1,676 research outputs found
Bi-Hermitian metrics on Kato surfaces
We investigate bi-Hermitian metrics on compact complex surfaces with odd
first Betti number producing new examples with connected anti-canonical divisor
using the general construction of \cite{abd15}. The result is a complete
classification for all \it unbranched \rm Kato surfaces and a classification up
to logarithmic deformation for \it intermediate \rm surfaces.Comment: Major revision: we found a gap in the proof of Theorem 5.1 and
withdrew it; a few Remarks adde
Anti-self-dual bihermitian structures on Inoue surfaces
We show that any hyperbolic Inoue surface (or Inoue-Hirzebruch surface of
even type) admits anti-self-dual bihermitian structures. The same result also
holds for any of its small deformations as far as its anti-canonical system is
non-empty. Similar results are obtained for parabolic Inoue surfaces. Our
method also yields anti-self-dual hermitian metrics on any half Inoue surface.
We use the twistor method of Donaldson-Friedman for the proof.Comment: 69 pages
Bounded derived categories of very simple manifolds
An unrepresentable cohomological functor of finite type of the bounded
derived category of coherent sheaves of a compact complex manifold of dimension
greater than one with no proper closed subvariety is given explicitly in
categorical terms. This is a partial generalization of an impressive result due
to Bondal and Van den Bergh.Comment: 11 pages one important references is added, proof of lemma 2.1 (2)
and many typos are correcte
Thermally-induced magnetic phases in an Ising spin Kondo lattice model on a kagome lattice at 1/3-filling
Numerical investigation on the thermodynamic properties of an Ising spin
Kondo lattice model on a kagome lattice is reported. By using Monte Carlo
simulation, we investigated the magnetic phases at 1/3-filling. We identified
two successive transitions from high-temperature paramagnetic state to a
Kosterlitz-Thouless-like phase in an intermediate temperature range and to a
partially disordered phase at a lower temperature. The partially disordered
state is characterized by coexistence of antiferromagnetic hexagons and
paramagnetic sites with period . We compare the results
with those for the triangular lattice case.Comment: 4 pages, 2 figure
Probing a ferromagnetic critical regime using nonlinear susceptibility
The second order para-ferromagnetic phase transition in a series of amorphous
alloys (Fe{_5}Co{_{50}}Ni{_{17-x}}Cr{_x}B{_{16}}Si{_{12}}) is investigated
using nonlinear susceptibility. A simple molecular field treatment for the
critical region shows that the third order suceptibility (chi{_3}) diverges on
both sides of the transition temperature, and changes sign at T{_C}. This
critical behaviour is observed experimentally in this series of amorphous
ferromagnets, and the related assymptotic critical exponents are calculated. It
is shown that using the proper scaling equations, all the exponents necessary
for a complete characterization of the phase transition can be determined using
linear and nonlinear susceptiblity measurements alone. Using meticulous
nonlinear susceptibility measurements, it is shown that at times chi{_3} can be
more sensitive than the linear susceptibility (chi{_1}) in unravelling the
magnetism of ferromagnetic spin systems. A new technique for accurately
determining T{_C} is discussed, which makes use of the functional form of
chi{_3} in the critical region.Comment: 11 Figures, Submitted to Physical Review
Online Intelligent Controllers for an Enzyme Recovery Plant: Design Methodology and Performance
This paper focuses on the development of intelligent controllers for use in a process of enzyme recovery from pineapple rind. The proteolytic enzyme bromelain (EC 3.4.22.4) is precipitated with alcohol at low temperature in a fed-batch jacketed tank. Temperature control is crucial to avoid irreversible protein denaturation. Fuzzy or neural controllers offer a way of implementing solutions that cover dynamic and nonlinear processes. The design methodology and a comparative study on the performance of fuzzy-PI, neurofuzzy, and neural network intelligent controllers are presented. To tune the fuzzy PI Mamdani controller, various universes of discourse, rule bases, and membership function support sets were tested. A neurofuzzy inference system (ANFIS), based on Takagi-Sugeno rules, and a model predictive controller, based on neural modeling, were developed and tested as well. Using a Fieldbus network architecture, a coolant variable speed pump was driven by the controllers. The experimental results show the effectiveness of fuzzy controllers in comparison to the neural predictive control. The fuzzy PI controller exhibited a reduced error parameter (ITAE), lower power consumption, and better recovery of enzyme activity
Blowing up generalized Kahler 4-manifolds
We show that the blow-up of a generalized Kahler 4-manifold in a
nondegenerate complex point admits a generalized Kahler metric. As with the
blow-up of complex surfaces, this metric may be chosen to coincide with the
original outside a tubular neighbourhood of the exceptional divisor. To
accomplish this, we develop a blow-up operation for bi-Hermitian manifolds.Comment: 16 page
A characterization of compact complex tori via automorphism groups
We show that a compact Kaehler manifold X is a complex torus if both the
continuous part and discrete part of some automorphism group G of X are
infinite groups, unless X is bimeromorphic to a non-trivial G-equivariant
fibration. Some applications to dynamics are given.Comment: title changed, to appear in Math. An
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