2,305 research outputs found
Renormalization of the asymptotically expanded Yang-Mills spectral action
We study renormalizability aspects of the spectral action for the Yang-Mills
system on a flat 4-dimensional background manifold, focusing on its asymptotic
expansion. Interpreting the latter as a higher-derivative gauge theory, a
power-counting argument shows that it is superrenormalizable. We determine the
counterterms at one-loop using zeta function regularization in a background
field gauge and establish their gauge invariance. Consequently, the
corresponding field theory can be renormalized by a simple shift of the
spectral function appearing in the spectral action.
This manuscript provides more details than the shorter companion paper, where
we have used a (formal) quantum action principle to arrive at gauge invariance
of the counterterms. Here, we give in addition an explicit expression for the
gauge propagator and compare to recent results in the literature.Comment: 28 pages; revised version. To appear in CMP. arXiv admin note:
substantial text overlap with arXiv:1101.480
On dynamically generated parton distribution functions and their properties
The idea of ``dynamically'' generated parton distribution functions, based on
regular initial conditions at low momentum scale, is reanalyzed with particular
emphasize paid to its compatibility with the factorization mechanism. Basic
consequences of this approach are discussed and compared to those of the
conventional approach, employing singular initial distribution functions.Comment: 15 pages, Latex, 5 figures in PS format attache
On the equivalence between the Boltzmann equation and classical field theory at large occupation numbers
We consider a system made up of exictations of a neutral scalar field, \phi,
having a \lambda\phi^4 interaction term. Starting from an ensemble where the
occupation number f is large, but \lambda f is small, we develop a classical
field theory description of the evolution of the system toward equilibrium. A
Boltzmann equation naturally emerges in this description and we show by
explicit calculation that the collision term is the same as that coming from
elastic scattering. This shows the equivalence of a Boltzmann equation
description and a classical field theory description of the same system.Comment: 15 pages, 7 figure
Silicon Drift Detector Readout Electronics for a Compton Camera
A prototype detector for Compton camera imaging is under development. A
monolithic array of 19 channel Silicon drift detector with on-chip electronics
is going to be used as a scatter detector for the prototype system. Custom
designed analog and digital readout electronics for this detector was first
tested by using a single cell Silicon drift detector. This paper describes the
readout architecture and presents the results of the measurement.Comment: 10 pages, 9 figures, submitted to Nucl. Instr. Meth.
cDNA Cloning of Biologically Active Chicken Interleukin-18
By searching a chicken EST database, we identified a cDNA clone that appeared to contain the entire open
reading frame (ORF) of chicken interleukin-18 (ChIL-18). The encoded protein consists of 198 amino acids
and exhibits approximately 30% sequence identity to IL-18 of humans and various others mammals. Sequence
comparisons reveals a putative caspase-1 cleavage site at aspartic acid 29 of the primary translation product,
indicating that mature ChIL-18 might consist of 169 amino acids. Bacterially expressed ChIL-18 in which the
N-terminal 29 amino acids of the putative precursor molecule were replaced by a histidine tag induced the
synthesis of interferon-Îł (IFN-Îł) in cultured primary chicken spleen cells, indicating that the recombinant
protein is biologically active
The cosmic gravitational wave background in a cyclic universe
Inflation predicts a primordial gravitational wave spectrum that is slightly
``red,'' i.e., nearly scale-invariant with slowly increasing power at longer
wavelengths. In this paper, we compute both the amplitude and spectral form of
the primordial tensor spectrum predicted by cyclic/ekpyrotic models. The
spectrum is blue and exponentially suppressed compared to inflation on long
wavelengths. The strongest observational constraint emerges from the
requirement that the energy density in gravitational waves should not exceed
around 10 per cent of the energy density at the time of nucleosynthesis.Comment: 4 pages, 3 figuer
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