An international group of scientists from Ligo, Virgo and Kagra established the most stringent restrictions on mysterious space strings – topological defects of space-time, which still elude researchers. The results assist to understand what characteristics the space strings should have if they really exist. This is reported in the article published in the magazine Physical Review Letters.
Field theories predict that as the Universe expanded and its temperature fell, it had to undergo a series of phase transitions, followed by a spontaneous violation of symmetries that could leave after themselves topological defects. One-dimensional topological defects are called cosmic strings. Although the models of the physics of elementary particles predict the existence of cosmic strings, there are currently no confirmation of their existence.
cosmic strings must be sufficiently massive, but a large mass corresponds to a significant gravitational effect. The gravitational wave detectors are capable of fixing the signs of the existence of cosmic strings, as well as other phenomena, which is not available for conventional particle accelerators.
At the moment there are two possible numerical simulations of cosmic strings loops. In the new work, scientists have developed a model that interpolates between the two previous, and used it to analyze the gravitational waves data from the last series of Observation of the LIGO / VIRGO / KAGRA collaboration. They tried to fix the gravitational wave signals arising due to the topological features of cosmic strings, such as protrusions, gentlements, as well as phenomena in which two inflection faces. With the help of a numerical model, researchers managed to limit the string tension as the function of the number of protrusions or beggars, whose value should be less than or approximately 4, multiplied by 10 per minus 15th degree.
As the authors write, in the case of cosmic strings formed at the end of inflation (the period of exponential expansion of the universe), these results challenge simple inflationary models describing the universe in the first moments after a large explosion.