1,301 research outputs found
Low-temperature thermal conductivity in polycrystalline graphene
The low-temperature thermal conductivity in polycrystalline graphene is
theoretically studied. The contributions from three branches of acoustic
phonons are calculated by taking into account scattering on sample borders,
point defects and grain boundaries. Phonon scattering due to sample borders and
grain boundaries is shown to result in a -behaviour in the thermal
conductivity where varies between 1 and 2. This behaviour is found to
be more pronounced for nanosized grain boundaries.
PACS: 65.80.Ck, 81.05.ue, 73.43.C
Ultrahard spectra of PeV neutrinos from supernovae in compact star clusters
Starburst regions with multiple powerful winds of young massive stars and
supernova remnants are favorable sites for high-energy cosmic ray acceleration.
A supernova shock colliding with a fast wind from a compact cluster of young
stars allows the acceleration of protons to energies well above the standard
limits of diffusive shock acceleration in an isolated SN. The proton spectrum
in such a wind-supernova PeV accelerator is hard with a large flux in the
high-energy-end of the spectrum producing copious gamma-rays and neutrinos in
inelastic nuclear collisions. We argue that SN shocks in the Westerlund 1
cluster in the Milky Way may accelerate protons to about 40 PeV. Once
accelerated, these CRs will diffuse into surrounding dense clouds and produce
neutrinos with fluxes sufficient to explain a fraction of the events detected
by IceCube Observatory from the inner Galaxy.Comment: 10 pages, 7 figures, MNRAS v.453, p.113-121, 201
Non-Degenerate Ultrametric Diffusion
General non-degenerate p-adic operators of ultrametric diffusion are
introduced. Bases of eigenvectors for the introduced operators are constructed
and the corresponding eigenvalues are computed. Properties of the corresponding
dynamics (i.e. of the ultrametric diffusion) are investigated.Comment: 19 pages, 3 figure
Full light absorption in single arrays of spherical nanoparticles
In this paper we show that arrays of core-shell nanoparticles function as
effective thin absorbers of light. In contrast to known metamaterial absorbers,
the introduced absorbers are formed by single planar arrays of spherical
inclusions and enable full absorption of light incident on either or both sides
of the array. We demonstrate possibilities for realizing different kinds of
symmetric absorbers, including resonant, ultra-broadband, angularly selective,
and all-angle absorbers. The physical principle behind these designs is
explained considering balanced electric and magnetic responses of unit cells.
Photovoltaic devices and thermal emitters are the two most important potential
applications of the proposed designs.Comment: (e.g.: 18 pages, 5 figures
Disclination vortices in elastic media
The vortex-like solutions are studied in the framework of the gauge model of
disclinations in elastic continuum. A complete set of model equations with
disclination driven dislocations taken into account is considered. Within the
linear approximation an exact solution for a low-angle wedge disclination is
found to be independent from the coupling constants of the theory. As a result,
no additional dimensional characteristics (like the core radius of the defect)
are involved. The situation changes drastically for 2\pi vortices where two
characteristic lengths, l_\phi and l_W, become of importance. The asymptotical
behaviour of the solutions for both singular and nonsingular 2\pi vortices is
studied. Forces between pairs of vortices are calculated.Comment: 13 pages, published versio
Global phase synchronization in an array of time-delay systems
We report the identification of global phase synchronization (GPS) in a
linear array of unidirectionally coupled Mackey-Glass time-delay systems
exhibiting highly non-phase-coherent chaotic attractors with complex
topological structure. In particular, we show that the dynamical organization
of all the coupled time-delay systems in the array to form GPS is achieved by
sequential synchronization as a function of the coupling strength. Further, the
asynchronous ones in the array with respect to the main sequentially
synchronized cluster organize themselves to form clusters before they achieve
synchronization with the main cluster. We have confirmed these results by
estimating instantaneous phases including phase difference, average phase,
average frequency, frequency ratio and their differences from suitably
transformed phase coherent attractors after using a nonlinear transformation of
the original non-phase-coherent attractors. The results are further
corroborated using two other independent approaches based on recurrence
analysis and the concept of localized sets from the original non-phase-coherent
attractors directly without explicitly introducing the measure of phase.Comment: 11 pages, 13 figures, Appear in Physical Review
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