13,400 research outputs found
Chameleon fields and solar physics
In this article we discuss some aspects of solar physics from the standpoint
of the so-called chameleon fields (i.e. quantum fields, typically scalar, where
the mass is an increasing function of the matter density of the environment).
Firstly, we analyze the effects of a chameleon-induced deviation from standard
gravity just below the surface of the Sun. In particular, we develop solar
models which take into account the presence of the chameleon and we show that
they are inconsistent with the helioseismic data. This inconsistency presents
itself not only with the typical chameleon set-up discussed in the literature
(where the mass scale of the potential is fine-tuned to the meV), but also if
we remove the fine-tuning on the scale of the potential. Secondly, we point out
that, in a model recently considered in the literature (we call this model
"Modified Fujii's Model"), a conceivable interpretation of the solar
oscillations is given by quantum vacuum fluctuations of a chameleon.Comment: 17 pages including figure
Excess money growth and inflation dynamics
The paper analyses the short-run impact of periods of strong monetary growth on inflation dynamics for 15 industrialised economies. We find that, over a 3-year horizon, the positive link between monetary aggregates and prices holds in approximately fifty percent of the cases. An econometric investigation suggests that a contemporaneous increase in the gap measures of the real stock price and real housing price and strong dynamics of loans to the private sector significantly increase the probability of turning an episode of excessive money growth into an inflationary outburst. JEL Classification:inflation, money growth, quantity theory of money
Excess money growth and inflation dynamics
The paper analyzes the short-run impact of periods of strong monetary growth on inflation dynamics for 15 industrialized economies. We find that when robust money growth is accompanied by large increases in stock and house prices and loose credit conditions, the probability of recording an inflationary outburst over a three-year horizon is significantly increased. In contrast, significant money stock expansions which are not associated with sustained credit increases and strong dynamics in other asset prices seem to be less likely to have inflationary consequences and thus, less worrying from a policy perspective.Inflation, money growth, quantity theory of money
Specifying Graph Languages with Type Graphs
We investigate three formalisms to specify graph languages, i.e. sets of
graphs, based on type graphs. First, we are interested in (pure) type graphs,
where the corresponding language consists of all graphs that can be mapped
homomorphically to a given type graph. In this context, we also study languages
specified by restriction graphs and their relation to type graphs. Second, we
extend this basic approach to a type graph logic and, third, to type graphs
with annotations. We present decidability results and closure properties for
each of the formalisms.Comment: (v2): -Fixed some typos -Added more reference
OPTIMAL HOMEOMORPHISMS BETWEEN CLOSED CURVES
The concept of natural pseudo-distance has proven to be a powerful tool for measuring the dissimilarity between topological spaces endowed with continuous real-valued functions. Roughly speaking, the natural pseudo-distance is defined as the infimum of the change of the functions' values, when moving from one space to the other through homeomorphisms, if possible. In this paper, we prove the first available result about the existence of optimal
homeomorphisms between closed curves, i.e. inducing a change of the function that equals the natural pseudo-distance
Design-time Models for Resiliency
Resiliency in process-aware information systems is based on the availability of recovery flows and alternative data for coping with missing data. In this paper, we discuss an approach to process and information modeling to support the specification of recovery flows and alternative data. In particular, we focus on processes using sensor data from different sources. The proposed model can be adopted to specify resiliency levels of information systems, based on event-based and temporal constraints
Economic Growth and Carbon Dioxide Emissions in Italy, 1861-2003
This paper examines the relationship between economic growth and carbon dioxide emissions in Italy for the period 1861-2003. Using cointegration, rolling regression and error correction modeling techniques, we find that growth and carbon dioxide emissions are strongly interrelated, and elasticity of pollutant emissions with respect to income has been decreasing over time. For the period 1960-2003 EKC estimates provide evidence for the existence of a reasonable "turning point". However, given the heavy dependence of Italian economy upon fossil fuels, meeting the emissions targets in the accomplishing of the Kyoto Protocol is a very challenging task.Environmental Kuznets Curve; Carbon Dioxide Emissions; Time Series Analysis; Italian Economy
Continuity and discontinuity in learning careers: potentials for a learning space in a changing world
Rewriting Abstract Structures: Materialization Explained Categorically
The paper develops an abstract (over-approximating) semantics for
double-pushout rewriting of graphs and graph-like objects. The focus is on the
so-called materialization of left-hand sides from abstract graphs, a central
concept in previous work. The first contribution is an accessible, general
explanation of how materializations arise from universal properties and
categorical constructions, in particular partial map classifiers, in a topos.
Second, we introduce an extension by enriching objects with annotations and
give a precise characterization of strongest post-conditions, which are
effectively computable under certain assumptions
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