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arXiv · 2506.10131

Positron Signal from the Early Universe

L. Stodolsky·J. Silk
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Abstract

Bursts from the very early universe may lead to a detectable signal via the production of positrons, whose annihilation gives an observable X-ray signal. Using the absorption parameters for the annihilation photons of 511 keV, it is found that observable photons would originate at a red-shift around $z\approx$ 200-300, resulting in soft X-rays of energy $\sim$ 2-3 keV at present. Positrons are expected to be absent at these times or red-shifts in the standard picture of the early universe. Detection of the X-rays would thus provide dramatic support for the hypothesis of the bursts, explosive events at very early times. We urge the search for such a signal.

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L. Stodolsky, J. Silk. 2025-06-11. Positron Signal from the Early Universe. https://arxiv.org/abs/2506.10131

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