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BusyBeaver(6) Is Quite Large

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Re: BusyBeaver(6) Is Quite Large

#91
post #62

Earlier quoted context omitted.

The number itself is not independent of ZFC. (Every integer can be expressed in ZFC.) What's independent of ZFC is the process of computing BB(748).

To try and help people digging into this, the following helped me. Two lenses for trying to understand this are potentially Chastain's limits on output of a lisp program being more complex than the program itself [1] or Markov's proof that you can't classify manifolds in d>= 4. If you try the latter and need/want to figure out how the Russian school is so different this is helpful [2] IMHO the former gives an intuiti…

Looking at [3], they seem to argue that the system isn’t complete for the usual Gödel reasons, which, sure, it isn’t, but then they call the claim that the system fails to decide, which is a statement about probability, a “scientific fact”. This seems to me like a mistake?

Like, a TOE is not expected to decide all statements expressible in the theory, only to predict particular future states from past states, with as much specificity as such past states actually determine the future states. It should not be expected to answer “given a physical setup where a Turing machine has been built, is there a time at which it halts?” but rather to answer “after N seconds, what state is the machine (as part of the physical system) in?” (for any particular choice of N).

Whether a particular statement expressed in the language of the theory is provable in the theory, is not a claim about the finite-time behavior of a physical system, unless your model of physics involves like, oracle machines or something like that.

Edit: it later says: “ Chaitin’s theorem states that there exists a constant K_{ℱ_{QG}} , determined by the axioms of ℱ_{QG} , such that no statement S with Kolmogorov complexity K(S) > K_{ℱ_{QG}} can be proven within ℱ_{QG} .”

But this, unless I’m badly misinterpreting it, seems very wrong? Most formal systems of interest have infinitely many distinct theorems. Given an infinite set of strings, there is no finite universal upper bound on the Kolmogorov complexity of the strings in that set.

Maybe this was just a typo or something?

They do then mention something about the Bekenstein bound, which I haven’t considered carefully yet but seems somewhat more promising than the parts of the article that preceded it.

Re: BusyBeaver(6) Is Quite Large

#92

If you want to learn about actual Busy Beaver results, I suggest reading https://www.sligocki.com/ instead Unlike Aaronson, he actually is on the forefront of Busy Beaver research, and is one of the people behind the https://bbchallenge.org website

I don’t get it. What’s wrong with the post? And https://arxiv.org/abs/1605.04343 is interesting, no?

Re: BusyBeaver(6) Is Quite Large

#93

Earlier quoted context omitted.

>Unlike Aaronson, he actually is on the forefront of Busy Beaver research [...] Extremely bad ad hominem , I enjoyed Aaronson's read, nothing wrong with it.

Gently, seconding peer: that is not ad hominem :) Colloquially, I understand it's easy to think it means "saying something about someone that could be interpreted negatively" because that's the context it is read in it when it is used. The meaning is saying a logical argument is incorrect because of who wrote the argument.

The wording implies that Aaronson does not know what he's talking about.

>If you want to learn about actual Busy Beaver results [...]

This is saying there is no discussion of the results in the article, which is not true.

>Unlike Aaronson, he actually is on the forefront of Busy Beaver research [...]

This implies Aaronson has no (or lesser) authority on the subject and suggests we should listen to somebody else who purportedly has more.

Nowhere in @NooneAtAll3's comment is there an argument made against/for the contents of the article, an example of that would be:

"Aaronson mentions X but this is not correct because Y" or something along those lines.

Instead, the comment, in it's full extent, is either discrediting (perhaps unintentionally) and/or appealing to the authority of people involved. That's ad hominem.

Re: BusyBeaver(6) Is Quite Large

#94
post #19

Earlier quoted context omitted.

No, that's one of the freakiest things about things like the Busy Beaver function. There is an exact integer that BB(748) defines. You can add one to it and then it would no longer be that number anymore. If you are refering to the idea that nothing that can't exist in the real universe "really exists", then the "Busy Beaver" portion of that idea is extraneous, as 100% of integers can't exist in the real universe, an…

> that's one of the freakiest things about things like the Busy Beaver function Every sentence ever spoken and every view ever looked at is also a number. It's not a freaky thing about "things like" busy beaver, it's a freaky thing about the concept of information. But even though everything is a number, saying "it's crazy that a number can be X" is usually someone making a mistake, using the everyday concept of numb…

> Every sentence ever spoken and every view ever looked at is also a number. It's not a freaky thing about "things like" busy beaver, it's a freaky thing about the concept of information.

I'd say that's a bit of a wrong or misleading statement. I think the correct version is "everything[1] can be encoded as a number". The concept of number is a very particular concept! It's pretty absurd to say "a screwdriver is a number" or "a word is a number". That is true for the peano axiomatization of numbers; but to me in particular, I believe numbers are a generalization (and formalization) of the idea or concept of quantity. There's a particular idea that refers to say 'two' apples, the quantity of apples. A word is not a quantity, it's a different concept. Even though each of them could be encoded as a number somehow!

[1]: Everything that we believe to be finite and of interest, that is. We don't know presently anything that could be used in reality (a music, picture, etc.) that can't in principle be encoded as a large enough number.

I think this is quite interesting, because this encoding is critical, and it completes the system. You essentially need a machine to turn things into numbers and numbers into things; and this is unavoidable. You can actually encode this machine itself with numbers! This number (which encodes this transcoding machine) can even be decoded by its own machine! But we cannot actually avoid the machine itself, some actual realization in the real world, because any number, in order to represent something, can only be translated by one "machine" (which can be essentially a computer, or a mind, etc.).

Instead of thinking of machines, you can also think of conventions. So you can have a convention that say the number '5' encodes the concept 'word', or maybe it simply encodes the string of letters "word" ("w"+"o"+"r"+"d"). But the convention interpretation isn't complete, because you still need someone, or something, to interpret this convention in practice and potentially turn concepts into reality, or simply manipulate those concepts in significant and useful ways.

Some more examples: (1) you can encode objects by describing a series of solid operations, essentially CAD modelling, so you have numbers that represent solids. The machine that interprets this number and is able to translate it for example into a picture, a series of instructions to be interpreted by a 3d printer, of performs operations (inferences) about the relevant solid model (for example, a structural analysis) is your "machine", i.e. your software, without which a number, or string of bits by itself doesn't mean anything (except the quantity associated with that binary number, perhaps), and again this encoding or number is essentially arbitrary, it could be very different. (2) a JPEG file for example encodes an image that is read by a software stack (jpeg decoder+picture viewer+operating system+display driver) and forwarded to your monitor to be viewed as a pixel array. Again the string of bits associated with any image could in principle represent anything else representable.

Information (Shannon information in particular) simply implies the encoding possible.

It's really interesting that a lot of the time we are performing essentially translations between different representations of a thing: a series of bits into states of pixels on a screen (a picture), [a series of bits] into a 3d printed object, into a visualization of an object on a screen, etc. (one way), or a reading of a camera sensor (photograph) into a series of bits, a conception of an object (3d modelling), a conception of a story (writing), etc. (the other way). We of course can (and must for them to be built of course) conceptualize those "machines" themselves (e.g. the software part), represent them in some way (our encoding), and then turn this representation into a realization of those machines (a software, a piece of hardware, or just a representation convention, etc.).

In other words, the mind or computer itself is always an integral part of the process, and information in a vacuum doesn't represent anything necessarily.

Finally, most of what we do is some kind of translation, inference, and construction -- everything to assist our lives. Of course some "machines" are capable of generating new concepts, those are very interesting "machines" :)

Re: BusyBeaver(6) Is Quite Large

#95
post #86

Earlier quoted context omitted.

This integer only exists if you assume classical logic. Otherwise, there is no such integer a priori, and actually there is none in general.

I'm fairly certain that's wrong, and I see a couple of other people may be making that mistake elsewhere in this conversation too. A Turing Machine is a Turing Machine. The execution trace of a Turing Machine is fully determined by its ruleset and its initial input. It doesn't matter which axioms you "take", nor does it matter what the intent of the initial construction of the 748-state machine was, or indeed even if…

> There is no situation where "the next step" of the Turing Machine "depends on your axioms" and could thereby be affected by such a decision.

That's easy, you just have to be an ultrafinitist, and say, "The definition of a TM presupposes an infinite set of natural numbers for time steps and tape configurations. But there aren't actually infinitely many natural numbers, infinitely long executions, arbitrarily long proofs, etc., outside of the formalism. If a formal statement and its negation do not differ regarding any natural numbers small enough to actually exist (in whatever sense), then neither is more true than the other." In particular, consistency statements may have no definite truth value, if the hypothetical proof of an inconsistency would be too large.

Of course, metamathematics tells us "you can't do that, in principle you could tell the lie if you wrote out the whole proof!" But that principle also presupposes the existence of arbitrarily-long proofs.

(Personally, hearing some of the arguments people make about BB numbers, I've become attracted to agnosticism toward ultrafinitist ideas.)

Re: BusyBeaver(6) Is Quite Large

#96
post #79

People on the bbchallenge Discord server are keen to speculate on how many Turing Machine states are needed to surpass Graham's Number, which is vastly larger than the 2^^2^^2^^9 achieved by the latest BB(6) champion. We know from the functional busy beaver [1] that Graham behaviour can come surprisingly early; a 49-bit lambda term suffices. There are only 77519927606 closed lambda terms of at most that size [2], com…

I can't pretend to be an expert, but I'll argue BB(7) is probably larger than Graham's number.

BB has to grow faster than any computable sequence. What exactly that means concretely for BB(7) is... nothing other than handwaving... but it sort of means it needs to walk up the "operator strength" ladder very quickly... it eventually needs to grow faster than any computable operator we define (including, for example, up-arrow^n, and up-arrow^f(n) for any computable f).

My gut feeling is that the growth between 47 million and 2^^2^^2^^9 is qualitatively larger than the growth between 2^^2^^2^^9 and graham's number in terms of how strong the operator we need is (with gramah's number being g_64 and g here being roughly one step "above" up_arrow^n). So probably we should have BB(7)>Graham's number.

Re: BusyBeaver(6) Is Quite Large

#97
post #4

It boggles my mind that a number (an uncomputable number, granted) like BB(748) can be "independent of ZFC". It feels like a category error or something.

It boggles my mind that we ever thought a small amount of text that fits comfortably on a napkin (the axioms of ZFC) would ever be “good enough” to capture the arithmetic truths or approximate those aspects of physical reality that are primarily relevant to the endeavors of humanity. That the behavior of a six state Turing machine might be unpredictable via a few lines of text does not surprise me in the slightest. A…

[deleted]

Re: BusyBeaver(6) Is Quite Large

#98

Earlier quoted context omitted.

But the comment is not just saying something negative. It is implying that claims from the article like "Then, three days ago, Tristan wrote again to say that mxdys has improved the bound again, to BB(6)>9_2_2_2" are not real results. The justification for these not being real results is solely based off whether author is actually on the forefront of research.

I think you're touching on something important here. OP isn't making a ad hominem fallacy in a logical argument sense - it's not saying "Aaronson is wrong because he's not a frontline researcher." But you're absolutely right to feel uncomfortable with their approach. There's something off-putting about dismissing someone's reporting of research developments, even if you prefer more comprehensive coverage, or there's…

>ex. "if you want the actual news, read Tucker, not Krugman" isn't an ad hominem towards Krugman.

But how you justify that could be one. If you are just attacking the person instead of their reporting I would call that ad hominem.

Re: BusyBeaver(6) Is Quite Large

#99

Earlier quoted context omitted.

This ignores the fact that it is not so easy to find natural interesting statements that are independent of ZFC. Statements that are independent of ZFC are a dime a dozen when doing foundations of mathematics, but they're not so common in many other areas of math. Harvey Friedman has done interesting work on finding "natural" statements that are independent of ZFC, but there's dispute about how natural they are. http…

Yeah, I’m quite familiar with Friedman’s work. I mentioned him and his Grand Conjecture in another comment. > This ignores the fact that it is not so easy to find natural interesting statements that are independent of ZFC. I’m not ignoring this fact—just observing that the sheer difficulty of the task seems to have encouraged mathematicians to pursue other areas of work beside foundational topics, which is a bit unfo…

I agree most working mathematicians have limited interest in foundational topics. To me, that seems harmless enough.

> approximate those aspects of physical reality that are primarily relevant to the endeavors of humanity.

This is the comment that made me think that you were saying we needed more work on foundations for math as it is used in the sciences, and that doesn't match my understanding. Did I read it differently than you meant it?

Re: BusyBeaver(6) Is Quite Large

#100
post #89
post #72

Earlier quoted context omitted.

Within ZFC one can prove that any two models of second order PA are isomorphic. ZFC proves that PA is consistent. ZFC is good enough to capture arithmetical truth.

Unfortunately no, ZFC isn't good enough to capture arithmetical truth. The problem is that there are nonstandard models of ZFC where every single model of second-order PA within is itself nonstandard. There are even models of ZFC where a certain specific computer program, known as the "universal algorithm" [1], solves the halting problem for all standard Turing machines. https://jdh.hamkins.org/the-universal-algorith…

ZFC allows models of second order PA and proves that those models are all isomorphic. Within each model of ZFC there is no such thing as a nonstandard model of second order PA. One can only think it is nonstandard by looking from outside the model, no? What theorem of second order PA is ZFC unable to prove?

This is similar to how there are countable models of ZFC but those models think of themselves as uncountable. They are countable externally and not internally.

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