8,391 research outputs found

    A New Handle on de Sitter Compactifications

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    We construct a large new class of de Sitter (and anti de Sitter) vacua of critical string theory from flux compactifications on products of Riemann surfaces. In the construction, the leading effects stabilizing the moduli are perturbative. We show that these effects self-consistently dominate over standard estimates for further αâ€Č\alpha^\prime and quantum corrections, via tuning available from large flux and brane quantum numbers.Comment: 26 pages, harvmac big. v2: Correction generalizing specific ingredients required for tunable negative term; conclusions and structure of potential unchange

    The Scaling of the No Scale Potential and de Sitter Model Building

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    We propose a variant of the KKLT (A)dS flux vacuum construction which does not require an antibrane to source the volume modulus. The strategy is to find nonzero local minima of the no-scale potential in the complex structure and dilaton directions in moduli space. The corresponding no-scale potential expanded about this point sources the volume modulus in the same way as does the antibrane of the KKLT construction. We exhibit explicit examples of such nonzero local minima of the no-scale potential in a simple toroidal orientifold model.Comment: 11 pages, harvmac big. v2: trivial typos fixe

    Dietary Patterns and Cognitive Function among Older Community-Dwelling Adults.

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    Diet may be an important modifiable risk factor for maintenance of cognitive health in later life. This study aimed at examining associations between common dietary indices and dietary patterns defined by factor analysis and cognitive function in older community-dwelling adults. Dietary information for 1499 participants from the Rancho Bernardo Study was collected in 1988⁻1992 and used to calculate the alternate Mediterranean diet score, Alternate Healthy Eating Index (AHEI)-2010 score and factor scores derived from factor analysis of nutrients. Global cognitive function, executive function, verbal fluency and episodic memory were assessed at approximate four-year intervals from 1988⁻2016. Linear mixed models were used to examine associations between dietary patterns and cognitive trajectories. Estimates for the highest vs. lowest tertile in models adjusting for age, sex, education, energy intake, lifestyle variables and retest effect showed greater adherence to the Mediterranean score was associated with better baseline global cognitive function (ÎČ (95% CI) = 0.33 (0.11, 0.55)). The AHEI-2010 score was not significantly associated with cognitive performance. Higher loading on a plant polyunsaturated fatty acid (PUFA)/vitamin E factor was associated with better baseline global cognitive function and executive function (ÎČ = 0.22 (0.02, 0.42) and ÎČ = -7.85 (-13.20, -2.47)). A sugar/low protein factor was associated with poorer baseline cognitive function across multiple domains. Dietary patterns were not associated with cognitive decline over time. Adherence to a healthy diet with foods high in PUFA and vitamin E and a low sugar to protein ratio, as typified by a Mediterranean diet, may be beneficial for cognitive health in late life

    Gaugino Masses in Modular Invariant Supergravity

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    We calculate gaugino masses in string-derived models with hidden-sector gaugino condensation. The linear multiplet formulation for the dilaton superfield is used to implement perturbative modular invariance. The contribution arising from quantum effects in the observable sector includes the term recently found in generic supergravity models. A much larger contribution is present if matter fields with Standard Model gauge couplings also couple to the Green-Schwarz counter term. We comment on the relation of our K\"ahler U(1) superspace formalism to other calculations.Comment: 15 pages, full postscript also available from http://phyweb.lbl.gov/theorygroup/papers/43259.p

    Application of Multimodal Neuromonitoring in Posterior Inferior Cerebellar Artery Aneurysm Clippings: Review of Two Cases.

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    Neurophysiological monitoring is advocated for the prevention of neurological sequelae secondary to the clipping of an aneurysm involved in posterior circulation. Unfortunately, there is a paucity in the literature regarding what neurophysiological monitoring techniques are best employed. The authors here present two cases where multimodal neuromonitoring techniques were used during the clippings of two posterior inferior cerebellar artery (PICA) aneurysms. There is increased neurologic morbidity associated with PICA aneurysm clippings, as a number of eloquent structures live in close proximity to the PICA. The application of a multimodal neuromonitoring paradigm may reduce a poor neurological outcome

    GLSMs for non-Kahler Geometries

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    We identify a simple mechanism by which H-flux satisfying the modified Bianchi identity arises in garden-variety (0,2) gauged linear sigma models. Taking suitable limits leads to effective gauged linear sigma models with Green-Schwarz anomaly cancellation. We test the quantum-consistency of a class of such effective theories by constructing an off-shell superconformal algebra, providing evidence that these models run to good CFTs in the deep IR.Comment: 37 pages, Minor updates for v

    Volume Stabilization via αâ€Č\alpha^\prime Corrections in Type IIB Theory with Fluxes

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    We consider the Type IIB string theory in the presence of various extra 7/7ˉ7/\bar 7-brane pairs compactified on a warped Calabi-Yau threefold that admits a conifold singularity. We demonstrate that the volume modulus can be stabilized perturbatively at a non-supersymmetric AdS4/dS4AdS_4/dS_4 vacuum by the effective potential that includes the stringy (αâ€Č)3(\alpha^\prime)^3 correction obtained by Becker {\it et al.} together with a combination of positive tension and anomalous negative tension terms generated by the additional 7-brane-antibrane pairs.Comment: 20 pages, 4 figures, parts of introduction and conclusions are modifie

    A Phase Transition between Small and Large Field Models of Inflation

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    We show that models of inflection point inflation exhibit a phase transition from a region in parameter space where they are of large field type to a region where they are of small field type. The phase transition is between a universal behavior, with respect to the initial condition, at the large field region and non-universal behavior at the small field region. The order parameter is the number of e-foldings. We find integer critical exponents at the transition between the two phases.Comment: 21 pages, 8 figure
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