301,342 research outputs found
Deflationary Models Driven by Matter Creation
A nonsingular deflationary cosmology driven by adiabatic matter creation is
proposed. In this scenario there is no preinflationary stage as happens in
conventional inflationary models. Deflation starts from a de Sitter spacetime
characterized by an arbitrary time scale , which also pins down an
initial value for the temperature of the universe. The model evolves
continuously towards a slightly modified Friedman-Robertson-Walker universe.
The horizon and other well known problems of the standard model are then solved
but, unlike in microscopic models of inflation, there is no supercooling and
subsequent reheating. Entropy generation is concomitant with deflation and if
is of the order of the Planck time, the present day value of the
radiation temperature is deduced. It is also shown that the ``age problem''
does not exist here. In particular, the theoretically favored FRW flat model is
old enough to agree with the observations even given the high values of
suggested by recent measurements.Comment: 17 pages, 2 figures(available from the authors), uses LATE
Periódicos de Oporto, públicos de la ciudad : la construcción de la identidad editorial y las audiencias
The three Oporto daily newspapers O Comércio do Porto, O Primeiro de Janeiro and Jornal de NotÃcias were founded during the XIX century and steadily grew in prestige and respect amongst the national Portuguese press. These papers began as local and ideological projects supported by political parties and a powerful commercial association but gradually evolved to more comprehensive newspapers with a wider range of lectors. Each particular profile was built through editorial policies which led to strategies of audience identification, underlined by the charisma of their owners and directors. The aim of this study is to identify the engagement processes with readers in their early days and the methodology will rely on sources such as newspapers contents and some other specialized publications. The key moments of evolution in Comércio, Janeiro and NotÃcias will be tracked by the adaptation to the modernization challenges according to reports, newspapers and some senior journalists’ testimoniesLos periódicos de Oporto O Comércio do Porto, O Primeiro de Janeiro y Jornal de NotÃcias, surgieron en el siglo XIX y gradualmente se tornaron tÃtulos nacionales de prestigio. Inicialmente dos de ellos eran proyectos ideológicos de partidos polÃticos locales y el tercero tenÃa el respaldo de la asociación comercial, pero con el tiempo fueron evolucionando hacia modelos de información más anchos, ampliando el cÃrculo de lectores. El perfil informativo de cada uno se construyó en articulación con públicos especÃficos y a través de la promoción de procesos de identificación, reforzada por la acción de propietarios y directores carismáticos. El objetivo de este estudio es identificar estas caracterÃsticas editoriales y procesos de conquista del público en sus primeras etapas, según una metodologÃa basada en el contenido de los periódicos y publicaciones especializadas. Los momentos clave de la transformación serán identificados por los periódicos, informes y testimonios de periodista
Ising model with spins S=1/2 and 1 on directed and undirected Erd\"os-R\'enyi random graphs
Using Monte Carlo simulations we study the Ising model with spin S=1/2 and 1
on {\it directed} and {\it undirected} Erd\"os-R\'enyi (ER) random graphs, with
neighbors for each spin. In the case with spin S=1/2, the {\it undirected}
and {\it directed} ER graphs present a spontaneous magnetization in the
universality class of mean field theory, where in both {\it directed} and {\it
undirected} ER graphs the model presents a spontaneous magnetization at (), but no spontaneous magnetization at which is
the percolation threshold. For both {\it directed} and {\it undirected} ER
graphs with spin S=1 we find a first-order phase transition for z=4 and 9
neighbors.Comment: 11 pages, 8 figure
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