In this article I bring the recent philosophical literature on theoretical equivalence to bear on dualities in physics. Focusing on electromagnetic duality, which is a simple example of S-duality in string theory, I show that the duality fits naturally into at least one framework for assessing equivalence—that of categorical equivalence—but that it fails to meet a necessary condition for equivalence on that account. The reason is that the duality does not preserve “empirical content” in the required sense; instead, it takes models to models with “dual” empirical content. I conclude by discussing how one might react to this.

It has been suggested that we can tell whether two theories are equivalent by comparing the structure that they ascribe to the world. If two theories posit different structures, then they must be inequivalent. The aim of this article is to evaluate the extent to which this desideratum holds for the different standards of equivalence that are currently on the table.

The Cold Dark Matter model faces many controversies at small scales, as simulations fail to reproduce the observed properties of dark matter (DM) halos. Since rival DM models differ on their predictions about the structure of DM halos, understanding their mass distribution is crucial for determining the nature of DM. However, only numerical approaches to determining what a hypothesis implies for the mass distribution are possible. Hence, simulations are a crucial part of evaluating DM rival models, as is assessing their reliability. I argue that robustness analysis is not a sufficient criterion for the trustworthiness of cosmological simulations.

Astrophysics faces methodological challenges as a result of being a predominantly observation-based science without access to traditional experiments. In light of these challenges, astrophysicists frequently rely on computer simulations. Using collisional ring galaxies as a case study, I argue that computer simulations play three roles in reasoning in astrophysics: (1) hypothesis testing, (2) exploring possibility space, and (3) amplifying observations.

Computer simulations of the formation and evolution of large-scale structure in the universe are integral to the enterprise of modern cosmology. Establishing the reliability of these simulations has been extremely challenging, primarily because of epistemic opacity. In this setting, robustness analysis defined by requiring converging outputs from a diverse ensemble of simulations is insufficient to determine simulation validity. We propose an alternative path of structured code validation that applies eliminative reasoning to isolate and reduce possible sources of error, a potential path that is already being explored by some cosmologists.

Signature-based model-independent (SBMI) searches for new physics form an explorative component of High Energy Physics experiments that aims at avoiding biases toward beyond-the-standard-model theories. In order to maximize their chances of meeting their objectives, however, SBMI searches must be guided by theory about the target phenomena. They correspond to strategy-driven experiments as defined by Koray Karaca, in contrast to Friedrich Steinle’s conception of explorative experiments. A concept of type II safeness is proposed to explain how the objectives of the experiment introduce theory dependence in the search strategy. Empirical evidence obtained from Large Hadron Collider experiments can therefore not avoid dependence on theory.

Since the discovery of the Higgs boson in 2012, particle physicists have not found any statistically significant deviations from the Standard Model. This has led to a shift of emphasis from model testing to exploration and an increasing popularity of ‘model-independent’ experimental approaches. Our goal is to analyze this shift by focusing on particle and event signatures. A differentiated picture of experimentation emerges between the extremes of theory guidance and theory-free exploration. Using the example of the top quark, we distinguish four types of motivations for the study of physics processes.