396 research outputs found
Non-Gaussianity and Excursion Set Theory: Halo Bias
We study the impact of primordial non-Gaussianity generated during inflation
on the bias of halos using excursion set theory. We recapture the familiar
result that the bias scales as on large scales for local type
non-Gaussianity but explicitly identify the approximations that go into this
conclusion and the corrections to it. We solve the more complicated problem of
non-spherical halos, for which the collapse threshold is scale dependent.Comment: 13 pages, 3 figures. v2 references added. Matches published versio
Choreography, controversy and child sex abuse: Theoretical reflections on a cultural criminological analysis of dance in a pop music video
This article was inspired by the controversy over claims of ‘pedophilia!!!!’ undertones and the ‘triggering’ of memories of childhood sexual abuse in some viewers by the dance performance featured in the music video for Sia’s ‘Elastic Heart’ (2015). The case is presented for acknowledging the hidden and/or overlooked presence of dance in social scientific theory and cultural studies and how these can enhance and advance cultural criminological research. Examples of how these insights have been used within other disciplinary frameworks to analyse and address child sex crime and sexual trauma are provided, and the argument is made that popular cultural texts such as dance in pop music videos should be regarded as significant in analysing and tracing public perceptions and epistemologies of crimes such as child sex abuse
Neutrinos and Future Concordance Cosmologies
We review the free parameters in the concordance cosmology, and those which
might be added to this set as the quality of astrophysical data improves. Most
concordance parameters encode information about otherwise unexplored aspects of
high energy physics, up to the GUT scale via the "inflationary sector," and
possibly even the Planck scale in the case of dark energy. We explain how
neutrino properties may be constrained by future astrophysical measurements.
Conversely, future neutrino physics experiments which directly measure these
parameters will remove uncertainty from fits to astrophysical data, and improve
our ability to determine the global properties of our universe.Comment: Proceedings of paper given at Neutrino 2008 meeting (by RE
Dark photon dark matter from an oscillating dilaton
We present a mechanism for generating ultralight dark photon dark matter in
the early Universe via a dilatonlike scalar field coupled to the dark photon's
kinetic term. Energy is initially stored in the condensate of the dilaton,
which resonantly produces dark photons when it begins oscillating in the early
Universe. While similar scenarios with axion--dark-photon couplings require
large coupling coefficients to fully populate the dark photon, the dilatonic
coupling features a unique regime: when the dark photon's mass is half that of
the dilaton, dark photons are copiously produced even when the dilaton
undergoes small-amplitude oscillations. Scenarios consistent with the cosmic
microwave background allow for ultralight vector dark matter with mass as light
as eV.Comment: 9 pages, 1 figur
Reionization and the large-scale 21 cm-cosmic microwave background cross correlation
Of the many probes of reionization, the 21 cm line and the cosmic microwave
background (CMB) are among the most effective. We examine how the
cross-correlation of the 21 cm brightness and the CMB Doppler fluctuations on
large angular scales can be used to study this epoch. We employ a new model of
the growth of large scale fluctuations of the ionized fraction as reionization
proceeds. We take into account the peculiar velocity field of baryons and show
that its effect on the cross correlation can be interpreted as a mixing of
Fourier modes. We find that the cross-correlation signal is strongly peaked
toward the end of reionization and that the sign of the correlation should be
positive because of the inhomogeneity inherent to reionization. The signal
peaks at degree scales (l~100) and comes almost entirely from large physical
scales (k~0.01 Mpc). Since many of the foregrounds and noise that plague low
frequency radio observations will not correlate with CMB measurements, the
cross correlation might appear to provide a robust diagnostic of the
cosmological origin of the 21 cm radiation around the epoch of reionization.
Unfortunately, we show that these signals are actually only weakly correlated
and that cosmic variance dominates the error budget of any attempted detection.
We conclude that the detection of a cross-correlation peak at degree-size
angular scales is unlikely even with ideal experiments.Comment: 15 pages, 4 figures, submitted to MNRA
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