70 research outputs found
Constraints on small-scale cosmological fluctuations from SNe lensing dispersion
We provide predictions on small-scale cosmological density power spectrum
from supernova lensing dispersion. Parameterizing the primordial power spectrum
with running and running of running of the spectral index, we
exclude large positive and parameters which induce too large
lensing dispersions over current observational upper bound. We ran cosmological
N-body simulations of collisionless dark matter particles to investigate
non-linear evolution of the primordial power spectrum with positive running
parameters. The initial small-scale enhancement of the power spectrum is
largely erased when entering into the non-linear regime. For example, even if
the linear power spectrum at is enhanced by orders
of magnitude, the enhancement much decreases to a factor of at late time
(). Therefore, the lensing dispersion induced by the dark matter
fluctuations weakly constrains the running parameters. When including
baryon-cooling effects (which strongly enhance the small-scale clustering), the
constraint is comparable or tighter than the PLANCK constraint, depending on
the UV cut-off. Further investigations of the non-linear matter spectrum with
baryonic processes is needed to reach a firm constraint.Comment: 11 pages, 9 figures. Submitted to MNRA
The Quantum Focusing Conjecture and the Improved Energy Condition
By rearranging its terms, the Quantum Focusing Conjecture (QFC) can be viewed
as a quantum energy condition, and we can consider various limits. A recent
restricted version is a limiting form where the quantum focusing vanishes
, and has been proven for Braneworld scenario. As a
result, we derive an improved quantum null energy condition (INEC) , that can be proven with field theory techniques. We sketch
the beginning of a proof, and briefly discuss possible interpretations in the
absence of one.Comment: 5 pages, 2 figure
Hierarchical Axion Inflation
We propose a new field theory mechanism for generating an effective
trans-Planckian decay constant from sub-Planckian ones. Using the minimal two
axions and a hierarchy between two axion decay constants is sufficient for
realizing inflation through non-perturbative effects only and with minimal
tuning. The inflationary motion is kept entirely within a sub-Planckian domain.
We outline possible strategies of embedding the model in a string theory setup.Comment: REVTeX, 5 pages, 2 figures, added refs, changed the numerical
parameter values of the stringy example, removed ED1's from the
superpotentia
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