Valley polarization effects on the localization in graphene Landau levels

Effects of disorder and valley polarization in graphene are investigated in the quantum Hall regime. We find anomalous localization properties for the lowest Landau level (LL), where disorder can induce wavefunction delocalization (instead of localization), both for white-noise and gaussian-correlated disorder. We quantitatively identify the contribution of each sublattice to wavefunction amplitudes. Following the valley (sublattice) polarization of states within LLs for increasing disorder we show: (i) valley mixing in the lowest LL is the main effect behind the observed anomalous localization properties, (ii) the polarization suppression with increasing disorder depends on the localization for the white-noise model, while, (iii) the disorder induces a partial polarization in the higher Landau levels for both disorder models.Comment: 5 pages, 6 figures, extended version, with 2 new figures adde

Strictly Positive Definite Kernels on a Product of Spheres II

We present, among other things, a necessary and sufficient condition for the strict positive definiteness of an isotropic and positive definite kernel on the cartesian product of a circle and a higher dimensional sphere. The result complements similar results previously obtained for strict positive definiteness on a product of circles [Positivity, to appear, arXiv:1505.01169] and on a product of high dimensional spheres [J. Math. Anal. Appl. 435 (2016), 286-301, arXiv:1505.03695]

Resonant tunneling through protected quantum dots at phosphorene edges

We theoretically investigate phosphorene zigzag nanorribons as a platform for constriction engineering. In the presence of a constriction at the upper edge, quantum confinement of edge protected states reveals resonant tunnelling Breit-Wigner transmission peaks, if the upper edge is uncoupled to the lower edge. Coupling between edges in thin constrictions gives rise to Fano-like and anti-resonances in the transmission spectrum of the system.Comment: 8 pages,7 figure

A singular structure: Monopost made in composites

p. 3002-3012This work presents the design process, the analysis, and the performance of a cylindrical hollow monopost, made entirely in composites. It is about a translucent structure of height 40m, external diameter 1.60m and the average wall-thickness 11mm. The material is a polymer made up of vinylster resin and reinforced by glass fiber (GFRP). The manufactured processing used is filament winding. Moreover, due to geographical emplacement where it is situated, the structure has to support wind velocity value above 180Km/h and its elastic modulus of the material does not exceed 25GPa. Eventually, we was able to achieve an optimum solution and strentgh structure, considering and developing differents types of approaches and analysis, such as linear, non-linear and buckling.Rovira, JA.; Martin, P.; Pons, D.; Almerich Chulia, AI. (2009). A singular structure: Monopost made in composites. Editorial Universitat Politècnica de València. http://hdl.handle.net/10251/670

Correlating features in the primordial spectra

Heavy fields coupled to the inflaton reduce the speed of sound in the effective theory of the adiabatic mode each time the background inflationary trajectory deviates from a geodesic. This can result in features in the primordial spectra. We compute the corresponding bispectrum and show that if a varying speed of sound induces features in the power spectrum, the change in the bispectrum is given by a simple formula involving the change in the power spectrum and its derivatives. In this manner, we provide a uniquely discriminable signature of a varying sound speed for the adiabatic mode during inflation that indicates the influence of heavy fields. We find that features in the bispectrum peak in the equilateral limit and, in particular, in the squeezed limit we find considerable enhancement entirely consistent with the single field consistency relation. From the perspective of the underlying effective theory, our results generalize to a wide variety of inflationary models where features are sourced by the time variation of background quantities. A positive detection of such correlated features would be unambiguous proof of the inflaton's nature as a single light scalar degree of freedom embedded in a theory that is UV completable.Comment: 5 pages, 1 figure; matches published versio

Judicial Risk and Credit Market Performance: Micro Evidence from Brazil Payroll Loans

A large body of literature has stressed the institution-development nexus as critical in explaining differences in countries' economic performance. The empirical evidence, however, has been mainly at the aggregate level, associating macro performance with measures of quality of institutions. This paper, by relating a judicial decision on the legality of payroll debit loans in Brazil to bank-level decision variables, provides micro evidence on how creditor legal protection affects market performance. Payroll loans are personal loans with principal and interests payments directly deducted from the borrowers' payroll check, which, in practice, makes a collateral out of future income. In June 2004, a high-level federal court upheld a regional court ruling that had declared payroll deduction illegal. Using personal loans without payroll deduction as a control group, we assess whether the ruling had an impact on market performance. Evidence indicates that it had an adverse impact on risk perception, interest rates, and amount lent.