Scale Factor Self-Dual Cosmological Models

We implement a conformal time scale factor duality for Friedmann-Robertson-Walker cosmological models, which is consistent with the weak energy condition. The requirement for self-duality determines the equations of state for a broad class of barotropic fluids. We study the example of a universe filled with two interacting fluids, presenting an accelerated and a decelerated period, with manifest UV/IR duality. The associated self-dual scalar field interaction turns out to coincide with the "radiation-like" modified Chaplygin gas models. We present an equivalent realization of them as gauged K\"ahler sigma models (minimally coupled to gravity) with very specific and interrelated K\"ahler- and super-potentials. Their applications in the description of hilltop inflation and also as quintessence models for the late universe are discussed.Comment: v3, improved and extended version to be published in JHEP; new results added to sect.2; 4 figures; 17pg

Cultura do sorgo sacarino.

Só existe crise para usineiro quando a usina está parada. Esta foi a frase que ouvi outro dia de um encarregado de campo em uma usina. A entressafra de cana-de-açúcar em Alagoas está chegando ao fim. Depois de um período que se estendeu desde março/abril, usinas como Santo Antonio e Camaragibe já anunciam o início da safra para os próximos dias.bitstream/item/123122/1/17-cultura-do-sorgo.pd