An investigation into the relationship between simple practice exercises in written recall and increased ability in unaided oral recall.

Thesis (Ed.M.)--Boston Universit

CONDITIONAL REGRESSION MODELS FOR TRANSIENT STATE SURVIVAL ANALYSIS

Survival models are important tools for the analysis of data when a disease event occurs in time and subjects are lost to follow-up. Many models, however, can also be adapted for use when an event is characterized by transitions through Intermediate states of disease with increasing severity. In this presentation, such adaptations will be demonstrated for a class of conditional regression models for the analysis of transient state events occurring among grouped event times. The type of conditioning that will be described is useful in providing comparisons of specific disease states and an assessment of transition-dependent risk factor effects. An example will be given based on the Framingham Heart Study

Slinky Inflation

We present a new approach to quintessential inflation, in which both dark energy and inflation are explained by the evolution of a single scalar field. We start from a simple scalar potential with both oscillatory and exponential behavior. We employ the conventional reheating mechanism of new inflation, in which the scalar decays to light fermions with a decay width that is proportional to the scalar mass. Because our scalar mass is proportional to the Hubble rate, this gives adequate reheating at early times while shutting off at late times to preserve quintessence and satisfy nucleosynthesis constraints. We discuss a simple model which solves the horizon, flatness, and "why now" problems. Without any additional tuning of parameters, this model satisfies all constraints from CMB, large scale structure, and nucleosynthesis. The predictions for the inflationary spectral indices are n_S = n_T = 1. In this model we are currently beginning the third cosmic epoch of accelerated expansion.Comment: 5 pages, 2 color figures, 1 tabl

A Conical Tear Drop as a Vacuum-Energy Drain for the Solution of the Cosmological Constant Problem

We propose a partial solution to the cosmological constant problem by using the simple observation that a three-brane in a six-dimensional bulk is flat. A model is presented in which Standard Model vacuum energy is always absorbed by the transverse space. The latter is a tear-drop like space with a conical singularity, which preserves bulk supersymmetry and gives rise to conventional macroscopic 4D gravity with no cosmological constant. Its cone acts like a drain, depleting vacuum energy from the three-brane to the tear drop increasing its volume. We stress that although gravity is treated classically, Standard Model is handled quantum-field theoretically and the model is robust against Standard Model corrections and particular details. The price paid is the presence of boundaries which are nevertheless physically harmless by appropriate boundary conditions.Comment: 14 pages, 1 fig. As appeared in Phys. lett.

Massive, massless and ghost modes of gravitational waves from higher-order gravity

We linearize the field equations for higher order theories that contain scalar invariants other than the Ricci scalar. We find that besides a massless spin-2 field (the standard graviton), the theory contains also spin-0 and spin-2 massive modes with the latter being, in general, ghost modes. Then, we investigate the possible detectability of such additional polarization modes of a stochastic gravitational wave by ground-based and space interferometric detectors. Finally, we extend the formalism of the cross-correlation analysis, including the additional polarization modes, and calculate the detectable energy density of the spectrum for a stochastic background of the relic gravity waves that corresponds to our model. For the situation considered here, we find that these massive modes are certainly of interest for direct detection by the LISA experiment.Comment: 11 pages, 3 figure

New hairy black holes with negative cosmological constant

Black hole solutions with nonspherical event horizon topology are shown to exist in an Einstein-Yang-Mills theory with negative cosmological constant. The main characteristics of the solutions are presented and differences with respect to the spherically symmetric case are studied. The stability of these configurations is also addressed.Comment: 14 pages, 6 Encapsulated PostScript figures, references adde

Arbitrary Spin Representations in de Sitter from dS/CFT with Applications to dS Supergravity

We present a simple group representation analysis of massive, and particularly ``partially massless'', fields of arbitrary spin in de Sitter spaces of any dimension. The method uses bulk to boundary propagators to relate these fields to Euclidean conformal ones at one dimension lower. These results are then used to revisit an old question: can a consistent de Sitter supergravity be constructed, at least within its intrinsic horizon?Comment: 19 pages LaTex, references added, version to appear Nucl. Phys.

Selftuning and its footprints

We re-consider the self tuning idea in brane world models of finite volume. We notice that in a large class of self tuning models, the four dimensional physics is sensitive to the vacuum energy on the brane. In particular the compactification volume changes each time the tension of the brane is modified: consequently, observable constants, as the effective Planck mass or masses of matter fields, change as well. We notice that the self tuning mechanism and the stabilization mechanism of the size of the extra dimensions are generically in apparent conflict. We focus on a self tuning model in six spacetime dimensions to analyze how the above considerations are explicitely realized.Comment: 28 pages, JHEP style. v2: typos corrected and references added. Published versio

Matching the observed cosmological constant with vacuum energy density in AdS

We calculate the vacuum energy density by taking account of different massive scalar fields in AdS spacetime. It is found that the mass spectrum of a scalar field in AdS spacetime is discrete because of a natural boundary condition. The results match well with the observed cosmological constant.Comment: 9 pages, no figures, Late

On the General Kerr/CFT Correspondence in Arbitrary Dimensions

We study conformal symmetries on the horizon of a general stationary and axisymmetric black hole. We find that there exist physically reasonable boundary conditions that uniquely determine a set of symmetry generators, which form one copy of the Virasoro algebra. For extremal black holes, Cardy's formula reproduces exactly the Bekenstein-Hawking entropy.Comment: 17 page