Resonant-tunneling oscillators and multipliers for submillimeter receivers

Resonant tunneling through double-barrier heterostructures has attracted increasing interest recently, largely because of the fast charge transport it provides. In addition, the negative differential resistance regions that exist in the current-voltage (I-V) curve (peak-to-valley ratios of 3.5:1 at room temperature, and nearly 10:1 at 77 K, were measured) suggest that high-speed devices based on the character of the I-V curve should be possible. For example, the negative differential resistance region is capable of providing the gain necessary for high-frequency oscillations. In the laboratory attempts were made to increase the frequency and power of these oscillators and to demonstrate several different high-frequency devices

Round-robin tournaments with minimum number of breaks and two teams per club

We study round-robin tournaments for 2n teams. Here n is either interpreted as the number of clubs, each having two teams, or the number of strength groups with two teams each. For even n we give a construction of a single round-robin tournament for 2n teams with 2n - 2 breaks, where the teams of the same club have complementary home-away patterns and play against each other in the first round. If the pairs of teams are strength groups, then a cyclic permutation of the constructed schedule results in a group-balanced tournament

Non-uniqueness of the third post-Newtonian binary point-mass dynamics

It is shown that the recently found non-uniqueness of the third post-Newtonian binary point-mass ADM-Hamiltonian is related to the non-uniqueness at the third post-Newtonian approximation of the applied ADM-coordinate conditions.Comment: LaTeX, 2 pages, submitted to Phys. Rev.

Spherically symmetric equilibria for self-gravitating kinetic or fluid models in the non-relativistic and relativistic case - A simple proof for finite extension

We consider a self-gravitating collisionless gas as described by the Vlasov-Poisson or Einstein-Vlasov system or a self-gravitating fluid ball as described by the Euler-Poisson or Einstein-Euler system. We give a simple proof for the finite extension of spherically symmetric equilibria, which covers all these models simultaneously. In the Vlasov case the equilibria are characterized by a local growth condition on the microscopic equation of state, i.e., on the dependence of the particle distribution on the particle energy, at the cut-off energy E_0, and in the Euler case by the corresponding growth condition on the equation of state p=P(\rho) at \rho=0. These purely local conditions are slight generalizations to known such conditions.Comment: 20 page

How Government Cares for Urban Economic Growth: the Impact of Different Fiscal Grant Schedules in the German Federal States on the Development of Urban Areas

In recent years, in the public discussion on (regional) economic policy, the importance of urban districts or cities for regional and for national economic growth has been strongly emphasized. It is an usual assumption that agglomeration economies may be found inside urban areas. For making best use of agglomeration economies, there have been proposals for changing the traditional scheme of regional policy from an orientation on "interregional equalization“ and "aid" for the regions lagging behind“ towards support for the strongest“ and "stimulating economic growth conditions in urban areas“. The paper has the intention to bring more light into the question how a country’s government could efficiently support the economic conditions in larger cities or urban areas. There are of course several instruments for this. One quite common instrument in most countries are the Systems for Local Fiscal Equalization (LFE), by which the national (federal) government or the states (within federations) are allocating different categories of grants in aid to the local level of government. As the LFE-systems differ strongly not only between different countries, but also between the states within a country, it seems necessary to focus on some countries or even on some states within a country. As a first approach to analyse the existing LFE-rules, this paper is concentrating on the conditions in six selected German states. For this sample, the paper is analyzing the current fiscal position of urban areas within the federal states (or Lander) of Germany and is trying to give some first answers to the following questions: Do some states care more than other states for urban areas? What is the institutional setting for spending state money for urban areas: Are the grants per capita higher for the more agglomerated urban areas? Have the grants the potential to stimulate ur¬ban growth – or are they supporting public functions without positive impacts on the economy? How are the urban centres compensated for their function as central places? The analysis is done on the basis of the states‘ rules on LFE, in the sense of an ex-ante evaluation of these rules, by classifying the rules according to their incidence (in favor or against urban centers). It is shown that there are quite different ways for a state to allocate grants in favour of the cities. There is an enormous lack of transparency in the LFE-systems of all states in the sample. The impression is that the LFE-rules are not trying, so far, to support the cities and their eco¬no¬mic performance consistently. In some states, shrinking cities and cities with special problems (e. g. with a high number of welfare recipients) could be to some extent even in a better fiscal position than cities with economic growth and growth potentials.