Inhomogeneous longitudinal electric field-induced anomalous Hall conductivity in a ferromagnetic two-dimensional electron gas

It is known that the anomalous Hall conductivity (AHC) in a disordered two dimensional electron system with Rashba spin-orbit interaction and finite ferromagnetic spin-exchange energy is zero in the metallic weak-scattering regime because of the exact cancellation of the bare-bubble contribution by the vertex correction. We study the effect of inhomogeneous longitudinal electric field on the AHC in such a system. We predict that AHC increases from zero (at zero wavenumber), forms a peak, and then decreases as the wavenumber for the variation of electric field increases. The peak-value of AHC is as high as the bare-buble contribution. We find that the wave number, q, at which the peaks occur is the inverse of the geometric mean of the mean free path of an electron and the spin-exchange length scale. Although the Rashba energy is responsible for the peak-value of AHC, the peak position is independent of it.Comment: 5 pages, 4 figure

Engagement at a Distance: Reflections on Student Learning and Parent Engagement in a Physics Classroom

New technology, including online gradebooks and learning management systems, allow schools to remotely involve families in their children\u27s educations. This engagement at a distance , as well as its impact on student learning, is examined through the lens of the author\u27s experiences as a student-teacher. It is argued that while a holistic and meaningful form of family engagement is ideal, engagement at a distance is more detrimental to student learning than no engagement at all

Site percolation in distorted square and simple cubic lattices with flexible number of neighbors

This paper exhibits a Monte Carlo study on site percolation using the Newmann-Ziff algorithm in distorted square and simple cubic lattices where each site is allowed to be directly linked with any other site if the euclidean separation between the pair is at most a certain distance d, called the connection threshold. Distorted lattices are formed from regular lattices by a random but controlled dislocation of the sites with the help of a parameter {\alpha}, called the distortion parameter. The distinctive feature of this study is the relaxation of the restriction of forming bonds with only the nearest neighbors. Owing to this flexibility and the intricate interplay between the two parameters {\alpha} and d, the site percolation threshold may either increase or decrease with distortion. The dependence of the percolation threshold on the average degree of a site has been explored to show that the obtained results are consistent with those on percolation in regular lattices with extended neighborhood and continuum percolation.Comment: 9 pages, 6 figures, Accepted in Phys. Rev.

Necrosis and myelomalaic lesions in acute experimental allergic encephalomyelitis in guinea pigs

Background: Multiple Sclerosis (MS) and its animal model Experimental Allergic Encephalomyelitis (EAE) is an inflammatory demyelinating disease of the central nervous system, in which the myelin sheath has been considered to be the primary target for many years. However, an increasing number of reports have focused on neurodegenerative aspects of the disease pathogenesis. Damage to axons is taken as a key factor of disability in multiple sclerosis, but its pathogenesis is largely unknown. Axonal injury is believed to occur as a consequence of demyelination and was recently shown to be a feature even of the early disease stages. It is evident that the crucial distinction between primary and secondary demyelination depends on the preservation or the destruction of the axons and the neuronal elements.Methods:EAE was induced in the adult healthy guinea pigs by weekly intradermal injections of homologous whole brain and spinal cord antigen together with complete Freund’s adjuvant into the foot pad of the animal. The animals were observed for clinical features of the disease after injection.Results:The histological observation revealed two stages of EAE; an initial inflammatory stage followed by demyelination. The inflammatory lesions were focal and invariably related to blood vessels. The inflammatory lesions consisted of perivascular cuffings with lymphocytes and mononuclear cells in the perivascular space and surrounding parenchyma. Perivascular demyelination was restricted to that part of the white matter which was infiltrated by mononuclear cells. The fibres in demyelinating lesions were demyelinated. Perivascular demyelination is followed by patchy demyelination and large plaques of demyelination. Neuronal and axonal damage, necrosis, tissue degeneration and cavity formation were seen in those animals which died during the acute phase of the disease. These changes were found in the spinal cord, brainstem and cerebellum.  Conclusion:The changes observed in results lead to the conclusion that the acute EAE with severity of disease is no more a primary demyelinating disease.   

Do Indian Firms Engage in Greenwashing? Evidence from Indian Firms

This study aims to look at ESG reporting in India through the lens of greenwashing, with a focus on the companies listed in the National Stock Exchange under the NIFTY 50 index using available ESG scores and assessments. Further, it aims to measure the indulgence of greenwashing by the companies. This study also analyses and attempts to highlight the factors that influence a company’s greenwashing behaviour, focusing specifically on the Indian context. Data for the empirical study and calculation of greenwashing score is collected from secondary data sources. We further use a regression method to study the nature of influence and significance of various factors on the calculated greenwashing score and assess the findings with our hypothesis. The study identifies 54% from the 48 companies, part of our sample size as green washers. Most of these companies belong to the manufacturing and energy sector of the Indian economy. The regression results suggest that a company’s cross listing status or its presence in any ESG focus fund has a significant and negative relationship with its observed greenwashing score. On firm level characteristics, the regression results indicate that a company’s board size and the presence of independent directors have a significant impact on the company’s observed greenwashing score

Frequency- and transverse wave-vector-dependent spin Hall conductivity in two-dimensional electron gas with disorder

We determine wave number $q$ and frequency $\omega$ dependent spin Hall conductivity $\sigma_{yx}^s(q, \omega)$ for a disordered two dimensional electron system with Rashba spin orbit interaction when \q is {\it transverse} to the electric field. Both the conventional definition of spin current and its new definition which takes care of the conservation of spins, have been considered. The spin Hall conductivitivities for both of these definitions are qualitatively similar. $\sigma_{yx}^s(q, \omega)$ is zero at $q=0, \omega =0$ and is maximum at $q=0$ and at small but finite $\omega$ whose value depends on different parameters of the system. Interestingly for $\omega \to 0$, $\sigma_{yx}^s(q)$ resonates when $\Lambda \simeq L_{so}$ which are the wavelength $(\Lambda = 2\pi/q)$ of the electric field's spatial variation and the length for one cycle of spin precession respectively. The sign of the out-of-plane component of the electrons' spin flips when the sign of electric field changes due to its spatial variation along transverse direction. It changes the mode of spin precession from clockwise to anti-clockwise or {\it vice versa} and consequently a finite spin Hall current flows in the bulk of the system.Comment: 6 pages; 6 figures; major changes including the titl

Two-field axion-monodromy hybrid inflation model: Dante\u27s Waterfall

We describe a hybrid axion-monodromy inflation model motivated by the Dante\u27s Inferno scenario. In Dante\u27s Inferno, a two-field potential features a stable trench along which a linear combination of the two fields slowly rolls, rendering the dynamics essentially identical to that of single-field chaotic inflation. A shift symmetry allows for the Lyth bound to be effectively evaded as in other axion-monodromy models. In our proposal, the potential is concave downward near the origin and the inflaton trajectory is a gradual downward spiral, ending at a point where the trench becomes unstable. There, the fields begin falling rapidly towards the minimum of the potential and inflation terminates as in a hybrid model. We find parameter choices that reproduce observed features of the cosmic microwave background, and discuss our model in light of recent results from the BICEP2 and Planck experiments