Observations on the method of determining the velocity of airships

To obtain the absolute velocity of an airship by knowing the speed at which two routes are covered, we have only to determine the geographical direction of the routes which we locate from a map, and the angles of routes as given by the compass, after correcting for the variation (the algebraical sum of the local magnetic declination and the deviation)

Locality and Bell's inequality

We prove that the locality condition is irrelevant to Bell in equality. We check that the real origin of the Bell's inequality is the assumption of applicability of classical (Kolmogorovian) probability theory to quantum mechanics. We describe the chameleon effect which allows to construct an experiment realizing a local, realistic, classical, deterministic and macroscopic violation of the Bell inequalities.Comment: 23 pages, Plain TeX, A talk given at Capri conference, July 2000, Corrected and Extended versio

Efficient size estimation and impossibility of termination in uniform dense population protocols

We study uniform population protocols: networks of anonymous agents whose pairwise interactions are chosen at random, where each agent uses an identical transition algorithm that does not depend on the population size $n$. Many existing polylog$(n)$ time protocols for leader election and majority computation are nonuniform: to operate correctly, they require all agents to be initialized with an approximate estimate of $n$ (specifically, the exact value $\lfloor \log n \rfloor$). Our first main result is a uniform protocol for calculating $\log(n) \pm O(1)$ with high probability in $O(\log^2 n)$ time and $O(\log^4 n)$ states ($O(\log \log n)$ bits of memory). The protocol is converging but not terminating: it does not signal when the estimate is close to the true value of $\log n$. If it could be made terminating, this would allow composition with protocols, such as those for leader election or majority, that require a size estimate initially, to make them uniform (though with a small probability of failure). We do show how our main protocol can be indirectly composed with others in a simple and elegant way, based on the leaderless phase clock, demonstrating that those protocols can in fact be made uniform. However, our second main result implies that the protocol cannot be made terminating, a consequence of a much stronger result: a uniform protocol for any task requiring more than constant time cannot be terminating even with probability bounded above 0, if infinitely many initial configurations are dense: any state present initially occupies $\Omega(n)$ agents. (In particular, no leader is allowed.) Crucially, the result holds no matter the memory or time permitted. Finally, we show that with an initial leader, our size-estimation protocol can be made terminating with high probability, with the same asymptotic time and space bounds.Comment: Using leaderless phase cloc

A Tale of Four Caves: ESR Dating of Mousterian Layers at Iberian Archaeological Sites

This study was undertaken to provide supporting evidence for the late presence of Neanderthals in Iberia at the end of the Middle Paleolithic. This period is almost impossible to date accurately by the conventional radiocarbon method. Accordingly electron spin resonance (ESR) was used to obtain ages for four Spanish sites. They were EI Pendo in the Cantabrian north, Carihuela in Andalusia and Gorham's and Vanguard caves at Gibraltar. The sites were chosen to allow the greatest variety in geographic settings, latitudes and sedimentation. They were either under excavation or had been excavated recently following modem techniques. A multidisciplinary approach to dating the archaeological contexts was being proposed for all the sites except EI Pendo whose deposits had been already dated but only on the basis of sedimentological and faunal analyses. This was the first research program to apply ESR to such a variety of sites and compare its results with that of such a variety of other archaeometric dating techniques. The variety allowed a further dimension to the research that is the opportunity of appraising first hand the applicability and advantages of a new dating technique and determining its accuracy as an archaeological dating method in comparison with other techniques. Test samples for the research were collected at the sites as well as at the Museo de Ciencias Naturales in Madrid and the Gibraltar Museum. The ESR results for EI Pendo provide a terminus post quem of 31 Ka for the presence of the Neanderthal at the site. Those for Carihuela permit the Neanderthal skeletal remains found in layers Vand VI to be dated between 45 ka and 74 ka and between 67 ka and 86 ka respectively. The data also confirm the late presence of the Neanderthals in Andalusia. The results for the Gibraltar final Mousterian layer also confirm the presence of Neanderthals in southern Spain at 36.9 ±5 to 40.3 ±5 ka. While there are a number of secure dates for early Aurignacian deposits in Spain the results of the present research provide the first solid evidence of the late presence of Homo sapiens neanderthalensis in the Iberian Peninsula. Furthermore, from the data collected it can also be concluded that the ESR method is accurate and eminently suitable for dating archaeological contexts.Doctor of Philosophy (PhD