4,572 research outputs found
Commuting charges and symmetric spaces
Every classical sigma-model with target space a compact symmetric space
(with classical) is shown to possess infinitely many local, commuting,
conserved charges which can be written in closed form. The spins of these
charges run over a characteristic set of values, playing the role of exponents
of , and repeating modulo an integer which plays the role of a Coxeter
number.Comment: LaTeX, 16 pages; v2: footnote adde
Conserved Charges and Supersymmetry in Principal Chiral Models
We report on investigations of local (and non-local) charges in bosonic and
supersymmetric principal chiral models in 1+1 dimensions. In the bosonic PCM
there is a classically conserved local charge for each symmetric invariant
tensor of the underlying group. These all commute with the non-local Yangian
charges. The algebra of the local charges amongst themselves is rather more
subtle. We give a universal formula for infinite sets of mutually commuting
local charges with spins equal to the exponents of the underlying classical
algebra modulo its Coxeter number. Many of these results extend to the
supersymmetric PCM, but with local conserved charges associated with
antisymmetric invariants in the Lie algebra. We comment briefly on the quantum
conservation of local charges in both the bosonic and super PCMs.Comment: 18 pages, LaTeX. Revised and up-dated version based on conference
talks by JME and NJ
Invariant tensors and Casimir operators for simple compact Lie groups
The Casimir operators of a Lie algebra are in one-to-one correspondence with
the symmetric invariant tensors of the algebra. There is an infinite family of
Casimir operators whose members are expressible in terms of a number of
primitive Casimirs equal to the rank of the underlying group. A systematic
derivation is presented of a complete set of identities expressing
non-primitive symmetric tensors in terms of primitive tensors. Several examples
are given including an application to an exceptional Lie algebra.Comment: 11 pages, LaTeX, minor changes, version in J. Math. Phy
Enhanced star formation: The importance of bars in spiral galaxies
It was found that among an IR luminous subset of nearby spiral galaxies, nearly all of the systems with IRAS colors and luminosities indicative of enhanced star formation are barred. Radio continuum and IR spectroscopic results support the hypothesis that this emission originates within the central 2 kpc; possibly in a circumnuclear ring. It was also found that outer rings are over represented among these barred systems and suggest possible reasons for this phenomena
High resolution sub-millimetre mapping of starburst galaxies: Comparison with CO emission
Researchers present first results from a program of submillimeter continuum mapping of starburst galaxies, and comparison of their dust and CO emission. This project was prompted by surprising results from the first target, the nearby starburst M82, which shows in the dust continuum a morphology quite unlike that of its CO emission, in contrast to what might be expected if both CO and dust are accurately tracing the molecular hydrogen. Possible explanations for this striking difference are discussed. In the light of these results, the program has been extended to include sub-mm mapping of the nearby, vigorously star forming spirals, M83 and Maffei 2. The latter were also observed extensively in CO, in order to study excitation conditions in its central regions. The James Clerk Maxwell Telescope was used in these studies
The Cleo III Ring Imaging Cherenkov Detector
The CLEO detector has been upgraded to include a state of the art particle
identification system, based on the Ring Imaging Cherenkov Detector (RICH)
technology, in order to take data at the upgraded CESR electron positron
collider. The expected performance is reviewed, as well as the preliminary
results from an engineering run during the first few months of operation of the
CLEO III detector.Comment: 5 pages, 2 Figures Talk given by M. Artuso at 8th Pisa Meeting on
Advanced Detectors, May 200
Optimum Monte Carlo Simulations: Some Exact Results
We obtain exact results for the acceptance ratio and mean squared
displacement in Monte Carlo simulations of the simple harmonic oscillator in
dimensions. When the trial displacement is made uniformly in the radius, we
demonstrate that the results are independent of the dimensionality of the
space. We also study the dynamics of the process via a spectral analysis and we
obtain an accurate description for the relaxation time.Comment: 17 pages, 8 figures. submitted to J. Phys.
Discovery of a High Proper Motion L Dwarf Binary: 2MASS J15200224-4422419AB
We report the discovery of the wide L1.5+L4.5 binary 2MASS
J15200224-4422419AB, identified during spectroscopic followup of high proper
motion sources selected from the Two Micron All Sky Survey. This source was
independently identified by Kendall et al. in the SuperCOSMOS Sky Survey.
Resolved JHK photometry and low resolution near-infrared spectroscopy
demonstrate that this system is composed of two well-separated (1"174+/-0"016)
L dwarfs. Component classifications are derived using both spectral ratios and
comparison to near-infrared spectra of previously classified field L dwarfs.
Physical association for the pair is deduced from the large (mu = 0"73+/-0"03
/yr) common proper motion of the components and their similar
spectrophotometric distances (19+/-2 pc). The projected separation of the
binary, 22+/-2 AU, is consistent with maximum separation/total system mass
trends for very low mass binaries. The 2MASS J1520-4422 system exhibits both
large tangential (66+/-7 km/s) and radial velocities (-70+/-18 km/s), and its
motion in the local standard of rest suggests that it is an old member of the
Galactic disk population. This system joins a growing list of well-separated
(>0"5), very low mass binaries, and is an excellent target for resolved optical
spectroscopy to constrain its age as well as trace activity/rotation trends
near the hydrogen-burning limit.Comment: 35 pages, 8 figures; accepted for publication to ApJ; see also
Kendall et al. astro-ph/060939
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