A large class of particle physics models beyond the 
"Standard Model" admit solutions which are linear 
topological defects. If Nature is described by such 
models, then inevitably such defects will form in 
the early universe and will persist to the present 
time. These are the cosmic strings. Cosmic strings 
are linear of trapped energy density, and their 
gravitational effects lead to signatures in a wide 
range of observational windows.
