18,595 research outputs found
Was SN1997ff at z~1.7 magnified by gravitational lensing?
The quest for the cosmological parameters has come to fruition with the
identification of a number of supernovae at a redshift of . Analyses of
the brightness of these standard candles reveal that the Universe is dominated
by a large cosmological constant. The recent identification of the
SN1997ff in the northern Hubble Deep Field has provided further evidence for
this cosmology. Here we examine the case for gravitational lensing of SN1997ff
due to the presence of galaxies lying along our line of sight. We find that,
while the alignment of SN1997ff with foreground masses was not favorable for it
to be multiply imaged and strongly magnified, two galaxies did lie close enough
to result in significant magnification: for the case where these
elliptical galaxies have velocity dispersion . Given the small
difference between supernova brightnesses in different cosmologies, detailed
modeling of the gravitational lensing properties of the intervening matter is
therefore required before the true cosmological significance of SN1997ff can be
deduced.Comment: 3 pages, 2 figures. Accepted for publication in MNRAS. Missing
reference adde
Lorentz-violating Yang-Mills theory: discussing the Chern-Simons-like term generation
We analyze the Chern-Simons-like term generation in the CPT-odd
Lorentz-violating Yang-Mills theory interacting with fermions. Moreover, we
study the anomalies of this model as well as its quantum stability. The whole
analysis is performed within the algebraic renormalization theory, which is
independent of the renormalization scheme. In addition, all results are valid
to all orders in perturbation theory. We find that the Chern-Simons-like term
is not generated by radiative corrections, just like its Abelian version.
Additionally, the model is also free of gauge anomalies and quantum stable.Comment: 16 pages. No figures. Final version to appear in the Eur.Phys.J.
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