2,925 research outputs found
Symplectic matrices with predetermined left eigenvalues
We prove that given four arbitrary quaternion numbers of norm 1 there always
exists a symplectic matrix for which those numbers are left
eigenvalues. The proof is constructive. An application to the LS category of
Lie groups is given.Comment: 7 page
Model of the polarized foreground diffuse Galactic emissions from 33 to 353 GHz
We present 3D models of the Galactic magnetic field including regular and
turbulent components, and of the distribution of matter in the Galaxy including
relativistic electrons and dust grains. By integrating along the line of sight,
we construct maps of the polarized Galactic synchrotron and thermal dust
emissions for each of these models. We perform a likelihood analysis to compare
the maps of the Ka, Q, V and W bands of the Wilkinson Microwave Anisotropy
Probe (Wmap) and the 353 GHz Archeops data to the models obtained by varying
the pitch angle of the regular magnetic field, the relative amplitude of the
turbulent magnetic field and the extrapolation spectral indices of the
synchrotron and thermal dust emissions. The best-fit parameters obtained for
the different frequency bands are very similar and globally the data seem to
favor a negligible isotropic turbulent magnetic field component at large
angular scales (an anisotropic line-of-sight ordered component can not be
studied using these data). From this study, we conclude that we are able to
propose a consistent model of the polarized diffuse Galac- tic synchrotron and
thermal dust emissions in the frequency range from 33 to 353 GHz, where most of
the CMB studies are performed and where we expect a mixture of these two main
foreground emissions. This model can be very helpful to estimate the
contamination by foregrounds of the polarized CMB anisotropies, for experiments
like the Planck satellite.Comment: 22 pages, 4 figure
Lusternik-Schnirelmann category of simplicial complexes and finite spaces
In this paper we establish a natural definition of Lusternik-Schnirelmann
category for simplicial complexes via the well known notion of contiguity. This
category has the property of being homotopy invariant under strong
equivalences, and only depends on the simplicial structure rather than its
geometric realization.
In a similar way to the classical case, we also develop a notion of geometric
category for simplicial complexes. We prove that the maximum value over the
homotopy class of a given complex is attained in the core of the complex.
Finally, by means of well known relations between simplicial complexes and
posets, specific new results for the topological notion of category are
obtained in the setting of finite topological spaces.Comment: 18 pages, 10 figures, this is a new version with some minor changes
and a new exampl
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