2,691 research outputs found
Discrete time Bogoyavlensky lattices
Discretizations of the Bogoyavlensky lattices are introduced, belonging to
the same hierarchies as the continuous--time systems. The construction
exemplifies the general scheme for integrable discretization of systems on Lie
algebras with --matrix Poisson brackets. An initial value problem for the
difference equations is solved in terms of a factorization problem in a group.
Interpolating Hamiltonian flow is found.Comment: 22 pages, LaTeX, revised version (the third lattice discretized now!
Observations of Oscillating Cavitation on a Flat Plate Hydrofoil
An experimental investigation was made to clarify the characteristics of oscillating cavitation on a flat plate hydrofoil in a water tunnel. Dynamic the behavior of oscillating cavitation is discussed from the unsteady pressure measurements at the upstream of the blade and the visual observations of cavitation phenomena using high-speed video recording. It was found that the mean cavity length characterizes the fundamental characteristics of cavity oscillation. The cavity oscillations are categorized into two types, i.e. the transitional cavity oscillation and the partial cavity oscillation
X-ray Development of the Classical Nova V2672 Ophiuchi with Suzaku
We report the Suzaku detection of a rapid flare-like X-ray flux amplification
early in the development of the classical nova V2672 Ophiuchi. Two
target-of-opportunity ~25 ks X-ray observations were made 12 and 22 days after
the outburst. The flux amplification was found in the latter half of day 12.
Time-sliced spectra are characterized by a growing supersoft excess with
edge-like structures and a relatively stable optically-thin thermal component
with Ka emission lines from highly ionized Si. The observed spectral evolution
is consistent with a model that has a time development of circumstellar
absorption, for which we obtain the decline rate of ~10-40 % in a time scale of
0.2 d on day 12. Such a rapid drop of absorption and short-term flux
variability on day 12 suggest inhomogeneous ejecta with dense blobs/holes in
the line of sight. Then on day 22 the fluxes of both supersoft and thin-thermal
plasma components become significantly fainter. Based on the serendipitous
results we discuss the nature of this source in the context of both short- and
long-term X-ray behavior.Comment: To appear in PASJ; 9 pages, 5 figures, 2 table
Contribution of Type Ia and Type II Supernovae for Intra-Cluster Medium Enrichment
The origin of the chemical composition of the intracluster medium (ICM) is
discussed in this paper. In particular, the contribution from Type Ia
supernovae (SNe Ia) to the ICM enrichment is shown to exist by adopting the
fitting formulas which have been used in the analysis of the solar system
abundances. Our analysis means that we can use the frequency of SNe Ia relative
to SNe II as the better measure than for
estimating the contribution of SNe Ia. Moreover, the chemical compositions of
ICMs are shown to be similar to that of the solar system abundances. We can
also reproduce the sulfur/iron abundance ratio within a factor of 2, which
means that the abundance problem of sulfur needs not to be emphasized too
strongly. We need more precise observations to conclude whether ICMs really
suffer the shortage problem of sulfur or not.Comment: 20 pages, LaTeX text and 15 postscript figures. Accepted for
publication in Astrophysical Journa
Age Dating of a High-Redshift QSO B1422+231 at Z=3.62 and its Cosmological Implications
The observed Fe II(UV+optical)/Mg II lambda lambda 2796,2804 flux ratio from
a gravitationally lensed quasar B1422+231 at z=3.62 is interpreted in terms of
detailed modeling of photoionization and chemical enrichment in the broad-line
region (BLR) of the host galaxy. The delayed iron enrichment by Type Ia
supernovae is used as a cosmic clock. Our standard model, which matches the Fe
II/Mg II ratio, requires the age of 1.5 Gyr for B1422+231 with a lower bound of
1.3 Gyr, which exceeds the expansion age of the Einstein-de Sitter Omega_0=1
universe at a redshift of 3.62 for any value of the Hubble constant in the
currently accepted range, H_0=60-80 km,s^{-1},Mpc^{-1}. This problem of an age
discrepancy at z=3.62 can be unraveled in a low-density Omega_0<0.2 universe,
either with or without a cosmological constant, depending on the allowable
redshift range of galaxy formation. However, whether the cosmological constant
is a required option in modern cosmology awaits a thorough understanding of
line transfer processes in the BLRs.Comment: 7 pages including 3 figures, to appear in ApJ Letter
An Algebraic Model for the Multiple Meixner Polynomials of the First Kind
An interpretation of the multiple Meixner polynomials of the first kind is
provided through an infinite Lie algebra realized in terms of the creation and
annihilation operators of a set of independent oscillators. The model is used
to derive properties of these orthogonal polynomials
The algebra of dual -1 Hahn polynomials and the Clebsch-Gordan problem of sl_{-1}(2)
The algebra H of the dual -1 Hahn polynomials is derived and shown to arise
in the Clebsch-Gordan problem of sl_{-1}(2). The dual -1 Hahn polynomials are
the bispectral polynomials of a discrete argument obtained from a q-> -1 limit
of the dual q-Hahn polynomials. The Hopf algebra sl_{-1}(2) has four generators
including an involution, it is also a q-> -1 limit of the quantum algebra
sl_{q}(2) and furthermore, the dynamical algebra of the parabose oscillator.
The algebra H, a two-parameter generalization of u(2) with an involution as
additional generator, is first derived from the recurrence relation of the -1
Hahn polynomials. It is then shown that H can be realized in terms of the
generators of two added sl_{-1}(2) algebras, so that the Clebsch-Gordan
coefficients of sl_{-1}(2) are dual -1 Hahn polynomials. An irreducible
representation of H involving five-diagonal matrices and connected to the
difference equation of the dual -1 Hahn polynomials is constructed.Comment: 15 pages, Some minor changes from version #
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