3,456 research outputs found
"Spread" restricted Young diagrams from a 2D WZNW dynamical quantum group
The Fock representation of the Q-operator algebra for the diagonal WZNW model
on SU(n) at level k, where Q is the matrix of the 2D WZNW "zero modes"
generating certain dynamical quantum group, is finite dimensional and has a
natural basis labeled by su(n) Young diagrams Y of "spread" not exceeding h :=
k+n (spr (Y) = #(columns) + #(rows))Comment: 10 pages, 8 figures, submitted to the Proceedings of the 11th
International Workshop "Lie Theory and Its Applications in Physics" (Varna,
Bulgaria, 15-21 June 2015); v.2 - amended Introduction, figures and list of
reference
New Test of Supernova Electron Neutrino Emission using Sudbury Neutrino Observatory Sensitivity to the Diffuse Supernova Neutrino Background
Supernovae are rare nearby, but they are not rare in the Universe, and all
past core-collapse supernovae contributed to the Diffuse Supernova Neutrino
Background (DSNB), for which the near-term detection prospects are very good.
The Super-Kamiokande limit on the DSNB electron {\it antineutrino} flux,
cm s, is just above the
range of recent theoretical predictions based on the measured star formation
rate history. We show that the Sudbury Neutrino Observatory should be able to
test the corresponding DSNB electron {\it neutrino} flux with a sensitivity as
low as cm s,
improving the existing Mont Blanc limit by about three orders of magnitude.
While conventional supernova models predict comparable electron neutrino and
antineutrino fluxes, it is often considered that the first (and
forward-directed) SN 1987A event in the Kamiokande-II detector should be
attributed to electron-neutrino scattering with an electron, which would
require a substantially enhanced electron neutrino flux. We show that with the
required enhancements in either the burst or thermal phase fluxes, the
DSNB electron neutrino flux would generally be detectable in the Sudbury
Neutrino Observatory. A direct experimental test could then resolve one of the
enduring mysteries of SN 1987A: whether the first Kamiokande-II event reveals a
serious misunderstanding of supernova physics, or was simply an unlikely
statistical fluctuation. Thus the electron neutrino sensitivity of the Sudbury
Neutrino Observatory is an important complement to the electron antineutrino
sensitivity of Super-Kamiokande in the quest to understand the DSNB.Comment: 10 pages, 3 figure
Nonmonotonic magnetoresistance of a two-dimensional viscous electron-hole fluid in a confined geometry
Ultra-pure conductors may exhibit hydrodynamic transport where the collective
motion of charge carriers resembles the flow of a viscous fluid. In a confined
geometry (e.g., in ultra-high quality nanostructures) the electronic fluid
assumes a Poiseuille-like flow. Applying an external magnetic field tends to
diminish viscous effects leading to large negative magnetoresistance. In
two-component systems near charge neutrality the hydrodynamic flow of charge
carriers is strongly affected by the mutual friction between the two
constituents. At low fields, the magnetoresistance is negative, however at high
fields the interplay between electron-hole scattering, recombination, and
viscosity results in a dramatic change of the flow profile: the
magnetoresistance changes its sign and eventually becomes linear in very high
fields. This novel non-monotonic magnetoresistance can be used as a fingerprint
to detect viscous flow in two-component conducting systems.Comment: 10 pages, 8 figure
Counterflows in viscous electron-hole fluid
In ultra-pure conductors, collective motion of charge carriers at relatively
high temperatures may become hydrodynamic such that electronic transport may be
described similarly to a viscous flow. In confined geometries (e.g., in
ultra-high quality nanostructures), the resulting flow is Poiseuille-like. When
subjected to a strong external magnetic field, the electric current in
semimetals is pushed out of the bulk of the sample towards the edges. Moreover,
we show that the interplay between viscosity and fast recombination leads to
the appearance of counterflows. The edge currents possess a non-trivial spatial
profile and consist of two stripe-like regions: the outer stripe carrying most
of the current in the direction of the external electric field and the inner
stripe with the counterflow.Comment: 10 pages, 5 figure
Soliton Solutions with Real Poles in the Alekseev formulation of the Inverse-Scattering method
A new approach to the inverse-scattering technique of Alekseev is presented
which permits real-pole soliton solutions of the Ernst equations to be
considered. This is achieved by adopting distinct real poles in the scattering
matrix and its inverse. For the case in which the electromagnetic field
vanishes, some explicit solutions are given using a Minkowski seed metric. The
relation with the corresponding soliton solutions that can be constructed using
the Belinskii-Zakharov inverse-scattering technique is determined.Comment: 8 pages, LaTe
Physical phase space of lattice Yang-Mills theory and the moduli space of flat connections on a Riemann surface
It is shown that the physical phase space of \g-deformed Hamiltonian
lattice Yang-Mills theory, which was recently proposed in refs.[1,2], coincides
as a Poisson manifold with the moduli space of flat connections on a Riemann
surface with handles and therefore with the physical phase space of
the corresponding -dimensional Chern-Simons model, where and are
correspondingly a total number of links and vertices of the lattice. The
deformation parameter \g is identified with and is an
integer entering the Chern-Simons action.Comment: 12 pages, latex, no figure
The extensions of gravitational soliton solutions with real poles
We analyse vacuum gravitational "soliton" solutions with real poles in the
cosmological context. It is well known that these solutions contain
singularities on certain null hypersurfaces. Using a Kasner seed solution, we
demonstrate that these may contain thin sheets of null matter or may be simple
coordinate singularities, and we describe a number of possible extensions
through them.Comment: 14 pages, LaTeX, 6 figures included using graphicx; to appear in Gen.
Rel. Gra
Tentative Detection of the Nitrosylium Ion in Space
We report the tentative detection in space of the nitrosylium ion, NO.
The observations were performed towards the cold dense core Barnard 1-b. The
identification of the NO =2--1 line is supported by new laboratory
measurements of NO rotational lines up to the =8--7 transition
(953207.189\,MHz), which leads to an improved set of molecular constants: \,MHz, \,kHz, and \,MHz. The profile of the feature assigned to NO exhibits two
velocity components at 6.5 and 7.5 km s, with column densities of and cm, respectively. New
observations of NO and HNO, also reported here, allow to estimate the following
abundance ratios: (NO)/(NO), and
(HNO)/(NO). This latter value provides important constraints
on the formation and destruction processes of HNO. The chemistry of NO and
other related nitrogen-bearing species is investigated by the means of a
time-dependent gas phase model which includes an updated chemical network
according to recent experimental studies. The predicted abundance for NO
and NO is found to be consistent with the observations. However, that of HNO
relative to NO is too high. No satisfactory chemical paths have been found to
explain the observed low abundance of HNO. HSCN and HNCS are also reported here
with an abundance ratio of . Finally, we have searched for NNO,
NO, HNNO, and NNOH, but only upper limits have been obtained for
their column density, except for the latter for which we report a tentative
3- detection.Comment: To appear in the Astrophysical Journal October 20, 201
Local anodic oxidation of graphene layers on SiC
This work is supported by Presidential Grant МК-5852.2018.2
Magnetoresistance of compensated semimetals in confined geometries
Two-component conductors -- e.g., semi-metals and narrow band semiconductors
-- often exhibit unusually strong magnetoresistance in a wide temperature
range. Suppression of the Hall voltage near charge neutrality in such systems
gives rise to a strong quasiparticle drift in the direction perpendicular to
the electric current and magnetic field. This drift is responsible for a strong
geometrical increase of resistance even in weak magnetic fields. Combining the
Boltzmann kinetic equation with sample electrostatics, we develop a microscopic
theory of magnetotransport in two and three spatial dimensions. The compensated
Hall effect in confined geometry is always accompanied by electron-hole
recombination near the sample edges and at large-scale inhomogeneities. As the
result, classical edge currents may dominate the resistance in the vicinity of
charge compensation. The effect leads to linear magnetoresistance in two
dimensions in a broad range of parameters. In three dimensions, the
magnetoresistance is normally quadratic in the field, with the linear regime
restricted to rectangular samples with magnetic field directed perpendicular to
the sample surface. Finally, we discuss the effects of heat flow and
temperature inhomogeneities on the magnetoresistance.Comment: 22 pages, 7 figures, published versio
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