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Cosmic Challenges in Fundamental Physics: Insights from String Theory

Join Diederik Roest at the "Quantum Universe" symposium as he explores the cosmic acceleration challenges within fundamental physics. Discussing the concordance model, he delves into components of our universe—including 73% dark energy and 23% dark matter—while outlining the inflationary period and its implications. He examines the role of string theory in addressing scalar potentials and moduli stabilization, presenting recent findings and future directions in cosmology, particularly how they relate to understanding the accelerated expansion of the universe.

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Cosmic Challenges in Fundamental Physics: Insights from String Theory

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  1. Cosmic challenges forfundamental physics Diederik Roest December 9, 2009 Symposium “The Quantum Universe”

  2. Modern cosmology

  3. Supernovae

  4. Cosmic Microwave Background

  5. Baryon acoustic oscillations

  6. Putting it all together

  7. Concordance Model Nearly flat Universe, 13.7 billion years old. Present ingredients: • 73% dark energy • 23% dark matter • 4% SM baryons

  8. Inflation • Period of accelerated expansion in very early universe • CMB anisotropies confirm inflation as source of fluctuations • Inflationary properties are now being measured • Planck satellite: • Non-Gaussianities? • Tensor modes? • Constraints on inflation? [cf. talk by Jan Pieter van der Schaar]

  9. Cosmic acceleration Two periods of accelerated expansion: • inflation in very early universe • present-time acceleration No microscopic understanding. Cosmic challenges for fundamental physics!

  10. Cosmic acceleration Modelled by scalar field with non-trivial scalar potential V Can we get such potentials from string theory? Extreme case with extremum of scalar potential leads to De Sitter space-time.

  11. Strings • Quantum gravity • No point particles, but small strings • Unique theory • Bonus: gauge forces Unification of four forces of Nature?

  12. …and then some! String theory has many implications: How can one extract 4D physics from this?

  13. Compactifications

  14. energy simple comp. with fluxes and branes Scalar field Stable compactifications • Simple compactifications yield massless scalar fields, so-called moduli, in 4D. • Would give rise to a new type of force, in addition to gravity and gauge forces. Has not been observed! • Need to give mass terms to these scalar fields (moduli stabilisation). • Extra ingredients of string theory, such as branes and fluxes, are crucial!

  15. Building a bridge What are the scalar potentials that follow from string theory, and do these allow for cosmologically interesting solutions? Focus of my VIDI project “How stable are extra dimensions?” (2008-2013). Keywords: flux compactifications, moduli stabilisation. Upcoming results: • Relations between N=2, 4 and 8 supergravity models with (un)stable dS vacua [1]? • Higher-dimensional origin in terms of gauge, geometric or non-geometric fluxes [2]? [1: D.R., Rosseel - in progress][2: D.R. ’09, Dibitetto, Linares, D.R. – in progress]

  16. Conclusions • Modern cosmology requires accelerated expansion for dark energy and inflation • Can we use string theory to explain this? • What are the scalar potentials from string compactifications? (flux compactifications and moduli stabilisation) • Many interesteresting (future) results – both theoretical and experimental

  17. Thanks for your attention! Diederik Roest December 9, 2009 Symposium “The Quantum Universe”

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