Where is My Attention?

Attention is the key to all learning. Indeed, it is what will save our lives on a daily basis. In all my Communication courses, it is one of the first things I put forward as a question that students may ask of themselves as a check on their “internal considering.” Philosopher/practitioner George Gurdjieff (1866-1949) called the constant rumble in our minds of random condemnations and re-imaginings of past events as “internal considering.” He felt it was detrimental to ourselves and our relationships with others; it is, I maintain, a constant “self considering” that takes us away from the present and “being here now.” So recognizing that we are often not paying attention to what is happening in the space we are in now, with the people we are with now, is the first step in correcting this distracting state of affairs

Non-universal disordered Glauber dynamics

We consider the one-dimensional Glauber dynamics with coupling disorder in terms of bilinear fermion Hamiltonians. Dynamic exponents embodied in the spectrum gap of these latter are evaluated numerically by averaging over both binary and Gaussian disorder realizations. In the first case, these exponents are found to follow the non-universal values of those of plain dimerized chains. In the second situation their values are still non-universal and sub-diffusive below a critical variance above which, however, the relaxation time is suggested to grow as a stretched exponential of the equilibrium correlation length.Comment: 11 pages, 5 figures, brief addition

Complete Positivity for Mixed Unitary Categories

In this article we generalize the \CP^\infty-construction of dagger monoidal categories to mixed unitary categories. Mixed unitary categories provide a setting, which generalizes (compact) dagger monoidal categories and in which one may study quantum processes of arbitrary (infinite) dimensions. We show that the existing results for the \CP^\infty-construction hold in this more general setting. In particular, we generalize the notion of environment structures to mixed unitary categories and show that the \CP^\infty-construction on mixed unitary categories is characterized by this generalized environment structure.Comment: Lots of figure

Filament Hunting: Integrated HI 21cm Emission From Filaments Inferred by Galaxy Surveys

Large scale filaments, with lengths that can reach tens of Mpc, are the most prominent features in the cosmic web. These filaments have only been observed indirectly through the positions of galaxies in large galaxy surveys or through absorption features in the spectra of high redshift sources. In this study we propose to go one step further and directly detect intergalactic medium filaments through their emission in the HI 21cm line. We make use of high resolution cosmological simulations to estimate the intensity of this emission in low redshift filaments and use it to make predictions for the direct detectability of specific filaments previously inferred from galaxy surveys, in particular the Sloan Digital Sky Survey. Given the expected signal of these filaments our study shows that HI emission from large filaments can be observed by current and next generation radio telescopes. We estimate that gas in filaments of length $l \gtrsim$ 15 $h^{-1}$Mpc with relatively small inclinations to the line of sight ($\lesssim 10^\circ$) can be observed in $\sim40-100$ hours with telescopes such as GMRT or EVLA, potentially providing large improvements over our knowledge of the astrophysical properties of these filaments. Due to their large field of view and sufficiently long integration times, upcoming HI surveys with the Apertif and ASKAP instruments will be able to detect large filaments independently of their orientation and curvature. Furthermore, our estimates indicate that a more powerful future radio telescope like SKA-2 can be used to map most of these filaments, which will allow them to be used as a strong cosmological probe.Comment: 16 pages, 11 figures, Accepted for publication in MNRA

Quasi integral of motion for axisymmetric potentials

We present an estimate of the third integral of motion for axisymmetric three-dimensional potentials. This estimate is based on a Staeckel approximation and is explicitly written as a function of the potential. We tested this scheme for the Besancon Galactic model and two other disc-halo models and find that orbits of disc stars have an accurately conserved third quasi integral. The accuracy ranges from of 0.1% to 1% for heights varying from z = 0~kpc to z= 6 kpc and Galactocentric radii R from 5 to 15kpc. We also tested the usefulness of this quasi integral in analytic distribution functions of disc stellar populations: we show that the distribution function remains approximately stationary and that it allows to recover the potential and forces by applying Jeans equations to its moments.Comment: 9 pages, 9 figures, accepted for publication in Astron. and Astrophy