Mott-Hubbard quantum criticality in paramagnetic CMR pyrochlores

We present a correlated {\it ab initio} description of the paramagnetic phase of Tl$_2$Mn$_2$O$_7$, employing a combined local density approximation (LDA) with multiorbital dynamical mean field theory (DMFT) treatment. We show that the insulating state observed in this colossal magnetoresistance (CMR) pyrochlore is determined by strong Mn intra- and inter-orbital local electron-electron interactions. Hybridization effects are reinforced by the correlation-induced spectral weight transfer. Our result coincides with optical conductivity measurements, whose low energy features are remarkably accounted for by our theory. Based on this agreement, we study the disorder-driven insulator-metal transition of doped compounds, showing the proximity of Tl$_2$Mn$_2$O$_7$ to quantum phase transitions, in agreement with recent measurements.Comment: 4 pages, 4 figure

Special issue of international journal of molecular sciences “opioid receptors and endorphinergic systems 2.0”

: Opioid peptides exhibit a wide-ranging tissue distribution and control multiple tissue functions not only through reflex mechanisms involving the central nervous system or the modulation of neurotransmitter release, but also by acting directly at the cellular level by targeting selected receptor subtypes (μ, δ, and κ are among the most frequently expressed) [...]

Modeling lithium rich carbon stars in the Large Magellanic Cloud: an independent distance indicator ?

We present the first quantitative results explaining the presence in the Large Magellanic Cloud of some asymptotic giant branch stars that share the properties of lithium rich carbon stars. A self-consistent description of time-dependent mixing, overshooting, and nuclear burning was required. We identify a narrow range of masses and luminosities for this peculiar stars. Comparison of these models with the luminosities of the few Li-rich C stars in the Large Magellanic Cloud provides an independent distance indicator for the LMCComment: 7 pages, 2 figure

Diffusive convective overshoot in core He-burning intermediate mass stars. I: the LMC metallicity

We present detailed evolutionary calculations focused on the evolution of intermediate mass stars with 3 Msun < M < 9 Msun of metallicity typical of the Large Magellanic Cloud (LMC), i.e. Z=0.008. We compare carefully the models calculated by adopting a diffusive scheme for chemical mixing, in which nuclear burning and mixing are self-consistently coupled, while the eddy velocities beyond the formal convective core boundary are treated to decay exponentially, and those calculated with the traditional instantaneous mixing approximation. We find that: i) the physical and chemical behaviour of the models during the H-burning phase is independent of the scheme used for the treatment of mixing inside the CNO burning core; ii) the duration of the He-burning phase relative to the MS phase is systematically longer in the diffusive models, due to a slower redistribution of helium to the core from the outer layers; iii) the fraction of time spent in the blue part of the clump, compared to the stay in the red, is larger in the diffusive models. The differences described in points ii) and iii) tend to vanish for M > Msun. In terms of the theoretical interpretation of an open cluster stellar population, the differences introduced by the use of a self-consistent scheme for mixing in the core with adjacent exponential decay are relevant for ages in the range 80 Myr < t < 200 Myr. These results are robust, since they are insensitive to the choice of the free-parameters regulating the extension of the extra-mixing region.Comment: 14 pages, 14 figure, accepted for publication on Astronomy & Astrophysic