pcalau12i

I think a lot of proponents of objective collapse would pick a bone with that, haha, although it’s really just semantics. They are proposing extra dynamics that we don’t understand and can’t yet measure.

Any actual physicist would agree objective collapse has to modify the dynamics, because it’s unavoidable when you introduce an objective collapse model and actually look at the mathematics. No one in the physics community would debate GRW or the Diósi–Penrose model technically makes different predictions, however, and in fact the people who have proposed these models often view this as a positive thing since it makes it testable rather than just philosophy.

How the two theories would deviate would depend upon your specific objective collapse model, because they place thresholds in different locations. For GRW, it is based on a stochastic process that increases with probability over time, rather than a sharp threshold, but you still should see statistical deviations between its predictions and quantum mechanics if you can maintain a coherent quantum state for a large amount of time. The DP model has something to do with gravity, which I do not know enough to understand it, but I think the rough idea is if you have sufficient mass/energy in a particular locality it will cause a “collapse,” and so if you can conduct an experiment where that threshold of mass/energy is met, traditional quantum theory would predict the system could still be coherent whereas the DP model would reject that, and so you’d inherently end up with deviations in the predictions.

What’s the definition of interact here?

An interaction is a local event where two systems become correlated with one another as a result of the event.

“The physical process during which O measures the quantity q of the system S implies a physical interaction between O and S. In the process of this interaction, the state of O changes…A quantum description of the state of a system S exists only if some system O (considered as an observer) is actually ‘describing’ S, or, more precisely, has interacted with S…It is possible to compare different views, but the process of comparison is always a physical interaction, and all physical interactions are quantum mechanical in nature.”

The term “observer” is used very broadly in RQM and can apply to even a single particle. It is whatever physical system you are choosing as the basis of a coordinate system to describe other systems in relation to.

Does it have an arbitrary cutoff like in objective collapse?

It has a cutoff but not an arbitrary cutoff. The cutoff is in relation to whatever system participates in an interaction. If you have a system in a superposition of states, and you interact with it, then from your perspective, it is cutoff, because the system now has definite, real values in relation to you. But it does not necessarily have definite, real values in relation to some other isolated system that didn’t interact at all.

You can make a non-separable state as big as you want.

Only in relation to things not participating in the interaction. The moment something enters into participation, the states become separable. Two entangled particles are nonseparable up until you interact with them. Although, even for the two entangled particles, from their “perspectives” on each other, they are separable. It is only nonseparable from the perspective of yourself who has not interacted with them yet. If you interact with them, an additional observer who has not interacted with you or the three particles yet may still describe all three of you in a nonseparble entangled state, up until they interact with it themselves.

This is also the first I’ve heard anything about time-symmetric interpretations. That sounds pretty fascinating. Does it not have experimenter “free will”, or do they sidestep the no-go theorems some other way?

It violates the “free will” assumption because there is no physical possibility of setting up an experiment where the measurement settings cannot potentially influence the system if you take both the time-forwards and time-reverse evolution seriously. We tend to think because we place the measurement device after the initial preparation and that causality only flows in a single time direction, then it’s possible for the initial preparation to affect the measurement device but impossible for the measurement device to affect the initial preparation. But this reasoning doesn’t hold if you drop the postulate of the arrow of time, because in the time-reverse, the measurement interaction is the first interaction in the causal chain and the initial preparation is the second.

Indeed, every single Bell test, if you look at its time-reverse, is unambiguously local and easy to explain classically, because all the final measurements are brought to a single locality, so in the time-reverse, all the information needed to explain the experiment begins in a single locality and evolves towards the initial preparation. Bell tests only appear nonlocal in the time-forwards evolution, and if you discount the time-reverse as having any sort of physical reality, it then forces you to conclude it must either be nonlocal or a real state for the particles independent of observation cannot exist. But if you drop the postulate of the arrow of time, this conclusion no longer follows, although you do end up with genuine retrocausality (as opposed to superdeterminism which only gives you pseudo-retrocausality), so it’s not like it gives you a classical system.

So saying we stick with objective collapse or multiple worlds, what I mean is, could you define a non-Lipschitz continuous potential well (for example) that leads to multiple solutions to a wave equation given the same boundary?

I don’t know, but that is a very interesting question. If you figure it out, I would be interested in the answer.

Many of the interpretations of quantum mechanics are nondeterministic.

1. Relational quantum mechanics interprets particles as taking on discrete states at random whenever they interact with another particle, but only in relation to what they interact with and not in relation to anything else. That means particles don’t have absolute properties, like, if you measure its spin to be +1/2, this is not an absolute property, but a property that exists only relative to you/your measuring device. Each interaction leads to particles taking on definite states randomly according to the statistics predicted by quantum theory, but only in relation to things participating in those interactions.

2. Time-symmetric interpretations explain violations of Bell inequalities through rejecting a fundamental arrow of time. Without it, there’s no reason to evolve the state vector in a single time-direction. It thus adopts the Two-State Vector Formalism which evolves it in both directions simultaneously. When you do this, you find it places enough constructs on the particles give you absolutely deterministic values called weak values, but these weak values are not what you directly measure. What you directly measure are the “strong” values. You can interpret it such that every time two particles interact, they take on “strong” values randomly according to a rule called the Aharonov-Bergmann-Lebowitz rule. This makes time-symmetric interpretations local realist but not local deterministic, as it can explain violations of Bell inequalities through local information stored in the particles, but that local information still only statistically determines what you observe.

3. Objective collapse models are not really interpretations but new models because they can’t universally reproduce the mathematics of quantum theory, but some serious physicists have explored them as possibilities and they are also fundamentally random. You assume that particles literally spread out as waves until some threshold is met then they collapse down randomly into classical particles. The reason this can’t reproduce the mathematics of quantum theory is because this implies quantum effects cannot be scaled beyond whatever that threshold is, but no such threshold exists in traditional quantum mechanics, so such a theory must necessarily deviate from its predictions at that threshold. However, it is very hard to scale quantum effects to large scales, so if you place the threshold high enough, you can’t practically distinguish it from traditional quantum mechanics.

That’s literally China’s policies. The problem is most westerners are lied to about China’s model and it is just painted it as if Deng Xiaoping was an uber capitalist lover and turned China into a free market economy and that was the end of history.

The reality is that Deng Xiaoping was a classical Marxist so he wanted China to follow the development path of classical Marxism (grasping the large, letting go of the small) and not the revision of Marxism by Stalin (nationalizing everything), because Marxian theory is about formulating a scientific theory of socioeconomic development, so if they want to develop as rapidly as possible they needed to adhere more closely to Marxian economics.

Deng also knew the people would revolt if the country remained poor for very long, so they should hyper-focus on economic development first-of-foremost at all costs for a short period of time. Such a hyper-focus on development he had foresight to predict would lead to a lot of problems: environmental degradation, rising wealth inequality, etc. So he argued that this should be a two-step development model. There would be an initial stage of rapid development, followed by a second stage of shifting to a model that has more of a focus on high quality development to tackle the problems of the previous stage once they’re a lot wealthier.

The first stage went from Deng Xiaoping to Jiang Zemin, and then they announced they were entering the second phase under Hu Jintao and this has carried onto the Xi Jinping administration. Western media decried Xi an “abandonment of Deng” because western media is just pure propaganda when in reality this was Deng’s vision. China has switched to a model that no longer prioritizes rapid growth but prioritizes high quality growth.

One of the policies for this period has been to tackle the wealth inequality that has arisen during the first period. They have done this through various methods but one major one is huge poverty alleviation initiatives which the wealthy have been required to fund. Tencent for example “donated” an amount worth 3/4th of its whole yearly profits to government poverty alleviation initiatives. China does tax the rich but they have a system of unofficial “taxation” as well where they discretely take over a company through a combination of party cells and becoming a major shareholder with the golden share system and then make that company “donate” its profits back to the state. As a result China’s wealth inequality has been gradually falling since 2010 and they’ve become the #1 funder of green energy initiatives in the entire world.

The reason you don’t see this in western countries is because they are capitalist. Most westerners have an mindset that laws work like magic spells, you can just write down on a piece of paper whatever economic system you want and this is like casting a spell to create that system as if by magic, and so if you just craft the language perfectly to get the perfect spell then you will create the perfect system.

The Chinese understand this is not how reality works, economic systems are real physical machines that continually transform nature into goods and services for human conception, and so whatever laws you write can only meaningfully be implemented in reality if there is a physical basis for them.

The physical basis for political power ultimately rests in production relations, that is to say, ownership and control over the means of production, and thus the ability to appropriate all wealth. The wealth appropriation in countries like the USA is entirely in the hands of the capitalist class, and so they use that immense wealth, and thus political power, to capture the state and subvert it to their own interests, and thus corrupt the state to favor those very same capital interests rather than to control them.

The Chinese understand that if you want the state to remain an independent force that is not captured by the wealth appropriators, then the state must have its own material foundations. That is to say, the state must directly control its own means of production, it must have its own basis in economic production as well, so it can act as an independent economic force and not wholly dependent upon the capitalists for its material existence.

Furthermore, its economic basis must be far larger and thus more economically powerful than any other capitalist. Even if it owns some basis, if that basis is too small it would still become subverted by capitalist oligarchs. The Chinese state directly owns and controls the majority of all its largest enterprises as well as has indirect control of the majority of the minority of those large enterprises it doesn’t directly control. This makes the state itself by far the largest producer of wealth in the whole country, producing 40% of the entire GDP, no singular other enterprise in China even comes close to that.

The absolute enormous control over production allows for the state to control non-state actors and not the other way around. In a capitalist country the non-state actors, these being the wealth bourgeois class who own the large enterprises, instead captures the state and controls it for its own interests and it does not genuinely act as an independent body with its own independent interests, but only as the accumulation of the average interests of the average capitalist.

No law you write that is unfriendly to capitalists under such a system will be sustainable, and often are entirely non-enforceable, because in capitalist societies there is no material basis for them. The US is a great example of this. It’s technically illegal to do insider trading, but everyone in US Congress openly does insider trading, openly talks about it, and the records of them getting rich from insider training is pretty openly public knowledge. But nobody ever gets arrested for it because the law is not enforceable because the material basis of US society is production relations that give control of the commanding heights of the economy to the capitalist class, and so the capitalists just buy off the state for their own interests and there is no meaningfully competing power dynamic against that in US society.