18 research outputs found

    A second look at N=1 supersymmetric AdS_4 vacua of type IIA supergravity

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    We show that a class of type IIA vacua recently found within the N=4 effective approach corresponds to compactification on Ads_4 \times S^3 \times S^3/Z_2^3. The results obtained using the effective method completely match the general ten-dimensional analysis for the existence of N=1 warped compactifications on Ads_4 \times M_6. In particular, we verify that the internal metric is nearly-Kahler and that for specific values of the parameters the Bianchi identity of the RR 2-form is fulfilled without sources. For another range of parameters, including the massless case, the Bianchi identity is satisfied when D6-branes are introduced. Solving the tadpole cancellation conditions in D=4 we are able to find examples of appropriate sets of branes. In the second part of this paper we describe how an example with internal space CP^3 but with non nearly-Kahler metric fits into the general analysis of flux vacua.Comment: Latex file, 35 pages, no figures. Reference added, minor corrections adde

    D-branes on AdS flux compactifications

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    We study D-branes in N=1 flux compactifications to AdS_4. We derive their supersymmetry conditions and express them in terms of background generalized calibrations. Basically because AdS has a boundary, the analysis of stability is more subtle and qualitatively different from the usual case of Minkowski compactifications. For instance, stable D-branes filling AdS_4 may wrap trivial internal cycles. Our analysis gives a geometric realization of the four-dimensional field theory approach of Freedman and collaborators. Furthermore, the one-to-one correspondence between the supersymmetry conditions of the background and the existence of generalized calibrations for D-branes is clarified and extended to any supersymmetric flux background that admits a time-like Killing vector and for which all fields are time-independent with respect to the associated time. As explicit examples, we discuss supersymmetric D-branes on IIA nearly Kaehler AdS_4 flux compactifications.Comment: 43 pages, 2 pictures, 1 table; v2: added references, color to figure and corrected typo in (6.21b

    From ten to four and back again: how to generalize the geometry

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    We discuss the four-dimensional N=1 effective approach in the study of warped type II flux compactifications with SU(3)x SU(3)-structure to AdS_4 or flat Minkowski space-time. The non-trivial warping makes it natural to use a supergravity formulation invariant under local complexified Weyl transformations. We obtain the classical superpotential from a standard argument involving domain walls and generalized calibrations and show how the resulting F-flatness and D-flatness equations exactly reproduce the full ten-dimensional supersymmetry equations. Furthermore, we consider the effect of non-perturbative corrections to this superpotential arising from gaugino condensation or Euclidean D-brane instantons. For the latter we derive the supersymmetry conditions in N=1 flux vacua in full generality. We find that the non-perturbative corrections induce a quantum deformation of the internal generalized geometry. Smeared instantons allow to understand KKLT-like AdS vacua from a ten-dimensional point of view. On the other hand, non-smeared instantons in IIB warped Calabi-Yau compactifications 'destabilize' the Calabi-Yau complex structure into a genuine generalized complex one. This deformation gives a geometrical explanation of the non-trivial superpotential for mobile D3-branes induced by the non-perturbative corrections.Comment: LaTeX, 47 pages, v2, references, hyperref added, v3, correcting small inaccuracies in eqs. (2.6a) and (5.16

    Towards Minkowski Vacua in Type II String Compactifications

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    We study the vacuum structure of compactifications of type II string theories on orientifolds with SU(3)xSU(3) structure. We argue that generalised geometry enables us to treat these non-geometric compactifications using a supergravity analysis in a way very similar to geometric compactifications. We find supersymmetric Minkowski vacua with all the moduli stabilised at weak string coupling and all the tadpole conditions satisfied. Generically the value of the moduli fields in the vacuum is parametrically controlled and can be taken to arbitrarily large values.Comment: 33 pages; v2 minor corrections, references added, version to appear in JHE

    Some No-go Theorems for String Duals of Non-relativistic Lifshitz-like Theories

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    We study possibilities of string theory embeddings of the gravity duals for non-relativistic Lifshitz-like theories with anisotropic scale invariance. We search classical solutions in type IIA and eleven-dimensional supergravities which are expected to be dual to (2+1)-dimensional Lifshitz-like theories. Under reasonable ansaetze, we prove that such gravity duals in the supergravities are not possible. We also discuss a possible physical reason behind this.Comment: 18 pages, Latex, flux conditions clarified (v2), brief summary of results added (v3

    Type IIA Moduli Stabilization

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    We demonstrate that flux compactifications of type IIA string theory can classically stabilize all geometric moduli. For a particular orientifold background, we explicitly construct an infinite family of supersymmetric vacua with all moduli stabilized at arbitrarily large volume, weak coupling, and small negative cosmological constant. We obtain these solutions from both ten-dimensional and four-dimensional perspectives. For more general backgrounds, we study the equations for supersymmetric vacua coming from the effective superpotential and show that all geometric moduli can be stabilized by fluxes. We comment on the resulting picture of statistics on the landscape of vacua.Comment: 48 pages, 2 figures, LaTeX. v2: references added. v3: minor comments & references adde

    The global burden of cancer attributable to risk factors, 2010–19: a systematic analysis for the Global Burden of Disease Study 2019

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    BACKGROUND: Understanding the magnitude of cancer burden attributable to potentially modifiable risk factors is crucial for development of effective prevention and mitigation strategies. We analysed results from the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2019 to inform cancer control planning efforts globally. METHODS: The GBD 2019 comparative risk assessment framework was used to estimate cancer burden attributable to behavioural, environmental and occupational, and metabolic risk factors. A total of 82 risk–outcome pairs were included on the basis of the World Cancer Research Fund criteria. Estimated cancer deaths and disability-adjusted life-years (DALYs) in 2019 and change in these measures between 2010 and 2019 are presented. FINDINGS: Globally, in 2019, the risk factors included in this analysis accounted for 4·45 million (95% uncertainty interval 4·01–4·94) deaths and 105 million (95·0–116) DALYs for both sexes combined, representing 44·4% (41·3–48·4) of all cancer deaths and 42·0% (39·1–45·6) of all DALYs. There were 2·88 million (2·60–3·18) risk-attributable cancer deaths in males (50·6% [47·8–54·1] of all male cancer deaths) and 1·58 million (1·36–1·84) risk-attributable cancer deaths in females (36·3% [32·5–41·3] of all female cancer deaths). The leading risk factors at the most detailed level globally for risk-attributable cancer deaths and DALYs in 2019 for both sexes combined were smoking, followed by alcohol use and high BMI. Risk-attributable cancer burden varied by world region and Socio-demographic Index (SDI), with smoking, unsafe sex, and alcohol use being the three leading risk factors for risk-attributable cancer DALYs in low SDI locations in 2019, whereas DALYs in high SDI locations mirrored the top three global risk factor rankings. From 2010 to 2019, global risk-attributable cancer deaths increased by 20·4% (12·6–28·4) and DALYs by 16·8% (8·8–25·0), with the greatest percentage increase in metabolic risks (34·7% [27·9–42·8] and 33·3% [25·8–42·0]). INTERPRETATION: The leading risk factors contributing to global cancer burden in 2019 were behavioural, whereas metabolic risk factors saw the largest increases between 2010 and 2019. Reducing exposure to these modifiable risk factors would decrease cancer mortality and DALY rates worldwide, and policies should be tailored appropriately to local cancer risk factor burden

    Superior vena cava obstruction after heart transplantation

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    Superior vena cava obstruction can be a serious complication after heart transplantation. A 58-year-old man with ischemic cardiomyopathy underwent orthotopic bicaval heart transplantation. On the 12th postoperative day, one hour after removing the central venous line, he developed sudden onset of facial edema, cyanosis, and tachycardia. Emergency transesophageal echocardiography revealed superior vena caval thrombosis at the site of anastomosis. Considering the risks of surgical reexploration, the superior vena cava was recanalized by stent deployment. All of the patient's symptoms were relieved a few hours after stent placement. © 2014 SAGE Publications

    Superior vena cava obstruction after heart transplantation

    No full text
    Superior vena cava obstruction can be a serious complication after heart transplantation. A 58-year-old man with ischemic cardiomyopathy underwent orthotopic bicaval heart transplantation. On the 12th postoperative day, one hour after removing the central venous line, he developed sudden onset of facial edema, cyanosis, and tachycardia. Emergency transesophageal echocardiography revealed superior vena caval thrombosis at the site of anastomosis. Considering the risks of surgical reexploration, the superior vena cava was recanalized by stent deployment. All of the patient's symptoms were relieved a few hours after stent placement. © 2014 SAGE Publications

    Gene expression profiles of aralkylamine n-acetyltransferase, b-cell translocation gene-2 and fatty acid synthase in pasture-based primiparous Holstein-Friesian dairy cows supplemented with crude degummed canola oil

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    The effect of oil-rich supplements on the expression of genes involved in lipogenesis and reproduction in pasturebased dairy cows is currently unknown, or at best, scanty and limited to impacts on cow liveweight, body condition score, milk composition, fatty acid and plasma metabolite profiles only. This research investigated the gene expression patterns of Aralkylamine N-acetyltransferase (AANAT), B-cell translocation gene-2 (BTG2) and Fatty Acid Synthase (FASN) genes in response to incremental levels of dietary crude degummed canola oil (CDCO). We tested the hypothesis that the relative mRNA abundance and gene expression profiles of AANAT, BTG2 and FASN in primiparous Holstein-Friesian cows will be up-regulated in response to post-partum dietary supplementation with CDCO in a typical pasture-based dairy production system. Thus, the primary objective of this study was to investigate the expression of AANAT, BTG2 and FASN genes in response to incremental levels of CDCO. A random allocation of primiparous Holstein-Friesian dairy cows into four treatment groups comprising wheat-based pelleted with no supplemental CDCO (control), or with CDCO added at 25 ml kg-1 DM (low), 35 ml kg-1 DM (medium) and 50 ml kg-1 DM (high) was utilized in a ten-week experimental feeding trial including two weeks of adjustment. Both level of supplementation and their interaction with duration were significant sources of variation (P<0.05) that influenced BTG2 expression, while the expressions of AANAT and FASN genes were unaffected (P>0.05). The high (0.67 fold), medium (0.87 fold) and low (0.56 fold) treatments had suppressed BTG2 expressions compared to the control (1.0 fold) group. The low expression of BTG2 might be important when the reproductive system of cows is recovering from the effect of gestation and new cell growth is required
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