6,707 research outputs found
Constrained Dynamics for Quantum Mechanics I. Restricting a Particle to a Surface
We analyze constrained quantum systems where the dynamics do not preserve the
constraints. This is done in particular for the restriction of a quantum
particle in Euclidean n-space to a curved submanifold, and we propose a method
of constraining and dynamics adjustment which produces the right Hamiltonian on
the submanifold when tested on known examples. This method we hope will become
the germ of a full Dirac algorithm for quantum constraints. We take a first
step in generalising it to the situation where the constraint is a general
selfadjoint operator with some additional structures.Comment: 49 pages, TEX, input files amssym.def, amssym.te
A simple model of price formation
A simple Ising spin model which can describe the mechanism of price formation
in financial markets is proposed. In contrast to other agent-based models, the
influence does not flow inward from the surrounding neighbors to the center
site, but spreads outward from the center to the neighbors. The model thus
describes the spread of opinions among traders. It is shown via standard Monte
Carlo simulations that very simple rules lead to dynamics that duplicate those
of asset prices.Comment: Version 2: 4 pages, 4 figures; added more stringent statistical
analysis; to appear in Int. J. Modern Physics C, Vol. 13, No. 1 (2002
Glueball Spin
The spin of a glueball is usually taken as coming from the spin (and possibly
the orbital angular momentum) of its constituent gluons. In light of the
difficulties in accounting for the spin of the proton from its constituent
quarks, the spin of glueballs is reexamined. The starting point is the
fundamental QCD field angular momentum operator written in terms of the
chromoelectric and chromomagnetic fields. First, we look at the restrictions
placed on the structure of glueballs from the requirement that the QCD field
angular momentum operator should satisfy the standard commutation
relationships. This can be compared to the electromagnetic charge/monopole
system, where the quantization of the field angular momentum places
restrictions (i.e. the Dirac condition) on the system. Second, we look at the
expectation value of this operator under some simplifying assumptions.Comment: 11 pages, 0 figures; added references and some discussio
The 6-vertex model of hydrogen-bonded crystals with bond defects
It is shown that the percolation model of hydrogen-bonded crystals, which is
a 6-vertex model with bond defects, is completely equivalent with an 8-vertex
model in an external electric field. Using this equivalence we solve exactly a
particular 6-vertex model with bond defects. The general solution for the
Bethe-like lattice is also analyzed.Comment: 13 pages, 6 figures; added references for section
Scaling Analysis and Evolution Equation of the North Atlantic Oscillation Index Fluctuations
The North Atlantic Oscillation (NAO) monthly index is studied from 1825 till
2002 in order to identify the scaling ranges of its fluctuations upon different
delay times and to find out whether or not it can be regarded as a Markov
process. A Hurst rescaled range analysis and a detrended fluctuation analysis
both indicate the existence of weakly persistent long range time correlations
for the whole scaling range and time span hereby studied. Such correlations are
similar to Brownian fluctuations. The Fokker-Planck equation is derived and
Kramers-Moyal coefficients estimated from the data. They are interpreted in
terms of a drift and a diffusion coefficient as in fluid mechanics. All partial
distribution functions of the NAO monthly index fluctuations have a form close
to a Gaussian, for all time lags, in agreement with the findings of the scaling
analyses. This indicates the lack of predictive power of the present NAO
monthly index. Yet there are some deviations for large (and thus rare) events.
Whence suggestions for other measurements are made if some improved
predictability of the weather/climate in the North Atlantic is of interest. The
subsequent Langevin equation of the NAO signal fluctuations is explicitly
written in terms of the diffusion and drift parameters, and a characteristic
time scale for these is given in appendix.Comment: 6 figures, 54 refs., 16 pages; submitted to Int. J. Mod. Phys. C:
Comput. Phy
Roughness and Finite Size Effect in the NYSE Stock-Price Fluctuations
We consider the roughness properties of NYSE (New York Stock Exchange)
stock-price fluctuations. The statistical properties of the data are relatively
homogeneous within the same day but the large jumps between different days
prevent the extension of the analysis to large times. This leads to intrinsic
finite size effects which alter the apparent Hurst (H) exponent. We show, by
analytical methods, that finite size effects always lead to an enhancement of
H. We then consider the effect of fat tails on the analysis of the roughness
and show that the finite size effects are strongly enhanced by the fat tails.
The non stationarity of the stock price dynamics also enhances the finite size
effects which, in principle, can become important even in the asymptotic
regime. We then compute the Hurst exponent for a set of stocks of the NYSE and
argue that the interpretation of the value of H is highly ambiguous in view of
the above results. Finally we propose an alternative determination of the
roughness in terms of the fluctuations from moving averages with variable
characteristic times. This permits to eliminate most of the previous problems
and to characterize the roughness in useful way. In particular this approach
corresponds to the automatic elimination of trends at any scale.Comment: 13 pages, 11 fugure
Distributive Justice for Volunteers: Extrinsic Outcome Distribution Matters
Volunteer organizations continue to suffer from turnover; the current volunteer rate is the lowest since 2002. Distributive justice, satisfaction, and extrinsic outcome importance were examined as influences of volunteer intention to quit. Survey results from 294 volunteers revealed that those who perceived less than fair distribution of extrinsic outcomes experienced heightened intention to quit compared to those who perceived fair distribution. Overall satisfaction partially mediated this relationship. We explored the potential moderating role of volunteersâ assessment of the importance of extrinsic outcomes on the overall mediated relationship
Mineralogical evidence for multiple dust sources in an early Triassic loessite.
Loessite present in a borehole into the Smith Bank Formation (early Triassic age, Central North Sea) differentiates five coeval source terranes for aerosol dust, three long distance sources and two local sources. All were active immediately following the end Permian mass extinction. Long distance sources are sedimentary, basic magmatic and acidâintermediate volcanic. Although predominantly siltâsized and dominated by quartz with subordinate feldspars, muscovite and illite, evidence of basic and acidâintermediate magmatic/volcanic sources are pervasive. Baddeleyite is diagnostic of basic magmatism, an origin supported by enrichment of plagioclase relative to potassium feldspar. Deduction of acidâintermediate volcanism comes from the collective occurrence of irregular geometry quartz, volcanic shards, Tiâmineralization, euhedral biotite, sanidine, the coâoccurrence of apatite and zircon, and the common occurrence of a tosuditic clay mineral. The tosuditic phase occurs as an unusual diagenetic dioctahedral chlorite/smectite formed at low temperature (<45°C), during very shallow burial by the decomposition of unstable rhyoâdacitic and andesitic grains in alkaline pore water from an adjacent lake that yielded pore fluids with a high Al:Si ratio. The Siberian Traps large igneous province is the likely source terrane for the magmatic and volcanic silt. Locally sourced clay pellets and kaolinite booklets formed from aeolian erosion of an adjacent, periodically desiccated lakeâfloor and a kaolinitic regolith, respectively. Inference of a prolonged harsh, arid climate leaves no evidence of any periods of sustained humidity or climatic fluctuation, such as pedogenesis. The association between the end Permian mass extinction, emplacement and aeolian erosion of the Siberian Traps large igneous province, and location of the Smith Bank Formation in a large lacustrine endorheic basin, combine to preserve a record of prolonged harsh climate in the early Triassic
Exact Results for the Roughness of a Finite Size Random Walk
We consider the role of finite size effects on the value of the effective
Hurst exponent H. This problem is motivated by the properties of the high
frequency daily stock-prices. For a finite size random walk we derive some
exact results based on Spitzer's identity. The conclusion is that finite size
effects strongly enhance the value of H and the convergency to the asymptotic
value (H=1/2) is rather slow. This result has a series of conceptual and
practical implication which we discuss.Comment: 5 pages, 3 figure
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