87 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
Non-Kahler Resolved Conifold, Localized Fluxes in M-Theory and Supersymmetry
The known supergravity solution for wrapped D5-branes on the two-cycle of a
Kahler resolved conifold is in general ISD but not supersymmetric, with the
supersymmetry being broken by the presence of (1, 2) fluxes. However if we
allow a non-Kahler metric on the resolved conifold, supersymmetry can easily be
restored. The vanishing of the (1, 2) fluxes here corresponds to, under certain
conformal rescalings of the metric, the torsion class constraints. We construct
a class of explicit non-Kahler metrics on the resolved conifold satisfying the
constraints. All this can also be studied from M-theory, where the fluxes and
branes become non-localized G-fluxes on deformed Taub-NUT spaces.
Interestingly, the gauge fluctuations on the wrapped D5-branes appear now as
localized G-fluxes in M-theory. These localized fluxes are related to certain
harmonic two-forms that are normalizable. We compute these forms explicitly and
discuss how new constraints on the geometry of the non-Kahler manifolds may
appear from M-theory considerations.Comment: 40 pages, no figures, LaTeX JHEP forma
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