Uploaded February 2026 | Updated September 2026, 2 weeks ago
Quantum Field Theory is a mature technology that is highly predictive. Most textbooks construct quantum field theory as an expansion for small positive coupling around classically stable vacua, which is a perfectly reasonable thing to do. However, history tells us that quantum mechanics sometimes does not conform to classical intuition. For instance, the hydrogen atom does not have a classically stable ground state, but is stable quantum mechanically. Similarly, negative coupling systems typically have upside-down potentials that do not possess a classically stable ground state. In this talk, I will give arguments why some negative coupling systems nevertheless are stable and physically acceptable quantum mechanically. In these theories, physical observables behave reasonably, with no indication of instabilities despite the missing classical intuition. I will point out the curious implications for our understanding of quantum field theory as well as for high energy physics observables that arise from treating negative coupling field theories as acceptable continuum descriptions of nature.
Quantum Field Theory is a mature technology that is highly predictive. Most textbooks construct quantum field theory as an expansion for small positive coupling around classically stable vacua, which is a perfectly reasonable thing to do. However, history tells us that quantum mechanics sometimes does not conform to classical intuition. For instance, the hydrogen atom does not have a classically stable ground state, but is stable quantum mechanically. Similarly, negative coupling systems typically have upside-down potentials that do not possess a classically stable ground state. In this talk, I will give arguments why some negative coupling systems nevertheless are stable and physically acceptable quantum mechanically. In these theories, physical observables behave reasonably, with no indication of instabilities despite the missing classical intuition. I will point out the curious implications for our understanding of quantum field theory as well as for high energy physics observables that arise from treating negative coupling field theories as acceptable continuum descriptions of nature.
