The Hubbard model with spin orbit coupling: a lattice gauge theory approach

We study the symmetry properties of the Hubbard model with spin-orbit interactions of Rashba and Dresselhaus type. These interactions break the rotational symmetry in spin space, so that the magnetic order cannot be excluded by using the Bogoliubov inequality method. Nevertheless, we rigorously show that the existence of the magnetic long-range orders may be ruled out when the Rashba and Dresselhaus coupling constants are equal in modulus, whereas the eta-pairing can be always ruled out, regardless of the microscopic parameters of the model. These results are obtained by imposing locally the SU(2) gauge symmetry on the lattice, and rewriting the spin-orbit interactions in such a way that they are included in the path ordered of the gauge field on lattice.Comment: 7 page

Phase transitions in strongly correlated electronic systems

2012 - 2013We studied the some type of phase transitions in Strongly Correlated Electronic Systems. In particular we rigorously established some exact properties of a multi-orbital Hubbard model, here formulated to describe a nematic phase transition. In the first step, using Bogoliubov’s inequality, we rigorously showed that the multiorbital Hubbard model with narrow bands, eventually in the presence of the spin-orbit coupling, does not exhibit long-range nematic order, in the low dimensions. This result holds at any finite temperature for both repulsive and attractive on-site Coulomb interactions, with and without spin-orbit coupling. In the following step, using the reflection positivity method, we showed that this model supports a staggered nematic order if repulsive or attractive on-site inter-orbital and intra-orbital interactions and off-site repulsive inter-orbital interaction are considered. Depending on the dimensions of the lattice where the model is defined, the order may or not may exist. Indeed, in three dimensions the order may exist at finite temperature, and we get the condition for its existence finding out an upper bound for the critical temperature. On the other hand, for two dimensional lattices, the order may exist at least in the ground state, if the hopping amplitude is small enough. Furthermore, in the final step, we studied the symmetry properties of the non-degenerate Hubbard model with spin-orbit interactions of Rashba and Dresselhaus type. These interactions break the rotational symmetry in spin space, so that the magnetic order cannot be excluded by using the Bogoliubov inequality method. Nevertheless, we rigorously show that the existence of the magnetic long-range orders may be ruled out when the Rashba and Dresselhaus coupling constants are equal in modulus, whereas the -pairing can be always ruled out, regardless of the microscopic parameters of the model. These results are obtained by imposing locally the SU(2) gauge symmetry on the lattice, and rewriting the spin-orbit interactions in such a way that they are included in the path ordered of the gauge field on lattice. [edited by author]XII n.s

4D Topological Mass by Gauging Spin

We propose a spin gauge field theory in which the curl of a Dirac fermion current density plays the role of the pseudovector charge density. In this field-theoretic model, spin interactions are mediated by a single scalar gauge boson in its antisymmetric tensor formulation. We show that these long range spin interactions induce a gauge invariant photon mass in the one-loop effective action. The fermion loop generates a coupling between photons and the spin gauge boson, which acquires thus charge. This coupling represents also an induced, gauge invariant, topological mass for the photons, leading to the Meissner effect. The one-loop effective equations of motion for the charged spin gauge boson are the London equations. We propose thus spin gauge interactions as an alternative, topological mechanism for superconductivity in which no spontaneous symmetry breaking is involved.Comment: 4 pages, no figures. arXiv admin note: substantial text overlap with arXiv:1310.210

The QuIC: Quantitative Intellectual Capital-based methodology for Firm Valuation

The paper proposes a new methodology for evaluating the market value of firms (QuIC – Quantitative Intellectual Capital-based methodology for Firm Valuation) that considers Intellectual Capital (IC) as an important factor that can influence the overall value. Findings show that this approach gives a more fair evaluation able of taking account of the “hidden” value that could remain unconsidered when applying “traditional” valuation approaches. In fact, findings demonstrated that, from a financial standpoint, the difference between DCF and QuIC evaluation can be recognised as the worth of intellectual capital assets

Immigrants in agricultural sector in Sicily: the experience of Sicilia Integra project

The overview of the most relevant literature on migration, whose main issues were human rights, work in agriculture, cultural and social inclusion, highlighted one common point: the need to foster the legal work of migrants as a driver for social integration. This finding was confirmed by a CREA-PB survey that, after outlining the role of foreign workers in Sicilian agriculture, has emphasised how their state of isolation derived mainly from their bad housing conditions directly connected to illegal employment. The evaluation of the project “Sicilia Integra”, which was born under the patronage of the UN to include young immigrants in urban agriculture activities in Sicily, was carried out through the SWOT methodology for verifying if it could be spread in the Sicilian region

Alcohol Septal Ablation in Patients with Hypertrophic Obstructive Cardiomyopathy: A Contemporary Perspective

Alcohol septal ablation is a minimally invasive procedure for the treatment of left ventricular outflow tract (LVOT) obstruction in patients with hypertrophic obstructive cardiomyopathy (HOCM) who remain symptomatic despite optimal medical therapy. The procedure causes a controlled myocardial infarction of the basal portion of the interventricular septum by the injection of absolute alcohol with the aim of reducing LVOT obstruction and improving the patient's hemodynamics and symptoms. Numerous observations have demonstrated the efficacy and safety of the procedure, making it a valid alternative to surgical myectomy. In particular, the success of alcohol septal ablation depends on appropriate patient selection and the experience of the institution where the procedure is performed. In this review, we summarize the current evidence on alcohol septal ablation and highlight the importance of a multidisciplinary approach involving a team of clinical and interventional cardiologists and cardiac surgeons with high expertise in the management of HOCM patients-the Cardiomyopathy Team

An optical coherence tomography-based grading of diabetic maculopathy proposed by an international expert panel: The European School for Advanced Studies in Ophthalmology classification.

Aims:To present an authoritative, universal, easy-to-use morphologic classification of diabetic maculopathy based on spectral domain optical coherence tomography.Methods:The first draft of the project was developed based on previously published classifications and a literature search regarding the spectral domain optical coherence tomography quantitative and qualitative features of diabetic maculopathy. This draft was sent to an international panel of retina experts for a first revision. The panel met at the European School for Advanced Studies in Ophthalmology headquarters in Lugano, Switzerland, and elaborated the final document.Results:Seven tomographic qualitative and quantitative features are taken into account and scored according to a grading protocol termed TCED-HFV, which includes foveal thickness (T), corresponding to either central subfoveal thickness or macular volume, intraretinal cysts (C), the ellipsoid zone (EZ) and/or external limiting membrane (ELM) status (E), presence of disorganization of the inner retinal layers (D), number of hyperreflective foci (H), subfoveal fluid (F), and vitreoretinal relationship (V). Four different stages of the disease, that is, early diabetic maculopathy, advanced diabetic maculopathy, severe diabetic maculopathy, and atrophic maculopathy, are based on the first four variables, namely the T, C, E, and D. The different stages reflect progressive severity of the disease.Conclusion:A novel grading system of diabetic maculopathy is hereby proposed. The classification is aimed at providing a simple, direct, objective tool to classify diabetic maculopathy (irrespective to the treatment status) even for non-retinal experts and can be used for therapeutic and prognostic purposes, as well as for correct evaluation and reproducibility of clinical investigations

Cx26 partial loss causes accelerated presbycusis by redox imbalance and dysregulation of Nfr2 pathway.

Mutations in GJB2, the gene that encodes connexin 26 (Cx26), are the most common cause of sensorineural hearing impairment. The truncating variant 35delG, which determines a complete loss of Cx26 protein function, is the prevalent GJB2 mutation in several populations. Here, we generated and analyzed Gjb2+/- mice as a model of heterozygous human carriers of 35delG. Compared to control mice, auditory brainstem responses (ABRs) and distortion product otoacoustic emissions (DPOAEs) worsened over time more rapidly in Gjb2+/- mice, indicating they were affected by accelerated age-related hearing loss (ARHL), or presbycusis. We linked causally the auditory phenotype of Gjb2+/- mice to apoptosis and oxidative damage in the cochlear duct, reduced release of glutathione from connexin hemichannels, decreased nutrient delivery to the sensory epithelium via cochlear gap junctions and deregulated expression of genes that are under transcriptional control of the nuclear factor erythroid 2-related factor 2 (Nrf2), a pivotal regulator of tolerance to redox stress. Moreover, a statistically significant genome-wide association with two genes (PRKCE and TGFB1) related to the Nrf2 pathway (p-value < 4\u202f 7 10-2) was detected in a very large cohort of 4091 individuals, originating from Europe, Caucasus and Central Asia, with hearing phenotype (including 1076 presbycusis patients and 1290 healthy matched controls). We conclude that (i) elements of the Nrf2 pathway are essential for hearing maintenance and (ii) their dysfunction may play an important role in the etiopathogenesis of human presbycusis