59,812 research outputs found
A heterotic sigma model with novel target geometry
We construct a (1,2) heterotic sigma model whose target space geometry
consists of a transitive Lie algebroid with complex structure on a Kaehler
manifold. We show that, under certain geometrical and topological conditions,
there are two distinguished topological half--twists of the heterotic sigma
model leading to A and B type half--topological models. Each of these models is
characterized by the usual topological BRST operator, stemming from the
heterotic (0,2) supersymmetry, and a second BRST operator anticommuting with
the former, originating from the (1,0) supersymmetry. These BRST operators
combined in a certain way provide each half--topological model with two
inequivalent BRST structures and, correspondingly, two distinct perturbative
chiral algebras and chiral rings. The latter are studied in detail and
characterized geometrically in terms of Lie algebroid cohomology in the
quasiclassical limit.Comment: 83 pages, no figures, 2 references adde
Management accounting education: is there a gap between academia and practitioner perceptions?
A mail survey was conducted of all Institute of Chartered Accountants of New Zealand accredited Tertiary Education Institutions and 300 randomly selected New Zealand companies to ascertain the views of management accounting academics and practitioners on the contents of management accounting courses and the skills and competencies of recent graduates.
The results show that practitioners placed an emphasis on traditional management accounting techniques, while academics placed an emphasis on contemporary techniques. Both groups were in agreement on the skills and characteristics required of recent graduates. An interesting finding was the emergence of negative comments on the arrogance of new graduates and an increased need for graduates to be work ready. These two aspects were not a feature of previous studies.
The implications of the results are that academics cannot ignore the teaching of traditional management accounting techniques and may need to increase the coverage of the issues involved in implementing contemporary management accounting techniques
Wave propagation in graphite/epoxy laminates due to impact
The low velocity impact response of graphite-epoxy laminates is investigated theoretically and experimentally. A nine-node isoparametric finite element in conjunction with an empirical contact law was used for the theoretical investigation. Flat laminates subjected to pendulum impact were used for the experimental investigation. Theoretical results are in good agreement with strain gage experimental data. The collective results of the investigation indicate that the theoretical procedure describes the impact response of the laminate up to about 150 in/sec. impact velocity
Short-range correlations in dilute atomic Fermi gases with spin-orbit coupling
We study the short-range correlation strength of three dimensional spin half
dilute atomic Fermi gases with spin-orbit coupling. The interatomic interaction
is modeled by the contact pseudopotential. In the high temperature limit, we
derive the expression for the second order virial expansion of the
thermodynamic potential via the ladder diagrams. We further evaluate the second
order virial expansion in the limit that the spin-orbit coupling constants are
small, and find that the correlation strength between the fermions increases as
the forth power of the spin-orbit coupling constants. At zero temperature, we
consider the cases in which there are symmetric spin-orbit couplings in two or
three directions. In such cases, there is always a two-body bound state of zero
net momentum. In the limit that the average interparticle distance is much
larger than the dimension of the two-body bound state, the system primarily
consists of condensed bosonic molecules that fermions pair to form; we find
that the correlation strength also becomes bigger compared to that in the
absence of spin-orbit coupling. Our results indicate that generic spin-orbit
coupling enhances the short-range correlations of the Fermi gases. Measurement
of such enhancement by photoassociation experiment is also discussed.Comment: 7 pages, 4 figure
Singularity problem in f(R) model with non-minimal coupling
We consider the non-minimal coupling between matter and the geometry in the
f(R) theory. In the new theory which we established, a new scalar has
been defined and we give it a certain stability condition. We intend to take a
closer look at the dark energy oscillating behavior in the de-Sitter universe
and the matter era, from which we derive the oscillating frequency, and the
oscillating condition. More importantly, we present the condition of coupling
form that the singularity can be solved. We discuss several specific coupling
forms, and find logarithmic coupling with an oscillating period in the matter era , can improve singularity in the early
universe. The result of numerical calculation verifies our theoretic
calculation about the oscillating frequency. Considering two toy models, we
find the cosmic evolution in the coupling model is nearly the same as that in
the normal f(R) theory when . We also discuss the local tests of the
non-minimal coupling f(R) model, and show the constraint on the coupling form.Comment: 13 pages, 4 figure
- …