You're viewing an archive of David Simmons-Duffin's website from June 2003 - December 2008.

(4:04:42 PM) FluxDrip: lo
(4:04:53 PM) PrincetonGuy: sup matt
(4:04:57 PM) FluxDrip: not much
(4:05:07 PM) FluxDrip: how's life at Princeton?
(4:05:14 PM) PrincetonGuy: good
(4:05:19 PM) PrincetonGuy: lots and lots and lots of work
(4:05:24 PM) PrincetonGuy: all of it challenging
(4:05:25 PM) PrincetonGuy: nah
(4:05:26 PM) PrincetonGuy: i lie
(4:05:26 PM) FluxDrip: yeah. I think that's pretty much universal
(4:05:34 PM) PrincetonGuy: about 2/3 challenging
(4:05:35 PM) PrincetonGuy: 1/3 bs
(4:05:40 PM) PrincetonGuy: same at harvard?
(4:05:49 PM) FluxDrip: I don't have much bs, unfortunately
(4:05:59 PM) PrincetonGuy: it's all bs really
(4:06:00 PM) FluxDrip: but that's probably mostly a function of classes
(4:06:01 PM) PrincetonGuy: esp math
(4:06:07 PM) PrincetonGuy: and physics
(4:06:07 PM) FluxDrip: heh - what math class are you taking?
(4:06:14 PM) PrincetonGuy: like analysis
(4:06:16 PM) FluxDrip: I don't find my physics class to be bs
(4:06:17 PM) PrincetonGuy: and linear algebra
(4:06:24 PM) PrincetonGuy: all proofs
(4:06:26 PM) FluxDrip: right
(4:06:30 PM) PrincetonGuy: physics is mostly proofs too though
(4:06:34 PM) PrincetonGuy: astrophysics is PURE ps
(4:06:35 PM) PrincetonGuy: bs
(4:06:35 PM) FluxDrip: metric topology? or mostly euclidean topology?
(4:06:47 PM) PrincetonGuy: math is half half
(4:06:50 PM) PrincetonGuy: physics is euclid
(4:06:53 PM) PrincetonGuy: astro is all metric
(4:06:54 PM) FluxDrip: well right
(4:06:58 PM) FluxDrip: and again
(4:06:59 PM) FluxDrip: right
(4:07:06 PM) FluxDrip: because you don't use the euclidean metric in spacetime
(4:07:18 PM) PrincetonGuy: i should hope not
(4:07:21 PM) FluxDrip: but I doubt in astrophysics you're doing work in arbitrary metric spaces...
(4:07:31 PM) PrincetonGuy: thats' not entirely true
(4:07:44 PM) FluxDrip: hmm
(4:07:46 PM) PrincetonGuy: we spent maybe 2 weeks playing with metrics
(4:07:54 PM) PrincetonGuy: from then on harder stuff assumign metrics
(4:08:49 PM) PrincetonGuy: what's; ure major man?
(4:09:37 PM) FluxDrip: probably cs and physics
(4:10:17 PM) PrincetonGuy: nice
(4:10:20 PM) PrincetonGuy: what about math?
(4:11:14 PM) FluxDrip: I took linear algebra and basic topology last semester
(4:11:25 PM) FluxDrip: what kind of harder stuff did you do in your math class?
(4:11:40 PM) PrincetonGuy: algebra
(4:11:50 PM) FluxDrip: what sorts of algebra?
(4:12:28 PM) PrincetonGuy: groups
(4:12:29 PM) PrincetonGuy: rnigs
(4:12:36 PM) PrincetonGuy: sylow theorem
(4:12:42 PM) PrincetonGuy: euclidian rings
(4:12:52 PM) PrincetonGuy: just bs like that
(4:12:59 PM) FluxDrip: that is in fact algebra
(4:13:06 PM) PrincetonGuy: yeh i think so
(4:13:27 PM) PrincetonGuy: doesnt' apply too much to physics though
(4:13:32 PM) PrincetonGuy: though maybe later with string theory
(4:13:42 PM) FluxDrip: mm
(4:13:44 PM) FluxDrip: Ed whitten and all
(4:13:46 PM) PrincetonGuy: it's more of hte approach of how to prove i am lookin for
(4:13:48 PM) FluxDrip: err
(4:13:51 PM) FluxDrip: witten
(4:14:15 PM) PrincetonGuy: yeh
(4:14:20 PM) PrincetonGuy: analysis is good too
(4:14:53 PM) FluxDrip: hmm... I have a stupid math problem I can't figure out... feel like giving a crack at it?
(4:15:09 PM) PrincetonGuy: waht subject?
(4:16:45 PM) FluxDrip: We have to show that:
GIVEN ANY ISOTROPIC POLYTOPE IN C^N , THERE EXISTS AN ISOTROPIC SUBSET OF THE P-adics OF MEASURE 0 WITH RESPECT TO THAT POLYTOPE
(4:17:36 PM) PrincetonGuy: never heard the word polytope
(4:17:38 PM) PrincetonGuy: what does it mean?
(4:18:42 PM) FluxDrip: A regular polytope is a generalization of the Platonic solids to an arbitrary dimension.
(4:19:59 PM) PrincetonGuy: i can't think of any easy way to prove it
(4:20:30 PM) PrincetonGuy: but prolly induction
(4:20:31 PM) FluxDrip: they give a hint
(4:21:12 PM) FluxDrip: they suggest starting with some complex manifold locally resembling C^2
(4:23:34 PM) PrincetonGuy: i would stil use induction though
(4:25:21 PM) FluxDrip: I dunno. I think the professor may have messed up somewhere. It doesn't seem logical
(4:25:37 PM) FluxDrip: How can something be of measure 0 with respect to a polytope?
(4:25:54 PM) PrincetonGuy: because it's a subset of that field?
(4:26:09 PM) FluxDrip: I'm not exactly sure what is meant by measure 0 then...
(4:26:30 PM) PrincetonGuy: yeh neither am i
(4:26:39 PM) PrincetonGuy: i think onceu that is defiend it should be easy to show induction
(4:26:47 PM) FluxDrip: some analysis class you're in...
(4:27:07 PM) PrincetonGuy: yah
(4:28:26 PM) PrincetonGuy: we never used these measures in describing riemann
(4:28:33 PM) FluxDrip: the mathematician?
(4:29:17 PM) PrincetonGuy: anh the sums
(4:29:38 PM) FluxDrip: hmm...I think the concept of measure is fairly essential to topology on an arbitrary metric
(4:30:00 PM) PrincetonGuy: true
(4:30:37 PM) PrincetonGuy: a finite # of points has 0 measure
(4:30:47 PM) PrincetonGuy: i mean a set of suck
(4:30:48 PM) PrincetonGuy: such
(4:31:11 PM) PrincetonGuy: and prolly also if u can arrange them in a sequence the measure will be 0
(4:31:11 PM) FluxDrip: right but a polytope is not finite
(4:31:16 PM) PrincetonGuy: even if it's finite
(4:31:18 PM) PrincetonGuy: infintie
(4:31:24 PM) PrincetonGuy: yeh i think that's true
(4:31:26 PM) FluxDrip: hmm
(4:31:27 PM) FluxDrip: damn
(4:31:39 PM) FluxDrip: induction is bound to fail on measure 0 subsets of the P-adics though
(4:31:47 PM) FluxDrip: by the continuum hypothesis
(4:32:30 PM) PrincetonGuy: but all the parts which make up the subset are of measure of 0
(4:33:14 PM) FluxDrip: what do you mean?
(4:33:37 PM) FluxDrip: (then there wouldn't be a polytope...)
(4:33:40 PM) PrincetonGuy: if u can show one of the lower subsets has a measure 0
(4:33:51 PM) PrincetonGuy: then all the subsets should have the same measure
(4:34:02 PM) FluxDrip: but...we need to show there's a polytope
(4:34:04 PM) PrincetonGuy: as u can't make up something of measure 0 from anyting else
(4:34:06 PM) FluxDrip: and not that they have measure 0
(4:34:09 PM) FluxDrip: what paving are you using?
(4:34:19 PM) PrincetonGuy: i am making it up
(4:34:28 PM) FluxDrip: huh?
(4:34:35 PM) PrincetonGuy: we dind't see polytopes in analysis
(4:34:44 PM) FluxDrip: it's a shape
(4:34:44 PM) PrincetonGuy: but ure right we did see measure
(4:34:49 PM) FluxDrip: a square? a rectangle?
(4:34:55 PM) FluxDrip: how about a rectangular prism.
(4:34:58 PM) FluxDrip: cept
(4:35:00 PM) PrincetonGuy: in what space?
(4:35:04 PM) FluxDrip: generalized into the set of the complex numbers...
(4:35:11 PM) FluxDrip: here
(4:35:14 PM) FluxDrip: try this
(4:35:25 PM) FluxDrip: given a square of non-zero area in R^2, how can we pave it with subsets of measure 0?
(4:35:31 PM) FluxDrip: i think if I can do that I can get the rest of the waay
(4:35:33 PM) FluxDrip: way, even
(4:37:46 PM) PrincetonGuy: i remeber some thm like
(4:38:02 PM) PrincetonGuy: if A is compact and has 0 measure -> A has content 0
(4:38:15 PM) FluxDrip: which imples?
(4:38:16 PM) FluxDrip: err
(4:38:18 PM) FluxDrip: implies?
(4:38:58 PM) PrincetonGuy: nothign really cuz it doesn't go backwards
(4:39:25 PM) PrincetonGuy: the subsets of this square must 0 measure?
(4:39:35 PM) PrincetonGuy: and the square must have non-zero measure?
(4:39:39 PM) FluxDrip: no, the paving must be made up off subsets of measure 0
(4:39:45 PM) FluxDrip: and the square has non-zero area
(4:40:35 PM) PrincetonGuy: could it be a question of countability and how many subunits u need?
(4:42:21 PM) FluxDrip: hmm...not really. if you needed uncountably many subunits then it would be a somewhat trivial paving, no?
(4:42:36 PM) PrincetonGuy: 0 measure is pretty trivial
(4:42:56 PM) PrincetonGuy: or at least can easily be so if u wish
(4:43:31 PM) FluxDrip: hmm...it seems like if it's trivial the answer should be self-evident
(4:44:24 PM) PrincetonGuy: and it easily could be so with this kidn of definitin
(4:44:39 PM) FluxDrip: sorry what?
(4:44:54 PM) FluxDrip: so...what is it?
(4:46:06 PM) PrincetonGuy: with uncountable 0 measures it would be possible to construct an area
(4:46:43 PM) FluxDrip: by definition, a set is not of measure 0 if it can only be paved with uncountably many subsets...
(4:46:57 PM) PrincetonGuy: aiite
(4:47:08 PM) PrincetonGuy: then i dun see an easy way to do this
(4:47:50 PM) PrincetonGuy: aiite
(4:47:56 PM) PrincetonGuy: i am gonna go do some nuymber thoery
(4:47:58 PM) FluxDrip: oh!
(4:48:03 PM) FluxDrip: I just got it!
(4:48:05 PM) PrincetonGuy: good man
(4:48:07 PM) PrincetonGuy: good job
(4:48:46 PM) FluxDrip: it's almost trivial - construct it directly from a basis of the P-adics
(4:49:03 PM) PrincetonGuy: ah true
(4:49:18 PM) FluxDrip: how silly we were...
(4:49:34 PM) PrincetonGuy: haah
(4:49:35 PM) PrincetonGuy: sure
(4:49:43 PM) PrincetonGuy: u have break yet?
(4:49:56 PM) FluxDrip: not next week but the week after
(4:50:21 PM) PrincetonGuy: nice
(4:50:23 PM) PrincetonGuy: mine starts tomororw

note: this is a real IM conversation, and an excellent illustration of a possible application of the Theorem of the Day. "PrincetonGuy" is a replacement screenname, put in place to reduce someone's risk of burning ears.