Complexity Digest 2000.20

15-May-2000

  1. Cosmic g-Rays From Intergalactic Structure Formation, Nature
  2. Reduction of Tropical Cloudiness by Soot, Science
  3. Lie Detection And Language Comprehension, Nature
  4. Interacting Molecular Loops in the Mammalian Circadian Clock, Science
  5. Senator Proposes Tax Credit for Telecommuters, NYTimes
  6. The Web Is A Bow Tie, Nature
  7. Digital Mechanics (DM), Sciences of the Interface
  8. Scale Relativity, Fractal Space-Time and Morphogenesis, Sciences of the Interface
  9. Editor's Note

  1. Cosmic g-Rays From Intergalactic Structure Formation, Nature Bookmark and Share

    Excerpt: The Universe is filled with a diffuse background of g -ray radiation1, the origin of which remains one of the unsolved puzzles of cosmology. Less than one-quarter of the g -ray flux can be attributed to unresolved discrete sources, such as active galactic nuclei; the remainder appears to constitute a truly diffuse background. Here we show that the shock waves induced by gravity in the gas of the intergalactic medium, during the formation of large-scale structures like filaments and sheets of galaxies, produce a population of highly relativistic electrons. These electrons scatter a small fraction of the cosmic microwave background photons in the local Universe up to g-ray energies, thereby providing the g -ray background. The predicted diffuse flux agrees with the observed background across more than four orders of magnitude in photon energy, and the model predicts that the g -ray background, though generated locally, is isotropic to better than five per cent on angular scales larger than a degree. Moreover, the agreement between the predicted and observed background fluxes implies a mean cosmological density of baryons that is consistent with Big Bang nucleosynthesis.


  2. Reduction of Tropical Cloudiness by Soot, Science Bookmark and Share

    Abstract: Measurements and models show that enhanced aerosol concentrations can augment cloud albedo not only by increasing total droplet cross-sectional area, but also by reducing precipitation and thereby increasing cloud water content and cloud coverage. Aerosol pollution is expected to exert a net cooling influence on the global climate through these conventional mechanisms. Here, we demonstrate an opposite mechanism through which aerosols can reduce cloud cover and thus significantly offset aerosol-induced radiative cooling at the top of the atmosphere on a regional scale. In model simulations, the daytime clearing of trade cumulus is hastened and intensified by solar heating in dark haze (as found over much of the northern Indian Ocean during the northeast monsoon).


  3. Lie Detection And Language Comprehension, Nature Bookmark and Share

    Excerpt: People are usually no better than chance at detecting lies from a liar's demeanour1, 2, even when clues to deceit are evident from facial expression and tone of voice3. We suspected that people who are unable to understand words (aphasics) may be better at spotting liars, so we tested their performance as lie detectors. We found that aphasics were significantly better at detecting lies about emotion than people with no language impairment, suggesting that loss of language skills may be associated with a superior ability to detect the truth.


  4. Interacting Molecular Loops in the Mammalian Circadian Clock, Science Bookmark and Share

    Abstract: We show that, in the mouse, the core mechanism for the master circadian clock consists of interacting positive and negative transcription and translation feedback loops. Analysis of Clock/Clock mutant mice, homozygous Period2Brdm1 mutants, and Cryptochrome-deficient mice reveals substantially altered Bmal1 rhythms, consistent with a dominant role of PERIOD2 in the positive regulation of the Bmal1 loop. In vitro analysis of CRYPTOCHROME inhibition of CLOCK: BMAL1-mediated transcription shows that the inhibition is through direct protein:protein interactions, independent of the PERIOD and TIMELESS proteins. PERIOD2 is a positive regulator of the Bmal1 loop, and CRYPTOCHROMES are the negative regulators of the Period and Cryptochrome cycles.
    • Interacting Molecular Loops in the Mammalian Circadian Clock, Lauren P. Shearman, Sathyanarayanan Sriram, David R. Weaver, Elizabeth S. Maywood, In s Chaves, Binhai Zheng, Kazuhiko Kume, Cheng Chi Lee, Gijsbertus T. J. van der Horst, Michael H. Hastings, Steven M. Reppert, Science, Volume 288, Number 5468 Issue of 12 May 2000, pp. 1013 - 1019


  5. Senator Proposes Tax Credit for Telecommuters, NYTimes Bookmark and Share

    Excerpts: (...) Sen. Rick Santorum's bill, the Telework Tax Incentive Act, will provide a $500 tax credit for every worker who telecommutes at least 75 days per year. (...)

    Supporters argue that telecommuting reduces traffic congestion, air pollution, gas consumption and dependency on foreign oil. They say the arrangement also benefits working parents, retirees and people who may find it difficult to commute to or work in a traditional office. (...)

    However, companies have shied away from allowing employees to work from home because of traditional business values and the extra cost of building home offices.



  6. The Web Is A Bow Tie, Nature Bookmark and Share

    Excerpt: A study of the web's structure, five times larger than any attempted previously, reveals that it isn't the fully interconnected network that we've been led to believe. The study suggests that the chance of being able to surf between two randomly chosen pages is less than one in four.

    Researchers from three Californian groups - at IBM's Almaden Research Center in San Jose, the Altavista search engine in San Mateo and Compaq Systems Research Center in Palo Alto - have analysed 200 million web pages and 1.5 billion hyperlinks. Their results, which will be presented next week at the World Wide Web 9 Conference in Amsterdam, indicate that the web is made up of four distinct components.



  7. Digital Mechanics (DM), Sciences of the Interface Bookmark and Share

    DM is the name we give to models of fundamental processes in physics that are entirely discrete and finite. We will illustrate the power of DM models by defining a particular model, assigning a small number of properties to the elements of the model, and then deriving a large number of physically correct properties from the model. In particular, we will start with a simple binary 3+1D lattice, where the time dimension has extent 2 and some further complexity. In a sense, this model has 10 dimensions, a 3+1D space time lattice with 6 extra dimensions of time. We then define just one conserved element, B. Bs can occupy sites in the lattice. Each site either is occupied by a B or is empty. Of course, there must be a rule that determines what happens to the Bs. In this model there are 3 fundamental units, B, Length and Time. That's it, BL&T; that's all we put into the model. Here's what we get out: We will show in simple terms exactly how the model represents space, time, energy, momentum, force, charge, temperature, QCD color, why (within the model) particles are colorless, why there are particles and antiparticles, why there are conservation laws, how things move, why there is CPT parity, how angular isotropy arises despite angular anisotropy at the most microscopic level and finally why so many fundamental numbers exist in the standard model.

    It even offers a yet unheard of explanation of Bell's inequality. To understand and absorb all these explanations, the listeners must tolerate an inordinate amount of hand waving and in addition must be able to temporarily suspend many of their most cherished beliefs. If you can force yourself to swallow a byte of the BL&T theory of physics, you might not like it, but it will be good for you.



  8. Scale Relativity, Fractal Space-Time and Morphogenesis, Sciences of the Interface Bookmark and Share

    The theory of scale relativity extends Einstein's principle of relativity to scale transformations of resolutions. It is based on the giving up of the axiom of differentiability of the space-time continuum. Three consequences arise from this withdrawal.

    (i) The geometry of space-time must be fractal, i.e., explicitly resolution-dependent: this allows one to describe a non-differentiable physics in terms of differential equations acting in the scale space. The requirement that these equations satisfy the principle of scale relativity leads to introduce scale laws having a Galilean form (constant fractal dimension), then a Lorentzian one (in which the Planck length-time scale becomes a minimal scale, invariant under dilations), and finally to attempt constructing a generalized scale relativity which includes non-linear scale transformations and scale-motion coupling.

    (ii) The geodesics of a non-differentiable space-time are fractal and in infinite number: this leads one to use a fluid-like description and implies adding new terms in the differential equations of mean motion.

    (iii) Time reversibility is broken at the infinitesimal level: this can be described in terms of a two-validness of the velocity vector, then by jumping to a complex representation. These three effects can be combined to construct a covariant time derivative operator, which transforms the fundamental equations of classical dynamics into a generalized Schrödinger equation. This provides us with a theory of morphogenesis and self-organization, since the solutions of this equations yield probability densities, which are interpreted as a tendency for the system to make structures. Several new theoretical predictions can be made by applying this approach to the equations of motion of test-particles in various gravitational potentials of astrophysical relevance. These predictions are successfully checked by a comparison with observational data on a wide range of scales, ranging from planetary systems to large scale cosmological structures.



  9. Editor's Note Bookmark and Share

    We apologize for the reduced format of this issue. It was compiled while traveling with difficult access to the Internet and additional technical problems.