6,322 research outputs found
Density of States of Quantum Spin Systems from Isotropic Entanglement
We propose a method which we call "Isotropic Entanglement" (IE), that
predicts the eigenvalue distribution of quantum many body (spin) systems (QMBS)
with generic interactions. We interpolate between two known approximations by
matching fourth moments. Though, such problems can be QMA-complete, our
examples show that IE provides an accurate picture of the spectra well beyond
what one expects from the first four moments alone. We further show that the
interpolation is universal, i.e., independent of the choice of local terms.Comment: 4+ pages, content is as in the published versio
Preliminary results of noble metal thermocouple research program, 1000 - 2000 C
Noble metal thermocouple research involving combustion gase
The Stochastically Subordinated Log Normal Process Applied To Financial Time Series And Option Pricing
The method of stochastic subordination, or random time indexing, has been recently applied to Wiener process price processes to model financial returns. Previous emphasis in stochastic subordination models has involved explicitly identifying the subordinating process with an observable quantity such as number of trades. In contrast, the approach taken here does not depend on the specific identification of the subordinated time variable, but rather assumes a class of time models and estimates parameters from data. In addition, a simple Markov process is proposed for the characteristic parameter of the subordinating distribution to explain the significant autocorrelation of the squared returns. It is shown in particular, that the proposed model, while containing only a few more parameters than the commonly used Wiener process models, fits selected fmancial time series particularly well, characterising the autocorrelation structure and heavy tails, as well as preserving the desirable self-similarity structure present in popular chaos-theoretic models, and the existence of risk-neutral measures necessary for objective derivative valuation
Universality in Systems with Power-Law Memory and Fractional Dynamics
There are a few different ways to extend regular nonlinear dynamical systems
by introducing power-law memory or considering fractional
differential/difference equations instead of integer ones. This extension
allows the introduction of families of nonlinear dynamical systems converging
to regular systems in the case of an integer power-law memory or an integer
order of derivatives/differences. The examples considered in this review
include the logistic family of maps (converging in the case of the first order
difference to the regular logistic map), the universal family of maps, and the
standard family of maps (the latter two converging, in the case of the second
difference, to the regular universal and standard maps). Correspondingly, the
phenomenon of transition to chaos through a period doubling cascade of
bifurcations in regular nonlinear systems, known as "universality", can be
extended to fractional maps, which are maps with power-/asymptotically
power-law memory. The new features of universality, including cascades of
bifurcations on single trajectories, which appear in fractional (with memory)
nonlinear dynamical systems are the main subject of this review.Comment: 23 pages 7 Figures, to appear Oct 28 201
Report of conference evaluation committee
A general classification is made of a number of approaches used for the prediction of turbulent shear flows. The sensitivity of these prediction methods to parameter values and initial data are discussed in terms of variable density, pressure fluctuation, gradient diffusion, low Reynolds number, and influence of geometry
Probability of local bifurcation type from a fixed point: A random matrix perspective
Results regarding probable bifurcations from fixed points are presented in
the context of general dynamical systems (real, random matrices), time-delay
dynamical systems (companion matrices), and a set of mappings known for their
properties as universal approximators (neural networks). The eigenvalue spectra
is considered both numerically and analytically using previous work of Edelman
et. al. Based upon the numerical evidence, various conjectures are presented.
The conclusion is that in many circumstances, most bifurcations from fixed
points of large dynamical systems will be due to complex eigenvalues.
Nevertheless, surprising situations are presented for which the aforementioned
conclusion is not general, e.g. real random matrices with Gaussian elements
with a large positive mean and finite variance.Comment: 21 pages, 19 figure
Investing in our Children
As adults we are responsible for meeting the needs of children. It is our moral obligation to help children survive, thrive and grow into self-sufficient adults - caring parents, competent workers with a fair opportunity for success and fulfillment, and responsible citizens. Adult society must provide children with food, shelter, medical care, and an environment that is both secure and stimulating. Children need our assistance to obtain the decent education they deserve, to prepare to compete in the job market, to make sound decisions about when to become parents, to feel valued and valuable, and to feel that they have a fair chance to succeed
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