Geometry for String Model Building

Lead Research Organisation: University of Oxford
Department Name: Oxford Physics

Abstract

The main purpose of the research proposal "The Particle Physics and Cosmology of Supersymmetry and String Theory" is to create a strong UK research effort exploring the mathematics and physics of string compactifications. The proposed work has strong interdisciplinary aspects and will feed into particle physics and cosmology. This is facilitated by a wider, international collaboration which involves Oxford University and Imperial College in the UK, Ludwig-Maximilian University/Max-Planck Institute Munich and University of Hamburg/Desy in Germany and the University of Pennsylvania and Princeton University in the US. Accordingly, this proposal to EPSRC is accompanied by related proposals to DFG in Germany and NSF in the US.

String theory is an area of research at the interface between physics and mathematics. It relates to and has indeed inspired cutting edge mathematics and at the same time it remains the most promising candidate for a unifying physics theory. Via string theory the study of geometry - covered by the mathematical areas of differential and algebraic geometry - is directly related to properties of physical theories, such as their particle content or their associated cosmological evolution. For example, in some constructions, the Euler number, roughly counting the number ``holes" in the geometry, also determines the number of families of fundamental particles in the associated physical theory. This link has led to a fruitful interaction between physics and mathematics, with advanced mathematical methods being applied to analyse string theory models on the one hand and physical insights inspiring new mathematical developments on the other hand.

The theme of the proposed international research is at the centre of this interdisciplinary area. Progress in string theory crucially relies on understanding how advanced mathematical methods can be applied in concrete string theory setting. It also requires further developing these methods as well as creating new mathematical structures. In pursuing these lines of investigation, the main goal of the proposed programme is to lay the groundwork for answering one of the main question in contemporary science: Is string theory indeed a viable unified theory of physics?

Planned Impact

Research in string theory, just as research in closely related fields of pure mathematics and in theoretical particle physics, can obviously not be linked to direct and immediate economic benefits. However, it is worth remembering that, historically, is has often taken decades for fundamental physics theories, such as electromagnetism, quantum mechanics or general relativity, to translate into direct benefits for society - yet modern life would be unthinkable without the technology based on these fundamental theories. Analogous remarks apply to major developments in pure mathematics. In short, there is convincing historical evidence that funding of mathematical physics and related areas is an extremely worth while long-term investment.

On a more immediate level, the quest for a fundamental theory of nature and its mathematical formulation is well embedded into the public consciousness and is considered one of the major cultural and intellectual issues of our time. The main goals of the proposed research programme are closely related to these fundamental questions.

Fundamental research in theoretical and mathematical physics is pursued by all developed countries and underpins a range of more applied subjects. No university can claim to be a leading research institution without substantial activities in the subject. Hence, the world-class status of many UK higher educational institutions - their success in attracting talent from across the world and their contribution to the UK economy - depends on support for such theoretical and fundamental sciences.

Publications

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Anderson L (2015) Hypercharge flux in heterotic compactifications in Physical Review D

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Ashmore A (2016) The exceptional generalised geometry of supersymmetric AdS flux backgrounds in Journal of High Energy Physics

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Ashmore A (2017) Exactly marginal deformations from exceptional generalised geometry in Journal of High Energy Physics

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Blesneag S (2018) Matter field Kähler metric in heterotic string theory from localisation in Journal of High Energy Physics

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Blesneag S (2016) Holomorphic Yukawa couplings in heterotic string theory in Journal of High Energy Physics

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Blesneag S (2017) Holomorphic Yukawa couplings for complete intersection Calabi-Yau manifolds in Journal of High Energy Physics

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Braun A (2017) Discrete Symmetries of Calabi-Yau Hypersurfaces in Toric Four-Folds in Communications in Mathematical Physics

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Braun A (2018) Heterotic line bundle models on elliptically fibered Calabi-Yau three-folds in Journal of High Energy Physics

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Braun A (2018) NS5-branes and line bundles in heterotic/F-theory duality in Physical Review D

 
Description Major progress has been made in developing techniques to work out Yukawa couplings from string theory. This is one of the most important issues in relating string theory to observable physics, yet has so far remained largely elusive. We have now shows that holomorphic Yukawa couplings can be computed explicitly, using methods of both differential and algebraic geometry for a wide range of compactification manifolds. These methods have been applied to a number of quasi-realistic examples. In particular, the moduli dependence of these couplings has been explicitly worked out in some cases. This is the first time that results of this kind have been obtained and it constitutes major progress in the attempt to understand observable physics from string theory. We have also, for the first time, calculated the matter field Kahler metric which is essential to obtain physical Yukawa couplings. In a parallel line of work, we have found that the number of standard models - that is models with the correct spectrum - within string theory is exponentially large.
Significant progress has also been made in characterising generic type II and M-theory superstring backgrounds preserving eight supercharges, in compactifications to both Minkowski and anti-de Sitter space, using the tools of exceptional generalised geometry. In particular, new steps were taken in identifying the moduli spaces in the case of AdS backgrounds.
Exploitation Route The next step is to apply our techniques to calculate physical Yukawa couplings for realistic string models. It will be crucial to explore to what extent this reduces the number of viable models and to identify at least one example which meets all phenomenological constraints.
Our generalised geometric techniques should extend to backgrounds with less supersymmetry and also potentially to heterotic backgrounds. This is something we aim to develop with particular focus on characterising the moduli and understanding the geometry of the corresponding moduli spaces.
Sectors Other