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Luís F. Simões

Polynomial Time Code For 3-SAT Released, P==NP - Slashdot - 0 views

science.slashdot.org/...me-Code-For-3-SAT-Released-PNP

INF computer science mathematics algorithm complexity P=NP?

shared by Luís F. Simões on 20 Jan 11 - No Cached
  • "Vladimir Romanov has released what he claims is a polynomial-time algorithm for solving 3-SAT. Because 3-SAT is NP-complete, this would imply that P==NP. While there's still good reason to be skeptical that this is, in fact, true, he's made source code available and appears decidedly more serious than most of the people attempting to prove that P==NP or P!=NP. Even though this is probably wrong, just based on the sheer number of prior failures, it seems more likely to lead to new discoveries than most. Note that there are already algorithms to solve 3-SAT, including one that runs in time (4/3)^n and succeeds with high probability. Incidentally, this wouldn't necessarily imply that encryption is worthless: it may still be too slow to be practical."
  • Luís F. Simões on 20 Jan 11
     
    here we go again...
  • Luís F. Simões on 28 Feb 11
     
    slashdot: "Russian computer scientist Vladimir Romanov has conceded that his previously published solution to the '3 SAT' problem of boolean algebra does not work."
Luís F. Simões

The Fantastical Promise of Reversible Computing  - Technology Review - 2 views

www.technologyreview.com/...26308

INF reversible logic computing chip electronics quantum cellular_automata

shared by Luís F. Simões on 25 Jan 11 - No Cached
  • Reversible logic could cut the energy wasted by computers to zero. But significant challenges lie ahead.
  • By some estimates the difference between the amount of energy required to carry out a computation and the amount that today's computers actually use, is some eight orders of magnitude. Clearly, there is room for improvement.
  • There are one or two caveats, of course. The first is that nobody has succeeded in building a properly reversible logic gate so this work is entirely theoretical. But there are a number of computing schemes that have the potential to work like this. Thapliyal and Ranganathan point in particular to the emerging technology of quantum cellular automata and show how their approach might be applied.
  • ...1 more annotation...
  • Ref: arxiv.org/abs/1101.4222: Reversible Logic Based Concurrent Error Detection Methodology For Emerging Nanocircuits
  • Dario Izzo on 26 Jan 11
     
    We did look at making computation powers more efficient from the bio perspective (efficiency of computations in brain). This paper was actually the base for our discussion on a new approsach to computing http://atlas.estec.esa.int/ACTwiki/images/6/68/Sarpeshkar.pdf and led to several ACT internal studies
  • Luís F. Simões on 26 Jan 11
     
    here is the paper I told you about, on the computational power of analog computing: http://dx.doi.org/10.1016/0304-3975(95)00248-0 you can also get it here: http://www.santafe.edu/media/workingpapers/95-09-079.pdf
santecarloni

Breakthrough Propulsion Physics - 7 views

www.grc.nasa.gov/bpp

propulsion physics space

shared by santecarloni on 26 Jan 11 - Cached
  • santecarloni on 26 Jan 11
     
    The competition is open....
  • Luzi Bergamin on 26 Jan 11
     
    And what does one win in the end? Yet another unfeasible concept to be archived somewhere in a journal? Look at "Millis hypothetical drives"... Give me a break, for sure!!
  • Dario Izzo on 26 Jan 11
     
    I like the sentence "16 peer-reviewed journal articles, and an award-winning website (Warp-When), all for a total investment of less than $1.6M". This gives 100.000 dollars per peer-reviewed paper (we neglect the award-winning web-site under the assumption that is the easy part....). With these number the ACT in 2010 cashed 1.4 millions only in research papers making it an obvious good investment for the European Space Agency also in austerity times!!!
LeopoldS

Human Brain Project - Goals - 3 views

www.humanbrainproject.eu/goals.html

AI bio technology science

shared by LeopoldS on 20 May 11 - No Cached
  • LeopoldS on 20 May 11
     
    can we contribute in any way to this - or alternatively benefit from this research already now?
  • ...4 more comments...
  • Luzi Bergamin on 20 May 11
     
    Watch out!! I read quite a lot about the contribution by EPFL (apparently coordinator) and their boss, Henry Markram. From what I read, this is not really science, but mainly a PR campaign. The main motor in this project is attracting a lot of money and the main aim to do so is promising a lot of stuff that nobody will be able to deliver. Accordingly, Markram is a very controversial person in the business...
  • Luzi Bergamin on 20 May 11
     
    Oups, sorry! Of course I meant, "the main MEAN to do so...", but the aim justifies the means. Well, that's exactly Markram's motto, I guess.
  • LeopoldS on 21 May 11
     
    interesting info indeed ... I though still think that the overall goal of this project, even if too ambitious for the time being is interesting, no?
  • Luzi Bergamin on 22 May 11
     
    It's not about interesting or not, it's about serious science or not. Also the goal of a fortune-teller is interesting, isn't it? Any description of a good science project is too ambitious, that's normal and not necessarily PR. But personally I think there is a certain limit where a science project becomes a bad SciFi thriller. This one here is a dime novel, I think. But the too ambitious is not the only point I became very doubtful. I have seen quite a number of scientists and engineers from different fields; what I read about the character and attitude of this guy just hints towards the worst case scenario. It's presumptive evidence, I know...
  • LeopoldS on 22 May 11
     
    that bad! wow ....
  • Luzi Bergamin on 22 May 11
     
    You know me, I'm the bullshitter... You remember Kurzweil and his Singularity-nonsense. In a way this was very similar. Though I think Kurzweil and Markram are very different characters (The Singularity essentially is a religion, I can't see anything like that in Markram's claims) they seem to share an important point: they are both complete nerds that apparently never spent a single thought on the limits of science (in its English meaning) in general nor of their particular research field in specific. One may find this excusable, I don't. But even then, they make claims that the nerdest nerd must know that they are completely unrealistic and thus I just have to assume that they claim their nonsense on purpose. The reason in Markram's case clearly seems to be money. But all this does not mean that these nerds cannot produce valuable results.
Luís F. Simões

Massively Parallel Computer Built From Single Layer of Molecules - Technology Review - 3 views

www.technologyreview.com/...27291

organic molecules parallel computing cellular_automata

shared by Luís F. Simões on 28 Oct 11 - No Cached
  • Japanese scientists have built a cellular automaton from individual molecules that carries out huge numbers of calculations in parallel
  • Ref: arxiv.org/abs/1110.5844: Massively Parallel Computing An An Organic Molecular Layer
  • Luís F. Simões on 28 Oct 11
     
    :) so Technology Review wrote the article now, based on an arXiv paper uploaded only now, but actually the paper was already published in Nature last year: http://dx.doi.org/10.1038/nphys1636
Luís F. Simões

Geoffrey West: The surprising math of cities and corporations | Video on TED.com - 3 views

www.ted.com/...f_cities_and_corporations.html

TED cities companies growth complex_systems complex_networks

shared by Luís F. Simões on 26 Oct 11 - No Cached
  • Physicist Geoffrey West has found that simple, mathematical laws govern the properties of cities -- that wealth, crime rate, walking speed and many other aspects of a city can be deduced from a single number: the city's population. In this mind-bending talk from TEDGlobal he shows how it works and how similar laws hold for organisms and corporations.
  • For those who felt that Geoffrey glossed over the implications for cities and companies, the following article in the New York Times did a respectable job of drawing conclusions from Dr. West's paper: http://www.nytimes.com/2010/12/19/magazine/19Urban_West-t.html
  • dejanpetkow on 27 Oct 11
     
    Tokyo has a very large population and one of the smallest crime rates in the world, in fact Tokyo is known to be the safest big city in the world (w.r.t. crime). It is hard to believe that the crime rate in L.A. is in the same order of magnitude.
jmlloren

Scientists discover how to turn light into matter after 80-year quest - 5 views

phys.org/...-05-scientists-year-quest.html

PHY MAD

shared by jmlloren on 19 May 14 - No Cached
  • Thijs Versloot on 19 May 14
     
    Theoretized 80 years ago was Breit-Wheeler pair production in which two photons result in an electron-positron pair (via a virtual electron). It is a relatively simple Feynmann diagram, but the problem is/was how to produce in practice a high energy photon-photon collider... The collider experiment that the scientists have proposed involves two key steps. First, the scientists would use an extremely powerful high-intensity laser to speed up electrons to just below the speed of light. They would then fire these electrons into a slab of gold to create a beam of photons a billion times more energetic than visible light. The next stage of the experiment involves a tiny gold can called a hohlraum (German for 'empty room'). Scientists would fire a high-energy laser at the inner surface of this gold can, to create a thermal radiation field, generating light similar to the light emitted by stars. They would then direct the photon beam from the first stage of the experiment through the centre of the can, causing the photons from the two sources to collide and form electrons and positrons. It would then be possible to detect the formation of the electrons and positrons when they exited the can. Now this is a good experiment... :)
  • ...6 more comments...
  • jmlloren on 19 May 14
     
    The solution of thrusting in space.
  • dejanpetkow on 20 May 14
     
    Thrusting in space is solved already. Maybe you wanted to say something different?
  • Thijs Versloot on 21 May 14
     
    Thrusting until your fuel runs out is solved, in this way one can produce mass from, among others, solar/star energy directly. What I like about this experiment is that we have the technology already to do it, many parts have been designed for inertial confinement fusion.
  • johannessimon81 on 29 May 14
     
    I am quite certain that it would be more efficient to use the photons directly for thrust instead of converting them into matter. Also, I am a bit puzzled at the asymmetric layout for photon creation. Typically, colliders use two beam of particle with equal but opposite momentum. Because the total momentum for two colliding particles is zero the reaction products are produced more efficiently as a minimum of collision energy is waisted on accelerating the products. I guess in this case the thermal radiation in the cavity is chosen instead of an opposing gamma ray beam to increase the photon density and increase the number of collisions (even if the efficiency decreases because of the asymmetry). However, a danger from using a high temperature cavity might be that a lot of thermionic emission creates lots of free electrons with the cavity. This could reduce the positron yield through recombination and would allow the high energetic photons to loose energy through Compton scattering instead of the Breit-Wheeler pair production.
  • Thijs Versloot on 30 May 14
     
    Well, the main benefit from e-p pair creation might be that one can accelerate these subsequently to higher energies again. I think the photon-photon cross-section is extremely low, such that direct beam-beam interactions are basically not happening (below 1/20.. so basically 0 according to quantum probability :P), in this way, the central line of the hohlraum actually has a very high photon density and if timed correctly maximizes the reaction yield such that it could be measured.
  • johannessimon81 on 30 May 14
     
    I agree about the reason for the hohlraum - but I also keep my reservations about the drawbacks. About the pair production as fuel: I pretty sure that your energy would be used smarter in using photon (not necessarily high energy photons) for thrust directly instead of putting tons of energy in creating a rest-mass and then accelerating that. If you look at E² = (p c)²+(m0 c)² then putting energy into the mass term will always reduce your maximum value of p.
  • Thijs Versloot on 31 May 14
     
    True, but isnt it E2=(pc)^2 + (m0c^2)^2 such that for photons E\propto{pc} and for mass E\propto{mc^2}. I agree it will take a lot of energy, but this assumes that that wont be the problem at least. The question therefore is whether the mass flow of the photon rocket (fuel consumed to create photons, eg fission/fusion) is higher/lower than the mass flow for e-p creation. You are probably right that the low e-p cross-section will favour direct use of photons to create low thrust for long periods of time, but with significant power available the ISP might be higher for e-p pair creation.
  • johannessimon81 on 03 Jun 14
     
    In essence the equation tells you that for photons with zero rest mass m0 all the energy will be converted to momentum of the particles. If you want to accelerate e-p then you first spend part of the energy on creating them (~511 keV each) and you can only use the remaining energy to accelerate them. In this case the equation gives you a lower particle momentum which leads to lower thrust (even when assuming 100% acceleration efficiency). ISP is a tricky concept in this case because there are different definitions which clash in the relativistic context (due to the concept of mass flow). R. Tinder gets to a I_SP = c (speed of light) for a photon rocket (using the relativistic mass of the photons) which is the maximum possible relativistic I_SP: http://goo.gl/Zz5gyC .
Thijs Versloot

Effectively Universal Behavior of Rotating Neutron Stars in General Relativity Makes Th... - 0 views

journals.aps.org/...PhysRevLett.112.121101

shared by Thijs Versloot on 02 Apr 14 - No Cached
  • Thijs Versloot on 02 Apr 14
     
    Recently, it was shown that slowly rotating neutron stars exhibit an interesting correlation between their moment of inertia I, their quadrupole moment Q, and their tidal deformation Love number λ (the I-Love-Q relations), independently of the equation of state of the compact object. By exploiting this relation, we can describe quite accurately the geometry around a neutron star with fewer parameters, even if we don't know precisely the equation of state. Side note: I-Love-Q relations? Some inner chuckles in the Fundamental Physicist community.. :)
Thijs Versloot

Resource availability towards a self-sufficient Mars Colony - 0 views

www.nss.org/...f-SufficientMartianOutpost.pdf

in-situ resource utilization Mars colony

shared by Thijs Versloot on 31 Oct 14 - No Cached
  • Thijs Versloot on 31 Oct 14
     
    Regarding our discussion on resource self-sufficiency of a Mars colony. Would it ever be possible (from a resource perspective that is..) A NASA report on availability of resources. A self-sufficiency trade study described in Boston (1996) identifies the mission duration at which the development of local life support resources becomes advantageous. Within 30 days, without recycling, or with the equivalent leakage, it becomes advantageous to derive oxygen from local resources. The time constants for water and food are about 6 months and 3 years, respectively.
  • Dario Izzo on 31 Oct 14
     
    I guess it depends on the number of astronauts that have to be supporte ... 3 years for food looks like a lot
Nina Nadine Ridder

Can physical exercise enhance long-term memory? - 1 views

medicalxpress.com/...physical-long-term-memory.html

BIO exercise_impact brain science

shared by Nina Nadine Ridder on 25 Nov 15 - No Cached
  • Nina Nadine Ridder on 25 Nov 15
     
    Exercise can enhance the development of new brain cells in the adult brain, a process called adult neurogenesis. These newborn brain cells play an important role in learning and memory. A new study has determined that mice that spent time running on wheels not only developed twice the normal number of new neurons, but also showed an increased ability to distinguish new objects from familiar objects.
  • LeopoldS on 10 Dec 15
     
    wow ... time to start running again ...
Marcus Maertens

[1703.00045] Aggregated knowledge from a small number of debates outperforms the wisdom... - 1 views

arxiv.org/abs/1703.00045##

fun INF

shared by Marcus Maertens on 20 Dec 18 - No Cached
mkisantal liked it
  • Marcus Maertens on 20 Dec 18
     
    Wisdom of crowds under a new perspective: a motivation for the island model?
Luís F. Simões

The AI Revolution: Why Deep Learning Is Suddenly Changing Your Life - 1 views

fortune.com/lligence-deep-machine-learning

AI deeplearning

shared by Luís F. Simões on 30 Sep 16 - No Cached
  • Indeed, corporations just may have reached another inflection point. “In the past,” says Andrew Ng, chief scientist at Baidu Research, “a lot of S&P 500 CEOs wished they had started thinking sooner than they did about their Internet strategy. I think five years from now there will be a number of S&P 500 CEOs that will wish they’d started thinking earlier about their AI strategy.” Even the Internet metaphor doesn’t do justice to what AI with deep learning will mean, in Ng’s view. “AI is the new electricity,” he says. “Just as 100 years ago electricity transformed industry after industry, AI will now do the same.”
  • Luís F. Simões on 30 Sep 16
     
    A good historical overview of the Deep Learning revolution. If you think the quote above is an exageration, here are some fresh news from Microsoft: Internal email: Microsoft forms new 5,000-person AI division
koskons

Interactive and reproducible science papers with jupyter (and mathematica)? - 6 views

www.theatlantic.com/...556676

science

shared by koskons on 12 Mar 19 - No Cached
microno95 liked it
  • darioizzo2 on 12 Mar 19
     
    I agree soooo very much. An increasing number of journal and scientists are finally coming on board with this open science philosophy and I bet we will soon see a radical change of the whole peer review process and publication business
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