1,965 research outputs found
A geometric basis for the standard-model gauge group
A geometric approach to the standard model in terms of the Clifford algebra
Cl_7 is advanced. A key feature of the model is its use of an algebraic spinor
for one generation of leptons and quarks. Spinor transformations separate into
left-sided ("exterior") and right-sided ("interior") types. By definition,
Poincare transformations are exterior ones. We consider all rotations in the
seven-dimensional space that (1) conserve the spacetime components of the
particle and antiparticle currents and (2) do not couple the right-chiral
neutrino. These rotations comprise additional exterior transformations that
commute with the Poincare group and form the group SU(2)_L, interior ones that
constitute SU(3)_C, and a unique group of coupled double-sided rotations with
U(1)_Y symmetry. The spinor mediates a physical coupling of Poincare and
isotopic symmetries within the restrictions of the Coleman--Mandula theorem.
The four extra spacelike dimensions in the model form a basis for the Higgs
isodoublet field, whose symmetry requires the chirality of SU(2). The charge
assignments of both the fundamental fermions and the Higgs boson are produced
exactly.Comment: 17 pages, LaTeX requires iopart. Accepted for publication in J. Phys.
A: Math. Gen. 9 Mar 2001. Typos correcte
The Poincare mass operator in terms of a hyperbolic algebra
The Poincare mass operator can be represented in terms of a Cl(3,0) Clifford
algebra. With this representation the quadratic Dirac equation and the Maxwell
equations can be derived from the same mathematical structure.Comment: 5 pages Latex2
Explicit solutions for relativistic acceleration and rotation
The Lorentz transformations are represented by Einstein velocity addition on
the ball of relativistically admissible velocities. This representation is by
projective maps. The Lie algebra of this representation defines the
relativistic dynamic equation. If we introduce a new dynamic variable, called
symmetric velocity, the above representation becomes a representation by
conformal, instead of projective maps. In this variable, the relativistic
dynamic equation for systems with an invariant plane, becomes a non-linear
analytic equation in one complex variable. We obtain explicit solutions for the
motion of a charge in uniform, mutually perpendicular electric and magnetic
fields. By assuming the Clock Hypothesis and using these solutions, we are able
to describe the space-time transformations between two uniformly accelerated
and rotating systems.Comment: 15 pages 1 figur
Effect of temperature and relative humidity on the development times and survival of Synopsyllus fonquerniei and Xenopsylla cheopis, the flea vectors of plague in Madagascar
Acknowledgements We would like to thank Dr Lila Rahalison and Jocelyn Ratovonjato for their advice and help during the experiment. We are grateful to the staff of the Plague Unit and the Medical Entomology Unit at the Institut Pasteur de Madagascar, particularly Dr Nohal Elissa. Without their expertise this study would not have been possible. Sincere thanks to Mr Tojo Ramihangihajason for his technical assistance. We are indebted to the Institut Pasteur de Madagascar for an internal grant which facilitated additional laboratory research. Two Wellcome Trust fellowships supported ST during this work (081705 and 095171).Peer reviewedPublisher PD
A new view on relativity: Part 2. Relativistic dynamics
The Lorentz transformations are represented on the ball of relativistically
admissible velocities by Einstein velocity addition and rotations. This
representation is by projective maps. The relativistic dynamic equation can be
derived by introducing a new principle which is analogous to the Einstein's
Equivalence Principle, but can be applied for any force. By this principle, the
relativistic dynamic equation is defined by an element of the Lie algebra of
the above representation. If we introduce a new dynamic variable, called
symmetric velocity, the above representation becomes a representation by
conformal, instead of projective maps. In this variable, the relativistic
dynamic equation for systems with an invariant plane, becomes a non-linear
analytic equation in one complex variable. We obtain explicit solutions for the
motion of a charge in uniform, mutually perpendicular electric and magnetic
fields. By the above principle, we show that the relativistic dynamic equation
for the four-velocity leads to an analog of the electromagnetic tensor. This
indicates that force in special relativity is described by a differential
two-form
A human approach to restructuring the education system: why schools in England need social pedagogy
In this article, we contend that the current schoolsâ system in England needs to be carefully reconsidered if we are to offer opportunities for success (in its broadest sense) to those whom our current, technocratic education system excludes. With a focus on social pedagogy and human-centred learning systems, we argue that continued modifications to the existing education system are no longer sufficient and that an ideology overhaul is needed before any significant positive progress can be made. To this end, we suggest various ways that schools might work towards developing healthier and more inclusive communities, built on the key social pedagogical foundations of positive relationships, democracy, inclusion, creativity and pedagogical love. We also make recommendations for an education system in which the teacher, as a highly trained professional, can enjoy a professional autonomy commensurate with their level of qualification. Finally, we dispel some of the myths that have prevented radical, community-focused change to date
Spinors in the hyperbolic algebra
The three-dimensional universal complex Clifford algebra is used to represent
relativistic vectors in terms of paravectors. In analogy to the Hestenes
spacetime approach spinors are introduced in an algebraic form. This removes
the dependance on an explicit matrix representation of the algebra.Comment: 9 pages Latex2
Flock-level risk factors for scrapie in Great Britain: analysis of a 2002 anonymous postal survey
BACKGROUND: In November 2002, an anonymous postal survey of sheep farmers in Great Britain (GB) was conducted to identify factors associated with the flock-level occurrence of scrapie. This survey was undertaken to update an earlier postal survey in 1998, and was the first occasion in which a large-scale postal survey had been repeated. RESULTS: The results of the 2002 survey indicated that scrapie was more likely to occur in certain geographic regions; in purebred compared to commercial flocks; in larger flocks; in flocks which lambed in group pens compared to those which lambed in individual pens; in flocks which always lambed in the same location compared to those which did not; and in farms which kept certain breeds of sheep. In addition to these factors, the likelihood of the disease occurring in homebred animals was higher in flocks which bred a greater proportion of replacement animals or which bought-in lambs. Finally, within-flock transmission following exposure was more likely to occur in hill flocks compared to other farm types; in flocks which bred a greater proportion of replacement animals; and in farms which kept a certain crossbreed of ewe. CONCLUSION: The risk factors identified from the 1998 and 2002 anonymous postal surveys in Great Britain were similar. However, differences between the surveys were identified in the influence of region and of purchasing behaviour on the risk of scrapie. These differences are most likely a consequence of changes in farmer awareness and the impact of the 2001 foot-and-mouth disease epidemic, respectively
A second order differential equation for the relativistic description of electrons and photons
A new relativistic description of quantum electrodynamics is presented.
Guideline of the theory is the Klein-Gordon equation, which is reformulated to
consider spin effects. This is achieved by a representation of relativistic
vectors with a space-time algebra made up of Pauli matrices and hyperbolic
numbers. The algebra is used to construct the differential operator of the
electron as well as the photon wave equation. The properties of free electron
and photon states related to this wave equation are investigated. Interactions
are introduced as usual with the minimal substitution of the momentum
operators. It can be shown that the new wave equation is equivalent to the
quadratic form of the Dirac equation. Furthermore, the Maxwell equations can be
derived from the corresponding wave equation for photons.Comment: Reverted preprint to initial version of 1999. Most of the content has
been published under the new title "Relativistic quantum physics with
hyperbolic numbers". However, interesting parts like the second quantization
of fermion fields within a Klein-Gordon theory, which is only possible with
the help of hyperbolic or bicomplex numbers, dropped out of the revised
versio
Lightlike infinity in GCA models of Spacetime
This paper discusses a 7 dimensional conformal geometric algebra model for
spacetime based on the notion that spacelike and timelike infinities are
distinct. I show how naturally of the dimensions represents the lightlike
infinity and appears redundant in computations, yet usefull in interpretationComment: 12 page
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