Origins of the Universe

 
The Origins of the Universe project is designed to advance our understanding of the universe by stimulating theoretical research into mechanisms of cosmogenesis.

The Simons Foundation’s effort will develop testable predictions about string theory, quantum gravity and inflation. To do so, the foundation has assembled an international group of theoretical physicists to tackle one of the biggest unsolved mysteries in science: what exactly went down at the dawn of the universe around 13.8 billion years ago.

Einstein’s gravity correctly describes astrophysical and cosmological phenomena at hugely diverse scales and is one of the most successful theories of all time. Yet experiment and observation have raised questions that might require theories beyond Einstein’s, including the cosmological constant problem, the lack of fundamental understanding of the accelerated expansion of the universe and the enigma of the beginning of the universe. The Cosmology Beyond Einstein’s Theory group will explore these issues.

The Research in Modern Inflationary Cosmology group will expand our understanding of inflationary dynamics, providing new insights into the density perturbations seeding structure in the universe as well as into the observational constraints on the theory. A key issue will be non-Gaussianity in the cosmic microwave background fluctuations. The group will develop the underlying theory, with control of quantum gravity effects, including typical string theoretic solutions with classical potential energies and many axion fields.

Cumrun Vafa will seek to find the universal features that distinguish the string landscape from the swampland by studying solutions to string equations. He is particularly interested in exploring consequences of these features that may lead to observable predictions for cosmology.

The inflationary paradigm — the proposal that our universe underwent an era of rapid acceleration — is the dominant paradigm for explaining many of the observed features of the early universe. However, this evidence also allows for alternatives, and so Kurt Hinterbichler’s project seeks to identify, discover, explore and develop possible alternatives to test against inflation. This includes studying and developing the structure of novel effective field theories that may be used in the construction of such scenarios.

Alberto Nicolis’s project involves a systematic application of effective field theory techniques and of spontaneous symmetry breaking considerations to early universe cosmology, with the goal of understanding the realm of possibilities beyond inflation that on the one hand are well motivated from the quantum field theory standpoint and, on the other hand, are compatible with observations. He will address model-independent questions related to the dynamics of the early universe and their implications for cosmological observables, starting from a quantum field theory, symmetry-based viewpoint, with an emphasis on the consequences of spontaneous symmetry breaking and the Goldstone phenomenon. Such an approach has proven extremely valuable in particle physics, and research in cosmology in the last decade has taught us that it can be extremely valuable there as well.

The New Theoretical Avenues for the Early Universe group, under Mark Trodden and Justin Khoury, will explore the range of allowed ideas for the early evolution of the cosmos and expand the theoretical and observational ways to distinguish between such possibilities. An important component is the development of new models of the very early universe that can address the traditional problems of standard big bang cosmology and generate density perturbations consistent with observations. A crucial broad question is that of identifying the symmetries that might underlie early universe cosmology and determining their observational consequences. This approach holds out the hope of model-independent tests for different early-universe scenarios. On a more specific level, new models frequently invoke physics that at least superficially conflict with standard stability criteria of general relativity. This group will explore this theoretical issue by sharpening the connection between the null-energy condition and the standard assumptions of quantum field theory.
 

Eva Silverstein is a physicist, cosmologist and string theorist. She is best known for her work on early universe cosmology, developing the structure of inflation and its range of signatures, as well as extensive contributions to string theory and gravitational physics. Her early work included control of tachyon condensation in string theory and resulting resolution of some space-time singularities (with Adams, Polchinski and others). Other significant research contributions include the construction of the first models of dark energy in string theory, some basic extensions of the AdS/CFT correspondence to more realistic field theories (with Kachru), as well as the discovery of a predictive, new mechanism for cosmic inflation involving D-brane dynamics (with Tong and Alishahiha), which helped motivate more systematic analyses of primordial non-Gaussianity.

Massimo Porrati is a professor of physics and a member of the Center for Cosmology and Particle Physics at New York University. His major research interests are string theory, supersymmetry and supergravity, nonperturbative aspects of strings and quantum field theory, and cosmology. Among others, Porrati is known for his work on the large-distance modification of gravity and its application to the cosmological constant problem. With Gia Dvali and Gregory Gabadadze, he co-pioneered and advanced this direction by proposing a generally covariant model of infrared modification of gravity (the so-called ‘DGP model’) and studying many novel and subtle features of this class of models.

Cumrun Vafa was appointed a full professor in the department of physics at Harvard University in 1990, where he is currently the Hollis Professor of Mathematicks and Natural Philosophy and a professor of physics. Vafa’s main area of research is string theory at the interface of geometry and physics. He is a member of the American Academy of Arts and Sciences and the National Academy of Sciences and has received many awards, including ICTP’s Dirac Medal, the AMS’s Leonard Eisenbud Prize for Math and Physics, the APS’s Dannie Heineman Prize in Mathematical Physics and the Breakthrough Prize in Fundamental Physics.

Kurt Hinterbichler is an assistant professor of theoretical physics at Case Western Reserve University and a member of the Center for Education and Research in Cosmology and Astroparticle Physics. He has a wide range of interests encompassing aspects of early universe cosmology, higher spins, extra dimensions/brane worlds, modified gravity and screening mechanisms. He is interested quite generally in the structure of effective field theories, the primary tool with which to attack problems when a full underlying theory is not known or is too difficult to solve. He has been active in constructing and studying effective theories that possess interesting and novel features and that may have relevance during the very early or late universe.

Alberto Nicolis works on cosmology, gravitational physics and quantum field theory. He has also applied effective field theory techniques and ideas to study the dynamics of different phases of matter, such as fluids, solids and superfluids, with an emphasis on the phenomenon of spontaneous symmetry breaking. His most important contributions to date include the so-called weak gravity conjecture, the realization that causality and analyticity can constrain the structure of low-energy effective field theories in nonobvious ways and the development of the galileon effective field theory.

Mark Trodden is a theoretical physicist who has worked broadly in both cosmology and particle physics, with the majority of his work lying on the border between these two areas. His early work was on the origin of the matter-antimatter asymmetry of the universe and on the microphysical properties of topological defect solutions to quantum field theories. In later significant work, he explored (with Krauss and Nasri) how models of neutrino masses can give rise to dark matter candidates and proposed (with Kaloper, March-Russell and Starkman) new compactification manifolds for large extra dimensions. He is best known for introducing (with Carroll, Duvvuri and Turner) one of the most-studied modified gravity approaches to late-time cosmic acceleration, as well as for the detailed development (with Goon, Hinterbichler and Joyce) of novel field theories with applications to both the early and present-day dynamics of the universe.

Justin Khoury is a theoretical physicist whose research interests lie at the interface of cosmology, particle physics and string theory. He is best known for developing and investigating new models of dark matter and dark energy, as well as novel cosmological theories of the very early universe. He introduced chameleon (with Weltman) and symmetron (with Hinterbichler) theories of dark energy, which have spurred considerable theoretical and experimental activity aimed at testing the signatures of these theories. He developed the conformal scenario (with Hinterbichler and others), an alternative to inflation based on approximate conformal invariance in the early universe. More recently, he proposed (with Berezhiani) a novel theory of dark matter superfluidity, inspired by recent developments in condensed matter physics. The theory aims to explain various empirical scaling relations in galaxies, while simultaneously preserving the success of the LambdaCDM model on cosmological scales.