748 research outputs found
From the Complete Yang Model to Snyder's Model, de Sitter Special Relativity and Their Duality
By means of Dirac procedure, we re-examine Yang's quantized space-time model,
its relation to Snyder's model, the de Sitter special relativity and their
UV-IR duality. Starting from a dimensionless dS_5-space in a 5+1-d Mink-space a
complete Yang model at both classical and quantum level can be presented and
there really exist Snyder's model, the dS special relativity and the duality.Comment: 7 papge
Newton-Hooke Limit of Beltrami-de Sitter Spacetime, Principles of Galilei-Hooke's Relativity and Postulate on Newton-Hooke Universal Time
Based on the Beltrami-de Sitter spacetime, we present the Newton-Hooke model
under the Newton-Hooke contraction of the spacetime with respect to the
transformation group, algebra and geometry. It is shown that in Newton-Hooke
space-time, there are inertial-type coordinate systems and inertial-type
observers, which move along straight lines with uniform velocity. And they are
invariant under the Newton-Hooke group. In order to determine uniquely the
Newton-Hooke limit, we propose the Galilei-Hooke's relativity principle as well
as the postulate on Newton-Hooke universal time. All results are readily
extended to the Newton-Hooke model as a contraction of Beltrami-anti-de Sitter
spacetime with negative cosmological constant.Comment: 25 pages, 3 figures; some misprints correcte
Intrinsic anomalous Hall effect in nickel: An GGA+U study
The electronic structure and intrinsic anomalous Hall conductivity of nickel
have been calculated based on the generalized gradient approximation (GGA) plus
on-site Coulomb interaction (GGA+U) scheme. It is found that the intrinsic
anomalous Hall conductivity () obtained from the GGA+U
calculations with eV and eV, is in nearly perfect agreement
with that measured recently at low temperatures while, in contrast, the
from the GGA calculations is about 100% larger than the
measured one. This indicates that, as for the other spin-orbit interaction
(SOI)-induced phenomena in 3 itinerant magnets such as the orbital magnetic
magnetization and magnetocrystalline anisotropy, the on-site electron-electron
correlation, though moderate only, should be taken into account properly in
order to get the correct anomalous Hall conductivity. The intrinsic
and the number of valence electrons () have also been
calculated as a function of the Fermi energy (). A sign change is
predicted at eV (), and this explain qualitatively
why the theoretical and experimental values for Fe and Co are
positive. It is also predicted that fcc NiCo(Fe,Cu) alloys with
being small, would also have the negative with the
magnitude being in the range of cm. The most
pronounced effect of including the on-site Coulomb interaction is that all the
-dominant bands are lowered in energy relative to the by about 0.3 eV,
and consequently, the small minority spin X hole pocket disappears. The
presence of the small X hole pocket in the GGA calculations is attributed
to be responsible for the large discrepancy in the between
theory and experiment.Comment: 7 pages, 3 figures; Accepted for publication in Physical Review
Three Kinds of Special Relativity via Inverse Wick Rotation
Since the special relativity can be viewed as the physics in an inverse Wick
rotation of 4-d Euclid space, which is at almost equal footing with the 4-d
Riemann/Lobachevski space, there should be important physics in the inverse
Wick rotation of 4-d Riemann/Lobachevski space. Thus, there are three kinds of
special relativity in de Sitter/Minkowski/anti-de Sitter space at almost equal
footing, respectively. There is an instanton tunnelling scenario in the
Riemann-de Sitter case that may explain why \La be positive and link with the
multiverse.Comment: 3 pages, no figures, to appear in Chin. Phys. Let
Snyder's Quantized Space-time and De Sitter Special Relativity
There is a one-to-one correspondence between Snyder's model in de Sitter
space of momenta and the \dS-invariant special relativity. This indicates that
physics at the Planck length and the scale should be
dual to each other and there is in-between gravity of local \dS-invariance
characterized by a dimensionless coupling constant .Comment: 8 page
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