21,050 research outputs found
On the sources of the late integrated Sachs-Wolfe effect
In some scenarios, the peculiar gravitational potential of linear and mildly
nonlinear structures depends on time and, as a result of this dependence, a
late integrated Sachs-Wolfe effect appears. Here, an appropriate formalism is
used which allows us to improve on the analysis of the spatial scales and
locations of the main cosmological inhomogeneities producing this effect. The
study is performed in the framework of the currently preferred flat model with
cosmological constant, and it is also developed in an open model for
comparisons. Results from this analysis are used to discuss the contribution of
Great Attractor-like objects, voids, and other structures to the CMB
anisotropy.Comment: 25 pages, 4 figures, accepted for publication in New Astronom
The hybrid SZ power spectrum: Combining cluster counts and SZ fluctuations to probe gas physics
Sunyaev-Zeldovich (SZ) effect from a cosmological distribution of clusters
carry information on the underlying cosmology as well as the cluster gas
physics. In order to study either cosmology or clusters one needs to break the
degeneracies between the two. We present a toy model showing how complementary
informations from SZ power spectrum and the SZ flux counts, both obtained from
upcoming SZ cluster surveys, can be used to mitigate the strong cosmological
influence (especially that of sigma_8) on the SZ fluctuations. Once the strong
dependence of the cluster SZ power spectrum on sigma_8 is diluted, the cluster
power spectrum can be used as a tool in studying cluster gas structure and
evolution. The method relies on the ability to write the Poisson contribution
to the SZ power spectrum in terms the observed SZ flux counts. We test the toy
model by applying the idea to simulations of SZ surveys.Comment: 12 pages. 11 plots. MNRAS submitte
Study of the glass transition in the amorphous interlamellar phase of highly crystallized poly(ethylene terephthalate)
Poly(ethylene terephthalate) (PET) is a semi--crystalline polymer that can be
crystallized to different degrees heating from the amorphous state. Even when
primary crystallization has been completed, secondary crystallization can take
place with further annealing and modify the characteristics of the amorphous
interlamellar phase. In this work we study the glass transition of highly
crystallized PET and in which way it is modified by secondary crystallization.
Amorphous PET samples were annealed for 4 hours at temperatures between 140C
and 180C. The secondary crystallization process was monitored by differential
scanning calorimetry and the glass transition of the remaining interllamelar
amorphous phase was studied by Thermally Stimulated Depolarization Currents
measurements. Non--isothermal window polarization is employed to resolve the
relaxation in modes with a well--defined relaxation time that are subsequently
adjusted to several standard models. Analysis of experimental results, show
that cooperativity is reduced to a great extend in the interlamellar amorphous
regions. The evolution of the modes on crystallization temperature reveals that
large scale movements are progressively replaced by more localized ones, with
higher frequency, as crystallization takes place at higher temperatures. As a
consequence, the glass transition temperature of the amorphous interlamellar
phase tends to lower values for higher annealing temperatures. Evolution of
calorimetric scans of the glass transition are simulated from the obtained
results and show the same behaviour. The interpretation of these results in
terms of current views about secondary crystallization is discussed.Comment: 30 pages, 5 tables, 12 figures; figure 5 modifie
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