749 research outputs found
Implications of quaternionic dark matter
Taking the complex nature of quantum mechanics which we observe today as a
low energy effect of a broken quaternionic theory we explore the possibility
that dark matter arises as a consequence of this underlying quaternionic
structure to our universe. We introduce a low energy, effective, Lagrangian
which incorporates the remnants of a local quaternionic algebra, investigate
the stellar production of the resultant exotic bosons and explore the possible
low energy consequences of our remnant extended Hilbert space.Comment: 14 pages, RevTeX, no figure
Experimental status of quaternionic quantum mechanics
Analysis of the logical foundations of quantum mechanics indicates the
possibility of constructing a theory using quaternionic Hilbert spaces. Whether
this mathematical structure reflects reality is a matter for experiment to
decide. We review the only direct search for quaternionic quantum mechanics yet
carried out and outline a recent proposal by the present authors to look for
quaternionic effects in correlated multi-particle systems. We set out how such
experiments might distinguish between the several quaternionic models proposed
in the literature.Comment: 8 pages, no figures, revtex. An update of paper appearing in journal
reference given below, with minor amendments and latest additional reference
Comments on No-Hair Theorems and Stabilty of Blackholes
In the light of recent blackhole solutions inspired by string theory, we
review some old statements on field theoretic hair on blackholes. We also
discuss some stability issues. In particular we argue that the two dimensional
string blackhole solution is semi-classically stable while the naked
singularity is unstable to tachyon fluctuations. Finally we comment on the
relation between the linear dilaton theory and the blackhole solution.Comment: 14 page
The effect of spontaneous collapses on neutrino oscillations
We compute the effect of collapse models on neutrino oscillations. The effect
of the collapse is to modify the evolution of the `spatial' part of the wave
function, which indirectly amounts to a change on the flavor components. In
many respects, this phenomenon is similar to neutrino propagation through
matter. For the analysis we use the mass proportional CSL model, and perform
the calculation to second order perturbation theory. As we will show, the CSL
prediction is very small - mainly due to the very small mass of neutrinos - and
practically undetectable.Comment: 24 pages, RevTeX. Updated versio
Parity violating pion electroproduction off the nucleon
Parity violating (PV) contributions due to interference between and
exchange are calculated for pion electroproduction off the nucleon. A
phenomenological model with effective Lagrangians is used to determine the
resulting asymmetry for the energy region between threshold and
resonance. The resonance is treated as a Rarita-Schwinger field with
phenomenological transition currents. The background contributions
are given by the usual Born terms using the pseudovector Lagrangian.
Numerical results for the asymmetry are presented.Comment: 17 pages, RevTeX, 6 figures (in separate file figs.uu), uses epsf,
accepted for publication in Z. Phys.
Insights into the effects of mucosal epithelial and innate immune dysfunction in older people on host interactions with Streptococcus pneumoniae
In humans, nasopharyngeal carriage of Streptococcus pneumoniae is common and although primarily asymptomatic, is a pre-requisite for pneumonia and invasive pneumococcal disease (IPD). Together, these kill over 500,000 people over the age of 70 years worldwide every year. Pneumococcal conjugate vaccines have been largely successful in reducing IPD in young children and have had considerable indirect impact in protection of older people in industrialized country settings (herd immunity). However, serotype replacement continues to threaten vulnerable populations, particularly older people in whom direct vaccine efficacy is reduced. The early control of pneumococcal colonization at the mucosal surface is mediated through a complex array of epithelial and innate immune cell interactions. Older people often display a state of chronic inflammation, which is associated with an increased mortality risk and has been termed 'Inflammageing'. In this review, we discuss the contribution of an altered microbiome, the impact of inflammageing on human epithelial and innate immunity to S. pneumoniae, and how the resulting dysregulation may affect the outcome of pneumococcal infection in older individuals. We describe the impact of the pneumococcal vaccine and highlight potential research approaches which may improve our understanding of respiratory mucosal immunity during pneumococcal colonization in older individuals.Host-parasite interactio
Softly broken supersymmetric Yang-Mills theories: Renormalization and non-renormalization theorems
We present a minimal version for the renormalization of softly broken
Super-Yang-Mills theories using the extended model with a local gauge coupling.
It is shown that the non-renormalization theorems of the case with unbroken
supersymmetry are valid without modifications and that the renormalization of
soft-breaking parameters is completely governed by the renormalization of the
supersymmetric parameters. The symmetry identities in the present context are
peculiar, since the extended model contains two anomalies: the Adler-Bardeen
anomaly of the axial current and an anomaly of supersymmetry in the presence of
the local gauge coupling. From the anomalous symmetries we derive the exact
all-order expressions for the beta functions of the gauge coupling and of the
soft-breaking parameters. They generalize earlier results to arbitrary
normalization conditions and imply the NSVZ expressions for a specific
normalization condition on the coupling.Comment: 24 pages, LaTeX, v2: one reference adde
Neutrino oscillations in a model with a source and detector
We study the oscillations of neutrinos in a model in which the neutrino is
coupled to a localized, idealized source and detector. By varying the spatial
and temporal resolution of the source and detector we are able to model the
full range of source and detector types ranging from coherent to incoherent. We
find that this approach is useful in understanding the interface between the
Quantum Mechanical nature of neutrino oscillations on the one hand and the
production and detection systems on the other hand. This method can easily be
extended to study the oscillations of other particles such as the neutral K and
B mesons. We find that this approach gives a reliable way to treat the various
ambiguities which arise when one examines the oscillations from a wave packet
point of view. We demonstrate that the conventional oscillation formula is
correct in the relativistic limit and that several recent claims of an extra
factor of 2 in the oscillation length are incorrect. We also demonstrate
explicitly that the oscillations of neutrinos which have separated spatially
may be "revived" by a long coherent measurement.Comment: 30 pages, 6 figures, Late
Meson Screening Mass in a Strongly Coupled Pion Superfluid
We calculate the meson screening mass in a pion superfluid in the framework
of Nambu--Jona-Lasinio model. The minimum of the attractive quark potential is
always located at the phase boundary of pion superfluid. Different from the
temperature and baryon density effect, the potential at finite isospin density
can not be efficiently suppressed and the matter is always in a strongly
coupled phase due to the Goldstone mode in the pion superfluid.Comment: 8 pages, 7 figures(Accepted by European Physical Journal C
QCD Corrections to QED Vacuum Polarization
We compute QCD corrections to QED calculations for vacuum polarization in
background magnetic fields. Formally, the diagram for virtual loops
is identical to the one for virtual loops. However due to
confinement, or to the growth of as decreases, a direct
calculation of the diagram is not allowed. At large we consider the
virtual diagram, in the intermediate region we discuss the role of
the contribution of quark condensates \left and at the
low-energy limit we consider the , as well as charged pion
loops. Although these effects seem to be out of the measurement accuracy of
photon-photon laboratory experiments they may be relevant for -ray
burst propagation. In particular, for emissions from the center of the galaxy
(8.5 kpc), we show that the mixing between the neutral pseudo-scalar pion
and photons renders a deviation from the power-law spectrum in the
range. As for scalar quark condensates \left and
virtual loops are relevant only for very high radiation density
and very strong magnetic fields of order .Comment: 15 pages, 4 figures; Final versio
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