Acoustic Signatures in the Cosmic Microwave Background

We study the uniqueness and robustness of acoustic signatures in the cosmic microwave background by allowing for the possibility that they are generated by some as yet unknown source of gravitational perturbations. The acoustic {\it pattern} of peak locations and relative heights predicted by the standard inflationary cold dark matter model is essentially unique and its confirmation would have deep implications for the causal structure of the early universe. A generic pattern for isocurvature initial conditions arises due to backreaction effects but is not robust to exotic source behavior inside the horizon. If present, the acoustic pattern contains unambiguous information on the curvature of the universe even in the general case. By classifying the behavior of the unknown source, we determine the minimal observations necessary for robust constraints on the curvature. The diffusion damping scale provides an entirely model independent cornerstone upon which to build such a measurement. The peak spacing, if regular, supplies a precision test.Comment: 45pg. aaspp4, 14 figs. minor changes reflect published version; supporting material at http://www.sns.ias.edu/~wh

The man/machine interface in information retrieval: Providing access to the casual user

This study is concerned with the difficulties encountered by casual users wishing to employ Information Storage and Retrieval Systems. A casual user is defined as a professional who has neither time nor desire to pursue in depth the study of the numerous and varied retrieval systems. His needs for on-line search are only occasional, and not limited to any particular system. The paper takes a close look at the state of the art of research concerned with aiding casual users of Information Storage and Retrieval Systems. Current experiments such as LEXIS, CONIT, IIDA, CITE, and CCL are presented and discussed. Comments and proposals are offered, specifically in the areas of training, learning and cost as experienced by the casual user. An extensive bibliography of recent works on the subject follows the text

Tensor Anisotropies in an Open Universe

We calculate the anisotropies in the cosmic microwave background induced by long-wavelength primordial gravitational waves in a universe with negative spatial curvature, such as are produced in the ``open inflation'' scenario. The impact of these results on the COBE normalization of open models is discussed.Comment: 5pgs, 2 figs.; also avalable at http://www.sns.ias.edu/~whu, revision reflects ApJL published version, model dependence clarifie