603 research outputs found
Natural Inflation From Fermion Loops
``Natural'' inflationary theories are a class of models in which inflation is
driven by a pseudo-Nambu-Goldstone boson. In this paper we consider two models,
one old and one new, in which the potential for inflation is generated by loop
effects from a fermion sector which explicitly breaks a global symmetry.
In both models, we retrieve the ``standard'' natural inflation potential,
, as a limiting case of the exact one-loop potential, but we
carry out a general analysis of the models including the limiting case.
Constraints from the COBE DMR observation and from theoretical consistency are
used to limit the parameters of the models, and successful inflation occurs
without the necessity of fine-tuning the parameters.Comment: (Revised) 15 pages, LaTeX (revTeX), 8 figures in uuencoded PostScript
format. Version accepted for publication in Phys. Rev. D 15. Corrected
definition of power spectrum and added three reference
Inflation at Low Scales: General Analysis and a Detailed Model
Models of inflationary cosmology based on spontaneous symmetry breaking
typically suffer from the shortcoming that the symmetry breaking scale is
driven to nearly the Planck scale by observational constraints. In this paper
we investigate inflationary potentials in a general context, and show that this
difficulty is characteristic only of potentials dominated near their
maxima by terms of order . We find that potentials dominated by terms
of order with \hbox{} can satisfy observational constraints at
an arbitrary symmetry breaking scale. Of particular interest, the spectral
index of density fluctuations is shown to depend only on the order of the
lowest non-vanishing derivative of near the maximum. This result is
illustrated in the context of a specific model, with a broken
symmetry, in which the potential is generated by gauge boson loops.Comment: Submitted to Phys. Rev. D. 32 Pages, REVTeX. No figure
Electron Scattering From High-Momentum Neutrons in Deuterium
We report results from an experiment measuring the semi-inclusive reaction
where the proton is moving at a large angle relative to the
momentum transfer. If we assume that the proton was a spectator to the reaction
taking place on the neutron in deuterium, the initial state of that neutron can
be inferred. This method, known as spectator tagging, can be used to study
electron scattering from high-momentum (off-shell) neutrons in deuterium. The
data were taken with a 5.765 GeV electron beam on a deuterium target in
Jefferson Laboratory's Hall B, using the CLAS detector. A reduced cross section
was extracted for different values of final-state missing mass ,
backward proton momentum and momentum transfer . The data
are compared to a simple PWIA spectator model. A strong enhancement in the data
observed at transverse kinematics is not reproduced by the PWIA model. This
enhancement can likely be associated with the contribution of final state
interactions (FSI) that were not incorporated into the model. A ``bound neutron
structure function'' was extracted as a function of and
the scaling variable at extreme backward kinematics, where effects of
FSI appear to be smaller. For MeV/c, where the neutron is far
off-shell, the model overestimates the value of in the region of
between 0.25 and 0.6. A modification of the bound neutron structure
function is one of possible effects that can cause the observed deviation.Comment: 33 pages RevTeX, 9 figures, to be submitted to Phys. Rev. C. Fixed 1
Referenc
Measurement of the B0-anti-B0-Oscillation Frequency with Inclusive Dilepton Events
The - oscillation frequency has been measured with a sample of
23 million \B\bar B pairs collected with the BABAR detector at the PEP-II
asymmetric B Factory at SLAC. In this sample, we select events in which both B
mesons decay semileptonically and use the charge of the leptons to identify the
flavor of each B meson. A simultaneous fit to the decay time difference
distributions for opposite- and same-sign dilepton events gives ps.Comment: 7 pages, 1 figure, submitted to Physical Review Letter
Human Resource Flexibility as a Mediating Variable Between High Performance Work Systems and Performance
Much of the human resource management literature has demonstrated the impact of high performance
work systems (HPWS) on organizational performance. A new generation of studies is
emerging in this literature that recommends the inclusion of mediating variables between HPWS
and organizational performance. The increasing rate of dynamism in competitive environments
suggests that measures of employee adaptability should be included as a mechanism that may
explain the relevance of HPWS to firm competitiveness. On a sample of 226 Spanish firms, the
studyâs results confirm that HPWS influences performance through its impact on the firmâs
human resource (HR) flexibility
A new scoring system derived from base excess and platelet count at presentation predicts mortality in paediatric meningococcal sepsis
Introduction: The aim of this study was to derive a novel prognostic score for mortality in paediatric meningococcal sepsis (MS) based on readily available laboratory markers.Methods: A multicentre retrospective cohort study for the consortium set and a single centre retrospective study for replication set. The consortium set were 1,073 children (age 1 week to 17.9 years) referred over a 15-year period (1996 to 2011), who had an admission diagnosis of MS, referred to paediatric intensive care units (PICUs) in six different European centres. The consortium set was split into a development set and validation set to derive the score. The replication set were 134 children with MS (age 2 weeks to 16 years) referred over a 4-year period (2007 to 2011) to PICUs via the Children's Acute Transport Service (CATS), London.Results: A total of 85/1,073 (7.9%) children in the consortium set died. A total of 16/134 (11.9%) children in the replication set died. Children dying in the consortium set had significantly lower base excess, C-reactive protein (CRP), platelet and white cell count, more deranged coagulation and higher lactate than survivors. Paediatric risk of mortality (PRISM) score, Glasgow meningococcal septicaemia prognosis score (GMSPS) and Rotterdam score were also higher. Using the consortium set, a new scoring system using base excess and platelet count at presentation, termed the BEP score, was mathematically developed and validated. BEP predicted mortality with high sensitivity and specificity scores (area under the curve (AUC) in the validation set = 0.8
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