969 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
Electron mass operator in a strong magnetic field
The electron mass operator in a strong magnetic field is calculated by
summation of the leading log contributions in all orders of the perturbation
theory. An influence of the strong field on the virtual photon polarization
operator is taken into account. The contribution of higher Landau levels of
virtual electrons, along with the ground Landau level, is shown to be essential
in the leading log approximation.Comment: 7 pages, LATEX, 1 PS figure, submitted to Modern Physics Letters
Self-Stimulated Undulator Radiation and its Possible Applications
We investigated the phenomena of self-stimulation of incoherent emission from
an undulator installed in the linear accelerator or quasi-isochronous storage
ring. We discuss possible applications of these phenomena for the beam physics
also.Comment: 14 pages, 4 figure
Dirac fermions on a disclinated flexible surface
A self-consisting gauge-theory approach to describe Dirac fermions on
flexible surfaces with a disclination is formulated. The elastic surfaces are
considered as embeddings into R^3 and a disclination is incorporated through a
topologically nontrivial gauge field of the local SO(3) group which generates
the metric with conical singularity. A smoothing of the conical singularity on
flexible surfaces is naturally accounted for by regarding the upper half of
two-sheet hyperboloid as an elasticity-induced embedding. The availability of
the zero-mode solution to the Dirac equation is analyzed.Comment: 6 page
Approximation by continuous functions and its applications
We prove that for every normal topological space and any function there is a continuous function such that
for all .
As an application of this result we prove the following statements to types
of tightness in a space of all quasicontinuous real-valued
functions with the topology of pointwise convergence: the countability
of tightness (fan-tightness, strong fan-tightness) at a point of space
implies the countability of tightness (fan-tightness,
strong fan-tightness) of space of all quasicontinuous functions from
into any non-one-point metrizable space . This result is the answer to
the open question in the class of metrizable spaces.Comment: 15 page
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