17,210 research outputs found
Optimal domain of -concave operators and vector measure representation of -concave Banach lattices
Given a Banach space valued -concave linear operator defined on a
-order continuous quasi-Banach function space, we provide a description
of the optimal domain of preserving -concavity, that is, the largest
-order continuous quasi-Banach function space to which can be
extended as a -concave operator. We show in this way the existence of
maximal extensions for -concave operators. As an application, we show a
representation theorem for -concave Banach lattices through spaces of
integrable functions with respect to a vector measure. This result culminates a
series of representation theorems for Banach lattices using vector measures
that have been obtained in the last twenty years
The geometry of L^p-spaces over atomless measure spaces and the Daugavet property
We show that -spaces over atomless measure spaces can be characterized
in terms of a -concavity type geometric property that is related with the
Daugavet property
Numerical study of relaxation in electron glasses
We perform a numerical simulation of energy relaxation in three-dimensional
electron glasses in the strongly localized regime at finite temperatures. We
consider systems with no interactions, with long-range Coulomb interactions and
with short-range interactions, obtaining a power law relaxation with an
exponent of 0.15, which is independent of the parameters of the problem and of
the type of interaction. At very long times, we always find an exponential
regime whose characteristic time strongly depends on temperature, system size,
interaction type and localization radius. We extrapolate the longest relaxation
time to macroscopic sizes and, for interacting samples, obtain values much
larger than the measuring time. We finally study the number of electrons
participating in the relaxation processes of very low energy configurations.Comment: 6 eps figures. To be published in Phys. Rev.
High Gain Amplifier with Enhanced Cascoded Compensation
A two-stage CMOS operational amplifier with both, gain-boosting and indirect current feedback frequency compensation performed by means of regulated cascode amplifiers, is presented. By using quasi-floating-gate transistors (QFGT) the supply requirements, the number of capacitors and the size of the compensation capacitors respect to other Miller schemes are reduced. A prototype was fabricated using a 0.5 μm technology, resulting, for a load of 45 pF and supply voltage of 1.65 V, in open-loop-gain of 129 dB, 23 MHz of gain-bandwidth product, 60o phase margin, 675 μW power consumption and 1% settling time of 28 ns
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