5,593 research outputs found
N=2 Conformal Superspace in Four Dimensions
We develop the geometry of four dimensional N=2 superspace where the entire
conformal algebra of SU(2,2|2) is realized linearly in the structure group
rather than just the SL(2,C) x U(2)_R subgroup of Lorentz and R-symmetries,
extending to N=2 our prior result for N=1 superspace. This formulation
explicitly lifts to superspace the existing methods of the N=2 superconformal
tensor calculus; at the same time the geometry, when degauged to SL(2,C) x
U(2)_R, reproduces the existing formulation of N=2 conformal supergravity
constructed by Howe.Comment: 43 pages; v2 references added, acknowledgments update
The Anomaly Structure of Regularized Supergravity
On-shell Pauli-Villars regularization of the one-loop divergences of
supergravity theories is used to study the anomaly structure of supergravity
and the cancellation of field theory anomalies under a gauge
transformation and under the T-duality group of modular transformations in
effective supergravity theories with three K\"ahler moduli obtained from
orbifold compactification of the weakly coupled heterotic string. This
procedure requires constraints on the chiral matter representations of the
gauge group that are consistent with known results from orbifold
compactifications. Pauli-Villars regulator fields allow for the cancellation of
all quadratic and logarithmic divergences, as well as most linear divergences.
If all linear divergences were canceled, the theory would be anomaly free, with
noninvariance of the action arising only from Pauli-Villars masses. However
there are linear divergences associated with nonrenormalizable
gravitino/gaugino interactions that cannot be canceled by PV fields. The
resulting chiral anomaly forms a supermultiplet with the corresponding
conformal anomaly, provided the ultraviolet cut-off has the appropriate field
dependence, in which case total derivative terms, such as Gauss-Bonnet, do not
drop out from the effective action. The anomalies can be partially canceled by
the four-dimensional version of the Green-Schwarz mechanism, but additional
counterterms, and/or a more elaborate set of Pauli-Villars fields and
couplings, are needed to cancel the full anomaly, including D-term
contributions to the conformal anomaly that are nonlinear in the parameters of
the anomalous transformations.Comment: 103 page
Rigid 4D N=2 supersymmetric backgrounds and actions
We classify all N=2 rigid supersymmetric backgrounds in four dimensions with
both Lorentzian and Euclidean signature that preserve eight real supercharges,
up to discrete identifications. Among the backgrounds we find specific warpings
of S^3 x R and AdS_3 x R, AdS_2 x S^2 and H^2 x S^2 with generic radii, and
some more exotic geometries. We provide the generic two-derivative rigid vector
and hypermultiplet actions and analyze the conditions imposed on the special
Kahler and hyperkahler target spaces.Comment: 50 + 17 pages; v2: minor corrections, published versio
Non-renormalization theorems and N=2 supersymmetric backgrounds
The conditions for fully supersymmetric backgrounds of general N=2 locally
supersymmetric theories are derived based on the off-shell superconformal
multiplet calculus. This enables the derivation of a non-renormalization
theorem for a large class of supersymmetric invariants with higher-derivative
couplings. The theorem implies that the invariant and its first order variation
must vanish in a fully supersymmetric background. The conjectured relation of
one particular higher-derivative invariant with a specific five-dimensional
invariant containing the mixed gauge-gravitational Chern-Simons term is
confirmed.Comment: 30 pages; v2: minor correction
Het verband tussen publiek belang en ontwerp bij het internet der dingen
Het internet der dingen levert een schat aan gegevens (“big data”) op over persoonlijk gedrag. Bij de benutting van deze gegevens is sprake van verschillende vormen van publiek belang waarvoor de overheid borgingsmechanismen in werking dient te stellen. Daarbij gaat het enerzijds om goede beschikbaarheid van gegevens, om opheffen van informatieasymmetrie als vorm van marktfalen, en anderzijds om het bieden van rechtsbescherming ten aanzien van veiligheid en privacy. In dit artikel bespreken wij hoe vanuit de principaal/agent benadering van regelgeving ten aanzien van borging van de verschillende onderdelen van het publiek belang het ontwerpproces van applicaties en systemen in het internet der dingen het best kan worden vormgegeven. Het voorbeeld van de slimme thermostaat Toon® leert hoe de samenwerking tussen ontwerpers en software ingenieurs heeft bijgedragen aan zowel een goede bescherming van de gegevens als aan een mogelijke prikkel tot energiebesparing
Nonlinear sigma models with AdS supersymmetry in three dimensions
In three-dimensional anti-de Sitter (AdS) space, there exist several
realizations of N-extended supersymmetry, which are traditionally labelled by
two non-negative integers p>=q such that p+q=N. Different choices of p and q,
with N fixed, prove to lead to different restrictions on the target space
geometry of supersymmetric nonlinear sigma-models. We classify all possible
types of hyperkahler target spaces for the cases N=3 and N=4 by making use of
two different realizations for the most general (p,q) supersymmetric
sigma-models: (i) off-shell formulations in terms of N=3 and N=4 projective
supermultiplets; and (ii) on-shell formulations in terms of covariantly chiral
scalar superfields in (2,0) AdS superspace. Depending on the type of N=3,4 AdS
supersymmetry, nonlinear sigma-models can support one of the following target
space geometries: (i) hyperkahler cones; (ii) non-compact hyperkahler manifolds
with a U(1) isometry group which acts non-trivially on the two-sphere of
complex structures; (iii) arbitrary hyperkahler manifolds including compact
ones. The option (iii) is realized only in the case of critical (4,0) AdS
supersymmetry.
As an application of the (4,0) AdS techniques developed, we also construct
the most general nonlinear sigma-model in Minkowski space with a non-centrally
extended N=4 Poincare supersymmetry. Its target space is a hyperkahler cone
(which is characteristic of N=4 superconformal sigma-models), but the
sigma-model is massive. The Lagrangian includes a positive potential
constructed in terms of the homothetic conformal Killing vector the target
space is endowed with. This mechanism of mass generation differs from the
standard one which corresponds to a sigma-model with the ordinary N=4 Poincare
supersymmetry and which makes use of a tri-holomorphic Killing vector.Comment: 109 pages; V2: comments adde
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