1,083 research outputs found
Wavelet representations and Fock space on positive matrices
We show that every biorthogonal wavelet determines a representation by
operators on Hilbert space satisfying simple identities, which captures the
established relationship between orthogonal wavelets and Cuntz-algebra
representations in that special case. Each of these representations is shown to
have tractable finite-dimensional co-invariant doubly-cyclic subspaces.
Further, motivated by these representations, we introduce a general Fock-space
Hilbert space construction which yields creation operators containing the
Cuntz--Toeplitz isometries as a special case.Comment: 32 pages, LaTeX ("amsart" document class), one EPS graphic file used
for shading, accepted March 2002 for J. Funct. Ana
A Detailed Monte-Carlo Simulation for the Belle TOF System
We have developed a detailed Monte Carlo simulation program for the Belle TOF
system. Based on GEANT simulation, it takes account of all physics processes in
the TOF scintillation counters and readout electronics. The simulation
reproduces very well the performance of the Belle TOF system, including the
dE/dx response, the time walk effect, the time resolution, and the hit
efficiency due to beam background. In this report, we will describe the Belle
TOF simulation program in detail.Comment: To be submitted to NI
Antiferromagnetic Domains and Superconductivity in UPt3
We explore the response of an unconventional superconductor to spatially
inhomogeneous antiferromagnetism (SIAFM). Symmetry allows the superconducting
order parameter in the E-representation models for UPt3 to couple directly to
the AFM order parameter. The Ginzburg-Landau equations for coupled
superconductivity and SIAFM are solved numerically for two possible SIAFM
configurations: (I) abutting antiferromagnetic domains of uniform size, and
(II) quenched random disorder of `nanodomains' in a uniform AFM background. We
discuss the contributions to the free energy, specific heat, and order
parameter for these models. Neither model provides a satisfactory account of
experiment, but results from the two models differ significantly. Our results
demonstrate that the response of an E_{2u} superconductor to SIAFM is strongly
dependent on the spatial dependence of AFM order; no conclusion can be drawn
regarding the compatibility of E_{2u} superconductivity with UPt3 that is
independent of assumptions on the spatial dependence of AFMComment: 12 pages, 13 figures, to appear in Phys. Rev.
OUTLIERS DETECTION BY RANSAC ALGORITHM IN THE TRANSFORMATION OF 2D COORDINATE FRAMES
Over the years there have been a number of different computational methods that allow for the identification of outliers. Methods for robust estimation are known in the set of M-estimates methods (derived from the method of Maximum Likelihood Estimation) or in the set of R-estimation methods (robust estimation based on the application of some rank test). There are also algorithms that are not classified in any of these groups but these methods are also resistant to gross errors, for example, in M-split estimation. Another proposal, which can be used to detect outliers in the process of transformation of coordinates, where the coordinates of some points may be affected by gross errors, can be a method called RANSAC algorithm (Random Sample and Consensus). The authors present a study that was performed in the process of 2D transformation parameter estimation using RANSAC algorithm to detect points that have coordinates with outliers. The calculations were performed in three scenarios on the real geodetic network. Selected coordinates were burdened with simulated values of errors to confirm the efficiency of the proposed method
Boundary Effects on Dynamic Behavior of Josephson-Junction Arrays
The boundary effects on the current-voltage characteristics in
two-dimensional arrays of resistively shunted Josephson junctions are examined.
In particular, we consider both the conventional boundary conditions (CBC) and
the fluctuating twist boundary conditions (FTBC), and make comparison of the
obtained results. It is observed that the CBC, which have been widely adopted
in existing simulations, may give a problem in scaling, arising from rather
large boundary effects; the FTBC in general turn out to be effective in
reducing the finite-size effects, yielding results with good scaling behavior.
To resolve the discrepancy between the two boundary conditions, we propose that
the proper scaling in the CBC should be performed with the boundary data
discarded: This is shown to give results which indeed scale well and are the
same as those from the FTBC.Comment: RevTex, Final version to appear in Phys. Rev.
Neutrino Mass from R-parity Violation in Split Supersymmetry
We investigate how the observed neutrino data can be accommodated by R-parity
violation in Split Supersymmetry. The atmospheric neutrino mass and mixing are
explained by the bilinear parameters inducing the neutrino-neutralino
mixing as in the usual low-energy supersymmetry. Among various one-loop
corrections, only the quark-squark exchanging diagrams involving the order-one
trilinear couplings can generate the solar neutrino mass
and mixing if the scalar mass is not larger than GeV. This scheme
requires an unpleasant hierarchical structure of the couplings, e.g.,
, and . On the other hand, the model has a distinct collider
signature of the lightest neutralino which can decay only to the final states,
and , arising from the bilinear mixing. Thus, the
measurement of the ratio; would provide a clean probe of the small reactor and
large atmospheric neutrino mixing angles as far as the neutralino mass is
larger than 62 GeV.Comment: 10 pages, 3 figures, version submitted to JHE
Dynamic instabilities induced by asymmetric influence: Prisoners' dilemma game on small-world networks
A two-dimensional small-world type network, subject to spatial prisoners'
dilemma dynamics and containing an influential node defined as a special node
with a finite density of directed random links to the other nodes in the
network, is numerically investigated. It is shown that the degree of
cooperation does not remain at a steady state level but displays a punctuated
equilibrium type behavior manifested by the existence of sudden breakdowns of
cooperation. The breakdown of cooperation is linked to an imitation of a
successful selfish strategy of the influential node. It is also found that
while the breakdown of cooperation occurs suddenly, the recovery of it requires
longer time. This recovery time may, depending on the degree of steady state
cooperation, either increase or decrease with an increasing number of long
range connections.Comment: 5 pages, 6 figure
Steady water waves with multiple critical layers: interior dynamics
We study small-amplitude steady water waves with multiple critical layers.
Those are rotational two-dimensional gravity-waves propagating over a perfect
fluid of finite depth. It is found that arbitrarily many critical layers with
cat's-eye vortices are possible, with different structure at different levels
within the fluid. The corresponding vorticity depends linearly on the stream
function.Comment: 14 pages, 3 figures. As accepted for publication in J. Math. Fluid
Mec
Cognitive Ability and Cardiovascular Control in Intellectually and Developmentally Disabled People
Earlier, we examined positive effects of hyperoxic air on the cognitive ability of intellectually
and developmentally disabled people (IDDP). In this study, correlation between cognitive
performance in the visual matching task and heart rate (HR) was investigated under normal
air conditions. Eighteen men (mean age 28.7 ± 5.0 year) and 22 women (mean age 35.5 ± 6.9
year) with an assessed disability level of 2.3 ± 0.6 participated. The experiment consisted of
three phases, a total of 7 min, including the rest (3 min), control (2 min), and visual matching
task 2 min phases. The HR in visual matching task phase increased, compared to those in the
rest and control phases. The cognitive ability in the visual matching task correlated with the
HR values; the response time showed a negative correlation with HR, while the accuracy rate
showed a positive correlation. Thus, adaptive changes in cardiovascular regulation probably
related to cognitive efforts and emotional excitation should be considered a noticeable factor
influencing brain supply with oxygen in IDDP (similarly to healthy people). The result of this
study agrees with the earlier obtained indications that hyperoxic air can positively affect the
cognitive performance in IDDP.Раніше ми вивчали позитивні впливи повітря, збагаченого
киснем, на когнітивні здатності людей з недостатнім інтелектуальним розвитком (НІР). У нашій роботі ми досліджували кореляцію між показниками когнітивної активності в
тесті візуальної відповідності та частотою серцевих скорочень (ЧСС) у таких суб’єктів в умовах дихання нормальним
повітрям. У тестах брали участь 18 чоловіків (середній вік
28.7 ± 5.0 року) та 22 жінки (35.5 ± 6.9 року) з оцінкою рівня
інтелектуального розвитку 2.3 ± 0.6. Експеримент (загальна
тривалість 7 хв) складався з трьох фаз: стан розслаблення
(3 хв), контроль (2 хв) та тест візуальної відповідності
(2 хв). Величини ЧСС у межах цього тесту порівняно з величинами в умовах розслаблення й контролю зростали. Показники когнітивних здібностей корелювали з величинами
ЧСС; кореляція часу відповіді була негативною, а точності відповіді – позитивною. Отже, адаптивні зміни регуляції
серцево-судинної системи, мабуть, пов’язані з когнітивними
зусиллями та емоційним збудженням, є істотним фактором,
який впливає на постачання мозку киснем у людей із НІР
(як і у здорових людей). Результати нашої роботи узгоджуються з отриманими раніше свідоцтвами про те, що дихання
повітрям, збагаченим киснем, позитивно впливає на когнітивні можливості людей із НІР
Long-Time Behavior of Macroscopic Quantum Systems: Commentary Accompanying the English Translation of John von Neumann's 1929 Article on the Quantum Ergodic Theorem
The renewed interest in the foundations of quantum statistical mechanics in
recent years has led us to study John von Neumann's 1929 article on the quantum
ergodic theorem. We have found this almost forgotten article, which until now
has been available only in German, to be a treasure chest, and to be much
misunderstood. In it, von Neumann studied the long-time behavior of macroscopic
quantum systems. While one of the two theorems announced in his title, the one
he calls the "quantum H-theorem", is actually a much weaker statement than
Boltzmann's classical H-theorem, the other theorem, which he calls the "quantum
ergodic theorem", is a beautiful and very non-trivial result. It expresses a
fact we call "normal typicality" and can be summarized as follows: For a
"typical" finite family of commuting macroscopic observables, every initial
wave function from a micro-canonical energy shell so evolves that for
most times in the long run, the joint probability distribution of these
observables obtained from is close to their micro-canonical
distribution.Comment: 34 pages LaTeX, no figures; v2: minor improvements and additions. The
English translation of von Neumann's article is available as arXiv:1003.213
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