Effect of Extra Dimensions on Gravitational Waves from Cosmic Strings

We show how the motion of cosmic superstrings in extra dimensions can modify the gravitational wave signal from cusps. Additional dimensions both round off cusps, as well as reducing the probability of their formation, and thus give a significant dimension dependent damping of the gravitational waves. We look at the implication of this effect for LIGO and LISA, as well as commenting on more general frequency bands.

Figure 1

A direct comparison with the DV plot [16], showing the GWB amplitude at $f=150\mathrm{Hz}$ as a function of $\alpha$. Solid lines show the interpolating function result, the dots correspond to exact numerical results. From top to bottom the plots are 3d DV in black, in red (dot-dashed) $n=1$, purple (dashed) $n=3$, and blue (dotted) $n=6$.

Figure 2

As Fig. 1, but with $f=3.9\mathrm{mHz}$ appropriate to the LISA detector.

Figure 3

A plot of the amplitude for LISA and LIGO with the modified measure (4) and $P={10}^{-3}$, fixing ${\Delta }_0={10}^{-3}$, and varying $n$. From top to bottom: the 3d result, and the extra dimension plots with $n=1$, 3, and 6, respectively.

Figure 4

A plot of the amplitude for LISA and LIGO with the modified measure (4) and $P={10}^{-3}$, varying ${\Delta }_0$ with fixed $n=3$. From top to bottom: the 3d DV result, then ${\Delta }_0={10}^{-4}$, ${10}^{-3}$, ${10}^{-2}$, and 0.1, respectively.