Background
Executive function is a concept for higher‐order cognitive functions, which have the role of controller and modulator of cognitive abilities. The consensus in the literature is that people ...with an intellectual disability perform significantly lower on executive function tasks than groups matched on chronological age. The comparison with groups matched on mental age is less clear. Therefore, the objective of this meta‐analysis was to investigate to what extent executive function is impaired in people with intellectual disability compared with a typically developing control group matched on mental age. It was also investigated if the executive function component and intellectual disability aetiology moderated the effect.
Methods
Eligibility criteria were participants with intellectual disability (IQ ≤ 75) without a dual diagnosis; a comparison group matched on mental age; executive function outcome reported in a group comparison study design with n ≥ 10. Working memory tasks and ratings of executive function were not included. The literature search yielded 6637 potentially interesting articles. Twenty‐six studies (with 99 effect sizes) including 1395 participants were included in the quantitative synthesis.
Results
A multilevel random‐effects meta‐analysis found that people with intellectual disability performed statistically significantly lower than the mental age‐matched group on the executive function tasks, g = −0.34, 95% confidence interval = −0.53, −0.16. However, the heterogeneity between effect sizes was large. The intellectual disability aetiology moderator was significant, but it only reduced the heterogeneity marginally.
Conclusion
The overall conclusion is that individuals with an intellectual disability have more problems with executive function tasks than mental age‐matched controls. Limitations are the large unexplained variance and the remarkably high number (69) of different tests that were used, which make more detailed conclusions problematic. This meta‐analysis implies that future studies need to be of better quality, to have higher power, and to a higher degree use the same executive function tests.
A
bstract
In
arXiv:1705.10172
it was proposed that string theory replaces Schwarzschild black holes with horizonless thin shells with an AdS interior. In this paper we extend the analysis to slowly ...rotating black holes, solving the Israel-Lanczos-Sen junction conditions for a rotating shell composed of stringy matter to determine the metric. Outside of the shell we find a vacuum solution that differs from Kerr with a 32% larger quadrupole moment. We discuss the observational consequences and explore the possibility to distinguish between a black shell and a black hole. Promising methods include imaging of the black hole at the center of the Milky Way using the Event Horizon Telescope, precision measurements of stars in close orbits around the central black hole, and future observations of colliding super massive black holes using the space based gravitational wave observatory LISA.
A
bstract
We elaborate on the decay of branes inside throat geometries that are supported by flux carrying charges opposite to the brane. Our main point is that such back-grounds necessarily have a ...local, possibly diverging, pile up of brane-charges dissolved in flux around the anti-brane due to the (fatal) attraction of the flux towards the brane. We explain that this causes enhanced brane-flux annihilation and is in tension with the idea that anti-branes can be used to construct meta-stable vacua. We argue that stable configurations — if they at all exist — are not obtainable within SUGR. The problem we point out is already present when the back-reaction is confined in the IR and the associated uplift energy small. Our results are valid in the regime that is complementary to a recent analysis of Bena et al.
A
bstract
The stabilisation of the dilaton and volume in tree-level flux compactifications leads to model independent and thus very powerful existence and stability criteria for dS solutions. In this ...paper we show that the sizes of cycles wrapped by orientifold planes are scalars whose scalings in the potential are not entirely model independent, but enough to entail strong stability constraints. For all known dS solutions arising from massive IIA supergravity flux compactifications on SU(3)-structure manifolds the tachyons are exactly within the subspace spanned by the dilaton, the total volume and the volumes of the orientifold cycles. We illustrate this in detail for the well-studied case of the
O
6 plane compactification on
. For that example we uncover another novel structure in the tachyon spectrum: the dS solutions have a singular, but supersymmetric, Minkowski limit, in which the tachyon exactly aligns with the sgoldstino.
We argue that the choice of boundary condition for the wave function in quantum cosmology depends on the UV completion of general relativity. We provide an explicit example using a braneworld ...scenario in which a de Sitter cosmology is induced on the surface of a Coleman-de Luccia bubble in a 5-dimensional AdS space. The corresponding boundary conditions are unambiguously fixed by demanding consistency with the known physics of bubble nucleation and this selects the Vilenkin weighting for the amplitude from a 4D viewpoint.
A swamp of non-SUSY vacua Danielsson, U. H.; Dibitetto, G.; Vargas, S. C.
The journal of high energy physics,
11/2017, Letnik:
2017, Številka:
11
Journal Article
Recenzirano
Odprti dostop
A
bstract
We consider known examples of non-supersymmetric AdS
7
and AdS
4
solutions arising from compactifications of massive type IIA supergravity and study their stability, taking into account the ...coupling between closed- and open-string sector excitations. Generically, open strings are found to develop modes with masses below the Breitenlohner-Freedman (BF) bound. We comment on the relation with the Weak Gravity Conjecture, and how this analysis may play an important role in examining the validity of non-supersymmetric constructions in string theory.
We study the universal conditions for quantum nonperturbative stability against bubble nucleation for pertubatively stable AdS vacua based on positive energy theorems. We also compare our analysis ...with the preexisting ones in the literature carried out within the thin-wall approximation. The aforementioned criterion is then tested in two explicit examples describing massive type IIA string theory compactified on S3 and S3×S3, respectively. The AdS landscape of both classes of compactifications is known to consist of a set of isolated points. The main result is that all critical points respecting the Breitenlohner-Freedman (BF) bound also turn out be stable at a nonperturbative level. Finally, we speculate on the possible universal features that may be extracted from the above specific examples.
A
bstract
In this note we discuss a possible resolution of the flux singularities associated with the insertion of branes in backgrounds supported by fluxes that carry charges opposite to the branes. ...We present qualitative arguments that such a setup could be unstable both in the closed and open string sector. The singularities in the fluxes then get naturally resolved by taking the true solution to be a time-dependent process in which flux gets attracted towards the brane and subsequently annihilates.
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