Quantum paramagnetic ground states on the honeycomb lattice and field-induced transition to N\'eel order

Motivated by recent experiments on Bi$_3$Mn$_4$O$_{12}$(NO$_3$), and a broader interest arising from numerical work on the honeycomb lattice Hubbard model, we have studied the effect of a magnetic field on honeycomb lattice spin models with quantum paramagnetic ground states. For a model with frustrating second-neighbor exchange, $J_2$, we use a Lindemann-like criterion within spin wave theory to show that N\'eel order melts beyond a critical $J_2$. The critical $J_2$ increases with a magnetic field, implying the existence of a field-induced paramagnet-N\'eel transition over a range of $J_2$. We also study bilayer model using a spin-$S$ generalization of bond operator mean field theory. We show that there is a N\'eel-dimer transition for various spin values with increasing bilayer coupling, and that the resulting interlayer dimer state undergoes a field induced transition into a state with transverse N\'eel order. Finally, we study a spin-3/2 model which interpolates between the Heisenberg model and the Affleck-Kennedy-Lieb-Tasaki (AKLT) parent Hamiltonian. Using exact diagonalization, we compute the fidelity susceptibility to locate the Neel-AKLT quantum critical point, obtain the spin gap of the AKLT parent Hamiltonian, and argue that AKLT state also undergoes field-induced Neel ordering.Comment: 8 pages, revised longer version of arXiv:1012.0316. Corrected factor of 2 error in Eq.[16], replotted Fig.[4] and revised the critical $J_c/J_1$ needed to stabilize interlayer dimer state. We thank S. V. Isakov for discussions which uncovered this erro

Load Balancing via Random Local Search in Closed and Open systems

In this paper, we analyze the performance of random load resampling and migration strategies in parallel server systems. Clients initially attach to an arbitrary server, but may switch server independently at random instants of time in an attempt to improve their service rate. This approach to load balancing contrasts with traditional approaches where clients make smart server selections upon arrival (e.g., Join-the-Shortest-Queue policy and variants thereof). Load resampling is particularly relevant in scenarios where clients cannot predict the load of a server before being actually attached to it. An important example is in wireless spectrum sharing where clients try to share a set of frequency bands in a distributed manner.Comment: Accepted to Sigmetrics 201

Enterprise Information Systems Integration and Business Process Improvement Initiative: An Empirical Study

Since the mid-and late 80\u27s, business process improvement (BPI) has become one of the leading methodologies to deliver corporations with high quality products and services. Businesses are seeking not simply to automate existing operations, but to improve and redesign business processes and capture customers\u27 expectations for products, and service delivery. Extensive communication and inter-connectivity arising from adoption of standards and integrated services digital networks (ISDN) has become a major force affectingbusinesses in fundamental ways (Madnick, 1990; Boar, 1993). The second avenue through which businesses are identifying new opportunities is the availability of databases (Madnick, 1990). By linking inter-organizational, inter-functional, and inter-personal levels of the processes through IS networks, businesses are not only automating their activities, they are also reshaping and improving their business processes (Hammer and Champy, 1993). By accessing enterprise-wise information from databases, IS integration is providing numerous opportunities to coordinate organizational activities by facilitating communication and information exchange across departments without the need to go up and down the vertical chain of command. The use of information networks to access relevant information from databases has been of enormous importance to eliminate duplicate activities, prevent errors from occurring, cycle time reduction in product development, and customer responsiveness (Davenport, 1993). The need of a well planned database management system is one of the important requirements for BPI. In most organizations, data architecture has evolved as a result of applications databases in various departments rather than as a well planned data management strategy. Therefore, the resolution of data management problems becomes quite difficult (Goodhue, Quillard, and Rockart, 1988). The access to timely, accurate and consistent information is crucial in business process improvement. IS integration, through communication networks and database systems, enables organizations to create and sustain process improvement through timely retrieval of consistent and accurate information. Process improvement can be measured by the extent desired specified results are produced right thefirst time (i.e., outcomes with zero defect), the extent various processes minimize the consumption of the business resources, and the extent business processes are easily modified to meet or exceed customers\u27 expectations for products and service delivery. The current study is aimed at developing and empirically testing the relationships between IS integration and BPI. As presently there are only a handful studies that empirically test the relationship between information systems and BPI, this study is an important step for furthering the scope of present stage of the IS literature

MARKETING CHARACTERISTICS ASSOCIATED WITH SEAFOOD COUNTERS IN GROCERY STORES

This study provides a benchmark analysis of seafood counter characteristics corresponding to the peaking of per capita seafood demand in the U.S. Logistic regression results show separate seafood counters are less likely in small stores, in rural stores, and in stores in low or medium income areas. Chain stores and stores with a significant number of non-white customers were more likely to have a seafood counter. Stores in the East South Central region were less likely, and stores in New England more likely, to have a seafood counter. The likelihood that stores will develop seafood counters was related to differences in sales volume, floor space, urban/rural location, income level of clients and regional location. Continuing innovations in marketing technology of seafood counters are likely to provide expanded marketing opportunities in the future.Marketing,

Signature of nearly icosahedral structures in liquid and supercooled liquid Copper

A growing body of experiments display indirect evidence of icosahedral structures in supercooled liquid metals. Computer simulations provide more direct evidence but generally rely on approximate interatomic potentials of unproven accuracy. We use first-principles molecular dynamics simulations to generate realistic atomic configurations, providing structural detail not directly available from experiment, based on interatomic forces that are more reliable than conventional simulations. We analyze liquid copper, for which recent experimental results are available for comparison, to quantify the degree of local icosahedral and polytetrahedral order