Question

what is cosmic string theory ?​

Answer 1

Cosmic strings are objects that may have formed in the early Universe, but scientists are still searching for
evidence that they exist. They were first introduced by theoretical physicist Tom W. B. Kibble in the late 70s
as a possible result of some field theories, including the famous Higgs theory. They are one-dimensional
(line-like) objects, similar to vortex lines in liquid helium, that could be left over after the early Universe went
through a phase transition. Cosmic strings were a popular research topic in the 80s, since they could have
triggered the formation of large-scale structures such as galaxies. However, the presence of cosmic strings
in the early universe would leave an imprint in the cosmic microwave background (CMB) Space-based
experiments like COBE and WMAP revealed that cosmic strings do not make a measurable contribution to
the CMB, thus ruling out a significant role for cosmic strings.
Cosmic strings were revisited in the early 2000s
when it was realized that they could also form in
the context of string theory. In a string theory,
elementary particles are described by tiny one-
dimensional objects in a multi-dimensional space.
In some theories, the strings could grow to
cosmological scales and behave like historical
cosmic strings. These are called cosmic
superstrings, and could provide precious
observational signatures of string theory.
Assuming they do exist, the network of cosmic
(super)strings formed in the early Universe would
have evolved as the Universe expanded: strings
stretched, interacted, oscillated, disintegrated...
Massive computer simulations can describe this
evolution from formation up to today, but they are
challenging because many physical effects need
to be taken into account. Some assumptions and
simplifications are necessary to keep the
simulation at a reasonable scale to be run by
computers. An example of such a simulation is
shown on the right.

Answer 2

this is cosmic string which never joined to other