119,531 research outputs found
The triangle-free graphs with rank 6
The rank of a graph G is defined to be the rank of its adjacency matrix A(G).
In this paper we characterize all connected triangle-free graphs with rank 6
Large Nonlocal Non-Gaussianity from a Curvaton Brane
We use a generalized delta N formalism to study the generation of the
primordial curvature perturbation in the curvaton brane scenario inspired by
stringy compactifications. We note that the non-Gaussian features, especially
the trispectra, crucially depend on the decay mechanism in a general curvaton
scenario. Specifically, we study the bispectra and trispectra of the curvaton
brane model in detail to illustrate the importance of curvaton decay in
generating nonlinear fluctuations. When the curvaton brane moves
nonrelativistically during inflation, the shape of non-Gaussianity is local,
but the corresponding size is different from that in the standard curvaton
scenario. When the curvaton brane moves relativistically in inflationary stage,
the shape of non-Gaussianity is of equilateral type.Comment: 24 pages, 2 figure
Testing quantum gravity effects with latest CMB observations
Inspired by quantum gravitational physics, the approach of non-commutative
(NC) phase space leads to a modified dispersion relation of gravitational
waves. This feature, if applied to the very early universe, gives rise to a
modified power spectrum of primordial tensor perturbations with a suppression
of power on large scales. We confront this phenomenon with the BICEP2 and
Planck experiments, and show that inflation with the modified dispersion
relation can simultaneously fit the observations better than the standard
inflationary paradigm. In particular, the numerical result implies that with
the latest cosmological microwave background (CMB) observations, a quantum
gravity modified power spectrum of primordial tensor modes is preferred at a
statistical significance of more than compared with the minimal
model. Our study indicates that the potential tension between the BICEP2 and
Planck data may be resolved by quantum gravity effects.Comment: 5 pages, 2 figures, comments are welcom
- …