Yeah, it's only an issue when you want to have a set of positive measure to show a binary string in ML-Random, or when you want to work on subshifts (sets closed under the 'shift left one' operation) and need everything to be distinct points without such identities creeping in.
-
-
Replying to @LargeCardinal @oe1cxw
e.g. forbidden word problems. If 0.101111... and 0.110000... are the same, then it's difficult to say that the first avoids the forbidden word '000' if the second is in some way identical to it. (just an ex. off the top of my head)
1 reply 0 retweets 1 like -
Replying to @LargeCardinal @oe1cxw
PS - this is probably the *least* weird thing about Algorithmic Randomness x-D
1 reply 0 retweets 2 likes -
Replying to @LargeCardinal
Excuse my ignorance. I've just read a bit on the topic on wikipedia. I'm mostly confused now. :) Most reals famously don't even have a finite description. So I have a hard time understanding how these questions even relate to those reals. If only I had more time. This looks cool.
1 reply 0 retweets 2 likes -
Replying to @oe1cxw
so, being honest with you - you can do just fine with these problems if you don't think of them as anything more than binary strings, i.e. you don't think of them as reals. >.< I'm very sorry if I've caused confusion...
1 reply 0 retweets 1 like -
Replying to @LargeCardinal @oe1cxw
I think this is a case where being mathematicians, we state something to avoid confusion later, but instead cause even more confusion at the start. We're rather good at that...
1 reply 0 retweets 1 like -
Replying to @LargeCardinal
Confusion just means I know there's something to learn for me. That's usually good. :) So, when you say these objects are "binary strings", these strings are still potentially infinite in length, and for most of them there's no finite program to generate them, right?
1 reply 0 retweets 1 like -
Replying to @oe1cxw
Exactly. Much of the study is for $\Pi^0_1$ classes, meaning there is some arithmetical function $\phi$, and we are saying $\forall x \, \phi(x)$ is true. After some work, this becomes equivalent to the usual interpretation:
1 reply 0 retweets 1 like -
Replying to @LargeCardinal @oe1cxw
Some initial segment ('stem') \sigma, and the cone of all its extensions.pic.twitter.com/pyQw10Fv1R
1 reply 0 retweets 1 like -
Replying to @LargeCardinal @oe1cxw
There is quite a lot of work on these - and a forthcoming book by Cenzer, a preprint of which was important in parts of my thesis I'm writing up. My fave theorem - due to Kucera: for any \Pi^0_1 class P (tree with a stem) of positive measure, P must contain a 1-random path.
2 replies 0 retweets 1 like
I think I need to learn more about this. Do you know by any chance of recordings of university lectures on these topics online? (Listening to uni lectures online is my preferred way of getting an overview of a new topic.)
-
-
Replying to @oe1cxw
Hmmm - so I've not heard of any post-graduate level logic courses online, and even then this is a 'corner' or computability theory that could be wiped out by a minibus crash... I'll have a dig around, and see if anyone's done any lectures I can find online. :)
0 replies 0 retweets 2 likesThanks. Twitter will use this to make your timeline better. UndoUndo
-
Loading seems to be taking a while.
Twitter may be over capacity or experiencing a momentary hiccup. Try again or visit Twitter Status for more information.