130 research outputs found
Global Crises and Equity Market Contagion
Using the 2007-09 financial crisis as a laboratory, we analyze the transmission of crises to country-industry equity portfolios in 55 countries. We use a factor model to predict crisis returns, defining unexplained increases in factor loadings and residual correlations as indicative of contagion. We find statistically significant evidence of contagion from US markets and from the global financial sector, but the effects are economically small. By contrast, there has been substantial contagion from domestic equity markets to individual domestic equity portfolios, with its severity inversely related to the quality of countries’ economic fundamentals and policies. This confirms the old “wake-up call” hypothesis, with markets and investors focusing substantially more on country-specific characteristics during the crisis.
Absence of Metastable States in Strained Monatomic Cubic Crystals
A tetragonal (Bain path) distortion of a metal with an fcc (bcc) ground state
will initially cause an increase in energy, but at some point along the Bain
path the energy will again decrease until a local minimum is reached. Using a
combination of parametrized tight-binding and first-principles LAPW
calculations we show that this local minimum is unstable with respect to an
elastic distortion, except in the rare case that the minimum is at the bcc
(fcc) point on the Bain path. This shows that body-centered tetragonal phases
of these materials, which have been seen in epitaxially grown thin films, must
be stabilized by the substrate and cannot be free-standing films.Comment: 7 pages, 5 postscript figures, REVTEX, submitted to Phys. Rev.
Superconductivity in Compressed Potassium and Rubidium
Calculations of the electron-phonon interaction in the alkali metals,
Potassium and Rubidium, using the results of band theory and BCS theory-based
techniques suggest that at high pressures K and Rb would be superconductors
with transition temperatures approaching 10 K.Comment: three figure
AFLOW-SYM: Platform for the complete, automatic and self-consistent symmetry analysis of crystals
Determination of the symmetry profile of structures is a persistent challenge
in materials science. Results often vary amongst standard packages, hindering
autonomous materials development by requiring continuous user attention and
educated guesses. Here, we present a robust procedure for evaluating the
complete suite of symmetry properties, featuring various representations for
the point-, factor-, space groups, site symmetries, and Wyckoff positions. The
protocol determines a system-specific mapping tolerance that yields symmetry
operations entirely commensurate with fundamental crystallographic principles.
The self consistent tolerance characterizes the effective spatial resolution of
the reported atomic positions. The approach is compared with the most used
programs and is successfully validated against the space group information
provided for over 54,000 entries in the Inorganic Crystal Structure Database.
Subsequently, a complete symmetry analysis is applied to all 1.7 million
entries of the AFLOW data repository. The AFLOW-SYM package has been
implemented in, and made available for, public use through the automated,
framework AFLOW.Comment: 24 pages, 6 figure
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