98 research outputs found
Fractal Noise in Quantum Ballistic and Diffusive Lattice Systems
We demonstrate fractal noise in the quantum evolution of wave packets moving
either ballistically or diffusively in periodic and quasiperiodic tight-binding
lattices, respectively. For the ballistic case with various initial
superpositions we obtain a space-time self-affine fractal which
verify the predictions by Berry for "a particle in a box", in addition to
quantum revivals. For the diffusive case self-similar fractal evolution is also
obtained. These universal fractal features of quantum theory might be useful in
the field of quantum information, for creating efficient quantum algorithms,
and can possibly be detectable in scattering from nanostructures.Comment: 9 pages, 8 postscript figure
Elementary fractal geometry. Networks and carpets involving irrational rotations
Self-similar sets with open set condition, the linear objects of fractal
geometry, have been considered mainly for crystallographic data. Here we
introduce new symmetry classes in the plane, based on rotation by irrational
angles. Examples without characteristic directions, with strong connectedness
and small complexity were found in a computer-assisted search. They are
surprising since the rotations are given by rational matrices, and the proof of
the open set condition usually requires integer data. We develop a
classification of self-similar sets by symmetry class and algebraic numbers.
Examples are given for various quadratic number fields. .Comment: 29 pages, 12 figure
Hausdorff dimension of boundaries of self-affine tiles in R^n
We present a new method to calculate the Hausdorff dimension of a certain
class of fractals: boundaries of self-affine tiles. Among the interesting
aspects are that even if the affine contraction underlying the iterated
function system is not conjugated to a similarity we obtain an upper- and
lower-bounds for its Hausdorff dimension. In fact, we obtain the exact value
for the dimension if the moduli of the eigenvalues of the underlying affine
contraction are all equal (this includes Jordan blocks). The tiles we discuss
play an important role in the theory of wavelets. We calculate the dimension
for a number of examples
Expanding measures: Random walks and rigidity on homogeneous spaces
Let be a real Lie group, a lattice and a connected
semisimple subgroup without compact factors and with finite center. We define
the notion of -expanding measures on and, applying recent work of
Eskin-Lindenstrauss, prove that -stationary probability measures on
are homogeneous. Transferring a construction by Benoist-Quint and
drawing on ideas of Eskin-Mirzakhani-Mohammadi, we construct Lyapunov/Margulis
functions to show that -expanding random walks on satisfy a
recurrence condition and that homogeneous subspaces are repelling. Combined
with a countability result, this allows us to prove equidistribution of
trajectories in for -expanding random walks and to obtain orbit
closure descriptions. Finally, elaborating on an idea of Simmons-Weiss, we
deduce Birkhoff genericity of a class of measures with respect to some diagonal
flows and extend their applications to Diophantine approximation on similarity
fractals to a non-conformal and weighted setting.Comment: 63 pages; revised the presentation of the proof of Corollary 1.2 and
made other small changes and corrections. Accepted for publication by Forum
of Mathematics, Sigm
Laplace Operators on Fractals and Related Functional Equations
We give an overview over the application of functional equations, namely the
classical Poincar\'e and renewal equations, to the study of the spectrum of
Laplace operators on self-similar fractals. We compare the techniques used to
those used in the euclidean situation. Furthermore, we use the obtained
information on the spectral zeta function to define the Casimir energy of
fractals. We give numerical values for this energy for the Sierpi\'nski gasket
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