71 research outputs found
Minimal massive 3D gravity unitarity redux
A geometrical analysis of the bulk and anti-de Sitter boundary unitarity conditions
of 3D āMinimal Massive Gravityā (MMG) (which evades the ābulk/boundary clashā of
Topologically Massive Gravity) is used to extend and simplify previous results, showing
that unitarity selects, up to equivalence, a connected region in parameter space. We
also initiate the study of flat-space holography for MMG.A.S.A. and P.K.T. acknowledge support from the UK Science and Technology Facilities
Council (grant ST/L000385/1). A.S.A. also acknowledges support from Clare Hall
College, Cambridge, and from the Cambridge Trust. We are grateful to Eduardo Casali,
Elias Kiritsis and Alasdair Routh for helpful discussions, and to Eric Bergshoeff and
Wout Merbis for helpful correspondence.This is the final version of the article. It was first published by IOP at https://camacuk.zendesk.com/agent/tickets/626
Twistor description of spinning particles in AdS
The two-twistor formulation of particle mechanics in D-dimensional anti-de Sitter space for D=4,5,7, which linearises invariance
under the AdS isometry group Sp(4;K) for K=R,C,H,, is generalized to the massless N-extended ``spinning particle''. The twistor
variables are gauge invariant with respect to the initial N local worldline supersymmetries; this simplifies aspects of the quantum theory such as
implications of global gauge anomalies. We also give details of the two-supertwistor form of the superparticle, in particular the massive
superparticle on AdS5
Worldline CPT and massless supermultiplets
The action for a massless particle in 4D Minkowski spaceātime has a worldline-time reversing symmetry corresponding to CPT invariance of the quantum theory. The analogous symmetry of the -extended superparticle is shown to be anomalous when is odd; in the supertwistor formalism this is because a CPT-violating worldline-ChernāSimons term is needed to preserve the chiral gauge invariance. This accords with the fact that no massless =1 super-PoincarĆ© irrep is CPT-self-conjugate. There is a CPT self-conjugate supermultiplet when is even, but it has states when is odd (e.g. the =2 hypermultiplet) in contrast to just when is even (e.g. the =4 Maxwell supermultiplet). This is shown to follow from a Kramers degeneracy of the superparticle state space when is odd.A.S. Arvanitakis and P. K. Townsend acknowledge support from the UK Science and Technology Facilities Council (grant ST/L000385/1).A.S. Arvanitakis also acknowledges support from Clare Hall College, Cambridge, and from the Cambridge Trust
Pauli-Lubanski, supertwistors, and the superspinning particle
We present a novel construction of the super-Pauli-Lubanski pseudo-vector for 4D supersymmetry and show how it arises naturally from the spin-shell constraints in the supertwistor formulation of superparticle dynamics. We illustrate this result in the context of a simple classical action for a āsuperspinning particleā of superspin 1/2. We then use an Sl(2;K)-spinor formalism for K=ā,ā,ā to unify our 4D results with previous results for 3D and 6D
Anti-de Sitter Particles and Manifest (Super)Isometries.
Starting from the classical action for a spin-zero particle in a D-dimensional anti-de Sitter (AdS) spacetime, we recover the Breitenlohner-Freedman bound by quantization. For D=4, 5, 7 and using an Sl(2;K) spinor notation for K=R,C,H, we find a bitwistor form of the action for which the AdS isometry group is linearly realized, although only for zero mass when D=4, 7 in agreement with previous constructions. For zero mass and D=4 the conformal isometry group is linearly realized. We extend these results to the superparticle in the maximally supersymmetric "AdSĆS" string or M-theory vacua, showing that quantization yields a 128+128 component supermultiplet. We also extend them to the null string.We acknowledge support from the UK Science and Technology Facilities Council (Grants No. ST/L000385/1 and No. ST/M50340X/1). A.āS.āA. also acknowledges support from the INFN, from Clare Hall College Cambridge, from DAMTP, from the Cambridge Philosophical Society, and from the Cambridge Trust
Homotopy transfer and effective field theory I: tree-level
We use the dictionary between general field theories and strongly homotopyalgebras to provide an algebraic formulation of the procedure of integratingout of degrees of freedom in terms of homotopy transfer. This includes moregeneral effective theories in which some massive modes are kept while othermodes of a comparable mass scale are integrated out, as first explored by Senin the context of closed string field theory. We treatLā-algebras both in termsof a nilpotent coderivation and, on the dual space, in terms of a nilpotentderivation (corresponding to the BRST charge of the field theory) and provideexplicit formulas for homotopy transfer. These are then shown to govern theintegrating out of degrees of freedom at tree level, while the generalization toloop level will be explored in a sequel to this paper
The benefits and risks of bacille Calmette-GuƩrin vaccination among infants at high risk for both tuberculosis and severe combined immunodeficiency: assessment by Markov model
BACKGROUND: Bacille Calmette-GuĆ©rin (BCG) vaccine is given to Canadian Aboriginal neonates in selected communities. Severe reactions and deaths associated with BCG have been reported among infants born with immunodeficiency syndromes. The main objective of this study was to estimate threshold values for severe combined immunodeficiency (SCID) incidence, above which BCG is associated with greater risk than benefit. METHODS: A Markov model was developed to simulate the natural histories of tuberculosis (TB) and SCID in children from birth to 14 years. The annual risk of tuberculous infection (ARI) and SCID incidence were varied in analyses. The model compared a scenario of no vaccination to intervention with BCG. Appropriate variability and uncertainty analyses were conducted. Outcomes included TB incidence and quality-adjusted life years (QALYs). RESULTS: In sensitivity analyses, QALYs were lower among vaccinated infants if the ARI was 0.1% and the rate of SCID was higher than 4.2 per 100,000. Assuming an ARI of 1%, this threshold increased to 41 per 100,000. In uncertainty analyses (Monte Carlo simulations) which assumed an ARI of 0.1%, QALYs were not significantly increased by BCG unless SCID incidence is 0. With this ARI, QALYs were significantly decreased among vaccinated children if SCID incidence exceeds 23 per 100,000. BCG is associated with a significant increase in QALYs if the ARI is 1%, and SCID incidence is below 5 per 100,000. CONCLUSION: The possibility that Canadian Aboriginal children are at increased risk for SCID has serious implications for continued BCG use in this population. In this context, enhanced TB Control ā including early detection and treatment of infection ā may be a safer, more effective alternative
The effect of regular walks on various health aspects in older people with dementia: protocol of a randomized-controlled trial
<p>Abstract</p> <p>Background</p> <p>Physical activity has proven to be beneficial for physical functioning, cognition, depression, anxiety, rest-activity rhythm, quality of life (QoL), activities of daily living (ADL) and pain in older people. The aim of this study is to investigate the effect of walking regularly on physical functioning, the progressive cognitive decline, level of depression, anxiety, rest-activity rhythm, QoL, ADL and pain in older people with dementia.</p> <p>Methods/design</p> <p>This study is a longitudinal randomized controlled, single blind study. Ambulatory older people with dementia, who are regular visitors of daily care or living in a home for the elderly or nursing home in the Netherlands, will be randomly allocated to the experimental or control condition. Participants of the experimental group make supervised walks of 30 minutes a day, 5 days a week, as part of their daily nursing care. Participants of the control group will come together three times a week for tea or other sedentary activities to control for possible positive effects of social interaction. All dependent variables will be assessed at baseline and after 6 weeks, and 3, 6, 9, 12 and 18 months of intervention.</p> <p>The dependent variables include neuropsychological tests to assess cognition, physical tests to determine physical functioning, questionnaires to assess ADL, QoL, level of depression and anxiety, actigraphy to assess rest-activity rhythm and pain scales to determine pain levels. Potential moderating variables at baseline are: socio-demographic characteristics, body mass index, subtype of dementia, apolipoprotein E (ApoE) genotype, medication use and comorbidities.</p> <p>Discussion</p> <p>This study evaluates the effect of regular walking as a treatment for older people with dementia. The strength of this study is that 1) it has a longitudinal design with multiple repeated measurements, 2) we assess many different health aspects, 3) the intervention is not performed by research staff, but by nursing staff which enables it to become a routine in usual care. Possible limitations of the study are that 1) only active minded institutions are willing to participate creating a selection bias, 2) the drop-out rate will be high in this population, 3) not all participants will be able to perform/understand all tests.</p> <p>Trial registration</p> <p><a href="http://www.trialregister.nl/trialreg/admin/rctview.asp?TC=1482">NTR1482</a></p
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