Universo desitter desde los efectos cua nticos en modelos de gravitacio n dilato nica y modelos de energia oscura

In this paper a quantum N = 4 super Yang-Mills theory perturbed by dilatoncoupled scalars, is considered. It is shown that, depending on the initial conditions for the dilaton, the dilaton may slow down, or accelerate, the inflation process. At late times, the dilaton is decaying exponentially. At the end of this work, the question how the perturbation of the solution for the scale factor a ects the stability of the solution for the equations of motion and therefore the stability of the Inflationary Universe, which could be eternal, is considered. From another hand a dark energy cosmology model in a de Sitter universe filled with quantum conformal matter is considered. Our model represents a Gauss-Bonnet model of gravity with contributions from quantum e ects. To the General Relativity action an arbitrary function of the GB invariant, f (G), is added, and taking into account quantum e ects from matter the cosmological constant is studied. For the considered model the conditions for a vanishing cosmological constant are considered. Creation of a de Sitter universe by quantum e ects in a GB modified gravity is discussed. Se construye una cosmolog´ýa cu´antica con base en la teor´ýa supersim´etrica del campo N = 4 Yang-Mills en interacci´on con la gravitaci´on dilat´onica. En el marco de la teor´ýa en consideraci´on se analiza la estabilidad y se demuestra que la inflaci´on presenta un comportamiento estable. De otro lado, es estudiado un modelo cosmol´ogico de energ´ýa oscura en un universo deSitter compuesto de materia cu´antica conforme. Este modelo representa un moelo de gravedad modificada de Gauss-Bonnet perturbada por efectos cu´anticos. Adicionando a la acci´on de la relatividad general una funci´on arbitraria del invariante de GB, f (G) y considerando los efectos cu´anticos de la materia, se estudia la constante cosmol´ogica. Para el modelo en consideraci´on, se investigan las condiciones de desaparici´on de la constante cosmol´ogica. Se discute el origen de un Universo deSitter por efectos cu´anticos en un modelo de gravedad modificada de GB.