22,436 research outputs found
de Broglie-Proca and Bopp-Podolsky massive photon gases in cosmology
We investigate the influence of massive photons on the evolution of the
expanding universe. Two particular models for generalized electrodynamics are
considered, namely de Broglie-Proca and Bopp-Podolsky electrodynamics. We
obtain the equation of state (EOS) for each case using
dispersion relations derived from both theories. The EOS are inputted into the
Friedmann equations of a homogeneous and isotropic space-time to determine the
cosmic scale factor . It is shown that the photon non-null mass does not
significantly alter the result valid for a massless photon
gas; this is true either in de Broglie-Proca's case (where the photon mass
is extremely small) or in Bopp-Podolsky theory (for which is extremely
large).Comment: 8 pages, 2 figures; v2 matches the published versio
Comparative gene expression study to identify genes possibly related to storage root formation in cassava.
Pt2L4 protein, a homologue to Hev b 5 from rubber tree, may not be responsible for the cross-reactions to cassava show by peope allergic to latex.
Classificação de colônias de Melipona Scutellaris latreille, 1811, (Hymenoptera: apidae) utilizando o índice soma de Ranks.
Parâmetros biométricos de colônias de Melipona scutellaris Latreille, 1811 (Hymenoptera: apidae) em diferentes gerações.
Seleção de espécies florestais para utilização em sistemas agroflorestais em Manaus, AM.
O objetivo deste trabalho foi testar o desempenho em crescimento das espécies Paricá, Taxi-branco, Sumaúma e Ucuúba visando sua possível utilização como componentes de sistemas agroflorestais na região
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