3,864 research outputs found
Ozone reference models for the middle atmosphere (new CIRA)
Models of ozone vertical structure were generated that were based on multiple data sets from satellites. The very good absolute accuracy of the individual data sets allowed the data to be directly combined to generate these models. The data used for generation of these models are from some of the most recent satellite measurements over the period 1978 to 1983. A discussion is provided of validation and error analyses of these data sets. Also, inconsistencies in data sets brought about by temporal variations or other factors are indicated. The models cover the pressure range from from 20 to 0.003 mb (25 to 90 km). The models for pressures less than 0.5 mb represent only the day side and are only provisional since there was limited longitudinal coverage at these levels. The models start near 25 km in accord with previous COSPAR international reference atmosphere (CIRA) models. Models are also provided of ozone mixing ratio as a function of height. The monthly standard deviation and interannual variations relative to zonal means are also provided. In addition to the models of monthly latitudinal variations in vertical structure based on satellite measurements, monthly models of total column ozone and its characteristic variability as a function of latitude based on four years of Nimbus 7 measurements, models of the relationship between vertical structure and total column ozone, and a midlatitude annual mean model are incorporated in this set of ozone reference atmospheres. Various systematic variations are discussed including the annual, semiannual, and quasibiennial oscillations, and diurnal, longitudinal, and response to solar activity variations
Localization and its consequences for quantum walk algorithms and quantum communication
The exponential speed-up of quantum walks on certain graphs, relative to
classical particles diffusing on the same graph, is a striking observation. It
has suggested the possibility of new fast quantum algorithms. We point out here
that quantum mechanics can also lead, through the phenomenon of localization,
to exponential suppression of motion on these graphs (even in the absence of
decoherence). In fact, for physical embodiments of graphs, this will be the
generic behaviour. It also has implications for proposals for using spin
networks, including spin chains, as quantum communication channels.Comment: 4 pages, 1 eps figure. Updated references and cosmetic changes for v
Spectral Statistics of "Cellular" Billiards
For a bounded planar domain whose boundary contains a number of
flat pieces we consider a family of non-symmetric billiards
constructed by patching several copies of along 's. It is
demonstrated that the length spectrum of the periodic orbits in is
degenerate with the multiplicities determined by a matrix group . We study
the energy spectrum of the corresponding quantum billiard problem in
and show that it can be split in a number of uncorrelated subspectra
corresponding to a set of irreducible representations of . Assuming
that the classical dynamics in are chaotic, we derive a
semiclassical trace formula for each spectral component and show that their
energy level statistics are the same as in standard Random Matrix ensembles.
Depending on whether is real, pseudo-real or complex, the spectrum
has either Gaussian Orthogonal, Gaussian Symplectic or Gaussian Unitary types
of statistics, respectively.Comment: 18 pages, 4 figure
On the Nodal Count Statistics for Separable Systems in any Dimension
We consider the statistics of the number of nodal domains aka nodal counts
for eigenfunctions of separable wave equations in arbitrary dimension. We give
an explicit expression for the limiting distribution of normalised nodal counts
and analyse some of its universal properties. Our results are illustrated by
detailed discussion of simple examples and numerical nodal count distributions.Comment: 21 pages, 4 figure
On the resonance eigenstates of an open quantum baker map
We study the resonance eigenstates of a particular quantization of the open
baker map. For any admissible value of Planck's constant, the corresponding
quantum map is a subunitary matrix, and the nonzero component of its spectrum
is contained inside an annulus in the complex plane, . We consider semiclassical sequences of eigenstates, such that the
moduli of their eigenvalues converge to a fixed radius . We prove that, if
the moduli converge to , then the sequence of eigenstates
converges to a fixed phase space measure . The same holds for
sequences with eigenvalue moduli converging to , with a different
limit measure . Both these limiting measures are supported on
fractal sets, which are trapped sets of the classical dynamics. For a general
radius , we identify families of eigenstates with
precise self-similar properties.Comment: 32 pages, 2 figure
Signatures of homoclinic motion in quantum chaos
Homoclinic motion plays a key role in the organization of classical chaos in
Hamiltonian systems. In this Letter, we show that it also imprints a clear
signature in the corresponding quantum spectra. By numerically studying the
fluctuations of the widths of wavefunctions localized along periodic orbits we
reveal the existence of an oscillatory behavior, that is explained solely in
terms of the primary homoclinic motion. Furthermore, our results indicate that
it survives the semiclassical limit.Comment: 5 pages, 4 figure
Complex System Governance as a Framework for Asset Management
Complex system governance (CSG) is an emerging field encompassing a framework for system performance improvement through the purposeful design, execution, and evolution of essential metasystem functions. The goal of this study was to understand how the domain of asset management (AsM) can leverage the capabilities of CSG. AsM emerged from engineering as a structured approach to organizing complex organizations to realize the value of assets while balancing performance, risks, costs, and other opportunities. However, there remains a scarcity of literature discussing the potential relationship between AsM and CSG. To initiate the closure of this gap, this research reviews the basics of AsM and the methods associated with realizing the value of assets. Then, the basics of CSG are provided along with how CSG might be leveraged to support AsM. We conclude the research with the implications for AsM and suggested future research
Entanglement in Quantum Spin Chains, Symmetry Classes of Random Matrices, and Conformal Field Theory
We compute the entropy of entanglement between the first spins and the
rest of the system in the ground states of a general class of quantum
spin-chains. We show that under certain conditions the entropy can be expressed
in terms of averages over ensembles of random matrices. These averages can be
evaluated, allowing us to prove that at critical points the entropy grows like
as , where and are determined explicitly. In an important class of systems,
is equal to one-third of the central charge of an associated Virasoro algebra.
Our expression for therefore provides an explicit formula for the
central charge.Comment: 4 page
Rate of convergence of linear functions on the unitary group
We study the rate of convergence to a normal random variable of the real and
imaginary parts of Tr(AU), where U is an N x N random unitary matrix and A is a
deterministic complex matrix. We show that the rate of convergence is O(N^{-2 +
b}), with 0 <= b < 1, depending only on the asymptotic behaviour of the
singular values of A; for example, if the singular values are non-degenerate,
different from zero and O(1) as N -> infinity, then b=0. The proof uses a
Berry-Esse'en inequality for linear combinations of eigenvalues of random
unitary, matrices, and so appropriate for strongly dependent random variables.Comment: 34 pages, 1 figure; corrected typos, added remark 3.3, added 3
reference
Systemic Intervention for Complex System Governance Development
This paper explores the issues related to systemic intervention for Complex System Governance (CSG) development. Systemic intervention seeks to intentionally engage a system to influence trajectory or outcomes. CSG is an emerging field focused on the design, execution, and evolution of the functions necessary to provide continued system performance (stability) in the midst of incessant turbulence and increasing complexity. Integral to this field is the necessity to ‘intervene’ in a complex system to enhance system behavior, structure, or performance. Arguably, system interventions have an unremarkable record of success, ranging from declared success in improving a situation (system) to abysmal failure (doing more harm than good).
However, little emphasis has been placed on a more rigorous exploration of the nature of systemic intervention as it influences our ability to more effectively enact change in complex systems. To address this sparse accounting in the literature, following an essential introduction to Complex System Governance, this paper pursues three primary objectives. First the nature of ‘systemic intervention’ is examined. Second, the different forms and roles in systemic intervention for complex systems are explored. Third, an approach for beginning an intervention in CSG (CSG Entry) is examined for broader implications for engaging complex systems and problems. The paper concludes with critical issues and suggests considerations for more effective systemic intervention
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