Graphene coherent states

In this paper, we will construct the coherent states for a Dirac electron in graphene placed in a constant homogeneous magnetic field which is orthogonal to the graphene surface. First of all, we will identify the appropriate annihilation and creation operators. Then, we will derive the coherent states as eigenstates of the annihilation operator, with complex eigenvalues. Several physical quantities, as the Heisenberg uncertainty product, probability density and mean energy value, will be as well explored.Comment: 17 pages, 32 figure

Correlations and synchronization in a Bose-Fermi mixture

We study a Bose-Fermi mixture within the framework of the mean-field theory, including three possible regimes for the fermionic species: fully polarized, BCS, and unitarity. Starting from the 3D description and using the variational approximation (VA), we derive 1D and 2D systems of equations, under the corresponding confining potentials. This method produces a pair of nonlinear Schr\"{o}dinger (NLS) equations coupled to algebraic equations for the transverse widths of the confined state. The equations incorporate interactions between atoms of the same species and between the species, assuming that the latter can be manipulated by means of the Feshbach resonance (FR). As an application, we explore spatial density correlations in the ground state (GS) between the species, concluding that they strongly depend on the sign and strength of the inter-species interaction. Also studied are the dynamics of the mixture in a vicinity of the GS and the corresponding spatiotemporal inter-species correlation. The correlations are strongly affected by the fermionic component, featuring the greatest variation in the unitary regime. Results produced by the VA are verified by comparison with full numerical solutions.Comment: Journal of Physics B: Atomic, Molecular and Optical Physics, in pres

Audit market concentration and related regulatory measures

Audit markets are highly concentrated and such a situation might have negative consequences on competition, and thus, on price setting, on audit quality and on the functioning of markets. The European regulator recognized some causes for audit market concentration, identified a systemic risk and suggested joint audits and a mandatory rotation of audit firms to reduce concentration. Prominent concentration measures are concentration ratios, the Lorenz curve, the Gini-coefficient and the Herfindahl-Hirschman-Index. An empirical study on the concentration of German Prime Standard market for the period 2010 – 2013 revealed a high concentration which is quite stable over time and a narrow oligopoly with duopolistic tendencies. Nevertheless, competition could still work, e.g. due to the threat of market entrants. Moreover, given the fact that Big4 audit firms provide a higher audit quality, concentration may have positive effects. The mandatory audit firm rotation has a positive effect on auditor independence and a negative effect on auditor competence. This explains why related research output is inconclusive, i.e. the total effect on audit quality remains unclear. Moreover, a positive impact on competition is not ensured. Archival studies reveal that joint audits do not improve audit quality but increase audit costs. On the other hand, joint audits potentially reduce concentration. A combination between audit firm rotation and joint audits might be an optimal solution.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

N,N'-1,2-Phenylenebis[4-(chloromethyl)benzamide]

4 páginas, 1 esquema.-- This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution license.N,N'-1,2-Phenylenebis[4-(chloromethyl)benzamide] (3) was obtained in 61% yield by nucleophilic acyl substitution of 4-(chloromethyl)benzoyl chloride (2) with 1,2-phenylenediamine (1) under basic conditions. The title compound was characterized by FT-IR, 1H NMR, 13C NMR, low- and high-resolution EI-MS, and melting point.Peer reviewe