19,229 research outputs found
M-Theory and Hypercharge
We discuss the possibility that the electro-weak and strong interactions
arise as the low energy effective description of branes in M-theory. As a step
towards constructing such a model we show how one can naturally obtain
SU(N_1)\times SU(N_2)\times U(1) gauge theories from branes, including matter
in the bi-fundamental representation of SU(N_1)\times SU(N_2) which are
fractionally charged under U(1).Comment: 29 pages Phyzzx. Two figure
N=2 Superfields and the M-Fivebrane
In this paper we provide a manifestly N=2 supersymmetric formulation of the
M-fivebrane in the presence of threebrane solitons. The superspace form of
four-dimensional effective equations for the threebranes are readily obtained
and yield the complete Seiberg-Witten equations of motion for N=2
super-Yang-Mills. A particularly simple derivation is given by introducing an
N=2 superfield generalisation of the Seiberg-Witten differential.Comment: 14 pages phyzzx. Added paragraph on the existence of a
six-dimensional action. To appear in Phys. Lett.
Partial inner product spaces: Some categorical aspects
We make explicit in terms of categories a number of statements from the
theory of partial inner product spaces (PIP spaces) and operators on them.
In particular, we construct sheaves and cosheaves of operators on certain PIP
spaces of practical interest.Comment: 21 page
Possible identifications of the 3.4 micrometer feature
A feature at 3.4 micrometer was first detected in Comet Halley by the IKS spectrometer on board the Vega 1 probe; and subsequently from the ground. The feature has since been reported in Comet Wilson. The presence of the feature is of considerable interest for a number of reasons. First, it may represent the detection of a new parent molecule, and when combined with data from Giotto and Vega yield new information on cometary chemistry and the early solar system composition. Secondly, it may represent a link to the interstellar medium, the feature corresponds in wavelength and shape with an interstellar feature seen in absorption in a luminous star, towards the Galactic center known as GC-IRS7. The feature in turn is thought to be related with a growing family of unidentified infrared emission features seen in stellar objects, planetary nebulae, reflection nebulae, HII regions and extra galactic sources. These features occur at wavelengths 3.3, 3.4, 3.5, 6.2, 7.7, 8.6, and 11.25 micrometers. Further identification theory is given
Oxygen Abundances in Nearby FGK Stars and the Galactic Chemical Evolution of the Local Disk and Halo
Atmospheric parameters and oxygen abundances of 825 nearby FGK stars are
derived using high-quality spectra and a non-LTE analysis of the 777 nm O I
triplet lines. We assign a kinematic probability for the stars to be thin-disk
(P1), thick-disk (P2), and halo (P3) members. We confirm previous findings of
enhanced [O/Fe] in thick-disk (P2>0.5) relative to thin-disk (P1>0.5) stars
with [Fe/H]<-0.2, as well as a "knee" that connects the mean [O/Fe]-[Fe/H]
trend of thick-disk stars with that of thin-disk members at [Fe/H]>-0.2.
Nevertheless, we find that the kinematic membership criterion fails at
separating perfectly the stars in the [O/Fe]-[Fe/H] plane, even when a very
restrictive kinematic separation is employed. Stars with "intermediate"
kinematics (P1<0.7, P2<0.7) do not all populate the region of the [O/Fe]-[Fe/H]
plane intermediate between the mean thin-disk and thick-disk trends, but their
distribution is not necessarily bimodal. Halo stars (P3>0.5) show a large
star-to-star scatter in [O/Fe]-[Fe/H], but most of it is due to stars with
Galactocentric rotational velocity V-200 km/s
follow an [O/Fe]-[Fe/H] relation with almost no star-to-star scatter. Early
mergers with satellite galaxies explain most of our observations, but the
significant fraction of disk stars with "ambiguous" kinematics and abundances
suggests that scattering by molecular clouds and radial migration have both
played an important role in determining the kinematic and chemical properties
of solar neighborhood stars.Comment: ApJ, in press. Complete tables 2-6 are available in the source
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Chiral currents in gold nanotubes
Results are presented for the electron current in gold chiral nanotubes
(AuNTs). Starting from the band structure of (4,3) and (5,3) AuNTs, we find
that the magnitude of the chiral currents are greater than those found in
carbon nanotubes. We also calculate the associated magnetic flux inside the
tubes and find this to be higher than the case of carbon nanotubes. Although
(4,3) and (5,3) AuNTs carry transverse momenta of similar magnitudes, the
low-bias magnetic flux carried by the former is far greater than that carried
by the latter. This arises because the low-bias longitudinal current carried by
a (4,3) AuNT is significantly smaller than that of a (5,3) AuNT.Comment: 5 pages, 6 figure
Superconductivity-Induced Anderson Localisation
We have studied the effect of a random superconducting order parameter on the
localization of quasi-particles, by numerical finite size scaling of the
Bogoliubov-de Gennes tight-binding Hamiltonian. Anderson localization is
obtained in d=2 and a mobility edge where the states localize is observed in
d=3. The critical behavior and localization exponent are universal within error
bars both for real and complex random order parameter. Experimentally these
results imply a suppression of the electronic contribution to thermal transport
from states above the bulk energy gap.Comment: 4 pages, revtex file, 3 postscript figure
Branes and Calibrated Geometries
The fivebrane worldvolume theory in eleven dimensions is known to contain BPS
threebrane solitons which can also be interpreted as a fivebrane whose
worldvolume is wrapped around a Riemann surface. By considering configurations
of intersecting fivebranes and hence intersecting threebrane solitons, we
determine the Bogomol'nyi equations for more general BPS configurations. We
obtain differential equations, generalising Cauchy-Riemann equations, which
imply that the worldvolume of the fivebrane is wrapped around a calibrated
geometry.Comment: Latex, 35 pages. References added, minor change
The Threebrane Soliton of the M-Fivebrane
We discuss the supersymmetry algebra of the M theory fivebrane and obtain a
new threebrane soliton preserving half of the six-dimensional supersymmetry.
This solution is dimensionally reduced to various D-p-branes.Comment: 10 pages, phyzz
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