124 research outputs found
Permanent magnetic moment in mesoscopic metals with spin-orbit interaction
We argue that at zero temperature an isolated metal particle (or an AB ring)
with spin-orbit interaction and odd number of electrons will have a permanent
magnetic moment, even in zero magnetic field (flux). In a zero-field-cooled
state both the direction and the magnitude of the moment varies from particle
to particle and averages to zero. In a field-cooled state it averages to . We argue that the permanent moment is due to an
uncompensated electron in the last occupied (Fermi) level. We introduce an
effective single-electron Hamiltonian which accounts for spin-orbit coupling.Comment: 4 page
Elliptic billiard - a non-trivial integrable system
We investigate the semiclassical energy spectrum of quantum elliptic
billiard. The nearest neighbor spacing distribution, level number variance and
spectral rigidity support the notion that the elliptic billiard is a generic
integrable system. However, second order statistics exhibit a novel property of
long-range oscillations. Classical simulation shows that all the periodic
orbits except two are not isolated. In Fourier analysis of the spectrum, all
the peaks correspond to periodic orbits. The two isolated periodic orbits have
small contribution to the fluctuation of level density, while non-isolated
periodic orbits have the main contribution. The heights of the majority of the
peaks match our semiclassical theory except for type-O periodic orbits.
Elliptic billiard is a nontrivial integrable system that will enrich our
understanding of integrable systems.Comment: 5 pages, 6 figure
Quantum absorption in small metal particles
We evaluate the electric dipole absorption in small metal particles in a
longitudinal electric field taking into account the Fermi-Thomas screening.
When either the level broadening or the frequency of the field are larger than
the mean energy-level spacing, the main contribution to absorption is
classical, with quantum corrections. When both the broadening and the frequency
are smaller than the mean level spacing, the absorption is manifestly quantum
and can be understood in terms of the two-level system.Comment: 5 pages revte
A Model for Stock Returns and Volatility
We prove that Student's t-distribution provides one of the better fits to
returns of S&P component stocks and the generalized inverse gamma distribution
best fits VIX and VXO volatility data. We further argue that a more accurate
measure of the volatility may be possible based on the fact that stock returns
can be understood as the product distribution of the volatility and normal
distributions. We find Brown noise in VIX and VXO time series and explain the
mean and the variance of the relaxation times on approach to the steady-state
distribution.Comment: 17 pages, 30 figures, 2 table
On absence of steady state in the Bouchaud-M\'ezard network model
In the limit of infinite number of nodes (agents), the It\^o-reduced
Bouchaud-M\'ezard network model of economic exchange has a time-independent
mean and a steady-state inverse gamma distribution. We show that for a finite
number of nodes the mean is actually distributed as a time-dependent lognormal
and inverse gamma is quasi-stationary, with the time-dependent scale parameter.Comment: 6 pages, 4 figure
Global Level Number Variance in Integrable Systems
We study previously un-researched second order statistics - correlation
function of spectral staircase and global level number variance - in generic
integrable systems with no extra degeneracies. We show that the global level
number variance oscillates persistently around the saturation spectral
rigidity. Unlike other second order statistics - including correlation function
of spectral staircase - which are calculated over energy scales much smaller
than the running spectral energy, these oscillations cannot be explained within
the diagonal approximation framework of the periodic orbit theory. We give
detailed numerical illustration of our results using four integrable systems:
rectangular billiard, modified Kepler problem, circular billiard and elliptic
billiard.Comment: 5 pages, 3 figure
Classical absorption in small metal particles and thin films
We study the electric dipole absorption in small metal particles and thin
films in a longitudnal electric field. In diffusive approximation, we give both
the phenomenological and microscopic derivations with the account for
Thomas-Fermi screening and Drude relaxation.Comment: 11 page
Spectral and Parametric Averaging for Integrable Systems
We analyze two theoretical approaches to ensemble averaging for integrable
systems in quantum chaos - spectral averaging and parametric averaging. For
spectral averaging, we introduce a new procedure - rescaled spectral averaging.
Unlike traditional spectral averaging, it can describe the correlation function
of spectral staircase and produce persistent oscillations of the interval level
number variance. Parametric averaging, while not as accurate as rescaled
spectral averaging for the correlation function of spectral staircase and
interval level number variance, can also produce persistent oscillations of the
global level number variance and better describes saturation level rigidity as
a function of the running energy. Overall, it is the most reliable method for a
wide range of statistics.Comment: 7 pages, 7 figure
Implied and Realized Volatility: A Study of the Ratio Distribution
We analyze correlations between squared volatility indices, VIX and VXO, and
realized variances -- the known one, for the current month, and the predicted
one, for the following month. We show that the ratio of the two is best fitted
by a Beta Prime distribution, whose shape parameters depend strongly on which
of the two months is used.Comment: 9 pages, 10 figures, 9 table
The Absence Of Saturation Of The Level Number Variance In A Rectangular Box
The variance of the number of levels in an energy interval around a level
with large quantum numbers (semiclassical quantization) is studied for a
particle in a rectangular box. Sampling involves changing the ratio of the
rectangle's sides while keeping the area constant. For sufficiently narrow
intervals, one finds the usual linear growth with the width of the interval.
For wider intervals, the variance undergoes large, non-decaying oscillations
around what is expected to be the saturation value. These oscillations can be
explained as a superposition of just a few harmonics that correspond to the
shortest periodic orbits in the rectangle. The analytical and numerical results
are in excellent agreement.Comment: 15 pages, 4 figure
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