4,796 research outputs found
Surface EM waves on 1D Photonic Crystals
We study surface states of 1D photonic crystals using a semiclassical coupled
wave theory. Both TE and TM modes are treated. We derive analytic
approximations that clarify the systematics of the dispersion relations, and
the roles of the various parameters defining the crystal.Comment: 7 pages, 8 figure
Symmetric achromatic low-beta collider interaction region design concept
We present a new symmetry-based concept for an achromatic low-beta collider
interaction region design. A specially-designed symmetric Chromaticity
Compensation Block (CCB) induces an angle spread in the passing beam such that
it cancels the chromatic kick of the final focusing quadrupoles. Two such CCBs
placed symmetrically around an interaction point allow simultaneous
compensation of the 1st-order chromaticities and chromatic beam smear at the IP
without inducing significant 2nd-order aberrations to the particle trajectory.
We first develop an analytic description of this approach and explicitly
formulate 2nd-order aberration compensation conditions at the interaction
point. The concept is next applied to develop an interaction region design for
the ion collider ring of an electron-ion collider. We numerically evaluate
performance of the design in terms of momentum acceptance and dynamic aperture.
The advantages of the new concept are illustrated by comparing it to the
conventional distributed-sextupole chromaticity compensation scheme.Comment: 12 pages, 17 figures, to be submitted to Phys. Rev. ST Accel. Beam
Universal Mandelbrot Set as a Model of Phase Transition Theory
The study of Mandelbrot Sets (MS) is a promising new approach to the phase
transition theory. We suggest two improvements which drastically simplify the
construction of MS. They could be used to modify the existing computer programs
so that they start building MS properly not only for the simplest families.
This allows us to add one more parameter to the base function of MS and
demonstrate that this is not enough to make the phase diagram connectedComment: 5 pages, 3 figure
Interplay between lattice, orbital, and magnetic degrees of freedom in the chain-polymer Cu(II) breathing crystals
The chain-polymer Cu(II) breathing crystals C21H19CuF12N4O6 were studied
using the x-ray diffraction and ab initio band structure calculations. We show
that the crystal structure modification at T=146 K, associated with the spin
crossover transition, induces the changes of the orbital order in half of the
Cu sites. This in turn results in the switch of the magnetic interaction sign
in accordance with the Goodenough-Kanamori-Andersen theory of the coupling
between the orbital and spin degrees of freedom.Comment: 6 pages, 7 figure
A-infinity structure on simplicial complexes
A discrete (finite-difference) analogue of differential forms is considered,
defined on simplicial complexes, including triangulations of continuous
manifolds. Various operations are explicitly defined on these forms, including
exterior derivative and exterior product. The latter one is non-associative.
Instead, as anticipated, it is a part of non-trivial A-infinity structure,
involving a chain of poly-linear operations, constrained by nilpotency
relation: (d + \wedge + m + ...)^n = 0 with n=2.Comment: final version. 29 page
Effect of Anode Dielectric Coating on Hall Thruster Operation
An interesting phenomenon observed in the near-anode region of a Hall
thruster is that the anode fall changes from positive to negative upon removal
of the dielectric coating, which is produced on the anode surface during the
normal course of Hall thruster operation. The anode fall might affect the
thruster lifetime and acceleration efficiency. The effect of the anode coating
on the anode fall is studied experimentally using both biased and emissive
probes. Measurements of discharge current oscillations indicate that thruster
operation is more stable with the coated anode
On Lie-algebraic solutions of the type IIB matrix model
A systematic search for Lie algebra solutions of the type IIB matrix model is
performed. Our survey is based on the classification of all Lie algebras for
dimensions up to five and of all nilpotent Lie algebras of dimension six. It is
shown that Lie-type solutions of the equations of motion of the type IIB matrix
model exist and they correspond to certain nilpotent and solvable Lie algebras.
Their representation in terms of Hermitian matrices is discussed in detail.
These algebras give rise to certain non-commutative spaces for which the
corresponding star-products are provided. Finally the issue of constructing
quantized compact nilmanifolds and solvmanifolds based on the above algebras is
addressed.Comment: 22 page
A weak-coupling superconductivity in the electron doped NaFeCoAs is revealed by ARPES
We report a systematic study on the electronic structure and superconducting
(SC) gaps in electron doped NaFeCoAs superconductor using
angle-resolved photoemission spectroscopy. Hole-like Fermi sheets are at the
zone center and electron-like Fermi sheets are at the zone corner, and are
mainly contributed by and orbital characters. Our results reveal a
in the range of 1.8-2.1, suggesting a weak-coupling
superconductivity in these compounds. Gap closing above the transition
temperature () shows the absence of pseudogaps. Gap evolution with
temperature follow the BCS gap equation near the , , and high
symmetry points. Furthermore, an almost isotropic superconductivity along
direction in the momentum space is observed by varying the excitation energies.Comment: 6 pages, 5 figures, Accepted by Phy.Rev.
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