A simple model for explaining Galaxy Rotation Curves

A new simple expression for the circular velocity of spiral galaxies is proposed and tested against HI Nearby Galaxy Survey (THINGS) data set. Its accuracy is compared with the one coming from MOND.Comment: 9 pages, 3 figures, 2 tables; this article is connected to arXiv:1705.0413

Partial wave analysis of the Dirac fermions scattered from Schwarzschild black holes

Asymptotic analytic solutions of the Dirac equation, giving the scattering modes (of the continuous energy spectrum, $E>mc^2$) in Schwarzschild's chart and Cartesian gauge, are used for building the partial wave analysis of Dirac fermions scattered by black holes. The contribution of the bound states to absorption and possible resonant scattering is neglected because of some technical difficulties related to the discrete spectrum that is less studied so far. In this framework, the analytic expressions of the differential cross section and induced polarization degree are derived in terms of scattering angle, mass of the black hole, energy and mass of the fermion. Moreover, the closed form of the absorption cross section due to the scattering modes is derived showing that in the high-energy limit this tends to the event horizon area regardless of the fermion mass (including zero). A graphical study presents the differential cross section analyzing the forward/backward scattering (known also as glory scattering) and the polarization degree as functions of scattering angle. The graphical analysis shows the presence of oscillations in scattering intensity around forward/backward directions, phenomena known as spiral scattering. The energy dependence of the differential cross section is also established by using analytical and graphical methods.Comment: 34 page

Partial wave analysis of the Dirac fermions scattered from Reissner - Nordstr\" om charged black holes

The asymptotic form of Dirac spinors in the field of the Reissner-Nordstrom black hole are derived for the scattering states (with $E>mc^2$) obtaining the phase shifts of the partial wave analysis of Dirac fermions scattered from charged black holes. The elastic scattering and absorption are studied giving analytic formulas for the partial amplitudes and cross sections. A graphical study is performed for analysing the differential cross section (forward/backward scattering) and the polarization degree as functions of scattering angle.Comment: 6 two-column pages, 5 figures, a new figure with absorption included and new comment

Invited; Contact effects towards mainstream thin-film transistor applications

Thin-film source-gated transistors (SGTs) [1] have been developed steadily over the last couple of decades, demonstrating important properties which span virtually all thin-film material systems [2], [3]. By virtue of their control mechanism, which relies on an energy barrier deliberately engineered at the source, they present impressive intrinsic gain [4], [5], tolerance to variability [6], stability [7], and temperature sensing utility [8]. Recently, numerous groups have adopted the architecture [2], [3] and conceptual evolutions have led to new and highly functional TFT devices [9]–[11]. As the contact-controlled nature of these transistors introduces a relatively large temperature dependence of drain current, and also drastically reduces the current density, for a given geometry, recent research (Fig. 1-3) is focusing on shifting the balance away from these limitations [12]–[14], without compromising the structure’s advantages. Please click Download on the upper right corner to see the full abstract