4,198 research outputs found
The Impact of the Temporal Distribution of Communicating Civilizations on their Detectability
We use a statistical model to investigate the detectability (defined by the
requirement that they are in causal contact with us) of communicating
civilizations within a volume of the universe surrounding our location. If the
civilizations are located in our Galaxy, the detectability requirement imposes
a strict constraint on their epoch of appearance and their communicating
lifespan. This, in turn, implies that the fraction of civilizations of which we
can find any empirical evidence strongly depends on the specific features of
their temporal distribution. Our approach shed light on aspects of the problem
that can escape the standard treatment based on the Drake equation. Therefore,
it might provide the appropriate framework for future studies dealing with the
evolutionary aspects of the search for extraterrestrial intelligence (SETI).Comment: 17 pages, 1 figure. Accepted for publication in Astrobiolog
Cosmology from Planck
I briefly review some of the main scientific outputs expected from the
upcoming Planck mission. Planck will map the CMB sky with 5' resolution and
K sensitivity, with minimal foreground contribution and superb control on
systematics. It will collect the entire information enclosed in the temperature
primary anisotropy signal and will also get a good measurement of the polarized
component of the CMB. This will have profound implications on our knowledge of
the physics of the early universe and on the determination of cosmological
parameters.Comment: Proceedings of the Francesco Melchiorri Memorial Conference (Rome,
Italy, April 12-14 2006). To appear in New Astron. Re
Rotated canonical correlation analysis for multilingual corpora
This paper aims at proposing the joint use of Canonical Correlation Analysis and Procrustes Rotations (RCA), when we deal with a text and its translation into another language. The basic idea is representing words in the two different natural languages on a common reference space. The main characteristic of this space is to be lan-guage independent, although Procrustes Rotation is performed transforming the lexical table derived from trans-lation by minimizing its distance from the lexical table belonging to the original corpus, while the subsequent Canonical Correlation Analysis treats symmetrically the two word sets. The most interesting RCA feature is building a unique reference space for representing the correlation structure in the data, inducing the two systems of canonical factors to lie on the same space. These graphical representations enables us to read distances be-tween corresponding points in terms of different way of translating the same word in relation with the general context defined by the canonical variates. Trying to understand the distances between matched points could rep-resent an useful tool for enriching lexical resources in a translation procedure. In this paper we propose the com-parison of the most frequent content bearing words in the two languages, analyzing one year (2003) of Le Monde Diplomatique and its Italian edition
Reviewing agent-based modelling of socio-ecosystems: a methodology for the analysis of climate change adaptation and sustainability
The integrated - environmental, economic and social - analysis of climate change calls for a paradigm shift as it is fundamentally a problem of complex, bottom-up and multi-agent human behaviour. There is a growing awareness that global environmental change dynamics and the related socio-economic implications involve a degree of complexity that requires an innovative modelling of combined social and ecological systems. Climate change policy can no longer be addressed separately from a broader context of adaptation and sustainability strategies. A vast body of literature on agent-based modelling (ABM) shows its potential to couple social and environmental models, to incorporate the influence of micro-level decision making in the system dynamics and to study the emergence of collective responses to policies. However, there are few publications which concretely apply this methodology to the study of climate change related issues. The analysis of the state of the art reported in this paper supports the idea that today ABM is an appropriate methodology for the bottom-up exploration of climate policies, especially because it can take into account adaptive behaviour and heterogeneity of the system's components.Review, Agent-Based Modelling, Socio-Ecosystems, Climate Change, Adaptation, Complexity.
COBE Constraints on a Compact Toroidal Low-density Universe
In this paper, the cosmic microwave background (CMB) anisotropy in a
multiply-connected compact flat 3-torus model with the cosmological constant is
investigated. Using the COBE-DMR 4-year data, a full Bayesian analysis revealed
that the constraint on the topology of the flat 3-torus model with
low-matter-density is less stringent. As in compact hyperbolic models, the
large-angle temperature fluctuations can be produced as the gravitational
potential decays at the -dominant epoch well after the last
scattering. The maximum allowed number of images of the cell (fundamental
domain) within the observable region at present is approximately 49 for
and whereas for and
.Comment: 13 pages using RevTeX, 5 eps files, typos correcte
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