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Interaction, reaction and performance: The human body tracking project
As a result of new technological advancements in performance practice, I am arguing that new liminal spaces exist where there is a potential for a reconfiguration of creativity and experimentation in performance practice
Natio et gens: Venice biennale 2009
The following is an informal reflection on the changing place of nationality and national consciousness in cultural life with reference to last year’s Biennale. Having drawn tentative inferences regarding the roles of these, we offer a selective review of what appear to us to be the most memorable national representations. These in turn suggest a paradoxical benefit which an awareness of localised histories may bring to artistic production
On one example and one counterexample in counting rational points on graph hypersurfaces
In this paper we present a concrete counterexample to the conjecture of
Kontsevich about the polynomial countability of graph hypersurfaces. In
contrast to this, we show that the "wheel with spokes" graphs are
polynomially countable
Transcendental numbers and the topology of three-loop bubbles
We present a proof that all transcendental numbers that are needed for the
calculation of the master integrals for three-loop vacuum Feynman diagrams can
be obtained by calculating diagrams with an even simpler topology, the topology
of spectacles.Comment: 4 pages in REVTeX, 1 PostScript figure included, submitted to Phys.
Rev. Let
Autofib Redshift Survey: II -- The Evolution of the Galaxy Luminosity Function by Spectral Type
We determine the evolution of the galaxy luminosity function (LF) as a
function of spectral type using the Autofib redshift survey, a compendium of
over 1700 galaxy redshifts in various magnitude-limited samples spanning
b_J=11.5-24.0. To carry out this analysis we have developed a cross-correlation
technique which classifies faint galaxy spectra into one of six types based on
local galaxy templates. Tests and simulations show that this technique yields
classifications correct to within one type for more than 90% of the galaxies in
our sample. We have also developed extensions of the step-wise maximum
likelihood method and the STY parametric method for estimating LFs which are
applicable to recovering an evolving LF from multiple samples. We find that:
(i) The spectra and LF of E/S0 galaxies show no appreciable evolution out to at
least z ~ 0.5. (ii) Early-type spirals show modest evolution, characterised by
a gradual steepening of the faint end of their LF with redshift. (iii) Out to z
~ 0.5, the overall evolution of the galaxy population is dominated by changes
seen in late-type spirals. The characteristic luminosity (L^*) of these
galaxies appears to brighten with redshift and there are signs of strong
density evolution (a rapid increase in \phi^*). These effects appear to be
luminosity dependent so that the LF steepens at higher redshift. These trends
are accompanied by a steep increase in the median [OII] equivalent width,
implying a rapid increase in the star-formation rate with redshift at fixed
luminosity---a given star-formation rate is found at higher redshift in
galaxies of higher luminosity. We find that these conclusions are robust with
respect to spectral classification errors and the luminosity function
estimator.Comment: LaTeX, 22 pages, 22 figure
Using the Hopf Algebra Structure of QFT in Calculations
We employ the recently discovered Hopf algebra structure underlying
perturbative Quantum Field Theory to derive iterated integral representations
for Feynman diagrams. We give two applications: to massless Yukawa theory and
quantum electrodynamics in four dimensions.Comment: 28 p, Revtex, epsf for figures, minor changes, to appear in
Phys.Rev.
The massless two-loop two-point function
We consider the massless two-loop two-point function with arbitrary powers of
the propagators and derive a representation, from which we can obtain the
Laurent expansion to any desired order in the dimensional regularization
parameter eps. As a side product, we show that in the Laurent expansion of the
two-loop integral only rational numbers and multiple zeta values occur. Our
method of calculation obtains the two-loop integral as a convolution product of
two primitive one-loop integrals. We comment on the generalization of this
product structure to higher loop integrals.Comment: 22 pages, revised version, eq. 9, 10 and 53 correcte
Spanning forest polynomials and the transcendental weight of Feynman graphs
We give combinatorial criteria for predicting the transcendental weight of
Feynman integrals of certain graphs in theory. By studying spanning
forest polynomials, we obtain operations on graphs which are weight-preserving,
and a list of subgraphs which induce a drop in the transcendental weight.Comment: 30 page
Free Form Lensing Implications for the Collision of Dark Matter and Gas in the Frontier Fields Cluster MACSJ0416.1-2403
We present a free form mass reconstruction of the massive lensing cluster
MACSJ0416.1-2403 using the latest Hubble Frontier Fields data. Our model
independent method finds that the extended lensing pattern is generated by two
elongated, closely projected clusters of similar mass. Our lens model
identifies new lensed images with which we improve the accuracy of the dark
matter distribution. We find that the bimodal mass distribution is nearly
coincident with the bimodal X-ray emission, but with the two dark matter peaks
lying closer together than the centroids of the X-ray emisison. We show this
can be achieved if the collision has occurred close to the plane and such that
the cores are deflected around each other. The projected mass profiles of both
clusters are well constrained because of the many interior lensed images,
leading to surprisingly flat mass profiles of both components in the region
15-100 kpc. We discuss the extent to which this may be generated by tidal
forces in our dynamical model which are large during an encounter of this type
as the cores "graze" each other. The relative velocity between the two cores is
estimated to be about 1200 km/s and mostly along the line of sight so that our
model is consistent with the relative redshift difference between the two cD
galaxies (dz = 0.04).Comment: 22 pages, 18 figures, 2 table
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