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Gauge symmetry and the arrow of time: How to count what counts

Gryb, Sean (2025) Gauge symmetry and the arrow of time: How to count what counts.

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Abstract

This thesis addresses two major problems in the philosophy of physics. The first is how to identify the minimal physical content of a theory; that is, what features of a theory are truly needed to make predictions, and what can be removed without changing its empirical consequences. The second is the problem of time's arrow: why time seems to have a direction, even though the fundamental laws of physics treat the past and future symmetrically.

I show that answering the first question leads to insights about the second. In particular, I argue that the overall size of the Universe is not used to make predictions in cosmology, and so should not count as part of the theory's minimal physical content. Describing the Universe without this feature leads to a striking result: the arrow of time becomes a local phenomenon. Observers like us who see a Universe full of matter clumped together to form structures like stars and planets are statistically much more likely to see increasing clumpiness into the future than into the past. This tendency helps explain our experience of time's direction.


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Item Type: Published Article or Volume
Creators:
CreatorsEmailORCID
Gryb, Seans.b.gryb@rug.nl0000-0002-0439-3548
Keywords: gauge, symmetry, arrow of time, past hypothesis, scale invariance, cosmology, gravitation, representation
Subjects: Specific Sciences > Physics > Cosmology
General Issues > Explanation
Specific Sciences > Probability/Statistics
Specific Sciences > Physics > Statistical Mechanics/Thermodynamics
Specific Sciences > Physics > Symmetries/Invariances
Depositing User: Dr Sean Gryb
Date Deposited: 23 Sep 2025 10:56
Last Modified: 23 Sep 2025 10:56
Item ID: 26696
Publisher: University of Groningen
Official URL: https://research.rug.nl/en/publications/gauge-symm...
DOI or Unique Handle: 10.33612/diss.1384838034
Subjects: Specific Sciences > Physics > Cosmology
General Issues > Explanation
Specific Sciences > Probability/Statistics
Specific Sciences > Physics > Statistical Mechanics/Thermodynamics
Specific Sciences > Physics > Symmetries/Invariances
Date: 11 September 2025
URI: https://philsci-archive.pitt.edu/id/eprint/26696

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