4,599,287 research outputs found
Repulsive force in the field theory of gravitation
It is shown that the slowing down of the rate of time referencing to the
inertial time leads in the field theory of gravitation to arising of repulsive
forces which remove the cosmological singularity in the evolution of a
homogeneous and isotropic universe and stop the collapse of large masses.Comment: 22 pages, Plenary talk presented at Workshop on High Energy
Physics&Field Theory (Protvino, Russia, 2005
What is the true charge transfer gap in parent insulating cuprates?
A large body of experimental data point towards a charge transfer instability
of parent insulating cuprates to be their unique property. We argue that the
true charge transfer gap in these compounds is as small as 0.4-0.5\,eV rather
than 1.5-2.0\,eV as usually derived from the optical gap measurements. In fact
we deal with a competition of the conventional (3d) ground state and a
charge transfer (CT) state with formation of electron-hole dimers which evolves
under doping to an unconventional bosonic system. Our conjecture does provide
an unified standpoint on the main experimental findings for parent cuprates
including linear and nonlinear optical, Raman, photoemission, photoabsorption,
and transport properties anyhow related with the CT excitations. In addition we
suggest a scenario for the evolution of the CuO planes in the CT unstable
cuprates under a nonisovalent doping.Comment: 13 pages, 5 figures, submitted to PR
Normal state diamagnetism of charged bosons in cuprate superconductors
Normal state orbital diamagnetism of charged bosons quantitatively accounts
for recent high-resolution magnetometery results near and above the resistive
critical temperature Tc of superconducting cuprates. Our parameter-free
descriptions of normal state diamagnetism, Tc, upper critical fields and
specific heat anomalies unambiguously support the 3D Bose-Einstein condensation
at Tc of preformed real-space pairs with zero off-diagonal order parameter
above Tc, at variance with phase fluctuation (or vortex) scenarios of the
"normal" state of cuprates.Comment: 10 pages, 4 figure
Sub-wavelength imaging: Resolution enhancement using metal wire gratings
An experimental evidence of subwavelength imaging with a "lens", which is a
uniaxial negative permittivity wire medium slab, is reported. The slab is
formed by gratings of long thin parallel conducting cylinders. Taking into
account the anisotropy and spatial dispersion in the wire medium we
theoretically show that there are no usual plasmons that could be exited on
surfaces of such a slab, and there is no resonant enhancement of evanescent
fields in the slab. The experimentally observed clear improvement of the
resolution in the presence of the slab is explained as filtering out the
harmonics with small wavenumbers. In other words, the wire gratings (the wire
medium) suppress strong traveling-mode components increasing the role of
evanescent waves in the image formation. This effect can be used in near-field
imaging and detection applications.Comment: 12 pages, 6 figure
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