Credit, Profitability and Instability: A Strictly Structural Approach

This paper offers a purely structural characterisation of the content, limits and contradictions of credit relations in capitalist accumulation. Considering steady-state evolutions and step-change perturbations in a dynamic model of the Marxian circuit of capital, it establishes that sustained paces of net credit extension may boost aggregate profitability, the rate of accumulation, and the aggregate financial robustness of capitalist enterprises. These gains are limited by the economy’s dynamic productive capacities, and tempered by the risks of credit and monetary disruptions created payment obligations established by credit. Economies with higher paces of net credit extension are shown to be more vulnerable to the disruptions to accumulation variously emphasised by Marxian, Keynesian and Post-Keynesian contributions.

At the Heart of the Matter: Household Debt in Contemporary Banking and the International Crisis

This paper considers the nature and role of household indebtedness in contemporary banking and the current financial and economic crises. It offers a concise empirical exposition of the centrality of household lending and related financial services to leading banking institutions and to the credit systems of a number of advanced and middle-income economies. It also offers socioeconomic characterizations of this debt and its macroeconomic significance from the standpoint of Marxist political economy, affording two distinctive insights. First, the concrete social content of household debt over the past two decades has helped ensure this lending remained highly profitable to lenders, making it a natural vehicle for destabilizing capital-market competition. Second, a crisis characterized by record levels of over-indebted wage-earning households is likely to pose distinctive difficulties to a process of market-based recovery. While the destruction of capital values during a crisis lays the basis for the eventual restoration of profitability and solvency for some enterprises, over-indebted wage-earning households face no analogous opportunity. Without new speculative asset-price bubbles, the restoration of their financial stability hinges on reductions in consumption or increases in wages, both of which present obstacles to a market-based process of economic recovery.

A NOTE ON COMONOTONICITY AND POSITIVITY OF THE CONTROL COMPONENTS OF DECOUPLED QUADRATIC FBSDE

In this small note we are concerned with the solution of Forward-Backward Stochastic Differential Equations (FBSDE) with drivers that grow quadratically in the control component (quadratic growth FBSDE or qgFBSDE). The main theorem is a comparison result that allows comparing componentwise the signs of the control processes of two different qgFBSDE. As a byproduct one obtains conditions that allow establishing the positivity of the control process.Comment: accepted for publicatio

Modelling spin waves in noncollinear antiferromagnets: spin-flop states, spin spirals, skyrmions and antiskyrmions

Spin waves in antiferromagnetic materials have great potential for next-generation magnonic technologies. However, their properties and their dependence on the type of ground-state antiferromagnetic structure are still open questions. Here, we investigate theoretically spin waves in one- and two-dimensional model systems with a focus on noncollinear antiferromagnetic textures such as spin spirals and skyrmions of opposite topological charges. We address in particular the nonreciprocal spin excitations recently measured in bulk antiferromagnet $\alpha$--$\text{Cu}_2\text{V}_2\text{O}_7$ utilizing inelastic neutron scattering experiments [Phys.\ Rev.\ Lett.\ \textbf{119}, 047201 (2017)], where we help to characterize the nature of the detected spin-wave modes. Furthermore, we discuss how the Dzyaloshinskii-Moriya interaction can lift the degeneracy of the spin-wave modes in antiferromagnets, resembling the electronic Rashba splitting. We consider the spin-wave excitations in antiferromagnetic spin-spiral and skyrmion systems and discuss the features of their inelastic scattering spectra. We demonstrate that antiskyrmions can be obtained with an isotropic Dzyaloshinskii-Moriya interaction in certain antiferromagnets.Comment: 26 pages, 9 figure

First-principles investigation of spin wave dispersions in surface-reconstructed Co thin films on W(110)

We computed spin wave dispersions of surface-reconstructed Co films on the W(110) surface in the adiabatic approximation. The magnetic exchange interactions are obtained via first-principles electronic structure calculations using the Korringa-Kohn-Rostoker Green function method. We analyze the strength and oscillatory behavior of the intralayer and interlayer magnetic interactions and investigate the resulting spin wave dispersions as a function of the thickness of Co films. In particular, we highlight and explain the strong impact of hybridization of the electronic states at the Co-W interface on the magnetic exchange interactions and on the spin wave dispersions. We compare our results to recent measurements based on electron energy loss spectroscopy [E. Michel, H. Ibach, and C.M. Schneider, Phys. Rev. B 92, 024407 (2015)]. Good overall agreement with experimental findings can be obtained by considering the possible overestimation of the spin splitting, stemming from the local spin density approximation, and adopting an appropriate correction.Comment: 14 pages, 14 figure

Characteristic functions on the boundary of a planar domain need not be traces of least gradient functions

Given a smooth bounded planar domain, we construct a compact set on the boundary s.t. its characteristic function is not the trace of a least gradient function. This generalize the construction of Spradlin and Tamasan [ST14] on the disc