# Bianca Dittrich

Faculty Chair

Perimeter Institute for Theoretical Physics

Areas of research:

### Teaching Affiliations

If you are interested in pursuing a MSc degree, please apply to the Perimeter Scholars International (PSI) masters program. If you are interested in working with me as a PhD student, please submit an application directly to my department at the University of Waterloo and indicate that you would like to be supervised by me. Perimeter Institute is committed to diversity within its community and I welcome applications from underrepresented groups.

### 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

- 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

- Dittrich, B., & Padua-Argüelles, J. (2023). Lorentzian quantum cosmology from effective spin foams. arxiv:2306.06012v1
- 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. arxiv:2303.07367v2
- Dittrich, B., & Padua-Argüelles, J. (2023). Twisted geometries are area-metric geometries. arxiv:2302.11586v1
- Asante, S. K., Dittrich, B., & Steinhaus, S. (2022). Spin foams, Refinement limit and Renormalization. arxiv:2211.09578v1
- Boer, J. D., Dittrich, B., Eichhorn, A., Giddings, S. B., Gielen, S., Liberati, S., . . . Verlinde, H. (2022). Frontiers of Quantum Gravity: shared challenges, converging directions. arxiv:2207.10618v1
- 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). 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
- Asante, S. K., Dittrich, B., & Haggard, H. M. (n.d.). Effective Spin Foam Models for Four-Dimensional Quantum Gravity. Physical Review Letters, 125(23). doi:10.1103/physrevlett.125.231301
- Asante, S. K., Dittrich, B., Girelli, F., Riello, A., & Tsimiklis, P. (2020). Quantum geometry from higher gauge theory. Classical and Quantum Gravity, 37(20), 205001. doi:10.1088/1361-6382/aba589
- Cunningham, W. J., Dittrich, B., & Steinhaus, S. (n.d.). Tensor Network Renormalization with Fusion Charges—Applications to 3D Lattice Gauge Theory. Universe, 6(7), 97. doi:10.3390/universe6070097
- Borissova, J. N., & Dittrich, B. (n.d.). Lorentzian quantum gravity via Pachner moves: one-loop evaluation. Journal of High Energy Physics, 2023(9). 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 Singapore. doi:10.1007/978-981-19-3079-9_106-1

### Seminars

- 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
- Progress and challenges for the Lorentzian quantum gravity path integral, Friedrich Schiller University Jena, Jena, Germany, 2023/07/01
- Challenges for quantum gravity, Radboud University Nijmegen, Nijmegen, Netherlands, 2023/07/01
- 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
- Overcoming the anomaly in loop quantum gravity, Non-local QG seminar, Lyon, 2021/10/01
- Loop quantum gravity - a status report, Inaugural workshop of the International Society for Quantum Gravity, 2021/10/01
- Exploring Lorentzian quantum gravity via effective spin foams, Radboud University, 2021/09/01
- Space and Time in a Lorentzian path integral, Quantizing Time, 2021/06/15, PIRSA:21060095
- Modified graviton dynamics from spin foams: the Area Regge action, Centre de Physique Theorique Marseille, 2021/06/01
- Quantization of space time and its effective dynamics, Universidade Federal do Rio Grande do Norte, 2021/06/01
- Quantization of space time and its (effective) dynamics, University of Sheffield, 2021/04/01
- Welcome and Opening Remarks, Women at the Intersection of Mathematics and Theoretical Physics, 2021/02/22, PIRSA:21020026
- Towards Lorentzian quantum gravity via effective spin foams, Quantum Gravity, 2021/01/28, PIRSA:21010024