May 20th 2025, @UCM

Faculty of Physics. Plaza de las Ciencias 1. Madrid

Theoretical Physics Dept. (Seminar Room, 2nd floor)

11:00h

Speaker: Eduardo Martín-Martínez (University of Waterloo, Canada)

Title: Species Cosmology

Abstract: We will discuss the measurement problem in quantum field theoretical scenarios from the perspective of particle detector models. In particular, we will discuss the subtle problems and limitations of these models, and more generally, to what extent making localized measurements on a quantum field can be made compatible with a fully relativistic theory. Finally we will show how particle detector models (such as the Unruh-Dewitt detector) emerge from approximations on a fully relativistic model of localized measurements in QFT. We will discuss how the lessons learned in these discussions can have consequences on experimental setups involving quantum effects and gravity.

12:30h

Speaker: José de Ramón (University of Burgos, Spain)

Title: Covariant nonperturbative pointer variables for quantum fields

Abstract: In this talk I will discuss how modelling local, nonperturbative measurements in relativistic field theories has traditionally led to a choice between mathematical intractability and frictions with covariance and causality. In this context I will argue that there is a class of detector models in which nonperturbative, local and covariant, as well as mathematically tractable results can be achieved. Our approach combines several features of other models encountered in the literature of relativistic quantum information, namely scattering processes, quantum Brownian motion models, and Gaussian dynamics. I will argue that,  in order to model nontrivial, yet simple processes respecting causality and covariance, pointlike, ill-defined interactions are necessary, but these can be renormalized consistently a la Epstein Glasser. I will further analyze the model in the context of quantum measurement theory and argue that these models generate well-defined induced observables. Our formalism can be used to detect non-Gaussianities present in the field's state in a local and covariant way, and the nonperturbative nature of the problem provides an operational framework to discuss Bell inequalities in quantum field theory. Based on arXiv:2502.01283.