63 research outputs found
Hunting for Chameleons in ALP searches
We discuss some recent developments in chameleon models presented at the
Fourth Patras workshop on Axions, WIMPs and WISPs. In particular we discuss the
possibility of searching for chameleons in axion-like particle searches
performed in the laboratory. Such chameleons may couple to both photons and
matter with different coupling strengths. We discuss the exciting possibility
of searching for these dark energy candidates in quantum vacuum experiments -
in particular for the GammeV experiment at Fermilab.Comment: 4 pages, 1 figure, Contribution to the ``4th Patras Workshop on
Axions, WIMPs and WISPs'', 18-21 June 2008, Hamburg, German
Chameleons on the Racetrack
We modify the ansatz for embedding chameleon scalars in string theory
proposed in [1] by considering a racetrack superpotential with two KKLT-type
exponentials instead of one. This satisfies all experimental
constraints, while also allowing for the chameleon to be light enough on
cosmological scales to be phenomenologically interesting.Comment: 11 pages, 1 figur
A natural cosmological constant from chameleons
We present a simple model where the effective cosmological constant appears
from chameleon scalar fields. For a Kachru-Kallosh-Linde-Trivedi
(KKLT)-inspired form of the potential and a particular chameleon coupling to
the local density, patches of approximately constant scalar field potential
cluster around regions of matter with density above a certain value, generating
the effect of a cosmological constant on large scales. This construction
addresses both the cosmological constant problem (why is so small,
yet nonzero) and the coincidence problem (why is comparable to the
matter density now).Comment: 9 pages; explanations, footnotes and references adde
Alignments of parity even/odd-only multipoles in CMB
We compare the statistics of parity even and odd multipoles of the cosmic
microwave background (CMB) sky from PLANCK full mission temperature
measurements. An excess power in odd multipoles compared to even multipoles has
previously been found on large angular scales. Motivated by this apparent
parity asymmetry, we evaluate directional statistics associated with even
compared to odd multipoles, along with their significances. Primary tools are
the \emph{Power Tensor} and \emph{Alignment Tensor} statistics. We limit our
analysis to the first sixty multipoles i.e., . We find no evidence
for statistically unusual alignments of even parity multipoles. More than one
independent statistic finds evidence for alignments of anisotropy axes of odd
multipoles, with a significance equivalent to or more. The
robustness of alignment axes is tested by making galactic cuts and varying the
multipole range. Very interestingly, the region spanned by the (a)symmetry axes
is found to broadly contain other parity (a)symmetry axes previously observed
in the literature.Comment: 13 pages, 13 figures, Matches the version accepted in MNRA
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