Parameterization of Dark-Energy Properties: a Principal-Component Approach

Considerable work has been devoted to the question of how to best parameterize the properties of dark energy, in particular its equation of state w. We argue that, in the absence of a compelling model for dark energy, the parameterizations of functions about which we have no prior knowledge, such as w(z), should be determined by the data rather than by our ingrained beliefs or familiar series expansions. We find the complete basis of orthonormal eigenfunctions in which the principal components (weights of w(z)) that are determined most accurately are separated from those determined most poorly. Furthermore, we show that keeping a few of the best-measured modes can be an effective way of obtaining information about w(z).Comment: Unfeasibility of a truly model-independent reconstruction of w at z>1 illustrated. f(z) left out, and w(z) discussed in more detail. Matches the PRL versio

Book Reviews

Management of Low Back Pain. Ed. by H. Carron and R. E. McLaughlin. Pp. xii + 246. Illusuated. £16,75. Boston: John Wright. 1982.Obesity and Leanness: Basic Aspects. By M. Stock and N. Romwell. Pp. 98. Illustrated. £10,00. London: John Libbey. 1982.Head and Neck Surgery: Indications, Techniques, Pitfalls, vo!. 3. Ed. by H. H. Naumann. Pp. xvi + 643. Illustrated. RI43,95. Philadelphia: W. B. Saunders. 1982.Manual ofClinical Nephrology. Ed. by D. P. Earle, F. del Greco, M. L. Levine and A. P. Saunders. Pp. xx + 585. Illustrated. Philadelphia: W. B. Saunders. 1982.Complications of Pediatric Surgery: Prevention and Management. By K. J. Welch. Pp. xiii + 468. Illustrated. RI09,75. Philadelphia: W. B. Saunders. 1982.Shoulder Surgery. Ed. by I. Bayley and L. Kesse!. Pp. xvi + 217 + index. Illustrated. DM 140,-. Berlin: Springer-Verlag. 1982.Management of Open Fractures and Their Complications (Saunders Monographs in Clinical Orthopaedics). 4th ed. By R. B. Gustilo. Pp. x + 211. Illustrated. R7l,95. Philadelphia: W. B. Saunders. 1982

The transformation of banking : what does it mean for rural economies?

Banks and banking ; Rural development ; Bank mergers

Causes of the recent increase in bank security holdings

While bank security holdings have increased sharply in recent years, there is widespread disagreement about the significance of the increase. Some analysts argue that the increase is not a cause for concern because it results from temporary factors such as the business cycle. Others argue that the increase represents a permanent shift in bank portfolio preferences from loans to securities, which could cause banks to look more like mutual funds. If the latter view is true, small firms that rely on banks for credit may be unable to fund new investment. Moreover, monetary policy may be less able to influence total spending in the economy by affecting bank lending.> Keeton seeks to determine how much of the surge in bank security holdings can be explained by temporary factors. He discusses possible explanations for the recent increase in bank security holdings and presents empirical evidence based on the aggregate behavior of bank portfolios over the previous 30 years. He concludes that more than half the increase in security holdings cannot be explained by temporary factors, suggesting that bank portfolio preferences may have permanently changed.Bank investments ; Banks and banking

Book Reviews

These are the book reviews from 1972