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Centro de Astrofísica da Universidade do Porto

Scale-invariant string evolution with friction

C. J. A. P. Martins, E. P. S. Shellard

Abstract
We study the effects of friction on the scaling evolution of string networks in condensed matter and cosmological contexts. We derive a generalized "one-scale" model with the string correlation length L and velocity v as dynamical variables. In nonrelativistic systems, we obtain a well-known L~t1/2 law, showing that loop production is important. For electroweak cosmic strings, we show transient damped epoch scaling with L~t5/4 (or, in the matter era, L~t3/2). A low initial density implies an earlier period with L~t1/2. For GUT strings, the approach to linear scaling L~t is faster than previously estimated.

Physical Review D
Volume 53, Page R575
January 1996

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Institute of Astrophysics and Space Sciences

Institute of Astrophysics and Space Sciences (IA) is a new but long anticipated research infrastructure with a national dimension. It embodies a bold but feasible vision for the development of Astronomy, Astrophysics and Space Sciences in Portugal, taking full advantage and fully realizing the potential created by the national membership of the European Space Agency (ESA) and the European Southern Observatory (ESO). IA resulted from the merging the two most prominent research units in the field in Portugal: the Centre for Astrophysics of the University of Porto (CAUP) and the Center for Astronomy and Astrophysics of the University of Lisbon (CAAUL). It currently hosts more than two-thirds of all active researchers working in Space Sciences in Portugal, and is responsible for an even greater fraction of the national productivity in international ISI journals in the area of Space Sciences. This is the scientific area with the highest relative impact factor (1.65 times above the international average) and the field with the highest average number of citations per article for Portugal.

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