Related Experiment Video
Updated: Jun 5, 2026
07:46
Setting Limits on Supersymmetry Using Simplified Models
Published on: November 15, 2013
Non-Gaussianity in axion N-flation models.
Soo A Kim1, Andrew R Liddle, David Seery
1Department of Astronomy and Space Science, Kyung Hee University, Yong-in, South Korea.
Physical Review Letters
|January 15, 2011
Summary
We analyzed multifield axion N-flation using the full potential, finding large, detectable non-Gaussianity (fNL). This differs from quadratic approximations and fits observational data, suggesting a generic feature in hilltop inflation models.
Area of Science:
- Cosmology
- Theoretical Physics
- Particle Physics
Background:
- The N-flation model is a key framework for cosmic inflation.
- Previous studies often used quadratic approximations for the potential.
- Understanding non-Gaussianity is crucial for testing inflationary models.
Purpose of the Study:
- To investigate perturbations in the multifield axion N-flation model with a full cosine potential.
- To compare results with previous analyses using quadratic approximations.
- To determine the potential for detectable non-Gaussianity in this model.
Main Methods:
- Analysis of perturbations within the multifield axion N-flation model.
- Utilizing the complete cosine potential, not a quadratic approximation.
- Calculating the tensor-to-scalar ratio, scalar spectral index, and bispectrum non-Gaussianity parameter (fNL).
Main Results:
- Significant deviations from previous quadratic approximation analyses.
- Lower values for the tensor-to-scalar ratio and scalar spectral index, consistent with observations.
- Potentially large and detectable bispectrum non-Gaussianity (fNL), reaching up to 100 for specific axion decay constants.
Conclusions:
- The full cosine potential in multifield axion N-flation yields significant differences from quadratic approximations.
- The model provides an acceptable fit to current cosmological observations.
- Large non-Gaussianity is a generic and potentially detectable feature in multifield hilltop inflation models.
More Related Videos
Related Concept Videos
01:20Gauss's Law: Cylindrical Symmetry
A charge distribution has cylindrical symmetry if the charge density depends only upon the distance from the axis of the cylinder and does not vary along the axis or with the direction about the axis. In other words, if a system varies if it is rotated around the axis or shifted along the axis, it does not have cylindrical symmetry. In real systems, we do not have infinite cylinders; however, if the cylindrical object is considerably longer than the radius from it that we are interested in,...
01:27Gauss's Law: Planar Symmetry
A planar symmetry of charge density is obtained when charges are uniformly spread over a large flat surface. In planar symmetry, all points in a plane parallel to the plane of charge are identical with respect to the charges. Suppose the plane of the charge distribution is the xy-plane, and the electric field at a space point P with coordinates (x, y, z) is to be determined. Since the charge density is the same at all (x, y) - coordinates in the z = 0 plane, by symmetry, the electric field at P...
01:07Gauss's Law
If a closed surface does not have any charge inside where an electric field line can terminate, then the electric field line entering the surface at one point must necessarily exit at some other point of the surface. Therefore, if a closed surface does not have any charges inside the enclosed volume, then the electric flux through the surface is zero. What happens to the electric flux if there are some charges inside the enclosed volume? Gauss's law gives a quantitative answer to this question.
01:26Gauss's Law: Spherical Symmetry
A charge distribution has spherical symmetry if the density of charge depends only on the distance from a point in space and not on the direction. In other words, if the system is rotated, it doesn't look different. For instance, if a sphere of radius R is uniformly charged with charge density ρ0, then the distribution has spherical symmetry. On the other hand, if a sphere of radius R is charged so that the top half of the sphere has a uniform charge density ρ1 and the bottom half has a uniform...
01:28Symmetry in Maxwell's Equations
Once the fields have been calculated using Maxwell's four equations, the Lorentz force equation gives the force that the fields exert on a charged particle moving with a certain velocity. The Lorentz force equation combines the force of the electric field and of the magnetic field on the moving charge. Maxwell's equations and the Lorentz force law together encompass all the laws of electricity and magnetism. The symmetry that Maxwell introduced into his mathematical framework may not be...
01:15Unsymmetric Bending - Angle of Neutral Axis
Unsymmetrical bending occurs when a structural member is subjected to bending moments in a plane that does not align with the member's principal axes. This scenario typically arises in beams and other structural components when loads are applied at non-ideal angles, introducing complexities in stress analysis.
When a bending moment is applied at an angle θ concerning the vertical axis of a symmetrical member, it can be resolved into components along the member's principal centroidal axes. The...
When a bending moment is applied at an angle θ concerning the vertical axis of a symmetrical member, it can be resolved into components along the member's principal centroidal axes. The...