Extended Equal Service and Differentiated Service Models for Peer-to-Peer File Sharing

Peer-to-Peer (P2P) systems have proved to be the most effective and popular file sharing applications in recent years. Previous studies mainly focus on the equal service and the differentiated service strategies when peers have no initial data before their download. In an upload-constrained P2P file sharing system, we model both the equal service process and the differentiated service process when peers' initial data distribution satisfies some special conditions, and also show how to minimize the time to get the file to any number of peers. The proposed models can reveal the intrinsic relations among the initial data amount, the size of peer set and the minimum last finish time. By using the models, we can also provide arbitrary degree of differentiated service to a certain number of peers. We believe that our analysis process and achieved theoretical results could provide fundamental insights into studies on bandwidth allocation and data scheduling, and can give helpful reference both for improving system performance and building effective incentive mechanism in P2P file sharing systems

Isospin-Violating Dark Matter Benchmarks for Snowmass 2013

Isospin-violating dark matter (IVDM) generalizes the standard spin-independent scattering parameter space by introducing one additional parameter, the neutron-to-proton coupling ratio f_n/f_p. In IVDM the implications of direct detection experiments can be altered significantly. We review the motivations for considering IVDM and present benchmark models that illustrate some of the qualitatively different possibilities. IVDM strongly motivates the use of a variety of target nuclei in direct detection experiments.Comment: LaTeX, 5 pages, 4 figures. v2: minor figure revision

Dark Matter-Motivated Searches for Exotic 4th Generation Quarks in Tevatron and Early LHC Data

We determine the prospects for finding dark matter at the Tevatron and LHC through the production of exotic 4th generation quarks T' that decay through T' \to t X, where X is dark matter. The resulting signal of t \bar{t} + \met has not previously been considered in searches for 4th generation quarks, but there are both general and specific dark matter motivations for this signal, and with slight modifications, this analysis applies to any scenario where invisible particles are produced in association with top quarks. Current direct and indirect bounds on such exotic quarks restrict their masses to be between 300 and 600 GeV, and the dark matter's mass may be anywhere below m_T'. We simulate the signal and main backgrounds with MadGraph/MadEvent-Pythia-PGS4. For the Tevatron, we find that an integrated luminosity of 20 fb^-1 will allow 3\sigma discovery up to m_T' = 400 GeV and 95% exclusion up to m_T' = 455 GeV. For the 10 TeV LHC with 300 pb^-1, the discovery and exclusion sensitivities rise to 490 GeV and 600 GeV. These scenarios are therefore among the most promising for dark matter at colliders. Perhaps most interestingly, we find that dark matter models that can explain results from the DAMA, CDMS and CoGeNT Collaborations can be tested with high statistical significance using data already collected at the Tevatron and have extraordinarily promising implications for early runs of the LHC.Comment: 22 pages; v2: additional discussion of relation to DAMA, CDMS, and CoGeNT results, references adde