Astrid Eichhorn

Research Interests

My research focuses on quantum gravity.
I'm mostly working on asymptotically safe quantum gravity, which is a continuum QFT approach to quantum gravity within the path-integral framework. My interest lies in two aspects, namely, a better understanding of the quantum gravity theory, as well as a route towards a more realistic model, that includes matter degrees of freedom and could potentially lead to experimental detection of quantum gravity.
Recently, I have studied a unimodular version of asymptotic safety, and shown that it shows an interacting fixed point for the Newton coupling, and could therefore exist as a quantum theory. I have also examined the Faddeev-Popov ghost sector of asymptotic safety in more detail. Since the UV is strongly-interacting in this theory, the ghost sector is completely different from a perturbative setting in an asymptotically free theory.

Including matter degrees of freedom can have interesting consequences in asymptotic safety, since metric fluctuations can be shown to induce matter self-interactions. These could possibly allow to find experimental evidence for quantum gravity. One example is given by high-energy scattering processes, where asymptotically safe quantum gravity gives a distinct contribution to the scattering cross section.
Furthermore, matter-quantum gravity couplings can also be used to test, whether a particular model of quantum gravity is compatible with the observed low-energy properties of the Standard Model. As an example, the existence of light (compared to the Planck scale) fermions is a non-trivial requirement, since quantum gravity fluctuations could in principle break chiral symmetry and induce fermion masses of the order of the Planck scale.

I have also worked on the question of dimensional flow in different quantum gravity models, and studied how one can derive that the spectral dimension goes to 2 in the UV in different models, based on well-defined diffusion processes that probe the quantum spacetime

I'm also interested in QFTs in a non-perturbative regime, which can be investigated with the functional Renormalisation Group. Specifically, I'm working on questions concerning the low-energy properties of QCD, such as the deconfinement phase transition, or the condensation of gluons.
I also use the FRG approach to study other particle models, such as axion-photon interactions, to understand the Renormalization Group running of parameters in these models.

More recently, I've become interested in systems that have phase diagrams which are governed by competing order parameters, and can show multicritical points. The Functional Renormalization Group is very well-adapted to the study of such systems, which involve antiferromagnets in an external magnetic field, high-Tc superconductors, and a variety of other materials.

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The International Seminar on Asymptotic Safety:

If you're interested in the International Seminar on Asymptotic Safety (held via skype), please send me an email.
Details on the seminar, and slides of the previous talks can be found at Roberto Percacci's webpage.
FAQs on asymptotic safety can be found here.


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Experimental search for quantum gravity - the hard facts:

All talks from the "Experimental search for quantum gravity - the hard facts" conference (Oct. 2012) can be found in PIRSA.
The titles and abstracts of talks are also available at this location.

Recent Publications

• On unimodular quantum gravity, Astrid Eichhorn, Class. Quantum Grav. 30 (2013) 115016, arxiv: 1301.0879
• Renormalization Flow of Axion Electrodynamics, Astrid Eichhorn, Holger Gies and Dietrich Roscher, Phys.Rev. D86 (2012) 125014, arxiv: 1208.0014
• Quantum-gravity-induced matter self-interactions in the asymptotic-safety scenario, Astrid Eichhorn,Phys.Rev. D86 (2012) 105021, arxiv: 1204.0965
• Can we see quantum gravity? Photons in the asymptotic-safety scenario, Babette Döbrich, Astrid Eichhorn, JHEP 1206 (2012) 156, arxiv: 1203.6366
• Probing the quantum nature of spacetime by diffusion Gianluca Calcagni, Astrid Eichhorn, Frank Saueressig. arxiv: 1304.7247
• Faddeev-Popov ghosts in quantum gravity beyond perturbation theory, Astrid Eichhorn, arxiv: 1301.0632
• Experimentally testing asymptotically safe quantum gravity with photon-photon scattering. Proceedings of the 13th Marcel Grossmann Meeting, Stockholm. arxiv: 1210.1528

Seminars

• Probing the quantum nature of spacetime, Astrophysics Seminar, Nordita, Stockholm
• On unimodular quantum gravity, APS April meeting, Denver, CO
• Unimodularity, ghosts and matter in asymptotically safe quantum gravity, seminar at the University of Nijmegen
• A fixed point for unimodular quantum gravity, Quantum gravity workshop, University of Heidelberg
• Challenges for a UV completion of gravity, seminar at the University of Mainz
• Asymptotic safety - a quantum field theory of gravity, defense of the research training group "quantum and gravitational fields", University of Jena
• Matter in asymptotically safe quantum gravity, plenary talk at 6th ERG conference, Aussois, France
• Matter in asymptotically safe quantum gravity, 13th Marcel Grossmann Meeting, Stockholm
• Asymptotic safety - a quantum field theory of gravity and matter?, DESY theory seminar, Hamburg
• Matter in asymptotically safe quantum gravity, CAP congress, Calgary