Why I see no interest in Causal Set Theory

People who wish to figure out the lessons of modern physics on the nature of physical reality, need to study what was actually discovered and verified, namely quantum field theory. Any attempt to review speculative theories of more fundamental physics which might give back the known physics in approximation, without having done that homework, is only misleading. In particular, the basic concepts of causal set theory are misleadingly simple, as their simple expression gives to naive readers the completely false impression of understanding something. The truth is, those basic concepts of causal set theory are so extremely different from those of established physics that no expert has any clue how it might be possible for the latter to effectively emerge from the former; and anyway, it is already clear that any solution to this problem would have to be still extremely more complicated than the already very complicated understanding of known physics itself, which such naive reader is already too lazy to learn. Until then, naive reading of the concepts of causal set theory simply gives a wrong view of physics, in contradiction with facts (pedagogically speaking). In conclusion, any presentation of causal set theory to non-experts in guise of theory of physics is complete delusion for all practical purposes, even if there is a tiny chance to someday find a link, but in a way which has no legitimate place outside expert discussion.

So you need to be careful about popularization of candidate unification theories. Some candidates can well be pure nonsense which do not happen to receive explicit criticism from scientists just because they are so ridiculous that there is simply no point or time to waste reviewing them. I experienced this long ago when reviewing Scale Relativity Theory.

Why attempts to explain the passage of time in such ways are misguided

Of two things one : either physicalism holds, or it doesn't.

If it does not hold then the passage of time can be real but fundamentally a feature of the non-physical reality of consciousness unrelated with any physical theory, so that any attempt to look for it in some speculative fundamental physics (given that it isn't much there in the ordinary physics, with its thermodynamics having a mere kind of emergent time arrow) is misguided.

On the other hand if physicalism holds then the conscious experience of time passage emerges from, and is in principle fully explainable by, the already well-established laws of physics and thermodynamics, making any search for some kind of time passage in some speculative candidate more fundamental physics, out of subject and conceptually unrelated with the conscious experience of time, making very odd the very idea of expecting a time passage there as if our conscious experience of time was any valid hint for it. The logical thread of this argument has been developed in an article by David Wallace, I mean essentially the same issue except only that the matter of the measurement problem and practical appearances, replaces the matter of time passage.

Trying to escape this dichotomy and go for something in between would seemingly lead to panpsychism, which is also full of troubles.

Does Causal Set Theory Account for Quantum Features?

The below is an answer from ChatGPT (skipping introduction)

Causal set theory itself does not directly dictate the specifics of quantum phenomena like superposition and entanglement, but it offers a framework within which quantum effects can emerge. Some features of quantum theory, like superposition and entanglement, might arise in causal set theory, but it would require additional structures or interpretations to fully explain them. Let’s break this down:

1. Superposition in Causal Set Theory:

Classical spacetime is modeled as a smooth, continuous manifold, but causal set theory suggests that spacetime has a discrete structure. The "events" in this set can potentially be in a "superposition" of causal relationships, similar to how particles can be in superpositions of states in quantum mechanics.

However, superposition in causal set theory is not fully developed in the same way as in standard quantum mechanics. Quantum superposition relies on the Hilbert space formalism, where a system can be in a linear combination of multiple states. In causal set theory, superposition would likely emerge from the way events are correlated in the discrete causal structure, but an explicit mechanism for this has not been fully worked out in the context of causal sets.

The discrete nature of causal sets might lead to quantum-like phenomena in certain limits, but the specific relationship to superposition is not trivially clear and would need a more detailed framework for quantum mechanics to be derived from causal set theory.

2. Entanglement in Causal Set Theory:

Quantum entanglement involves correlations between particles that persist regardless of distance, and it plays a key role in quantum information theory. In causal set theory, the discrete causal relationships between events might be able to account for certain types of non-local correlations, but again, this would depend on how the causal set is interpreted in terms of quantum theory.

One possibility is that entanglement could arise from the way causal relationships between events are structured in the causal set. If the theory could be extended to incorporate quantum states in a way that is compatible with the Bell-type experiments or quantum teleportation, it might explain the non-locality of entanglement.

There is no definitive proof yet that causal set theory can fully capture the quantum mechanical correlations that underlie entanglement, as the theory’s primary focus has been on the structure of spacetime rather than on the specifics of quantum mechanics.

3. Quantum Gravity and Causal Set Theory:

Causal set theory primarily serves as an approach to quantum gravity, attempting to combine the principles of quantum mechanics with general relativity. It replaces the continuous fabric of spacetime with a discrete causal structure, which may lead to a quantum version of spacetime.

Quantum gravity does not yet have a fully established formulation that accounts for all quantum phenomena. The hope is that causal set theory might naturally produce the correct behavior for quantum fields and their interactions, potentially including superposition and entanglement, once more detailed formulations of quantum dynamics are integrated with the causal set framework.

Spacetime discretization could influence how quantum fields behave, and thus it might eventually help explain quantum phenomena within a quantum-gravitational context.

Current Status and Challenges:

Causal set theory is still a developing framework, and many questions remain about how exactly quantum mechanics, particularly phenomena like superposition and entanglement, emerge from this causal structure.

While the theory has shown promise in addressing aspects of quantum gravity, such as avoiding infinities in the way spacetime behaves at very small scales (like the Planck scale), integrating it fully with quantum mechanics is an ongoing challenge.

The relation between quantum field theory and causal set theory remains speculative, and more work is needed to demonstrate that causal set theory can directly account for these quantum features.

Conclusion:

Causal set theory provides an intriguing approach to quantum gravity, but it does not yet offer a complete explanation for quantum features like superposition and entanglement in the same way that quantum mechanics does. These phenomena might emerge in the context of causal sets, but additional work is needed to fully develop the theory in a way that accounts for them. Causal set theory is still primarily concerned with building a quantum theory of spacetime, and it may eventually provide a foundation for understanding quantum phenomena, but this remains a topic of ongoing research.