Regional Integration of Equity Markets in Sub-Saharan Africa

Equity markets in developing and emerging economies have grown in number and importance as a result of financial market globalisation. However, their role in economic growth and development is enhanced if nascent markets are integrated with well-established ones. Market integration, measured by the transmission of returns volatility, is identified across a sample of SSA countries, using a unique dataset. Evidence for potential integration between financial markets in Sub-Saharan Africa (SSA) is found. Spillovers are found across markets, some unidirectional and others bi-directional. However, continued illiquidity and incomplete institutions indicate that an integrated financial community remains premature, and considerable regulatory reform and harmonisation will be necessary for this to succeed

Volatility co-movements and spillover effects within the Eurozone economies: A multivariate GARCH approach using the financial stress index

The Eurozone crisis is one the most important economic event in recent years. At its peak, the effects of the crisis have put at serious risk the outcome of the euro project, exposing the inherent weaknesses and vulnerabilities of the monetary union. As the degree of economic and financial integration of these countries is significant, we aim to investigate in details the potential cross-covariance and spillover effects between the Eurozone economies and financial markets. In order to do this, we employ financial stress indexes, as systemic risk metrics in a multivariate GARCH model. This method is able to capture markets’ dependencies and volatility spillovers and is employed on a single market level as well as on the full spectrum of Eurozone markets. The empirical results have shown the important and intensive stress transmission on banking and money markets. Moreover, the role of peripheral countries as stress transmitter is verified, but only for particular periods. The significant spillover effects from core countries are also evident, indicating their important role in the Euro Area and its overall financial stability. The “decoupling” hypothesis is empirically verified, underling the gradually decreasing intensity of spillovers between Euro Area countries. Overall, this paper exhibits the complex structure of spillover effects for Eurozone, along with a clustering effect in the most recent times

Slow waves in locally resonant metamaterials line defect waveguides

In the past decades, many efforts have been devoted to the temporal manipulation of waves, especially focusing on slowing down their propagation. In electromagnetism, from microwave to optics, as well as in acoustics or for elastic waves, slow wave propagation indeed largely benefits both applied and fundamental physics. It is for instance essential in analog signal computing through the design of components such as delay lines and buffers, and it is one of the prerequisite for increased wave/matter interactions. Despite the interest of a broad community, researches have mostly been conducted in optics along with the development of wavelength scaled structured composite media, that appear promising candidates for compact slow light components. Yet their minimum structural scale prevents them from being transposed to lower frequencies where wavelengths range from sub-millimeter to meters. In this article, we propose to overcome this limitation thanks to the deep sub-wavelength scale of locally resonant metamaterials. In our approach, implemented here in the microwave regime, we show that introducing coupled resonant defects in such composite media allows the creation of deep sub-wavelength waveguides. We experimentally demonstrate that waves, while propagating in such waveguides, exhibit largely reduced group velocities. We qualitatively explain the mechanism underlying this slow wave propagation and first experimentally demonstrate, then numerically verify, how it can be taken advantage of to tune the velocity, achieving group indices ng as high as 227 over relatively large bandwidths. We conclude by highlighting the three beneficial consequences of our line defect slow wave waveguides in locally resonant metamaterials: the deep sub-wavelength scale, the very large group indices and the fact that slow wave propagation does not occur at the expense of drastic bandwidth reductions