DF-strings from D3D̄3 as cosmic strings

We study Dirac-Born-Infeld type effective field theory of a complex tachyon and U(1) × U(1) gauge fields describing a D33 system. Classical solutions of straight global and local DF-strings with quantized vorticity are found and are classified into two types by the asymptotic behavior of the tachyon amplitude. For sufficiently large radial distances, one has linearly-growing tachyon amplitude and the other logarithmically-growing tachyon amplitude. A constant radial electric flux density denoting the fundamental-string background makes the obtained DF-strings thick. The other electric flux density parallel to the strings is localized, which represents localization of fundamental strings in the D1-F1 bound states. Since these DF-strings are formed in the coincidence limit of the D33, these cosmic DF-strings are safe from inflation induced by the approach of the separated D3 and 3.