564 research outputs found
Scarred eigenstates for quantum cat maps of minimal periods
In this paper we construct a sequence of eigenfunctions of the ``quantum
Arnold's cat map'' that, in the semiclassical limit, show a strong scarring
phenomenon on the periodic orbits of the dynamics. More precisely, those states
have a semiclassical limit measure that is the sum of 1/2 the normalized
Lebesgue measure on the torus plus 1/2 the normalized Dirac measure
concentrated on any a priori given periodic orbit of the dynamics. It is known
(the Schnirelman theorem) that ``most'' sequences of eigenfunctions
equidistribute on the torus. The sequences we construct therefore provide an
example of an exception to this general rule. Our method of construction and
proof exploits the existence of special values of Planck's constant for which
the quantum period of the map is relatively ``short'', and a sharp control on
the evolution of coherent states up to this time scale. We also provide a
pointwise description of these states in phase space, which uncovers their
``hyperbolic'' structure in the vicinity of the fixed points and yields more
precise localization estimates.Comment: LaTeX, 49 pages, includes 10 figures. I added section 6.6. To be
published in Commun. Math. Phy
Relaxation Time of Quantized Toral Maps
We introduce the notion of the relaxation time for noisy quantum maps on the
2d-dimensional torus - a generalization of previously studied dissipation time.
We show that relaxation time is sensitive to the chaotic behavior of the
corresponding classical system if one simultaneously considers the
semiclassical limit ( -> 0) together with the limit of small noise
strength (\ep -> 0).
Focusing on quantized smooth Anosov maps, we exhibit a semiclassical regime
\hbar^{-1}\ep\hbar$ << 1,
quantum and classical relaxation times behave very differently. In the special
case of ergodic toral symplectomorphisms (generalized ``Arnold's cat'' maps),
we obtain the exact asymptotics of the quantum relaxation time and precise the
regime of correspondence between quantum and classical relaxations.Comment: LaTeX, 27 pages, former term dissipation time replaced by relaxation
time, new introduction and reference
On the mean density of complex eigenvalues for an ensemble of random matrices with prescribed singular values
Given any fixed positive semi-definite diagonal matrix
we derive the explicit formula for the density of complex eigenvalues for
random matrices of the form } where the random unitary
matrices are distributed on the group according to the Haar
measure.Comment: 10 pages, 1 figur
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
Weyl law for fat fractals
It has been conjectured that for a class of piecewise linear maps the closure
of the set of images of the discontinuity has the structure of a fat fractal,
that is, a fractal with positive measure. An example of such maps is the
sawtooth map in the elliptic regime. In this work we analyze this problem
quantum mechanically in the semiclassical regime. We find that the fraction of
states localized on the unstable set satisfies a modified fractal Weyl law,
where the exponent is given by the exterior dimension of the fat fractal.Comment: 8 pages, 4 figures, IOP forma
Fractal Weyl law behavior in an open, chaotic Hamiltonian system
We numerically show fractal Weyl law behavior in an open Hamiltonian system
that is described by a smooth potential and which supports numerous
above-barrier resonances. This behavior holds even relatively far away from the
classical limit. The complex resonance wave functions are found to be localized
on the fractal classical repeller.Comment: 4 pages, 3 figures. to appear in Phys Rev
Dissipation time and decay of correlations
We consider the effect of noise on the dynamics generated by
volume-preserving maps on a d-dimensional torus. The quantity we use to measure
the irreversibility of the dynamics is the dissipation time. We focus on the
asymptotic behaviour of this time in the limit of small noise. We derive
universal lower and upper bounds for the dissipation time in terms of various
properties of the map and its associated propagators: spectral properties,
local expansivity, and global mixing properties. We show that the dissipation
is slow for a general class of non-weakly-mixing maps; on the opposite, it is
fast for a large class of exponentially mixing systems which include uniformly
expanding maps and Anosov diffeomorphisms.Comment: 26 Pages, LaTex. Submitted to Nonlinearit
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