The Mode of Computing

The Turing Machine is the paradigmatic case of computing machines, but there are others, such as Artificial Neural Networks, Table Computing, Relational-Indeterminate Computing and diverse forms of analogical computing, each of which based on a particular underlying intuition of the phenomenon of computing. This variety can be captured in terms of system levels, re-interpreting and generalizing Newell's hierarchy, which includes the knowledge level at the top and the symbol level immediately below it. In this re-interpretation the knowledge level consists of human knowledge and the symbol level is generalized into a new level that here is called The Mode of Computing. Natural computing performed by the brains of humans and non-human animals with a developed enough neural system should be understood in terms of a hierarchy of system levels too. By analogy from standard computing machinery there must be a system level above the neural circuitry levels and directly below the knowledge level that is named here The mode of Natural Computing. A central question for Cognition is the characterization of this mode. The Mode of Computing provides a novel perspective on the phenomena of computing, interpreting, the representational and non-representational views of cognition, and consciousness.Comment: 35 pages, 8 figure

Neutron \beta-decay as the origin of IceCube's PeV (anti)neutrinos

Motivated by the indications of a possible deficit of muon tracks in the first three-year equivalent dataset of IceCube we investigate the possibility that the astrophysical (anti)neutrino flux (in the PeV energy range) could originate from \beta-decay of relativistic neutrons. We show that to accommodate IceCube observations it is necessary that only about 1% to 10% of the emitted cosmic rays in the energy decade 10^{8.5} \alt E_{CR}/GeV \alt 10^{9.5}$, yielding antineutrinos on Earth (10^{5.5} \alt E_{\bar \nu}/GeV \alt 10^{6.5}), are observed. Such a strong suppression can be explained assuming magnetic shielding of the secondary protons which diffuse in extragalactic magnetic fields of strength 10 \alt B/nG \alt 100 and coherence length \alt Mpc.Comment: To be published in PR

Multi-stage quantum absorption heat pumps

It is well known that heat pumps, while being all limited by the same basic thermodynamic laws, may find realization on systems as "small" and "quantum" as a three-level maser. In order to quantitatively assess how the performance of these devices scales with their size, we design generalized $N$-dimensional ideal heat pumps by merging $N-2$ elementary three-level stages. We set them to operate in the absorption chiller mode between given hot and cold baths, and study their maximum achievable cooling power and the corresponding efficiency as a function of $N$. While the efficiency at maximum power is roughly size-independent, the power itself slightly increases with the dimension, quickly saturating to a constant. Thus, interestingly, scaling up autonomous quantum heat pumps does not render a significant enhancement beyond the optimal double-stage configuration.Comment: 7 pages, 3 figure

The Pierre Auger Observatory: Science Prospects and Performance at First Light

The Pierre Auger Observatory is a major international effort aiming at high-statistics study of highest energy cosmic rays. A general description of the experimental set-up and overall performance of the detector at first light are presented.Comment: Contribution to the Proceedings of PASCOS '0

Neutrino probe of cosmic ray astrophysics and new physics at sub-fermi distances

We show that if the evolution of cosmic ray sources follows that of active galactic nuclei, the upper limit on the diffuse flux of tau neutrinos from the Pierre Auger Observatory marginally constrains the proton fraction at the end of the energy spectrum. We also discuss prospects to uncover new physics leptophobic interactions using future Auger data.Comment: Talk given at SUSY09, the 17th International Conference on Supersymmetry and the Unification of Fundamental Interactions, Boston 2009. To be published in the Conference Proceeding

Fluid Compressibility Effects on the Dynamic Response of Hydrostatic Journal Bearings

A theoretical analysis for the dynamic performance characteristics of laminar flow, capillar/orifice compensated hydrostatic journal bearings is presented. The analysis considers in detail the effect of fluid compressibility in the bearing recesses. At high frequency excitations beyond a break frequency, the bearing hydrostatic stiffness increases sharply and it is accompanied by a rapid decrease in direct damping. Also, the potential of pneumatic hammer instability (negative damping) at low frequencies is likely to occur in hydrostatic bearing applications handling highly compressible fluids. Useful design criteria to avoid undesirable dynamic operating conditions at low and high frequencies are determined. The effect of fluid recess compressibility is brought into perspective, and found to be of utmost importance on the entire frequency spectrum response and stability characteristics of hydrostatic/hybrid journal bearings