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AGPhil: Arbeitsgruppe Philosophie der Physik

AGPhil 4: Quantum Gravity 3

AGPhil 4.3: Talk

Monday, March 18, 2024, 18:15–18:45, PTB SR AvHB

Growing Block in Causal Set Theory: Not Quite — •Marco Forgione — University of Milan

In this contribution, I shall explore the possibility of characterizing the emergence of time in causal set theory (CST) in terms of the growing block universe (GBU) metaphysics. I will show that although GBU seems to be the most intuitive time metaphysics for CST, it leaves us with a number of interpretation problems, independently of which dynamics we choose to favor for the theory -here I shall consider the Classical Sequential Growth and the Covariant model. Discrete general covariance of the CSG dynamics does not allow us to individuate a single history of the universe (defined by a causal history of different causal sets), thereby making the claim that "the past exists" at best problematic. In addition, because the evolution of the universe in CSG dynamics leads to an outward branching causal tree, it becomes impossible to determine a proper "line of becoming", thereby blurring the presentists' claim that only the present exists. Similarly, the covariant approach runs into the same, if not even more severe problems, since each configuration of the universe would amount to a set of possible causal sets, thereby making the individuation of a single configuration of the universe -and thus the physical interpretation of the theory- implausible.

Keywords: causal set theory; emergence of time; Presentism; growing block view