Finite-time singularities in f(R, T) gravity and the effect of conformal anomaly

We investigate $f(R,T)$ gravity models ($R$ is the curvature scalar and $T$ is the trace of the stress-energy tensor of ordinary matter) that are able to reproduce the four known types of future finite-time singularities. We choose a suitable expression for the Hubble parameter in order to realise the cosmic acceleration and we introduce two parameters, $\alpha$ and $H_s$, which characterise each type of singularity. We address conformal anomaly and we observe that it cannot remove the sudden singularity or the type IV one, but, for some values of $\alpha$, the big rip and the type III singularity may be avoided. We also find that, even without taking into account conformal anomaly, the big rip and the type III singularity may be removed thanks to the presence of the $T$ contribution of the $f(R,T)$ theory.Comment: 18 pages; Accepted for publication in Canadian Journal of Physics (CJP

Aging of a nanostructured Zn50Se50 alloy produced by mechanical alloying

The aging of a nanocrystalline equiatomic ZnSe alloy produced by mechanical alloying was investigated using X-ray diffraction (XRD) and differential scanning calorimetry (DSC) techniques. The measured XRD patterns showed that Se atoms located at interfacial component migrated with aging giving raise to a crystalline selenium (c-Se) phase. DSC spectra of heat-treated samples at temperatures above 221oC followed by quenching showed that the c-Se particles changed to the amorphous state. It was also observed that the as-milled and aged samples are highly hydrophilic. The lattice parameters and the average crystallite sizes were calculated as a function of time of aging and temperature of heat treatment.Comment: Submitted to Solid State Communications, 4 figure