Interactions of cosmic superstrings

Abstract

We develop methods by which cosmic superstring interactions can be studied in detail. These include the reconnection probability and emission of radiation such as gravitons or small string loops. Loop corrections to these are discussed, as well as relationships to (p, q)-strings. These tools should allow a phenomenological study of string models in anticipation of upcoming experiments sensitive to cosmic string radiation.

CMB constraints on cosmic strings and superstrings

“…1. Models of cosmic superstrings generally have suppressed intercommutation probabilities [45][46][47][48], which effectively reduces c r , and so they correspond to the purple region in the figure. Such networks have relativistic rms velocities v ∼ 1/ √ 2 and correlation lengths much smaller than the horizon, corresponding to a much higher string number density compared to ordinary string networks.…”

“…(2.15) is replaced by the corresponding self-interaction coefficient c i , and new cross-interaction terms with coefficients d k ij are added to describe zipping and unzipping. The coefficients c i , d k ij are controlled by the corresponding microphysical intercommuting probabilities P ij [52], which can be estimated [46,48] from the corresponding string theoretic amplitudes (and field theory approximations in the case of non-perturbative interactions between heavy strings [47]). They can be expressed as a product of two pieces: one that is dependent on the volume of the compact extra dimensions V ij (w, g s ), and a quantum interaction piece F ij (v, θ, g s ).…”

“…Notably, interacting networks of fundamental F-strings, one-dimensional D-branes (Dstrings), and bound (FD) strings, collectively referred to as cosmic superstrings, arise naturally in string theoretic inflation [7,43,44]. These networks are notably different to their simpler, single-type string counterparts since the different string types have intercommutation probabilities that are not necessarily unity [44][45][46][47][48][49][50]. The interactions among different string types are also much more complex, as colliding strings can zip together or unzip, producing heavier or lighter FD-string states carrying different charges.…”

Effect of kinematic constraints on multitension string network evolution

“…In the case of cosmic superstrings, for example, the interaction rules are well understood [25,43,44]. There are three possible outcomes of the crossing of a ðp; qÞ and a ðp 0 ; q 0 Þ string: they can either pass through one other or zip in two different ways, producing either a ðp þ p 0 ; q þ q 0 Þ or a ðp À p 0 ; q À q 0 Þ zipper segment.…”

“…This factor depends on the compactification and string coupling g s , and for different string types lies in different ranges, which have been investigated in detail in Refs. [43,44]. We will treat these factors as free parameters chosen in the appropriate ranges, which typically lie between 10 À3 d ðp;qÞ;ðp 0 ;q 0 Þ 1.…”