Particle Dark Matter
  Several lines of evidence suggest that some of the dark matter may be non-baryonic: the non-detection of various plausible baryonic candidates for dark matter inferred, e.g., from galaxy rotation curves and from cluster of galaxy velocity dispersions, the need for non-baryonic dark matter for theoretical models of galaxy formation, and the large discrepancy between dynamical measurements implying $\Omega_0 > 0.2$ and the baryon abundance inferred from big bang nucleosynthesis, $\Omega_b h^2 = 0.015$. There are a number of well-motivated dark matter candidates: massive neutrinos, supersymmetric dark matter and ``invisible'' axions. Many of these dark matter candidates are potentially detectable by the current generation of dark matter experiments. 
David N. Spergel (Dept. of Astrophysical Sciences, Princeton   University)