Collisions of cosmic F- and D-strings

Abstract

Recent work suggests that fundamental and Dirichlet strings, and their (p, q) bound states, may be observed as cosmic strings. The evolution of cosmic string networks, and therefore their observational signals, depends on what happens when two strings collide. We study this in string perturbation theory for collisions between all possible pairs of strings; different cases involve sphere, disk, and annulus amplitudes. The result also depends on the details of compactification; the dependence on ratios of scales is only logarithmic, but this is still numerically important. We study a range of models and parameters, and find that in most cases these strings can be distinguished from cosmic strings that arise as gauge theory solitons.

Interactions of cosmic superstrings

“…This partly illuminates a puzzle discovered in [10], that there is a 1/v divergence in the fundamental string reconnection probability. Since the integrand in (3.14) universally contains the exponential of p 2z k z ∝ vk z , the integration over k z will result in an additional factor of 1/v (recall the original 1/v originated from the incoming strings' kinematic factor).…”

“…Such scattering was also studied by Khuri [8] finding that interaction is suppressed in the large-winding limit, whereas Mende used path integral saddle points [9] to show that for some special configurations it may still occur. Reconnection probabilities of wound superstrings were studied in [10], and further investigation into the effect of backgrounds was performed in [11].…”

Lumps in the throat

“…The precise metric is given by 25) which is almost of the form Eq. (4.2) as one would have expected except that in place of dx 2 we have a modified coordinate dx 2 − that captures the geometry 11 . This coordinate is related to x in the following way: 26) which also means that the harmonic function dependence for the seven brane is not the naively expected result.…”

“…Instead, a three-string junction of (p, q)-strings, as studied in section 2, is formed. Furthermore, for the case when intercommutation takes place, its probability may be significantly less than unity [11,53]. In [11] the intercommutation probabilities for F-F, D-D and F-D collisions in flat background were calculated.…”

“…When different types of cosmic superstrings intersect they cannot intercommute; instead they form junctions. This can have important consequences for the evolution of cosmic superstring networks [11,12,13]. In more realistic models of brane inflation in warped compactification, such as in [14], the spectrum of (p, q)-strings can be non-trivial [15,16].…”