A unified projection formalism for the Al-Pd-Mn quasicrystal Xi-approximants and their metadislocations

The approximants xi, xi' and xi'_n of the quasicrystal Al-Mn-Pd display most interesting plastic properties as for example phason-induced deformation processes (Klein, H., Audier, M., Boudard, M., de Boissieu, M., Beraha, L., and Duneau, M., 1996, Phil. Mag. A, 73, 309.) or metadislocations (Klein, H., Feuerbacher, M., Schall, P., and Urban, K., 1999, Phys. Rev. Lett., 82, 3468.). Here we demonstrate that the phases and their deformed or defected states can be described by a simple projection formalism in three-dimensional space - not as usual in four to six dimensions. With the method we can interpret microstructures observed with electron microscopy as phasonic phase boundaries. Furthermore we determine the metadislocations of lowest energy and relate them uniquely to experimentally observed ones. Since moving metadislocations in the xi'-phase can create new phason-planes, we suggest a dislocation induced phase transition from xi' to xi'_n. The methods developed in this paper can as well be used for various other complex metallic alloys.Comment: 25 pages, 12 figure

The U.S. current account deficit and the expected share of world output

We investigate the possibility that the large current account deficits of the U.S. are the outcome of optimizing behavior. We develop a simple long-run world equilibrium model in which the current account is determined by the expected discounted present value of its future share of world GDP relative to its current share of world GDP. The model suggests that under some reasonable assumptions about future U.S. GDP growth relative to the rest of the advanced countries--more modest than the growth over the past 20 years--the current account deficit is near optimal levels. We then explore the implications for the real exchange rate. Under some plausible assumptions, the model implies little change in the real exchange rate over the adjustment path, though the conclusion is sensitive to assumptions about tastes and technology. Then we turn to empirical evidence. A test of current account sustainability suggests that the U.S. is not keeping on a long-run sustainable path. A direct test of our model finds that the dynamics of the U.S. current account--the increasing deficits over the past decade--are difficult to explain under a particular statistical model (Markov-switching) of expectations of future U.S. growth. But, if we use survey data on forecasted GDP growth in the G7, our very simple model appears to explain the evolution of the U.S. current account remarkably well. We conclude that expectations of robust performance of the U.S. economy relative to the rest of the advanced countries is a contender--though not the only legitimate contender--for explaining the U.S. current account deficit.Budget deficits ; Balance of trade

Violating the Law of One Price: Should We Make a Federal Case Out of It?

We use new disaggregated data on consumer prices to determine why there is variability in prices of similar goods across U.S. cities. We address questions similar to those that have arisen in the international context: is this variability purely a result of market segmentation or do sticky nominal prices play a role? We also examine how the degree of tradability of a good influences price variability. Surprisingly, we find that variability is larger for traded-goods. We attribute this finding to greater price stickiness for non-traded goods. Distance between cities accounts for a significant amount of the variation in prices between pairs of cities. But we also find that nominal price stickiness plays an even more significant role.

Relative Returns on Equities in Pacific Basin Countries

We examine the factors that determine the differences in ex ante returns on equities in eleven Pacific Basin countries. Our concern is whether real return differentials are primarily caused by nominal return differentials or expected changes in real exchange rates. We find that nominal return differentials account for most of the difference, which suggests that either there is not free mobility of capital between the countries of our study or that there are significant differences in the riskiness of returns across countries. We do not find a significant relationship between the size of the return differentials and the flexibility of the nominal exchange rate.