19,693 research outputs found
A Note on the Gauge Equivalence between the Manin-Radul and Laberge-Mathieu Super KdV Hierarchies
The gauge equivalence between the Manin-Radul and Laberge-Mathieu super KdV
hierarchies is revisited. Apart from the Inami-Kanno transformation, we show
that there is another gauge transformation which also possess the canonical
property. We explore the relationship of these two gauge transformations from
the Kupershmidt-Wilson theorem viewpoint and, as a by-product, obtain the
Darboux-Backlund transformation for the Manin-Radul super KdV hierarchy. The
geometrical intepretation of these transformations is also briefly discussed.Comment: 8 pages, revtex, 1 figur
The constrained modified KP hierarchy and the generalized Miura transformations
In this letter, we consider the second Hamiltonian structure of the
constrained modified KP hierarchy. After mapping the Lax operator to a pure
differential operator the second structure becomes the sum of the second and
the third Gelfand-Dickey brackets defined by this differential operator. We
simplify this Hamiltonian structure by factorizing the Lax operator into linear
terms.Comment: 8 pages, latex, no figure
Retrieving Bulge and Disk Parameters and Asymptotic Magnitudes from the Growth Curves of Galaxies
We show that the growth curves of galaxies can be used to determine their
bulge and disk parameters and bulge-to-total luminosity ratios, in addition to
their conventional asymptotic magnitudes, provided that the point spread
function is accurately known and signal-to-noise ratio is modest
(S/N). The growth curve is a fundamental quantity that most future
large galaxy imaging surveys will measure. Bulge and disk parameters retrieved
from the growth curve will enable us to perform statistical studies of
luminosity structure for a large number of galaxies.Comment: 28 pages including 13 PS figures; accepted for publication in PAS
B\"{a}cklund transformations for the KP and mKP hierarchies with self-consistent sources
Using gauge transformations for the corresponding generating
pseudo-differential operators in terms of eigenfunctions and adjoint
eigenfunctions, we construct several types of auto-B\"{a}cklund transformations
for the KP hierarchy with self-consistent sources (KPHSCS) and mKP hierarchy
with self-consistent sources (mKPHSCS) respectively. The B\"{a}cklund
transformations from the KPHSCS to mKPHSCS are also constructed in this way.Comment: 22 pages. to appear in J.Phys.
On the Miura map between the dispersionless KP and dispersionless modified KP hierarchies
We investigate the Miura map between the dispersionless KP and dispersionless
modified KP hierarchies. We show that the Miura map is canonical with respect
to their bi-Hamiltonian structures. Moreover, inspired by the works of Takasaki
and Takebe, the twistor construction of solution structure for the
dispersionless modified KP hierarchy is given.Comment: 19 pages, Latex, no figure
Molecular Gas in Candidate Double-Barred Galaxies II. Cooler, Less Dense Gas Associated with Stronger Central Concentrations
We have performed a multi-transition CO study of the centers of seven
double-barred galaxies that exhibit a variety of molecular gas morphologies to
determine if the molecular gas properties are correlated with the nuclear
morphology and star forming activity. Near infrared galaxy surveys have
revealed the existence of nuclear stellar bars in a large number of barred or
lenticular galaxies. High resolution CO maps of these galaxies exhibit a wide
range of morphologies. Recent simulations of double-barred galaxies suggest
that variations in the gas properties may allow it to respond differently to
similar gravitational potentials. We find that the 12CO J=3-2/J=2-1 line ratio
is lower in galaxies with centrally concentrated gas distributions and higher
in galaxies with CO emission dispersed around the galactic center in rings and
peaks. The 13CO/12CO J=2-1 line ratios are similar for all galaxies, which
indicates that the J=3-2/J=2-1 line ratio is tracing variations in gas
temperature and density, rather than variations in optical depth. There is
evidence that the galaxies which contain more centralized CO distributions are
comprised of molecular gas that is cooler and less dense. Observations suggest
that the star formation rates are higher in the galaxies containing the warmer,
denser, less centrally concentrated gas. It is possible that either the bar
dynamics are responsible for the variety of gas distributions and densities
(and hence the star formation rates) or that the star formation alone is
responsible for modifying the gas properties.Comment: 27 pages + 6 figures; to appear in the April 20, 2003 issue of Ap
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