629 research outputs found
Interplay between perturbative and non-perturbative effects in the stealthy Higgs model
We study corrections to electroweak precision variables in a model with
strongly interacting singlet Higgs particles.Comment: 31 pages, Latex, 11 figure
Density-metric unimodular gravity:vacuum spherical symmetry
We analyze an alternative theory of gravity characterized by metrics that are
tensor density of rank(0,2)and weight-1/2.The metric compatibility condition is
supposed to hold. The simplest expression for the action of gravitational field
is used.Taking the metric and trace of connections as dynamical variables,the
field equations in the absence of matter and other kinds of sources are
derived.The solutions of these equations are obtained for the case of vacuum
static spherical symmetric spacetime.The null geodesics and advance of
perihelion of ellipes are discussed.We confirm a subclass of solutions is
regular for r>0 and there is no event horizon while it is singular at r=0.Comment: 15 pages,no,figures,typos corrected,new section added,published
versio
Gravitational anomaly and fundamental forces
I present an argument, based on the topology of the universe, why there are
three generations of fermions. The argument implies a preferred gauge group of
SU(5), but with SO(10) representations of the fermions. The breaking pattern
SU(5) to SU(3)xSU(2)xU(1) is preferred over the pattern SU(5) to SU(4)xU(1). On
the basis of the argument one expects an asymmetry in the early universe
microwave data, which might have been detected already.Comment: Contribution to the 2nd School and Workshop on Quantum Gravity and
Quantum Geometry. Corfu, september 13-20 2009. 10 page
Resonance in Strong WW Rescattering in Massive SU(2) Gauge Theory
We investigate the effects of WW rescattering through strong anomalous
four-vector boson couplings. In the I=1, J=1 channel, we find a resonance with
a mass of approximately 200 GeV and a width of less than 12 GeV. In an
application to pion physics we find a small correction to the KSRF relation.Comment: 21 pages, extended discussion, some minor change
Heavy Fermion Screening Effects and Gauge Invariance
We show that the naively expected large virtual heavy fermion effects in low
energy processes may be screened if the process under consideration contains
external gauge bosons constrained by gauge invariance. We illustrate this by a
typical example of the process . Phenomenological
implications are also briefly indicated.Comment: a miss-print fixed, 7 pages, LaTex, no figure
Mini-Proceedings of the 15th meeting of the Working Group on Rad. Corrections and MC Generators for Low Energies
The mini-proceedings of the 15th Meeting of the "Working Group on Rad.
Corrections and MC Generators for Low Energies" held in Mainz on April 11,
2014, are presented. These meetings, started in 2006, have as aim to bring
together experimentalists and theorists working in the fields of meson
transition form factors, hadronic contributions to and the
effective fine structure constant, and development of Monte Carlo generators
and Radiative Corrections for precision e+e- and tau physics.Comment: 21 pages, 7 contributions. Editors: S. E. Mueller and G. Venanzon
A refinement of the Gribov-Zwanziger approach in the Landau gauge: infrared propagators in harmony with the lattice results
Recent lattice data have reported an infrared suppressed, positivity
violating gluon propagator which is nonvanishing at zero momentum and a ghost
propagator which is no longer enhanced. This paper discusses how to obtain
analytical results which are in qualitative agreement with these lattice data
within the Gribov-Zwanziger framework. This framework allows one to take into
account effects related to the existence of gauge copies, by restricting the
domain of integration in the path integral to the Gribov region. We elaborate
to great extent on a previous short paper by presenting additional results,
also confirmed by the numerical simulations. A detailed discussion on the soft
breaking of the BRST symmetry arising in the Gribov-Zwanziger approach is
provided.Comment: 38 pages, 9 figures, the content of section V has been extended and
adapte
Single-Top-Quark Production via W-Gluon Fusion at Next-to-Leading Order
Single-top-quark production via W-gluon fusion at hadron colliders provides
an opportunity to directly probe the charged-current interaction of the top
quark. We calculate the next-to-leading-order corrections to this process at
the Fermilab Tevatron, the CERN Large Hadron Collider, and DESY HERA. Using a
b-quark distribution function to sum collinear logarithms, we show that there
are two independent corrections, of order 1/[ln(m_t^2/m_b^2)] and alpha_s. This
observation is generic to processes involving a perturbatively derived
heavy-quark distribution function at an energy scale large compared with the
heavy-quark mass.Comment: 19 pages, 9 figures, small update to Phys. Rev. D versio
Incomplete quality of life data in lung transplant research: comparing cross sectional, repeated measures ANOVA, and multi-level analysis
BACKGROUND: In longitudinal studies on Health Related Quality of Life (HRQL) it frequently occurs that patients have one or more missing forms, which may cause bias, and reduce the sample size. Aims of the present study were to address the problem of missing data in the field of lung transplantation (LgTX) and HRQL, to compare results obtained with different methods of analysis, and to show the value of each type of statistical method used to summarize data. METHODS: Results from cross-sectional analysis, repeated measures on complete cases (ANOVA), and a multi-level analysis were compared. The scores on the dimension 'energy' of the Nottingham Health Profile (NHP) after transplantation were used to illustrate the differences between methods. RESULTS: Compared to repeated measures ANOVA, the cross-sectional and multi-level analysis included more patients, and allowed for a longer period of follow-up. In contrast to the cross sectional analyses, in the complete case analysis, and the multi-level analysis, the correlation between different time points was taken into account. Patterns over time of the three methods were comparable. In general, results from repeated measures ANOVA showed the most favorable energy scores, and results from the multi-level analysis the least favorable. Due to the separate subgroups per time point in the cross-sectional analysis, and the relatively small number of patients in the repeated measures ANOVA, inclusion of predictors was only possible in the multi-level analysis. CONCLUSION: Results obtained with the various methods of analysis differed, indicating some reduction of bias took place. Multi-level analysis is a useful approach to study changes over time in a data set where missing data, to reduce bias, make efficient use of available data, and to include predictors, in studies concerning the effects of LgTX on HRQL
- …