# Bianca Dittrich

### Teaching Affiliations

### Research Interests

Understanding the nature of space and time has been a central question for philosophy and physics throughout the centuries. Space time in its classical form underlies the formulations of quantum (field) theory as well as classical gravity. Yet we know today that both theories are incomplete and that classical space time should be replaced by quantum spacetime. With my research I am contributing towards the construction of a consistent theory of quantum gravity and towards an understanding of quantum space time. My work focusses in particular on non-perturbative approaches of quantum gravity and here on how to obtain a theory of quantum gravity valid over all scales. Such a theory of quantum gravity needs to incorporate renormalization concepts in its very construction. Thus my work involves the understanding of renormalization in a background independent context and with it the development of a framework of how to consistently formulate and construct a theory of quantum gravity. Arguable quantum gravity should be based on a Lorentzian (that is real time) path integral. Most path integrals evaluation techniques rely however on an Euclidianization (that is imaginary time). I am developing techniques to evaluate Lorentzian path integrals in quantum gravity, and explore some foundational questions related to the Lorentzian path integral. This includes the investigation of causality properties and topology change in quantum gravity. A partial list of subjects I am interested in: Loop quantum gravity and spin foams. Discrete geometries and diffeomorphism symmetry. Renormalization in background independent theories and tensor network coarse graining. Renormalization and tensor network techniques in lattice gauge theories. New notions of quantum geometry derived from topological field theories. Topological phases and defects. Holographic formulations of quantum gravity. Observables in covariant systems and general relativity. The Lorentzian path integral in quantum gravity. Causality properties in quantum gravity.

### Positions Held

- Junior Research Faculty, Perimeter Institute for Theoretical Physics, 2012-2017
- Adjunct Professor, University of Waterloo, 2012-present
- Adjunct Professor, University of Guelph, 2011-2014
- Max Planck Research Group Leader, Max Planck Institute for Gravitational Physics, Potsdam, 2009-2012
- Marie Curie Fellow, Universiteit Utrecht, 2008-2009
- Postdoctoral Researcher, Perimeter Institute for Theoretical Physics, 2005-2008
- Resident PhD Student, Perimeter Institute for Theoretical Physics, 2003-2004
- PhD fellow, Max Planck Institute for Gravitational Physics, Potsdam, 2002-2005

### Awards

- CAP-CRM Prize, Canadian Association of Physicists and Centre de recherches mathematiques, 2024
- FQXi Grant, Fetzer Franklin Fund, 2021-2022
- Computational Resources Grant, Compute Canada, 2021-2022
- Computational Resources Grant, Compute Canada, 2020-2021
- Simons Emmy Noether Fellows Program Grant, Simons Foundation, 2018-2026
- Discovery Grant, Natural Sciences and Engineering Research Council of Canada (NSERC), 2017-2023
- Early Researcher Award, Province of Ontario, 2014
- Otto Hahn Medal for Young Scientists, Max Planck Society, 2007

### Recent Publications

- Asante, S. K., Dittrich, B., & Padua-Argüelles, J. (2023). Complex actions and causality violations: applications to Lorentzian quantum cosmology. Classical and Quantum Gravity, 40(10), 105005. doi:10.1088/1361-6382/accc01
- Borissova, J. N., & Dittrich, B. (2023). Towards effective actions for the continuum limit of spin foams. Classical and Quantum Gravity, 40(10), 105006. doi:10.1088/1361-6382/accbfb
- Dittrich, B., & Kogios, A. (2023). From spin foams to area metric dynamics to gravitons. Classical and Quantum Gravity, 40(9), 095011. doi:10.1088/1361-6382/acc5d9
- Borissova, J. N., & Dittrich, B. (2023). Lorentzian quantum gravity via Pachner moves: one-loop evaluation. doi:10.48550/arxiv.2303.07367
- Asante, S. K., Dittrich, B., & Steinhaus, S. (2022). Spin foams, Refinement limit and Renormalization. doi:10.48550/arxiv.2211.09578
- de Boer, J., Dittrich, B., Eichhorn, A., Giddings, S. B., Gielen, S., Liberati, S., . . . Verlinde, H. (2022). Frontiers of Quantum Gravity: shared challenges, converging directions. doi:10.48550/arxiv.2207.10618
- Asante, S. K., & Dittrich, B. (n.d.). Perfect discretizations as a gateway to one-loop partition functions for 4D gravity. Journal of High Energy Physics, 2022(5), 172. doi:10.1007/jhep05(2022)172
- Dittrich, B., Gielen, S., & Schander, S. (2022). Lorentzian quantum cosmology goes simplicial. Classical and Quantum Gravity, 39(3), 035012. doi:10.1088/1361-6382/ac42ad
- Asante, S. K., Dittrich, B., & Padua-Argüelles, J. (2021). Effective spin foam models for Lorentzian quantum gravity. Classical and Quantum Gravity, 38(19), 195002. doi:10.1088/1361-6382/ac1b44
- Bahr, B., Dittrich, B., & Geiller, M. (2021). A new realization of quantum geometry. Classical and Quantum Gravity, 38(14), 145021. doi:10.1088/1361-6382/abfed1
- Asante, S. K., Dittrich, B., & Haggard, H. M. (2021). Discrete gravity dynamics from effective spin foams. Classical and Quantum Gravity, 38(14), 145023. doi:10.1088/1361-6382/ac011b
- Dittrich, B. (2021). Modified Graviton Dynamics From Spin Foams: The Area Regge Action. arxiv:2105.10808v1
- Dittrich, B., Jacobson, T., & Padua-Argüelles, J. (2024). de Sitter horizon entropy from a simplicial Lorentzian path integral. Physical Review D, 110(4), 046006. doi:10.1103/physrevd.110.046006
- Dittrich, B. (n.d.). Modified graviton dynamics from spin foams: the area Regge action. The European Physical Journal Plus, 139(7), 651. doi:10.1140/epjp/s13360-024-05432-4
- Borissova, J., Dittrich, B., Qu, D., & Schiffer, M. (2024). Spikes and spines in 4D Lorentzian simplicial quantum gravity. arxiv:2407.13601v1
- Dittrich, B., & Padua-Argüelles, J. (n.d.). Lorentzian Quantum Cosmology from Effective Spin Foams. Universe, 10(7), 296. doi:10.3390/universe10070296
- Borissova, J., Dittrich, B., Qu, D., & Schiffer, M. (2024). Spikes and spines in 3D Lorentzian simplicial quantum gravity. arxiv:2406.19169v1
- Borissova, J. N., Dittrich, B., & Krasnov, K. (2024). Area-metric gravity revisited. Physical Review D, 109(12), 124035. doi:10.1103/physrevd.109.124035
- Dittrich, B., & Padua-Argüelles, J. (2024). Twisted geometries are area-metric geometries. Physical Review D, 109(2), 026002. doi:10.1103/physrevd.109.026002
- Borissova, J. N., & Dittrich, B. (n.d.). Lorentzian quantum gravity via Pachner moves: one-loop evaluation. Journal of High Energy Physics, 2023(9), 69. doi:10.1007/jhep09(2023)069
- Asante, S. K., Dittrich, B., & Steinhaus, S. (2023). Spin Foams, Refinement Limit, and Renormalization. In Handbook of Quantum Gravity (pp. 1-37). Springer Nature. doi:10.1007/978-981-19-3079-9_106-1

### Seminars

- Area metric gravity as an effective continuum theory for spin foams, Quantum Gravity Program at Nordita, Nordic Institute for Theoretical Physics, Stockholm, Sweden, 2024/08/01
- Discussion: QFT framework for quantum gravity: yes or no, Quantum Gravity Program at Nordita, Nordic Institute for Theoretical Physics, Stockholm, Sweden, 2024/08/01
- Discussion: Unitarity, causality, stability, Quantum Gravity Program at Nordita, Nordic Institute for Theoretical Physics, Stockholm, Sweden, 2024/08/01
- Lectures: Regge calculus, effective spin foams and applications, Loops school 2024, Loops school 2024, 2024/05/01
- Plenary Talk: From Spacetime Quanta to Quantum Spacetime, CAP Congress 2024, CAP Congress 2024, 2024/05/01
- Quantum Gravity Seminar Series - TBA, Quantum Gravity, 2024/04/25, PIRSA:24040119
- Area metric gravity as effective theory for spin foams, London-Oldenburg Relativity Seminar, 2024/04/01
- From spacetime quanta to the quantum cosmos, Okinawa Institute of Science and Technology, Onna Son, Japan, 2024/03/01
- Entanglement entropy in lattice gauge theory I & II, Okinawa Institute of Science and Technology, Onna Son, Japan, 2024/02/01
- The (simplicial) Lorentzian quantum gravity path integral, OIST, 2024/02/01
- On the continuum limit of spin foams, International Loop Quantum Gravity Seminar, 2023/11/01
- Open discussion with today's speakers (Dittrich, Heisenberg, Quevedo, Turok), Puzzles in the Quantum Gravity Landscape: viewpoints from different approaches, 2023/10/27, PIRSA:23100018
- The simplicial Lorentzian path integral and spin foams, Puzzles in the Quantum Gravity Landscape: viewpoints from different approaches, 2023/10/27, PIRSA:23100068
- Panel Discussion - Future Directions in QG (Dittrich, Gregory, Loll, Sakellariadou, Surya), Puzzles in the Quantum Gravity Landscape: viewpoints from different approaches, 2023/10/27, PIRSA:23100020
- Diffeomorphism symmetry in the discrete and perfect discretizations, Workshop on Lagrangian Multiform Theory and Pluri-Lagrangian Systems, BIRS Hangzhou, 2023/10/01
- Lectures: Quantum Gravity and Quantum Space Time, XIV School on Gravitation and Mathematical Physics of the Mexican Physical Society, XIV School on Gravitation and Mathematical Physics of the Mexican Physical Society, 2023/09/01
- Challenges for quantum gravity, Radboud University Nijmegen, Nijmegen, Netherlands, 2023/07/01
- Progress and challenges for the Lorentzian quantum gravity path integral, Friedrich Schiller University Jena, Jena, Germany, 2023/07/01
- Quantization of 3D gravity, Okinawa Institute of Science and Technology, Onna Son, Japan, 2023/02/01
- A universal mechanism for the emergence of gravitons from effective spin foams and lattice gravity, Henri Poincaré Institute, Paris, France, 2023/01/01
- CDT lessons for Regge gravity and spin foams, Radboud University Nijmegen, Nijmegen, Netherlands, 2023/01/01
- The continuum limit of spin foams - is it GR?, Online seminar series: Quantum Gravity and All of That, 2022/11/01, Video URL
- Progress and challenges for the Lorentzian quantum gravity path integral, Relativity seminar, University of Warsaw, 2022/11/01
- Progress and challenges for the Lorentzian quantum gravity path integral, OIST, 2022/10/01
- Effective spin foam models and effective actions for their continuum limit, Loops 2021+1, Lyon, 2022/07/01
- Areas as fundamental variables for gravity, Online workshop: Informational architecture of spacetime, OIST, 2022/05/01
- Complex action and causality violations in Lorentzian gravity, University of Mainz, 2022/01/01
- Exploring Lorentzian quantum gravity via effective spin foams, Particle-Cosmo Seminar, University of Heidelberg, 2021/12/01
- The future of spin foams, International Loop Quantum Gravity Seminar, 2021/12/01
- Complex Regge action and topology change in Lorentzian gravity, Radboud University, 2021/12/01