## Abstract

We propose a new approach for multiverse analysis based on computational complexity, which leads to a new family of “computational” measure factors. By defining a cosmology as a space–time containing a vacuum with specified properties (for example small cosmological constant) together with rules for how time evolution will produce the vacuum, we can associate global time in a multiverse with clock time on a supercomputer which simulates it. We argue for a principle of “limited computational complexity” governing early universe dynamics as simulated by this supercomputer, which translates to a global measure for regulating the infinities of eternal inflation. The rules for time evolution can be thought of as a search algorithm, whose details should be constrained by a stronger principle of “minimal computational complexity”. Unlike previously studied global measures, ours avoids standard equilibrium considerations and the well-known problems of Boltzmann Brains and the youngness paradox. We also give various definitions of the computational complexity of a cosmology, and argue that there are only a few natural complexity classes.

Original language | English (US) |
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Pages (from-to) | 93-127 |

Number of pages | 35 |

Journal | Annals of Physics |

Volume | 392 |

DOIs | |

State | Published - May 2018 |

Externally published | Yes |

### Bibliographical note

Publisher Copyright:© 2018 Elsevier Inc.

## Keywords

- Computational complexity
- Measures
- Multiverse
- String theory