Robust, data-driven inference in non-linear cosmostatistics

We discuss two projects in non-linear cosmostatistics applicable to very large surveys of galaxies. The first is a Bayesian reconstruction of galaxy redshifts and their number density distribution from approximate, photometric redshift data. The second focuses on cosmic voids and uses them to construct cosmic spheres that allow reconstructing the expansion history of the Universe using the Alcock-Paczynski test. In both cases we find that non-linearities enable the methods or enhance the results: non-linear gravitational evolution creates voids and our photo-z reconstruction works best in the highest density (and hence most non-linear) portions of our simulations.Comment: 14 pages, 10 figures. Talk given at "Statistical Challenges in Modern Astronomy V," held at Penn Stat

Hadley V. Baxendale: Still Crazy After All These Years? Panel Discussion

The following discussion about Hadley v. Baxendale took place on June 8, 2004, at the Conference on The Common Law of Contracts as a World Force in Two Ages of Revolution, held at the Oxstalls Campus of the University of Gloucestershire, in Gloucester, England. The Conference marked the 150th anniversary of Hadley. The following discussion was intended to be a free-ranging exploration of Hadley, its rule, its role in legal pedagogy, and its likely future

Recovering the intrinsic shape of early-type galaxies

We investigate how well the intrinsic shape of early-type galaxies can be recovered when both photometric and two-dimensional stellar kinematic observations are available. We simulate these observations with galaxy models that are representative of observed oblate fast-rotator to triaxial slow-rotator early-type galaxies. By fitting realistic triaxial dynamical models to these simulated observations, we recover the intrinsic shape (and mass-to-light ratio), without making additional (ad-hoc) assumptions on the orientation. For (near) axisymmetric galaxies the dynamical modelling can strongly exclude triaxiality, but the regular kinematics do not further tighten the constraint on the intrinsic flattening significantly, so that the inclination is nearly unconstrained above the photometric lower limit even with two-dimensional stellar kinematics. Triaxial galaxies can have additional complexity in both the observed photometry and kinematics, such as twists and (central) kinematically decoupled components, which allows the intrinsic shape to be accurately recovered. For galaxies that are very round or show no significant rotation, recovery of the shape is degenerate, unless additional constraints such as from a thin disk are available.Comment: 12 pages, 7 figures, PDFLaTeX, accepted to MNRAS, minor revision

A Bogomol`nyi equation for intersecting domain walls

We argue that the Wess-Zumino model with quartic superpotential admits static solutions in which three domain walls intersect at a junction. We derive an energy bound for such junctions and show that configurations saturating it preserve 1/4 supersymmetry.Comment: 4 pages revtex. No figures. Revised version to appear in Physical Review Letters includes discussion of the supersymmetry algebr

Cosmic Shear with Next Generation Redshift Surveys as a Cosmological Probe

The expansion of the universe causes spacetime curvature, distinguishing between distances measured along and transverse to the line of sight. The ratio of these distances, e.g. the cosmic shear distortion of a sphere defined by observations of large scale structure as suggested by Alcock & Paczynski, provides a method for exploring the expansion as a function of redshift. The theoretical sensitivity to cosmological parameters, including the dark energy equation of state, is presented. Remarkably, sensitivity to the time variation of the dark energy equation of state is best achieved by observations at redshifts z<1. While systematic errors greatly degrade the theoretical sensitivity, this probe may still offer useful parameter estimation, especially in complementarity with a distance measure like the Type Ia supernova method implemented by SNAP. Possible future observations of the Alcock-Paczynski distortion by the KAOS project on a 8 meter ground based telescope are considered.Comment: 6 pages, 8 figure

Cosmological perturbations on local systems

We study the effect of cosmological expansion on orbits--galactic, planetary, or atomic--subject to an inverse-square force law. We obtain the laws of motion for gravitational or electrical interactions from general relativity--in particular, we find the gravitational field of a mass distribution in an expanding universe by applying perturbation theory to the Robertson-Walker metric. Cosmological expansion induces an ($\ddot a/a) \vec r$ force where $a(t)$ is the cosmological scale factor. In a locally Newtonian framework, we show that the $(\ddot a/a) \vec r$ term represents the effect of a continuous distribution of cosmological material in Hubble flow, and that the total force on an object, due to the cosmological material plus the matter perturbation, can be represented as the negative gradient of a gravitational potential whose source is the material actually present. We also consider the effect on local dynamics of the cosmological constant. We calculate the perihelion precession of elliptical orbits due to the cosmological constant induced force, and work out a generalized virial relation applicable to gravitationally bound clusters.Comment: 10 page

Domain Wall Junctions are 1/4-BPS States

We study N=1 SUSY theories in four dimensions with multiple discrete vacua, which admit solitonic solutions describing segments of domain walls meeting at one-dimensional junctions. We show that there exist solutions preserving one quarter of the underlying supersymmetry -- a single Hermitian supercharge. We derive a BPS bound for the masses of these solutions and construct a solution explicitly in a special case. The relevance to the confining phase of N=1 SUSY Yang-Mills and the M-theory/SYM relationship is discussed.Comment: 18 pages, 4 figures, uses RevTeX. Brief comments concerning lattices of junctions added. Version to appear in Phys. Rev.

'The show must go on': Event dramaturgy as consolidation of community

Event dramaturgy and cultural performance have not been examined in the literature from a strategic standpoint of fostering the social value of events. Thus, the purpose of this study was to explore the case of the Water Carnival, a celebratory event in a rural community of Southwest Texas, demonstrating the essence of this event as a symbolic social space, wherein event participants instantiate a shared and valued sense of community. A hermeneutical approach was employed, interpreting the event and its symbolisms as a text, combined with findings from ethnographic fieldwork, including participant observation, in-depth interviews and analysis of archival documents. The study examines the ways that dramaturgy in the Water Carnival helps frame the ongoing public discourse for community improvement and enhances social capital. The implications of the study for social leverage of events are discussed. It is suggested that a foundation for strategic social planning is the understanding of events as symbolic social spaces and their embeddedness in community development, which can be accomplished when events are pertinent to public discourse, address community issues, represent an inclusive range of stakeholders, and promote cooperation