Spherical collapse in Galileon models

Galileon models form a class of models where an additional scalar field is added to the Lagrangian describing the general theory of relativity. The addition of the scalar field causes a wide array of phenomena within our universe to change. Among those phenomena are both the expansion of the universe and the formation of large scale structures. We will study how they are both changed within a subclass of the Galileon models, called the Galileon ghost condensate models. First, we explore the parameter space of the model to find the values that give rise to non-singular evolu- tions of the expansion of the universe. Then, we examine how the large scale structures would form within those universes. To do that we use the spherical collapse model, in which the evolution of a spherical overden- sity is tracked. The spherical overdensity models how a relatively small perturbation leads to the formation of dark matter halos. We will show that the Galileon ghost condensate models still allow...Show moreGalileon models form a class of models where an additional scalar field is added to the Lagrangian describing the general theory of relativity. The addition of the scalar field causes a wide array of phenomena within our universe to change. Among those phenomena are both the expansion of the universe and the formation of large scale structures. We will study how they are both changed within a subclass of the Galileon models, called the Galileon ghost condensate models. First, we explore the parameter space of the model to find the values that give rise to non-singular evolu- tions of the expansion of the universe. Then, we examine how the large scale structures would form within those universes. To do that we use the spherical collapse model, in which the evolution of a spherical overden- sity is tracked. The spherical overdensity models how a relatively small perturbation leads to the formation of dark matter halos. We will show that the Galileon ghost condensate models still allow for a large degree of freedom within the spherical collapse, which would allow further research to constrain its parameter space.Show less

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Spherical collapse in Galileon models