1202.4487 (R J Slagter et al.)

Warped Self-Gravitating U(1) Gauge Cosmic Strings in 5D    [PDF]

R J Slagter, D Masselink

We present the "classical" Nielsen-Olesen vortex solution on a warped five
dimensional space time, where we solved the effective four-dimensional
equations from the five-dimensional equations together with the junction and
boundary conditions. Four dimensional cosmic strings show some serious problems
concerning the mechanism of string smoothing related to the string mass per
unit length, $G\mu \leq 10^{-6}$. Moreover, there is no observational evidence
of axially symmetric lensing effect caused by cosmic strings. Also
super-massive cosmic strings ($G\mu\gtrsim 1$), predicted by superstring
theory, possess some problems. They are studied because the universe may have
undergone phase transitions at scales much higher than the GUT scale. But $G\mu
\gtrsim 1$ is far above observational bounds, so one needs an inflationary
scenario to smooth them out. Further, it is believed that these super-massive
strings could never have extended to macroscopic size. Brane-world models could
overcome these problems. $G\mu$ could be warped down to GUT scale, even if its
value was at the Planck scale.
In our warped cosmic string model, where the string mass per unit length in
the bulk can be of order of the Planck scale, we find that the four dimensional
brane space time is exponential warped down. Moreover, asymptotically the
induced four dimensional space time is always degenerated, so has an
unobservable angle deficit compared to its value in the bulk. There is no
conical structure and the space time seems to be un-physical, at least under
fairly weak assumptions on the stress-energy tensor and without a positive
brane tension. The results are confirmed by numerical solutions of the field
equations.

View original: http://arxiv.org/abs/1202.4487