Steffen Gielen

Research Interests

I am working on the interplay between various non-perturbative approaches to quantum gravity, which often involve some form of discrete structures, and cosmological models which could relate to observation. In this context I have been recently involved in the formulation of a "group field cosmology" model which provides a mechanism for topology change and for the creation of inhomogeneities starting from homogeneous and isotropic loop quantum cosmology.

Another recent interest of mine has been the formulation of classical gravity as a Cartan geometry, which allows bringing `spontaneous' symmetry breaking into gravity. This could be used for a reformulation of Ashtekar variables where local Lorentz symmetry is broken to a rotational subgroup through local observers that specify a local notion of `time'. I am currently working on formulations of physics on `observer space' which include all such local observers simultaneously. In general relativity this space is just a direct product of spacetime with the space of unit timelike vectors at each point, but if proposals such as relative locality point in the right direction it could be a more general space. Observer space could also be helpful to understand Lorentz-violating theories from a new geometric angle.

Positions Held

• 2010 - 2011 Postdoctoral Fellow, Albert Einstein Institute, Potsdam, Germany
• 2007 - 2010 PhD student, Relativity and Gravitation group, DAMTP, Cambridge

Awards

• 2011 Vaclav Votruba Prize, Doppler Institute, Prague, Czech Republic
• 2007 Mayhew Prize, DAMTP, University of Cambridge

Recent Publications

• Linking Covariant and Canonical General Relativity via Local Observers, Steffen Gielen, Derek K. Wise, Gen. Rel. Grav. (2012), arxiv: 1206.0658
• Group field cosmology: a cosmological field theory of quantum geometry, Gianluca Calcagni, Steffen Gielen, Daniele Oriti, Class. Quantum Grav. 29 (2012) 105005, arxiv: 1201.4151
• Cosmology from Group Field Theory, Steffen Gielen, Daniele Oriti, Lorenzo Sindoni, arxiv: 1303.3576
• Comment on `Causality-violating Higgs singlets at the LHC', Steffen Gielen, arxiv: 1302.1711
• Contracted Lorentz Invariance for Gravity with a Preferred Foliation, Steffen Gielen, arxiv: 1301.1692
• Spontaneous breaking of Lorentz symmetry for canonical gravity, proceedings of "Relativity and Gravitation - 100 years after Einstein in Prague", arxiv: 1210.1787
• Lifting General Relativity to Observer Space, Steffen Gielen, Derek K. Wise, arxiv: 1210.0019

Seminars

• General relativity on observer space, Group Seminar, Institute for Quantum Gravity, Erlangen
• Spontaneous breaking of Lorentz symmetry for canonical gravity, at ``Relativity and Gravitation - 100 years after Einstein in Prague``, Prague
• Cartan geometry and spontaneous breaking of Lorentz symmetry in gravity, Riemann Center for Geometry and Physics, Hannover
• Spontaneous breaking of Lorentz symmetry for canonical gravity, German Physics Society (DPG) Spring Meeting Goettingen