RESUMO
CONTEXT: In the realm of quantum chemistry, the accurate prediction of electronic structure and properties of nanostructures remains a formidable challenge. Density functional theory (DFT) and density matrix renormalization group (DMRG) have emerged as two powerful computational methods for addressing electronic correlation effects in diverse molecular systems. We compare ground-state energies ( e 0 ), density profiles ( n ), and average entanglement entropies ( S ¯ ) in metals, insulators and at the transition from metal to insulator, in homogeneous, superlattices, and harmonically confined chains described by the fermionic one-dimensional Hubbard model. While for the homogeneous systems, there is a clear hierarchy between the deviations, D % ( S ¯ ) < D % ( e 0 ) < D ¯ % ( n ) , and all the deviations decrease with the chain size; for superlattices and harmonic confinement, the relation among the deviations is less trivial and strongly dependent on the superlattice structure and the confinement strength considered. For the superlattices, in general, increasing the number of impurities in the unit cell represents lower precision in the DFT calculations. For the confined chains, DFT performs better for metallic phases, while the highest deviations appear for the Mott and band-insulator phases. This work provides a comprehensive comparative analysis of these methodologies, shedding light on their respective strengths, limitations, and applications. METHODS: The DFT calculations were performed using the standard Kohn-Sham scheme within the BALDA approach. It integrated the numerical Bethe-Ansatz (BA) solution of the Hubbard model as the homogeneous density functional within a local-density approximation (LDA) for the exchange-correlation energy. The DMRG algorithms were implemented using the ITensor library, which is based on the matrix product states (MPS) ansatz. The calculations were performed until the energy reaches convergence of at least 10 - 8 .
RESUMO
We investigate the Mott-Anderson physics in interacting disordered one-dimensional chains through the average single-site entanglement quantified by the linear entropy, which is obtained via density-functional theory calculations. We show that the minimum disorder strength required to the so-called full Anderson localization-characterized by the real-space localization of pairs-is strongly dependent on the interaction regime. The degree of localization is found to be intrinsically related to the interplay between the correlations and the disorder potential. In magnetized systems, the minimum entanglement characteristic of the full Anderson localization is split into two, one for each of the spin species. We show that although all types of localization eventually disappear with increasing temperature, the full Anderson localization persists for higher temperatures than the Mott-like localization.
RESUMO
We use entanglement to track the superfluid-insulator transition (SIT) in disordered fermionic superfluids described by the one-dimensional Hubbard model. Entanglement is found to have remarkable signatures of the SIT driven by i) the disorder strength V, ii) the concentration of impurities C and iii) the particle density n. Our results reveal the absence of a critical potential intensity on the SIT driven by V, i.e. any small V suffices to decrease considerably the degree of entanglement: it drops â¼50% for V = -0.25t. We also find that entanglement is non-monotonic with the concentration C, approaching to zero for a certain critical value CC. This critical concentration is found to be related to a special type of localization, here named as fully-localized state, which can be also reached for a particular density nC. Our results show that the SIT driven by n or C has distinct nature whether it leads to the full localization or to the ordinary one: it is a first-order quantum phase transition only when leading to full localization. In contrast, the SIT driven by V is never a first-order quantum phase transition independently on the type of localization reached.
RESUMO
Pneumatization in the osseous components of the temporomandibular joint (TMJ) may represent a complicating factor in TMJ surgery. This study determined the prevalence and characteristics of pneumatized articular eminence (PAE) and pneumatized glenoid fossa (PGF) using cone beam computed tomography (CBCT) scans of patients with and without dentofacial deformities. The CBCT of 587 asymptomatic patients (216 class I, 179 class II, 192 class III) were assessed to determine PAE and PGF. Age, sex, laterality, and type (uni/multilocular) of pneumatization were recorded. Differences were tested using the χ2 test and binary logistic regression models (P<0.05). Overall, 63.7% of patients presented some pneumatization: 15.5% presented both PAE and PGF, 0.9% presented only PAE, and 47.4% presented only PGF. The multilocular type was more frequent in both PAE and PGF (P<0.001). There was a significant difference regarding dentofacial deformity for PAE (P=0.021), with a higher frequency in class I. There were no differences according to sex, age, or laterality. The absence or lower frequency of pneumatization in class II and III patients may indicate continuous remodelling of the joint, which is submitted to abnormal occlusion forces. This knowledge is helpful for TMJ surgery planning, particularly as patients with dentofacial abnormalities may more often be candidates for TMJ surgery.
Assuntos
Deformidades Dentofaciais , Tomografia Computadorizada de Feixe Cônico , Humanos , Modelos Logísticos , Osso Temporal , Articulação TemporomandibularRESUMO
We investigate entanglement of strongly interacting fermions in spatially inhomogeneous environments. To quantify entanglement in the presence of spatial inhomogeneity, we propose a local-density approximation (LDA) to the entanglement entropy, and a nested LDA scheme to evaluate the entanglement entropy on inhomogeneous density profiles. These ideas are applied to models of electrons in superlattice structures with different modulation patterns, electrons in a metallic wire in the presence of impurities, and phase-separated states in harmonically confined many-fermion systems, such as electrons in quantum dots and atoms in optical traps. We find that the entanglement entropy of inhomogeneous systems is strikingly different from that of homogeneous systems.
RESUMO
Solanum lycocarpum St. Hill (SL) is commonly used in Brazilian folk medicine. The aim of the present study was to evaluate the validity of the traditional therapeutic indication of SL as hypoglycaemic agent. The extract reduced glycemia to 92.4mg/dl in alloxan induced diabetic rats (230.5mg/dl). We also investigated the potential of SL as antioxidant (it reduced in 27% nitrate generation in diabetic animals). Our results also demonstrated that SL is not ulcerogenic and restored haemoglobin and haematocrit to normal values in diabetic animals.