28,592 research outputs found
Dualisation of the D=7 Heterotic String
The dualisation and the first-order formulation of the D=7 abelian Yang-Mills
supergravity which is the low energy effective limit of the D=7 fully Higssed
heterotic string is discussed. The non-linear coset formulation of the scalars
is enlarged to include the entire bosonic sector by introducing dual fields and
by constructing the Lie superalgebra which generates the dualized coset
element.Comment: 20 page
Z(3) Interfaces in Lattice Gauge Theory
A study is made of properties of the Z(3) interface which forms between the
different ordered phases of pure SU(3) gauge theory above a critical
temperature. The theory is simulated on a (2+1)-D lattice at various
temperatures above this critical point. At high temperatures, the interface
tension is shown to agree well with the prediction of perturbation theory. Near
the critical temperature, the interface behaviour is characterised by various
displacement moments, and modelled by an interacting scalar field theory. This
thesis is provided for reference, as it gives full details of the computational
and statistical methods outlined only briefly in preprints hep-lat/9605040 and
hep-lat/9607005.Comment: TeX, 143 pages, 52 figure
Dualisation of the D=9 Matter Coupled Supergravity
We perform the bosonic dualisation of the matter coupled N=1, D=9
supergravity. We derive the Lie superalgebra which parameterizes the coset map
whose Cartan form realizes the second-order bosonic field equations. Following
the non-linear coset construction we present the first-order formulation of the
bosonic field equations as a twisted self-duality condition.Comment: 16 page
The Connection between Supernova Remnants and the Galactic Magnetic Field: A Global Radio Study of the Axisymmetric Sample
The study of supernova remnants (SNRs) is fundamental to understanding the
chemical enrichment and magnetism in galaxies, including our own Milky Way. In
an effort to understand the connection between the morphology of SNRs and the
Galactic magnetic field (GMF), we have examined the radio images of all known
SNRs in our Galaxy and compiled a large sample that have an "axisymmetric"
morphology, which we define to mean SNRs with a "bilateral" or "barrel"-shaped
morphology, in addition to one-sided shells. We selected the cleanest examples
and model each of these at their appropriate Galactic position using two GMF
models, those of Jansson & Farrar (2012a), which includes a vertical halo
component, and Sun et al. (2008) that is oriented entirely parallel to the
plane. Since the magnitude and relative orientation of the magnetic field
changes with distance from the sun, we analyse a range of distances, from 0.5
to 10 kpc in each case. Using a physically motivated model of a SNR expanding
into the ambient GMF, we find the models using Jansson & Farrar (2012a) are
able to reproduce observed morphologies of many SNRs in our sample. These
results strongly support the presence of an off-plane, vertical component to
the GMF, and the importance of the Galactic field on SNR morphology. Our
approach also provides a potential new method for determining distances to
SNRs, or conversely, distances to features in the large-scale GMF if SNR
distances are known.Comment: 24 pages, 8 figures plus one 5-page appendix figure, 3 tables,
accepted to A&
Fermi surface of the colossal magnetoresistance perovskite La_{0.7}Sr_{0.3}MnO_{3}
Materials that exhibit colossal magnetoresistance (CMR) are currently the
focus of an intense research effort, driven by the technological applications
that their sensitivity lends them to. Using the angular correlation of photons
from electron-positron annihilation, we present a first glimpse of the Fermi
surface of a material that exhibits CMR, supported by ``virtual crystal''
electronic structure calculations. The Fermi surface is shown to be
sufficiently cubic in nature that it is likely to support nesting.Comment: 5 pages, 5 PS figure
Very Extended and at low levels, Gravity and Supergravity
We define a level for a large class of Lorentzian Kac-Moody algebras. Using
this we find the representation content of very extended and
(i.e. ) at low levels in terms of and
representations respectively. The results are consistent with the conjectured
very extended and symmetries of gravity and maximal supergravity
theories given respectively in hep-th/0104081 and hep-th/0107209. We explain
how these results provided further evidence for these conjectures.Comment: 16 pages, plain tex (equation 3.3 modified and one reference
expanded
Analytical Aspects of Absorption Spectroelectrochemistry at a Platinum Electrode- II: Quantitative Basis and Study of Organic Compounds
The theoretical basis for a new spectroelectrochemical technique, in which a narrow lightbeamis passed at grazing incidence over a plane electrode surface, has been derived. Agreement betweentheoretical and experimental behaviour has been obtained for a number of organic molecules withwell-defined redox behaviour. The advantages of this technique over other spectroelectrochemical techniquesare discussed with respect to potential applications in quantitative analysis and electrochemicalstudies
Experimental determination of the state-dependent enhancement of the electron-positron momentum density in solids
The state-dependence of the enhancement of the electron-positron momentum
density is investigated for some transition and simple metals (Cr, V, Ag and
Al). Quantitative comparison with linearized muffin-tin orbital calculations of
the corresponding quantity in the first Brillouin zone is shown to yield a
measurement of the enhancement of the s, p and d states, independent of any
parameterizations in terms of the electron density local to the positron. An
empirical correction that can be applied to a first-principles state-dependent
model is proposed that reproduces the measured state-dependence very well,
yielding a general, predictive model for the enhancement of the momentum
distribution of positron annihilation measurements, including those of angular
correlation and coincidence Doppler broadening techniques
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Analytical Aspects of Absorption Spectroelectrochemistry at a Platinum Electrode- I study of Metal Ions
Anomalous isotopic predissociation in the F³Πu(v=1) state of O₂
Using a tunable, narrow-bandwidth vacuum-ultraviolet source based on third-harmonic generation from excimer-pumped dye-laser radiation, the F³Πu←X³Σg-(1,0)photoabsorption cross sections of ¹⁶O₂ and ¹⁸O₂ have been recorded in high resolution. Rotational analyses have been performed and the resultant F(v=1) term values fitted to the ³Π Hamiltonian of Brown and Merer [J. Mol. Spectrosc. 74, 488 (1979)]. A large rotationless isotope effect is observed in the F(v=1)predissociation, wherein the Lorentzian linewidth component for ¹⁸O₂ is a factor of ∼50 smaller than the corresponding ¹⁶O₂linewidth. This effect, a consequence of the nonadiabatic rotationless predissociation mechanism, is described using a coupled-channel treatment of the strongly Rydberg-valence-mixed 3Πu states. Significant J, e/f-parity, and sublevel dependencies observed in the isotopic F(v=1) rotational widths are found to derive from an indirect predissociation mechanism involving an accidental degeneracy with the E³Σ−u(v=3) level, itself strongly predissociated by ³Σ−u Rydberg-valence interactions, together with L-uncoupling (rotational) interactions between the Rydberg components of the F and E states. Transitions into the E(v=3) level are observed directly for the first time, specifically in the ¹⁸O₂ spectrumPartial support
was provided by an NSF International Opportunities for Scientists
and Engineers Program Grant No. INT-9513350, and
Visiting Fellowships for G.S. and J.B.W. at the Australian
National University
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