12,789 research outputs found
Disk tracing for B[e] supergiants in the Magellanic Clouds
B[e] supergiants are evolved massive stars with a complex circumstellar
environment. A number of important emission features probe the structure and
the kinematics of the circumstellar material. In our survey of Magellanic Cloud
B[e] supergiants we focus on the [OI] and [CaII] emission lines, which we
identified in four more objects.Comment: 2 pages; 1 figure; submitted to the proceedings of the Physics of
Evolved Stars - A conference dedicated to the memory of Olivier Chesneau,
Nice, France, June 8-12, 201
The High-Order-Multiplicity of Unusually Wide M-dwarf Binaries: Eleven New Triple and Quadruple Systems
M-dwarfs in extremely wide binary systems are very rare, and may thus have
different formation processes from those found as single stars or close
binaries in the field. In this paper we search for close companions to a new
sample of 36 extremely wide M-dwarf binaries, covering a spectral type range of
M1 to M5 and a separation range of 600 - 6500 AU. We discover 10 new triple
systems and one new quadruple system. We carefully account for selection
effects including proper motion, magnitude limits, the detection of close
binaries in the SDSS, and other sample biases. The bias-corrected total
high-order-multiple fraction is 45% (+18%/-16%) and the bias-corrected
incidence of quadruple systems is < 5%, both statistically compatible with that
found for the more common close M-dwarf multiple systems. Almost all the
detected companions have similar masses to their primaries, although two very
low mass companions, including a candidate brown dwarf, are found at relatively
large separations. We find that the close-binary separation distribution is
strongly peaked towards < 30AU separations. There is marginally significant
evidence for a change in high-order M-dwarf multiplicity with binding energy
and total mass. We also find 2-sigma evidence of an unexpected increased
high-order-multiple fraction for the widest targets in our survey, with a
high-order-multiple fraction of 21% (+17%/-7%) for systems with separations up
to 2000AU, compared to 77% (+9%/-22%) for systems with separations > 4000AU.
These results suggest that the very widest M-dwarf binary systems need higher
masses to form or to survive.Comment: 11 pages, 14 figures, accepted for publication in Ap
Mechanical Mixing in Nonlinear Nanomechanical Resonators
Nanomechanical resonators, machined out of Silicon-on-Insulator wafers, are
operated in the nonlinear regime to investigate higher-order mechanical mixing
at radio frequencies, relevant to signal processing and nonlinear dynamics on
nanometer scales. Driven by two neighboring frequencies the resonators generate
rich power spectra exhibiting a multitude of satellite peaks. This nonlinear
response is studied and compared to -order perturbation theory and
nonperturbative numerical calculations.Comment: 5 pages, 7 figure
High maternal androstenedione levels during pregnancy in a small precocial mammal with female genital masculinisation
-Masculinisation of female genitalia is an intriguing phenomenon amongst some mammalian species and its endocrinological basis as well as its adaptive value is still heavily debated. We recently reported female genital masculinisation in Cavia magna. The closely related C. aperea, does not show such masculinisation providing an unique opportunity to investigate potential endocrinological mechanisms underlying this difference. For both species we determined plasma levels of androstenedione and testosterone in adults of both sexes, and in females during different stages of pregnancy. Consistent with the normal mammalian pattern males showed higher levels of both androgens than conspecific females. Androgen profiles during pregnancy differed significantly between C. magna and C. aperea females: during mid-pregnancy androstenedione levels were strongly elevated in the masculinised C. magna, but not in C. aperea, indicating that high levels of this androgen may be involved in the differentiation of masculinized genitalia in female C. magna, as has been suggested for the spotted hyena. In both C. magna and the spotted hyena the pups show a highly advanced state of maturation, but in contrast to the hyena female C. magna are not overly aggressive. We therefore propose that female genital masculinisation might be a side effect of early exposure to elevated levels of maternal androgens that might be selected for to speed up precocial development.
Rigid invariance as derived from BRS invariance: The abelian Higgs model
Consequences of a symmetry, e.g.\ relations amongst Green functions, are
renormalization scheme independently expressed in terms of a rigid Ward
identity. The corresponding local version yields information on the respective
current. In the case of spontaneous breakdown one has to define the theory via
the BRS invariance and thus to construct rigid and current Ward identity
non-trivially in accordance with it. We performed this construction to all
orders of perturbation theory in the abelian Higgs model as a prelude to the
standard model. A technical tool of interest in itself is the use of a doublet
of external scalar ``background'' fields. The Callan-Symanzik equation has an
interesting form and follows easily once the rigid invariance is established.Comment: 33 pages, Plain Te
5D Attractors with Higher Derivatives
We analyze higher derivative corrections to attractor geometries in five
dimensions. We find corrected AdS_3xS^2 geometries by solving the equations of
motion coming from a recently constructed four-derivative supergravity action
in five dimensions. The result allows us to explicitly verify a previous
anomaly based derivation of the AdS_3 central charges of this theory. Also, by
dimensional reduction we compare our results with those of the 4D higher
derivative attractor, and find complete agreement.Comment: 18 pages, harvma
Transmitting qudits through larger quantum channels
We address the problem of transmitting states belonging to finite dimensional
Hilbert space through a quantum channel associated with a larger (even infinite
dimensional) Hilbert space.Comment: 5 pages, ReVTeX, minor changes, to appear in J. Phys.
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