Monday, July 14, 2014

If physics blogs were like economics blogs

I recently came across some interesting new work in computational cosmology, this time in a paper from Jan Ambjorn, Timothy Budd that lent itself to some rather beautiful 2-dimensional universes. Check out this video for some of these 2D universes embedded in 3D:

Causal dynamical triangulation may potentially be the long-sought quantum theory of gravity. It constructs universes from tiny triangles ("simplices"). Older but similar "brute force" approaches failed, producing universes with a low number of effective dimensions. However this approach assumes one extra ingredient: causality. Complexes with causality-violating simplices are forbidden, reducing the number of possible configurations. This results in universes with the "correct" number of effective dimensions.

Posted 07/14/2014 11:14am

Comments (13)

Ted A. Thomas III I've spent 30+ years as a manager of a piano moving company, so I think I know a thing or two about gravity. All I can say is that this isn't how gravity works in the real world. You have to apply force perpendicular to the ground plane in order to move objects along the z-direction.

Anonymous LOL this is completely wrong

jeffkeen22 This ignores what Aristotle said: everything moves toward its natural place.
Anonymous Ah, but Aristotle got heliocentrism wrong. 
jeffkeen22 Heliocentrism was the downfall our society. We're living in a dark age now. 
Anonymous You realize Aristotle was a geocentrist right?
unlearningphysics Newton knew about this all along. He's credited with discovering calculus but he used trigonometry in his Principia for a reason.

Paulite2000 You liberals think government can fix everything.
progman2000 It can!
StudentofPhilosophy I've long thought gravity is an illusion invented by physicists to keep ordinary people from being allowed to speak on the subject. Remember -- Newton's inverse square law is guilty of what Einstein called spooky action at a distance. Yet astrophysicists and aerospace engineers still use Newton's flawed equations to run our society. I was completely astounded when I saw this:

Physicists Pin Down Value Of Newton's Gravitational Constant

How can they pin down something that Einstein says is fundametally flawed? I was a philosophy major in college, so I am well trained in being able to spot the fundamental contradiction and circular logic.

oldisnewagain "Once upon a time a valiant fellow had the idea that men were drowned in water only because they were possessed with the idea of gravity. If they were to knock this notion out of their heads, say by stating it to be a superstition, a religious concept, they would be sublimely proof against any danger from water. His whole life long he fought against the illusion of gravity, of whose harmful results all statistics brought him new and manifold evidence. This valiant fellow was the type of the new revolutionary philosophers in Germany. "
aphysicist Actually that may be more correct than you know -- gravity may be an entropic force and the local direction of the gravitational field is the direction of the holographic dimension.
timecube4444 1000 dollars to anyone who can disprove the Harmonic Cube


PS This is kind of a half-baked joke, but apparently I was scooped in concept by John Cochrane of all people.

PPS I really think the CDT group is doing really neat stuff -- actually that is what I devoted my spare time to playing with before I took up the economics blogging. I was hoping to speed up the computations with GPU processing, but it appears they've already gotten there.


  1. Does any intelegent person with experience of reading the "Huffing" post still read it?

    1. It was the first link in Google news that had the search terms "Newton" and "gravity" -- that is about as much of an endorsement as I can give right now :)

  2. OK, this will sound like a dopey question, but the comments section there is entirely fictional I assume?.... :D

    I like this:


    If that's real, that'd be weird.

    1. Yes, the 13 comments are entirely fictional :)

      I just thought it was a funny play on "unlearningeconomics" ... to whom I don't mean any disrespect.

    2. Right, I got the unlearned reference. :D ... any others (that I may have missed)?

      I thought perhaps Major_DegreesOfFreedom might work too.

      O/T: you probably already say this from Tony Yates (since Sumner linked to it):

      I wrote a comment in there about mathematical models for MM... before reading what Nick Rowe wrote in the comments (right above me). I asked Tony it he was frustrated by an apparent lack of models from the MM crowd... both Nick and Scott refer to models, but I can't say I can reconcile their statements. This was Nick's final paragraph in the comment I'm referring to:

      "MM is more about interpreting existing models differently and interpreting the existing data differently. Monetary policy is 99% expectations, so how monetary policy is communicated is 99% of how it works. And market prices (especially asset prices) are the main source of information we have on how that communication is being received."

      What's your view? More phlogiston?

    3. Major DOF, that's a good one! :)

      I actually wrote down a version of Sumner's model (a first approximation?):

      I posted a comment with a link on his post on Yates.

      If economics is 99% expectations then economics is 99% question begging.

      (In my view at least.)

    4. "If economics is 99% expectations then economics is 99% question begging."

      I love it!

  3. Jason, an idea for a future blog post: Create a fictional econ post w/ fictional comments (as above), but with certain key sentences underlined and numbered. Then underneath you have a list (A, B, C, ... etc) of phrases like "just-so story," "assuming the conclusion" etc, in the form of a quiz: match the letter corresponding to the descriptive phrase (A, B, etc) with the numbered sentence from the fake post and comments (1, 2, etc). They don't all have to be bad things. Then the next post you give the answers.

    Maybe there wouldn't be enough to flush out a full interesting post.

    1. Ha!

      Although it can be difficult to point out assuming the conclusion in just a couple of sentences. Sometimes it's somewhere in the unstated assumptions :)

  4. Jason, you might like this story about what the phrase "modern jackass" means. I feel like a "modern jackass" pretty much every time I write anything on an econ blog comment section, but particularly when I'm trying to convey some point about an econ theory (such as yours!), which I don't fully understand.

    I try to console myself by imagining I'm usuallly not the biggest, loudest or most obnoxious modern jackass in the room (and thus I can hide in the noise to a certain extent). :D

    Really though, econ blog comment sections must be pretty thick with modern jackassery, don't you think?

    1. I sometimes feel like the "physicist" in that story.

      However I console myself with the fact that I'm not saying economists are wrong or misguided or anything.

    2. You read a lot of that story!... I meant to tell you that they cover the "modern jackass" concept in the first few paragraphs. Well, I hope you enjoyed it.

      I don't think you have much to worry about... especially with commentators like me around making you look good (by comparison)! :D

  5. Jason, you may find this interesting: Mike Freimuth's model of endogenous money:

    Here's his final paragraph:

    "The thing you should take away from this is that monetary policy, as we are currently doing it (inflation targeting) works much the way we think it works but that I think it either leads, in a predictable way, into a “liquidity trap” and a deflationary recession in the long run or it requires ever-expanding “fiscal policy” to keep this from happening."

    Nick Rowe comments there too.

    1. That *is* interesting. I will have to study it some more, but that is basically the conclusion of the information transfer model. I am not sure the mechanism is the same, though (that's what I have to look at more closely).

    2. Jason,

      I would be shocked if the mechanism is the same haha. It's interesting that you get the same conclusion though! I guess I will have to try to figure out what he heck you are doing. =)

  6. Lol, this is great - honoured to be included ;)


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