Noise Correlations in one-dimensional systems of ultra-cold fermions

Time of flight images reflect the momentum distribution of the atoms in the trap, but the spatial noise in the image holds information on more subtle correlations. Using Bosonization, we study such noise correlations in generic one dimensional systems of ultra cold fermions. Specifically, we show how pairing as well as spin and charge density wave correlations may be identified and extracted from the time of flight images. These incipient orders manifest themselves as power law singularities in the noise correlations, that depend on the Luttinger parameters, which suggests a general experimental technique to obtain them.Comment: 5 pages, 3 figures. Added discussion on the visibility of noise correlation features for realistic condition

Branching processes, the max-plus algebra and network calculus

Branching processes can describe the dynamics of various queueing systems, peer-to-peer systems, delay tolerant networks, etc. In this paper we study the basic stochastic recursion of multitype branching processes, but in two non-standard contexts. First, we consider this recursion in the max-plus algebra where branching corresponds to finding the maximal offspring of the current generation. Secondly, we consider network-calculus-type deterministic bounds as introduced by Cruz, which we extend to handle branching-type processes. The paper provides both qualitative and quantitative results and introduces various applications of (max-plus) branching processes in queueing theory

Utilisation of native wildlife by Indigenous Australians: Commercial considerations

This paper is based on a submission to the Senate Rural and Regional Affairs and Transport References Committee Inquiry into the commercial use of Australian native wildlife. It uses secondary sources and is also based on primary research. - Indigenous Australians have a special interest in commercial utilisation of wildlife due to their subsistence activities, religious associations with many species, present and future rights to tracts of land under land rights legislation and, potentially, following the passage of the Native Title Act. - Indigenous people's interest is also based in their growing involvement in sustainable utilisation of species for ecotourism and their desire to become less economically dependent on government support. - Indigenous people desire input into species management to ensure maintenance of biodiversity. - Aboriginal people have few economic opportunities in remote communities and are seeking further commercial opportunities in wildlife enterprises. However, past experience of Indigenous enterprises is chequered due to locational, cultural and human capital constraints. - Marketing and other problems associated with wildlife products hamper present enterprises. There are few data on the impact of commercial utilisation or subsistence usage of species. The research recommends that: - In the best interests of commercial utilisation of wildlife in a sustainable manner, there is a need for an enhanced role for Indigenous interests in species management. This could be achieved through their Indigenous organisations and via joint management processes. This is necessary because many species are endemic to Aboriginal-owned land that accounts for 17 per cent of Australia. Some precedents exist in joint management of inhabited national parks particularly in the Northern Territory. - It is essential to achieve a balance between subsistence use, commercialisation and preservation of wildlife, taking into account possible tradeoffs with the commercial value of tourism based on the non-harvesting of species. Opportunities are greatest for Indigenous people when harvesting is from the wild, rather than by farming species. -Joint ventures, royalty arrangements, property rights in species and joint management plans also offer opportunities for Indigenous people to become involved in commercial utilisation and management of wildlife. - Given the limited economic opportunities of remote Aboriginal communities, there is a need to explore options to convert Indigenous leverage with respect to species to their advantage. If commercial wildlife use is to expand, it is important that Indigenous people have equal opportunities to participate in it, and that expansion by non-Indigenous interests does not hamper the subsistence and commercial options available to Indigenous people. Joint-venturing, possibly with non-Indigenous partners, is an important means that must be considered to enable Indigenous people to participate in the economic benefits from commercial utilisation of wildlife. - Another issue requiring investigation in the aftermath of native title legislation is whether there is a need (or statutory requirement) to recognise existing and potential Indigenous property rights in species. Indirect options to attract rents from utilisation of wildlife, either via direct involvement as joint venturers or as sellers of property rights in species, need to be assessed as a way to provide financial returns to Indigenous communities. -There is a need to recognise that from the Indigenous perspective, in some situations, subsistence utilisation of species may make greater economic sense than commercial utilisation. In other words, the 'outstation gate' market replacement value of species used for subsistence may exceed their monetary market price

Parasites Alter Community Structure

Parasites often play an important role in modifying the physiology and behavior of their hosts and may, consequently, mediate the influence hosts have on other components of an ecological community. Along the northern Atlantic coast of North America, the dominant herbivorous snail Littorina littorea structures rocky intertidal communities through strong grazing pressure and is frequently parasitized by the digenean trematode Cryptocotyle lingua. We hypothesized that the effects of parasitism on host physiology would induce behavioral changes in L. littorea, which in turn would modulate L. littorea\u27s influence on intertidal community composition. Specifically, we hypothesized that C. lingua infection would alter the grazing rate of L. littorea and, consequently, macroalgal communities would develop differently in the presence of infected versus uninfected snails. Our results show that uninfected snails consumed 40% more ephemeral macroalgal biomass than infected snails in the laboratory, probably because the digestive system of infected snails is compromised by C. lingua infection. In the field, this weaker grazing by infected snails resulted in significantly greater expansion of ephemeral macroalgal cover relative to grazing by uninfected snails. By decreasing the per-capita grazing rate of the dominant herbivore, C. lingua indirectly affects the composition of the macroalgal community and may in turn affect other species that depend on macroalgae for resources or habitat structure. In light of the abundance of parasites across systems, we suggest that, through trait-mediated indirect effects, parasites may be a common determinant of structure in ecological communities

Brownian Dynamics of a Sphere Between Parallel Walls

We describe direct imaging measurements of a colloidal sphere's diffusion between two parallel surfaces. The dynamics of this deceptively simple hydrodynamically coupled system have proved difficult to analyze. Comparison with approximate formulations of a confined sphere's hydrodynamic mobility reveals good agreement with both a leading-order superposition approximation as well as a more general all-images stokeslet analysis.Comment: 4 pages, 3 figures, REVTeX with PostScript figure

Equilibrium in size-based scheduling systems

Size-based scheduling is advocated to improve response times of small flows. While researchers continue to explore different ways of giving preferential treatment to small flows without causing starvation to other flows, little focus has been paid to the study of stability of systems that deploy size-based scheduling mechanisms. The question on stability arises from the fact that, users of such a system can exploit the scheduling mechanism to their advantage and split large flows into multiple small flows. Consequently, a large flow in the disguise of small flows, may get the advantage aimed for small flows. As the number of misbehaving users can grow to a large number, an operator would like to learn about the system stability before deploying size-based scheduling mechanism, to ensure that it won't lead to an unstable system. In this paper, we analyse the criteria for the existence of equilibria and reveal the constraints that must be satisfied for the stability of equilibrium points. Our study exposes that, in a two-player game, where the operator strives for a stable system, and users of large flows behave to improve delay, size-based scheduling doesn't achieve the goal of improving response time of small flows