Philosophy of Physics
The Philosophy of Physics Group is hosted by University College Groningen. Our work is broadly focused on, but not limited to, understanding the nature of probability, causality, spacetime and symmetry. Currently, we are investigating two exciting research projects on the quantum measurement problem and explanations of the arrow of time. Our group also has close connections with the Faculty of Philosophy and the Faculty of Science and Engineering.
Two themes were are working on, corresponding to the two research projects above, are: Quantum foundations, quantization, and causality (Simon Friederich, Isa Kooiman, Mritunjay Tyagi) and Symmetries and the arrow of time (Sean Gryb, Simon Friederich).
Quantum foundations, quantization, and causality (Simon Friederich, Isa Kooiman, Mritunjay Tyagi).
As Simon Friederich explains in his video for University of the Netherlands, the empirical success of quantum theory is profoundly puzzling. Supported by Simon Friederich’s VIDI grant “Saving Reality with Exotic Causality” we try to develop a compelling account of quantum theory as describing a single objective reality using a reconsideration of quantization: the procedure of going from a classical to a quantum theory. In particular, we focus on coherent state quantization and the prospects for interpreting the Husimi function on phase space as a proper probability density. Quantum theory predicts correlations between distant events for which there is no obvious causal explanation. To account for this “non-locality”, any empirically viable approach may have to embrace some kind of “exotic” causality, for instance causation backwards in time. We are currently figuring out what this exotic causality must be like and whether it’s acceptable or problematic.
Symmetries and the arrow of time (Sean Gryb, Simon Friederich)
The problem of the arrow of time arises from the observation that almost all processes that we encounter in science and in our everyday lives are strikingly asymmetric in time, whereas the fundamental laws of our best scientific theories are essentially time-symmetric. A popular solution to this problem is to postulate a very special state for the early universe, introducing a radical asymmetry in time that seeds all others. This solution, however, presupposes a notion of “specialness” for states of the universe. Our work on this theme questions this notion on new grounds. In particular, we argue that it treats as distinct states that correspond to a simple rescaling of all the distances in the universe. We then venture to show that the most important time asymmetries we see in our universe can be explained if we adapt the notion of specialness of states to be compatible with the claim that the absolute size of the universe is of no empirical significance. This suggests a new kind of explanation of the arrow of time can be obtained by making the right “counting” of physical states. Sean Gryb’s previous work on this theme was supported by a PhD grant from the Young Academy Groningen (YAG).
Group members
Affiliate members
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Leah Henderson (Professor of Philosophy, RUG)
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Jan-Willem Romeijn (Professor of Philosophy of Science, RUG)
Project Showcases
Open Quantum Systems and the Causal Structure of Reality by Sean Gryb
Description of the project:
In physics, it is often useful to distinguish between "open" and "closed" systems. A closed system has little or no interaction with its environment, whereas an open system interacts continuously with its surroundings. For this reason, closed systems typically conserve energy, and their evolution over time remains stable. In contrast, open systems exchange energy with their environment through absorption or dissipation. This exchange strongly constrains how the system evolves over time. For example, while an isolated pendulum might swing indefinitely, air resistance gradually dissipates its energy until it comes to rest at its lowest point.
What is particularly interesting is that dissipative interactions in open systems have a clear direction in time: a pendulum spontaneously slows down due to friction, but it never speeds up on its own. But what if the system in question is the Universe itself? Surely the Universe must be a closed system, as there is no external environment for it to interact with. Surprisingly, however, cosmologists have found that the Universe behaves in ways characteristic of an open, not a closed, system: it has been cooling continuously since the Big Bang, light waves stretch as they travel across expanding space, and the smooth distribution of matter in the early Universe has clumped into complex galaxies, stars, and planets.
This project aims to understand how this open-system behavior arises. As part of an interdisciplinary team of 17 physicists and philosophers across 10 institutions, I will apply the physical and mathematical tools of open systems to reframe our understanding of cosmic expansion and cooling. Together, we seek to establish a new philosophical framework for how a self-contained Universe can resemble an open system, shedding light on the fundamental nature of time's direction.