Zenith Grant Awardee
Dr. Alexander Vilenkin
Tufts University
Co-Investigators
Jaume Garriga, <i>Universitat de Baecelona</i><br>Vitaly Vanchurin, <i>Tufts University</i>
Project Title
Probabilities in the Landscape
Project Summary
Models of cosmic inflation, combined with recent developments in string theory, point to a new cosmological paradigm, where distant parts of the universe have diverse properties and different particle physics. Inflationary scenarios, which explain the observed homogeneity of the universe, predict that on very large scales the universe is very inhomogeneous, with vast regions still in the state of exponential inflationary expansion, and "normal" regions like ours constantly being formed. The cosmological and particle physics parameters, such as the dark energy density or elementary particle masses, may have different values in different parts of such an eternally inflating universe. These variable parameters cannot be predicted with certainty, and one can only hope to determine their probability distributions. The proposed research will focus on the conceptual and technical problems that have been encountered in the calculation of probabilities in the eternally inflating universe. We shall also consider applications of the general theory to specific observables, such as the dark energy and dark matter densities, the magnitude of density fluctuations that seeded the structure formation in the universe, and the neutrino masses.
Technical Abstract
String theory appears to admit a multitude of vacua with different values of the effective constants of nature. In combination with inflationary dynamics, this results in a ?Multiverse? where the entire landscape of vacua is explored. How are the different vacua distributed in the Multiverse? And what are the probabilities for us to observe given values of the constants? These fundamental questions are the target of the present proposal.
The characterization of the distribution of vacua faces conceptual and technical difficulties. The volume of all types of regions in the inflationary multiverse is infinite, and a regularization prescription is needed for determining volume fractions in different vacua. Recently, we proposed a regularization, which is independent of gauge and of initial conditions. The uniqueness of this proposal should be investigated further. Moreover, new analytical and numerical tools should be developed to describe the complicated dynamics of eternal inflation. The calculation of probabilities for observations requires also the investigation of selection effects, and the comparison of ?alternate universes? with different low energy constants. We will also consider application to specific observables, such as the amplitude of density perturbations, the dark matter mass per photon, neutrino masses, and the cosmological constant.
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.