstrate that at zero temperature a special parameter, lambda = l(perpendicular to)(H)/d, is responsible for strength of the orbital effect, where l(perpendicular to)(H) is a typical "size" of the quasiclassical electron orbit in a magnetic field and d is the interplane distance. We discuss applications of our results to the existing experiments on the FFLO phase in the organic Q2D conductors kappa-(ET)(2)Cu(NCS)(2) and kappa-(ET)(2)Cu[N(CN)(2)]Cl.Authors retain "The right to use all or part of the Article, including the APS-prepared version without revision or modification, on the author(s)’ web home page or employer’s website and to make copies of all or part of the Article, including the APS-prepared version without revision or modification, for the author(s)’ and/or the employer’s use for educational or research purposes."This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]
About a question of Gateva-Ivanova and Cameron on square-free set-theoretic solutions of the Yang-Baxter equation
No full textIn this article, we introduce a new sequence (Formula presented.) to find a new estimation of the cardinality Nm of the minimal involutive square-free solution of level m. As an application, using the first values of (Formula presented.) we improve the estimations of Nm obtained by Gateva-Ivanova and Cameron and Lebed and Vendramin. Following the approach of the first part, in the last section we construct several new counterexamples to the Gateva-Ivanova’s Conjecture
Croce Rossa Italiana. Manuale di buone pratiche: esperienze da un Centro di Accoglienza per Richiedenti Asilo.
No full text152 pagin
On various types of nilpotency of the structure monoid and group of a set-theoretic solution of the Yang--Baxter equation
No full textGiven a finite bijective non-degenerate set-theoretic solution of the
Yang--Baxter equation we characterize when its structure monoid is
Malcev nilpotent. Applying this characterization to solutions coming from
racks, we rediscover some results obtained recently by Lebed and Mortier, and
by Lebed and Vendramin on the description of finite abelian racks and quandles.
We also investigate bijective non-degenerate multipermutation (not
necessarily finite) solutions and show, for example, that this property
is equivalent to the solution associated to the structure monoid
(respectively structure group ) being a multipermuation solution and
that is solvable of derived length not exceeding the
multipermutation level of enlarged by one, generalizing results of
Gateva-Ivanova and Cameron obtained in the involutive case. Moreover, we also
prove that if is finite and is nilpotent, then the torsion part
of the group is finite, it coincides with the commutator subgroup
of the additive structure of the skew left brace and is a
trivial left brace.Comment: 36 pages, some typos corrected, to appear in Journal of Pure and
Applied Algebra, postprint versio
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