37 research outputs found
Supersymmetric branes on curved spaces and fluxes
We discuss general supersymmetric brane configurations in flux backgrounds of
string and M-theory and derive a necessary condition for the worldvolume theory
to be supersymmetric on a given curved manifold. This condition resembles very
much the conditions found from coupling a supersymmetric field theory to
off-shell supergravity but can be derived in any dimension and for up to
sixteen supercharges. Apart from the topological twist, all couplings appearing
in the supersymmetry condition are linked to fluxes in the bulk. We explicitly
derive the condition for D3-, M2- and M5-branes, in which case the results are
also useful for constructing holographic duals to the corresponding field
theories. In setups we compare the supersymmetry conditions to those that
arise by coupling the field theory to off-shell supergravity. We find that the
couplings of both old and new minimal supergravity are simultaneously realized,
indicating that off-shell supergravity should be coupled via the S-multiplet of
16/16 supergravity in order to describe all supersymmetric brane theories on
curved spaces.Comment: 18 pages; v2: Added discussion refering to 16/16 supergravity for the
N=1 case and added reference
Maximally Supersymmetric AdS4 Vacua in N=4 Supergravity
We study AdS backgrounds of N=4 supergravity in four space-time dimensions
which preserve all sixteen supercharges. We show that the graviphotons have to
form a subgroup of the gauge group that consists of an electric and a magnetic
SO(3)_+ x SO(3)_-. Moreover, these N=4 AdS backgrounds are necessarily isolated
points in field space which have no moduli.Comment: 11 page
N=4 Supersymmetric AdS5 Vacua and their Moduli Spaces
We classify the N=4 supersymmetric AdS5 backgrounds that arise as solutions
of five-dimensional N=4 gauged supergravity. We express our results in terms of
the allowed embedding tensor components and identify the structure of the
associated gauge groups. We show that the moduli space of these AdS vacua is of
the form SU(1,m)/(U(1)x SU(m)) and discuss our results regarding
holographically dual N=2 SCFTs and their conformal manifolds.Comment: 29 pages; v2: published versio
Enhanced supersymmetry from vanishing Euler number
We argue that compactifications on Calabi-Yau threefolds with vanishing Euler
number yield effective four dimensional theories exhibiting (spontaneously
broken) N=4 supersymmetry. To this end, we derive the low-energy effective
action for general SU(2) structure manifolds in type IIA string theory and show
its consistency with gauged N=4 supergravity. Focusing on the special case of
Calabi-Yau manifolds with vanishing Euler number, we explain the absence of
perturbative corrections at the two-derivative level. In addition, we
conjecture that all non-perturbative corrections are governed and constrained
by the couplings of N=4 massive gravitino multiplets.Comment: 49 page
The N=4 effective action of type IIA supergravity compactified on SU(2)-structure manifolds
We study compactifications of type IIA supergravity on six-dimensional
manifolds with SU(2) structure and compute the low-energy effective action in
terms of the non-trivial intrinsic torsion. The consistency with gauged N=4
supergravity is established and the gauge group is determined. Depending on the
structure of the intrinsic torsion, antisymmetric tensor fields can become
massive.Comment: 29 pages, latex, v2: minor corrections, added references, published
versio
Compact G2 holonomy spaces from SU(3) structures
We construct novel classes of compact G2 spaces from lifting type IIA flux
backgrounds with O6 planes. There exists an extension of IIA Calabi-Yau
orientifolds for which some of the D6 branes (required to solve the RR tadpole)
are dissolved in fluxes. The backreaction of these fluxes deforms the
Calabi-Yau manifold into a specific class of SU(3)-structure manifolds. The
lift to M-theory again defines compact G2 manifolds, which in case of toroidal
orbifolds are a twisted generalisation of the Joyce construction. This
observation also allows a clear identification of the moduli space of a warped
compactification with fluxes. We provide a few explicit examples, of which some
can be constructed from T-dualising known IIB orientifolds with fluxes. Finally
we discuss supersymmetry breaking in this context and suggest that the purely
geometric picture in M-theory could provide a simpler setting to address some
of the consistency issues of moduli stabilisation and de Sitter uplifting.Comment: 32 pages; v2. minor changes and corrections, version accepted on JHE
The quantization problem in Scherk-Schwarz compactifications
15 pages, v2: significant revision; overall conclusions altered, results on classification of solvmanifolds added, v3: published version with an extended classification of latticesInternational audienceWe re-examine the quantization of structure constants, or equivalently the choice of lattice in the so-called flat group reductions, introduced originally by Scherk and Schwarz. Depending on this choice, the vacuum either breaks supersymmetry and lifts certain moduli, or preserves all supercharges and is identical to the one obtained from the torus reduction. Nonetheless the low-energy effective theory proposed originally by Scherk and Schwarz is a gauged supergravity that describes supersymmetry breaking and moduli lifting for all values of the structure constants. When the vacuum does not break supersymmetry, such a description turns out to be an artifact of the consistent truncation to left-invariant forms as illustrated for the example of ISO(2). We furthermore discuss the construction of flat groups in d dimensions and find that the Scherk--Schwarz algorithm is exhaustive. A classification of flat groups up to six dimensions and a discussion of all possible lattices is presented
Addressing label noise for electronic health records: insights from computer vision for tabular data
The analysis of extensive electronic health records (EHR) datasets often calls for automated solutions, with machine learning (ML) techniques, including deep learning (DL), taking a lead role. One common task involves categorizing EHR data into predefined groups. However, the vulnerability of EHRs to noise and errors stemming from data collection processes, as well as potential human labeling errors, poses a significant risk. This risk is particularly prominent during the training of DL models, where the possibility of overfitting to noisy labels can have serious repercussions in healthcare. Despite the well-documented existence of label noise in EHR data, few studies have tackled this challenge within the EHR domain. Our work addresses this gap by adapting computer vision (CV) algorithms to mitigate the impact of label noise in DL models trained on EHR data. Notably, it remains uncertain whether CV methods, when applied to the EHR domain, will prove effective, given the substantial divergence between the two domains. We present empirical evidence demonstrating that these methods, whether used individually or in combination, can substantially enhance model performance when applied to EHR data, especially in the presence of noisy/incorrect labels. We validate our methods and underscore their practical utility in real-world EHR data, specifically in the context of COVID-19 diagnosis. Our study highlights the effectiveness of CV methods in the EHR domain, making a valuable contribution to the advancement of healthcare analytics and research