706 research outputs found
Mass Transfer Mechanism in Real Crystals by Pulsed Laser Irradiation
The dynamic processes in the surface layers of metals subjected activity of a
pulsing laser irradiation, which destroyed not the crystalline structure in
details surveyed. The procedure of calculation of a dislocation density
generated in bulk of metal during the relaxation processes and at repeated
pulse laser action is presented. The results of evaluations coincide with high
accuracy with transmission electron microscopy dates. The
dislocation-interstitial mechanism of laser-stimulated mass-transfer in real
crystals is presented on the basis of the ideas of the interaction of structure
defects in dynamically deforming medium. The good compliance of theoretical and
experimental results approves a defining role of the presented mechanism of
mass transfer at pulse laser action on metals. The possible implementation this
dislocation-interstitial mechanism of mass transfer in metals to other cases of
pulsing influences is justifiedComment: 10 pages, 2 figures, Late
Radial Velocity along the Voyager 1 Trajectory: The Effect of Solar Cycle
As Voyager 1 and Voyager 2 are approaching the heliopause (HP)—the boundary between the solar wind (SW) and the local interstellar medium (LISM)—we expect new, unknown features of the heliospheric interface to be revealed. A seeming puzzle reported recently by Krimigis et al. concerns the unusually low, even negative, radial velocity components derived from the energetic ion distribution. Steady-state plasma models of the inner heliosheath (IHS) show that the radial velocity should not be equal to zero even at the surface of the HP. Here we demonstrate that the velocity distributions observed by Voyager 1 are consistent with time-dependent simulations of the SW-LISM interaction. In this Letter, we analyze the results from a numerical model of the large-scale heliosphere that includes solar cycle effects. Our simulations show that prolonged periods of low to negative radial velocity can exist in the IHS at substantial distances from the HP. It is also shown that Voyager 1 was more likely to observe such regions than Voyager 2
Quantum Electrodynamics at Extremely Small Distances
The asymptotics of the Gell-Mann - Low function in QED can be determined
exactly, \beta(g)= g at g\to\infty, where g=e^2 is the running fine structure
constant. It solves the problem of pure QED at small distances L and gives the
behavior g\sim L^{-2}.Comment: Latex, 6 pages, 1 figure include
Bound electron states in the monolayer graphene with short-range impurities
Bound electron states in impure graphene are considered. Short-range
perturbations for defect and impurities of the types "local chemical potential"
and "local gap" are taken into account.Comment: 3 figure
Rim curvature anomaly in thin conical sheets revisited
This paper revisits one of the puzzling behaviors in a developable cone
(d-cone), the shape obtained by pushing a thin sheet into a circular container
of radius by a distance [E. Cerda, S. Chaieb, F. Melo, and L.
Mahadevan, {\sl Nature} {\bf 401}, 46 (1999)]. The mean curvature was reported
to vanish at the rim where the d-cone is supported [T. Liang and T. A. Witten,
{\sl Phys. Rev. E} {\bf 73}, 046604 (2006)]. We investigate the ratio of the
two principal curvatures versus sheet thickness over a wider dynamic range
than was used previously, holding and fixed. Instead of tending
towards 1 as suggested by previous work, the ratio scales as .
Thus the mean curvature does not vanish for very thin sheets as previously
claimed. Moreover, we find that the normalized rim profile of radial curvature
in a d-cone is identical to that in a "c-cone" which is made by pushing a
regular cone into a circular container. In both c-cones and d-cones, the ratio
of the principal curvatures at the rim scales as ,
where is the pushing force and is the Young's modulus. Scaling
arguments and analytical solutions confirm the numerical results.Comment: 25 pages, 12 figures. Added references. Corrected typos. Results
unchange
Magnetoresistance of Highly Correlated Electron Liquid
The behavior in magnetic fields of a highly correlated electron liquid
approaching the fermion condensation quantum phase transition from the
disordered phase is considered. We show that at sufficiently high temperatures
the effective mass starts to depend on , . This dependence of the effective mass at elevated
temperatures leads to the non-Fermi liquid behavior of the resistivity,
and at higher temperatures . The
application of a magnetic field restores the common behavior of the
resistivity. The effective mass depends on the magnetic field, , being approximately independent of the temperature at . At , the dependence of the
effective mass is re-established. We demonstrate that this phase diagram
has a strong impact on the magnetoresistance (MR) of the highly correlated
electron liquid. The MR as a function of the temperature exhibits a transition
from the negative values of MR at to the positive values at . Thus, at , MR as a function of the temperature
possesses a node at .Comment: 7 pages, revtex, no figure
Dissymmetrical tunnelling in heavy fermion metals
A tunnelling conductivity between a heavy fermion metal and a simple metallic
point is considered. We show that at low temperatures this conductivity can be
noticeably dissymmetrical with respect to the change of voltage bias. The
dissymmetry can be observed in experiments on the heavy fermion metals whose
electronic system has undergone the fermion condensation quantum phase
transition.Comment: 7 pages, Revte
Curvature condensation and bifurcation in an elastic shell
We study the formation and evolution of localized geometrical defects in an
indented cylindrical elastic shell using a combination of experiment and
numerical simulation. We find that as a symmetric localized indentation on a
semi-cylindrical shell increases, there is a transition from a global mode of
deformation to a localized one which leads to the condensation of curvature
along a symmetric parabolic crease. This process introduces a soft mode in the
system, converting a load-bearing structure into a hinged, kinematic mechanism.
Further indentation leads to twinning wherein the parabolic crease bifurcates
into two creases that move apart on either side of the line of symmetry. A
qualitative theory captures the main features of the phenomena and leads to
sharper questions about the nucleation of these defects.Comment: 4 pages, 5 figures, submitted to Physical Review Letter
Specifics of impurity effects in ferropnictide superconductors
Effects of impurities and disorder on quasiparticle spectrum in
superconducting iron pnictides are considered. Possibility for occurrence of
localized energy levels due to impurities within the superconducting gap and
the related modification of band structure and of superconducting order
parameter are discussed. The evolution of superconducting state with impurity
doping is traced.Comment: 9 pages, 8 figure
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