SL(2,R)/U(1) Supercoset and Elliptic Genera of Non-compact Calabi-Yau Manifolds

We first discuss the relationship between the SL(2;R)/U(1) supercoset and N=2 Liouville theory and make a precise correspondence between their representations. We shall show that the discrete unitary representations of SL(2;R)/U(1) theory correspond exactly to those massless representations of N=2 Liouville theory which are closed under modular transformations and studied in our previous work hep-th/0311141. It is known that toroidal partition functions of SL(2;R)/U(1) theory (2D Black Hole) contain two parts, continuous and discrete representations. The contribution of continuous representations is proportional to the space-time volume and is divergent in the infinite-volume limit while the part of discrete representations is volume-independent. In order to see clearly the contribution of discrete representations we consider elliptic genus which projects out the contributions of continuous representations: making use of the SL(2;R)/U(1), we compute elliptic genera for various non-compact space-times such as the conifold, ALE spaces, Calabi-Yau 3-folds with A_n singularities etc. We find that these elliptic genera in general have a complex modular property and are not Jacobi forms as opposed to the cases of compact Calabi-Yau manifolds.Comment: 39 pages, no figure; v2 references added, minor corrections; v3 typos corrected, to appear in JHEP; v4 typos corrected in eqs. (3.22) and (3.44

The statistics of string/M theory vacua

We discuss systematic approaches to the classification of string/M theory vacua, and physical questions this might help us resolve. To this end, we initiate the study of ensembles of effective Lagrangians, which can be used to precisely study the predictive power of string theory, and in simple examples can lead to universality results. Using these ideas, we outline an approach to estimating the number of vacua of string/M theory which can realize the Standard Model.Comment: harvmac, 72pp (v4: fixed error in discussion of quiver ensembles

Biomechanics models predict increasing smooth muscle tone as a novel therapeutic target for central arterial dysfunction in hypertension

Introduction:Vasodilation can paradoxically increase arterial stiffness in older, hypertensive adults. This study modeled increasing smooth muscle tone as a therapeutic strategy to improve central arterial dysfunction in hypertension using participant-specific simulations.Methods:Participant-specific models of the carotid artery were parameterized from vascular ultrasound measures of nitroglycerin-induced vasodilation in 18 hypertensive veterans. The acute changes in carotid artery mechanics were simulated for changes of +/- 2, +/- 4, and +/- 6% in smooth muscle tone and +/- 5, +/- 10, and +/- 15 mmHg in mean arterial pressure (MAP). The chronic carotid artery adaptations were simulated based on the hypothesis that the carotid artery will remodel wall-cross sectional area to maintain mechanical homeostasis.Results:A 6% increase in smooth muscle tone acutely decreased carotid pulse wave velocity from 6.89 +/- 1.24 m/s to 5.83 +/- 1.73 m/s, and a 15 mmHg decrease in MAP decreased carotid pulse wave velocity to 6.17 +/- 1.23 m/s. A 6% increase in smooth muscle tone acutely decreased wall stress from 76.2 +/- 12.3 to 64.2 +/- 10.4 kPa, and a 15 mmHg decrease in MAP decreased wall stress to 60.6 +/- 10.7 kPa. A 6% increase in smooth muscle tone chronically decreased wall cross-sectional area from 18.3 +/- 5.4 to 15.2 +/- 4.9 mm(2,) and a 15 mmHg decrease in MAP decreased wall cross-sectional area to 14.3 +/- 4.6 mm(2).Conclusion:In participant-specific simulation, increasing smooth muscle tone can have a stronger or equivalent effect on carotid artery mechanics compared with decreasing blood pressure. Increasing central arterial smooth muscle tone may be a novel therapeutic target to improve central arterial dysfunction in older, hypertensive adults and should be a focus of future research

Do children with autism perceive second-order relational features? The case of the Thatcher illusion

Background:This study presents two experiments that investigated whether children with autism were susceptible to the Thatcher illusion. Perception of the Thatcher illusion requires being able to compute second-order configural relations for facial stimuli. Method:In both experiments children with autism were matched for non-verbal and verbal ability with a group of children with moderate (non-specific) mental retardation (MLD) and a group of typically developing children respectively. Participants were asked to detect the ‘unusual’ face in a two-alternative-forced-choice version of the Margaret Thatcher illusion with grey-scale (Experiment 1) and monochrome ‘Mooney’ face images (Experiment 2). In Experiment 1 participants also performed a control task where buildings had been doctored in the same way as the facial stimuli. Results:Children with autism were as susceptible to the Thatcher illusion as both control groups, in terms of accuracy and reaction time to make decisions about which face was unusual. Children with autism performed more accurately than children with MLD in the buildings task. Conclusion:Children with autism are able to compute second-order configural features in faces and exhibit no difference in face processing, relative to appropriate control groups