Debt, Cash Flow and Inflation Incentives: A Swedish Example

The fiscal gains from, and hence the political incentives to, an increase in inflation rate of ten percentage points may be substantial: with Swedish data from 1994, these gains would have been an annual real flow of 3-4 percent of GDP, or a capitalized value of nearly 100 percent of GDP. They would mainly have arisen from the nominalistic features of the tax and transfer systems rather than from the traditional sources: seignorage and real depreciation of the public debt. The welfare costs of such an inflation increase would have been even larger, however, and would thus have reduced net welfare. Possible institutional reforms, aimed at making the political costs of inflation more equal to the social costs, are presented and discussed

Dependence of boundary lubrication on the misfit angle between the sliding surfaces

Using molecular dynamics based on Langevin equations with a coordinate- and velocity-dependent damping coefficient, we study the frictional properties of a thin layer of "soft" lubricant (where the interaction within the lubricant is weaker than the lubricant-substrate interaction) confined between two solids. At low driving velocities the system demonstrates stick-slip motion. The lubricant may or may not be melted during sliding, thus exhibiting either the "liquid sliding" (LS) or the "layer over layer sliding" (LoLS) regimes. The LoLS regime mainly operates at low sliding velocities. We investigate the dependence of friction properties on the misfit angle between the sliding surfaces and calculate the distribution of static frictional thresholds for a contact of polycrystalline surfaces.Comment: 8 pages, 11 figure

Sealing is at the Origin of Rubber Slipping on Wet Roads

Loss of braking power and rubber skidding on a wet road is still an open physics problem, since neither the hydrodynamical effects nor the loss of surface adhesion that are sometimes blamed really manage to explain the 20-30% observed loss of low speed tire-road friction. Here we advance a novel mechanism based on sealing of water-filled substrate pools by the rubber. The sealed-in water effectively smoothens the substrate, thus reducing the viscoelastic dissipation in bulk rubber induced by surface asperities, well established as a major friction contribution. Starting with the measured spectrum of asperities one can calculate the water-smoothened spectrum and from that the predicted friction reduction, which is of the right magnitude. The theory is directly supported by fresh tire-asphalt friction data.Comment: 5 pages, 4 figures. Published on Nature Materials (November 7th 2004

Rubber friction on (apparently) smooth lubricated surfaces

We study rubber sliding friction on hard lubricated surfaces. We show that even if the hard surface appears smooth to the naked eye, it may exhibit short wavelength roughness, which may give the dominant contribution to rubber friction. That is, the observed sliding friction is mainly due to the viscoelastic deformations of the rubber by the substrate surface asperities. The presented results are of great importance for rubber sealing and other rubber applications involving (apparently) smooth surfaces.Comment: 7 pages, 15 figure

Integration of Ferroelectric HfO2 onto a III-V Nanowire Platform

The discovery of ferroelectricity in CMOS-compatible oxides, such as doped hafnium oxide, has opened new possibilities for electronics by reviving the use of ferroelectric implementations on modern technology platforms. This thesis presents the ground-up integration of ferroelectric HfO2 on a thermally sensitive III-V nanowire platform leading to the successful implementation of ferroelectric transistors (FeFETs), tunnel junctions (FTJs), and varactors for mm-wave applications. As ferroelectric HfO2 on III-V semiconductors is a nascent technology, a special emphasis is put on the fundamental integration issues and the various engineering challenges facing the technology.The fabrication of metal-oxide-semiconductor (MOS) capacitors is treated as well as the measurement methods developed to investigate the interfacial quality to the narrow bandgap III-V materials using both electrical and operando synchrotron light source techniques. After optimizing both the films and the top electrode, the gate stack is integrated onto vertical InAs nanowires on Si in order to successfully implement FeFETs. Their performance and reliability can be explained from the deeper physical understanding obtained from the capacitor structures.By introducing an InAs/(In)GaAsSb/GaSb heterostructure in the nanowire, a ferroelectric tunnel field effect transistor (ferro-TFET) is fabricated. Based on the ultra-short effective channel created by the band-to-band tunneling process, the localized potential variations induced by single ultra-scaled ferroelectric domains and individual defects are sensed and investigated. By intentionally introducing a gate-source overlap in the ferro-TFET, a non-volatile reconfigurable single-transistor solution for modulating an input signal with diverse modes including signal transmission, phase shift, frequency doubling, and mixing is implemented.Finally, by fabricating scaled ferroelectric MOS capacitors in the front-end with a dedicated and adopted RF and mm-wave backend-of-line (BEOL) implementation, the ferroelectric behavior is captured at RF and mm-wave frequencies

INTERNATIONALIZATION OF CLINICAL AND EXPERIMENTAL MEMORY RESEARCH

A problem-oriented retrospective information search in MEDLINE on CD-ROM in 1981-1993 revealed the relevant publications devoted mainly to physiology and pharmacology of human and animal memory. The annual dynamics of a set of bibliometric parameters (number of articles and journals containing these articles; number of countries of authors and journals; number of publications in own and foreign journals; number of interdisciplinary and international journals, language of papers, etc.) was studied to identify some essential patterns of internationalization of the interdisciplinary memory research. There were a total of 5597 papers by authors from 48 countries in 809 journals from 40 countries. In 1988-1993 only, there were 1361 papers (48,47 %) in foreign journals. In 42 international journals from 9 countries a total of 231 papers were published while 50 interdisciplinary journals from 13 countries contained 579 papers. Bulgarian memory research was relatively insufficiently presented in this data-base

Dynamical transitions and sliding friction in the two-dimensional Frenkel-Kontorova model

The nonlinear response of an adsorbed layer on a periodic substrate to an external force is studied via a two dimensional uniaxial Frenkel-Kontorova model. The nonequlibrium properties of the model are simulated by Brownian molecular dynamics. Dynamical phase transitions between pinned solid, sliding commensurate and incommensurate solids and hysteresis effects are found that are qualitatively similar to the results for a Lennard-Jones model, thus demonstrating the universal nature of these features.Comment: 11 pages, 12 figures, to appear in Phys. Rev.

Finite-size scaling in the interfacial stiffness of rough elastic contacts

The total elastic stiffness of two contacting bodies with a microscopically rough interface has an interfacial contribution K that is entirely attributable to surface roughness. A quantitative understanding of K is important because it can dominate the total mechanical response and because it is proportional to the interfacial contributions to electrical and thermal conductivity in continuum theory. Numerical simulations of the dependence of K on the applied squeezing pressure p are presented for nominally flat elastic solids with a range of surface roughnesses. Over a wide range of p, K rises linearly with p. Sublinear power-law scaling is observed at small p, but the simulations reveal that this is a finite-size effect. We derive accurate, analytical expressions for the exponents and prefactors of this low-pressure scaling of K by extending the contact mechanics theory of Persson to systems of finite size. In agreement with our simulations, these expressions show that the onset of the low-pressure scaling regime moves to lower pressure as the system size increases.Comment: Supplementary material is available at arXiv:1210.4255, 5 pages, 3 figure

International Borrowing and Time-Consistent Fiscal Policy

We discuss optimal fiscal policy in open economies, using an open-economy version of a model used in the recent work by Lucas and Stokey. An optimal allocation  smooths out the tax distortions associated with financing a given sequence of government consumption, and it also smooths out private consumption of goods and leisure by borrowing (lending) on the international capital market in periods with high (low) government consumption. The main question we ask is how the optimal policy can be made time-consistent, when usccessive governments reoptimize with respect to current and future tax rates, but most honor the government debt obligations. We show that this requires government debt of sufficiently rich maturity to be issued. First we treat a case with capital controls, where only the government can borrow and lend abroad. The there is a unique restructuring scheme for the domestic debt that is necessary to give succeeding governments incentives to continue following the optimal policy (here we interpret and extend Lucas and Stokey's results). For a small economy, this scheme is also sufficient for time-consistency, but in an economy large enough to affect its terms of trade, it is also necessary to follow a unique restructuring scheme for the government's (and the country's) foreign debt. When there are no capital controls, time-consistency is no longer a problem in a small economy. In a large economy, what matters is total government debt and total foreign debt (but not their composition), and again there are unique maturity structures necessary and sufficient for time-consistency. An interesting observation is that in the distorted world we consider, relaxing the capital controls actually deteriorates welfare