222 research outputs found
Possible quantum kinematics. II. Non-minimal case
The quantum analogs of the N-dimensional Cayley-Klein spaces with different
combinations of quantum and Cayley-Klein structures are described for
non-minimal multipliers, which include the first and the second powers of
contraction parameters in the transformation of deformation parameter. The
noncommutative analogs of (N-1)-dimensional constant curvature spaces are
introduced. Part of these spaces for N=5 are interpreted as the noncommutative
analogs of (1+3) space-time models. As a result the wide variety of the quantum
deformations of realistic kinematics are suggested.Comment: 13 pages, no figure
The R.I. Pimenov unified gravitation and electromagnetism field theory as semi-Riemannian geometry
More then forty years ago R.I. Pimenov introduced a new geometry --
semi-Riemannian one -- as a set of geometrical objects consistent with a
fibering He suggested the heuristic principle according to
which the physically different quantities (meter, second, coulomb etc.) are
geometrically modelled as space coordinates that are not superposed by
automorphisms. As there is only one type of coordinates in Riemannian geometry
and only three types of coordinates in pseudo-Riemannian one, a multiple
fibered semi-Riemannian geometry is the most appropriate one for the treatment
of more then three different physical quantities as unified geometrical field
theory.
Semi-Euclidean geometry with 1-dimensional fiber and
4-dimensional Minkowski space-time as a base is naturally interpreted as
classical electrodynamics. Semi-Riemannian geometry with the
general relativity pseudo-Riemannian space-time and 1-dimensional
fiber responsible for the electromagnetism, provides the unified field
theory of gravitation and electromagnetism. Unlike Kaluza-Klein theories, where
the 5-th coordinate appears in nondegenerate Riemannian or pseudo-Riemannian
geometry, the theory based on semi-Riemannian geometry is free from defects of
the former. In particular, scalar field does not arise.
PACS: 04.50.Cd, 02.40.-k, 11.10.KkComment: 16 pages, 2 figures. Submited to Physics of Atomic Nucle
On the relation of Voevodsky's algebraic cobordism to Quillen's K-theory
Quillen's algebraic K-theory is reconstructed via Voevodsky's algebraic
cobordism. More precisely, for a ground field k the algebraic cobordism
P^1-spectrum MGL of Voevodsky is considered as a commutative P^1-ring spectrum.
There is a unique ring morphism MGL^{2*,*}(k)--> Z which sends the class
[X]_{MGL} of a smooth projective k-variety X to the Euler characteristic of the
structure sheaf of X. Our main result states that there is a canonical grade
preserving isomorphism of ring cohomology theories MGL^{*,*}(X,U)
\tensor_{MGL^{2*,*}(k)} Z --> K^{TT}_{- *}(X,U) = K'_{- *}(X-U)} on the
category of smooth k-varieties, where K^{TT}_* is Thomason-Trobaugh K-theory
and K'_* is Quillen's K'-theory. In particular, the left hand side is a ring
cohomology theory. Moreover both theories are oriented and the isomorphism
above respects the orientations. The result is an algebraic version of a
theorem due to Conner and Floyd. That theorem reconstructs complex K-theory via
complex cobordism.Comment: LaTeX, 18 pages, uses XY-pi
Electric-dipole active two-magnon excitation in {\textit{ab}} spiral spin phase of a ferroelectric magnet GdTbMnO
A broad continuum-like spin excitation (1--10 meV) with a peak structure
around 2.4 meV has been observed in the ferroelectric spiral spin phase of
GdTbMnO by using terahertz (THz) time-domain spectroscopy.
Based on a complete set of light-polarization measurements, we identify the
spin excitation active for the light vector only along the a-axis, which
grows in intensity with lowering temperature even from above the magnetic
ordering temperature but disappears upon the transition to the -type
antiferromagnetic phase. Such an electric-dipole active spin excitation as
observed at THz frequencies can be ascribed to the two-magnon excitation in
terms of the unique polarization selection rule in a variety of the
magnetically ordered phases.Comment: 11 pages including 3 figure
Comparison of the effect of superplasticizing admixtures on the processes of cement hydration during mechanochemical activation
© 2016 Ruslan Ibragimov, Sergey Pimenov, Ilham Kiyamov, Ramil Mingazov, Laysan Kiyamova.The results of the study of the influence of two different super-plasticizers on the peculiarities of the process of hydration during mechanochemical activation (MCA) of a binder are given. The influence of SAS admixtures during the MCA of a binder on the kinetics of heat release and the alkalinity of the liquid phase of cement slurry is revealed. Technological properties of concrete mixture and physicomechanical properties of heavy-weight concrete, obtained by the MCA of a binder with the SAS admixtures, were studied. Dependencies of the influence of SAS on the processes and the nature of cement hydration were established, as well as on granulometric and phase composition of hydrated new formations. It was established that the application of SAS admixtures at the MCA of a binder makes it possible to substantially increase the efficiency of cement dispergation, which manifests itself in the decrease of grain sizes and the increase in specific surface area. The MCA of a binder with SAS admixtures makes it possible to obtain homogeneous cement suspension with the uniform distribution of water in the volume of cement, which positively affects physicomechanical properties and the quality of the obtained concrete. The application of SAS admixtures at the MCA of a binder results in the reduction of induction period of hydration by 2-5 hours, and also in the acceleration of crystallization period by 5-7 hours faster than in the reference compositions. MCA of cement suspension with SAS admixtures leads to the increase in the density of concrete mixture and a substantial increase in the strength limit of heavy-weight concrete at compression during all periods of hardening. With the MCA of a binder with SAS, an increase in the amount of crystalline phase by 10-12 % is observed in the first twenty-four hours of hardening, which confirms the conclusion about acceleration of cement hydration with the joint use of SAS and MCA. According to the results of a comprehensive study we received new data of the influence of super-plasticizing admixtures of different chemical bases on the peculiarities of the processes of hydration of a binder during MCA. The obtained data can be used for selection of superplasticizing admixtures in the production of the ferroconcrete products, obtained with the MCA of a binder, as well as in the technology of construction of buildings made of monolithic reinforced concrete
Higgsless Electroweak Model and Contraction of Gauge Group
A modified formulation of the Electroweak Model with 3-dimensional spherical
geometry in the target space is suggested. The {\it free} Lagrangian in the
spherical field space along with the standard gauge field Lagrangian form the
full Higgsless Lagrangian of the model, whose second order terms reproduce the
same experimentally verified fields with the same masses as the Standard
Electroweak Model. The vector bosons masses are automatically generated, so
there is no need in special mechanism of spontaneous symmetry breaking.
The limiting case of the modified Higgsless Electroweak Model, which
corresponds to the contracted gauge group is discussed.
Within framework of the limit model Z-boson, electromagnetic and electron
fields are interpreted as an external ones with respect to W-bosons and
neutrino fields. The W-bosons and neutrino fields do not effect on these
external fields. The masses of all particles remain the same, but the field
interactions in contracted model are more simple as compared with the standard
Electroweak Model due to nullification of some terms.Comment: Talk at the International Workshop "`Supersymmetries and Quantum
Symmetries"' (SQS-09), Dubna, Russia, July 29 -- August 3, 2009, 11
Structural and magnetic dimers in the spin-gapped system CuTe2O5
We investigated the magnetic properties of the system CuTe2O5 by
susceptibility and electron spin resonance measurements. The anisotropy of the
effective g-factors and the ESR linewidth indicates that the anticipated
structural dimer does not correspond to the singlet-forming magnetic dimer.
Moreover, the spin susceptibility of CuTe2O5 can only be described by taking
into account interdimer interactions of the same order of magnitude than the
intradimer coupling. Analyzing the exchange couplings in the system we identify
the strongest magnetic coupling between two Cu ions to be mediated by
super-super exchange interaction via a bridging Te ligand, while the
superexchange coupling between the Cu ions of the structural dimer only results
in the second strongest coupling
Theory of magnetoelectric resonance in two-dimensional antiferromagnet via spin-dependent metal-ligand hybridization mechanism
We investigate magnetic excitations in an Heisenberg model
representing two-dimensional antiferromagnet . In
terahertz absorption experiment of the compound, Goldstone mode as well as
novel magnetic excitations, conventional magnetic resonance at 2 meV and both
electric- and magnetic-active excitation at 4 meV, have been observed. By
introducing a hard uniaxial anisotropy term , three modes can
be explained naturally. We also indicate that, via the spin-dependent
metal-ligand hybridization mechanism, the 4 meV excitation is an
electric-active mode through the coupling between spin and electric-dipole.
Moreover, at 4 meV excitation, an interference between magnetic and electric
responses emerges as a cross correlated effect. Such cross correlation effects
explain the non-reciprocal linear directional dichroism observed in .Comment: 5 pages, 3 figure
Electric-field control of spin waves at room temperature in multiferroic BiFeO3
To face the challenges lying beyond current CMOS-based technology, new
paradigms for information processing are required. Magnonics proposes to use
spin waves to carry and process information, in analogy with photonics that
relies on light waves, with several advantageous features such as potential
operation in the THz range and excellent coupling to spintronics. Several
magnonic analog and digital logic devices have been proposed, and some
demonstrated. Just as for spintronics, a key issue for magnonics is the large
power required to control/write information (conventionally achieved through
magnetic fields applied by strip lines, or by spin transfer from large
spin-polarized currents). Here we show that in BiFeO3, a room-temperature
magnetoelectric material, the spin wave frequency (>600 GHz) can be tuned
electrically by over 30%, in a non-volatile way and with virtually no power
dissipation. Theoretical calculations indicate that this effect originates from
a linear magnetoelectric effect related to spin-orbit coupling induced by the
applied electric field. We argue that these properties make BiFeO3 a promising
medium for spin wave generation, conversion and control in future magnonics
architectures.Comment: 3 figure
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