Physics / Fizik
Permanent URI for this collectionhttps://hdl.handle.net/11147/6
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Article Citation - WoS: 9Citation - Scopus: 9Is It Possible To Obtain Cosmic Accelerated Expansion Through Energy Transfer Between Different Energy Densities?(Elsevier Ltd., 2017) Erdem, RecaiThe equation of state of an energy density may be significantly modified by coupling it to another energy density. In the light of this observation we check the possibility of producing cosmic accelerated expansion in this way. In particular we consider the case where matter is converted to radiation (or vice versa by particle physics processes). We find that cosmic accelerated expansion can be obtained in this way only if an intermediate state with negative equation of state forms during the conversion.Article Citation - WoS: 1Citation - Scopus: 1Extra dimensions, dilaton and dark energy(Elsevier Ltd., 2011) Rador, TonguçIn view of the recent observations showing that the universe is accelerating we discuss dilaton and radion stabilization from a phenomenological perspective using perfect fluid sources. One general conclusion we present is that the pressure coefficient along extra dimensions should be -2 if that of the observed dimensions is -1, the latter mimicking a cosmological constant compatible with experimental data. The conditions on the dilaton coupling are similarly strong: we find that if the coupling of the dilaton Φ to fields other than gravity is of the form -ge(a-2)ΦL where L representing all other fields yielding the mentioned fluid, a must be -2 if space-time dimensionality is 10. Within our approach these conditions result taking constant radion and dilaton at the level of the equations of motion. To ameliorate this we also discuss how dynamical stabilization may be achieved with a simple variant in which a dilaton potential is added in the picture where the mentioned constraints are shown to remain.