On walls of marginal stability in N=2 string theories

We study the properties of walls of marginal stability for BPS decays in a class of N=2 theories. These theories arise in N=2 string compactifications obtained as freely acting orbifolds of N=4 theories, such theories include the STU model and the FHSV model. The cross sections of these walls for a generic decay in the axion-dilaton plane reduce to lines or circles. From the continuity properties of walls of marginal stability we show that central charges of BPS states do not vanish in the interior of the moduli space. Given a charge vector of a BPS state corresponding to a large black hole in these theories, we show that all walls of marginal stability intersect at the same point in the lower half of the axion-dilaton plane. We isolate a class of decays whose walls of marginal stability always lie in a region bounded by walls formed by decays to small black holes. This enables us to isolate a region in moduli space for which no decays occur within this class. We then study entropy enigma decays for such models and show that for generic values of the moduli, that is when moduli are of order one compared to the charges, entropy enigma decays do not occur in these models.Comment: 40 pages, 2 figure

Topological Strings and (Almost) Modular Forms

The B-model topological string theory on a Calabi-Yau threefold X has a symmetry group Gamma, generated by monodromies of the periods of X. This acts on the topological string wave function in a natural way, governed by the quantum mechanics of the phase space H^3(X). We show that, depending on the choice of polarization, the genus g topological string amplitude is either a holomorphic quasi-modular form or an almost holomorphic modular form of weight 0 under Gamma. Moreover, at each genus, certain combinations of genus g amplitudes are both modular and holomorphic. We illustrate this for the local Calabi-Yau manifolds giving rise to Seiberg-Witten gauge theories in four dimensions and local P_2 and P_1 x P_1. As a byproduct, we also obtain a simple way of relating the topological string amplitudes near different points in the moduli space, which we use to give predictions for Gromov-Witten invariants of the orbifold C^3/Z_3.Comment: 62 pages, 1 figure; v2: minor correction

Longitudinal Associations of Neighborhood Crime and Perceived Safety with Blood Pressure: The Multi-Ethnic Study of Atherosclerosis (MESA)

Background: High neighborhood crime and low perceptions of safety may influence blood pressure (BP) through chronic stress. Few studies have examined these associations using longitudinal data. Methods: We used longitudinal data from 528 participants of the Multi-Ethnic Study of Atherosclerosis (aged 45-84, nonhypertensive at baseline) who lived in Chicago, Illinois. We examined associations of changes in individual-level perceived safety, aggregated neighborhood-level perceived safety, and past-year rates of police-recorded crime in a 1, =, or = mile buffer per 1,000 population with changes in systolic and diastolic BPs using fixed-effects linear regression. BP was measured five times between 2000 and 2012 and was adjusted for antihypertensive medication use (+10 mm Hg added to systolic and +5 mm Hg added to diastolic BP for participants on medication). Models were adjusted for time-varying sociodemographic and healthrelated characteristics and neighborhood socioeconomic status. We assessed differences by sex. Results: A standard deviation increase in individual-level perceived safety was associated with a 1.54 mm Hg reduction in systolic BP overall (95% confidence interval [CI]: 0.25, 2.83), and with a 1.24 mm Hg reduction in diastolic BP among women only (95% CI: 0.37, 2.12) in adjusted models. Increased neighborhood-level safety was not associated with BP change. An increase in police-recorded crime was associated with a reduction in systolic and diastolic BPs among women only, but results were sensitive to neighborhood buffer size. Conclusions: Results suggest individual perception of neighborhood safety may be particularly salient for systolic BP reduction relative to more objective neighborhood exposures

Building a Better Racetrack

We find IIb compactifications on Calabi-Yau orientifolds in which all Kahler moduli are stabilized, along lines suggested by Kachru, Kallosh, Linde and Trivedi.Comment: 47 pages, 1 figure, harvmac (v2: added references, minor comments, v3: improved discussion of metastability and explicit flux vacua

Gravitational corrections in supersymmetric gauge theory and matrix models

Gravitational corrections in N=1 and N=2 supersymmetric gauge theories are obtained from topological string amplitudes. We show how they are recovered in matrix model computations. This provides a test of the proposal by Dijkgraaf and Vafa beyond the planar limit. Both, matrix model and topological string theory, are used to check a conjecture of Nekrasov concerning these gravitational couplings in Seiberg-Witten theory. Our analysis is performed for those gauge theories which are related to the cubic matrix model, i.e. pure SU(2) Seiberg-Witten theory and N=2 U(N) SYM broken to N=1 via a cubic superpotential. We outline the computation of the topological amplitudes for the local Calabi-Yau manifolds which are relevant for these two cases.Comment: 27 pages, one eps figur

Cross-over behaviour in a communication network

We address the problem of message transfer in a communication network. The network consists of nodes and links, with the nodes lying on a two dimensional lattice. Each node has connections with its nearest neighbours, whereas some special nodes, which are designated as hubs, have connections to all the sites within a certain area of influence. The degree distribution for this network is bimodal in nature and has finite variance. The distribution of travel times between two sites situated at a fixed distance on this lattice shows fat fractal behaviour as a function of hub-density. If extra assortative connections are now introduced between the hubs so that each hub is connected to two or three other hubs, the distribution crosses over to power-law behaviour. Cross-over behaviour is also seen if end-to-end short cuts are introduced between hubs whose areas of influence overlap, but this is much milder in nature. In yet another information transmission process, namely, the spread of infection on the network with assortative connections, we again observed cross-over behaviour of another type, viz. from one power-law to another for the threshold values of disease transmission probability. Our results are relevant for the understanding of the role of network topology in information spread processes.Comment: 12 figure

Associations of Neighborhood Crime and Safety and with Changes in Body Mass Index and Waist Circumference

Using data from the Multi-Ethnic Study of Atherosclerosis (MESA), we evaluated associations of neighborhood crime and safety with changes in adiposity (body mass index (BMI) and waist circumference). MESA is a longitudinal study of cardiovascular disease among adults aged 45-84 years at baseline in 2000-2002, from 6 US sites, with follow-up for MESA participants until 2012. Data for this study were limited to Chicago, Illinois, participants in the MESA Neighborhood Ancillary Study, for whom police-recorded crime data were available, and who had complete baseline data (n = 673). We estimated associations of individual-level safety, aggregated neighborhood-level safety, and police-recorded crime with baseline levels and trajectories of BMI and waist circumference over time using linear mixed modeling with random effects. We also estimated how changes in these factors related to changes in BMI and waist circumference using econometric fixed-effects models. At baseline, greater individual-level safety was associated with more adiposity. Increasing individual- and neighborhood-level safety over time were associated with decreasing BMI over the 10-year period, with a more pronounced effect observed in women for individual-level safety and men for neighborhood-level safety. Police-recorded crime was not associated with adiposity. Neighborhood-level safety likely influences adiposity change and subsequent cardiovascular risk in multiethnic populations

Notes on the algebraic curves in (p,q) minimal string theory

Loop amplitudes in (p,q) minimal string theory are studied in terms of the continuum string field theory based on the free fermion realization of the KP hierarchy. We derive the Schwinger-Dyson equations for FZZT disk amplitudes directly from the W_{1+\infty} constraints in the string field formulation and give explicitly the algebraic curves of disk amplitudes for general backgrounds. We further give annulus amplitudes of FZZT-FZZT, FZZT-ZZ and ZZ-ZZ branes, generalizing our previous D-instanton calculus from the minimal unitary series (p,p+1) to general (p,q) series. We also give a detailed explanation on the equivalence between the Douglas equation and the string field theory based on the KP hierarchy under the W_{1+\infty} constraints.Comment: 61 pages, 1 figure, section 2.5 and Appendix B added, references added, final version to appear in JHE

A Precious Bequest: Contemporary Research with the WPA-CCC Collections from Moundville, Alabama *

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72459/1/j.1749-6632.1981.tb28184.x.pd