Indications of a Metallic Antiferromagnetic Phase in the 2 Dimensional U−t−t′U-t-t' Model

We present mean-field and quantum Monte Carlo results that suggest the existence of an itinerant antiferromagnetic ground state in the half-filled $U-t-t'$ model in two dimensions. In particular, working at $t'/t=-0.2$ we found that antiferromagnetic long range order develops at $U_{c_1}/t\approx 2.5$, while a study of the density of states $N(\omega)$ and the response to an external magnetic field indicates that the system becomes insulating at a larger coupling $4<U_{c_2}/t<6$.Comment: 4 pages, RevTex 3.0, 5 figures embedded in the text, modifications in the text, as well as added data to Fig.

Detection, attribution, and sensitivity of trends toward earlier streamflow in the Sierra Nevada

Observed changes in the timing of snowmelt dominated streamflow in the western United States are often linked to anthropogenic or other external causes. We assess whether observed streamflow timing changes can be statistically attributed to external forcing, or whether they still lie within the bounds of natural (internal) variability for four large Sierra Nevada (CA) basins, at inflow points to major reservoirs. Streamflow timing is measured by “center timing” (CT), the day when half the annual flow has passed a given point. We use a physically based hydrology model driven by meteorological input from a global climate model to quantify the natural variability in CT trends. Estimated 50-year trends in CT due to natural climate variability often exceed estimated actual CT trends from 1950 to 1999. Thus, although observed trends in CT to date may be statistically significant, they cannot yet be statistically attributed to external influences on climate. We estimate that projected CT changes at the four major reservoir inflows will, with 90% confidence, exceed those from natural variability within 1–4 decades or 4–8 decades, depending on rates of future greenhouse gas emissions. To identify areas most likely to exhibit CT changes in response to rising temperatures, we calculate changes in CT under temperature increases from 1 to 5°. We find that areas with average winter temperatures between −2°C and −4°C are most likely to respond with significant CT shifts. Correspondingly, elevations from 2000 to 2800 m are most sensitive to temperature increases, with CT changes exceeding 45 days (earlier) relative to 1961–1990

Criminal Cases Gone Paperless : Hanging With the Wrong Crowd

This article explores issues concerning electronic discovery (e-discovery), its association with ESI, and how it impacts criminal litigation

High Resolution Nature Runs and the Big Data Challenge

NASA's Global Modeling and Assimilation Office at Goddard Space Flight Center is undertaking a series of very computationally intensive Nature Runs and a downscaled reanalysis. The nature runs use the GEOS-5 as an Atmospheric General Circulation Model (AGCM) while the reanalysis uses the GEOS-5 in Data Assimilation mode. This paper will present computational challenges from three runs, two of which are AGCM and one is downscaled reanalysis using the full DAS. The nature runs will be completed at two surface grid resolutions, 7 and 3 kilometers and 72 vertical levels. The 7 km run spanned 2 years (2005-2006) and produced 4 PB of data while the 3 km run will span one year and generate 4 BP of data. The downscaled reanalysis (MERRA-II Modern-Era Reanalysis for Research and Applications) will cover 15 years and generate 1 PB of data. Our efforts to address the big data challenges of climate science, we are moving toward a notion of Climate Analytics-as-a-Service (CAaaS), a specialization of the concept of business process-as-a-service that is an evolving extension of IaaS, PaaS, and SaaS enabled by cloud computing. In this presentation, we will describe two projects that demonstrate this shift. MERRA Analytic Services (MERRA/AS) is an example of cloud-enabled CAaaS. MERRA/AS enables MapReduce analytics over MERRA reanalysis data collection by bringing together the high-performance computing, scalable data management, and a domain-specific climate data services API. NASA's High-Performance Science Cloud (HPSC) is an example of the type of compute-storage fabric required to support CAaaS. The HPSC comprises a high speed Infinib and network, high performance file systems and object storage, and a virtual system environments specific for data intensive, science applications. These technologies are providing a new tier in the data and analytic services stack that helps connect earthbound, enterprise-level data and computational resources to new customers and new mobility-driven applications and modes of work. In our experience, CAaaS lowers the barriers and risk to organizational change, fosters innovation and experimentation, and provides the agility required to meet our customers' increasing and changing need

Quarterly Economic Commentary, Winter 2015

The Irish economy is set to register a substantial growth performance in 2015 with the expected 6.7 per cent year-on-year increase in output unsurpassed since 2005. While the Irish recovery has benefitted from a weak Euro and strong economic performance amongst key trading partners, it is noteworthy, particularly given a variety of countervailing factors; the ongoing difficulties in the Irish financial sector, the related low levels of credit extended, the persistent high levels of private sector debt and the anaemic performance of many European economies since 2010

Quarterly Economic Commentary, Autumn 2015

The pace of the Irish recovery would appear to be increasing; the latest National Accounts indicate that output in the economy grew by over 5 per cent in 2014 and by almost 2 per cent in Q2 2015 alone. Use of the nowcasting model (summarised in the Appendix) suggests the economy is growing through Q3 by approximately 1.5 per cent per quarter in 2015. Accordingly, we now update our forecast for GDP in 2015 to 6 per cent, with GNP expected to grow marginally less at 5.9 per cent. One significant consequence of this is that Irish income per capita, which fell significantly post-2007, is now back to the peak level prior to the financial crisis

Quarterly Economic Commentary Special Articles, Winter 2015

The Irish economy is set to register a substantial growth performance in 2015 with the expected 6.7 per cent year-on-year increase in output unsurpassed since 2005. While the Irish recovery has benefitted from a weak Euro and strong economic performance amongst key trading partners, it is noteworthy, particularly given a variety of countervailing factors; the ongoing difficulties in the Irish financial sector, the related low levels of credit extended, the persistent high levels of private sector debt and the anaemic performance of many European economies since 2010