30,435 research outputs found
Balanced simplices
An additive cellular automaton is a linear map on the set of infinite
multidimensional arrays of elements in a finite cyclic group
. In this paper, we consider simplices appearing in the
orbits generated from arithmetic arrays by additive cellular automata. We prove
that they are a source of balanced simplices, that are simplices containing all
the elements of with the same multiplicity. For any
additive cellular automaton of dimension or higher, the existence of
infinitely many balanced simplices of appearing in
such orbits is shown, and this, for an infinite number of values . The
special case of the Pascal cellular automata, the cellular automata generating
the Pascal simplices, that are a generalization of the Pascal triangle into
arbitrary dimension, is studied in detail.Comment: 33 pages ; 11 figures ; 1 tabl
Fast algorithm for the 3-D DCT-II
Recently, many applications for three-dimensional
(3-D) image and video compression have been proposed using 3-D discrete cosine transforms (3-D DCTs). Among different types of DCTs, the type-II DCT (DCT-II) is the most used. In order to use the 3-D DCTs in practical applications, fast 3-D algorithms are essential. Therefore, in this paper, the 3-D vector-radix decimation-in-frequency (3-D VR DIF) algorithm that calculates the 3-D DCT-II directly is introduced. The mathematical analysis and the implementation of the developed algorithm are presented,
showing that this algorithm possesses a regular structure, can be implemented in-place for efficient use of memory, and is faster than the conventional row-column-frame (RCF) approach. Furthermore, an application of 3-D video compression-based 3-D DCT-II is implemented using the 3-D new algorithm. This has led to a substantial speed improvement for 3-D DCT-II-based compression systems and proved the validity of the developed algorithm
Multidimensional extension of the Morse--Hedlund theorem
A celebrated result of Morse and Hedlund, stated in 1938, asserts that a
sequence over a finite alphabet is ultimately periodic if and only if, for
some , the number of different factors of length appearing in is
less than . Attempts to extend this fundamental result, for example, to
higher dimensions, have been considered during the last fifteen years. Let
. A legitimate extension to a multidimensional setting of the notion of
periodicity is to consider sets of \ZZ^d definable by a first order formula
in the Presburger arithmetic . With this latter notion and using a
powerful criterion due to Muchnik, we exhibit a complete extension of the
Morse--Hedlund theorem to an arbitrary dimension $d$ and characterize sets of
$\ZZ^d$ definable in in terms of some functions counting recurrent
blocks, that is, blocks occurring infinitely often
Workshop on Verification and Theorem Proving for Continuous Systems (NetCA Workshop 2005)
Oxford, UK, 26 August 200
Popular progression differences in vector spaces II
Green used an arithmetic analogue of Szemer\'edi's celebrated regularity
lemma to prove the following strengthening of Roth's theorem in vector spaces.
For every , , and prime number , there is a least
positive integer such that if ,
then for every subset of of density at least there is
a nonzero for which the density of three-term arithmetic progressions with
common difference is at least . We determine for the
tower height of up to an absolute constant factor and an
additive term depending only on . In particular, if we want half the random
bound (so ), then the dimension required is a tower of
twos of height . It turns
out that the tower height in general takes on a different form in several
different regions of and , and different arguments are used
both in the upper and lower bounds to handle these cases.Comment: 34 pages including appendi
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