135 research outputs found
Primordial Circular Polarization in the Cosmic Microwave Background
Circular ("V-mode") polarization is expected to be vanishing in the CMB,
since it is not produced in Thomson scattering. However, considering that the
conventional CMB anisotropies are generated via an early universe mechanism
such as inflation or a bouncing scenario, it is possible that circular
polarization could be primordially produced and survive to the surface of last
scattering. We study this in detail, and find a large class of inflationary
models that produce a nearly scale invariant spectrum of scalar V-mode
anisotropies. We study the inflationary production and subsequent evolution via
the Boltzmann hierarchy, and show that V-mode polarization present in the CMB
is suppressed by a factor of at least relative to the primordial
, consistent with expectation of negligible V-mode polarization from
inflation. We consider alternative possibilities for sourcing primordially,
such as the V-mode polarization induced by circularly polarized primordial
gravitational waves, or producing after inflation, via new interactions at
recombination.Comment: 8 pages, 1 figure. v2: references added. v3:matches published
version. v4:typo correcte
The Hubble Web: The Dark Matter Problem and Cosmic Strings
I propose a reinterpretation of cosmic dark matter in which a rigid network
of cosmic strings formed at the end of inflation. The cosmic strings fulfill
three functions: At recombination they provide an accretion mechanism for
virializing baryonic and warm dark matter into disks. These cosmic strings
survive as configurations which thread spiral and elliptical galaxies leading
to the observed flatness of rotation curves and the Tully-Fisher relation. We
find a relationship between the rotational velocity of the galaxy and the
string tension and discuss the testability of this model.Comment: 5 page
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