Dark Matter Candidates: A Ten-Point Test

An extraordinarily rich zoo of non-baryonic Dark Matter candidates has been proposed over the last three decades. Here we present a 10-point test that a new particle has to pass, in order to be considered a viable DM candidate: I.) Does it match the appropriate relic density? II.) Is it {\it cold}? III.) Is it neutral? IV.) Is it consistent with BBN? V.) Does it leave stellar evolution unchanged? VI.) Is it compatible with constraints on self-interactions? VII.) Is it consistent with {\it direct} DM searches? VIII.) Is it compatible with gamma-ray constraints? IX.) Is it compatible with other astrophysical bounds? X.) Can it be probed experimentally?Comment: 29 pages, 12 figure

Flow through a two-scale porosity material

Flow through a two-scale porous medium is here investigated by a unique comparison between simulations performed with computational fluid dynamics and the boundary element method with microparticle image velocimetry in model geometries. Copyright © 2009 A. G. Andersson et al

Ultralow noise, broadband phase-sensitive optical amplifiers, and their applications

Frequency nondegenerate phase-sensitive amplifiers (PSAs) have the potential to realize broadband and noiseless amplification. However, the rigorous requirement of phase-and wavelength-locking of the input waves has significantly hampered their progress. In this paper, we review recent research on this type of optical amplifier. This work is based on a copier-PSA scheme, which consists of a parametric phase-insensitive copier followed by one or more PSAs. Broadband gain and noise performance of a fiber-based nondegenerate PSA has been characterized, both theoretically and experimentally. A record-low 1.1 dB noise figure was measured at >26 dB gain, and a clear phase dependent gain was observed. Moreover, potential applications including phase noise squeezing and ultralow noise, multichannel and modulation-format-transparent linear amplification with up to 6dB link noise figure advantage over conventional EDFA-amplified links have been experimentally demonstrated. The prospects and practical challenges of this intriguing amplification technology are also discussed. © 2011 IEEE