June 2021

Abstract: I describe a recent proposal for a simultaneous completion of quantum mechanics and general relativity, called the causal theory of views (CTV). Among its postulates are that time, in the sense of causal relations amongst events, is fundamental, and that space is emergent-along with everything that depends on space, such as distances, derivatives, fields, locality, non-locality etc.   Also assumed real and fundamental are energy and momentum.  Each event than has a view of the rest of the universe, which is made  by the energy and momentum transferred to it by its causal precedents. To define dynamics we must introduce a measure of distance on the space of views.  The idea is that differences of views substitutes for spacial distances and derivatives. The potential energy is then postulated to be a measure of the total diversity of views in the universe, called the variety.   The kinetic energy is then related to the variety’s rate of change under causal evolution.   The dynamics is defined by a sum over causal histories, from which space and spacetime emerge at the semiclassical approximation.  N body nonrelativistic quantum mechanics is also derived, due to the variety reducing to Bohm’s quantum potential. Further steps are sketched. Based on papers: arXiv:1712.04799.  with Marina Cortes: arXiv:1307.6167,   arXiv:1407.0032, arXiv:1703.09696 , arXiv:1902.05082,
arXiv:1104.2822, arXiv:1506.02938,  arXiv:1205.3707

Abstract: Recent arguments purport to show that if quantum theory is universally applicable then there is no objective fact about the outcome of a quantum measurement in certain extended Wigner’s friend Gedankenexperimenten. This calls for an examination of the notions of fact and objectivity. If quantum theory is universally applicable then the facts about the physical world include a fact about each quantum measurement outcome. I will argue that these and other physical facts lack an ideal kind of objectivity but their more modest objectivity is all that science needs.

Abstract: The invention of quantum theory in the 1920s represented a paradigm shift in our approach to describing the natural world. The focus on the object as a primitive shifted to the observation as a primitive. At the time, the first applications of interest came with a classical description in the language of Hamiltonian evolution, canonical variables and states. Staying close to this particular language lead to the development of the quantum formalism of Hilbert spaces, operators, Schrödinger equation and Born rule. Somewhat unfortunately, this standard formulation has come to dominate our understanding of what quantum theory is. While it was successfully employed in describing the micro-structure of matter and its relevant interactions, describing the dynamics of spacetime itself is outside of its scope. With the present talk I want to promote the idea that quantum theory is much more general than this standard formulation. I aim to clarify the essence of the paradigm shift that lies at the heart of the transition from classical to quantum theory. On this basis I then review the derivation from first principles of a more fundamental formulation of quantum theory, the positive formalism, and the recovery of the standard formulation as a special case.