74 research outputs found
On random walks in random scenery
This paper considers 1-dimensional generalized random walks in random
scenery. That is, the steps of the walk are generated by an arbitrary
stationary process, and also the scenery is a priori arbitrary stationary.
Under an ergodicity condition--which is satisfied in the classical case--a
simple proof of the distinguishability of periodic sceneries is given.Comment: Published at http://dx.doi.org/10.1214/074921706000000068 in the IMS
Lecture Notes--Monograph Series
(http://www.imstat.org/publications/lecnotes.htm) by the Institute of
Mathematical Statistics (http://www.imstat.org
Elliptic Curve Scalar Multiplication Combining Yao’s Algorithm and Double Bases
Abstract. In this paper we propose to take one step back in the use of double base number systems for elliptic curve point scalar multiplication. Using a mod-ified version of Yao’s algorithm, we go back from the popular double base chain representation to a more general double base system. Instead of representing an integer k as Pn i=1 2 bi3ti where (bi) and (ti) are two decreasing sequences, we only set a maximum value for both of them. Then, we analyze the efficiency of our new method using different bases and optimal parameters. In particular, we pro-pose for the first time a binary/Zeckendorf representation for integers, providing interesting results. Finally, we provide a comprehensive comparison to state-of-the-art methods, including a large variety of curve shapes and latest point addition formulae speed-ups
On the automatic construction of indistinguishable operations
An increasingly important design constraint for software running
on ubiquitous computing devices is security, particularly against
physical methods such as side-channel attack. One well studied methodology
for defending against such attacks is the concept of indistinguishable
functions which leak no information about program control
flow since all execution paths are computationally identical. However,
constructing such functions by hand becomes laborious and error prone
as their complexity increases. We investigate techniques for automating
this process and find that effective solutions can be constructed with
only minor amounts of computational effort.Fundação para a Ciência e Tecnologia - SFRH/BPD/20528/2004
Effective-Range Expansion of the Neutron-Deuteron Scattering Studied by a Quark-Model Nonlocal Gaussian Potential
The S-wave effective range parameters of the neutron-deuteron (nd) scattering
are derived in the Faddeev formalism, using a nonlocal Gaussian potential based
on the quark-model baryon-baryon interaction fss2. The spin-doublet low-energy
eigenphase shift is sufficiently attractive to reproduce predictions by the
AV18 plus Urbana three-nucleon force, yielding the observed value of the
doublet scattering length and the correct differential cross sections below the
deuteron breakup threshold. This conclusion is consistent with the previous
result for the triton binding energy, which is nearly reproduced by fss2
without reinforcing it with the three-nucleon force.Comment: 21 pages, 6 figures and 6 tables, submitted to Prog. Theor. Phy
Spectrum of multidimensional dynamical systems with positive entropy
Applying methods of harmonic analysis we give a simple proof of the multidimensional version of the Rokhlin-Sinaǐ theorem which states that a Kolmogorov -action on a Lebesgue space has a countable Lebesgue spectrum. At the same time we extend this theorem to -actions. Next, using its relative version, we extend to -actions some other general results connecting spectrum and entropy
On extremal and perfect σ-algebras for -actions on a Lebesgue space
We show that for every positive integer d there exists a -action and an extremal σ-algebra of it which is not perfect
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