Zenith Grant Awardee
Raphael Bousso
University of California, Berkeley
Co-Investigators
Project Title
The Future of the Multiverse
Project Summary
The arrow of time is the question of why the universe started out so well ordered that even today, it remains far from the state of maximum disorder that it strives towards. A popular but somewhat ad-hoc strategy is to look for a law that requires the universe to begin orderly. In eternal inflation, this cannot work. Instead, the emergence of an arrow of time depends in on the lifetime of the vacua populating the landscape of string theory–a fascinating connection that I will explore. Eternal inflation leads to infinities that must be tamed to make predictions. Leading approaches to this problem tell us to count everything that happens until a particular time. This "cutoff" was regarded as a mere computational trick, but recent work indicates that it comes with heavy baggage. Some ob jects may last to the end of time, when they are disrupted for no reason other than the cutoff. We must understand this bizarre conclusion in a more physical way, by identifying a real mechanism that brings about the end of time and justifies the cutoff. The only alternative is to find an entirely new way of thinking about eternal inflation.
Technical Abstract
This project will focus on two issues. Eternal inflation transforms an old problem–the origin of the arrow of time–and introduces a new problem, the end of time.
In eternal inflation, special initial conditions are erased by cosmological attractor behavior. Therefore, the arrow of time can only emerge dynamically. Recent work indicates that it will indeed emerge, if all metastable de Sitter vacua decay sufficiently fast. I intend to demonstrate this connection rigorously. This would reduce the arrow of time problem to a nontrivial constraint on the landscape of string theory, which can in principle be checked.
Time cutoffs on eternal inflation are widely used to regulate divergences and compute probabilities. Recent work has shown that such cutoffs are necessarily physical, since they are encountered by a finite fraction of matter systems. My research will investigate the implications of this result: Either geometric cutoffs are not the right way to compute probabilities, in which case we will need to develop entirely new tools for the study of eternal inflation. Or the end of time is a real possibility, which challenges us to identify a physical mechanism underlying the cutoff.
QSpace Latest
PressRelease: Shining a light on the roots of plant “intelligence”
All living organisms emit a low level of light radiation, but the origin and function of these ‘biophotons’ are not yet fully understood. An international team of physicists, funded by the Foundational Questions Institute, FQxI, has proposed a new approach for investigating this phenomenon based on statistical analyses of this emission. Their aim is to test whether biophotons can play a role in the transport of information within and between living organisms, and whether monitoring biophotons could contribute to the development of medical techniques for the early diagnosis of various diseases. Their analyses of the measurements of the faint glow emitted by lentil seeds support models for the emergence of a kind of plant ‘intelligence,’ in which the biophotonic emission carries information and may thus be used by plants as a means to communicate. The team reported this and reviewed the history of biophotons in an article in the journal Applied Sciences in June 2024.