159 research outputs found
Local Features with Large Spiky non-Gaussianities during Inflation
We provide a dynamical mechanism to generate localized features during
inflation. The local feature is due to a sharp waterfall phase transition which
is coupled to the inflaton field. The key effect is the contributions of
waterfall quantum fluctuations which induce a sharp peak on the curvature
perturbation which can be as large as the background curvature perturbation
from inflaton field. Due to non-Gaussian nature of waterfall quantum
fluctuations a large spike non-Gaussianity is produced which is narrowly peaked
at modes which leave the Hubble radius at the time of phase transition. The
large localized peaks in power spectrum and bispectrum can have interesting
consequences on CMB anisotropies.Comment: 22 pages, 2 figure
Curvature perturbation and waterfall dynamics in hybrid inflation
We investigate the parameter spaces of hybrid inflation model with special
attention paid to the dynamics of waterfall field and curvature perturbations
induced from its quantum fluctuations. Depending on the inflaton field value at
the time of phase transition and the sharpness of the phase transition
inflation can have multiple extended stages. We find that for models with mild
phase transition the induced curvature perturbation from the waterfall field is
too large to satisfy the COBE normalization. We investigate the model parameter
space where the curvature perturbations from the waterfall quantum fluctuations
vary between the results of standard hybrid inflation and the results obtained
here.Comment: V2: Minor revisions, references added, JCAP published versio
On the weak coupling spectrum of N=2 supersymmetric SU(n) gauge theory
The weak coupling spectrum of BPS saturated states of pure
supersymmetric SU gauge theory is investigated. The method uses known
results on the dyon spectrum of the analogous theory with supersymmetry,
along with the action on these states of the semi-classical monodromy
transformations. For dyons whose magnetic charge is not a simple root of the
Lie algebra, it is found that the weak coupling region is divided into a series
of domains, for which the dyons have different electric charge, separated by
walls on which the dyons decay. The proposed spectrum is shown to be consistent
with the exact solution of the theory at strong coupling in the sense that the
states at weak coupling can account for the singularities at strong coupling.Comment: 19 pages, plain tex with macro included, 6 figures included using
psfig.te
The Importance of Slow-roll Corrections During Multi-field Inflation
We re-examine the importance of slow-roll corrections during the evolution of
cosmological perturbations in models of multi-field inflation. We find that in
many instances the presence of light degrees of freedom leads to situations in
which next to leading order slow-roll corrections become significant. Examples
where we expect such corrections to be crucial include models in which modes
exit the Hubble radius while the inflationary trajectory undergoes an abrupt
turn in field space, or during a phase transition. We illustrate this with two
examples -- hybrid inflation and double quadratic inflation. Utilizing both
analytic estimates and full numerical results, we find that corrections can be
as large as 20%. Our results have implications for many existing models in the
literature, as these corrections must be included to obtain accurate
observational predictions -- particularly given the level of accuracy expected
from CMB experiments such as PlanckComment: v1: 21 pages, 3 figures, 1 appendix. v2: clarifications to
{\S}{\S}2.1, 3.1 and 4, {\S}5.3 added, references added, results unchanged.
Matches published version in JCA
Effects of Variable Newton Constant During Inflation
In this paper the effects of time-dependent Newton constant G during
inflation are studied. We present the formalism of curvature perturbations in
an inflationary system with a time-dependent Newton constant. As an example we
consider a toy model in which G undergoes a sudden change during inflation. By
imposing the appropriate matching conditions the imprints of this sharp change
in G on curvature perturbation power spectrum are studied. We show that if G
increases (decreases) during the transition the amplitude of curvature
perturbations on large scales decreases (increases). In our model with a sudden
change in G a continuous sinusoidal modulations on curvature power spectrum is
induced. However, in a realistic scenario in which the change in G has some
finite time scale we expect these sinusoidal modulations to be damped on short
scales. The generated features may be used to explain the observed glitches on
CMB power spectrum. This puts a bound on during inflation of roughly
the same order as current bounds on during the entire observed age
of the universe.Comment: 15 pages, 2 figures. Typos fixed, new references added, conforms with
the journal versio
Issues on Generating Primordial Anisotropies at the End of Inflation
We revisit the idea of generating primordial anisotropies at the end of
inflation in models of inflation with gauge fields. To be specific we consider
the charged hybrid inflation model where the waterfall field is charged under a
U(1) gauge field so the surface of end of inflation is controlled both by
inflaton and the gauge fields. Using delta N formalism properly we find that
the anisotropies generated at the end of inflation from the gauge field
fluctuations are exponentially suppressed on cosmological scales. This is
because the gauge field evolves exponentially during inflation while in order
to generate appreciable anisotropies at the end of inflation the spectator
gauge field has to be frozen and scale invariant. We argue that this is a
generic feature, that is, one can not generate observable anisotropies at the
end of inflation within an FRW background.Comment: V3: new references added, JCAP published versio
Large-scale Perturbations from the Waterfall Field in Hybrid Inflation
We estimate large-scale curvature perturbations from isocurvature
fluctuations in the waterfall field during hybrid inflation, in addition to the
usual inflaton field perturbations. The tachyonic instability at the end of
inflation leads to an explosive growth of super-Hubble scale perturbations, but
they retain the steep blue spectrum characteristic of vacuum fluctuations in a
massive field during inflation. The power spectrum thus peaks around the
Hubble-horizon scale at the end of inflation. We extend the usual delta-N
formalism to include the essential role of these small fluctuations when
estimating the large-scale curvature perturbation. The resulting curvature
perturbation due to fluctuations in the waterfall field is second-order and the
spectrum is expected to be of order 10^{-54} on cosmological scales.Comment: 10 pages, 4 figures; v2 comments added on application of delta-N
formalism including Hubble scale fluctuation
Dyon electric charge and fermion fractionalization
A first principles calculation of the quantum corrections to the electric
charge of a dyon in an N=2 gauge theory with arbitrary gauge group is
presented. These corrections arise from the fermion fields via the mechanism of
fermion fractionalization. For a dyon whose magnetic charge is a non-simple
co-root, the correction is a discontinuous function on the moduli space of
vacua and the discontinuities occur precisely on co-dimension one curves on
which the dyon decays. In this way, the complete spectrum of dyons at weak
coupling is found for a theory with any gauge group. It is shown how this
spectrum is consistent with the semi-classical monodromies.Comment: 19 pages, plain tex with macro included, 3 figures included using
psfi
Music in advertising and consumer identity: The search for Heideggerian authenticity
This study discusses netnographic findings involving 472 YouTube postings categorized to identify themes regarding consumers’ experience of music in advertisements. Key themes relate to musical taste, musical indexicality, musical repetition and musical authenticity. Postings reveal how music conveys individual taste and is linked to personal memories and Heidegger’s coincidental time where moments of authenticity may be triggered in a melee of emotions, memories and projections. Identity protection is enabled as consumers frequently resist advertisers’ attempts to use musical repetition to impose normative identity. Critiques of repetition in the music produce Heideggerian anxiety leading to critically reflective resistance. Similarly, where advertising devalues the authenticity of iconic pieces of music, consumers often resist such authenticity transgressions as a threat to their own identity. The Heideggerian search for meaning in life emphasizes the significance of philosophically driven ideological authenticity in consumers’ responses to music in advertisements
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