777 research outputs found
SLIM : Scalable Linkage of Mobility Data
We present a scalable solution to link entities across mobility datasets using their spatio-temporal information. This is a fundamental problem in many applications such as linking user identities for security, understanding privacy limitations of location based services, or producing a unified dataset from multiple sources for urban planning. Such integrated datasets are also essential for service providers to optimise their services and improve business intelligence. In this paper, we first propose a mobility based representation and similarity computation for entities. An efficient matching process is then developed to identify the final linked pairs, with an automated mechanism to decide when to stop the linkage. We scale the process with a locality-sensitive hashing (LSH) based approach that significantly reduces candidate pairs for matching. To realize the effectiveness and efficiency of our techniques in practice, we introduce an algorithm called SLIM. In the experimental evaluation, SLIM outperforms the two existing state-of-the-art approaches in terms of precision and recall. Moreover, the LSH-based approach brings two to four orders of magnitude speedup
Avoidance Control on Time Scales
We consider dynamic systems on time scales under the control of two agents.
One of the agents desires to keep the state of the system out of a given set
regardless of the other agent's actions. Leitmann's avoidance conditions are
proved to be valid for dynamic systems evolving on an arbitrary time scale.Comment: Revised edition in JOTA format. To appear in J. Optim. Theory Appl.
145 (2010), no. 3. In Pres
On the behaviour of a rumour process with random stifling
We propose a realistic generalization of the Maki-Thompson rumour model by
assuming that each spreader ceases to propagate the rumour right after being
involved in a random number of stifling experiences. We consider the process
with a general initial configuration and establish the asymptotic behaviour
(and its fluctuation) of the ultimate proportion of ignorants as the population
size grows to . Our approach leads to explicit formulas so that the
limiting proportion of ignorants and its variance can be computed.Comment: 12 pages, to appear in Environmental Modelling & Softwar
Generation of Cosmological Seed Magnetic Fields from Inflation with Cutoff
Inflation has the potential to seed the galactic magnetic fields observed
today. However, there is an obstacle to the amplification of the quantum
fluctuations of the electromagnetic field during inflation: namely the
conformal invariance of electromagnetic theory on a conformally flat underlying
geometry. As the existence of a preferred minimal length breaks the conformal
invariance of the background geometry, it is plausible that this effect could
generate some electromagnetic field amplification. We show that this scenario
is equivalent to endowing the photon with a large negative mass during
inflation. This effective mass is negligibly small in a radiation and matter
dominated universe. Depending on the value of the free parameter of the theory,
we show that the seed required by the dynamo mechanism can be generated. We
also show that this mechanism can produce the requisite galactic magnetic field
without resorting to a dynamo mechanism.Comment: Latex, 16 pages, 2 figures, 4 references added, minor corrections;
v4: more references added, boundary term written in a covariant form,
discussion regarding other gauge fields added, submitted to PRD; v5: matched
with the published versio
The Wright ω Function
This paper defines the Wright ω function, and presents some of its properties. As well as being of intrinsic mathematical interest, the function has a specific interest in the context of symbolic computation and automatic reasoning with nonstandard functions. In particular, although Wright ω is a cognate of the Lambert W function, it presents a di#erent model for handling the branches and multiple values that make the properties of W difficult to work with. By choosing a form for the function that has fewer discontinuities (and numerical difficulties), we make reasoning about expressions containing such functions easier. A final point of interest is that some of the techniques used to establish the mathematical properties can themselves potentially be automated, as was discussed in a paper presented at AISC Madrid [3]
A Simple Theory of Condensation
A simple assumption of an emergence in gas of small atomic clusters
consisting of particles each, leads to a phase separation (first order
transition). It reveals itself by an emergence of ``forbidden'' density range
starting at a certain temperature. Defining this latter value as the critical
temperature predicts existence of an interval with anomalous heat capacity
behaviour . The value suggested in literature
yields the heat capacity exponent .Comment: 9 pages, 1 figur
On the infrared freezing of perturbative QCD in the Minkowskian region
The infrared freezing of observables is known to hold at fixed orders of
perturbative QCD if the Minkowskian quantities are defined through the analytic
continuation from the Euclidean region. In a recent paper [1] it is claimed
that infrared freezing can be proved also for Borel resummed all-orders
quantities in perturbative QCD. In the present paper we obtain the Minkowskian
quantities by the analytic continuation of the all-orders Euclidean amplitudes
expressed in terms of the inverse Mellin transform of the corresponding Borel
functions [2]. Our result shows that if the principle of analytic continuation
is preserved in Borel-type resummations, the Minkowskian quantities exhibit a
divergent increase in the infrared regime, which contradicts the claim made in
[1]. We discuss the arguments given in [1] and show that the special
redefinition of Borel summation at low energies adopted there does not
reproduce the lowest order result obtained by analytic continuation.Comment: 19 pages, 1 figur
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