Astrophysics

This course is part of the 2026 Undergraduate Summer School curriculum. This course will provide a short introduction to loop quantum cosmology.  After a brief overview of the physics and geometry underlying cosmology, we will explore how it is possible to obtain a quantum description of cosmology.  As a part of this, we will discuss conceptual questions underlying quantum cosmology including the problem of time and the lack of an external observer, and some possible resolutions.  Finally, we will see how loop quantum gravity motivates a particular quantization for cosmology that gives loop quantum cosmology.  In the last part of the course, we will study the physics predicted by loop quantum cosmology in the primordial universe.

This course is part of the 2026 Undergraduate Summer School curriculum. This course is an introduction to basic cosmology based on Einstein’s theory of gravity (general relativity), to the modern ΛCDM model of the universe and its limitations, and to dark energy. The last lecture is non-standard and explores a plausible alternative to dark energy based on alternative theories of gravity. You are encouraged to ask questions in class (and outside) at all times.

Field-level inference has recently emerged as a powerful alternative to traditional summary-statistic approaches in the analysis of cosmological data sets. This technique exploits the full information content of data from the cosmic microwave background, galaxy redshift surveys, and forthcoming multi-wavelength imaging campaigns, allowing us to extract considerably more information from cosmic surveys compared to traditional analysis methods focused on modeling two-point correlations. This workshop will convene cosmologists, statisticians, machine-learning practitioners, and high-performance-computing experts to accelerate progress on this rapidly evolving frontier. 

All sessions will be plenary to maximise cross-disciplinary dialogue, with ample time reserved for  structured discussion and collaborative problem-solving.

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Speakers

Adrian Bayer (Flatiron Institute / Princeton University)
Carolina Cuesta-Lazaro (Flatiron Institute)
Natali de Santi (Berkeley)
Adriaan Duivenvoorden (MPA Garching)
Fei Ge (Caltech)*
Yashar Hezaveh (Université de Montréal)
Mikhail Ivanov (MIT)
Jens Jasche (Stockholm University)
Azadeh Moradinezhad (CNRS - LAPTh)
Fabian Schmidt (MPA Garching)
Uros Seljak (University of California, Berkeley)
*Virtual Presenter

Scientific Organizers

Marco Bonici (University of Waterloo)
Neal Dalal (Perimeter Institute)
Beatriz Tucci (Stanford University)

Cosmology is at a crossroad. Are the rising observational tensions harbingers of doom for our beloved LCDM paradigm? Is the young field of gravitational wave astronomy about to revolutionize our understanding of black holes, and their cosmic dynamics? What is the best explanation of the early universe? What are the most exciting new ideas? This annual workshop brings together leaders from our three institutes and beyond to address these questions, and plan a roadmap to advance the cosmological frontiers of fundamental physics.

Past editions:
2025 - hosted by APC
2024 - hosted by University of Edinburgh

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Speakers

Asimina Arvanitaki (Perimeter Institute)
Job Feldbrugge (University of Edinburgh)
Ben Freivogel (University of Amsterdam)
Akshay Anant Ghalsasi (Harvard University)
Yonatan Kahn (University of Toronto)
Alex Krolewski (University of Waterloo)
Alessandro Longo (APC)
Sizheng Ma (Perimeter Institute)
Roberto Maiolino (Cambridge University)
Laurence Perreault-Levasseur (Université de Montréal)
Rashmish Mishra (Harvard University)
Mykhaylo Usatyuk (University of California, Santa Barbara)
Cumrun Vafa (Harvard University)
Zach Weiner (Perimeter Institute)
Yazaman Yazdi (Dublin Institute for Advanced Studies)
Hanyu Zhang (University of Waterloo)

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Scientific Organizer Committee

Niayesh Afshordi
Ghazal Geshnizjani
Neal Dalal
Will Percival
Carlos Wagner

Elias Kritsis
Luca Santoni
Francesco Nitti
Martin Bucher

Latham Boyle
Alkistis Pourtsidou 

This course introduces Scientific Machine Learning, beginning with an overview of traditional and modern machine learning methods illustrated with examples from physics. It then transitions to physics-informed approaches, where physical laws, symmetries, and mechanistic models are embedded into learning frameworks. Tutorials and assignments will emphasize developing programming skills in Python.

This course in Cosmology provides a theoretical overview of the standard cosmological model. Key topics include the FRW metric and the homogeneous universe, the thermal history of the universe, inflation and scalar field dynamics, along with selected aspects of cosmological perturbation theory time permitting.

We will study advanced topics in gravitational physics and their applications to high energy physics. After reviewing topics in differential geometry, including differential forms, Cartan's formalism, and the Gauss-Codazzi equations for the geometry of embedded hypersurfaces, we will address the Einstein-Hilbert variational principle and the Hawking-York term, which plays an important role in the gravitational path integral. We will then study the Kerr solution for rotating black holes, and address topics in black hole thermodynamics using the Euclidean action, as well as Hawking radiation. Time allowing we will touch on some more advanced topics such as domain walls, brane world scenarios, Kaluza-Klein (KK) theory & KK black holes, Gregory-Laflamme instability, and Gravitational instantons.

This course offers an introduction to general relativity (GR), focusing on the core principles of Einstein's theory of gravity. We will explore key topics such as the equivalence principle, some essential concepts in differential geometry, the Einstein-Hilbert action, and Einstein's field equations. Furthermore, we will examine practical applications of general relativity in understanding black holes, cosmology, and gravitational waves.

Charting the Future Symposium: Big questions in particle physics, strong gravity, and cosmology over the next 25 years

Join us for a special symposium celebrating Perimeter’s 25th anniversary. This event offers a unique opportunity to unite Perimeter alumni and friends in the fields of cosmology, particle physics, and strong gravity with our extended community, reflect on a quarter-century of discovery, and look ahead to the challenges and opportunities that will shape the next 25 years of fundamental physics.

Over the past quarter-century, we have witnessed transformative advances across our fields. In particle physics, the discovery of the Higgs boson crowned decades of effort, while precision experiments continue to probe the Standard Model and search for new physics. In strong gravity, the direct detection of gravitational waves has opened a new observational window onto black holes, neutron stars, and the very fabric of spacetime. In cosmology, precision measurements of the cosmic microwave background and large-scale structure have revolutionized our understanding of the universe’s origins and evolution, even as dark matter and dark energy remain profound mysteries.

As we look to the future, a new generation of experiments, observations, and theoretical ideas promises to drive further revolutions. From uncovering physics beyond the Standard Model to probing the nature of spacetime and the earliest moments of the cosmos, the next 25 years are poised to be as transformative as the last.

This symposium will bring together leading researchers, young scientists, alumni, and friends to celebrate past achievements, and imagine the discoveries yet to come. We invite you to be part of this landmark event at Perimeter Institute, as we honor the spirit of curiosity, ambition, and collaboration that has defined our journey so far — and will carry us forward.

 

Invited Speakers

• Haipeng An (Tsinghua University)
• Masha Baryakhtar (University of Washington)
• Brian Batell (University of Pittsburgh)
• Laura Bernard (Observatoire de Paris)
• Richard Bond (CITA)
• Pablo Bosch Gomez (Utrecht University)
• Latham Boyle (University of Edinburgh)
• Patrick Brady (University of Wisconsin-Milwaukee)
• Joe Bramante (Queen's University)
• Savas Dimopoulos (Perimeter Institute)
• Adrienne Erickcek (University of North Carolina at Chapel Hill)
• Stefania Gori (UC Santa Cruz)
• Chad Hanna (Pennsylvania State)
• Renée Hložek (University of Toronto)
• Yoni Kahn (University of Toronto)
• Vicky Kaspi (McGill University)
• Gordan Krnjaic (Fermilab)
• Ian Low (Northwestern University)
• Mathew Madhavacheril (University of Pennsylvania)
• David Morissey (TRIUMF)
• Moritz Münchmeyer (University of Wisconsin-Madison)
• Ue-Li Pen (CITA, Perimeter Institute)
• Will Percival (Perimeter Institute)
• Maxim Pospelov (University of Minnesota)
• Josef Pradler (Austrian Academy of Sciences)
• Daniel Siegel (University of Greifswald)
• Nils Siemonsen (Princeton University)
• Carlos Wagner (University of Chicago)
• Huan Yang (Tsinghua University)
• Matias Zaldarriaga (IAS)

 

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Organizing Committee
Asimina Arvanitaki
Luis Lehner
Sergey Sibiryakov
Kendrick Smith

 

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This course in Cosmology provides a theoretical overview of the standard cosmological model. Key topics include the FRW metric and the homogeneous universe, the thermal history of the universe (with an emphasis on the hot Big Bang and equilibrium thermodynamics), inflation and scalar field dynamics, along with selected aspects of cosmological perturbation theory (time permitting). Instructor: Neal Dalal/Ghazal Geshnizjani Students who are not part of the PSI MSc program should review enrollment and course format information here: https://perimeterinstitute.ca/graduate-courses

The main objective of this course is to discuss some advanced topics in gravitational physics and its applications to high energy physics. Necessary mathematical tools will be introduced on the way. Instructor: Ruth Gregory/Aldo Riello Students who are not part of the PSI MSc program should review enrollment and course format information here: https://perimeterinstitute.ca/graduate-courses