2,627 research outputs found
Connection Between Type A and E Factorizations and Construction of Satellite Algebras
Recently, we introduced a new class of symmetry algebras, called satellite
algebras, which connect with one another wavefunctions belonging to different
potentials of a given family, and corresponding to different energy
eigenvalues. Here the role of the factorization method in the construction of
such algebras is investigated. A general procedure for determining an so(2,2)
or so(2,1) satellite algebra for all the Hamiltonians that admit a type E
factorization is proposed. Such a procedure is based on the known relationship
between type A and E factorizations, combined with an algebraization similar to
that used in the construction of potential algebras. It is illustrated with the
examples of the generalized Morse potential, the Rosen-Morse potential, the
Kepler problem in a space of constant negative curvature, and, in each case,
the conserved quantity is identified. It should be stressed that the method
proposed is fairly general since the other factorization types may be
considered as limiting cases of type A or E factorizations.Comment: 20 pages, LaTeX, no figure, to be published in J. Phys.
Orbital ordering and enhanced magnetic frustration of strained BiMnO3 thin films
Epitaxial thin films of multiferroic perovskite BiMnO3 were synthesized on
SrTiO3 substrates, and orbital ordering and magnetic properties of the thin
films were investigated. The ordering of the Mn^{3+} e_g orbitals at a wave
vector (1/4 1/4 1/4) was detected by Mn K-edge resonant x-ray scattering. This
peculiar orbital order inherently contains magnetic frustration. While bulk
BiMnO3 is known to exhibit simple ferromagnetism, the frustration enhanced by
in-plane compressive strains in the films brings about cluster-glass-like
properties.Comment: 8 pages, 4 figures, accepted to Europhysics Letter
Variable stars in the Open Cluster M11 (NGC 6705)
V-band time-series CCD photometric observations of the intermediate-age open
cluster M11 were performed to search for variable stars. Using these
time-series data, we carefully examined light variations of all stars in the
observing field. A total of 82 variable stars were discovered, of which 39
stars had been detected recently by Hargis et al. (2005). On the basis of
observational properties such as variable period, light curve shape, and
position on a color-magnitude diagram, we classified their variable types as 11
delta Scuti-type pulsating stars, 2 gamma Doradus-type pulsating stars, 40 W
UMa-type contact eclipsing binaries, 13 Algol-type detached eclipsing binaries,
and 16 eclipsing binaries with long period. Cluster membership for each
variable star was deduced from the previous proper motion results (McNamara et
al. 1977) and position on the color-magnitude diagram. Many pulsating stars and
eclipsing binaries in the region of M11 are probable members of the cluster.Comment: 23 pages, 9 figures, 3 tables, and accepted for publication in PAS
Localization-delocalization transition of a reaction-diffusion front near a semipermeable wall
The A+B --> C reaction-diffusion process is studied in a system where the
reagents are separated by a semipermeable wall. We use reaction-diffusion
equations to describe the process and to derive a scaling description for the
long-time behavior of the reaction front. Furthermore, we show that a critical
localization-delocalization transition takes place as a control parameter which
depends on the initial densities and on the diffusion constants is varied. The
transition is between a reaction front of finite width that is localized at the
wall and a front which is detached and moves away from the wall. At the
critical point, the reaction front remains at the wall but its width diverges
with time [as t^(1/6) in mean-field approximation].Comment: 7 pages, PS fil
Testing Consumer Rationality using Perfect Graphs and Oriented Discs
Given a consumer data-set, the axioms of revealed preference proffer a binary
test for rational behaviour. A natural (non-binary) measure of the degree of
rationality exhibited by the consumer is the minimum number of data points
whose removal induces a rationalisable data-set.We study the computational
complexity of the resultant consumer rationality problem in this paper. This
problem is, in the worst case, equivalent (in terms of approximation) to the
directed feedback vertex set problem. Our main result is to obtain an exact
threshold on the number of commodities that separates easy cases and hard
cases. Specifically, for two-commodity markets the consumer rationality problem
is polynomial time solvable; we prove this via a reduction to the vertex cover
problem on perfect graphs. For three-commodity markets, however, the problem is
NP-complete; we prove thisusing a reduction from planar 3-SAT that is based
upon oriented-disc drawings
Evidence of triggered star formation in G327.3-0.6. Dust-continuum mapping of an infrared dark cloud with P-ArT\'eMiS
Aims. Expanding HII regions and propagating shocks are common in the
environment of young high-mass star-forming complexes. They can compress a
pre-existing molecular cloud and trigger the formation of dense cores. We
investigate whether these phenomena can explain the formation of high-mass
protostars within an infrared dark cloud located at the position of G327.3-0.6
in the Galactic plane, in between two large infrared bubbles and two HII
regions. Methods: The region of G327.3-0.6 was imaged at 450 ? m with the CEA
P-ArT\'eMiS bolometer array on the Atacama Pathfinder EXperiment telescope in
Chile. APEX/LABOCA and APEX-2A, and Spitzer/IRAC and MIPS archives data were
used in this study. Results: Ten massive cores were detected in the P-ArT\'eMiS
image, embedded within the infrared dark cloud seen in absorption at both 8 and
24 ?m. Their luminosities and masses indicate that they form high-mass stars.
The kinematical study of the region suggests that the infrared bubbles expand
toward the infrared dark cloud. Conclusions: Under the influence of expanding
bubbles, star formation occurs in the infrared dark areas at the border of HII
regions and infrared bubbles.Comment: 4 page
The integral monodromy of hyperelliptic and trielliptic curves
We compute the \integ/\ell and \integ_\ell monodromy of every irreducible
component of the moduli spaces of hyperelliptic and trielliptic curves. In
particular, we provide a proof that the \integ/\ell monodromy of the moduli
space of hyperelliptic curves of genus is the symplectic group
\sp_{2g}(\integ/\ell). We prove that the \integ/\ell monodromy of the
moduli space of trielliptic curves with signature is the special
unitary group \su_{(r,s)}(\integ/\ell\tensor\integ[\zeta_3])
Generalized Morse Potential: Symmetry and Satellite Potentials
We study in detail the bound state spectrum of the generalized Morse
potential~(GMP), which was proposed by Deng and Fan as a potential function for
diatomic molecules. By connecting the corresponding Schr\"odinger equation with
the Laplace equation on the hyperboloid and the Schr\"odinger equation for the
P\"oschl-Teller potential, we explain the exact solvability of the problem by
an symmetry algebra, and obtain an explicit realization of the latter
as . We prove that some of the generators
connect among themselves wave functions belonging to different GMP's (called
satellite potentials). The conserved quantity is some combination of the
potential parameters instead of the level energy, as for potential algebras.
Hence, belongs to a new class of symmetry algebras. We also stress
the usefulness of our algebraic results for simplifying the calculation of
Frank-Condon factors for electromagnetic transitions between rovibrational
levels based on different electronic states.Comment: 23 pages, LaTeX, 2 figures (on request). one LaTeX problem settle
Reclaiming the political : emancipation and critique in security studies
The critical security studies literature has been marked by a shared commitment towards the politicization of security – that is, the analysis of its assumptions, implications and the practices through which it is (re)produced. In recent years, however, politicization has been accompanied by a tendency to conceive security as connected with a logic of exclusion, totalization and even violence. This has resulted in an imbalanced politicization that weakens critique. Seeking to tackle this situation, the present article engages with contributions that have advanced emancipatory versions of security. Starting with, but going beyond, the so-called Aberystwyth School of security studies, the argument reconsiders the meaning of security as emancipation by making the case for a systematic engagement with the notions of reality and power. This revised version of security as emancipation strengthens critique by addressing political dimensions that have been underplayed in the critical security literature
Star Forming Dense Cloud Cores in the TeV {\gamma}-ray SNR RX J1713.7-3946
RX J1713.7-3946 is one of the TeV {\gamma}-ray supernova remnants (SNRs)
emitting synchrotron X rays. The SNR is associated with molecular gas located
at ~1 kpc. We made new molecular observations toward the dense cloud cores,
peaks A, C and D, in the SNR in the 12CO(J=2-1) and 13CO(J=2-1) transitions at
angular resolution of 90". The most intense core in 13CO, peak C, was also
mapped in the 12CO(J=4-3) transition at angular resolution of 38". Peak C shows
strong signs of active star formation including bipolar outflow and a
far-infrared protostellar source and has a steep gradient with a
r^{-2.20.4} variation in the average density within radius r. Peak C and
the other dense cloud cores are rim-brightened in synchrotron X rays,
suggesting that the dense cloud cores are embedded within or on the outer
boundary of the SNR shell. This confirms the earlier suggestion that the X rays
are physically associated with the molecular gas (Fukui et al. 2003). We
present a scenario where the densest molecular core, peak C, survived against
the blast wave and is now embedded within the SNR. Numerical simulations of the
shock-cloud interaction indicate that a dense clump can indeed survive shock
erosion, since shock propagation speed is stalled in the dense clump.
Additionally, the shock-cloud interaction induces turbulence and magnetic field
amplification around the dense clump that may facilitate particle acceleration
in the lower-density inter-clump space leading to the enhanced synchrotron X
rays around dense cores.Comment: 22 pages, 7 figures, to accepted in The Astrophysical Journal. A full
color version with higher resolution figures is available at
http://www.a.phys.nagoya-u.ac.jp/~sano/ApJ10/ms_sano.pd
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