1,637 research outputs found
Big brother is watching - using digital disease surveillance tools for near real-time forecasting
Abstract for the International Journal of Infectious Diseases 79 (S1) (2019).https://www.ijidonline.com/article/S1201-9712(18)34659-9/abstractPublished versio
Quaternionic and Octonionic Spinors. A Classification
Quaternionic and octonionic realizations of Clifford algebras and spinors are
classified and explicitly constructed in terms of recursive formulas. The most
general free dynamics in arbitrary signature space-times for both quaternionic
and octonionic spinors is presented. In the octonionic case we further provide
a systematic list of results and tables expressing, e.g., the relations of the
octonionic Clifford algebras with the cosets over the Lorentz algebras,
the identities satisfied by the higher-rank antisymmetric octonionic tensors
and so on. Applications of these results range from the classification of
octonionic generalized supersymmetries, the construction of octonionic
superstrings, as well as the investigations concerning the recently discovered
octonionic -superalgebra and its superconformal extension.Comment: 24 pages, LaTe
Classification of irreps and invariants of the N-extended Supersymmetric Quantum Mechanics
We present an algorithmic classification of the irreps of the -extended
one-dimensional supersymmetry algebra linearly realized on a finite number of
fields. Our work is based on the 1-to-1 \cite{pt} correspondence between
Weyl-type Clifford algebras (whose irreps are fully classified) and classes of
irreps of the -extended 1D supersymmetry. The complete classification of
irreps is presented up to . The fields of an irrep are accommodated
in different spin states. N=10 is the minimal value admitting length
irreps. The classification of length-4 irreps of the N=12 and {\em real} N=11
extended supersymmetries is also explicitly presented.\par Tensoring irreps
allows us to systematically construct manifestly (-extended) supersymmetric
multi-linear invariants {\em without} introducing a superspace formalism.
Multi-linear invariants can be constructed both for {\em unconstrained} and
{\em multi-linearly constrained} fields. A whole class of off-shell invariant
actions are produced in association with each irreducible representation. The
explicit example of the N=8 off-shell action of the multiplet is
presented.\par Tensoring zero-energy irreps leads us to the notion of the {\em
fusion algebra} of the 1D -extended supersymmetric vacua.Comment: Final version to appear in JHEP. 52 pages. The part with the complete
classification of irreps (and the explicit presentation of length-4 irreps of
N=9,10,11,12 and N=10 length-5 irreps) is unchanged. An extra section has
been added with an entire class of off-shell invariant actions for arbitrary
values N of the 1D extended supersymmetry. A non-trivial N=8 off-shell action
for the (1,8,7) multiplet has been constructed as an example. It is obtained
in terms of the octonionic structure constant
Hermitian versus holomorphic complex and quaternionic generalized supersymmetries of the M-theory. A classification
Relying upon the division-algebra classification of Clifford algebras and
spinors, a classification of generalized supersymmetries (or, with a slight
abuse of language,"generalized supertranslations") is provided. In each given
space-time the maximal, saturated, generalized supersymmetry, compatible with
the division-algebra constraint that can be consistently imposed on spinors and
on superalgebra generators, is furnished. Constraining the superalgebra
generators in both the complex and the quaternionic cases gives rise to the two
classes of constrained hermitian and holomorphic generalized supersymmetries.
In the complex case these two classes of generalized supersymmetries can be
regarded as complementary. The quaternionic holomorphic supersymmetry only
exists in certain space-time dimensions and can admit at most a single bosonic
scalar central charge.
The results here presented pave the way for a better understanding of the
various algebra-type of structures which can be introduced in different
space-time signatures and in association with different division algebras, as
well as their mutual relations. In a previous work, e.g., the introduction of a
complex holomorphic generalized supersymmetry was shown to be necessary in
order to perform the analytic continuation of the standard -theory to the
11-dimensional Euclidean space. As an application of the present results, it is
shown that the above algebra also admits a 12-dimensional, Euclidean,
-algebra presentation.Comment: 25 pages, LaTe
Satellite laser ranging work at the Goddard Space Flight Center
Laser ranging systems, their range and accuracy capabilities, and planned improvements for future systems are discussed, the systems include one fixed and two mobile lasers ranging systems. They have demonstrated better than 10 cm accuracy both on a carefully surveyed ground range and in regular satellite ranging operations. They are capable of ranging to all currently launched retroreflector equipped satellites with the exception of Timation III. A third mobile system is discussed which will be accurate to better than 5 cm and will be capable of ranging to distant satellites such as Timation III and LAGEOS
Supersymmetric Rotating Black Holes and Causality Violation
The geodesics of the rotating extreme black hole in five spacetime dimensions
found by Breckenridge, Myers, Peet and Vafa are Liouville integrable and may be
integrated by additively separating the Hamilton-Jacobi equation. This allows
us to obtain the St\"ackel-Killing tensor. We use these facts to give the
maximal analytic extension of the spacetime and discuss some aspects of its
causal structure. In particular, we exhibit a `repulson'-like behaviour
occuring when there are naked closed timelike curves. In this case we find that
the spacetime is geodesically complete (with respect to causal geodesics) and
free of singularities. When a partial Cauchy surface exists, we show, by
solving the Klein-Gordon equation, that the absorption cross-section for
massless waves at small frequencies is given by the area of the hole. At high
frequencies a dependence on the angular quantum numbers of the wave develops.
We comment on some aspects of `inertial time travel' and argue that such time
machines cannot be constructed by spinning up a black hole with no naked closed
timelike curves.Comment: 36 pages,LaTeX,8 figures;added 1 reference and a few comments;
formula (2.6) corrected; a few changes to section
On Supergroups with Odd Clifford Parameters and Supersymmetry with Modified Leibniz Rule
We investigate supergroups with Grassmann parameters replaced by odd Clifford
parameters. The connection with non-anticommutative supersymmetry is discussed.
A Berezin-like calculus for odd Clifford variables is introduced. Fermionic
covariant derivatives for supergroups with odd Clifford variables are derived.
Applications to supersymmetric quantum mechanics are made. Deformations of the
original supersymmetric theories are encountered when the fermionic covariant
derivatives do not obey the graded Leibniz property. The simplest non-trivial
example is given by the N=2 SQM with a real multiplet and a cubic
potential. The action is real. Depending on the overall sign ("Euclidean" or
"Lorentzian") of the deformation, a Bender-Boettcher pseudo-hermitian
hamiltonian is encountered when solving the equation of motion of the auxiliary
field. A possible connection of our framework with the Drinfeld twist
deformation of supersymmetry is pointed out.Comment: Final version to be published in Int. J. Mod. Phys. A; 20 page
The emergence of enterovirus D68 in England in autumn 2014 and the necessity for reinforcing enterovirus respiratory screening.
In autumn 2014, enterovirus D68 (EV-D68) cases presenting with severe respiratory or neurological disease were described in countries worldwide. To describe the epidemiology and virological characteristics of EV-D68 in England, we collected clinical information on laboratory-confirmed EV-D68 cases detected in secondary care (hospitals), between September 2014 and January 2015. In primary care (general practitioners), respiratory swabs collected (September 2013-January 2015) from patients presenting with influenza-like illness were tested for EV-D68. In secondary care 55 EV-D68 cases were detected. Among those, 45 cases had clinical information available and 89% (40/45) presented with severe respiratory symptoms. Detection of EV-D68 among patients in primary care increased from 0.4% (4/1074; 95% CI 0.1-1.0) (September 2013-January 2014) to 0.8% (11/1359; 95% CI 0.4-1.5) (September 2014-January 2015). Characterization of EV-D68 strains circulating in England since 2012 and up to winter 2014/2015 indicated that those strains were genetically similar to those detected in 2014 in USA. We recommend reinforcing enterovirus surveillance through screening respiratory samples of suspected cases
Trauma histories of men and women in residential drug treatment: The Scottish evidence
This article focuses on self-reported child neglect and abuse in residential drug treatment drawing on data from clients in Scotland collected 1996-1999. It notes the lack of adoption of regular screening using validated tools of childhood trauma in men and women. The authorsâ findings suggest that the prevalence of childhood abuse histories are higher in female drug users than male drug users but recognises that even with standardised tools there is a wealth of diverse categories of severity of abuse that warn against broad treatment plans for âthe traumatisedâ
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