487 research outputs found
The Hudson Laboratories microbarograph system: Results and future trends
The ultralow frequency microbarograph system is described, and some results for periods ranging from a few minutes to a few hours are presented. Problems encountered during operation of the system are also discussed
Gel'fand-Zetlin Basis and Clebsch-Gordan Coefficients for Covariant Representations of the Lie superalgebra gl(m|n)
A Gel'fand-Zetlin basis is introduced for the irreducible covariant tensor
representations of the Lie superalgebra gl(m|n). Explicit expressions for the
generators of the Lie superalgebra acting on this basis are determined.
Furthermore, Clebsch-Gordan coefficients corresponding to the tensor product of
any covariant tensor representation of gl(m|n) with the natural representation
V ([1,0,...,0]) of gl(m|n) with highest weight (1,0,. . . ,0) are computed.
Both results are steps for the explicit construction of the parastatistics Fock
space.Comment: 16 page
Extremal projectors for contragredient Lie (super)symmetries (short review)
A brief review of the extremal projectors for contragredient Lie
(super)symmetries (finite-dimensional simple Lie algebras, basic classical Lie
superalgebras, infinite-dimensional affine Kac-Moody algebras and
superalgebras, as well as their quantum -analogs) is given. Some
bibliographic comments on the applications of extremal projectors are
presented.Comment: 21 pages, LaTeX; typos corrected, references adde
Cybersecurity conceptsâ taxonomy
Based on the previously accepted taxonomy of concepts, a classification of concepts is proposed that is related to cybersecurity (CS) of objects and currently has the maximum unambiguous correspondence between the terms denoting these concepts and the concepts themselves. When constructing the classification, an attempt was made to apply the fundamentals of the taxonomy theory (systematics), the results of which led to the conclusion that the considered structures of concept systems will be hierarchical (the basic principle of taxonomy) under certain conditions (for example, when using only concepts that relate to the categories of the subject (object)), process, or property). The approach considered made it possible to form a group of terms directly related to the concepts from the proposed classification. This set can be considered as a terminology system related to the objectâs CS. The proposed terms and their definitions do not contradict similar ones being used, but are distinguished by consistency in relation to the terms (definitions) themselves and corresponding concepts, and also have a universal application, which allows their use for almost any CS objects related to information (for example, information and automated systems, informatization systems, sociotechnical systems, cyber-physical systems and information as an object). The results obtained also have practical significance for education in the formation of a modern, methodologically sound conceptual base of students
On irreducibility of tensor products of evaluation modules for the quantum affine algebra
Every irreducible finite-dimensional representation of the quantized
enveloping algebra U_q(gl_n) can be extended to the corresponding quantum
affine algebra via the evaluation homomorphism. We give in explicit form the
necessary and sufficient conditions for irreducibility of tensor products of
such evaluation modules.Comment: 22 pages. Some references are adde
Q-power function over Q-commuting variables and deformed XXX, XXZ chains
We find certain functional identities for the Gauss q-power function of a sum
of q-commuting variables. Then we use these identities to obtain two-parameter
twists of the quantum affine algebra U_q (\hat{sl}_2) and of the Yangian
Y(sl_2). We determine the corresponding deformed trigonometric and rational
quantum R-matrices, which then are used in the computation of deformed XXX and
XXZ Hamiltonians.Comment: LaTeX, 12 page
On Some Lie Bialgebra Structures on Polynomial Algebras and their Quantization
We study classical twists of Lie bialgebra structures on the polynomial
current algebra , where is a simple complex
finite-dimensional Lie algebra. We focus on the structures induced by the
so-called quasi-trigonometric solutions of the classical Yang-Baxter equation.
It turns out that quasi-trigonometric -matrices fall into classes labelled
by the vertices of the extended Dynkin diagram of . We give
complete classification of quasi-trigonometric -matrices belonging to
multiplicity free simple roots (which have coefficient 1 in the decomposition
of the maximal root). We quantize solutions corresponding to the first root of
.Comment: 41 pages, LATE
The Stellar Populations of the Cetus Dwarf Spheroidal Galaxy
We present Hubble Space Telescope Wide Field Planetary Camera 2 photometry in
the V and I passbands of the recently discovered Local Group dwarf spheroidal
galaxy in Cetus. Our color-magnitude diagram extends from above the first
ascent red giant branch (RGB) tip to approximately half a magnitude below the
horizontal branch (HB). Adopting a reddening of E(B-V) = 0.03, the magnitude of
the RGB tip yields a distance modulus of (m-M)o = 24.46 +/- 0.14. After
applying the reddening and distance modulus, we have utilized the color
distribution of RGB stars to determine a mean metal abundance of [Fe/H] = -1.7
on the Zinn & West scale with an intrinsic internal abundance dispersion of
+/-0.2 dex. An indirect calculation of the HB morphology of Cetus based on the
mean dereddened HB color yields (B-R)/(B+V+R) = -0.91 +/- 0.09, which
represents an HB that is redder than what can be attributed solely to Cetus'
metal abundance. As such, Cetus suffers from the `second parameter effect' in
which another parameter besides metallicity is controlling the HB morphology.
If we adopt the conventional `age hypothesis' explanation for the second
parameter effect, then this implies that Cetus is 2-3 Gyr younger than Galactic
globular clusters at its metallicity.Comment: 13 pages, 8 figures, Accepted for publication in the March 10, 2002
Ap
Generalized Paraxial Ray Trace Procedure Derived from Geodesic Deviation
Paraxial ray tracing procedures have become widely accepted techniques for
acoustic models in seismology and underwater acoustics. To date a generic form
of these procedures including fluid motion and time dependence has not appeared
in the literature. A detailed investigation of the characteristic curves of the
equations of hydrodynamics allows for an immediate generalization of the
procedure to be extracted from the equation form geodesic deviation. The
general paraxial ray trace equations serve as an ideal supplement to ordinary
ray tracing in predicting the deformation of acoustic beams in random
environments. The general procedure is derived in terms of affine
parameterization and in a coordinate time parameterization ideal for
application to physical acoustic ray propagation. The formalism is applied to
layered media, where the deviation equation reduces to a second order
differential equation for a single field with a general solution in terms of a
depth integral along the ray path. Some features are illustrated through
special cases which lead to exact solutions in terms of either ordinary or
special functions.Comment: Original; 40 pages (double spaced), 1 figure Replaced version; 36
pages single spaced, 7 figures. Expanded content; Complete derivation of the
equations from the equations of hydrodynamics, introduction of an auxiliary
basis for three dimensional wave-front modeling. Typos in text and equations
correcte
An E-ELT Case Study: Colour-Magnitude Diagrams of an Old Galaxy in the Virgo Cluster
One of the key science goals for a diffraction limited imager on an Extremely
Large Telescope (ELT) is the resolution of individual stars down to faint
limits in distant galaxies. The aim of this study is to test the proposed
capabilities of a multi-conjugate adaptive optics (MCAO) assisted imager
working at the diffraction limit, in IJHK filters, on a 42m diameter ELT to
carry out accurate stellar photometry in crowded images in an Elliptical-like
galaxy at the distance of the Virgo cluster. As the basis for realistic
simulations we have used the phase A studies of the European-ELT project,
including the MICADO imager (Davies & Genzel 2010) and the MAORY MCAO module
(Diolaiti 2010). We convolved a complex resolved stellar population with the
telescope and instrument performance expectations to create realistic images.
We then tested the ability of the currently available photometric packages
STARFINDER and DAOPHOT to handle the simulated images. Our results show that
deep Colour-Magnitude Diagrams (photometric error, 0.25 at I27.2;
H25. and K24.6) of old stellar populations in galaxies, at the
distance of Virgo, are feasible at a maximum surface brightness,
17 mag/arcsec (down to M and M M), and
significantly deeper (photometric error, 0.25 at I29.3; H26.6
and K26.2) for 21 mag/arcsec (down to M and
M M). The photometric errors, and thus also the depth of
the photometry should be improved with photometry packages specifically
designed to adapt to an ELT MCAO Point Spread Function. We also make a simple
comparison between these simulations and what can be expected from a Single
Conjugate Adaptive Optics feed to MICADO and also the James Webb Space
Telescope.Comment: 17 pages, 22 figures, accepted on A&
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