# IWARA2018 - 8th International Workshop on Astronomy and Relativistic Astrophysics

8-15 September 2018
America/Lima timezone

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

11 Sep 2018, 14:50
20m
Talk

### Speaker

Tomonori Totani (Univ. of Tokyo)

### Description

The observed value $\Lambda_{obs}$ 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 $\Lambda \gg \Lambda_{obs}$. However, the contemporary galaxy formation theory predicts that stars form even with a high value of $\Lambda / \Lambda_{obs} \sim 50$, 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 $\Lambda_{obs},$ 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.

### Primary author

Tomonori Totani (Univ. of Tokyo)