15,842 research outputs found
Polytropic equation of state and primordial quantum fluctuations
We study the primordial Universe in a cosmological model where inflation is
driven by a fluid with a polytropic equation of state . We calculate the dynamics of the scalar factor and build a
Universe with constant density at the origin. We also find the equivalent
scalar field that could create such equation of state and calculate the
corresponding slow-roll parameters. We calculate the scalar perturbations, the
scalar power spectrum and the spectral index.Comment: 16 pages, 4 figure
The importance of subclasses of chitin synthase enzymes with myosin-like domains for the fitness of fungi
Acknowledgements TG and CF are funded by FEDER funds through the Operational Programme Competitiveness Factors – COMPETE and national funds by FCT – Foundation for Science and Technology under the strategic project UID/NEU/04539/2013. C.F. is a recipient of a postdoctoral fellowship from FCT-Fundação para a Ciência e Tecnologia (SFRH/BPD/63733/2009). NG is funded by The Wellcome Trust (080088, 086827, 075470, 099215 & 097377), the FungiBrain Marie Curie Network and the Medical Research Council (UK).Peer reviewedPostprin
Constraints on the duality relation from ACT cluster data
The cosmic distance-duality relation (CDDR), , where and and are, respectively, the
luminosity and the angular diameter distances, holds as long as the number of
photons is conserved and gravity is described by a metric theory. Testing such
hypotheses is, therefore, an important task for both cosmology and fundamental
physics. In this paper we use 91 measurements of the gas mass fraction of
galaxy clusters recently reported by the Atacama Cosmology Telescope (ACT)
survey along with type Ia supernovae observations of the Union2.1 compilation
to probe a possible deviation from the value . Although in agreement
with the standard hyphothesis, we find that this combination of data tends to
favor negative values of which might be associated with some physical
processes increasing the number of photons and modifying the above relation to
.Comment: 4 pages, 2 figures, 2 table
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