7,946 research outputs found
The effect of electron surface scattering on fine metal particle electromagnetic radiation absorption
The magnetic dipole absorption cross section of a spherically shaped metal
particle was calculated in terms of kinetic approach. The particle considered
was placed in the field of a plane electromagnetic wave. The model of boundary
conditions was investigated taking into account the dependence of the
reflectivity coefficient both on the surface roughness parameter and on the
electron incidence angle. The results obtained were compared with theoretical
computation results for a model of combined diffusion-specular boundary
conditions of Fuchs.Comment: 9 pages, 5 figure
Determinant Line Bundles and Topological Invariants of Hyperbolic Geometry - Expository Remarks
We give some remarks on twisted determinant line bundles and Chern-Simons
topological invariants associated with real hyperbolic manifolds. Index of a
twisted Dirac operator is derived. We discuss briefly application of obtained
results in topological quantum field theory.Comment: 10 pages. To appear in G@C, special issue devoted to QG, Unified
Models and Strings, to mark 100th Anniversary of Tomsk State Pedagogical
University. Editor - S.D. Odintso
Long-distance entanglement and quantum teleportation in XX spin chains
Isotropic XX models of one-dimensional spin-1/2 chains are investigated with
the aim to elucidate the formal structure and the physical properties that
allow these systems to act as channels for long-distance, high-fidelity quantum
teleportation. We introduce two types of models: I) open, dimerized XX chains,
and II) open XX chains with small end bonds. For both models we obtain the
exact expressions for the end-to-end correlations and the scaling of the energy
gap with the length of the chain. We determine the end-to-end concurrence and
show that model I) supports true long-distance entanglement at zero
temperature, while model II) supports {\it ``quasi long-distance''}
entanglement that slowly falls off with the size of the chain. Due to the
different scalings of the gaps, respectively exponential for model I) and
algebraic in model II), we demonstrate that the latter allows for efficient
qubit teleportation with high fidelity in sufficiently long chains even at
moderately low temperatures.Comment: 9 pages, 6 figure
One-dimensional structures behind twisted and untwisted superYang-Mills theory
We give a one-dimensional interpretation of the four-dimensional twisted N=1
superYang-Mills theory on a Kaehler manifold by performing an appropriate
dimensional reduction. We prove the existence of a 6-generator superalgebra,
which does not possess any invariant Lagrangian but contains two different
subalgebras that determine the twisted and untwisted formulations of the N=1
superYang-Mills theory.Comment: 12 pages. Final version to appear in Lett. Math. Phys. with improved
notation and misprints correcte
A short survey on nonlinear models of the classic Costas loop: rigorous derivation and limitations of the classic analysis
Rigorous nonlinear analysis of the physical model of Costas loop --- a
classic phase-locked loop (PLL) based circuit for carrier recovery, is a
challenging task. Thus for its analysis, simplified mathematical models and
numerical simulation are widely used. In this work a short survey on nonlinear
models of the BPSK Costas loop, used for pre-design and post-design analysis,
is presented. Their rigorous derivation and limitations of classic analysis are
discussed. It is shown that the use of simplified mathematical models, and the
application of non rigorous methods of analysis (e.g., simulation and
linearization) may lead to wrong conclusions concerning the performance of the
Costas loop physical model.Comment: Accepted to American Control Conference (ACC) 2015 (Chicago, USA
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