Verification for Timed Automata extended with Unbounded Discrete Data Structures

We study decidability of verification problems for timed automata extended with unbounded discrete data structures. More detailed, we extend timed automata with a pushdown stack. In this way, we obtain a strong model that may for instance be used to model real-time programs with procedure calls. It is long known that the reachability problem for this model is decidable. The goal of this paper is to identify subclasses of timed pushdown automata for which the language inclusion problem and related problems are decidable

MTL-Model Checking of One-Clock Parametric Timed Automata is Undecidable

Parametric timed automata extend timed automata (Alur and Dill, 1991) in that they allow the specification of parametric bounds on the clock values. Since their introduction in 1993 by Alur, Henzinger, and Vardi, it is known that the emptiness problem for parametric timed automata with one clock is decidable, whereas it is undecidable if the automaton uses three or more parametric clocks. The problem is open for parametric timed automata with two parametric clocks. Metric temporal logic, MTL for short, is a widely used specification language for real-time systems. MTL-model checking of timed automata is decidable, no matter how many clocks are used in the timed automaton. In this paper, we prove that MTL-model checking for parametric timed automata is undecidable, even if the automaton uses only one clock and one parameter and is deterministic.Comment: In Proceedings SynCoP 2014, arXiv:1403.784

Wolfgang Mühlpfordt and the ‘transformation problem’: some remarks on articles by Howard and King and Gilibert

Until recently, the name of Wolfgang Mühlpfordt (1872-1928) was certainly not among those a theoretical economist was expected to know. Mühlpfordt has now been rehabilitated not only in the Cambridge Journal of Economics (Howard and King: 1987 and Gilibert:1991), but also in the German Jahrbücher für Nationalökonomie und Statistik (Quaas:1991). There are many points of correspondence between my own interpretation and the assessments of Mühlpfordt by Gilibert and by Howard and King. However, I believe it is possible to add some further remarks and also to make some corrections. We do not know why Mühlpfordt did not react to Bortkiewicz's famous articles (1907), to which he would certainly have had something to say. Mühlpfordt was more advanced than Bortkiewicz, since his mathematical approach is of more general validity and he prepared the way for the modern theory of production prices which is now associated with, among others, the name of Piero Sraffa.transformation problem; Wolfgang Mühlpfordt; Ladislaus von Bortkiewicz; labour theory of value

WAS THE WORLDWIDE ASYMMETRY IN CURRENT ACCOUNTS CAUSED BY THE MACROECONOMIC POLICY OF THE GLOBAL ECONOMY’S LEADER?

Some authors sketch the causal chain that produced the current account surplus in China and the current account deficit of the US (as a part of global imbalances) as follows: declining interest rates in the US cause a redirection of capital flows into the periphery, rising capital inflows into China and other Asian countries trigger currency purchases by periphery central banks, and increasing stocks of foreign reserves on the asset side in the central bank balance sheet are matched by a proportional increase of reserve money on the liability side. To keep the exchange rate stable, foreign reserves are accumulated and reserve money expands. The Peoples Bank of China is trying to fight the inflation pressure with several measures, among them higher interest rates. This attracts even more foreign capital to China. Moreover, it cannot solve a problem that originates in the macroeconomic policy of the global economy’s leader – a crucial point in this argument is the redirection thesis. The empirical evidence does not support this thesis in several respects – there is no evidence for a redirected capital flow away from the US toward China, and there is no evidence that interest rates controlled by the Federal Reserve are the cause of the capital flow to China.global imbalances, current account surplus, current account deficit

Pollution-reducing infrastructure and urban environmental policy

Based on a case study on Bombay, we argue that urban infrastructure, like the sewage system and the municipal waste collection, is an important instrument for urban environmental policy. We develop a spatial general equilibrium model of a monocentric city, where infrastructure serves as a public means of abating pollution. Analyzing the optimal supply of pollution-reducing infrastructure, we conclude that it has to be geographically differentiated, even if pollution is homogenous. In a city with a growing population the provision of infrastructure has to be changed throughout the city, not only in newly inhabited areas. Urban environmental policies, based on Pigouvian taxes and pollution-reducing infrastructure, are mutually dependent. In two settings of public or private infrastructure, we show that fiscal environmental policies have to be spatially differentiated, and that income transfers are necessary in order to implement the first best allocation as a residential market equilibrium. --urban environmental policy,pollution-reducing infrastructure,spatial environmental economics,unequal treatment of equal

Does the macroeconomic policy of the global economy’s leader cause the worldwide asymmetry in current accounts?

Schnabl and Freitag (2009) sketch the causal chain that produced the current account surplus in China and the current account deficit of the U.S. (as a part of global imbalances) as follows: declining interest rates in the U.S. cause a redirection of capital flows into the periphery, rising capital inflows into China and other Asian countries trigger currency purchases by periphery central banks, and increasing stocks of foreign reserves on the asset side in the central bank balance sheet are matched by a proportional increase of reserve money on the liability side. To keep the exchange rate stable, foreign reserves are accumulated and reserve money expands. The Peoples Bank of China is trying to fight the inflation pressure with several measures, among them higher interest rates. This attracts even more foreign capital to China. Moreover, it cannot solve a problem that originates in the macroeconomic policy of the global economy’s leader. - A crucial point in this argument is the redirection thesis. The empirical evidence does not support this thesis in several respects—there is no evidence for a redirected capital flow away from the U.S. toward China, and there is no evidence that interest rates controlled by the Federal Reserve are the cause of the capital flow to China.global imbalances, current account surplus, current account deficit