151 research outputs found
Complex paths for regular-to-chaotic tunneling rates
In generic Hamiltonian systems tori of regular motion are dynamically
separated from regions of chaotic motion in phase space. Quantum mechanically
these phase-space regions are coupled by dynamical tunneling. We introduce a
semiclassical approach based on complex paths for the prediction of dynamical
tunneling rates from regular tori to the chaotic region. This approach is
demonstrated for the standard map giving excellent agreement with numerically
determined tunneling rates.Comment: 5 pages, 4 figure
Virtual turning points and bifurcation of Stokes curves for higher order ordinary differential equations
For a higher order linear ordinary differential operator P, its Stokes curve
bifurcates in general when it hits another turning point of P. This phenomenon
is most neatly understandable by taking into account Stokes curves emanating
from virtual turning points, together with those from ordinary turning points.
This understanding of the bifurcation of a Stokes curve plays an important role
in resolving a paradox recently found in the Noumi-Yamada system, a system of
linear differential equations associated with the fourth Painleve equation.Comment: 7 pages, 4 figure
Semiclassical Description of Tunneling in Mixed Systems: The Case of the Annular Billiard
We study quantum-mechanical tunneling between symmetry-related pairs of
regular phase space regions that are separated by a chaotic layer. We consider
the annular billiard, and use scattering theory to relate the splitting of
quasi-degenerate states quantized on the two regular regions to specific paths
connecting them. The tunneling amplitudes involved are given a semiclassical
interpretation by extending the billiard boundaries to complex space and
generalizing specular reflection to complex rays. We give analytical
expressions for the splittings, and show that the dominant contributions come
from {\em chaos-assisted}\/ paths that tunnel into and out of the chaotic
layer.Comment: 4 pages, uuencoded postscript file, replaces a corrupted versio
Spectral properties of quantized barrier billiards
The properties of energy levels in a family of classically pseudointegrable
systems, the barrier billiards, are investigated. An extensive numerical study
of nearest-neighbor spacing distributions, next-to-nearest spacing
distributions, number variances, spectral form factors, and the level dynamics
is carried out. For a special member of the billiard family, the form factor is
calculated analytically for small arguments in the diagonal approximation. All
results together are consistent with the so-called semi-Poisson statistics.Comment: 8 pages, 9 figure
Evanescent wave approach to diffractive phenomena in convex billiards with corners
What we are going to call in this paper "diffractive phenomena" in billiards
is far from being deeply understood. These are sorts of singularities that, for
example, some kind of corners introduce in the energy eigenfunctions. In this
paper we use the well-known scaling quantization procedure to study them. We
show how the scaling method can be applied to convex billiards with corners,
taking into account the strong diffraction at them and the techniques needed to
solve their Helmholtz equation. As an example we study a classically
pseudointegrable billiard, the truncated triangle. Then we focus our attention
on the spectral behavior. A numerical study of the statistical properties of
high-lying energy levels is carried out. It is found that all computed
statistical quantities are roughly described by the so-called semi-Poisson
statistics, but it is not clear whether the semi-Poisson statistics is the
correct one in the semiclassical limit.Comment: 7 pages, 8 figure
Semiclassical transmission across transition states
It is shown that the probability of quantum-mechanical transmission across a
phase space bottleneck can be compactly approximated using an operator derived
from a complex Poincar\'e return map. This result uniformly incorporates
tunnelling effects with classically-allowed transmission and generalises a
result previously derived for a classically small region of phase space.Comment: To appear in Nonlinearit
Level statistics and eigenfunctions of pseudointegrable systems: dependence on energy and genus number
We study the level statistics (second half moment and rigidity
) and the eigenfunctions of pseudointegrable systems with rough
boundaries of different genus numbers . We find that the levels form energy
intervals with a characteristic behavior of the level statistics and the
eigenfunctions in each interval. At low enough energies, the boundary roughness
is not resolved and accordingly, the eigenfunctions are quite regular functions
and the level statistics shows Poisson-like behavior. At higher energies, the
level statistics of most systems moves from Poisson-like towards Wigner-like
behavior with increasing . Investigating the wavefunctions, we find many
chaotic functions that can be described as a random superposition of regular
wavefunctions. The amplitude distribution of these chaotic functions
was found to be Gaussian with the typical value of the localization volume
. For systems with periodic boundaries we find
several additional energy regimes, where is relatively close to the
Poisson-limit. In these regimes, the eigenfunctions are either regular or
localized functions, where is close to the distribution of a sine or
cosine function in the first case and strongly peaked in the second case. Also
an interesting intermediate case between chaotic and localized eigenfunctions
appears
Slow relaxation in weakly open vertex-splitting rational polygons
The problem of splitting effects by vertex angles is discussed for
nonintegrable rational polygonal billiards. A statistical analysis of the decay
dynamics in weakly open polygons is given through the orbit survival
probability. Two distinct channels for the late-time relaxation of type
1/t^delta are established. The primary channel, associated with the universal
relaxation of ''regular'' orbits, with delta = 1, is common for both the closed
and open, chaotic and nonchaotic billiards. The secondary relaxation channel,
with delta > 1, is originated from ''irregular'' orbits and is due to the
rationality of vertices.Comment: Key words: Dynamics of systems of particles, control of chaos,
channels of relaxation. 21 pages, 4 figure
Periodic Orbits and Spectral Statistics of Pseudointegrable Billiards
We demonstrate for a generic pseudointegrable billiard that the number of
periodic orbit families with length less than increases as , where is a constant and is the average area occupied by these families. We also find that
increases with before saturating. Finally, we show
that periodic orbits provide a good estimate of spectral correlations in the
corresponding quantum spectrum and thus conclude that diffraction effects are
not as significant in such studies.Comment: 13 pages in RevTex including 5 figure
Scale Anomaly and Quantum Chaos in the Billiards with Pointlike Scatterers
We argue that the random-matrix like energy spectra found in pseudointegrable
billiards with pointlike scatterers are related to the quantum violation of
scale invariance of classical analogue system. It is shown that the behavior of
the running coupling constant explains the key characteristics of the level
statistics of pseudointegrable billiards.Comment: 10 pages, RevTex file, uuencode
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