Causal modelling frameworks link observable correlations to causal explanations, which is a crucial aspect of science. These models represent causal relationships through directed graphs, with vertices and edges denoting systems and transformations within a theory. Most studies focus on acyclic causal graphs, where well-defined probability rules and powerful graph-theoretic properties like the...
More than a century after the birth of quantum theory, the question of which properties and phenomena are fundamentally quantum remains under active investigation. In this talk, I will discuss when and to what extent quantumness can be unambiguously associated with an open quantum system that is sequentially measured at different times. Central to our analysis are the quantum regression...
The theory of relativity fundamentally reshaped our understanding of space and time, introducing conceptual shifts often illustrated explicitly through apparent paradoxes. Among these, the twin paradox stands out by clearly demonstrating how two observers following different spacetime trajectories can experience distinct elapsed times. Physically meaningful statements about elapsed time...
Considering the problems to extract near-term testable predictions from theories of quantum gravity, a promising alternative is to instead start with phenomenological approaches. One such phenomenon, that might be rather generic, is indefinite causal structure: The dynamic causal structure of general relativity gets combined with quantum indeterminism. The most established framework to...
We present a unified theoretical framework that combines a covariant Generalized Uncertainty Principle with a dynamical momentum‑space geometry. Using normal‑coordinate methods, we show that the extrinsic curvature of constant‑momentum hypersurfaces induces covariant deformations of the canonical commutators, yielding noncommutative position operators. Simultaneously, the momentum‑space metric...
Starting from operationally motivated principles, we derive a relational theory of local observables in Minkowski spacetime from which the notion of scalar quantum fields naturally emerges. We expand on quantum reference frames in spacetime and demonstrate that most properties of quantum fields arise as direct consequences of constraints on quantum reference frames -- that is, quantum fields...
The Page-Wootters framework introduces a covariant observable for a physical system, allowing it to serve as a time reference—a clock—to describe the dynamics of a system of interest. Within this framework, standard Schrödinger dynamics is recovered when the clock and system do not interact. However, interactions generally lead to time-nonlocal and potentially nonunitary dynamics. We show that...
Viewing frames of reference as physical systems, subject to the same laws as the systems they describe, is central to the relational approach in physics. Under the assumption that quantum mechanics universally governs all physical entities, this perspective naturally leads to the concept of quantum reference frames (QRFs). In this talk, I will discuss the perspective-dependence of position and...
One of the defining features of gauge theories is that they describe physics redundantly, in a way that is insensitive to certain local details. This redundancy is akin to how quantum error correcting codes (QECCs) protect quantum information from local errors by redundantly encoding logical states into a larger physical space. In this talk, I will show that this analogy is not merely a...
By describing the properties of one quantum system relative to another (treated as a quantum reference frame), we can construct a relational picture of physics that reduces or eliminates reliance on idealised background structures such as classical coordinates. When applied to time, this relational approach offers a compelling resolution of the "problem of time" in canonical approaches...
Causal set theory is an approach to quantum gravity that proposes that spacetime is fundamentally discrete and the causal relations among the discrete elements play a prominent role in the physics. Progress has been made in recognizing and understanding how some continuumlike features can emerge from causal sets at macroscopic scales, i.e., when the number of elements is large. An important...