4,497 research outputs found
Pattern Matching in Multiple Streams
We investigate the problem of deterministic pattern matching in multiple
streams. In this model, one symbol arrives at a time and is associated with one
of s streaming texts. The task at each time step is to report if there is a new
match between a fixed pattern of length m and a newly updated stream. As is
usual in the streaming context, the goal is to use as little space as possible
while still reporting matches quickly. We give almost matching upper and lower
space bounds for three distinct pattern matching problems. For exact matching
we show that the problem can be solved in constant time per arriving symbol and
O(m+s) words of space. For the k-mismatch and k-difference problems we give
O(k) time solutions that require O(m+ks) words of space. In all three cases we
also give space lower bounds which show our methods are optimal up to a single
logarithmic factor. Finally we set out a number of open problems related to
this new model for pattern matching.Comment: 13 pages, 1 figur
Towards predictive modelling of near-edge structures in electron energy loss spectra of AlN based ternary alloys
Although electron energy loss near edge structure analysis provides a tool
for experimentally probing unoccupied density of states, a detailed comparison
with simulations is necessary in order to understand the origin of individual
peaks. This paper presents a density functional theory based technique for
predicting the N K-edge for ternary (quasi-binary) nitrogen alloys by adopting
a core hole approach, a methodology that has been successful for binary nitride
compounds. It is demonstrated that using the spectra of binary compounds for
optimising the core hole charge ( for cubic TiAlN
and for wurtzite AlGaN), the predicted spectra
evolutions of the ternary alloys agree well with the experiments. The spectral
features are subsequently discussed in terms of the electronic structure and
bonding of the alloys.Comment: 11 pages, 9 figures, 1 tabl
Introductory clifford analysis
In this chapter an introduction is given to Clifford analysis and the underlying Clifford algebras. The functions under consideration are defined on Euclidean space and take values in the universal real or complex Clifford algebra, the structure and properties of which are also recalled in detail. The function theory is centered around the notion of a monogenic function, which is a null solution of a generalized Cauchy–Riemann operator, which is rotation invariant and factorizes the Laplace operator. In this way, Clifford analysis may be considered as both a generalization to higher dimension of the theory of holomorphic functions in the complex plane and a refinement of classical harmonic analysis. A notion of monogenicity may also be associated with the vectorial part of the Cauchy–Riemann operator, which is called the Dirac operator; some attention is paid to the intimate relation between both notions. Since a product of monogenic functions is, in general, no longer monogenic, it is crucial to possess some tools for generating monogenic functions: such tools are provided by Fueter’s theorem on one hand and the Cauchy–Kovalevskaya extension theorem on the other hand. A corner stone in this function theory is the Cauchy integral formula for representation of a monogenic function in the interior of its domain of monogenicity. Starting from this representation formula and related integral formulae, it is possible to consider integral transforms such as Cauchy, Hilbert, and Radon transforms, which are important both within the theoretical framework and in view of possible applications
On-Shell Recursion Relations for Generic Theories
We show that on-shell recursion relations hold for tree amplitudes in generic
two derivative theories of multiple particle species and diverse spins. For
example, in a gauge theory coupled to scalars and fermions, any amplitude with
at least one gluon obeys a recursion relation. In (super)gravity coupled to
scalars and fermions, the same holds for any amplitude with at least one
graviton. This result pertains to a broad class of theories, including QCD, N=4
SYM, and N=8 supergravity.Comment: 19 pages, 3 figure
Formation of Spaced Cleavage and Concurrent Mass Removal of Si02, Meguma Goup Metagreywackes, Goldenville, Nova Scotia
Increasing inequancy and decreasing fluctuation of long axes of quartz grains from lithons to cleavage zones in Heguna Group metagreywackes indicate an increase in strain. This strain increase is best ascribed to pervasive pressure solution in which quartz grains are trimmed to yield nearly rectangular sections in cleavage zones, as compared to their irregular outlines in lithons. Shortening calculated from a one-dimensional strain model reaches 60-7OZ in cleavage zones. Comparable values of shortening are calculated from modal analyses, and from chemical analyses of cleavages and lithons.
The Implication of such shortening is that about ten percent of all the quartz in the original rock has been removed from the immediate system. This demands volumes of water about one order of magnitude greater than any likely content of connate water. The transport system was a dynamic one, involving most of the rock volume.
RÉSUMÉ
L'accroieseaent de l'inégalité et la baisse des fluctuations des longs axes des grains de quartz, des lithons jusqu'aux zones de clivage, dans les métagrauwackes du groupe Méguma, indique une haueae de tension. Cette hausse de tension est attribute à la solution de pression pénétrante dans laquelle les grains de quartz sont tallés et donnent des sections presque rectangulaires dans les zones de clivage, comparé à leur profile irrégulier dans les lithons. Le raccourcissement, calculi à partlr d'un modèle de pression unidimensionnel, atteint des valeurs entre 60 et 702 dans les zones de clivage. Des valeurs comparables du raccourcissement sont calculées à partlr d'analyses modales, et d'analyses chimiques des clivages et des lithons.
L'implicatlon de ce raccourclssement est qu'environ dix pourcent de tout le quartz de la roche originaire, a été supérime du système immédiate Cela exige des volumes d'eau d'un ordre de grandeur plus important que n'importe quel système inné d'eau vraissembable. Ce système de transport était un système dynamique qui comprenait la majorité du volume des roches.
[Traduit par le journal
Synchronization Gauges and the Principles of Special Relativity
The axiomatic bases of Special Relativity Theory (SRT) are thoroughly
re-examined from an operational point of view, with particular emphasis on the
status of Einstein synchronization in the light of the possibility of arbitrary
synchronization procedures in inertial reference frames. Once correctly and
explicitly phrased, the principles of SRT allow for a wide range of `theories'
that differ from the standard SRT only for the difference in the chosen
synchronization procedures, but are wholly equivalent to SRT in predicting
empirical facts. This results in the introduction, in the full background of
SRT, of a suitable synchronization gauge. A complete hierarchy of
synchronization gauges is introduced and elucidated, ranging from the useful
Selleri synchronization gauge (which should lead, according to Selleri, to a
multiplicity of theories alternative to SRT) to the more general Mansouri-Sexl
synchronization gauge and, finally, to the even more general
Anderson-Vetharaniam-Stedman's synchronization gauge. It is showed that all
these gauges do not challenge the SRT, as claimed by Selleri, but simply lead
to a number of formalisms which leave the geometrical structure of Minkowski
spacetime unchanged. Several aspects of fundamental and applied interest
related to the conventional aspect of the synchronization choice are discussed,
encompassing the issue of the one-way velocity of light on inertial and
rotating reference frames, the GPS's working, and the recasting of Maxwell
equations in generic synchronizations. Finally, it is showed how the gauge
freedom introduced in SRT can be exploited in order to give a clear explanation
of the Sagnac effect for counter-propagating matter beams.Comment: 56 pages, 3 eps figures, invited paper; to appear in Foundations of
Physics (Special Issue to honor Prof. Franco Selleri on his 70th birthday
On Alternative Supermatrix Reduction
We consider a nonstandard odd reduction of supermatrices (as compared with
the standard even one) which arises in connection with possible extension of
manifold structure group reductions. The study was initiated by consideration
of the generalized noninvertible superconformal-like transformations. The
features of even- and odd-reduced supermatrices are investigated on a par. They
can be unified into some kind of "sandwich" semigroups. Also we define a
special module over even- and odd-reduced supermatrix sets, and the generalized
Cayley-Hamilton theorem is proved for them. It is shown that the odd-reduced
supermatrices represent semigroup bands and Rees matrix semigroups over a unit
group.Comment: 22 pages, Standard LaTeX with AmS font
Theoretical Aspects of the Equivalence Principle
We review several theoretical aspects of the Equivalence Principle (EP). We
emphasize the unsatisfactory fact that the EP maintains the absolute character
of the coupling constants of physics while General Relativity, and its
generalizations (Kaluza-Klein,..., String Theory), suggest that all absolute
structures should be replaced by dynamical entities. We discuss the
EP-violation phenomenology of dilaton-like models, which is likely to be
dominated by the linear superposition of two effects: a signal proportional to
the nuclear Coulomb energy, related to the variation of the fine-structure
constant, and a signal proportional to the surface nuclear binding energy,
related to the variation of the light quark masses. We recall the various
theoretical arguments (including a recently proposed anthropic argument)
suggesting that the EP be violated at a small, but not unmeasurably small
level. This motivates the need for improved tests of the EP. These tests are
probing new territories in physics that are related to deep, and mysterious,
issues in fundamental physics.Comment: 21 pages, no figures; submitted to a "focus issue" of Classical and
Quantum Gravity on Tests of the Weak Equivalence Principle, organized by
Clive Speake and Clifford Wil
- …