575 research outputs found
A general weak nonlinearity model for LNAs
This paper presents a general weak nonlinearity model that can be used to model, analyze and describe the distortion behavior of various low noise amplifier topologies in both narrowband and wideband applications. Represented by compact closed-form expressions our model can be easily utilized by both circuit designers and LNA design automation algorithms.\ud
Simulations for three LNA topologies at different operating conditions show that the model describes IM components with an error lower than 0.1% and a one order of magnitude faster response time. The model also indicates that for narrowband IM2@w1-w2 all the nonlinear capacitances can be neglected while for narrowband IM3 the nonlinear capacitances at the drainterminal can be neglected
The effects of macroscopic inhomogeneities on the magneto transport properties of the electron gas in two dimensions
In experiments on electron transport the macroscopic inhomogeneities in the
sample play a fundamental role. In this paper and a subsequent one we introduce
and develop a general formalism that captures the principal features of sample
inhomogeneities (density gradients, contact misalignments) in the magneto
resistance data taken from low mobility heterostructures. We present detailed
assessments and experimental investigations of the different regimes of
physical interest, notably the regime of semiclassical transport at weak
magnetic fields, the plateau-plateau transitions as well as the
plateau-insulator transition that generally occurs at much stronger values of
the external field only.
It is shown that the semiclassical regime at weak fields plays an integral
role in the general understanding of the experiments on the quantum Hall
regime. The results of this paper clearly indicate that the plateau-plateau
transitions, unlike the the plateau-insulator transition, are fundamentally
affected by the presence of sample inhomogeneities. We propose a universal
scaling result for the magneto resistance parameters. This result facilitates,
amongst many other things, a detailed understanding of the difficulties
associated with the experimental methodology of H.P. Wei et.al in extracting
the quantum critical behavior of the electron gas from the transport
measurements conducted on the plateau-plateau transitions.Comment: 20 pages, 9 figure
Geometric measure of entanglement and applications to bipartite and multipartite quantum states
The degree to which a pure quantum state is entangled can be characterized by
the distance or angle to the nearest unentangled state. This geometric measure
of entanglement, already present in a number of settings (see Shimony 1995 and
Barnum and Linden 2001), is explored for bipartite and multipartite pure and
mixed states. The measure is determined analytically for arbitrary two-qubit
mixed states and for generalized Werner and isotropic states, and is also
applied to certain multipartite mixed states. In particular, a detailed
analysis is given for arbitrary mixtures of three-qubit GHZ, W and inverted-W
states. Along the way, we point out connections of the geometric measure of
entanglement with entanglement witnesses and with the Hartree approximation
method.Comment: 13 pages, 11 figures, this is a combination of three previous
manuscripts (quant-ph/0212030, quant-ph/0303079, and quant-ph/0303158) made
more extensive and coherent. To appear in PR
Short-Range Interactions and Scaling Near Integer Quantum Hall Transitions
We study the influence of short-range electron-electron interactions on
scaling behavior near the integer quantum Hall plateau transitions. Short-range
interactions are known to be irrelevant at the renormalization group fixed
point which represents the transition in the non-interacting system. We find,
nevertheless, that transport properties change discontinuously when
interactions are introduced. Most importantly, in the thermodynamic limit the
conductivity at finite temperature is zero without interactions, but non-zero
in the presence of arbitrarily weak interactions. In addition, scaling as a
function of frequency, , and temperature, , is determined by the
scaling variable (where is the exponent for the temperature
dependence of the inelastic scattering rate) and not by , as it would
be at a conventional quantum phase transition described by an interacting fixed
point. We express the inelastic exponent, , and the thermal exponent, ,
in terms of the scaling dimension, , of the interaction strength
and the dynamical exponent (which has the value ), obtaining
and .Comment: 9 pages, 4 figures, submitted to Physical Review
A Lorentz Invariance Violating Cosmology on the DGP Brane
We study cosmological implications of a Lorentz invariance violating
DGP-inspired braneworld scenario. A minimally coupled scalar field and a
single, fixed-norm, Lorentz-violating timelike vector field within an
interactive picture provide a wide parameter space which accounts for late-time
acceleration and transition to phantom phase of the scalar field.Comment: 23 pages, 8 figures, accepted for publication in JCA
A Model of Fermion Masses and Flavor Mixings with Family Symmetry
The family symmetry is proposed to solve flavor problems
about fermion masses and flavor mixings. It's breaking is implemented by some
flavon fields at the high-energy scale. In addition a discrete group is
introduced to generate tiny neutrino masses, which is broken by a real singlet
scalar field at the middle-energy scale. The low-energy effective theory is
elegantly obtained after all of super-heavy fermions are integrated out and
decoupling. All the fermion mass matrices are regularly characterized by four
fundamental matrices and thirteen parameters. The model can perfectly fit and
account for all the current experimental data about the fermion masses and
flavor mixings, in particular, it finely predicts the first generation quark
masses and the values of and in neutrino
physics. All of the results are promising to be tested in the future
experiments.Comment: 14 pages, 1 figure, to make a few of corrections to the old version.
arXiv admin note: substantial text overlap with arXiv:1011.457
Generalized measurements by linear elements
I give a first characterization of the class of generalized measurements that
can be exactly realized on a pair of qudits encoded in indistinguishable
particles, by using only linear elements and particle detectors. Two immediate
results follow from this characterization. (i) The Schmidt number of each POVM
element cannot exceed the number of initial particles. This rules out any
possibility of performing perfect Bell-measurements for qudits. (ii) The
maximum probability of performing a generalized incomplete Bell-measurement is
1/2.Comment: 4 pages. Submitted to Phys. Rev.
Reducing human pressure on farmland could rescue China’s declining wintering geese
Conservation Biolog
Scalar field exact solutions for non-flat FLRW cosmology: A technique from non-linear Schr\"odinger-type formulation
We report a method of solving for canonical scalar field exact solution in a
non-flat FLRW universe with barotropic fluid using non-linear Schr\"{o}dinger
(NLS)-type formulation in comparison to the method in the standard Friedmann
framework. We consider phantom and non-phantom scalar field cases with
exponential and power-law accelerating expansion. Analysis on effective
equation of state to both cases of expansion is also performed. We speculate
and comment on some advantage and disadvantage of using the NLS formulation in
solving for the exact solution.Comment: 12 pages, GERG format, Reference added. accepted by Gen. Relativ. and
Gra
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