2 resultados para rapid evolution

em Universidad de Alicante


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The English language and the Internet, both separately and taken together, are nowadays well-acknowledged as powerful forces which influence and affect the lexico-grammatical characteristics of other languages world-wide. In fact, many authors like Crystal (2004) have pointed out the emergence of the so-called Netspeak, that is, the language used in the Net or World Wide Web; as Crystal himself (2004: 19) puts it, ‘a type of language displaying features that are unique to the Internet […] arising out of its character as a medium which is electronic, global and interactive’. This ‘language’, however, may be differently understood: either as an adaptation of the English language proper to internet requirements and purposes, or as a new and rapidly-changing and developing language as a result of a rapid evolution or adaptation to Internet requirements of almost all world languages, for whom English is a trendsetter. If the second and probably most plausible interpretation is adopted, there are three salient features of ‘Netspeak’: (a) the rapid expansion of all its new linguistic developments thanks to the Internet itself, which may lead to the generalization and widespread acceptance of new words, coinages, or meanings, hundreds of times faster than was the case with the printed media. As said above, (b) the visible influence of English, the most prevalent language on the Internet. Consequently, (c) this new language tends to reduce the ‘distance’ between English and other languages as well as the ignorance of the former by speakers of other languages, since the ‘Netspeak’ version of the latter adopts grammatical, syntactic and lexical features of English. Thus, linguistic differences may even disappear when code-switching and/or borrowing occurs, as whole fragments of English appear in other language contexts. As a consequence of the new situation, an ideal context appears for interlanguage or multilingual word formation to thrive: puns, blends, compounds and word creativity in general find in the web the ideal place to gain rapid acceptance world-wide, as a result of fashion, coincidence, or sheer merit of the new linguistic proposals.

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Context. The rotational evolution of isolated neutron stars is dominated by the magnetic field anchored to the solid crust of the star. Assuming that the core field evolves on much longer timescales, the crustal field evolves mainly though Ohmic dissipation and the Hall drift, and it may be subject to relatively rapid changes with remarkable effects on the observed timing properties. Aims. We investigate whether changes of the magnetic field structure and strength during the star evolution may have observable consequences in the braking index n. This is the most sensitive quantity to reflect small variations of the timing properties that are caused by magnetic field rearrangements. Methods. We performed axisymmetric, long-term simulations of the magneto-thermal evolution of neutron stars with state-of-the-art microphysical inputs to calculate the evolution of the braking index. Relatively rapid magnetic field modifications can be expected only in the crust of neutron stars, where we focus our study. Results. We find that the effect of the magnetic field evolution on the braking index can be divided into three qualitatively different stages depending on the age and the internal temperature: a first stage that may be different for standard pulsars (with n ~ 3) or low field neutron stars that accreted fallback matter during the supernova explosion (systematically n < 3); in a second stage, the evolution is governed by almost pure Ohmic field decay, and a braking index n > 3 is expected; in the third stage, at late times, when the interior temperature has dropped to very low values, Hall oscillatory modes in the neutron star crust result in braking indices of a high absolute value and both positive and negative signs. Conclusions. Current magneto-thermal evolution models predict a large contribution to the timing noise and, in particular, to the braking index, from temporal variations of the magnetic field. Models with strong (≳ 1014 G) multipolar or toroidal components, even with a weak (~1012 G) dipolar field are consistent with the observed trend of the timing properties.