Inflation in the Postmodern Era

In this lecture I will review some recent progress in improving the accuracy of the calculation of density perturbations resulting from inflation.Comment: 21-page LaTeX file for proceedings of the Erice School ``Astrofundamental Physics.'' Four postscript figures, figi.ps (i=1 to 4), included using eps

Massive scalar fields in the early Universe

We discuss the role of gravitational excitons/radions in different cosmological scenarios. Gravitational excitons are massive moduli fields which describe conformal excitations of the internal spaces and which, due to their Planck-scale suppressed coupling to matter fields, are WIMPs. It is demonstrated that, depending on the concrete scenario, observational cosmological data set strong restrictions on the allowed masses and initial oscillation amplitudes of these particles.Comment: 6 pages, Latex2e, talk presented at the 1st International Workshop on Astronomy and Relativistic Astrophysics, 12-16 October, 2003, (IWARA2003), Olinda-PE, Brazi

Sterile neutrino dark matter in warped extra dimensions

We consider a (long-lived) sterile neutrino dark matter scenario in a five dimensional (5D) warped extra dimension model where the fields can live in the bulk, which is partly motivated from the absence of the absolutely stable particles in a simple Randall-Sundrum model. The dominant production of the sterile neutrino can come from the decay of the radion (the scalar field representing the brane separation) around the electroweak scale. The suppressions of the 4D parameters due to the warp factor and the small wave function overlaps in the extra dimension help alleviate the exceeding fine-tunings typical for a sterile neutrino dark matter scenario in a 4D setup.Comment: Typos corrected and references adde

Pseudo-Dirac Bino Dark Matter

While the bino-dominated lightest neutralino of the minimal supersymmetric Standard Model (MSSM) is an interesting and widely-studied candidate of the dark matter, the p-wave suppression of its annihilation cross section requires fine-tunings of the MSSM spectra to be consistent with WMAP observations. We propose pseudo-Dirac bino that arises in theories with D-type supersymmetry-breaking as an intriguing alternative candidate of dark matter. The pseudo-Dirac nature of the bino gives a natural mechanism of enhanced co-annihilation because these two states are degenerate in the absence of electroweak symmetry breaking. In addition, the lightest state can be consistent with limits of direct detection experiments because of the lack of vector interactions, as with the case of the MSSM bino.Comment: 18 pages, 2 figures, REVTEX, to be published in PRD, made minor changes and added comments to match the published versio

Early thermalization at RHIC

It is shown that recent RHIC data on hadron spectra and elliptic flow can be excellently reproduced within a hydrodynamic description of the collision dynamics, and that this provides strong evidence for rapid thermalization while the system is still in the quark-gluon plasma phase. But even though the hydrodynamic approach provides an impressive description of the single-particle momentum distributions, it fails to describe the two-particle momentum correlation (HBT) data for central Au+Au collisions at RHIC. We suggest that this is not likely to be repaired by further improvements in our understanding of the early collision stages, but probably requires a better modelling of the freeze-out process. We close with a prediction of the phases of the azimuthal oscillations of the HBT radii in noncentral collisions at RHIC.Comment: 12 pages, including 6 figures. Invited talk at the International Conference on "Statistical QCD", Bielefeld, August 26-30, 2001, to appear in the proceedings (F. Karsch and H. Satz, eds.) in Nucl. Phys.

Vision to reality: From Robert R. Wilson's frontier to Leon M. Lederman's Fermilab

This paper examines the roles of vision and leadership in creating and directing Fermi National Accelerator Laboratory from the late 1960s through the 1980s. The story divides into two administrations having different problems and accomplishments, that of Robert R. Wilson (1967-1978), which saw the transformation from cornfield to frontier physics facility, and that of Leon Max Lederman (1979-1989), in which the laboratory evolved into one of the world's major high-energy facilities. Lederman's pragmatic vision of a user-based experimental community helped him to convert the pioneering facility that Wilson had built frugally into a laboratory with a stable scientific, cultural, and funding environment