34,274 research outputs found
Further Evidence on Convergence across Italian Regions
In the last decade the issue of convergence across states and regions has received a great deal of attention both on the theoretical and empirical ground. On the empirical ground different specifications lead to different results and their robustness is also questioned. We review both neoclassical and endogenous growth theories and the evidence on international and Italian data. We use a methodology that enhances the power of the estimates proposed by Evans and Karras (Journal of Monetary Economics, 1996) that uses panel data and test for their stochastic properties. Data cover the time-span 1951-1998. We find evidence of conditional convergence.
Regularity Properties and Pathologies of Position-Space Renormalization-Group Transformations
We reconsider the conceptual foundations of the renormalization-group (RG)
formalism, and prove some rigorous theorems on the regularity properties and
possible pathologies of the RG map. Regarding regularity, we show that the RG
map, defined on a suitable space of interactions (= formal Hamiltonians), is
always single-valued and Lipschitz continuous on its domain of definition. This
rules out a recently proposed scenario for the RG description of first-order
phase transitions. On the pathological side, we make rigorous some arguments of
Griffiths, Pearce and Israel, and prove in several cases that the renormalized
measure is not a Gibbs measure for any reasonable interaction. This means that
the RG map is ill-defined, and that the conventional RG description of
first-order phase transitions is not universally valid. For decimation or
Kadanoff transformations applied to the Ising model in dimension ,
these pathologies occur in a full neighborhood of the low-temperature part of the first-order
phase-transition surface. For block-averaging transformations applied to the
Ising model in dimension , the pathologies occur at low temperatures
for arbitrary magnetic-field strength. Pathologies may also occur in the
critical region for Ising models in dimension . We discuss in detail
the distinction between Gibbsian and non-Gibbsian measures, and give a rather
complete catalogue of the known examples. Finally, we discuss the heuristic and
numerical evidence on RG pathologies in the light of our rigorous theorems.Comment: 273 pages including 14 figures, Postscript, See also
ftp.scri.fsu.edu:hep-lat/papers/9210/9210032.ps.
There Is No Pure Empirical Reasoning
The justificatory force of empirical reasoning always depends upon the existence of some synthetic, a priori justification. The reasoner must begin with justified, substantive constraints on both the prior probability of the conclusion and certain conditional probabilities; otherwise, all possible degrees of belief in the conclusion are left open given the premises. Such constraints cannot in general be empirically justified, on pain of infinite regress. Nor does subjective Bayesianism offer a way out for the empiricist. Despite often-cited convergence theorems, subjective Bayesians cannot hold that any empirical hypothesis is ever objectively justified in the relevant sense. Rationalism is thus the only alternative to an implausible skepticism
Kernel Analog Forecasting: Multiscale Test Problems
Data-driven prediction is becoming increasingly widespread as the volume of
data available grows and as algorithmic development matches this growth. The
nature of the predictions made, and the manner in which they should be
interpreted, depends crucially on the extent to which the variables chosen for
prediction are Markovian, or approximately Markovian. Multiscale systems
provide a framework in which this issue can be analyzed. In this work kernel
analog forecasting methods are studied from the perspective of data generated
by multiscale dynamical systems. The problems chosen exhibit a variety of
different Markovian closures, using both averaging and homogenization;
furthermore, settings where scale-separation is not present and the predicted
variables are non-Markovian, are also considered. The studies provide guidance
for the interpretation of data-driven prediction methods when used in practice.Comment: 30 pages, 14 figures; clarified several ambiguous parts, added
references, and a comparison with Lorenz' original method (Sec. 4.5
Poland in the Period of Economic Transition and Germany After Reunification an Attempt at Assessing Σ-Convergence
In 2009 and 2010 Poland and Germany are celebrating some important anniversaries - 20 years of the first free elections and the fall of the Berlin Wall. These jubilees inspire research aiming at taking stock of developments having unfolded over this time. Since the economic cohesion is high on the EU agenda, examining international and interregional differences seems an important research task. This article aims at evaluating and comparing σ-convergence (diminishing discrepancies of GDP p.c.) in Poland (1995-2005) and Germany (1992-2006) on three NUTS levels. Preliminary results point to inequalities regularly diminishing in Germany, however, growing in Poland. A tentative reasoning suggests that increasing values of regional differences observed in Poland might be a temporary phenomenon
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