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Cosmic microwave background bispectrum from primordial magnetic fields on large angular scales
T R Seshadri1, Kandaswamy Subramanian
1Department of Physics and Astrophysics, University of Delhi, Delhi 110007, India. trs@physics.du.ac.in
Physical Review Letters
|October 2, 2009
Summary
Primordial magnetic fields create unique non-Gaussian signals in the cosmic microwave background (CMB). This study proposes a new method to detect these fields by analyzing CMB bispectrum data, setting upper limits on their strength.
Area of Science:
- Cosmology
- Astrophysics
- Fundamental Physics
Background:
- Primordial magnetic fields leave unique imprints on the cosmic microwave background (CMB).
- These fields induce non-Gaussian signals in the CMB at the lowest order, unlike scalar perturbations from inflation.
- Analyzing these non-Gaussianities offers a novel avenue to probe the early universe.
Purpose of the Study:
- To propose and validate a new method for detecting stochastic primordial magnetic fields.
- To exploit the characteristic non-Gaussianity induced by magnetic fields in the CMB.
- To establish observational constraints on the strength of primordial magnetic fields.
Main Methods:
- Computation of the CMB bispectrum induced by stochastic primordial magnetic fields.
- Analysis of the bispectrum on large angular scales.
- Application of observational limits on the CMB bispectrum to constrain magnetic field strength.
Main Results:
- A typical value for the induced CMB bispectrum is found to be approximately 10^-22 for a magnetic field strength of 3 nG.
- The proposed method provides a distinct signature of primordial magnetic fields.
- Upper limits on the strength of primordial magnetic fields are established at approximately 35 nG.
Conclusions:
- The CMB bispectrum serves as a powerful probe for stochastic primordial magnetic fields.
- Observational constraints on the CMB bispectrum can effectively limit the strength of these primordial fields.
- This research opens new possibilities for understanding the origin and evolution of magnetic fields in the early universe.
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