A cosmic string has very interesting physical effects. All these effects are originated from its unique way to deform the space-time around it. A model of an infinitely long, straight cosmic string is one of the exactly solvable systems in General Relativity. Since it is made of vacuum energy rather than ordinary matter, it has different solution of the Einstein equations, a conic space-time!
Figure 4. Conic space-time formed around a straight string, One
complete turn around the string makes up less than 
by the deficit angle
.
The metric around a straight string is given by (in cylindrical
coordinates)
where 
is the cosmic string parameter (G=Newton
constant, 
= string energy density). It is a
flat space-time metric except for the deficit angle
.
Motion of a cosmic string can be described by Nambu-Goto action:
and it satisfies wave equation. Cosmic strings are expected to have
huge tension. Tension ~ mass density are in a natural unit so their
motions are relativistic.
Possible
Physical Effects:
(1) Double Images
(2)
Kaiser-Stebbins Effect
(3) Wakes
(4) Gravitational Wave Radiation
Figure 5. Physical effects by cosmic strings. Kaiser-Stebbins effect,
double image, and wake are due to conic space-time around cosmic string.
Radiation of gravitational waves is a generic phenomenon by
time-varying fluctuation of the metric, especially around the cusp.
Kaiser-Stebbins effect is explained in
the next page in more detail.