8,217 research outputs found
Freire re-viewed
The work of Paulo Freire is associated with themes of oppression and liberation, and his critical pedagogy is visionary in its attempts to bring about social transformation. Freire has created a theory of education that embeds these issues within social relations that center around both ideological and material domination. In this review essay, Sue Jackson explores three books: Freire’s final work Pedagogy of Indignation; Cesar Augusto Rossatto’s Engaging Paulo Freire’s Pedagogy of Possibility, which attempts to engage Freire’s pedagogy of possibility; and C.A. Bowers and Frederique Apffel-Marglin’s edited collection Re-thinking Freire, which asks readers to reconsider Freire’s work in light of globalization and environmental crises. Jackson questions the extent to which Freire’s pedagogical approaches are useful to educators as well as to “the oppressed,” and whether challenges to re-think Freire can lead to new kinds of critical pedagogies
Positivity of Entropy in the Semi-Classical Theory of Black Holes and Radiation
Quantum stress-energy tensors of fields renormalized on a Schwarzschild
background violate the classical energy conditions near the black hole.
Nevertheless, the associated equilibrium thermodynamical entropy by
which such fields augment the usual black hole entropy is found to be positive.
More precisely, the derivative of with respect to radius, at fixed
black hole mass, is found to vanish at the horizon for {\it all} regular
renormalized stress-energy quantum tensors. For the cases of conformal scalar
fields and U(1) gauge fields, the corresponding second derivative is positive,
indicating that has a local minimum there. Explicit calculation
shows that indeed increases monotonically for increasing radius and
is positive. (The same conclusions hold for a massless spin 1/2 field, but the
accuracy of the stress-energy tensor we employ has not been confirmed, in
contrast to the scalar and vector cases). None of these results would hold if
the back-reaction of the radiation on the spacetime geometry were ignored;
consequently, one must regard as arising from both the radiation
fields and their effects on the gravitational field. The back-reaction, no
matter how "small",Comment: 19 pages, RevTe
A Liquid Model Analogue for Black Hole Thermodynamics
We are able to characterize a 2--dimensional classical fluid sharing some of
the same thermodynamic state functions as the Schwarzschild black hole. This
phenomenological correspondence between black holes and fluids is established
by means of the model liquid's pair-correlation function and the two-body
atomic interaction potential. These latter two functions are calculated exactly
in terms of the black hole internal (quasilocal) energy and the isothermal
compressibility. We find the existence of a ``screening" like effect for the
components of the liquid.Comment: 20 pages and 6 Encapsulated PostScript figure
Analytical and Experimental Evaluation of the Heat Transfer Distribution over the Surfaces of Turbine Vanes
Three airfoil data sets were selected for use in evaluating currently available analytical models for predicting airfoil surface heat transfer distributions in a 2-D flow field. Two additional airfoils, representative of highly loaded, low solidity airfoils currently being designed, were selected for cascade testing at simulated engine conditions. Some 2-D analytical methods were examined and a version of the STAN5 boundary layer code was chosen for modification. The final form of the method utilized a time dependent, transonic inviscid cascade code coupled to a modified version of the STAN5 boundary layer code featuring zero order turbulence modeling. The boundary layer code is structured to accommodate a full spectrum of empirical correlations addressing the coupled influences of pressure gradient, airfoil curvature, and free-stream turbulence on airfoil surface heat transfer distribution and boundary layer transitional behavior. Comparison of pedictions made with the model to the data base indicates a significant improvement in predictive capability
Conformal thin-sandwich puncture initial data for boosted black holes
We apply the puncture approach to conformal thin-sandwich black-hole initial
data. We solve numerically the conformal thin-sandwich puncture (CTSP)
equations for a single black hole with non-zero linear momentum. We show that
conformally flat solutions for a boosted black hole have the same maximum
gravitational radiation content as the corresponding Bowen-York solution in the
conformal transverse-traceless decomposition. We find that the physical
properties of these data are independent of the free slicing parameter.Comment: 12 pages, 11 figure
Large Scale Structure Forecast Constraints on Particle Production During Inflation
Bursts of particle production during inflation provide a well-motivated
mechanism for creating bump like features in the primordial power spectrum.
Current data constrains these features to be less than about 5% the size of the
featureless primordial power spectrum at wavenumbers of about 0.1 h Mpc^{-1}.
We forecast that the Planck cosmic microwave background experiment will be able
to strengthen this constraint to the 0.5% level. We also predict that adding
data from a square kilometer array (SKA) galaxy redshift survey would improve
the constraint to about the 0.1% level. For features at larger wave-numbers,
Planck will be limited by Silk damping and foregrounds. While, SKA will be
limited by non-linear effects. We forecast for a Cosmic Inflation Probe (CIP)
galaxy redshift survey, similar constraints can be achieved up to about a
wavenumber of 1 h Mpc^{-1}.Comment: 10 pages. Matches PRD accepted versio
A catalogue of absorption-line systems in QSO spectra
We present a new catalog of absprption-line systems identified in the quasar
spectra. It contains data on 821 QSOs and 8558 absorption systems comprizing
16139 absorption lines with measured redshifts in the QSO spectra. The catalog
includes absorption-line systems consisting of lines of heavy elements, lines
of neutral hydrogen, Lyman limit systems, damped Ly\alpha absorption systems,
and broad absorption-line systems. The catalog is available in electronic form
at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via
http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/412/707 and at
www.ioffe.ru/astro/QC. Using the data of the present catalog we also discuss
redshift distributions of absorption-line systems.Comment: 3 pages with 1 postscript figur
Initial Data and Coordinates for Multiple Black Hole Systems
We present here an alternative approach to data setting for spacetimes with
multiple moving black holes generalizing the Kerr-Schild form for rotating or
non-rotating single black holes to multiple moving holes. Because this scheme
preserves the Kerr-Schild form near the holes, it selects out the behaviour of
null rays near the holes, may simplify horizon tracking, and may prove useful
in computational applications. For computational evolution, a discussion of
coordinates (lapse function and shift vector) is given which preserves some of
the properties of the single-hole Kerr-Schild form
Action Principle for the Generalized Harmonic Formulation of General Relativity
An action principle for the generalized harmonic formulation of general
relativity is presented. The action is a functional of the spacetime metric and
the gauge source vector. An action principle for the Z4 formulation of general
relativity has been proposed recently by Bona, Bona--Casas and Palenzuela
(BBP). The relationship between the generalized harmonic action and the BBP
action is discussed in detail.Comment: This version is contains more thorough presentations and discussions
of the key results. To be published in PRD. (8 pages, no figures
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