2,565 research outputs found
Limit theorem for a time-dependent coined quantum walk on the line
We study time-dependent discrete-time quantum walks on the one-dimensional
lattice. We compute the limit distribution of a two-period quantum walk defined
by two orthogonal matrices. For the symmetric case, the distribution is
determined by one of two matrices. Moreover, limit theorems for two special
cases are presented
Absorption problems for quantum walks in one dimension
This paper treats absorption problems for the one-dimensional quantum walk
determined by a 2 times 2 unitary matrix U on a state space {0,1,...,N} where N
is finite or infinite by using a new path integral approach based on an
orthonormal basis P, Q, R and S of the vector space of complex 2 times 2
matrices. Our method studied here is a natural extension of the approach in the
classical random walk.Comment: 15 pages, small corrections, journal reference adde
Produção de celulases em farelos de trigo e arroz e grão de trigo por Lentinula edodes.
Editores técnicos: Marcílio José Thomazini, Elenice Fritzsons, Patrícia Raquel Silva, Guilherme Schnell e Schuhli, Denise Jeton Cardoso, Luziane Franciscon. EVINCI. Resumos
Analysis of scale-free networks based on a threshold graph with intrinsic vertex weights
Many real networks are complex and have power-law vertex degree distribution,
short diameter, and high clustering. We analyze the network model based on
thresholding of the summed vertex weights, which belongs to the class of
networks proposed by Caldarelli et al. (2002). Power-law degree distributions,
particularly with the dynamically stable scaling exponent 2, realistic
clustering, and short path lengths are produced for many types of weight
distributions. Thresholding mechanisms can underlie a family of real complex
networks that is characterized by cooperativeness and the baseline scaling
exponent 2. It contrasts with the class of growth models with preferential
attachment, which is marked by competitiveness and baseline scaling exponent 3.Comment: 5 figure
String-Inspired Chern-Simons Modified Gravity In 4-Dimensions
Chern-Simons modified gravity models in 4-dimensions are shown to be special
cases of low energy effective string models to first order in the string
constant.Comment: To appear in the European Physics Journal
Recurrence of biased quantum walks on a line
The Polya number of a classical random walk on a regular lattice is known to
depend solely on the dimension of the lattice. For one and two dimensions it
equals one, meaning unit probability to return to the origin. This result is
extremely sensitive to the directional symmetry, any deviation from the equal
probability to travel in each direction results in a change of the character of
the walk from recurrent to transient. Applying our definition of the Polya
number to quantum walks on a line we show that the recurrence character of
quantum walks is more stable against bias. We determine the range of parameters
for which biased quantum walks remain recurrent. We find that there exist
genuine biased quantum walks which are recurrent.Comment: Journal reference added, minor corrections in the tex
Stable periodic waves in coupled Kuramoto-Sivashinsky - Korteweg-de Vries equations
Periodic waves are investigated in a system composed of a
Kuramoto-Sivashinsky - Korteweg-de Vries (KS-KdV) equation, which is linearly
coupled to an extra linear dissipative equation. The model describes, e.g., a
two-layer liquid film flowing down an inclined plane. It has been recently
shown that the system supports stable solitary pulses. We demonstrate that a
perturbation analysis, based on the balance equation for the field momentum,
predicts the existence of stable cnoidal waves (CnWs) in the same system. It is
found that the mean value U of the wave field u in the main subsystem, but not
the mean value of the extra field, affects the stability of the periodic waves.
Three different areas can be distinguished inside the stability region in the
parameter plane (L,U), where L is the wave's period. In these areas, stable
are, respectively, CnWs with positive velocity, constant solutions, and CnWs
with negative velocity. Multistability, i.e., the coexistence of several
attractors, including the waves with several maxima per period, appears at
large value of L. The analytical predictions are completely confirmed by direct
simulations. Stable waves are also found numerically in the limit of vanishing
dispersion, when the KS-KdV equation goes over into the KS one.Comment: a latex text file and 16 eps files with figures. Journal of the
Physical Society of Japan, in pres
Controlling discrete quantum walks: coins and intitial states
In discrete time, coined quantum walks, the coin degrees of freedom offer the
potential for a wider range of controls over the evolution of the walk than are
available in the continuous time quantum walk. This paper explores some of the
possibilities on regular graphs, and also reports periodic behaviour on small
cyclic graphs.Comment: 10 (+epsilon) pages, 10 embedded eps figures, typos corrected,
references added and updated, corresponds to published version (except figs
5-9 optimised for b&w printing here
Mass dependence of the gravitationally-induced wave-function phase
The leading mass dependence of the wave function phase is calculated in the
presence of gravitational interactions. The conditions under which this phase
contains terms depending on both the square of the mass and the gravitational
constant are determined. The observability of such terms is briefly discussed.Comment: 5 pages, no figures, requires Revtex. The discussion has been
extended and clarifie
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