1,700 research outputs found
Two-loop Renormalization Group Equations in the Standard Model
Two-loop renormalization group equations in the standard model are
re-calculated. A new coefficient is found in the beta-function of the quartic
coupling and a class of gauge invariants are found to be absent in the
beta-functions of hadronic Yukawa couplings. The two-loop beta-function of the
Higgs mass parameter is presented in complete form.Comment: 4 pages, RevTe
Insensitive Unification of Gauge Couplings
The standard model extended by three vector-like families with masses of
order 1 TeV -- 100 TeV allows for unification of gauge couplings. The values of
gauge couplings at the electroweak scale are highly insensitive to fundamental
parameters. The grand unification scale is large enough to avoid the problem
with fast proton decay. The electroweak minimum of the Higgs potential is
stable.Comment: 4 pages, 2 figures, minor corrections, matches the published versio
Proton lifetime, Yukawa couplings and dynamical SUSY breaking in SU(5) GUT
We study the influence of messenger Yukawa couplings and top, bottom and
Yukawa couplings on the proton lifetime in SU(5) Supersymmetric GUT with
dynamical supersymmetry breaking mechanism due to Dine and Nelson.Comment: 7 pages latex file, 6 ps figures include
Connections between Dynamical and Renormalization Group Techniques in Top Condensation Models
Predictions for the ratio arise in top condensation models from
different methods. One type of prediction stems from Pagels--Stokar relations
based on the use of Ward Identities in the calculation of the \GB decay
constants and expresses in terms of integrals containing the dynamically
generated mass function . Another type of prediction emerges
from the renormalization group equations via infrared quasi--fixed--points of
the running top quark Yukawa coupling. We demonstrate in this paper that in the
limit of a high cutoff these two methods lead to the same predictions for
and in lowest loop order.Comment: Slightly revised version. LaTeX and uuencoded, packed Postscript
figures. The complete paper, including figures, is also available via WWW at
the following http URL
http://www.physik.tu-muenchen.de/tumphy/d/T30d/PAPERS/TUM-HEP-216-95.ps.g
Irregular sloshing cold fronts in the nearby merging groups NGC 7618 and UGC 12491: evidence for Kelvin-Helmholtz instabilities
We present results from two \sim30 ks Chandra observations of the hot
atmospheres of the merging galaxy groups centered around NGC 7618 and UGC
12491. Our images show the presence of arc-like sloshing cold fronts wrapped
around each group center and \sim100 kpc long spiral tails in both groups. Most
interestingly, the cold fronts are highly distorted in both groups, exhibiting
'wings' along the fronts. These features resemble the structures predicted from
non-viscous hydrodynamic simulations of gas sloshing, where Kelvin-Helmholtz
instabilities (KHIs) distort the cold fronts. This is in contrast to the
structure seen in many other sloshing and merger cold fronts, which are smooth
and featureless at the current observational resolution. Both magnetic fields
and viscosity have been invoked to explain the absence of KHIs in these smooth
cold fronts, but the NGC 7618/UGC 12491 pair are two in a growing number of
both sloshing and merger cold fronts that appear distorted. Magnetic fields
and/or viscosity may be able to suppress the growth of KHIs at the cold fronts
in some clusters and groups, but clearly not in all. We propose that the
presence or absence of KHI-distortions in cold fronts can be used as a measure
of the effective viscosity and/or magnetic field strengths in the ICM.Comment: ApJ, accepted. Uses emulateapj styl
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