1,142 research outputs found
Angular-planar CMB power spectrum
Gaussianity and statistical isotropy of the Universe are modern cosmology's
minimal set of hypotheses. In this work we introduce a new statistical test to
detect observational deviations from this minimal set. By defining the
temperature correlation function over the whole celestial sphere, we are able
to independently quantify both angular and planar dependence (modulations) of
the CMB temperature power spectrum over different slices of this sphere. Given
that planar dependence leads to further modulations of the usual angular power
spectrum , this test can potentially reveal richer structures in the
morphology of the primordial temperature field. We have also constructed an
unbiased estimator for this angular-planar power spectrum which naturally
generalizes the estimator for the usual 's. With the help of a chi-square
analysis, we have used this estimator to search for observational deviations of
statistical isotropy in WMAP's 5 year release data set (ILC5), where we found
only slight anomalies on the angular scales and . Since this
angular-planar statistic is model-independent, it is ideal to employ in
searches of statistical anisotropy (e.g., contaminations from the galactic
plane) and to characterize non-Gaussianities.Comment: Replaced to match the published version. Journal-ref: Phys.Rev. D80
063525 (2009
A note on dualities in Einstein's gravity in the presence of a non-minimally coupled scalar field
We show that the action of Einstein's gravity with a scalar field coupled in
a generic way to spacetime curvature is invariant under a particular set of
conformal transformations. These transformations relate dual theories for which
the effective couplings of the theory are scaled uniformly. In the simplest
case, this class of dualities reduce to the S-duality of low-energy effective
action of string theory.Comment: 12 page
Spherical Collapse in Chameleon Models
We study the gravitational collapse of an overdensity of nonrelativistic
matter under the action of gravity and a chameleon scalar field. We show that
the spherical collapse model is modified by the presence of a chameleon field.
In particular, we find that even though the chameleon effects can be
potentially large at small scales, for a large enough initial size of the
inhomogeneity the collapsing region possesses a thin shell that shields the
modification of gravity induced by the chameleon field, recovering the standard
gravity results. We analyse the behaviour of a collapsing shell in a
cosmological setting in the presence of a thin shell and find that, in contrast
to the usual case, the critical density for collapse depends on the initial
comoving size of the inhomogeneity.Comment: matches printed versio
Energy density and pressure of long wavelength gravitational waves
Inflation leads us to expect a spectrum of gravitational waves (tensor
perturbations) extending to wavelengths much bigger than the present observable
horizon. Although these gravity waves are not directly observable, the energy
density that they contribute grows in importance during the radiation- and
dust-dominated ages of the universe. We show that the back reaction of tensor
perturbations during matter domination is limited from above, since
gravitational waves of wavelength have a share of the total energy
density during matter domination that is at most
equal to the share of the total energy density that they had when the mode
exited the Hubble radius during inflation. This work is to
be contrasted to that of Sahni, who analyzed the energy density of gravity
waves only insofar as their wavelengths are smaller than . Such a
cut-off in the spectral energy of gravity waves leads to the breakdown of
energy conservation, and we show that this anomaly is eliminated simply by
taking into account the energy density and pressure of long wavelength
gravitational waves as well as short wavelength ones.Comment: Updated one reference; 17 pages, no figure
One Loop Back Reaction On Power Law Inflation
We consider quantum mechanical corrections to a homogeneous, isotropic and
spatially flat geometry whose scale factor expands classically as a general
power of the co-moving time. The effects of both gravitons and the scalar
inflaton are computed at one loop using the manifestly causal formalism of
Schwinger with the Feynman rules recently developed by Iliopoulos {\it et al.}
We find no significant effect, in marked contrast with the result obtained by
Mukhanov {\it et al.} for chaotic inflation based on a quadratic potential. By
applying the canonical technique of Mukhanov {\it et al.} to the exponential
potentials of power law inflation, we show that the two methods produce the
same results, within the approximations employed, for these backgrounds. We
therefore conclude that the shape of the inflaton potential can have an
enormous impact on the one loop back-reaction.Comment: 28 pages, LaTeX 2 epsilo
Energy-Momentum Tensor of Cosmological Fluctuations during Inflation
We study the renormalized energy-momentum tensor (EMT) of cosmological scalar
fluctuations during the slow-rollover regime for chaotic inflation with a
quadratic potential and find that it is characterized by a negative energy
density which grows during slow-rollover. We also approach the back-reaction
problem as a second-order calculation in perturbation theory finding no
evidence that the back-reaction of cosmological fluctuations is a gauge
artifact. In agreement with the results on the EMT, the average expansion rate
is decreased by the back-reaction of cosmological fluctuations.Comment: 19 pages, no figures.An appendix and references added, conclusions
unchanged, version accepted for publication in PR
Mandibular osteosarcoma in a goat
Introduction-A few large surveys on tumour prevalence in goats indicate that tumours in general are quite common in this species. Reviews of neoplastic diseases in goats indicate a prevalence ranging from 0,8 to 11%. However, osteogenic tumours arising from facial bones in goats are rare. Regarding oral localization only a few mesenchymal tumours have been described arising from the gengiva. Case presentation-A 4-year old, female crossbred goat was referred with a history of dysorexia and a slow growing painful mass on the face. On physical examination the animal showed poor body condition and the left side of the face was deformed by a voluminous mass which, at the inspection of the oral cavity, displaced the maxillary teeth. Differential diagnoses included os-teomyelitis and benign (osteoma, chondroma, ossifying and non ossifying fibroma, odontogenic tumours) as well as malignant (osteosarcoma, chondrosarcoma) mesenchymal tumours arising from either the connective tissue and bone. The goat was euthanized because of the extension of the lesion and a complete necropsy was performed. Grossly, the face was deformed by the presence of a hard mass arising from the branch of the left mandible. Histologically the oral mass was composed of heterogeneous proliferation of malignant osteoblasts intermigled with brightly eosinophilic strands or island of osteoid matrix. Neoplastic cells, interpreted as malignant osteoblasts, were characterized by plump to round or spindle-shape morphology, with moderate basophilic cytoplasm and an eccentrically located voluminous nucleus containing a large prominent nucleolus. Mitotic figures were found and were either bipolar and atypical. At necropsy no metastases were found and the final diagnosis was non-metastasizing mandibular osteoblastic osteosarcoma. Conclusion-In conclusion, regardless the type of tumour, the goat was euthanized because of the extension and the severity of the lesion. Necropsy and histological examination were necessary to correctly classify the tumour as a non-metastasizing mandibular osteosarcoma
Seafood fraud incidents control: Histological based methods as reliable tools for fresh and frozen/thawed products discrimination
Freezing is one of the commonest methods applied for seafood shelf-life extension and long-term preservation. Nevertheless, the quality decay caused by water crystallization and cellular dehydration is responsible of significant reduction of the frozen-thawed products commercial value. Therefore, according to the European Legislation on food labelling, the declaration of freezing process represents a mandatory information for the protection of consumers’ rights. In fact, the lack of such information, besides entailing a non-conformity, can favor commercial frauds. The present work aims to present the development and validation of a histological approach, based on quali-quantitative histological markers, for the discrimination between fresh and thawed-frozen fishery products. In particular, the results of the application of the histological method on Merluccius merluccius and Octopus vulgaris, respectively selected as study models for white meat fish and cephalopods species, will be presented
- …