Searches for Long-lived Particles at the Tevatron Collider

Several searches for long-lived particles have been performed using data from p-pbar collisions from Run II at the Tevatron. In most cases, new analysis techniques have been developed to carry out each search and/or estimate the backgrounds. These searches expand the discovery potential of the CDF and D0 experiments to new physics that may have been missed by traditional search techniques. This review discusses searches for (1) neutral, long-lived particles decaying to muons, (2) massive, neutral, long-lived particles decaying to a photon and missing energy, (3) stopped gluinos, and (4) charged massive stable particles. It summarizes some of the theoretical and experimental motivations for such searches.Comment: submitted to Mod. Phys. Lett.

Effects of speech rate modifications on phonatory acoustic outcomes in Parkinson’s disease

Speech rate reduction is a global speech therapy approach for speech deficits in Parkinson’s disease (PD) that has the potential to result in changes across multiple speech subsystems. While the overall goal of rate reduction is usually improvements in speech intelligibility, not all people with PD benefit from this approach. Speech rate is often targeted as a means of improving articulatory precision, though less is known about rate-induced changes in other speech subsystems that could help or hinder communication. The purpose of this study was to quantify phonatory changes associated with speech rate modification across a broad range of speech rates from very slow to very fast in talkers with and without PD. Four speaker groups participated: younger and older healthy controls, and people with PD with and without deep brain stimulation of the subthalamic nucleus (STN-DBS). Talkers read aloud standardized sentences at 7 speech rates elicited using magnitude production: habitual, three slower rates, and three faster rates. Acoustic measures of speech intensity, cepstral peak prominence, and fundamental frequency were measured as a function of speech rate and group. Overall, slower rates of speech were associated with differential effects on phonation across the four groups. While all talkers spoke at a lower pitch in slow speech, younger talkers showed increases in speech intensity and cepstral peak prominence, while talkers with PD and STN-DBS showed the reverse pattern. Talkers with PD without STN-DBS and older healthy controls behaved in between these two extremes. At faster rates, all groups uniformly demonstrated increases in cepstral peak prominence. While speech rate reductions are intended to promote positive changes in articulation to compensate for speech deficits in dysarthria, the present results highlight that undesirable changes may be invoked across other subsystems, such as at the laryngeal level. In particular, talkers with STN-DBS, who often demonstrate speech deterioration following DBS surgery, demonstrated more phonatory detriments at slowed speech rates. Findings have implications for speech rate candidacy considerations and speech motor control processes in PD

Magnetically Controlled Accretion Flows onto Young Stellar Objects

(abridged) Accretion from disks onto young stars is thought to follow magnetic field lines from the inner disk edge to the stellar surface. The accretion flow thus depends on the geometry of the magnetic field. This paper extends previous work by constructing a collection of orthogonal coordinate systems, including the corresponding differential operators, where one coordinate traces the magnetic field lines. This formalism allows for an (essentially) analytic description of the geometry and the conditions required for the flow to pass through sonic points. Using this approach, we revisit the problem of magnetically controlled accretion flow in a dipole geometry, and then generalize the treatment to consider magnetic fields with multiple components, including dipole, octupole, and split monopole contributions. This approach can be generalized further to consider more complex magnetic field configurations. Observations indicate that accreting young stars have substantial dipole and octupole components, and that accretion flow is transonic. If the effective equation of state for the fluid is too stiff, the flow cannot pass smoothly through the sonic points in steady state. For a multipole field of order \ell, we derive a constraint on the polytropic index, n>\ell+3/2, required for steady transonic flow to reach free-fall velocities. For octupole fields, inferred on surfaces of T Tauri stars, n>9/2, so that the flow must be close to isothermal. The inclusion of octupole field components produces higher densities at the stellar surface and smaller hot spots, which occur at higher latitudes; the magnetic truncation radius is also modified. This contribution thus increases our understanding of magnetically controlled accretion for young stellar objects and can be applied to a variety of additional astrophysical problems.Comment: 50 pages, 8 figures, accepted to Ap

Natural Supergravity inflation

We identify a new mechanism in supergravity theories which leads to successful inflation without any need for fine tuning. The simplest model yields a spectrum of density fluctuations tilted away from scale-invariance and negligible gravitational waves. We demonstrate that this is consistent with the observed large-scale structure for a cold dark matter dominated, critical density universe. The model can be tested through measurements of microwave background anisotropy on small angular scales.Comment: 14 pages (revtex) including 3 figures (epsf); Minor changes to Introduction and discussion and modified Figure 1; to appear in Phys. Lett. B; Postscript also available from ftp://ftp.physics.ox.ac.uk/pub/local/users/sarkar/SugraInfl.ps.g

Degenerate dispersive equations arising in the study of magma dynamics

An outstanding problem in Earth science is understanding the method of transport of magma in the Earth's mantle. Models for this process, transport in a viscously deformable porous media, give rise to scalar degenerate, dispersive, nonlinear wave equations. We establish a general local well-posedness for a physical class of data (roughly $H^1$) via fixed point methods. The strategy requires positive lower bounds on the solution. This is extended to global existence for a subset of possible nonlinearities by making use of certain conservation laws associated with the equations. Furthermore, we construct a Lyapunov energy functional, which is locally convex about the uniform state, and prove (global in time) nonlinear dynamic stability of the uniform state for any choice of nonlinearity. We compare the dynamics to that of other problems and discuss open questions concerning a larger range of nonlinearities, for which we conjecture global existence.Comment: 27 Pages, 7 figures are not present in this version. See http://www.columbia.edu/~grs2103/ for a PDF with figures. Submitted to Nonlinearit

Identification and Development of User Requirements to Support Robust Corridor Investment Models

The purpose of the project was to develop useable techniques to integrate a broader range of potential impacts of transportation investments into transportation planning and decision-making. The research project described in this report developed a multi-attribute framework that can be used to assist in organizing and synthesizing information to measure costs and benefits, both monetary and non-monetary, of highway corridor investments. A modular approach was taken to developing individual techniques to quantify the potential impacts that could be utilized within the framework. The framework is flexible enough to accommodate the incorporation of additional techniques over time. To determine the range of potential impacts to consider, the values and needs of various stakeholders in highway corridors were taken into account and incorporated into variables, or indicators, to be used in a comprehensive system for evaluating impacts, costs, and benefits. Example techniques include a consideration and demonstration of the utility of geographic information systems (GIS) to organize data for use with the hedonic land valuation method. A prediction map was generated from this process, indicating the price consumers are willing to pay for a house in relation to its location with respect to highway corridors. This information is useful in analyzing the impact of competing corridor alternatives. In order to measure other indicators, the project also assessed the utility of high-resolution satellite remote sensing (RS) image data to provide highly accurate inputs necessary for economic models and as a means of measuring success after investments have been made. A methodology was developed to identify commercial and industrial origins and destinations from impervious surfaces. This, in turn, was translated into a calculation of average travel distances that could be used to quantify accessibility impacts associated with corridor alternatives. Remote sensing and GIS were assessed because of the spatial nature of transportation investments and their potential as a measuring tool for the transportation indicators. This multi-attribute framework is consistent with the Missouri Department of Transportation\u27s (MoDOT\u27s) overall planning direction of including the perspectives of more individuals/groups and potential impacts in decision making. This overall planning direction is seen in the Planning Framework and the Long-Range Transportation Plan (LRTP)

A Century of Cosmology

In the century since Einstein's anno mirabilis of 1905, our concept of the Universe has expanded from Kapteyn's flattened disk of stars only 10 kpc across to an observed horizon about 30 Gpc across that is only a tiny fraction of an immensely large inflated bubble. The expansion of our knowledge about the Universe, both in the types of data and the sheer quantity of data, has been just as dramatic. This talk will summarize this century of progress and our current understanding of the cosmos.Comment: Talk presented at the "Relativistic Astrophysics and Cosmology - Einstein's Legacy" meeting in Munich, Nov 2005. Proceedings will be published in the Springer-Verlag "ESO Astrophysics Symposia" series. 10 pages Latex with 2 figure

Gaudin Models and Bending Flows: a Geometrical Point of View

In this paper we discuss the bihamiltonian formulation of the (rational XXX) Gaudin models of spin-spin interaction, generalized to the case of sl(r)-valued spins. In particular, we focus on the homogeneous models. We find a pencil of Poisson brackets that recursively define a complete set of integrals of the motion, alternative to the set of integrals associated with the 'standard' Lax representation of the Gaudin model. These integrals, in the case of su(2), coincide wih the Hamiltonians of the 'bending flows' in the moduli space of polygons in Euclidean space introduced by Kapovich and Millson. We finally address the problem of separability of these flows and explicitly find separation coordinates and separation relations for the r=2 case.Comment: 27 pages, LaTeX with amsmath and amssym