the physics arXiv blog

Category: Calculatin’

  • Quantum test found for mathematical undecidability

    It was the physicist Eugene Wigner who discussed the “unreasonable effectiveness of mathematics” in a now famous paper that examined the profound link between mathematics and physics. Today, Anton Zeilinger and pals at the University of Vienna in Austria reveal this link at its deepest. Their experiment involves the issue of mathematical decidability. First, some…

  • A clue in the puzzle of perfect synchronization in the brain

    “Two identical chaotic systems starting from almost identical initial states, end in completely uncorrelated trajectories. On the other hand, chaotic systems which are mutually coupled by some of their internal variables often synchronize to a collective dynamical behavior,” write Meital Zigzag at Bar-Ilan University in Israel and colleagues o the arXiv today. And perhaps the…

  • Triggering a phase change in wealth distribution

    Wealth distribution in the western world follows a curious pattern. For 95 per cent of the population, it follows a Boltzmann Gibbs distribution, in other words a straight line on a log-linear scale. For the top 5 per cent, however, wealth allocation follows a Pareto distribution, a straight line on a log-log scale, which is…

  • Predicting the popularity of online content

    The page views for entries on this site in the last week range from more than 17,000 thousand for this story to around 100 for this one. That just goes to show that when you post a blog entry and there’s no way of knowing how popular it will become. Right? Not according to Gabor…

  • Breakthrough calculations on the capacity of a steganographic channel

    Steganography is the art of hiding a message in such a way that only the sender and receiver realise it is there. (By contrast, cryptography disguises the content of a message but makes no attempt to hide it.) The central problem for steganographers is how much data can be hidden without being detected. But the…

  • The trouble with traffic at intersections

    These rather beautiful graphs are space-time plots of vehicles approaching, entering and then leaving an intersection controlled by traffic lights. The plots were calculated using cellular automata to model the behavior of the vehicles.  Here the upper plot shows the pattern of traffic at a traffic lights with a fixed schedule. The lower figures shows…

  • Forget black holes, could the LHC trigger a “Bose supernova”?

    The fellas at CERN have gone to great lengths to reassure us all that they won’t destroy the planet (who says physicists are cold hearted?). The worry was that the collision of particles at the LHC’s high energies could create a black hole that would swallow the planet. We appear to be safe on that…

  • Why spontaneous traffic jams are like detonation waves

    We’re all familiar with phantom jams, traffic blockages that arise with no apparent cause and that melt away for no discernible reason. Today Ruben Rosales and pals at MIT and the University of Alberta in Canada coin a new term for the waves that cause these hold ups: they call them jamitons. And jamitons turn…

  • Flyby anomalies explained by special relativity

    On 23 January 1998, when NASA’s Near spacecraft swung past Earth on a routine flyby towards more interesting lands, a curious thing happened to its speed. It jumped by 13 mm/s. This wasn’t the first time such an effect had been seen. Engineers saw similar jumps in speed during the Earth flybys of Galileo (in…

  • How big is a city?

    That’s not as silly a question as it sounds. Defining the size of a city is tricky task that has major economic implications: how much should you invest in a city if you don’t know how many people live and work there? The standard definition is the Metropolitan Statistical Area, which attempts to capture the…