30,694 research outputs found
Linear complementarity problems on extended second order cones
In this paper, we study the linear complementarity problems on extended
second order cones. We convert a linear complementarity problem on an extended
second order cone into a mixed complementarity problem on the non-negative
orthant. We state necessary and sufficient conditions for a point to be a
solution of the converted problem. We also present solution strategies for this
problem, such as the Newton method and Levenberg-Marquardt algorithm. Finally,
we present some numerical examples
On the nature of the lightest scalar resonances
We briefly review the recent progresses in the new unitarization approach
being developed by us. Especially we discuss the large
scatterings by making use of the partial wave matrix parametrization form.
We find that the pole may move to the negative real axis on the second
sheet of the complex plane, therefore it raises the interesting question
that this `' pole may be related to the in the linear
model.Comment: Talk presented by Zheng at ``Quark Confinement and Hadron
Spectroscopy VI'', 21--25 Sept. 2004, Cagliari, Italy. 3 pages with 2 figure
Is the meson a dynamically generated resonance? -- a lesson learned from the O(N) model and beyond
O(N) linear model is solvable in the large limit and hence
provides a useful theoretical laboratory to test various unitarization
approximations. We find that the large limit and the
limit do not commute. In order to get the correct large spectrum one has
to firstly take the large limit. We argue that the meson may
not be described as generated dynamically. On the contrary, it is most
appropriately described at the same level as the pions, i.e, both appear
explicitly in the effective lagrangian. Actually it is very likely the
meson responsible for the spontaneous chiral symmetry breaking in a lagrangian
with linearly realized chiral symmetry.Comment: 15 pages, 3 figurs; references added; discussions slightly modified;
revised version accepted by IJMP
Realization of Artificial Ice Systems for Magnetic Vortices in a Superconducting MoGe Thin-film with Patterned Nanostructures
We report an anomalous matching effect in MoGe thin films containing pairs of
circular holes arranged in such a way that four of those pairs meet at each
vertex point of a square lattice. A remarkably pronounced fractional matching
was observed in the magnetic field dependences of both the resistance and the
critical current. At the half matching field the critical current can be even
higher than that at zero field. This has never been observed before for
vortices in superconductors with pinning arrays. Numerical simulations within
the nonlinear Ginzburg-Landau theory reveal a square vortex ice configuration
in the ground state at the half matching field and demonstrate similar
characteristic features in the field dependence of the critical current,
confirming the experimental realization of an artificial ice system for
vortices for the first time.Comment: To appear in Phys. Rev. Let
Recent Developments In Computational Fracture Mechanics At Cardiff
The following most recent developments in computational fracture mechanics at Cardiff University are reviewed: hybrid crack element (HCE) which can give directly the stress intensity factor (SIF) as well as the coefficients of higher order terms in the plane linear elastic crack tip asymptotic field; extended finite element method (XFEM) which avoids using a mesh conforming with the crack as is the case with the traditional FEM and gives highly accurate crack tip fields; penalty function technique for handling point loads; and compressed sparse row (CSR) storage scheme for efficient implementation of the above techniques. Possible future improvements are also discussed
A single radio-emitting nucleus in the dual AGN candidate NGC 5515
The Seyfert galaxy NGC 5515 has double-peaked narrow-line emission in its
optical spectrum, and it has been suggested that this could indicate that it
has two active nuclei. We observed the source with high resolution Very Long
Baseline Interferometry (VLBI) at two radio frequencies, reduced archival Very
Large Array data, and re-analysed its optical spectrum. We detected a single,
compact radio source at the position of NGC 5515, with no additional radio
emission in its vicinity. The optical spectrum of the source shows that the
blue and red components of the double-peaked lines have very similar
characteristics. While we cannot rule out unambiguously that NGC 5515 harbours
a dual AGN, the assumption of a single AGN provides a more plausible
explanation for the radio observations and the optical spectrum.Comment: 6 pages, 1 figure, accepted for publication in MNRA
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