Shot Noise in Digital Holography

We discuss on noise in heterodyne holography in an off-axis configuration. We show that, for a weak signal, the noise is dominated by the shot noise on the reference beam. This noise corresponds to an equivalent noise on the signal beam of one photoelectron per pixel, for the whole sequence of images used to build the digital hologram

Natural Neutrino Mass Matrix

Naturalness of the neutrino mass hierarchy and mixing is studied. First we select among 12 neutrino mixing patterns a few patterns, which could form the natural neutrino mass matrix. Further we show that if the Dirac neutrino mass matrix is taken as the natural one in the quark sector, then only two mixing patterns without the large mixing lead to the natural right-handed Majorana mass matrix. The rest of the chosen patterns with three degenerate mass solution lead to the unnatural right-handed Majorana mass matrix in the see-saw mechanism. Notice however, that for the chosen two natural patterns there could be a huge mass hierarchy such as ${\cal O}(10^{4\sim 6})$ in order to reproduce the inverse mass hierarchy of the light neutrinos.Comment: 31 pages, LaTex file, no figures, arguments made more clear, main conclusions unchanged, version accepted for publication in PRD Reort-no: Lund-Mph-97/14 Revise

The Danger of Having All Your Eggs in One Basket—Winter Crash of the Re-Introduced Przewalski's Horses in the Mongolian Gobi

Large mammals re-introduced into harsh and unpredictable environments are vulnerable to stochastic effects, particularly in times of global climate change. The Mongolian Gobi is home to several rare large ungulates such as re-introduced Przewalski's horses (Equus ferus przewalskii) and Asiatic wild asses (Equus hemionus), but also to a millennium-old semi-nomadic livestock herding culture

Information Counselling

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Low Latency Asynchronous Optical Bus for Distributed Multiprocessor Systems

: We present an investigation on how to reduce the internode communication latency in distributed multiprocessor systems. The strategy consists of replacing the "store and forward" mechanism that is usually carried out on each electronic node by a free diffusion of optical packets along an optical bus. No routing, no extraction of optical packets and no access arbitration into the bus are needed. Intermediate nodes between two processors engaged in a communication are optically transparent. These specifications considerably simplify the optoelectronic interface of the node and reduce the latency of communication. In the asynchronous operation mode that we consider, each node multiplexer inserts on the fly optical packets into the bus. The optical demultiplexer identifies the packet destination address before transmitting the data to the node electronics. The key point is to make the intranode latency shorter than the internode propagation time to attain a network latency close to ulti..