1,620 research outputs found
Quantum phenomena modelled by interactions between many classical worlds
We investigate whether quantum theory can be understood as the continuum
limit of a mechanical theory, in which there is a huge, but finite, number of
classical 'worlds', and quantum effects arise solely from a universal
interaction between these worlds, without reference to any wave function. Here
a `world' means an entire universe with well-defined properties, determined by
the classical configuration of its particles and fields. In our approach each
world evolves deterministically; probabilities arise due to ignorance as to
which world a given observer occupies; and we argue that in the limit of
infinitely many worlds the wave function can be recovered (as a secondary
object) from the motion of these worlds. We introduce a simple model of such a
'many interacting worlds' approach and show that it can reproduce some generic
quantum phenomena---such as Ehrenfest's theorem, wavepacket spreading, barrier
tunneling and zero point energy---as a direct consequence of mutual repulsion
between worlds. Finally, we perform numerical simulations using our approach.
We demonstrate, first, that it can be used to calculate quantum ground states,
and second, that it is capable of reproducing, at least qualitatively, the
double-slit interference phenomenon.Comment: Published version (including further discussion of interpretation and
quantum limit
Ground states in the Many Interacting Worlds approach
Recently the Many-Interacting-Worlds (MIW) approach to a quantum theory
without wave functions was proposed. This approach leads quite naturally to
numerical integrators of the Schr\"odinger equation. It has been suggested that
such integrators may feature advantages over fixed-grid methods for higher
numbers of degrees of freedom. However, as yet, little is known about concrete
MIW models for more than one spatial dimension and/or more than one particle.
In this work we develop the MIW approach further to treat arbitrary degrees of
freedom, and provide a systematic study of a corresponding numerical
implementation for computing one-particle ground and excited states in one
dimension, and ground states in two spatial dimensions. With this step towards
the treatment of higher degrees of freedom we hope to stimulate their further
study.Comment: 16 pages, 8 figure
Reliable dual-redundant sensor failure detection and identification for the NASA F-8 DFBW aircraft
A technique was developed which provides reliable failure detection and identification (FDI) for a dual redundant subset of the flight control sensors onboard the NASA F-8 digital fly by wire (DFBW) aircraft. The technique was successfully applied to simulated sensor failures on the real time F-8 digital simulator and to sensor failures injected on telemetry data from a test flight of the F-8 DFBW aircraft. For failure identification the technique utilized the analytic redundancy which exists as functional and kinematic relationships among the various quantities being measured by the different control sensor types. The technique can be used not only in a dual redundant sensor system, but also in a more highly redundant system after FDI by conventional voting techniques reduced to two the number of unfailed sensors of a particular type. In addition the technique can be easily extended to the case in which only one sensor of a particular type is available
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Differences in single and aggregated nanoparticle plasmon spectroscopy
Vibrational spectroscopy usually provides structural information averaged over many molecules. We report a larger peak position variation and reproducibly smaller FWHM of TERS spectra compared to SERS spectra indicating that the number of molecules excited in a TERS experiment is extremely low. Thus, orientational averaging effects are suppressed and micro ensembles are investigated. This is shown for a thiophenol molecule adsorbed on Au nanoplates and nanoparticles
Generalized solutions and distributional shadows for Dirac equations
We discuss the application of recent results on generalized solutions to the
Cauchy problem for hyperbolic systems to Dirac equations with external fields.
In further analysis we focus on the question of existence of associated
distributional limits and derive their explicit form in case of free Dirac
fields with regularizations of initial values corresponding to point-like
probability densities
Noise gates for decoherent quantum circuits
A major problem in exploiting microscopic systems for developing a new
technology based on the principles of Quantum Information is the influence of
noise which tends to work against the quantum features of such systems. It
becomes then crucial to understand how noise affects the evolution of quantum
circuits: several techniques have been proposed among which stochastic
differential equations (SDEs) can represent a very convenient tool. We show how
SDEs naturally map any Markovian noise into a linear operator, which we will
call a noise gate, acting on the wave function describing the state of the
circuit, and we will discuss some examples. We shall see that these gates can
be manipulated like any standard quantum gate, thus simplifying in certain
circumstances the task of computing the overall effect of the noise at each
stage of the protocol. This approach yields equivalent results to those derived
from the Lindblad equation; yet, as we show, it represents a handy and fast
tool for performing computations, and moreover, it allows for fast numerical
simulations and generalizations to non Markovian noise. In detail we review the
depolarizing channel and the generalized amplitude damping channel in terms of
this noise gate formalism and show how these techniques can be applied to any
quantum circuit.Comment: 10 pages, 4 figures: journal reference added + some typos correcte
Level of 25(OH)D Serum, Expression of Interleukin 4 and Glucocorticoid Receptor of Mononuclear Cell in Steroid Resistance Nephrotic Syndrome Children
Nephrotic syndrome (NS) is autoimmune disease and its steroid resistance status supposed correlate with 25(OH)D level and IL-4 expression. The aimed of this study was investigated 25(OH)D plasma level, IL-4 and GR expression of PBMC in steroid sensitive and resistant pediatric NS patients and the association of those parameters. 27 subjects were divided into three groups (control group, steroid resistant NS group, and steroid sensitive NS group). Peripheral blood mononuclear cells (PBMCs) isolated using Ficoll-Hypaque method. Plasma 25(OH)D level was measured using ELISA method. IL-4 and GR expression were measured using flowcytometry of PBMCs. This study showed that 25(OH)D level and GR expression were significantly different in control group compared to steroid resistant NS group (p<0.05). Plasma 25(OH)D level, IL-4 and GR expression were not correlated each other in NS patients (p>0.05). Plasma 25(OH)D level, IL-4 and GR expression were not contributed in steroid resistance in NS patients. However, GR expression has highest contribution in steroid resistance of NS patient (Wald score 1.198). Plasma 25(OH)D level and GR expression was lower in steroid resistant NS group. GR expression has a highest contribution in steroid resistance of NS patients
Does adult ADHD interact with COMT val 158 met genotype to influence working memory performance?
Peer reviewedPostprin
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Plasmon response evaluation based on image-derived arbitrary nanostructures
The optical response of realistic 3D plasmonic substrates composed of randomly shaped particles of different size and interparticle distance distributions in addition to nanometer scale surface roughness is intrinsically challenging to simulate due to computational limitations. Here, we present a Finite Element Method (FEM)-based methodology that bridges in-depth theoretical investigations and experimental optical response of plasmonic substrates composed of such silver nanoparticles. Parametrized scanning electron microscopy (SEM) images of surface enhanced Raman spectroscopy (SERS) active substrate and tip-enhanced Raman spectroscopy (TERS) probes are used to simulate the far-and near-field optical response. Far-field calculations are consistent with experimental dark field spectra and charge distribution images reveal for the first time in arbitrary structures the contributions of interparticle hybridized modes such as sub-radiant and super-radiant modes that also locally organize as basic units for Fano resonances. Near-field simulations expose the spatial position-dependent impact of hybridization on field enhancement. Simulations of representative sections of TERS tips are shown to exhibit the same unexpected coupling modes. Near-field simulations suggest that these modes can contribute up to 50% of the amplitude of the plasmon resonance at the tip apex but, interestingly, have a small effect on its frequency in the visible range. The band position is shown to be extremely sensitive to particle nanoscale roughness, highlighting the necessity to preserve detailed information at both the largest and the smallest scales. To the best of our knowledge, no currently available method enables reaching such a detailed description of large scale realistic 3D plasmonic systems
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