On Mon, Feb 24, 2025 at 6:07 PM Brent Meeker <meekerbr...@gmail.com> wrote:
> *>> Zurek’s "envariance" means that if a system is entangled with its >> environment then mathematics insists we assign equal probabilities to >> outcomes in which the amplitudes in the quantum state’s expansion are >> equal, and obviously the squared magnitudes of the amplitudes. And I don't >> need to tell you what that leads to.* > > > *> That's not "envariance". Envariance is Zurek's proposal for how the > preferred basis problem should be solved. I guess I did need to tell you > that.* > *I**asked Grok3 (which might be the smartest AI currently available to the general public) about that and he she or it seems to agree with me. Envariance doesn't demand that many worlds be true but it is certainly consistent with it, and there are strong similarities between the two ideas. You were correct when you said because of envariance "interaction with the environment must select only certain bases which survive decoherence" but those "certain bases" that survive are all pointer states, quantum states that remains stable under environmental interactions, particularly during measurement processes; it's why the POINTER on the dial of a GR device always POINTS to spin up or spin down and nothing in between, and why you always see either a live cat or a dead cat and nothing in between. Pointer States are unusually robust quantum states, mathematically they are the interaction Hamiltonian between the system and its environment, and "you" is part of the environment.* *Here is my conversation with Grok3:* *Me: In quantum mechanics what does the word "envariance" mean?* *Grok3: "In quantum mechanics, "envariance" is short for "environment-induced variance," a concept introduced by physicist Wojciech Zurek as part of his work on quantum decoherence and the emergence of classical behavior from quantum systems. It describes a special kind of symmetry in how a quantum system becomes entangled with its environment, leading to the loss of certain quantum properties—like superposition—and the appearance of classical-like states."* *Me: How is that related to the Many Worlds idea?* *Grok3: "Envariance and the Many Worlds Interpretation (MWI) of quantum mechanics are connected in that they both deal with how quantum systems evolve and how we perceive outcomes, but they approach the story from different angles. Let’s break it down and tie them together intuitively."* *"In the Many Worlds idea, proposed by Hugh Everett, every quantum event—like a coin flip or a particle’s spin being measured—doesn’t just pick one outcome and discard the others. Instead, the universe splits into multiple branches, one for each possible result. So, if you measure a spinning coin, one "world" has you seeing heads, and another has you seeing tails. These worlds don’t talk to each other; they’re separate, parallel realities, and you’re only aware of the one you’re in. The superposition doesn’t collapse—it just fans out across these branches."* *"Envariance, on the other hand, doesn’t explicitly require splitting universes. It’s about how entanglement with the environment (like when you flip a coin) creates a symmetry that makes quantum superpositions unobservable to us. The coin’s heads-and-tails superposition gets tangled with the environment, and because of envariance, the information about the superposition is spread out in a way that locks us into seeing just one outcome locally—like heads—while the full quantum state still exists globally."* *"Here’s where they relate: in Many Worlds, the entanglement between the coin and the environment (and you, the observer) is what drives the branching. When the coin entangles with the table, and then you look at it, the quantum state of the whole system—coin + table + you—splits into branches: one where "you" see heads, and another where "you" see tails. Envariance fits into this picture as a mechanism explaining why each branch looks classical to the "you" inside it. The symmetry of envariance ensures that, within your branch, the environment has conspired to align with one definite outcome (say, heads), hiding the other possibilities (tails) in a way that’s consistent with the branching process. The tails outcome isn’t gone—it’s just in another world, perfectly mirrored by its own environment."* *"Intuitively, think of envariance as the backstage crew in a Many Worlds theater. While Many Worlds says the play splits into multiple performances (one for each ending), envariance is what makes each performance feel complete and consistent to its audience—ensuring that the props (environment) match the script (outcome) in every branch. Without envariance, the branching might feel more like a chaotic mess than distinct worlds. So, envariance doesn’t invent Many Worlds, but it helps make the worlds feel "real" and separate by describing how entanglement locks in the classical appearances we experience in each one."* *"They’re not identical—envariance can stand alone in decoherence theories without requiring Many Worlds—but in the MWI framework, envariance provides a neat way to understand why each world seems to have its own definite reality!"* *John K Clark See what's on my new list at Extropolis <https://groups.google.com/g/extropolis>* tbt > > -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. 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