Lethal radiation from nearby supernovae helps to explain the small cosmological constant

TL;DR

This paper proposes that lethal radiation from nearby supernovae significantly influences the probability distribution of the cosmological constant, potentially explaining its small observed value by affecting galaxy habitability.

Contribution

It introduces a model incorporating supernova radiation effects into galaxy formation theory to explain the small cosmological constant's value.

Findings

Lethal supernova radiation reduces habitability in high stellar density regions.

The probability distribution of $\Lambda$ aligns with observations when supernova effects are considered.

Our location is likely near the edge of habitable stellar density regions in the galaxy.

Abstract

The observed value $\Lambda_{\rm obs}$ of the cosmological constant $\Lambda$ is extremely smaller than theoretical expectations, and the anthropic argument has been proposed as a solution to this problem because galaxies do not form when $\Lambda \gg \Lambda_{\rm obs}$. However, the contemporary galaxy formation theory predicts that stars form even with a high value of $\Lambda / \Lambda_{\rm obs} \sim$ 50, which makes the anthropic argument less persuasive. Here we calculate the probability distribution of $\Lambda$ using a model of cosmological galaxy formation, considering extinction of observers caused by radiation from nearby supernovae. The life survival probability decreases in a large $\Lambda$ universe because of higher stellar density. Using a reasonable rate of lethal supernovae, we find that the mean expectation value of $\Lambda$ can be close to $\Lambda_{\rm obs}$, and hence this effect may be essential to understand the small but nonzero value of $\Lambda$. It is predicted that we are located on the edge of habitable regions about stellar density in the Galaxy, which may be tested by future exoplanet studies.