8,058 research outputs found
Cubulating hyperbolic free-by-cyclic groups: the general case
Let be an automorphism of the finite-rank free group
. Suppose that is word-hyperbolic. Then acts
freely and cocompactly on a CAT(0) cube complex.Comment: 36 pages, 11 figures. Version 2 contains minor corrections. Accepted
to GAF
Trispectrum versus Bispectrum in Single-Field Inflation
In the standard slow-roll inflationary cosmology, quantum fluctuations in a
single field, the inflaton, generate approximately Gaussian primordial density
perturbations. At present, the bispectrum and trispectrum of the density
perturbations have not been observed and the probability distribution for these
perturbations is consistent with Gaussianity. However, Planck satellite data
will bring a new level of precision to bear on this issue, and it is possible
that evidence for non-Gaussian effects in the primordial distribution will be
discovered. One possibility is that a trispectrum will be observed without
evidence for a non-zero bispectrum. It is not difficult for this to occur in
inflationary models where quantum fluctuations in a field other than the
inflaton contribute to the density perturbations. A natural question to ask is
whether such an observation would rule out the standard scenarios. We explore
this issue and find that it is possible to construct single-field models in
which inflaton-generated primordial density perturbations have an observable
trispectrum, but a bispectrum that is too small to be observed by the Planck
satellite. However, an awkward fine tuning seems to be unavoidable.Comment: 15 pages, 3 figures; journal versio
Higgs Properties and Fourth Generation Leptons
It is possible that there are additional vector-like generations where the
quarks have mass terms that do not originate from weak symmetry breaking, but
the leptons only get mass through weak symmetry breaking. We discuss the impact
that the new leptons have on Higgs boson decay branching ratios and on the
range of allowed Higgs masses in such a model (with a single new vector-like
generation). We find that if the fourth generation leptons are too heavy to be
produced in Higgs decay, then the new leptons reduce the branching ratio for h
-> gamma gamma to about 30% of its standard-model value. The dependence of this
branching ratio on the new charged lepton masses is weak. Furthermore the
expected Higgs production rate at the LHC is very near its standard-model value
if the new quarks are much heavier than the weak scale. If the new quarks have
masses near the cutoff for the theory then for cutoffs greater than 10^15 GeV,
the new lepton masses cannot be much heavier than about 100 GeV and the Higgs
mass must have a value around 175 GeV.Comment: 8 pages, 8 figures, published versio
Polychart contour plotter enables data extrapolation from multiple plotting charts
A polychart contour plotter is used to reduce the data from all 19 antenna pattern charts to a one-chart form
Comment on Decay
We calculate the rate for decay using Chiral
Perturbation Theory. This isospin violating process results from -
mixing, and its amplitude is proportional to . Experimental information on the branching
ratio for can provide insight into the pattern of
violation in radiative decays.Comment: 7 pages with 2 figures not included but available upon request,
CALT-68-191
Penicillin: its basic site of action as an inhibitor of a peptide cross-linking reaction in cell wall mucopeptide synthesis.
Chiral Perturbation Theory for , , and
We use heavy vector meson chiral perturbation theory
to predict differential decay distributions for and in the kinematic region where
(here or ) is much smaller than the
chiral symmetry breaking scale. Using the large number of colors limit we also
predict the rate for in this region (now
). Comparing our prediction with experimental data, we determine
one of the coupling constants in the heavy vector meson chiral Lagrangian.Comment: 14 pages, latex 2e. We include the decay of the tau into the omega,
pi minus and the tau neutrino, and extract a value for the coupling constant
g2, using experimental dat
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