Семинар на 27.08.2015 г.

На 27 август 2015 г., от 13:15 ч. в зала 300 на ИЯИЯЕ Professor Eduardo Guendelman /Physics Department, Ben Gurion University, Beer Sheva, Israel/ ще изнесе доклад на тема:

"Dark Matter and Dark Energy from a Hidden Noether Symmetry, Cosmic Fluids and their K-essence Duals" (after joint works with Emil Nissimov and Svetlana Pacheva)

Abstract:

We show that dark energy and dark matter can be described simultaneously by ordinary Einstein gravity interacting with a single scalar field provided the scalar field Lagrangian couples in a symmetric fashion to two different spacetime volume-forms (covariant integration measure densities) on the spacetime manifold - one standard Riemannian given by the square-root of the determinant of the pertinent Riemannian metric and another non-Riemannian volume-form independent of the Riemannian metric, defined in terms of an auxiliary antisymmetric tensor gauge field of maximal rank. Integration of the equations of motion of the latter auxiliary gauge field produce an a priori arbitrary integration constant that plays the role of a dynamically generated cosmological constant or dark energy. Moreover, the above modified scalar field action turns out to possess a hidden Noether symmetry whose associated conserved current describes a pressureless "dust" fluid which we can identify with the dark matter completely decoupled from the dark energy. The form of both the dark energy and dark matter that results from above class of models is insensitive to the specific form of the scalar field Lagrangian. By adding very general perturbations, which breaks the above hidden symmetry and along with this it couples dark matter and dark energy we preserve the geodesic motion of the dust fluid, we also suggest a way to obtain growing dark energy in the present universe's epoch without evolution pathologies. Other variations of this model allow "K-essence" representations, in the Einstein frame.

 

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