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Francesco Biscani

The End Of Gravity As a Fundamental Force - 6 views

science.slashdot.org/...Gravity-As-a-Fundamental-Force

phy

shared by Francesco Biscani on 11 Jan 10 - Cached
LeopoldS liked it
  • Francesco Biscani on 11 Jan 10
     
    "At a symposium at the Dutch Spinoza-instituut on 8 December, 2009, string theorist Erik Verlinde introduced a theory that derives Newton's classical mechanics. In his theory, gravity exists because of a difference in concentration of information in the empty space between two masses and its surroundings. He does not consider gravity as fundamental, but as an emergent phenomenon that arises from a deeper microscropic reality. A relativistic extension of his argument leads directly to Einstein's equations."
  • ...8 more comments...
  • Dario Izzo on 12 Jan 10
     
    Diffcult for me to fully understand / believe in the holographic principle at macroscopical scales ... potentially it looks though as a revolutionary idea.....
  • pacome delva on 13 Jan 10
     
    never heard about it... seems interesting. At first sight it seems that it is based on fundamental principle that could lead to a new phenomenology, so that could be tested. Perhaps Luzi knows more about this ? Did we ever work on this concept ?
  • Luzi Bergamin on 13 Jan 10
     
    The paper is quite long and I don't have the time right now to read it in detail. Just a few comments: * We (ACT) definitely never did anything in this direction? But: is there a new phenomenology? I'm not sure, if the aim is just to get Einstein's theory as emergent theory, then GR should not change (or only change in extreme conditions.) * Emergent gravity is not new, also Erik admits that. The claim to have found a solution appears quite frequently, but most proposals actually are not emergent at all. At least, I have the impression that Erik is aware of the relevant steps to be performed. * It's very difficult to judge from a short glance at the paper, up to which point the claims are serious and where it just starts to be advertisments. Section 6 is pretty much a collection of self-praise. * Most importantly: I don't understand how exactly space and time should be emergent. I think it's not new to observe that space is related to special canonical variables in thermodynamics. If anybody can see anything "emergent" in the first paragraphs of section 3, then please explain me. For me, this is not emergent space, but space introduced with a "sledge hammer." Time anyway seems to be a precondition, else there is nothing like energy and nothing like dynamics. * Finally, holography appears to be a precondition, to my knowledge no proof exists that normal (non-supersymmetric, non-stringy, non-whatever) GR has a holographic dual.
  • Luzi Bergamin on 13 Jan 10
     
    Update: meanwhile I understood roughly what this should be about. It's well known that BH physics follow the laws of theormodynamics, suggesting the existence of underlying microstates. But if this is true, shouldn't the gravitational force then be emergent from these microstates in the same way as any theromdynamical effect is emergent from the behavior of its constituents (e.g. a gas)? If this can be prooven, then indeed gravity is emergent. Problem: one has to proof that *any* configuration in GR may be interpreted as thermodynamical, not just BHs. That's probably where holography comes into the play. To me this smells pretty much like N=4 SYM vs. QCD. The former is not QCD, but can be solved, so all stringy people study just that one and claim to learn something about QCD. Here, we look at holographic models, GR is not holographic, but who cares... Engineering problems...
  • LeopoldS on 13 Jan 10
     
    is there any experimental or observational evidence that points to this "solution"?
  • Luzi Bergamin on 13 Jan 10
     
    Are you joking??? :D
  • pacome delva on 14 Jan 10
     
    I was a bit fast to say it could be tested... apparently we don't even know a theory that is holographic, perhaps a string theory (see http://arxiv.org/abs/hep-th/9409089v2). So very far from any test...
  • LeopoldS on 14 Jan 10
     
    Luzi, I miss you!!!
  • Luzi Bergamin on 14 Jan 10
     
    Leo, do you mean you liked my comment on your question more than Pacome's? Well, the ACT has to evolve and fledge, so no bullshitting anymore, but serious and calculating answers... :-) Sorry Pacome, nothing against you!! I just LOVE this Diigo because it gives me the opportunity for a happy revival of my ACT mood.
  • pacome delva on 14 Jan 10
     
    haha, today would have been great to show your mood... we had a talk on the connection between mind and matter !!
Juxi Leitner

Touchable Holography - 0 views

www.alab.t.u-tokyo.ac.jp/...SIGGRAPH09-TH.html

holography haptics

shared by Juxi Leitner on 18 Sep 09 - Cached
  • Juxi Leitner on 18 Sep 09
     
    "feeling holographic raindrops fall on your hand"
pacome delva

How to walk through walls - 6 views

physicsworld.com/...44576

phy transformation_optics

shared by pacome delva on 15 Dec 10 - No Cached
  • Luzi Bergamin on 15 Dec 10
     
    and yet another TO nonsense... And why always Harry Potter, dont't these darn scientists have more imagination or is their intellectual level just as low as being unable to read more complex literature than J.K. Rawling?? btw.: how about this skype session on TO, Leo?
  • dejanpetkow on 15 Dec 10
     
    Combine it with touchable holography (search for SIGGRAPH 2009 at youtube) and name it Holosuite 0.1.
Paul N

Microsoft Hololens, Occulus rift killer? - 1 views

www.youtube.com/watch

FUN

shared by Paul N on 27 Jan 15 - No Cached
  • Paul N on 27 Jan 15
     
    Probably old news by now, but this thing sounds so awesome it warrants an entry
  • Thijs Versloot on 28 Jan 15
     
    Looks like fun! Note though, I'm always slightly annoyed when people use holography only because it sounds cool. because clearly this is not a hologram! Definition: a three-dimensional image formed by the interference of light beams from a laser or other coherent light source. I am sure this is not what is happening in these goggles.
  • Paul N on 28 Jan 15
     
    I think they suspect that "hologram" would sell better than "yet-another-augmented-reality-goggle"
Marcus Maertens

Big Hero 6's Programmable Nanobots Are on the Horizon - 2 views

futurism.com/...-programmable-nanobots-horizon

AI technology

shared by Marcus Maertens on 09 Dec 15 - No Cached
  • Marcus Maertens on 09 Dec 15
     
    This collaborating swarm of drones acts as 3D pixels (voxels) to create giant, flying interactive displays.
  • Thijs Versloot on 10 Dec 15
     
    I have never understood the flying part of these things. Isn't it really impracticle to have all those tiny quadrocopters zooming around. My money is on holography or still a google glass type of device, if only considering the energy requirements for doing anything kinetically.
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