196,710 research outputs found
Malagasy Dialects and the Peopling of Madagascar
No full textServa M, Petroni F, Volchenkov D, Wichmann S. Malagasy Dialects and the Peopling of Madagascar. Interface. Journal of the Royal Society. 2012;9(66):54-67
Effective localization induced by noise and nonlinearity
No full textBlanchard P, Pasquini M, Serva M. Effective localization induced by noise and nonlinearity. PHYSICA D. 2000;141(3-4):214-220.With the aid of a very simple model with only two possible configurations, we study the dynamical transition from delocalized to localized states for quantum bistable systems. Results may have relevance for the understanding of the phenomenology of some mesoscopic systems which are usually found in a localized state as for example pyramidal AsH3 molecule. The interaction with the environment is modeled by considering bath external noise disturbance and nonlinear effects due to the contraction of the Hilbert space. The noise alone produces decoherence and suppression of tunneling, but delocalized states spontaneously evolve into localized ones only when nonlinearity is also present. (C) 2000 Elsevier Science B.V. All rights reserved
CLDF dataset derived from Serva's "Dialects of Madagascar" from 2020
No full textCite the source of the dataset as:
Serva M., Pasquini M. (2020): Dialects of Madagascar, PLoS ONE 15(10)
Indo-European languages tree by Levenshtein distance
No full textThe evolution of languages closely resembles the evolution of haploid organisms. This similarity has been recently exploited (Gray R. D. and Atkinson Q. D., Nature, 426 (2003) 435; Gray R. D. and Jordan F. M., Nature, 405 (2000) 1052) to construct languagetrees. The key point is the definition of a distance among all pairs of languages which is the analogous of a genetic distance. Many methods have been proposed to define these distances; one of these, used by glottochronology, computes the distance from the percentage of shared "cognates". Cognates are words inferred to have a common historical origin, and subjective judgment plays a relevant role in the identification process. Here we push closer the analogy with evolutionary biology and we introduce a genetic distance among language pairs by considering a renormalized Levenshtein distance among words with same meaning and averaging on all words contained in a Swadesh list (Swadesh M., Proc. Am. Philos. Soc., 96 (1952) 452). The subjectivity of process is consistently reduced and the reproducibility is highly facilitated. We test our method against the Indo-European group considering fifty different languages and the two hundred words of the Swadesh list for any of them. We find out a tree which closely resembles the one published in Gray and Atkinson (2003), with some significant differences
Measures of lexical distance between languages
No full textThe idea of measuring distance between languages seems to have its roots in the work of the French explorer Dumont D’Urville (1832) [13]. He collected comparative word lists for various languages during his voyages aboard the Astrolabe from 1826 to 1829 and, in his work concerning the geographical division of the Pacific, he proposed a method for measuring the degree of relation among languages. The method used by modern glottochronology, developed by Morris Swadesh in the 1950s, measures distances from the percentage of shared cognates, which are words with a common historical origin.
Recently, we proposed a new automated method which uses the normalized Levenshtein distances among words with the same meaning and averages on the words contained in a list. Recently another group of scholars, Bakker et al. (2009) [8] and Holman et al. (2008) [9], proposed a refined version of our definition including a second normalization. In this paper we compare the information content of our definition with the refined version in order to
decide which of the two can be applied with greater success to resolve relationships among languages
Real Prices from Spot Foreign Exchange Market
No full textIn this work we discuss the problem of price definition when using high frequency foreign
exchange data. If one uses the spot mid price a strong autocorrelation of returns, at one lag, is
found which is only due to microstructure effect and does not capture the real behavior of
price dynamics. This autocorrelation increases the intraday volatility estimated from this type
of data. To solve this problem we introduce an algorithm which is able, by using the no-
arbitrage principle, of eliminating every microstructure effects
Constant speed random particles spontaneously confined on the surface of an expanding sphere
No full textThe particles that we describe here can only move at the speed of light c in three-dimensional space. The velocity, which randomly but continuously changes direction, can be represented as a point on the surface of a sphere of constant radius c, and its trajectories may only connect points of this variety. The Wiener process that we use to describe the velocity dynamics on the surface of the sphere is anisotropic since the infinitesimal variation of the velocity is not only always orthogonal to the velocity itself (which guarantees a constant speed), but also to the position. This choice for the infinitesimal variation of the velocity is the one that best slows down the diffusion of particles in space by random motion at the speed of light. As a result of these dynamics, the position of the particles spontaneously remain confined on the surface of an expanding sphere whose radius increases, for large times, as the square root of time
Brownian Motion at the Speed of Light: A New Lorentz Invariant Family of Processes
No full textWe consider here a new family of processes which describe particles which only can move at the speed of light c in the ordinary 3D physical space. The velocity, which randomly changes direction, can be represented as a point on the surface of a sphere of radius c and its trajectories only may connect points of this variety. A process can be constructed both by considering jumps from one point to another (velocity changes discontinuously) and by continuous velocity trajectories on the surface. We recently proposed to follow this second strategy assuming that the velocity is described by a Wiener process (which is isotropic only in the ’rest frame’) on the surface of the sphere. Using both Ito calculus and Lorentz boost rules, we succeed here in characterizing the entire Lorentz-invariant family of processes. Moreover, we highlight and describe the short-term ballistic behavior versus the long-term diffusive behavior of the particles in the 3D physical space
Particles with constant speed and random velocity in 3+1 space-time: separation of the space variables
No full textWe consider a particle in 3+1 space-time dimensions which constantly moves at speed of light c, randomly changing its velocity which can be represented by a point on the surface of a sphere of radius c. The velocity performs an isotropic Wiener process on this surface so that the velocity trajectories are almost everywhere continuous although not differentiable, while the position trajectories are continuous and differentiable. Together with the process that describes the particle in the 'rest frame', where the diffusion of velocity on the surface of the sphere is isotropic, the entire family of anisotropic processes which result from Lorentz boosts is also described. The focus of this article is on stochastic evolution in space. We identify a reduced set of variables whose stochastic evolution is autonomous from the remaining variables, but, nevertheless, carry all the relevant information concerning the spatial properties of the process. The associated stochastic equations as well the Forward Kolmogorov equation are considerably simplified compared to those of the complete set of position and velocity variables
COMMENT ON REPEATED MEASUREMENTS IN STOCHASTIC MECHANICS - REPLY
No full textBlanchard P, SERVA M. COMMENT ON REPEATED MEASUREMENTS IN STOCHASTIC MECHANICS - REPLY. PHYSICAL REVIEW D. 1995;51(6):3132-3134
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