منابع مشابه
Effects of friction on cosmic strings.
We study the evolution of cosmic strings taking into account the frictional force due to the surrounding radiation. We consider small perturbations on straight strings, oscillation of circular loops and small perturbations on circular loops. For straight strings, friction exponentially suppresses perturbations whose co-moving scale crosses the horizon before cosmological time t∗ ∼ μ−2 (in Planc...
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We study the effect of free streaming in a universe with cosmic strings with timevarying tension as well as with constant tension. Although current cosmological observations suggest that fluctuation seeded by cosmic strings cannot be the primary source of cosmic density fluctuation, some contributions from them are still allowed. Since cosmic strings actively produce isocurvature fluctuation, t...
متن کاملCosmic Strings & Cosmic Variance
By using a simple analytical model based on counting random multiple impulses inflicted on photons by a network of cosmic strings we show how to construct the general q-point temperature correlation function of the Cosmic Microwave Background radiation. Our analysis is sensible specially for large angular scales where the Kaiser-Stebbins effect is dominant. Then we concentrate our study on the ...
متن کاملCosmic Strings
Cosmic strings, a hot subject in the 1980’s and early 1990’s, lost its appeal when it was found that it leads to inconsistencies in the power spectrum of the measured cosmic microwave background temperature anisotropies. However, topological defects in general, and cosmic strings in particular, are deeply rooted in the framework of grand unified theories. Indeed, it was shown that cosmic string...
متن کاملCosmic Strings
Cosmic strings belong to the basic extremals of the Kähler action. The upper bound for string tension of the cosmic strings is T ' .5 × 10−6/G and in the same range as the string tension of GUT strings and this makes them very interesting cosmologically although TGD cosmic strings have otherwise practically nothing to do with their GUT counterparts.
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ژورنال
عنوان ژورنال: Physical Review D
سال: 1993
ISSN: 0556-2821
DOI: 10.1103/physrevd.48.2502