Preparation to the CMB PLANCK data analysis, estimation of the contamination due to the galactic polarized emissions

This work is point of the preparation to the analysis of the PLANCK satellite data. The PLANCK satellite is an ESA mission which has been launched the 14th of may 2009 and is dedicaced to the measurement of the Cosmic Microwave Background (CMB) in temperature and polarization. The presence of diffuse Galactic polarized emissions disturb the measurement of the CMB anisotropies, in particular in polarization. Therefore a precise knowledge of these emissions is needed to obtain the level of accuracy required for PLANCK. In this context, we have developed and implemented a coherent 3D model of the two mains polarized Galactic emissions : synchrotron and thermal dust. We have compared these models to preexisting data: the 23 GHz band of the WMAP data, the 353 GHz Archeops data and the 408 MHz all-sky continuum survey. We extrapolate these models to the frequencies where the CMB dominates and we are able to estimate the contribution of polarized foreground emissions to the polarized CMB emission measured with PLANCK.Comment: Proceeding of the International Workshop on Cosmic Structure and Evolution - Cosmology2009, September 23-25, 2009 Bielefeld, German

Material Adverse Change Clauses and Acquisition Dynamics

Material-Adverse-Change clauses (MACs) are present in over 90% of acquisition agreements. These clauses are the outcome of extensive negotiation and exhibit substantial cross-sectional variation in the number and types of events that are excluded from being ‘material adverse events’ (MAEs). MAEs are the underlying cause of more than 50% of acquisition terminations and 60% of acquisition renegotiations. Moreover, these renegotiations lead to substantial changes in the price offered to target shareholders (13-15%). We find that acquisitions with fewer MAE exclusions are characterized by wider arbitrage spreads (i.e., the difference between the price offered to target shareholders and the current market price of the target’s shares) during the acquisition period and are associated with higher offer premiums. We conclude that material adverse change clauses have an economically important impact on the dynamics of corporate acquisitions and stock prices during the acquisition period.Acquisitions, Contractual mechanisms, Material-Adverse-Change clause (MACs), Material-Adverse Event (MAE) exclusions, merger agreement, risk allocation, flexibility

Bayesian blind component separation for Cosmic Microwave Background observations

We present a technique for the blind separation of components in CMB data. The method uses a spectral EM algorithm which recovers simultaneously component templates, their emission law as a function of wavelength, and noise levels. We test the method on Planck HFI simulated observations featuring 3 astrophysical components.Comment: 15 pages, 5 figures, to appear in the Proceedings of the MAXENT 2001 international worksho

Non-linear Preheating with Scalar Metric Perturbations

We have studied preheating of field perturbations in a 3-dimensional lattice including the effect of scalar metric perturbations, in two generic models of inflation: chaotic inflation with a quartic potential, and standard hybrid inflation. We have prepared the initial state for the classical evolution of the system with vanishing vector and tensor metric perturbations, consistent with the constraint equations, the energy and momentum constraints. The non-linear evolution inevitably generates vector and tensor modes, and this reflects on how well the constraint equations are fulfilled during the evolution. The induced preheating of the scalar metric perturbations is not large enough to backreact onto the fields, but it could affect the evolution of vector and tensor modes. This is the case in hybrid inflation for some values of the coupling $g$ and the height of potential $V_0^{1/4}$. For example with $V_0^{1/4} \simeq 10^{15}$ GeV, preheating of scalar perturbations is such that their source term in the evolution equation of tensor and vector becomes comparable to that of the field anisotropic stress.Comment: 15 pages, 12 eps figure

r-process enrichment of ultra-faint dwarf galaxies by fast merging double neutron stars

The recent aLIGO/aVirgo discovery of gravitational waves from the neutron star merger (NSM) GW170817 and the follow up kilonova observations have shown that NSMs produce copious amount of r-process material. However, it is difficult to reconcile the large natal kicks and long average merging times of Double Neutron Stars (DNSs), with the levels of r-process enrichment seen in ultra faint dwarf (UFD) galaxies such as Reticulum II and Tucana III. Assuming that such dwarf systems have lost a significant fraction of their stellar mass through tidal stripping, we conclude that contrary to most current models, it is the DNSs with rather large natal kicks but very short merging timescales that can enrich UFD-type galaxies. These binaries are either on highly eccentric orbits, or form with very short separations due to an additional mass-transfer between the first-born neutron star and a naked helium star, progenitor of the second-born neutron star. These DNSs are born with a frequency that agrees with the statistics of the r-process UFDs, and merge well within the virial radius of their host halos, therefore contributing significantly to their r-process enrichment.Comment: Accepted for publication in Ap

The scalar sector in the Myers-Pospelov model

We construct a perturbative expansion of the scalar sector in the Myers-Pospelov model, up to second order in the Lorentz violating parameter and taking into account its higher-order time derivative character. This expansion allows us to construct an hermitian positive-definite Hamiltonian which provides a correct basis for quantization. Demanding that the modified normal frequencies remain real requires the introduction of an upper bound in the magnitude |k| of the momentum, which is a manifestation of the effective character of the model. The free scalar propagator, including the corresponding modified dispersion relations, is also calculated to the given order, thus providing the starting point to consider radiative corrections when interactions are introduced.Comment: Published in AIP Conf.Proc.977:214-223,200