Narrowing the window of inflationary magnetogenesis

Abstract

We consider inflationary magnetogenesis where the conformal symmetry is broken by the term $f^2(\varphi )F_{\alpha \beta }{F}^{\alpha \beta }$. We assume that the magnetic field power spectrum today between 0.1 and $10^4$ Mpc is a power law, with upper and lower limits from observation. This fixes $f$ to be close to a power law in conformal time in the window during inflation when the modes observed today are generated. In contrast to previous work, we do not make any assumptions about the form of $f$ outside these scales. We cover all possible reheating histories, described by an average equation of state $-1/3<\bar{w}<1$. Requiring that strong coupling and large backreaction are avoided both at the background and perturbative level, we find the bound ${\delta }_{B_0}<5\times 10^{-15}{\left(\frac{r}{0.07}\right)}^{1/2}\kappa \mathrm{G}$ for the magnetic field generated by inflation, where $r$ is the tensor-to-scalar ratio and $\kappa$ is a constant related to the form of $f$. This estimate has an uncertainty of one order of magnitude related to our approximations. The parameter $\kappa$ is $<100$, and values $\gtrsim 1$ require a highly fine-tuned form of $f$; typical values are orders of magnitude smaller.

24 pages, 1 figure. v2: published version. Added references and clarifications, fixed a typo

References in corpus (7)

• Generation of Large-Scale Magnetic Fields in Single-Field Inflation
• Magnetic fields from inflation?
• Anisotropic Inflation from Vector Impurity
• The cosmic microwave background temperature bispectrum from scalar perturbations induced by primordial magnetic fields
• Universal upper limit on inflation energy scale from cosmic magnetic field
• Particle Production of Vector Fields: Scale Invariance is Attractive
• Large-scale magnetic fields, curvature fluctuations and the thermal history of the Universe

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• Model-independent constraints in inflationary magnetogenesis
• Circumventing the challenges in the choice of the non-conformal coupling function in inflationary magnetogenesis
• Cosmological magnetic braking and the formation of high-redshift, super-massive black holes
• Amplifying quantum discord during inflationary magnetogenesis through violation of parity