6,891 research outputs found
Towards a Unified Theory of Massless Superfields of All Superspins
We describe the ``universal'' action for massless superfields of all
superspins in N = 1, D = 4 anti-de Sitter superspace as a gauge theory of
unconstrained superfields taking their values in the commutative algebra of
analytic functions over a one-sheeted hyperboloid in . The action is
invariant under N = 2 supersymmetry transformations which form a closed algebra
off the mass-shell.Comment: 12 pages, LaTe
Definition of technology development missions for early space stations: Large space structures
The objectives studied are the definition of the tested role of an early Space Station for the construction of large space structures. This is accomplished by defining the LSS technology development missions (TDMs) identified in phase 1. Design and operations trade studies are used to identify the best structural concepts and procedures for each TDMs. Details of the TDM designs are then developed along with their operational requirements. Space Station resources required for each mission, both human and physical, are identified. The costs and development schedules for the TDMs provide an indication of the programs needed to develop these missions
On Graph-Theoretic Identifications of Adinkras, Supersymmetry Representations and Superfields
In this paper we discuss off-shell representations of N-extended
supersymmetry in one dimension, ie, N-extended supersymmetric quantum
mechanics, and following earlier work on the subject codify them in terms of
certain graphs, called Adinkras. This framework provides a method of generating
all Adinkras with the same topology, and so also all the corresponding
irreducible supersymmetric multiplets. We develop some graph theoretic
techniques to understand these diagrams in terms of a relatively small amount
of information, namely, at what heights various vertices of the graph should be
"hung".
We then show how Adinkras that are the graphs of N-dimensional cubes can be
obtained as the Adinkra for superfields satisfying constraints that involve
superderivatives. This dramatically widens the range of supermultiplets that
can be described using the superspace formalism and organizes them. Other
topologies for Adinkras are possible, and we show that it is reasonable that
these are also the result of constraining superfields using superderivatives.
The family of Adinkras with an N-cubical topology, and so also the sequence
of corresponding irreducible supersymmetric multiplets, are arranged in a
cyclical sequence called the main sequence. We produce the N=1 and N=2 main
sequences in detail, and indicate some aspects of the situation for higher N.Comment: LaTeX, 58 pages, 52 illustrations in color; minor typos correcte
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Comparison of Bayesian and frequentist group-sequential clinical trial designs
Background: There is a growing interest in the use of Bayesian adaptive designs in late-phase clinical trials. This
includes the use of stopping rules based on Bayesian analyses in which the frequentist type I error rate is controlled as
in frequentist group-sequential designs.
Methods: This paper presents a practical comparison of Bayesian and frequentist group-sequential tests. Focussing
on the setting in which data can be summarised by normally distributed test statistics, we evaluate and compare
boundary values and operating characteristics.
Results: Although Bayesian and frequentist group-sequential approaches are based on fundamentally different
paradigms, in a single arm trial or two-arm comparative trial with a prior distribution specified for the treatment
difference, Bayesian and frequentist group-sequential tests can have identical stopping rules if particular critical values
with which the posterior probability is compared or particular spending function values are chosen. If the Bayesian
critical values at different looks are restricted to be equal, O’Brien and Fleming’s design corresponds to a Bayesian
design with an exceptionally informative negative prior, Pocock’s design to a Bayesian design with a non-informative
prior and frequentist designs with a linear alpha spending function are very similar to Bayesian designs with slightly
informative priors.
This contrasts with the setting of a comparative trial with independent prior distributions specified for treatment
effects in different groups. In this case Bayesian and frequentist group-sequential tests cannot have the same
stopping rule as the Bayesian stopping rule depends on the observed means in the two groups and not just on their
difference. In this setting the Bayesian test can only be guaranteed to control the type I error for a specified range of
values of the control group treatment effect.
Conclusions: Comparison of frequentist and Bayesian designs can encourage careful thought about design
parameters and help to ensure appropriate design choices are made
On Supermultiplet Twisting and Spin-Statistics
Twisting of off-shell supermultiplets in models with 1+1-dimensional
spacetime has been discovered in 1984, and was shown to be a generic feature of
off-shell representations in worldline supersymmetry two decades later. It is
shown herein that in all supersymmetric models with spacetime of four or more
dimensions, this off-shell supermultiplet twisting, if non-trivial, necessarily
maps regular (non-ghost) supermultiplets to ghost supermultiplets. This feature
is shown to be ubiquitous in all fully off-shell supersymmetric models with
(BV/BRST-treated) constraints.Comment: Extended version, including a new section on manifestly off-shell and
supersymmetric BRST treatment of gauge symmetry; added reference
Chiral supergravity actions and superforms
The superform construction of supergravity actions, christened the "ectoplasm
method," is based on the use of a closed super d-form in the case of d
space-time dimensions. In known examples, such superforms are obtained by
iteratively solving nontrivial cohomological problems. The latter usually makes
this scheme no less laborious than the normal coordinate method for deriving
component actions for matter-coupled supergravity. In this note we present an
alternative procedure to generate required superforms in four space-time
dimensions, which makes use of self-dual vector multiplets. It provides the
shortest derivation of chiral actions in two different theories: (i) N = 1 old
minimal supergravity; and (ii) N = 2 conformal supergravity. The N = 2
superform construction is developed here for the first time. Although our
consideration is restricted to the case of four dimensions, a generalization to
higher dimensions is plausible.Comment: 14 pages; V2: minor correction
A Superfield for Every Dash-Chromotopology
The recent classification scheme of so-called adinkraic off-shell
supermultiplets of N-extended worldline supersymmetry without central charges
finds a combinatorial explosion. Completing our earlier efforts, we now
complete the constructive proof that all of these trillions or more of
supermultiplets have a superfield representation. While different as
superfields and supermultiplets, these are still super-differentially related
to a much more modest number of minimal supermultiplets, which we construct
herein.Comment: 13 pages, integrated illustration
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