Hidden horizons in non-relativistic AdS/CFT

We study boundary Green's functions for spacetimes with non-relativistic scaling symmetry. For this class of backgrounds, scalar modes with large transverse momentum, or equivalently low frequency, have an exponentially suppressed imprint on the boundary. We investigate the effect of these modes on holographic two-point functions. We find that the boundary Green's function is generically insensitive to horizon features on small transverse length scales. We explicitly demonstrate this insensitivity for Lifshitz z=2, and then use the WKB approximation to generalize our findings to Lifshitz z>1 and RG flows with a Lifshitz-like region. We also comment on the analogous situation in Schroedinger spacetimes. Finally, we exhibit the analytic properties of the Green's function in these spacetimes.Comment: Abstract and Introduction updated, typos correcte

Naive Noncommutative Blowing Up

Let B(X,L,s) be the twisted homogeneous coordinate ring of an irreducible variety X over an algebraically closed field k with dim X > 1. Assume that c in X and s in Aut(X) are in sufficiently general position. We show that if one follows the commutative prescription for blowing up X at c, but in this noncommutative setting, one obtains a noncommutative ring R=R(X,c,L,s) with surprising properties. In particular: (1) R is always noetherian but never strongly noetherian. (2) If R is generated in degree one then the images of the R-point modules in qgr(R) are naturally in (1-1) correspondence with the closed points of X. However, both in qgr(R) and in gr(R), the R-point modules are not parametrized by a projective scheme. (3) qgr R has finite cohomological dimension yet H^1(R) is infinite dimensional. This gives a more geometric approach to results of the second author who proved similar results for X=P^n by algebraic methods.Comment: Latex, 42 page

Universal features of Lifshitz Green's functions from holography

We examine the behavior of the retarded Green's function in theories with Lifshitz scaling symmetry, both through dual gravitational models and a direct field theory approach. In contrast with the case of a relativistic CFT, where the Green's function is fixed (up to normalization) by symmetry, the generic Lifshitz Green's function can a priori depend on an arbitrary function $\mathcal G(\hat\omega)$, where $\hat\omega=\omega/|\vec k|^z$ is the scale-invariant ratio of frequency to wavenumber, with dynamical exponent $z$. Nevertheless, we demonstrate that the imaginary part of the retarded Green's function (i.e. the spectral function) of scalar operators is exponentially suppressed in a window of frequencies near zero. This behavior is universal in all Lifshitz theories without additional constraining symmetries. On the gravity side, this result is robust against higher derivative corrections, while on the field theory side we present two $z=2$ examples where the exponential suppression arises from summing the perturbative expansion to infinite order.Comment: 32 pages, 4 figures, v2: reference added, v3: fixed bug in bibliograph

The Association Between Self-Rated Mental Health Status and Total Health Care Expenditure: A Cross-Sectional Analysis of a Nationally Representative Sample

Both clinical diagnoses and self-rated measures of mental illness are associated with a variety of outcomes, including physical well-being, health utilization, and expenditure. However, much of current literature primarily utilizes clinically diagnosed data. This cross-sectional study explores the impact of mental illness and health care expenditure using 2 self-rated measures: self-rated measured of perceived mental health status (SRMH) and Kessler Screening Scale for Psychological Distress (K6). Data from the 2011 Medical Expenditure Panel Survey Household Component, a nationally representative sample of noninstitutionalized individuals (n = 18,295), were analyzed using bivariate χ2 tests and a 2-part model (logistics regression and generalized linear model regression for the first and second stages, respectively). Although predictive of any health expenditure, SRMH alone was not highly predictive of the dollar value of that health expenditure conditional on any spending. By comparison, the K6 measure was significantly and positively associated with the probability of any health expenditure as well as the dollar value of that spending. Taken together, both the K6 and SRMH measures suggest a positive relationship between poor mental health and the probability of any health expenditure and total expenditure conditional on any spending, even when adjusting for other confounding factors such as race/ethnicity, sex, age, educational attainment, insurance status, and some regional characteristics. Our results suggest that psychological distress and SRMH may represent potential pathways linking poor mental health to increased health care expenditure. Further research exploring the nuances of these relationships may aid researchers, practitioners, and policy makers in addressing issues of inflated health care expenditure in populations at risk for poor mental health

ARAPAHO PRAIRIE, Arthur County, Nebraska: Approximate AP Grid for GIS

Grid map of field sites at Arapaho Prairie in Arthur County, Nebraska. Scale 1 5/16 = 1/4 mile. Shows permanently marked vegetation quadrats, blowouts and ravine washouts, roads, and 100\u27 contour intervals. Part of the map was destroyed by mice. What remains of the map as of 2013 is shown