COSALER · Cosmological consequences of Particle Physics models

Final Activity Report Summary - COSALER (Cosmological consequences of Particle Physics models)

Recent observations in astrophysics have become very precise and they enabled us to obtain a so-called 'standard cosmological model'. The constraints on the cosmological parameter values though will become much tighter in the near future, because of the new data that will be acquired through projects like Planck, Clover and CMBpol. On the other hand, the standard model of high energy physics is also extremely successful in its predictions, and the imminent new experiments in the large hadron collider (LHC) will provide us with further insights into particle physics. However, in spite of the success of both cosmology and high energy physics, little is known about the particle physics underlying the cosmological model. One of the most important challenges in physics during the coming years will be to identify the microscopic degrees of freedom of the early Universe and to reconcile them with data from cosmological observations. A promising connection between cosmology and high energy physics comes from cosmic defects. In fact, defects in cosmological phase transitions form quite generically in supersymmetric Grand unified theories (GUT) as well as in brane inflation models in string theory. Moreover, it was conjectured that fundamental superstring states might have direct analogies as soliton solutions in four-dimensional supergravity and these 'cosmic superstrings' could also have potentially measurable cosmological effects. In this project, we used high performance computers to carry out numerical simulations in order to study different kinds of cosmic defects. Our work enabled us to make predictions of the implications of the defects in the physics of the early universe. These objects were very complicated and intense numerical studies were necessary to understand their behaviour. We simulated some of the models predicting defects in big computers to see how they formed and evolved. Using our results we could compare the outcome with cosmological data to extract information regarding the early stages of the universe. Moreover, we were able to predict whether upcoming experiments would be accurate enough to answer some questions in a more definitive way and found that the Planck project would be able to distinguish cosmic strings from other possible effects in the cosmic microwave background, such as tensor modes. One of the project outcomes was that we found strong hints that the imprints of cosmic strings could be located in the cosmic microwave radiation. This was surprising because, although cosmic strings were in the mind of theoreticians for about 30 years, there was no experimental evidence related to them so far. Given that cosmic strings are relics of the very early Universe, they were anticipated to provide very valuable information to help construct a theory of all forces and particles. This result, published in a very high impact scientific journal, was also broadcasted by more general public media, such as BBC4 radio and electronic journals such as physorg.com, sciencedaily.com and newscientist.com

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