Detection of cosmic superstrings by geodesic test particle motion

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(p,q)-strings are bound states of p F-strings and q D-strings and are\npredicted to form at the end of brane inflation. As such these cosmic\nsuperstrings should be detectable in the universe. In this paper we argue that\nthey can be detected by the way that massive and massless test particles move\nin the space-time of these cosmic superstrings, in particular we study\nsolutions to the geodesic equation in the space-time of field theoretical\n(p,q)-strings. The geodesics can be classified according to the test particle's\nenergy, angular momentum and momentum in the direction of the string axis. We\ndiscuss how the change of the magnetic fluxes, the ratio between the symmetry\nbreaking scale and the Planck mass, the Higgs to gauge boson mass ratios and\nthe binding between the F- and D-strings, respectively, influence the motion of\nthe test particles. While massless test particles can only move on escape\norbits, a new feature as compared to the infinitely thin string limit is the\nexistence of bound orbits for massive test particles. In particular, we observe\nthat - in contrast to the space-time of a single Abelian-Higgs string - bound\norbits for massive test particles in (p,q)-string space-times are possible if\nthe Higgs boson mass is larger than the gauge boson mass. We also compute the\neffect of the binding between the p- and the q-string on observables such as\nthe light deflection and the perihelion shift. While light deflection can also\nbe caused by other matter distributions, the possibility of a negative\nperihelion shift seems to be a feature of finite width cosmic strings that\ncould lead to the unmistakable identification of such objects. In Melvin\nspace-times, which are asymptotically non-conical, massive test particles have\nto move on bound orbits, while massless test particles can only escape to\ninfinity if their angular momentum vanishes.\n