About Gustaf Ullman
My name is Gustaf Ullman. I am a physicist, teacher and independent researcher based in Sweden.
I have a master’s degree in theoretical physics and a doctorate in medical radiation physics. My doctoral research concerned image quality in diagnostic radiology, using computer simulations of imaging systems and mathematical model observers.
I spent approximately fifteen years in academic research, including work at Linköping University and Uppsala University. My research ranged from medical imaging and Monte Carlo simulation to single-cell analysis and mathematical modelling in molecular biology. I now teach physics and mathematics while continuing my research independently.
Current work in physics and philosophy
My current research, and much of the present focus of this blog, lies in the foundations and philosophy of physics. I am particularly interested in the relationship between perspective-dependent descriptions and the objective structures shared between them. This leads to questions concerning relativity, quantum theory, symmetry, scientific objectivity, consciousness and the limits of formal description.
I approach these questions from the standpoint of physics and mathematics, but also through philosophy. My current work is broadly relational and structural: instead of beginning with a view of reality from nowhere, it asks what can be preserved, compared and shared between different perspectives.
Observer Equivariance
A central theme of my current work is Observer Equivariance. Its guiding idea is that physical objectivity should not be understood as the absence of perspective. Rather, objectivity consists in what remains invariant—or can be coherently transported—under admissible changes of perspective.
An observer in this framework need not be a conscious person. It may be a reference frame, a coordinate system, a gauge, a representation, a local chart or an operational standpoint. The central question is:
What must be shared between different perspectives for us to speak of the same physical law?
The mathematical development of this idea draws on category theory, group theory, geometry, symmetry and formal verification in Lean. Alongside more accessible essays, I publish technical papers and computer-verified formalizations of parts of the framework.
About this blog
This blog contains essays in both English and Swedish. Some posts introduce physical and philosophical questions for a general audience, while others develop more technical arguments. I aim to distinguish established physics and mathematics from philosophical interpretation and exploratory speculation.
The blog is primarily concerned with physics and philosophy, particularly questions about consciousness, objectivity and the relations between perspectives. My interests also include art, music and other subjects, which may enter the discussion where they overlap with the blog’s central themes.
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