We investigate the physical meaning of some of the texture zeros which appear in most of the Ansatze on leptonic masses and their mixing. It is shown that starting from arbitrary lepton mass matrices and making suitable weak basis transformations one
can obtain some of these sets of zeros, which therefore have no physical content. We then analyse four-zero texture Ansatze where the charged lepton and neutrino mass matrices have the same structure. The four texture zeros cannot be obtained simultaneously through weak basis transformations, so these Ansatze do have physical content. We show that they can be separated into four classes and study the physical implications of each class.
A simple model of quintessential inflation with the modified exponential potential $e^{-alpha phi} [A+(phi-phi_0)^2]$ is analyzed in the braneworld context. Considering reheating via instant preheating, we conclude that the model exhibits transient a
cceleration at late times for $0.96 lesssim A alpha^2 lesssim 1.26$ and $271 lesssim phi_0 alpha lesssim 273$, while permanent acceleration is obtained for $2.3times10^{-8} lesssim A alpha^2 lesssim 0.98$ and $255 lesssim phi_0 alpha lesssim 273$. The steep parameter $alpha$ is constrained to be in the range $5.3 lesssim alpha lesssim 10.8$.
A simple model of quintessential inflation with the modified exponential potential exp(-alpha phi) [A + (phi-phi_0)^2] is analyzed in the braneworld context. Considering reheating via instant preheating, it is shown that the evolution of the scalar f
ield phi from inflation to the present epoch is consistent with the observational constraints in a wide region of the parameter space. The model exhibits transient acceleration at late times for 0.96 < A alpha^2 < 1.26 and 271 < phi_0 alpha < 273, while permanent acceleration is obtained for 2.3 10^{-8} < A alpha^2 < 0.98 and 255 < phi_0 alpha < 273. The steep parameter alpha is constrained to be in the range 5.3 < alpha < 10.8.
