Paolo Benettin; Scott W. Bailey; John L. Campbell; Mark B. Green; Andrea Rinaldo; Gene E. Likens; Kevin J. McGuire; Gianluca Botter
2015-01-01
We combine experimental and modeling results from a headwater catchment at the Hubbard Brook Experimental Forest (HBEF), New Hampshire, USA, to explore the link between stream solute dynamics and water age. A theoretical framework based on water age dynamics, which represents a general basis for characterizing solute transport at the catchment scale, is here applied to...
Salamander populations and biomass in the Hubbard Brook Experimental Forest, New Hampshire
Energy Technology Data Exchange (ETDEWEB)
Burton, T.M.; Likens, G.E.
1975-01-01
There were about 2950 salamanders per ha (1770 g/ha wet wt) in the Hubbard Brook Experimental Forest in New Hampshire. The terrestrial species, Plethodon cinereus, accounted for about 93.5% of the total biomass while the streamside species, Desmognathus fuscus, Eurycea bislineata and Gyrinophilus porphyriticus, accounted for the remaining 6.5%. Notophthalmus viridescens was present, but was rare and insignificant in the biomass calculations. The population size of salamanders at Hubbard Brook appears to be stable. The biomass of salamanders is about twice that of birds during the bird's peak (breeding) season and is about equal to the biomass of small mammals.
Rakesh Minocha; Stephanie Long; Palaniswamy Thangavel; Subhash C. Minocha; Christopher Eagar; Charles T. Driscoll
2010-01-01
Acidic deposition has caused a depletion of calcium (Ca) in the northeastern forest soils. Wollastonite (Ca silicate) was added to watershed 1 (WS1) at the Hubbard Brook Experimental Forest (HBEF) in 1999 to evaluate its effects on various functions of the HBEF ecosystem. The effects of Ca addition on foliar soluble (extractable in 5% HClO4) ions...
Long-term trends from ecosystem research at the Hubbard Brook Experimental Forest
John L. Campbell; Charles T. Driscoll; Christopher Eagar; Gene E. Likens; Thomas G. Siccama; Chris E. Johnson; Timothy J. Fahey; Steven P. Hamburg; Richard T. Holmes; Amey S. Bailey; Donald C. Buso
2007-01-01
Summarizes 52 years of collaborative, long-term research conducted at the Hubbard Brook (NH) Experimental Forest on ecosystem response to disturbances such as air pollution, climate change, forest disturbance, and forest management practices. Also provides explanations of some of the trends and lists references from scientific literature for further reading.
Water age and stream solute dynamics at the Hubbard Brook Experimental Forest (US)
Botter, Gianluca; Benettin, Paolo; McGuire, Kevin; Rinaldo, Andrea
2016-04-01
The contribution discusses experimental and modeling results from a headwater catchment at the Hubbard Brook Experimental Forest (New Hampshire, USA) to explore the link between stream solute dynamics and water age. A theoretical framework based on water age dynamics, which represents a general basis for characterizing solute transport at the catchment scale, is used to model both conservative and weathering-derived solutes. Based on the available information about the hydrology of the site, an integrated transport model was developed and used to estimate the relevant hydrochemical fluxes. The model was designed to reproduce the deuterium content of streamflow and allowed for the estimate of catchment water storage and dynamic travel time distributions (TTDs). Within this framework, dissolved silicon and sodium concentration in streamflow were simulated by implementing first-order chemical kinetics based explicitly on dynamic TTD, thus upscaling local geochemical processes to catchment scale. Our results highlight the key role of water stored within the subsoil glacial material in both the short-term and long-term solute circulation at Hubbard Brook. The analysis of the results provided by the calibrated model allowed a robust estimate of the emerging concentration-discharge relationship, streamflow age distributions (including the fraction of event water) and storage size, and their evolution in time due to hydrologic variability.
Salim Belyazid; Scott Bailey; Harald. Sverdrup
2010-01-01
The Hubbard Brook Ecosystem Study presents a unique opportunity for studying long-term ecosystem responses to changes in anthropogenic factors. Following industrialisation and the intensification of agriculture, the Hubbard Brook Experimental Forest (HBEF) has been subject to increased loads of atmospheric deposition, particularly sulfur and nitrogen. The deposition of...
John L. Campbell; Scott V. Ollinger; Gerald N. Flerchinger; Haley Wicklein; Katharine Hayhoe; Amey S. Bailey
2010-01-01
Long-term data from the Hubbard Brook Experimental Forest in New Hampshire show that air temperature has increased by about 1 °C over the last half century. The warmer climate has caused significant declines in snow depth, snow water equivalent and snow cover duration. Paradoxically, it has been suggested that warmer air temperatures may result in colder soils...
Benettin, Paolo; Bailey, Scott W.; Campbell, John L.; Green, Mark B.; Rinaldo, Andrea; Likens, Gene E.; McGuire, Kevin J.; Botter, Gianluca
2015-11-01
We combine experimental and modeling results from a headwater catchment at the Hubbard Brook Experimental Forest (HBEF), New Hampshire, USA, to explore the link between stream solute dynamics and water age. A theoretical framework based on water age dynamics, which represents a general basis for characterizing solute transport at the catchment scale, is here applied to conservative and weathering-derived solutes. Based on the available information about the hydrology of the site, an integrated transport model was developed and used to compute hydrochemical fluxes. The model was designed to reproduce the deuterium content of streamflow and allowed for the estimate of catchment water storage and dynamic travel time distributions (TTDs). The innovative contribution of this paper is the simulation of dissolved silicon and sodium concentration in streamflow, achieved by implementing first-order chemical kinetics based explicitly on dynamic TTD, thus upscaling local geochemical processes to catchment scale. Our results highlight the key role of water stored within the subsoil glacial material in both the short-term and long-term solute circulation. The travel time analysis provided an estimate of streamflow age distributions and their evolution in time related to catchment wetness conditions. The use of age information to reproduce a 14 year data set of silicon and sodium stream concentration shows that, at catchment scales, the dynamics of such geogenic solutes are mostly controlled by hydrologic drivers, which determine the contact times between the water and mineral interfaces. Justifications and limitations toward a general theory of reactive solute circulation at catchment scales are discussed.
Ganapathi Sridevi; Rakesh Minocha; Swathi A. Turlapati; Katherine C. Goldfarb; Eoin L. Brodie; Louis S. Tisa; Subhash C. Minocha
2012-01-01
Soil Ca depletion because of acidic deposition-related soil chemistry changes has led to the decline of forest productivity and carbon sequestration in the northeastern USA. In 1999, acidic watershed (WS) 1 at the Hubbard Brook Experimental Forest (HBEF), NH, USA was amended with Ca silicate to restore soil Ca pools. In 2006, soil samples were collected from the Ca-...
Brett A. Huggett; Paul G. Schaberg; Gary J. Hawley; Christopher Eager
2007-01-01
We surveyed and wounded forest-grown sugar maple (Acer saccharum Marsh.) trees in a long-term, replicated Ca manipulation study at the Hubbard Brook Experimental Forest in New Hampshire, USA. Plots received applications of Ca (to boost Ca availability above depleted ambient levels) or A1 (to compete with Ca uptake and further reduce Ca availability...
Directory of Open Access Journals (Sweden)
Jesse Caputo
2016-05-01
Full Text Available Background: Forests contribute to human wellbeing through the provision of important ecosystem services. Methods: In this study, we investigated how the perceived importance of ecosystem services may impact the overall benefit provided by managed watersheds at the Hubbard Brook Experimental Forest over a 45-year period, using standardized measures of service capacity weighted by service importance weights derived from a survey of beneficiaries. Results: The capacity of watersheds to regulate water flow and quality was high in all watersheds throughout the study period, whereas cultural services such as scenic beauty declined after harvest. Impacts on greenhouse gas regulation depended on the efficiency with which harvested biomass was used. Surveys revealed that stakeholders placed high value on all ecosystem services, with regulating and cultural services seen as more important than provisioning services. When service metrics were weighted by survey responses and aggregated into a single measure, total service provision followed the same overall trend as greenhouse gas regulation. Where biomass use was less efficient in terms of greenhouse gas emissions, harvesting resulted in an overall “ecosystem service debt”; where use was more efficient, this “ecosystem service debt” was reduced. Beneficiaries’ educational backgrounds significantly affected overall assessment of service provision. Beneficiaries with college or university degrees incurred smaller “ecosystem service debts” and were less negatively affected by harvesting overall. Conclusions: This study highlights the importance of including empirical measures of beneficiary preference when attempting to quantify overall provision of ecosystem services to human beneficiaries over time. Keywords: Ecosystem services, Forests, Long-term ecological research, Hubbard Brook Experimental Forest, Regulating services
Campbell, J. L.; Yanai, R. D.; Green, M.; Likens, G. E.; Buso, D. C.; See, C.; Barr, B.
2013-12-01
Small watersheds are hydrologically distinct ecological units that integrate chemical, physical and biological processes. The basic premise of the small watershed approach is that the flux of chemical elements in and out of watersheds can be used to evaluate nutrient gains or losses. In paired watershed studies, following a pre-treatment calibration period, a treated watershed is compared with a reference watershed enabling evaluation of the treatment on nutrient flux and cycling. This approach has provided invaluable insight into how ecosystems function and respond to both natural and human disturbances. Despite the great advances that have been made using this approach, the method is often criticized because the treatments are usually not replicated. The reason for this lack of replication is that it is often difficult to identify suitable replicate watersheds and is expensive due to the large scale of these studies. In cases where replication is not possible, traditional statistical approaches cannot be applied. Uncertainty analysis can help address this issue because it enables reporting of statistical confidence even when replicates are not used. However, estimating uncertainty can be challenging because it is difficult to identify and quantify sources of uncertainty, there are many different possible approaches, and the methods can be computationally challenging. In this study, we used uncertainty analysis to evaluate changes in the net hydrologic flux (inputs in precipitation minus outputs in stream water) of calcium following a whole-tree harvest at the Hubbard Brook Experimental Forest in New Hampshire, USA. In the year following the harvest, there was a large net loss of calcium (20 kg/ha/yr) in the treated watershed compared to the reference (5 kg/ha/yr). Net losses in the treated watershed have declined over the 26 years after the harvest, but still remain elevated compared to the reference. We used uncertainty analysis to evaluate whether the
Pourmokhtarian, Afshin; Driscoll, Charles T.; Campbell, John L.; Hayhoe, Katharine
2012-07-01
Dynamic hydrochemical models are useful tools for understanding and predicting the interactive effects of climate change, atmospheric CO2, and atmospheric deposition on the hydrology and water quality of forested watersheds. We used the biogeochemical model, PnET-BGC, to evaluate the effects of potential future changes in temperature, precipitation, solar radiation, and atmospheric CO2on pools, concentrations, and fluxes of major elements at the Hubbard Brook Experimental Forest in New Hampshire, United States. Future climate projections used to run PnET-BGC were generated specifically for the Hubbard Brook Experimental Forest with a statistical technique that downscales climate output (e.g., air temperature, precipitation, solar radiation) from atmosphere-ocean general circulation models (AOGCMs) to a finer temporal and spatial resolution. These climate projections indicate that over the twenty-first century, average air temperature will increase at the site by 1.7°C to 6.5°C with simultaneous increases in annual average precipitation ranging from 4 to 32 cm above the long-term mean (1970-2000). PnET-BGC simulations under future climate change show a shift in hydrology characterized by later snowpack development, earlier spring discharge (snowmelt), greater evapotranspiration, and a slight increase in annual water yield (associated with CO2 effects on vegetation). Model results indicate that under elevated temperature, net soil nitrogen mineralization and nitrification markedly increase, resulting in acidification of soil and stream water, thereby altering the quality of water draining from forested watersheds. Invoking a CO2 fertilization effect on vegetation under climate change substantially mitigates watershed nitrogen loss, highlighting the need for a more thorough understanding of CO2 effects on forest vegetation.
Chemical and morphological distinctions between vertical and lateral podzolization at Hubbard Brook
Rebecca R. Bourgault; Donald S. Ross; Scott W. Bailey
2015-01-01
Classical podzolization studies assumed vertical percolation and pedon-scale horizon development. However, hillslope-scale lateral podzolization also occurs where lateral subsurface water flux predominates. In this hydropedologic study, 99 podzols were observed in Watershed 3, Hubbard Brook Experimental Forest, New Hampshire. Soil horizon samples were extracted with...
Energy Technology Data Exchange (ETDEWEB)
Amthor, J.S.
1998-11-01
Increases in atmospheric C02 concentration from mid-1956 through mid-1997 were compared with hydrologic records from five forested, gaged watersheds in the Hubbard Brook Experimental Forest (HBEF) in New Hampshire, U.S.A. The purpose of the comparison was to assess whether a relationship between increasing atmospheric CO2 concentration and whole-ecosystem evapotranspiration (ET) could be determined. The HBEF is particularly well suited to this type of study because of the length of the hydrologic record and the physical properties of the watersheds. This analysis is based on HBEF water years (which begin 1 June and end the following 31 May) rather than calendar years. Hydrologic records from individual watersheds used in this analysis ranged from 28 to 41 water years. During the full 41-water-year period, it is estimated that water-year mean atmospheric CO2 concentration increased more than 15% (from about 314 to 363 ppm). In one south-facing watershed (i.e., HBEF watershed 3), there was a statistically significant negative relationship between atmospheric C02 concentration and ET. This translated into a nearly 77 rnndyear reduction in ET as a result of a 50 ppm increase in atmospheric C02 concentration, a result of practical significance. Evapotranspiration from the other watersheds was also negatively related to atmospheric CO2 concentration, but with smaller (and statistically insignificant) magnitudes. Evapotranspiration from the three south-facing (but not the two north-facing) watersheds included in the analysis was "abnormally" low during the most recent 2 years (i.e., water years beginning in 1995 and 1996), and this affected the trends in ET. This recent and abrupt, reduction in ET deserves further analysis, most importantly by an extension of the hydrologic record through continued long-term monitoring in the HBEF (which is ongoing). If ET remains relatively low during the coming years in south-facing watersheds, studies of the physical and/or biological
Stream Carbon Dioxide Dynamics and Evasion in Temperate Forest Catchments at Hubbard Brook
Werner, S. F.; Driscoll, C. T.; Cole, J. J.
2010-12-01
Degassing of carbon dioxide (CO2) from small streams draining forest landscapes have come under close scrutiny as potentially significant sources of CO2 relative to the net ecosystem exchange (NEE) of carbon. Quantifying such losses is essential to our understanding of how temperate forest ecosystems function as carbon sinks. The concentration of CO2 in stream water is not only a product of in-stream metabolism but also terrestrial respiration, thereby functioning as integrative measure of whole catchment respiration. Longitudinal surveys and in situ monitoring (4 hour intervals) of dissolved pCO2 were conducted to examine the spatial and temporal variability in headwater streams at the Hubbard Brook Experimental Forest, NH, USA. A valley wide survey of contrasting headwaters revealed that CO2 was rapidly lost and approached atmospheric equilibrium within the first 400 m of first flowing water. Catchment geomorphology (soil depth, slope, aspect) did not appear to significantly influence pCO2 variation between streams. Stream flow exhibited a strong control over pCO2, approaching atmospheric levels under high flows and increasing to upwards of 15,000 µatm during low flow periods. Two distinct phases of diurnal fluctuations in pCO2 were observed from early May to mid June, and again in mid August until late October. These diurnal patterns were largely absent during the height of the growing season (mid June through July). The role of small streams draining northern temperate forest ecosystems relative to the NEE of CO2 will be discussed. The Hubbard Brook pCO2 time-series are among the first reported for northern temperate forest headwaters and represent a potential advancement towards assessing whole catchment soil respiration.
Beier, Colin M; Caputo, Jesse; Groffman, Peter M
2015-10-01
In this study, by coupling long-term ecological data with empirical proxies of societal demand for benefits, we measured the capacity of forest watersheds to provide ecosystem services over variable time periods, to different beneficiaries, and in response to discrete perturbations and drivers of change. We revisited one of the earliest ecosystem experiments in North America: the 1963 de-vegetation of a forested catchment at Hubbard Brook Experimental Forest in New Hampshire, USA. Potential benefits of the regulation of water flow, water quality, greenhouse gases, and forest growth were compared between experimental (WS 2) and reference (WS 6) watersheds over a 30-year period. Both watersheds exhibited similarly high capacity for flow regulation, in part because functional loads remained low (i.e., few major storm events) during the de-vegetation period. Drought mitigation capacity, or the maintenance of flows sufficient to satisfy municipal water consumption, was higher in WS 2 due to reduced evapotranspiration associated with loss of plant cover. We also assessed watershed capacity to regulate flows to satisfy different beneficiaries, including hypothetical flood averse and drought averse types. Capacity to regulate water quality was severely degraded during de-vegetation, as nitrate concentrations exceeded drinking water standards on 40% of measurement days. Once forest regeneration began, WS 2 rapidly recovered the capacity to provide safe drinking water, and subsequently mitigated the eutrophication potential of rainwater at a marginally higher level than WS 6. We estimated this additional pollution removal benefit would have to accrue for approximately 65-70 years to offset the net eutrophication cost incurred during forest removal. Overall, our results affirmed the critical role of forest vegetation in water regulation, but also indicated trade-offs associated with forest removal and recovery that partially depend on larger-scale exogenous changes in climate
Knox, Robert G.; Blair, J. Bryan; Schwarz, Paul A.; Hofton, Michelle A.; Dubayah, Ralph; Smith, David E. (Technical Monitor)
2000-01-01
On September 26, 1999, we mapped canopy structure over 90% of the Hubbard Brook Experimental Forest in White Mountain National Forest, New Hampshire, using the Laser Vegetation Imaging Sensor (LVIS). This airborne instrument was configured to emulate data expected from the Vegetation Canopy Lidar (VCL) space mission. We compared above ground heights of the tallest surfaces detected by lidar with average forest canopy heights estimated from tree-based measurements in or near 346 0.05 ha plots (made in autumn of 1997 and 1998). Vegetation heights had by far the predominant influence on lidar top heights, but with this large data set we were able to measure two significant secondary effects: those of steepness or slope of the underlying terrain and of tree crown form. The size of the slope effect was intermediate between that expected from models of homogeneous canopy layers and for solitary tree crowns. The first detected surfaces were also proportionately taller for plots with more basal area in broad leaved northern hardwoods than for mostly coniferous plots. We expected this because of the contrast between the shapes of cumulative distributions of surface area for elliptical or hemi-elliptical tree crowns and those for conical crowns. Correcting for these secondary effects, when appropriate data are available for calibration, may improve vegetation structure estimates in regional studies using VCL or similar lidar data sources.
John L. Campbell; Amey S. Bailey; Christopher Eagar; Mark B. Green; John J. Battles
2013-01-01
By the late 19th and early 20th century, extensive forest harvesting was occurring throughout the United States, often with little regard for natural resources. The effects of logging on the environment were relatively unknown, which contributed to rising environmental concerns. Relationships between forests and stream water yield were of particular interest, because...
A comparative and experimental evaluation of performance of stocked diploid and triploid brook trout
Budy, Phaedra E.; Thiede, G.P.; Dean, A.; Olsen, D.; Rowley, G.
2012-01-01
Despite numerous negative impacts, nonnative trout are still being stocked to provide economically and socially valuable sport fisheries in western mountain lakes. We evaluated relative performance and potential differences in feeding strategy and competitive ability of triploid versus diploid brook trout Salvelinus fontinalis in alpine lakes, as well as behavioral and performance differences of diploid and triploid brook trout in two controlled experimental settings: behavioral experiments in the laboratory and performance evaluations in ponds. Across lakes, catch per unit effort (CPUE) and relative weight (Wr ) were not significantly different between ploidy levels. Mean sizes were also similar between ploidy levels except in two of the larger lakes where diploids attained slightly larger sizes (approximately 20 mm longer). We observed no significant differences between diploids and triploids in diet, diet preference, or trophic structure. Similarly, growth and condition did not differ between ploidy levels in smaller-scale pond experiments, and aggressive behavior did not differ between ploidy levels (fed or unfed fish trials) in the laboratory. Independent of ploidy level, the relative performance of brook trout varied widely among lakes, a pattern that appeared to be a function of lake size or a factor that covaries with lake size such as temperature regime or carrying capacity. In summary, we observed no significant differences in the relative performance of brook trout from either ploidy level across a number of indices, systems, and environmental conditions, nor any indication that one group is more aggressive or a superior competitor than the other. Collectively, these results suggest that triploid brook trout will offer a more risk-averse and promising management opportunity when they are stocked to these lakes and elsewhere to simultaneously meet the needs for the sport fishery and conservation objectives.
Experimental test of genetic rescue in isolated populations of brook trout
Robinson, Zachary L.; Coombs, Jason A.; Hudy, Mark; Nislow, Keith H.; Letcher, Benjamin H.; Whiteley, Andrew R.
2017-01-01
Genetic rescue is an increasingly considered conservation measure to address genetic erosion associated with habitat loss and fragmentation. The resulting gene flow from facilitating migration may improve fitness and adaptive potential, but is not without risks (e.g., outbreeding depression). Here, we conducted a test of genetic rescue by translocating ten (five of each sex) brook trout (Salvelinus fontinalis) from a single source to four nearby and isolated stream populations. To control for the demographic contribution of translocated individuals, ten resident individuals (five of each sex) were removed from each recipient population. Prior to the introduction of translocated individuals, the two smallest above-barrier populations had substantially lower genetic diversity, and all populations had reduced effective number of breeders relative to adjacent below-barrier populations. In the first reproductive bout following translocation, 31 of 40 (78%) translocated individuals reproduced successfully. Translocated individuals contributed to more families than expected under random mating and generally produced larger full-sibling families. We observed relatively high (>20%) introgression in three of the four recipient populations. The translocations increased genetic diversity of recipient populations by 45% in allelic richness and 25% in expected heterozygosity. Additionally, strong evidence of hybrid vigour was observed through significantly larger body sizes of hybrid offspring relative to resident offspring in all recipient populations. Continued monitoring of these populations will test for negative fitness effects beyond the first generation. However, these results provide much-needed experimental data to inform the potential effectiveness of genetic rescue-motivated translocations.
McLennan, S. M.; Dehouck, E.; Hurowitz, J.; Lindsley, D. H.; Schoonen, M. A.; Tosca, N. J.; Zhao, Y. Y. S.
2016-12-01
Starting with Pathfinder and Global Surveyor, recent missions to Mars have provided great opportunity for low-temperature experimental geochemistry investigations of the Martian sedimentary record by providing geochemical and mineralogical data that can be used as meaningful tests for experiments. These missions have documented a long-lived, complex and dynamic sedimentary rock cycle, including "source-to-sink" sedimentary systems and global paleoenvironmental transitions through time. We designed and constructed an experimental facility, beginning in 2000, specifically to evaluate surficial processes on Mars. Our experimental philosophy has been to (1) keep apparatus simple and flexible, and if feasible maintain sample access during experiments; (2) use starting materials (minerals, rocks) close to known Mars compositions (often requiring synthesis); (3) address sedimentary processes supported by geological investigations at Mars; (4) begin with experiments at standard conditions so they are best supported by thermodynamics; (5) support experiments with thermodynamic-kinetic-mass balance modeling in both design and interpretation, and by high quality chemical, mineralogical and textural lab analyses; (6) interpret results in the context of measurements made at Mars. Although eliciting much comment in proposal and manuscript reviews, we have not attempted to slavishly maintain "Mars conditions", doing so only to the degree required by variables being tested in any given experiments. Among the problems we have addressed are (1) Amazonian alteration of rock surfaces; (2) Noachian-Hesperian chemical weathering; (3) epithermal alteration of `evolved' igneous rocks; (4) mineral surface chemical reactivity from aeolian abrasion; (5) evaporation of mafic brines; (6) early diagenesis of sedimentary iron mineralogy; (7) trace element and halogen behavior during chemical weathering and diagenesis; (8) photochemical influences on halogen distribution and speciation; (9) post
Paul G. Schaberg; Rakesh Minocha; Stephanie Long; Joshua M. Halman; Gary J. Hawley; Christopher. Eagar
2011-01-01
Red spruce (Picea rubens Sarg.) trees are uniquely vulnerable to foliar freezing injury during the cold season (fall and winter), but are also capable of photosynthetic activity if temperatures moderate. To evaluate the influence of calcium (Ca) addition on the physiology of red spruce during the cold season, we measured concentrations of foliar...
Endoparasites of plethodontid salamanders from Paradise Brook, New Hampshire.
Muzzall, P M; Peebles, C R; Burton, T M
1997-12-01
Totals of 52 dusky salamanders Desmognathus fuscus, 51 two-lined salamanders Eurycea bislineata, 54 red-backed salamanders Plethodon cinereus, and 3 spring salamanders Gyrinophilus porphyriticus (Plethodontidae) collected in June and August 1995 from Paradise Brook, a tributary to Hubbard Brook, New Hampshire, were examined for parasites. Parasites found were Brachycoelium storeriae, Brachycoelium sp., Bothriocephalus rarus, Falcaustra sp., Omeia sp., Batracholandros magnavulvaris, and Cepedietta michiganensis. Eighty-six percent of the red-backed salamanders, a terrestrial species, harbored 1 or more parasites. Among the aquatic and semiaquatic species, 27% of the dusky and 45% of the two-lined salamanders were infected with 1 or more parasites.
Szepietowski, J C; Wasik, F; Szybejko-Machaj, G; Bieniek, A; Schwartz, R A
2001-07-01
The Brooke-Spiegler syndrome is an autosomal dominant one characterized by cylindromas, trichoepitheliomas and occasionally spiradenomas. Within a given family, some members may have cylindromas whereas others may have trichoepitheliomas or both. We describe the coexistence of trichoepithelioma papulosum multiplex (also known as epithelioma adenoides cysticum of Brooke) and cylindromas in a 30-year-old man, and discuss the relationship between these two autosomal dominant syndromes.
Bose-Hubbard Hamiltonian: Quantum chaos approach
Kolovsky, Andrey R.
2016-03-01
We discuss applications of the theory of quantum chaos to one of the paradigm models of many-body quantum physics — the Bose-Hubbard (BH) model, which describes, in particular, interacting ultracold Bose atoms in an optical lattice. After preliminary, pure quantum analysis of the system we introduce the classical counterpart of the BH model and the governing semiclassical equations of motion. We analyze these equations for the problem of Bloch oscillations (BOs) of cold atoms where a number of experimental results are available. The paper is written for nonexperts and can be viewed as an introduction to the field.
Paul G. Schaberg; Gary J. Hawley
2010-01-01
Pollution-induced acidification and other anthropogenic factors are leaching calcium (Ca) and mobilizing aluminum (Al) in many forest soils. Because Ca is an essential nutrient and Al is a potential toxin, resulting depletions of Ca and increases in available Al may significantly alter the health and productivity of forest trees. Controlled experiments on red spruce (...
Introduction to Hubbard model and exact diagonalization
Directory of Open Access Journals (Sweden)
S. Akbar Jafari
2008-06-01
Full Text Available Hubbard model is an important model in the theory of strongly correlated electron systems. In this contribution we introduce this model and the concepts of electron correlation by building on a tight binding model. After enumerating various methods of tackling the Hubbard model, we introduce the numerical method of exact diagonalization in detail. The book keeping and practical implementation aspects are illustrated with analytically solvable example of two-site Hubbard model.
Measurement of the Equation of State of the Two-Dimensional Hubbard Model
Miller, Luke; Cocchi, Eugenio; Drewes, Jan; Koschorreck, Marco; Pertot, Daniel; Brennecke, Ferdinand; Koehl, Michael
2016-05-01
The subtle interplay between kinetic energy, interactions and dimensionality challenges our comprehension of strongly-correlated physics observed, for example, in the solid state. In this quest, the Hubbard model has emerged as a conceptually simple, yet rich model describing such physics. Here we present an experimental determination of the equation of state of the repulsive two-dimensional Hubbard model over a broad range of interactions, 0 constitute benchmarks for state-of-the-art theoretical approaches.
Łącki, Mateusz; Damski, Bogdan; Zakrzewski, Jakub
2016-12-02
We show that the critical point of the two-dimensional Bose-Hubbard model can be easily found through studies of either on-site atom number fluctuations or the nearest-neighbor two-point correlation function (the expectation value of the tunnelling operator). Our strategy to locate the critical point is based on the observation that the derivatives of these observables with respect to the parameter that drives the superfluid-Mott insulator transition are singular at the critical point in the thermodynamic limit. Performing the quantum Monte Carlo simulations of the two-dimensional Bose-Hubbard model, we show that this technique leads to the accurate determination of the position of its critical point. Our results can be easily extended to the three-dimensional Bose-Hubbard model and different Hubbard-like models. They provide a simple experimentally-relevant way of locating critical points in various cold atomic lattice systems.
Branner-Hubbard Motions and attracting dynamics
DEFF Research Database (Denmark)
Petersen, Carsten Lunde; Tan, Lei
2006-01-01
We introduce a new notion of attracting dynamics, which is related to polynomial-like mappings. Also we review the Branner-Hubbard Motion and study its action on attracting dynamics.......We introduce a new notion of attracting dynamics, which is related to polynomial-like mappings. Also we review the Branner-Hubbard Motion and study its action on attracting dynamics....
Branner-Hubbard motions and attracting dynamics
DEFF Research Database (Denmark)
Petersen, Carsten Lunde; Tan, Lei
We introduce the new notion an aatracting dynamics, which is related to polynomial-likke mappings. Also we review the Branner-Hubbard motion and study its action on attracting dynamics.......We introduce the new notion an aatracting dynamics, which is related to polynomial-likke mappings. Also we review the Branner-Hubbard motion and study its action on attracting dynamics....
Hubbard model with geometrical frustration
Energy Technology Data Exchange (ETDEWEB)
Lee, Hunpyo
2009-10-15
At first we present the details of the dual fermion (DF), the cluster extension of dynamical mean field theory (CDMFT) and continuous-time quantum Monte Carlo (CT QMC) methods. Using a panoply of these methods we explore the Hubbard model on the triangular and hyperkagome lattice. We find a first-order transition and continuous transition on the triangular and hyper-kagome lattice, respectively. Moreover, we find the reentrant behavior due to competition between the magnetic correlation and itinerancy of electrons by source of geometrical frustration on both lattices. (orig.)
Equation of State of the Two-Dimensional Hubbard Model
Cocchi, Eugenio; Miller, Luke A.; Drewes, Jan H.; Koschorreck, Marco; Pertot, Daniel; Brennecke, Ferdinand; Köhl, Michael
2016-04-01
The subtle interplay between kinetic energy, interactions, and dimensionality challenges our comprehension of strongly correlated physics observed, for example, in the solid state. In this quest, the Hubbard model has emerged as a conceptually simple, yet rich model describing such physics. Here we present an experimental determination of the equation of state of the repulsive two-dimensional Hubbard model over a broad range of interactions 0 ≲U /t ≲20 and temperatures, down to kBT /t =0.63 (2 ) using high-resolution imaging of ultracold fermionic atoms in optical lattices. We show density profiles, compressibilities, and double occupancies over the whole doping range, and, hence, our results constitute benchmarks for state-of-the-art theoretical approaches.
An algebraic approach to the Hubbard model
de Leeuw, Marius
2015-01-01
We study the algebraic structure of an integrable Hubbard-Shastry type lattice model associated with the centrally extended su(2|2) superalgebra. This superalgebra underlies Beisert's AdS/CFT worldsheet R-matrix and Shastry's R-matrix. The considered model specializes to the one-dimensional Hubbard model in a certain limit. We demonstrate that Yangian symmetries of the R-matrix specialize to the Yangian symmetry of the Hubbard model found by Korepin and Uglov. Moreover, we show that the Hubbard model Hamiltonian has an algebraic interpretation as the so-called secret symmetry. We also discuss Yangian symmetries of the A and B models introduced by Frolov and Quinn.
Ising Expansion for the Hubbard Model
Shi, Zhu-Pei; Singh, Rajiv R. P.
1995-01-01
We develop series expansions for the ground state properties of the Hubbard model, by introducing an Ising anisotropy into the Hamiltonian. For the two-dimensional (2D) square lattice half-filled Hubbard model, the ground state energy, local moment, sublattice magnetization, uniform magnetic susceptibility and spin stiffness are calculated as a function of $U/t$, where $U$ is the Coulomb constant and $t$ is the hopping parameter. Magnetic susceptibility data indicate a crossover around $U\\app...
Quasiparticle band structure for the Hubbard systems: Application to. alpha. -CeAl sub 2
Energy Technology Data Exchange (ETDEWEB)
Costa-Quintana, J.; Lopez-Aguilar, F. (Departamento de Fisica, Grupo de Electromagnetismo, Universidad Autonoma de Barcelona, Bellaterra, E-08193 Barcelona, Spain (ES)); Balle, S. (Departament de Fisica, Universitat de les Illes Balears, E-07071 Palma de Mallorca, Spain (ES)); Salvador, R. (Control Data Corporation, TALLAHASSEE, FL (USA) Supercomputer Computations Research Institute, Florida State University, Tallahassee, Florida 32306-4052 (USA))
1990-04-01
A self-energy formalism for determining the quasiparticle band structure of the Hubbard systems is deduced. The self-energy is obtained from the dynamically screened Coulomb interaction whose bare value is the correlation energy {ital U}. A method for integrating the Schroedingerlike equation with the self-energy operator is given. The method is applied to the cubic Laves phase of {alpha}-CeAl{sub 2} because it is a clear Hubbard system with a very complex electronic structure and, moreover, this system provides us with sufficient experimental data for testing our method.
36 CFR 13.1226 - Brooks Falls area.
2010-07-01
... 36 Parks, Forests, and Public Property 1 2010-07-01 2010-07-01 false Brooks Falls area. 13.1226... Developed Area § 13.1226 Brooks Falls area. The area within 50 yards of the ordinary high water marks of the Brooks River from the Riffles Bear Viewing Platform to a point 100 yards above Brooks Falls is closed...
Phase Diagram of the Frustrated Hubbard Model
Zitzler, R.; Tong, N.-H.; Pruschke, Th.; Bulla, R.
2004-07-01
The Mott-Hubbard metal-insulator transition in the paramagnetic phase of the one-band Hubbard model has long been used to describe similar features in real materials like V2O3. In this Letter we investigate the antiferromagnetic phase of this model with frustration. At T=0 we find a first-order transition from a paramagnetic metal to an antiferromagnetic insulator. We show that even in the presence of strong magnetic frustration, the paramagnetic metal-insulator transition is hidden inside an extended antiferromagnetic region. This raises the question of whether the one-band Hubbard model with frustration is sufficient to describe the phase diagram of V2O3 or similar transition metal oxides even qualitatively.
Mott-Hubbard transition in the mass-imbalanced Hubbard model
Philipp, Marie-Therese; Wallerberger, Markus; Gunacker, Patrik; Held, Karsten
2016-01-01
The mass-imbalanced Hubbard model represents a continuous evolution from the Hubbard to the Falicov-Kimball model. We employ dynamical mean field theory and study the paramagnetic metal-insulator transition, which has a very different nature for the two limiting models. Our results indicate that the metal-insulator transition rather resembles that of the Hubbard model as soon as a tiny hopping between the more localized fermions is switched on. At low temperatures we observe a first-order met...
2012 USGS Lidar: Brooks Camp (AK)
National Oceanic and Atmospheric Administration, Department of Commerce — The U.S. Geological Survey (USGS) had a requirement for high resolution Lidar needed for mapping the Brooks Camp region of Katmai National Park in Alaska....
Katherine Brooke'ist / Tiina Lepiste
Lepiste, Tiina
2007-01-01
Ameerika teleseriaali "Vaprad ja ilusad" ("The Bold and the Beautiful") osatäitja Katherine Kelly Lang (Brooke). Artikli aluseks on Soap Opera Weekly ajakirjaniku Linda Susmani vestlus näitlejannaga
Katherine Brooke'ist / Tiina Lepiste
Lepiste, Tiina
2007-01-01
Ameerika teleseriaali "Vaprad ja ilusad" ("The Bold and the Beautiful") osatäitja Katherine Kelly Lang (Brooke). Artikli aluseks on Soap Opera Weekly ajakirjaniku Linda Susmani vestlus näitlejannaga
Genetics Home Reference: Brooke-Spiegler syndrome
... gene (CYLD) mutations in Brooke-Spiegler syndrome: novel insights into the role of deubiquitination in cell signaling. ... healthcare professional . About Genetics Home Reference Site Map Customer Support Selection Criteria for Links USA.gov Copyright ...
Morse, S. A.
2008-10-01
The foremost principles of experimental igneous petrology applied to natural rocks are here considered to be the following. First, only the mineral assemblages found at or near the experimental liquidus are relevant to fractional crystallization. Subliquidus assemblages of the same bulk composition can have little relevance to this process, owing to the closed system of the experiment. Second, in a closed system the natural mineral assemblages define the intensive parameters of T, P, and the activities of all components, including oxygen, which must constrain the experimental investigation. Extensive (mass-dependent) parameters do not define the compositions of the evolving liquids, which are solely controlled by successive liquidus phase assemblages. Third, the bulk compositions (rocks or mixtures) chosen for study must be able to yield at the liquidus the mineral compositions found in the natural occurrence. The study under discussion fails in all three of these desiderata. Subliquidus products of equilibrium crystallization and their masses were used to infer a differentiation history. Intensive parameters were constrained to an arbitrary choice of the FMQ buffer. Finally, the bulk compositions chosen for experiment can be shown beforehand (and as in the listed results) to yield olivine and plagioclase compositions far more refractory than in any known rock of the target intrusion.
The landscape of the Hubbard model
Sachdev, Subir
2010-01-01
I present a pedagogical survey of a variety of quantum phases of the Hubbard model. The honeycomb lattice model has a conformal field theory connecting the semi-metal to the insulator with Neel order. States with fractionalized excitations are linked to the deconfined phases of gauge theories. I also consider the confining phases of such gauge theories, and show how Berry phases of monopoles induce valence bond solid order. Compressible metallic phases with Fermi surfaces are described, including the 'fractionalized Fermi liquid', using the Hubbard model on a bilayer triangular lattice. I make numerous connections to the AdS/CFT correspondence, reviewing insights gained and discussing open problems that the correspondence could address.
Quantum simulation of a Fermi-Hubbard model using a semiconductor quantum dot array
Hensgens, T.; Fujita, T.; Janssen, L.; Li, Xiao; van Diepen, C. J.; Reichl, C.; Wegscheider, W.; Das Sarma, S.; Vandersypen, L. M. K.
2017-08-01
Interacting fermions on a lattice can develop strong quantum correlations, which are the cause of the classical intractability of many exotic phases of matter. Current efforts are directed towards the control of artificial quantum systems that can be made to emulate the underlying Fermi-Hubbard models. Electrostatically confined conduction-band electrons define interacting quantum coherent spin and charge degrees of freedom that allow all-electrical initialization of low-entropy states and readily adhere to the Fermi-Hubbard Hamiltonian. Until now, however, the substantial electrostatic disorder of the solid state has meant that only a few attempts at emulating Fermi-Hubbard physics on solid-state platforms have been made. Here we show that for gate-defined quantum dots this disorder can be suppressed in a controlled manner. Using a semi-automated and scalable set of experimental tools, we homogeneously and independently set up the electron filling and nearest-neighbour tunnel coupling in a semiconductor quantum dot array so as to simulate a Fermi-Hubbard system. With this set-up, we realize a detailed characterization of the collective Coulomb blockade transition, which is the finite-size analogue of the interaction-driven Mott metal-to-insulator transition. As automation and device fabrication of semiconductor quantum dots continue to improve, the ideas presented here will enable the investigation of the physics of ever more complex many-body states using quantum dots.
Quantum simulation of a Fermi-Hubbard model using a semiconductor quantum dot array.
Hensgens, T; Fujita, T; Janssen, L; Li, Xiao; Van Diepen, C J; Reichl, C; Wegscheider, W; Das Sarma, S; Vandersypen, L M K
2017-08-02
Interacting fermions on a lattice can develop strong quantum correlations, which are the cause of the classical intractability of many exotic phases of matter. Current efforts are directed towards the control of artificial quantum systems that can be made to emulate the underlying Fermi-Hubbard models. Electrostatically confined conduction-band electrons define interacting quantum coherent spin and charge degrees of freedom that allow all-electrical initialization of low-entropy states and readily adhere to the Fermi-Hubbard Hamiltonian. Until now, however, the substantial electrostatic disorder of the solid state has meant that only a few attempts at emulating Fermi-Hubbard physics on solid-state platforms have been made. Here we show that for gate-defined quantum dots this disorder can be suppressed in a controlled manner. Using a semi-automated and scalable set of experimental tools, we homogeneously and independently set up the electron filling and nearest-neighbour tunnel coupling in a semiconductor quantum dot array so as to simulate a Fermi-Hubbard system. With this set-up, we realize a detailed characterization of the collective Coulomb blockade transition, which is the finite-size analogue of the interaction-driven Mott metal-to-insulator transition. As automation and device fabrication of semiconductor quantum dots continue to improve, the ideas presented here will enable the investigation of the physics of ever more complex many-body states using quantum dots.
Brook trout use of thermal refugia and foraging habitat influenced by brown trout
Hitt, Nathaniel P.; Snook, Erin; Massie, Danielle L.
2017-01-01
The distribution of native brook trout (Salvelinus fontinalis) in eastern North America is often limited by temperature and introduced brown trout (Salmo trutta), the relative importance of which is poorly understood but critical for conservation and restoration planning. We evaluated effects of brown trout on brook trout behavior and habitat use in experimental streams across increasing temperatures (14–23 °C) with simulated groundwater upwelling zones providing thermal refugia (6–9 °C below ambient temperatures). Allopatric and sympatric trout populations increased their use of upwelling zones as ambient temperatures increased, demonstrating the importance of groundwater as thermal refugia in warming streams. Allopatric brook trout showed greater movement rates and more even spatial distributions within streams than sympatric brook trout, suggesting interference competition by brown trout for access to forage habitats located outside thermal refugia. Our results indicate that removal of introduced brown trout may facilitate native brook trout expansion and population viability in downstream reaches depending in part on the spatial configuration of groundwater upwelling zones.
Mass-imbalanced ionic Hubbard chain
Sekania, Michael; Baeriswyl, Dionys; Jibuti, Luka; Japaridze, George I.
2017-07-01
A repulsive Hubbard model with both spin-asymmetric hopping (t↑≠t↓ ) and a staggered potential (of strength Δ ) is studied in one dimension. The model is a compound of the mass-imbalanced (t↑≠t↓ ,Δ =0 ) and ionic (t↑=t↓ ,Δ >0 ) Hubbard models, and may be realized by cold atoms in engineered optical lattices. We use mostly mean-field theory to determine the phases and phase transitions in the ground state for a half-filled band (one particle per site). We find that a period-two modulation of the particle (or charge) density and an alternating spin density coexist for arbitrary Hubbard interaction strength, U ≥0 . The amplitude of the charge modulation is largest at U =0 , decreases with increasing U and tends to zero for U →∞ . The amplitude for spin alternation increases with U and tends to saturation for U →∞ . Charge order dominates below a value Uc, whereas magnetic order dominates above. The mean-field Hamiltonian has two gap parameters, Δ↑ and Δ↓, which have to be determined self-consistently. For U Uc they have different signs, and for U =Uc one gap parameter jumps from a positive to a negative value. The weakly first-order phase transition at Uc can be interpreted in terms of an avoided criticality (or metallicity). The system is reluctant to restore a symmetry that has been broken explicitly.
Mott-Hubbard transition in the mass-imbalanced Hubbard model
Philipp, Marie-Therese; Wallerberger, Markus; Gunacker, Patrik; Held, Karsten
2017-06-01
The mass-imbalanced Hubbard model represents a continuous evolution from the Hubbard to the Falicov-Kimball model. We employ dynamical mean field theory and study the paramagnetic metal-insulator transition, which has a very different nature for the two limiting models. Our results indicate that the metal-insulator transition rather resembles that of the Hubbard model as soon as a tiny hopping between the more localized fermions is switched on. At low temperatures we observe a first-order metal-insulator transition and a three peak structure. The width of the central peak is the same for the more and less mobile fermions when approaching the phase transition, which agrees with our expectation of a common Kondo temperature and phase transition for the two species.
Rozhkov, A. V.; Rakhmanov, A. L.
2011-02-01
The Hubbard-I approximation is generalized to allow for direct evaluation of the equal-time anomalous two-electron propagator for the Hubbard model on a two-dimensional square lattice. This propagator is compared against the quantum Monte Carlo data obtained by Aimi and Imada (2007 J. Phys. Soc. Japan 76 113708) in the limit of strong electron-electron interaction. The Hubbard-I predictions are in good qualitative agreement with the Monte Carlo results. In particular, d-wave correlations decay as cr - 3 ('free-electron' behaviour) if the separation r exceeds 2-3 lattice constants. However, the Hubbard-I approximation underestimates the coefficient c by a factor of about 3. We conclude that the Hubbard-I approximation, despite its simplicity and artefacts, captures the qualitative behaviour of the two-particle propagator for the Hubbard model, at least for moderate values of r.
Peter Brook y el pensamiento tradicional
Nicolescu, Basarab
2014-01-01
La trayectoria creativa de Peter Brook tiene su fuente en la investigación sobre la tradición. En este ensayo se hace un recorrido por su concepción teatral y se revisan los diversos sentidos del concepto “tradición”. Desde la perspectiva transdiciplinaria se analizan los componentes centrales del teatro de Brook: energía, movimiento e interrelación, así como la estructura ternaria del espacio, la relación entre determinismo y espontaneidad y la imposibilidad de un lenguaje universal. El pens...
BCS-Hubbard model applied to anisotropic superconductors
Energy Technology Data Exchange (ETDEWEB)
Millan, J.S., E-mail: smillan@pampano.unacar.mx [Facultad de Ingenieria, Universidad Autonoma del Carmen, Cd. del Carmen, 24180 Campeche (Mexico); Perez, L.A. [Instituto de Fisica, Universidad Nacional Autonoma de Mexico, A.P. 20-364, 01000, Mexico D.F. (Mexico); Wang, C. [Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico, A.P. 70-360, 04510, Mexico D.F. (Mexico)
2011-11-15
The BCS formalism applied to a Hubbard model, including correlated hoppings, is used to study d-wave superconductors. The theoretical T{sub c} vs. n relationship is compared with experimental data from BiSr{sub 2-x}La{sub x}CuO{sub 6+{delta}} and La{sub 2-x}Sr{sub x}CuO{sub 4}. The results suggest a nontrivial correlation between the hole and the doping concentrations. Based on the BCS formalism, we study the critical temperature (T{sub c}) as a function of electron density (n) in a square lattice by means of a generalized Hubbard model, in which first ({Delta}t) and second neighbors ({Delta}t{sub 3}) correlated-hopping interactions are included in addition to the repulsive Coulomb ones. We compare the theoretical T{sub c} vs. n relationship with experimental data of cuprate superconductors BiSr{sub 2-x}La{sub x}CuO{sub 6+{delta}} (BSCO) and La{sub 2-x}Sr{sub x}CuO{sub 4}, (LSCO). The theory agrees very well with BSCO data even though the complicated association between Sr concentration (x) and hole doping (p). For the LSCO system, it is observed that in the underdoped regime, the T{sub c} vs. n behavior can be associated to different systems with small variations of t'. For the overdoped regime, a more complicated dependence n = 1 - p/2 fits better than n = 1 - p. On the other hand, it is proposed that the second neighbor hopping ratio (t'/t) should be replaced by the effective mean field hopping ratio t{sub MF}{sup '}/t{sub MF}, which can be very sensitive to small changes of t' due to the doping.
Directory of Open Access Journals (Sweden)
Alexandre Bérubé Tellier
2016-12-01
Full Text Available Ephippium pigmentation is a plastic trait which can be related to a trade-off between visual predation pressure and better protection of cladoceran eggs against different types of stress. Experimental studies showed that planktivorous fish exert a greater predation pressure on individuals carrying darker ephippia, but little is known about the variation of ephippium pigmentation along gradients of fish predation pressure in natural conditions. For this study, our experimental design included four small boreal lakes with known fish assemblages. Two of the lakes have viable brook trout (Salvelinus fontinalis populations, whereas the other two lakes experienced brook trout extinctions during the 20th century. Cladoceran ephippia were extracted from sediment cores at layers corresponding to the documented post- extinction phase (1990's and from an older layer (1950's for which the brook trout population status is not known precisely. Our first objective was to determine whether brook trout extinction has a direct effect on both ephippium pigmentation and size. Our second objective was to give a preliminary assessment of the status of brook trout populations in the 1950's by comparing the variation in ephippia traits measured from this layer to those measured in the 1990's, for which the extinction patterns are well known. Cost-effective image analysis was used to assess variation in pigmentation levels in ephippia. This approach provided a proxy for the amount of melanin invested in each ephippium analysed. Our study clearly shows that ephippium pigmentation may represent a better indicator of the presence of fish predators than ephippium size, a trait that showed a less clear pattern of variation between lakes with and without fish. For the 1990's period, ephippia from fishless lakes were darker and showed a slight tendency to be larger than ephippia from lakes with brook trout. However, no clear differences in either ephippium size or pigmentation
Hubbard-U band-structure methods
DEFF Research Database (Denmark)
Albers, R.C.; Christensen, Niels Egede; Svane, Axel
2009-01-01
The last decade has seen a large increase in the number of electronic-structure calculations that involve adding a Hubbard term to the local-density approximation band-structure Hamiltonian. The Hubbard term is then determined either at the mean-field level or with sophisticated many-body techniq...
Hubbard physics in the PAW GW approximation.
Booth, J M; Drumm, D W; Casey, P S; Smith, J S; Russo, S P
2016-06-28
It is demonstrated that the signatures of the Hubbard Model in the strongly interacting regime can be simulated by modifying the screening in the limit of zero wavevector in Projector-Augmented Wave GW calculations for systems without significant nesting. This modification, when applied to the Mott insulator CuO, results in the opening of the Mott gap by the splitting of states at the Fermi level into upper and lower Hubbard bands, and exhibits a giant transfer of spectral weight upon electron doping. The method is also employed to clearly illustrate that the M1 and M2 forms of vanadium dioxide are fundamentally different types of insulator. Standard GW calculations are sufficient to open a gap in M1 VO2, which arise from the Peierls pairing filling the valence band, creating homopolar bonds. The valence band wavefunctions are stabilized with respect to the conduction band, reducing polarizability and pushing the conduction band eigenvalues to higher energy. The M2 structure, however, opens a gap from strong on-site interactions; it is a Mott insulator.
Dynamical Vertex Approximation for the Hubbard Model
Toschi, Alessandro
A full understanding of correlated electron systems in the physically relevant situations of three and two dimensions represents a challenge for the contemporary condensed matter theory. However, in the last years considerable progress has been achieved by means of increasingly more powerful quantum many-body algorithms, applied to the basic model for correlated electrons, the Hubbard Hamiltonian. Here, I will review the physics emerging from studies performed with the dynamical vertex approximation, which includes diagrammatic corrections to the local description of the dynamical mean field theory (DMFT). In particular, I will first discuss the phase diagram in three dimensions with a special focus on the commensurate and incommensurate magnetic phases, their (quantum) critical properties, and the impact of fluctuations on electronic lifetimes and spectral functions. In two dimensions, the effects of non-local fluctuations beyond DMFT grow enormously, determining the appearance of a low-temperature insulating behavior for all values of the interaction in the unfrustrated model: Here the prototypical features of the Mott-Hubbard metal-insulator transition, as well as the existence of magnetically ordered phases, are completely overwhelmed by antiferromagnetic fluctuations of exponentially large extension, in accordance with the Mermin-Wagner theorem. Eventually, by a fluctuation diagnostics analysis of cluster DMFT self-energies, the same magnetic fluctuations are identified as responsible for the pseudogap regime in the holed-doped frustrated case, with important implications for the theoretical modeling of the cuprate physics.
Emergent phases in the spin orbit coupled spin-1 Bose Hubbard model
Natu, Stefan; Pixley, Jedediah
2015-05-01
Motivated by recent experiments on spin orbit coupled, ultra-cold Bose gases, we theoretically study the spin-1 Bose Hubbard model in the presence and absence of spin orbit coupling (SOC). In the absence of SOC, using a spatially homogenous Gutzwiller mean field theory, we determine the phase diagram and excitation spectrum of the spin-1 Bose Hubbard model on a hyper-cubic lattice in both the polar and ferromagnetic phases. We focus on the evolution of various density, spin, and nematic order parameters across the phase diagram as a function of chemical potential and nearest neighbor hopping. We then generalize the Gutzwiller mean-field theory to incorporate spin-orbit coupling by allowing the mean-fields to be spatially inhomogeneous, which enable us to study spontaneous translational symmetry broken phases. To connect with ongoing experiments, we focus on the lattice generalization of the experimentally realized 1D spin-orbit coupling.
Hubbard-I approach to the Mott transition
Energy Technology Data Exchange (ETDEWEB)
Grzybowski, Przemyslaw R.; Chhajlany, Ravindra W. [Faculty of Physics, Adam Mickiewicz University, Umultowska 85, 61-614 Poznan (Poland)
2012-11-15
We expose the relevance of double occupancy conservation symmetry in application of the Hubbard-I approach to strongly correlated electron systems. We propose the utility of a composite method, viz. the Hubbard-I method in conjunction with strong coupling perturbation expansion, for studying systems violating the afore-mentioned symmetry. We support this novel approach by presenting a first successful Hubbard-I type calculation for the description of the metal-insulator paramagnetic Mott transition in a strongly correlated electron system with conserved double occupancies, which is a constrained Hubbard Hamiltonian equivalent to the Hubbard bond charge Hamiltonian at a symmetry point X = t. In particular, we obtain the phase diagram of this system for arbitrary fillings, as well as new, universal critical indices of the Mott transition at half-filling in 1,2, and 3 dimensions. We also compare the Hubbard-I band-splitting Mott transition description with results obtained using the standard Gutzwiller Approximation (GA), and show that the two approximate approaches lead to qualitatively different results. In contrast to the GA applied to the system studied here, the Hubbard-I approach compares favorably with known exact results for the d = 1 dimensional chain. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
L Ron Hubbard's science fiction quest against psychiatry.
Hirshbein, Laura
2016-12-01
Layfayette Ronald Hubbard (1911-1986) was a colourful and prolific American writer of science fiction in the 1930s and 1940s. During the time between his two decades of productivity and his return to science fiction in 1980, Hubbard founded the Church of Scientology. In addition to its controversial status as a religion and its troubling pattern of intimidation and litigation directed towards its foes, Scientology is well known as an organised opponent to psychiatry. This paper looks at Hubbard's science fiction work to help understand the evolution of Scientology's antipsychiatry stance, as well as the alternative to psychiatry offered by Hubbard. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/.
A Bespoke Single-Band Hubbard Model Material
Griffin, S M; Staar, P.; Schulthess, T. C.; Troyer, M.; Spaldin, N. A.
2015-01-01
The Hubbard model, which augments independent-electron band theory with a single parameter to describe electron-electron correlations, is widely regarded to be the `standard model' of condensed matter physics. The model has been remarkably successful at addressing a range of correlation effects in solids, but beyond one dimension its solution is intractable. Much current research aims, therefore, at finding appropriate approximations to the Hubbard model phase diagram. Here we take the new ap...
Fractional Quantum Hall Physics in Jaynes-Cummings-Hubbard Lattices
Hayward, Andrew L. C.; Martin, Andrew M.; Greentree, Andrew D.
2012-01-01
Jaynes-Cummings-Hubbard arrays provide unique opportunities for quantum emulation as they exhibit convenient state preparation and measurement, and in-situ tuning of parameters. We show how to realise strongly correlated states of light in Jaynes-Cummings-Hubbard arrays under the introduction of an effective magnetic field. The effective field is realised by dynamic tuning of the cavity resonances. We demonstrate the existence of Fractional Quantum Hall states by com- puting topological invar...
Extended Hubbard models for ultracold atoms in optical lattices
Energy Technology Data Exchange (ETDEWEB)
Juergensen, Ole
2015-06-05
In this thesis, the phase diagrams and dynamics of various extended Hubbard models for ultracold atoms in optical lattices are studied. Hubbard models are the primary description for many interacting particles in periodic potentials with the paramount example of the electrons in solids. The very same models describe the behavior of ultracold quantum gases trapped in the periodic potentials generated by interfering beams of laser light. These optical lattices provide an unprecedented access to the fundamentals of the many-particle physics that govern the properties of solid-state materials. They can be used to simulate solid-state systems and validate the approximations and simplifications made in theoretical models. This thesis revisits the numerous approximations underlying the standard Hubbard models with special regard to optical lattice experiments. The incorporation of the interaction between particles on adjacent lattice sites leads to extended Hubbard models. Offsite interactions have a strong influence on the phase boundaries and can give rise to novel correlated quantum phases. The extended models are studied with the numerical methods of exact diagonalization and time evolution, a cluster Gutzwiller approximation, as well as with the strong-coupling expansion approach. In total, this thesis demonstrates the high relevance of beyond-Hubbard processes for ultracold atoms in optical lattices. Extended Hubbard models can be employed to tackle unexplained problems of solid-state physics as well as enter previously inaccessible regimes.
Timothy J. Fahey; Pamela H. Templer; Bruce T. Anderson; John J. Battles; John L. Campbell; Charles T. Driscoll; Anthony R. Fusco; Mark B. Green; Karim-Aly S. Kassam; Nicholas L. Rodenhouse; Lindsey Rustad; Paul G. Schaberg; Matthew A. Vadeboncoeur
2015-01-01
Ecological research is increasingly concentrated at particular locations or sites. This trend reflects a variety of advantages of intensive, site-based research, but also raises important questions about the nature of such spatially delimited research: how well does site based research represent broader areas, and does it constrain scientific discovery? We provide an...
Brook trout passage performance through culverts
Goerig, Elsa; Castro-Santos, Theodore R.; Bergeron, Normand
2016-01-01
Culverts can restrict access to habitat for stream-dwelling fishes. We used passive integrated transponder telemetry to quantify passage performance of >1000 wild brook trout (Salvelinus fontinalis) attempting to pass 13 culverts in Quebec under a range of hydraulic and environmental conditions. Several variables influenced passage success, including complex interactions between physiology and behavior, hydraulics, and structural characteristics. The probability of successful passage was greater through corrugated metal culverts than through smooth ones, particularly among smaller fish. Trout were also more likely to pass at warmer temperatures, but this effect diminished above 15 °C. Passage was impeded at higher flows, through culverts with steep slopes, and those with deep downstream pools. This study provides insight on factors influencing brook trout capacity to pass culverts as well as a model to estimate passage success under various conditions, with an improved resolution and accuracy over existing approaches. It also presents methods that could be used to investigate passage success of other species, with implications for connectivity of the riverscape.
Stationary discrete solitons in a driven dissipative Bose-Hubbard chain
Naether, Uta; Quijandría, Fernando; García-Ripoll, Juan José; Zueco, David
2015-03-01
We demonstrate that stationary localized solutions (discrete solitons) exist in one-dimensional Bose-Hubbard lattices with gain and loss in a semiclassical regime. Stationary solutions, by definition, are robust and do not demand state preparation. Losses, unavoidable in experiments, are not a drawback, but a necessary ingredient for these modes to exist. The semiclassical calculations are complemented with their classical limit and dynamics based on a Gutzwiller ansatz. We argue that circuit quantum electrodynamic architectures are ideal platforms for realizing the physics developed here. Finally, within the input-output formalism, we explain how to experimentally access the different phases, including the solitons, of the chain.
Buys, D.J.; Hilderbrand, R.H.; Kershner, J.L.
2009-01-01
We evaluated the effects of various density treatments on adult fish growth and emigration rates between Bonneville cutthroat trout Oncorhynchus clarki utah and brook trout Salvelinus fontinalis in stream enclosures in Beaver Creek, Idaho, We used 3 density treatments (low, ambient, and high fish densities) to evaluate density-related effects and to ensure a response. Intraspecific ambient-density tests using cutthroat trout only were also performed. Results indicated an absence of cage effects in the stream enclosures and no differences in fish growth between ambient-density stream-enclosure fish and free-range fish. Brook trout outgrew and moved less than cutthroat trout in the stream enclosures, especially as density increased, In all 3 density treatments, brook trout gained more weight than cutthroat trout, with brook trout gaining weight in each density treatment and cutthroat trout losing weight at the highest density. At high densities, cutthroat trout attempted to emigrate more frequently than brook trout in sympatry and allopatry. We observed a negative correlation between growth and emigration for interspecific cutthroat trout, indicating a possible competitive response due to the presence of brook trout. We observed similar responses for weight and emigration in trials of allopatric cutthroat trout, indicating strong intraspecific effects as density increased. While cutthroat trout showed a response to experimental manipulation with brook trout at different densities, there has been long-term coexistence between these species in Beaver Creek, This system presents a unique opportunity to study the mechanisms that lead cutthroat trout to coexist with rather than be replaced by nonnative brook trout.
Spectrum of boundary states in the open Hubbard chain
Energy Technology Data Exchange (ETDEWEB)
Beduerftig, Gerald; Frahm, Holger [Institut fuer Theoretische Physik, Universitaet Hannover, Hannover (Germany)
1997-06-21
We use the Bethe ansatz solution for the one-dimensional Hubbard model with open boundary conditions and applied boundary fields to study the spectrum of bound states at the boundary. Depending on the strength of the boundary potentials, one finds that the true ground state contains a single charge or, for boundary potentials comparable with the Hubbard interaction, a pair of electrons in a bound state. If these are left unoccupied one finds holon and spinon bound states. We compute the finite size corrections to the low-lying energies in this system and use the predictions of boundary conformal field theory to study the exponents related to the orthogonality catastrophe. (author)
Time-dependent Gutzwiller theory for multiband Hubbard models.
Oelsen, E v; Seibold, G; Bünemann, J
2011-08-12
Based on the variational Gutzwiller theory, we present a method for the computation of response functions for multiband Hubbard models with general local Coulomb interactions. The improvement over the conventional random-phase approximation is exemplified for an infinite-dimensional two-band Hubbard model where the incorporation of the local multiplet structure leads to a much larger sensitivity of ferromagnetism on the Hund coupling. Our method can be implemented into local-density approximation and Gutzwiller schemes and will therefore be an important tool for the computation of response functions for strongly correlated materials.
Environmental contaminants in brook trout from Aroostook National Wildlife Refuge
US Fish and Wildlife Service, Department of the Interior — In June 2012, four brook trout (Salvelinus fontinalis) were collected by angling from Chapman Pond and East Loring Lake at Aroostook NWR in northeast Maine. Two...
Foote Brook Macroinvertebrate Biomonitoring - Phase 2 in Johnson, Vermont
Vermont Center for Geographic Information — In 2000, Foote Brook was identified as a high priority site for restoration after the extensive countywide stream stability study, Stream Stability Assessment of...
Great Smoky Mountains National Park Brook Trout Genetics
National Park Service, Department of the Interior — Great Smoky Mountains National Park (GRSM) is committed to monitoring ecological and evolutionary functions and processes of park ecosystems. Brook trout (Salvelinus...
VT Foote Brook Natural Channel Design Restoration 2001-2002
Vermont Center for Geographic Information — (Link to Metadata) The Foote Brook, located in Johnson, Vermont, is known to biologists and anglers as a high quality stream with significant natural reproduction of...
Foote Brook Macroinvertebrate Biomonitoring-Phase I in Johnson, Vermont
Vermont Center for Geographic Information — The Foote Brook Biomonitoring Project, Phase I geospatial dataset consists of data from the biomonitoring of benthic macroinvertebrates at three sites located along...
VT Foote Brook Natural Channel Design Restoration 2003
Vermont Center for Geographic Information — (Link to Metadata) The Foote Brook, located in Johnson, Vermont, is known to biologists and anglers as a high quality stream with significant natural reproduction of...
Mitochondrial dysfunction in Brooks-Wisniewski-Brown syndrome.
Morava, E.; Rodenburg, R.J.T.; Hol, F.A.; Meirleir, L. de; Seneca, S.; Busch, R.; Heuvel, L.P.W.J. van den; Smeitink, J.A.M.
2006-01-01
Brooks, Wisniewski, and Brown described a familial presentation of severe developmental retardation, speech delay, static encephalopathy with atrophic hydrocephalus, microcephaly, progressive spastic diplegia, a characteristic facial appearance, optic atrophy, and growth retardation associated with
Brook Trout Distribution, Pacific Northwest (updated March, 2006)
Pacific States Marine Fisheries Commission — This dataset is a record of fish distribution and activity for BROOK TROUT contained in the StreamNet database. This feature class was created based on linear event...
Phase-slip-induced dissipation in an atomic Bose-Hubbard system.
McKay, D; White, M; Pasienski, M; DeMarco, B
2008-05-01
Phase-slips control dissipation in many bosonic systems, determining the critical velocity of superfluid helium and the generation of resistance in thin superconducting wires. Technological interest has been largely motivated by applications involving nanoscale superconducting circuit elements, such as standards based on quantum phase-slip junctions. Although phase slips caused by thermal fluctuations at high temperatures are well understood, controversy remains over the role of phase slips in small-scale superconductors--in solids, problems such as uncontrolled noise sources and disorder complicate their study and application. Here we show that phase slips can lead to dissipation in a clean and well-characterized Bose-Hubbard system, by experimentally studying the transport of ultracold atoms trapped in an optical lattice. In contrast to previous work, we explore a low-velocity regime described by the three-dimensional Bose-Hubbard model that is unaffected by instabilities, and we measure the effect of temperature on the dissipation strength. The damping rate of atomic motion (the analogue of electrical resistance in a solid) in the confining parabolic potential is well fitted by a model that includes finite damping at zero temperature. The low-temperature behaviour is consistent with the theory of quantum tunnelling of phase slips, whereas at higher temperatures a crossover consistent with a transition to thermal activation of phase slips is evident. Motion-induced features reminiscent of vortices and vortex rings associated with phase slips are also observed in time-of-flight imaging. These results clarify the role of phase slips in superfluid systems. They may also be of relevance in understanding the source of metallic phases observed in thin films, or serve as a test bed for theories of bosonic dissipation based upon variants of the Bose-Hubbard model.
QUANTUM SIZE EFFECTS IN THE ATTRACTIVE HUBBARD-MODEL
BORMANN, D; SCHNEIDER, T; FRICK, M
1992-01-01
We investigate superconducting pair correlations in the attractive Hubbard model on a finite square lattice. Our aim is to understand the pronounced size dependence which they display in the weak and intermediate coupling regimes. These size effects originate from the electronic shell structure of f
Quantum symmetries induced by phonons in the Hubbard model
Energy Technology Data Exchange (ETDEWEB)
Montorsi, A.; Rasetti, M. (Theory Division, Los Alamos National Laboratories, Los Alamos, New Mexico 87545 (United States) Dipartimento di Fisica and Unita Istituto Nazionale di Fisica della Materia, Politecnico di Torino, I-10129 Torino (Italy))
1994-03-14
We show how the addition of a phonon field to the Hubbard model deforms the [ital superconducting] su(2) part of the global symmetry Lie algebra su(2)[direct product]su(2)/[ital openZ][sub 2], holding at half filling for the customary model, into a [ital quantum] [su(2)][sub [ital q
A bespoke single-band Hubbard model material
Griffin, S. M.; Staar, P.; Schulthess, T. C.; Troyer, M.; Spaldin, N. A.
2016-02-01
The Hubbard model, which augments independent-electron band theory with a single parameter to describe electron-electron correlations, is widely regarded to be the "standard model" of condensed-matter physics. The model has been remarkably successful at addressing a range of correlation phenomena in solids, but it neglects many behaviors that occur in real materials, such as phonons, long-range interactions, and, in its simplest form, multiorbital effects. Here, we use ab initio electronic structure methods to design a material whose Hamiltonian matches as closely as possible that of the single-band Hubbard model. Our motivation is to compare the measured properties of our new material to those predicted by reliable theoretical solutions of the Hubbard model to determine the relevance of the model in the description of real materials. After identifying an appropriate crystal class and several appropriate chemistries, we use density-functional theory and dynamical mean-field theory to screen for the desired electronic band structure and metal-insulator transition. We then explore the most promising candidates for structural stability and suitability for doping, and we propose specific materials for subsequent synthesis. Finally, we identify a regime—that should manifest in our bespoke material—in which the single-band Hubbard model on a triangular lattice exhibits exotic d -wave superconductivity.
Block Entanglement in the Single-Hole Hubbard Model
Institute of Scientific and Technical Information of China (English)
YAO Kai-Lun; SUN Xiao-Zhong; LIU Zu-Li; LI Yan-Chao; YU Li; GAO Guo-Ying
2006-01-01
@@ We investigate the distribution of the entanglement of the one-dimensional single-hole Hubbard model (HM)and study the relationship between the entanglement and quantum phase transition in the model. The von Neumann entropy of a block with neighbouring spins L for a single-hole HM is calculated using the densitymatrix renormalization group.
Strongly correlated flat-band systems: The route from Heisenberg spins to Hubbard electrons
Derzhko, Oleg; Richter, Johannes; Maksymenko, Mykola
2015-05-01
-correlated percolation problem, as well as the dispersion-driven ground-state ferromagnetism in flat-band Hubbard systems. Closely related studies and possible experimental realizations of the flat-band physics are also described briefly.
Nocera, A.; Patel, N. D.; Fernandez-Baca, J.; Dagotto, E.; Alvarez, G.
2016-11-01
We study the effects of charge degrees of freedom on the spin excitation dynamics in quasi-one-dimensional magnetic materials. Using the density matrix renormalization group method, we calculate the dynamical spin structure factor of the Hubbard model at half electronic filling on a chain and on a ladder geometry, and compare the results with those obtained using the Heisenberg model, where charge degrees of freedom are considered frozen. For both chains and two-leg ladders, we find that the Hubbard model spectrum qualitatively resembles the Heisenberg spectrum—with low-energy peaks resembling spinonic excitations—already at intermediate on-site repulsion as small as U /t ˜2 -3 , although ratios of peak intensities at different momenta continue evolving with increasing U /t converging only slowly to the Heisenberg limit. We discuss the implications of these results for neutron scattering experiments and we propose criteria to establish the values of U /t of quasi-one-dimensional systems described by one-orbital Hubbard models from experimental information.
Surface Effects on the Mott-Hubbard Transition in Archetypal V{2}O{3}.
Lantz, G; Hajlaoui, M; Papalazarou, E; Jacques, V L R; Mazzotti, A; Marsi, M; Lupi, S; Amati, M; Gregoratti, L; Si, L; Zhong, Z; Held, K
2015-12-04
We present an experimental and theoretical study exploring surface effects on the evolution of the metal-insulator transition in the model Mott-Hubbard compound Cr-doped V{2}O{3}. We find a microscopic domain formation that is clearly affected by the surface crystallographic orientation. Using scanning photoelectron microscopy and x-ray diffraction, we find that surface defects act as nucleation centers for the formation of domains at the temperature-induced isostructural transition and favor the formation of microscopic metallic regions. A density-functional theory plus dynamical mean-field theory study of different surface terminations shows that the surface reconstruction with excess vanadyl cations leads to doped, and hence more metallic, surface states, which explains our experimental observations.
Unconventional fermi surface instabilities in the kagome Hubbard model.
Kiesel, Maximilian L; Platt, Christian; Thomale, Ronny
2013-03-22
We investigate the competing Fermi surface instabilities in the kagome tight-binding model. Specifically, we consider on-site and short-range Hubbard interactions in the vicinity of van Hove filling of the dispersive kagome bands where the fermiology promotes the joint effect of enlarged density of states and nesting. The sublattice interference mechanism devised by Kiesel and Thomale [Phys. Rev. B 86, 121105 (2012)] allows us to explain the intricate interplay between ferromagnetic fluctuations and other ordering tendencies. On the basis of the functional renormalization group used to obtain an adequate low-energy theory description, we discover finite angular momentum spin and charge density wave order, a twofold degenerate d-wave Pomeranchuk instability, and f-wave superconductivity away from van Hove filling. Together, this makes the kagome Hubbard model the prototypical scenario for several unconventional Fermi surface instabilities.
A Simple Hubbard Model for the Excited States of Dibenzoterrylene
Sadeq, Z S
2016-01-01
We use a simple Hubbard model to characterize the electronic excited states of the dibenzoterrylene (DBT) molecule; we compute the excited state transition energies and oscillator strengths from the ground state to several singlet excited states. We consider the lowest singlet and triplet states of the molecule, examine their wavefunctions, and compute the density correlation functions that describe these states. We find that the DBT ground state is mostly a closed shell singlet with very slight radical character. We predict a relatively small singlet-triplet splitting of 0.75 eV, which is less than the mid-sized -acenes but larger than literature predictions for this state; this is because the Hubbard interaction makes a very small correction to the singlet and triplet states.
Entanglement entropies of the quarter filled Hubbard model
Calabrese, Pasquale; Essler, Fabian H. L.; Läuchli, Andreas M.
2014-09-01
We study Rényi and von Neumann entanglement entropies in the ground state of the one dimensional quarter-filled Hubbard model with periodic boundary conditions. We show that they exhibit an unexpected dependence on system size: for L = 4mod 8 the results are in agreement with expectations based on conformal field theory, while for L = 0mod 8 additional contributions arise. We show that these can be understood in terms of a ‘shell-filling’ effect and we develop a conformal field theory approach to calculate the additional contributions to the entropies. These analytic results are found to be in excellent agreement with density matrix renormalization group computations for weak Hubbard interactions. We argue that for larger interactions the presence of a marginal irrelevant operator in the spin sector strongly affects the entropies at the finite sizes accessible numerically and we present an effective way to take them into account.
The Quantum Inverse Scattering Method for Hubbard-like Models
Martins, M J
1997-01-01
This work is concerned with various aspects of the formulation of the quantum inverse scattering method for the one-dimensional Hubbard model. We first establish the essential tools to solve the eigenvalue problem for the transfer matrix of the classical ``covering'' Hubbard model within the algebraic Bethe Ansatz framework. The fundamental commutation rules exhibit a hidden 6-vertex symmetry which plays a crucial role in the whole algebraic construction. Next we apply this formalism to study the SU(2) highest weights properties of the eigenvectors and the solution of a related coupled spin model with twisted boundary conditions. The machinery developed in this paper is applicable to many other models, and as an example we present the algebraic solution of the Bariev XY coupled model.
Cleanth Brooks at the United States Air Force Academy April 11-12, 1978,
1980-01-01
April 1966. The Writer and His Community. Glasgow: Jackson , 1968. The Twenty-First W. P. Fer Memorial Lecture delivered in the University of Glasgow...Brooks & Warren. N. Y.: Crofts 119431. The Correspondence of Thomas Percy . General Editors, David Nichol Smith & Brooks. 5 vols. Baton Rouge: LSU Press...1944-57. Brooks edited vol. 11, The Correspondence of Thomas Percy and Richard Farmer [19461. Understanding Drama. By Brooks & Robert B. Heilman. N
Aerospace medicine at Brooks AFB, TX: hail and farewell.
Nunneley, Sarah A; Webb, James T
2011-05-01
With the impending termination of USAF operations at Brooks Air Force Base (AFB) in San Antonio, TX, it is time to consider its historic role in Aerospace Medicine. The base was established in 1917 as a flight training center for the U.S. Army Air Service and in 1926 became home to its School of Aviation Medicine. The school moved to San Antonio's Randolph Field in 1931, but in 1959 it returned to Brooks where it occupied new facilities to support its role as a national center for U.S. Air Force aerospace medicine, including teaching, clinical medicine, and research. The mission was then expanded to encompass support of U.S. military and civilian space programs. With the abrupt termination of the military space program in 1969, research at Brooks focused on clinical aviation medicine and support of advanced military aircraft while continuing close cooperation with NASA in support of orbital spaceflight and the journey to the Moon. Reorganization in the 1990s assigned all research functions at Brooks to the Human Systems Division and its successors, leaving to USAFSAM the missions related to clinical work and teaching. In 2002 the USAF and the city of San Antonio implemented shared operation of Brooks as a "City-Base" in the hope of deflecting threatened closure. Nevertheless, under continuing pressure to consolidate military facilities in the United States, the 2005 Base Closure and Realignment Commission ordered Brooks closed by 2011, with its aerospace medicine functions relocated to new facilities at Wright-Patterson AFB in Dayton, OH.
Exact Numerical Solutions of Bose-Hubbard Model
Institute of Scientific and Technical Information of China (English)
ZHANG Dan; PAN Feng
2004-01-01
Hamiltonian of a one-dimensional Bose-Hubbard model is re-formulated by using differential realization of the boson algebra. Energy matrices can then be generated systematically by using a Mathematica package. The output can be taken as the input of other diagonalization codes. As examples, exact energy eigenvalues and the corresponding wavefunctions for some cases are obtained with a Fortran diagonalization code. Phase transition of the model is analyzed.
Negativity in the Extended Hubbard Model under External Magnetic Field
Institute of Scientific and Technical Information of China (English)
YANG Zhen; NING Wen-Qiang
2008-01-01
We exactly calculate the negativity,a measurement of entanglement,in the two-site extended Hubbard model with external magnetic field.Its behaviour at different temperatures is presented.The negativity reduces with the increasing temperature or with the increasing uniform external magnetic field.It is also found that a non-uniform external magnetic field can be used to modulate or to increase the negativity.
Gutzwiller variational theory for the Hubbard model with attractive interaction.
Bünemann, Jörg; Gebhard, Florian; Radnóczi, Katalin; Fazekas, Patrik
2005-06-29
We investigate the electronic and superconducting properties of a negative-U Hubbard model. For this purpose we evaluate a recently introduced variational theory based on Gutzwiller-correlated BCS wavefunctions. We find significant differences between our approach and standard BCS theory, especially for the superconducting gap. For small values of |U|, we derive analytical expressions for the order parameter and the superconducting gap which we compare to exact results from perturbation theory.
Damping of Bloch oscillations in the Hubbard model.
Eckstein, Martin; Werner, Philipp
2011-10-28
Using nonequilibrium dynamical mean-field theory, we study the isolated Hubbard model in a static electric field in the limit of weak interactions. Linear response behavior is established at long times, but only if the interaction exceeds a critical value, below which the system exhibits an ac-type response with Bloch oscillations. The transition from ac to dc response is defined in terms of the universal long-time behavior of the system, which does not depend on the initial condition.
The one-dimensional extended Bose-Hubbard model
Indian Academy of Sciences (India)
Ramesh V Pai; Rahul Pandit
2003-10-01
We use the finite-size, density-matrix-renormalization-group (DMRG) method to obtain the zero-temperature phase diagram of the one-dimensional, extended Bose-Hubbard model, for mean boson density ρ = 1, in the - plane ( and are respectively, onsite and nearest-neighbour repulsive interactions between bosons). The phase diagram includes superfluid (SF), bosonic-Mott-insulator (MI), and mass-density-wave (MDW) phases. We determine the natures of the quantum phase transitions between these phases.
Mujeres malditas pintadas de gris : el arte de Romaine Brooks
Serrano de Haro, Amparo
1994-01-01
A pesar de su morbosa elegancia y fatídica sensualidad, los retratos de Romaine Brooks, grises como la nostalgia, son aceptados y considerados dignos de atención crítica desde hace muy poco tiempo. Romaine Brooks,norteamericana nacida en Roma en 1874, cuyas pinturas gozaron de una gran popularidad en el París de principios de siglo XX, fue prácticamente olvidada a partir de los años treinta. La donación de buena parte de su obra al Museo Nacional de Washington a fines de los...
Bose-Hubbard model on a checkerboard superlattice
Iskin, Menderes
2011-05-01
We study the ground-state phases of the Bose-Hubbard model on a checkerboard superlattice in two dimensions, including the superfluid phase and the Mott and charge-density-wave insulators. First, we discuss the single-particle Hofstadter problem, and show that the presence of a checkerboard superlattice gives rise to a magnetic flux-independent energy gap in the excitation spectrum. Then, we consider the many-particle problem, and derive an analytical mean-field expression for the superfluid-Mott and superfluid-charge-density-wave insulator phase transition boundaries. Finally, since the phase diagram of the Bose-Hubbard model on a checkerboard superlattice is in many ways similar to that of the extended Bose-Hubbard model, we comment on the effects of magnetic field on the latter model, and derive an analytical mean-field expression for the superfluid-insulator phase transition boundaries as well. This work is supported by Marie Curie International Reintegration Grant (FP7-PEOPLE-IRG-2010-268239).
Functional renormalization for antiferromagnetism and superconductivity in the Hubbard model
Energy Technology Data Exchange (ETDEWEB)
Friederich, Simon
2010-12-08
Despite its apparent simplicity, the two-dimensional Hubbard model for locally interacting fermions on a square lattice is widely considered as a promising approach for the understanding of Cooper pair formation in the quasi two-dimensional high-T{sub c} cuprate materials. In the present work this model is investigated by means of the functional renormalization group, based on an exact flow equation for the effective average action. In addition to the fermionic degrees of freedom of the Hubbard Hamiltonian, bosonic fields are introduced which correspond to the different possible collective orders of the system, for example magnetism and superconductivity. The interactions between bosons and fermions are determined by means of the method of ''rebosonization'' (or ''flowing bosonization''), which can be described as a continuous, scale-dependent Hubbard-Stratonovich transformation. This method allows an efficient parameterization of the momentum-dependent effective two-particle interaction between fermions (four-point vertex), and it makes it possible to follow the flow of the running couplings into the regimes exhibiting spontaneous symmetry breaking, where bosonic fluctuations determine the types of order which are present on large length scales. Numerical results for the phase diagram are presented, which include the mutual influence of different, competing types of order. (orig.)
Clarification to Brook and Willoughby (2016).
2016-07-01
Reports an error in "Social anxiety and alcohol use across the university years: Adaptive and maladaptive groups" by Christina A. Brook and Teena Willoughby (Developmental Psychology, 2016[May], Vol 52[5], 835-845). In the article, Figures 1 and 2 and Tables 1, 2, 3, and 4 were inadvertently designated as supplemental material. The figures and tables are present in the erratum. (The following abstract of the original article appeared in record 2016-13161-001.) University/college can be a challenging time as students face developmental tasks such as building new social networks and achieving academically. Social anxiety may be disadvantageous in this setting given that social situations often include drinking and individuals with social anxiety tend to self-medicate through alcohol use. However, findings are mixed as to whether the association between social anxiety and alcohol use is positive or negative. To clarify the nature of this association, we used a person-centered longitudinal analysis to identify student groups based on levels of social anxiety symptoms and alcohol consumption. Undergraduates (N = 1132, 70.5% female, Mage = 19.06 at Time 1) enrolled in university completed a survey assessing social anxiety and alcohol use over 3 years, and psychosocial functioning and emotion coping behaviors at Time 1. Two out of 5 groups were identified with higher levels of social anxiety, 1 with moderately low alcohol use, and the other with moderately high alcohol use. Both groups reported higher levels of general anxiety, depressive symptoms, behavioral inhibition, emotional reactivity, daily hassles, and lower levels of social ties at Time 1 than the 3 groups with lower levels of social anxiety. Furthermore, the social anxiety-alcohol use group reported significantly lower academic grades and was more likely to endorse problematic emotion coping behaviors (e.g., self-injury) than the social anxiety-low alcohol use group. These results not only help explain the
Thermodynamics of the Hubbard model on stacked honeycomb and square lattices
Imriška, Jakub; Gull, Emanuel; Troyer, Matthias
2016-07-01
We present a numerical study of the Hubbard model on simply stacked honeycomb and square lattices, motivated by a recent experimental realization of such models with ultracold atoms in optical lattices. We perform simulations with different interlayer coupling and interaction strengths and obtain Néel transition temperatures and entropies. We provide data for the equation of state to enable comparisons of experiments and theory. We find an enhancement of the short-range correlations in the anisotropic lattices compared to the isotropic cubic lattice, in parameter regimes suitable for the interaction driven adiabatic cooling. Supplementary material in the form of one zip file available from the Jounal web page at http://dx.doi.org/10.1140/epjb/e2016-70146-y
Phase coexistence and Mott metal-insulator transition in the doped Hubbard-Holstein model
Moradi Kurdestany, Jamshid; Satpathy, Sashi
2015-03-01
Motivated by recent progress in the understanding of the Mott insulators away from half filling [?], often observed in the oxide materials, we study the role of the electron-lattice interaction vis-à-vis the electron correlations by studying the one-band Hubbard-Holstein model using the Gutzwiller variational method. Our theory predicts phase separation for sufficiently strong electron-lattice interaction, which however is frustrated in the solid due to the long-range Coulomb interaction of the dopant atoms, resulting in puddles of metallic phases embedded in the insulating matrix. Metallic state occurs when the volume fraction of the metallic phase exceeds the percolation threshold, as the dopant concentration is increased. Connection is made with the experimentally observed metal-insulator transition in the complex oxides.
Okugawa, Seigo; Masu, Hyuma; Yamaguchi, Kentaro; Takeda, Kei
2005-12-09
[reactions: see text] The reaction of delta-silyl-gamma,delta-epoxypentanenitrile derivatives 9-12 with a base and an alkylating agent affords (Z)-delta-siloxy-gamma,delta-unsaturated pentanenitrile derivatives via a tandem process that involves the formation of a cyclopropane derivative by epoxy nitrile cyclization followed by Brook rearrangement and an anion-induced cleavage of the cyclopropane ring. Exclusive formation of a (Z)-derivative from trans-epoxides is explained by the reaction pathway that involves a backside displacement of the epoxide by the alpha-nitrile carbanion and the O-Si bond formation followed by concerted processes involving Brook rearrangement and the anti-mode of eliminative ring fission of the cyclopropane from the rotamer 19. The fact that (E)-isomers are exclusively obtained from cis-epoxides and alpha-cyclopropyl-alpha-silylcarbinol derivative 26 provides experimental support for the proposed pathway.
Feasibility of target communities in a Dutch brook valley system
Prins, AH; Bekker, RM
As a reaction to the ongoing deterioration of nature conservation interest in The Netherlands, an offensive nature strategy was formulated in the 1990 Nature Policy Plan. In this Plan, target communities and target plant species are mentioned. For the 'Drentse A brook valley system', target
Feasibility of target communities in a Dutch brook valley system
Prins, AH; Bekker, RM
1998-01-01
As a reaction to the ongoing deterioration of nature conservation interest in The Netherlands, an offensive nature strategy was formulated in the 1990 Nature Policy Plan. In this Plan, target communities and target plant species are mentioned. For the 'Drentse A brook valley system', target communit
Induction and viability of tetraploids in brook trout (Salvelinus fontinalis)
Brook trout (Salvelinus fontinalis) populations are threatened by introduction of invasive species, habitat loss, and habitat degradation in their native range; and are a problem invasive species in western Unites States and Canada, and in Europe. Stocking sterile triploids has been promoted as an ...
Patterns of streamwater acidity in Lye Brook Wilderness, Vermont, USA
John L. Campbell; Christopher Eagar; William H. McDowell
2002-01-01
Under the United States Clean Air Act Amendments of 1977, a class I designation safeguards wilderness areas from the negative effects of new sources of air pollution. We monitored streamwater chemistry in the class I Lye Brook Wilderness in southwestern Vermont from May 1994 through August 1995. Stream samples were collected biweekly at nine sampling locations...
Documentary Linguistics and Computational Linguistics: A Response to Brooks
Bird, Steven; Chiang, David; Frowein, Friedel; Hanke, Florian; Vaswani, Ashish
2015-01-01
In mid-2012, the authors organized a two-week workshop in Papua New Guinea to provide training in basic techniques and technologies for language documentation, and to gain understanding of how these technologies might be improved in the future. An assessment of the workshop was conducted by Brooks with the central idea that the workshop's…
Investigation of a four-body coupling in the one-dimensional extended Penson-Kolb-Hubbard model
Ding, Hanqin; Ma, Xiaojuan; Zhang, Jun
2017-09-01
The experimental advances in cold fermion gases motivates the investigation of a one-dimensional (1D) correlated electronic system by incorporating a four-body coupling. Using the low-energy field theory scheme and focusing on the weak-coupling regime, we extend the 1D Penson-Kolb-Hubbard (PKH) model at half filling. It is found that the additional four-body interaction may significantly modify the quantum phase diagram, favoring the presence of the superconducting phase even in the case of two-body repulsions.
Energy Technology Data Exchange (ETDEWEB)
Meyer, Kevin A.; Lamansky, Jr., James A.; Schill, Daniel J.
2006-01-26
In the western United States, exotic brook trout Salvelinus fontinalis frequently have a deleterious effect on native salmonids, and biologists often attempt to remove brook trout from streams by means of electrofishing. Although the success of such projects typically is low, few studies have assessed the underlying mechanisms of failure, especially in terms of compensatory responses. A multiagency watershed advisory group (WAG) conducted a 3-year removal project to reduce brook trout and enhance native salmonids in 7.8 km of a southwestern Idaho stream. We evaluated the costs and success of their project in suppressing brook trout and looked for brook trout compensatory responses, such as decreased natural mortality, increased growth, increased fecundity at length, and earlier maturation. The total number of brook trout removed was 1,401 in 1998, 1,241 in 1999, and 890 in 2000; removal constituted an estimated 88% of the total number of brook trout in the stream in 1999 and 79% in 2000. Although abundance of age-1 and older brook trout declined slightly during and after the removals, abundance of age-0 brook trout increased 789% in the entire stream 2 years after the removals ceased. Total annual survival rate for age-2 and older brook trout did not decrease during the removals, and the removals failed to produce an increase in the abundance of native redband trout Oncorhynchus mykiss gairdneri. Lack of a meaningful decline and unchanged total mortality for older brook trout during the removals suggest that a compensatory response occurred in the brook trout population via reduced natural mortality, which offset the removal of large numbers of brook trout. Although we applaud WAG personnel for their goal of enhancing native salmonids by suppressing brook trout via electrofishing removal, we conclude that their efforts were unsuccessful and suggest that similar future projects elsewhere over such large stream lengths would be costly, quixotic enterprises.
Off-diagonal long-range order in generalized Hubbard models
Michielsen, Kristel; Raedt, Hans De
1997-01-01
We present stochastic diagonalization results for the ground-state energy and the largest eigenvalue of the two-fermion density matrix of the BCS reduced Hamiltonian, the Hubbard model, and the Hubbard model with correlated hopping. The system-size dependence of this eigenvalue is used to study the
Exact solutions of the high dimensional hard-core Fermi-Hubbard model
Institute of Scientific and Technical Information of China (English)
潘峰; 戴连荣
2001-01-01
A simple algebraic approach to exact solutions of the hard-core Fermi-Hubbard model is proposed. Excitation energies and the corresponding wavefunctions of the hard-core Fermi-Hubbard model with nearest neighbor hopping cases in high dimension are obtained by using this method, which manifests that the model is exactly solvable in any dimension.
Bethe Ansatz Solutions of the Bose-Hubbard Dimer
Directory of Open Access Journals (Sweden)
Jon Links
2006-12-01
Full Text Available The Bose-Hubbard dimer Hamiltonian is a simple yet effective model for describing tunneling phenomena of Bose-Einstein condensates. One of the significant mathematical properties of the model is that it can be exactly solved by Bethe ansatz methods. Here we review the known exact solutions, highlighting the contributions of V.B. Kuznetsov to this field. Two of the exact solutions arise in the context of the Quantum Inverse Scattering Method, while the third solution uses a differential operator realisation of the su(2 Lie algebra.
A polaritonic two-component Bose-Hubbard model
Energy Technology Data Exchange (ETDEWEB)
Hartmann, M J; Brandao, F G S L; Plenio, M B [Institute for Mathematical Sciences, Imperial College London, 53 Exhibition Road, SW7 2PE (United Kingdom)], E-mail: m.hartmann@imperial.ac.uk
2008-03-15
We demonstrate that polaritons in an array of interacting micro-cavities with strong atom-photon coupling can form a two-component Bose-Hubbard model in which both polariton species are protected against spontaneous emission as their atomic part is stored in two ground states of the atoms. The parameters of the effective model can be tuned via the driving strength of external lasers and include attractive and repulsive polariton interactions. We also describe a method to measure the number statistics in one cavity for each polariton species independently.
Exact diagonalization: the Bose-Hubbard model as an example
Zhang, J. M.; Dong, R. X.
2010-05-01
We take the Bose-Hubbard model to illustrate exact diagonalization techniques in a pedagogical way. We follow the route of first generating all the basis vectors, then setting up the Hamiltonian matrix with respect to this basis and finally using the Lanczos algorithm to solve low lying eigenstates and eigenvalues. Emphasis is placed on how to enumerate all the basis vectors and how to use the hashing trick to set up the Hamiltonian matrix or matrices corresponding to other quantities. Although our route is not necessarily the most efficient one in practice, the techniques and ideas introduced are quite general and may find use in many other problems.
Quantum symmetries induced by phonons in the Hubbard model
Montorsi, Arianna; Rasetti, Mario
1994-03-01
We show how the addition of a phonon field to the Hubbard model deforms the superconducting su(2) part of the global symmetry Lie algebra su(2)⊗su(2)/openZ2, holding at half filling for the customary model, into a quantum [su(2)]q symmetry, holding for a filling which depends on the electron-phonon interaction strength. Such symmetry originates in the feature that in the presence of phonons the hopping amplitude turns out to depend on the coupling strength. The states generated by resorting to this q symmetry exhibit both off-diagonal long-range order and pairing.
Quantum symmetries induced by phonons in the Hubbard model
Montorsi, Arianna; Rasetti, Mario
1994-01-01
We show how the addition of a phonon field to the Hubbard model deforms the superconducting su(2) part of the global symmetry Lie algebra su(2)⊗su(2)/openZ2, holding at half filling for the customary model, into a quantum [su(2)]q symmetry, holding for a filling which depends on the electron-phonon interaction strength. Such symmetry originates in the feature that in the presence of phonons the hopping amplitude turns out to depend on the coupling strength. The states generated by resorting t...
Solving the Bose-Hubbard Model with Machine Learning
Saito, Hiroki
2017-09-01
Motivated by the recent successful application of artificial neural networks to quantum many-body problems [G. Carleo and M. Troyer, doi.org/10.1126/science.aag2302" xlink:type="simple">Science 355, 602 (2017)], a method to calculate the ground state of the Bose-Hubbard model using a feedforward neural network is proposed. The results are in good agreement with those obtained by exact diagonalization and the Gutzwiller approximation. The method of neural-network quantum states is promising for solving quantum many-body problems of ultracold atoms in optical lattices.
Desarrollo No Perturbativo para el Modelo de Hubbard Generalizado
Directory of Open Access Journals (Sweden)
Oscar P. Zandron
2010-01-01
Full Text Available Se extienden a un estado superconductor nuestros resultados previamente obtenidos para un estado normal en el marco del formalismo Lagrangiano. Se considera la expansión noperturbativa a N grande aplicada a un modelo generalizado de Hubbard describiendo N bandas degeneradas correlacionadas. Se obtienen la diagramática Feynman del modelo y se calculan y analizan las cantidades físicas renormalizadas. Nuestro propósito es obtener la corrección 1/N de los propagadores bosónico y fermiónico renormalizados cuando se tiene en cuenta un estado de condensación de pares de Cooper.
Specific heat of a non-local attractive Hubbard model
Energy Technology Data Exchange (ETDEWEB)
Calegari, E.J., E-mail: eleonir@ufsm.br [Laboratório de Teoria da Matéria Condensada, Departamento de Física, UFSM, 97105-900, Santa Maria, RS (Brazil); Lobo, C.O. [Laboratório de Teoria da Matéria Condensada, Departamento de Física, UFSM, 97105-900, Santa Maria, RS (Brazil); Magalhaes, S.G. [Instituto de Física, Universidade Federal Fluminense, Av. Litorânea s/n, 24210, 346, Niterói, Rio de Janeiro (Brazil); Chaves, C.M.; Troper, A. [Centro Brasileiro de Pesquisas Físicas, Rua Xavier Sigaud 150, 22290-180, Rio de Janeiro, RJ (Brazil)
2013-10-01
The specific heat C(T) of an attractive (interaction G<0) non-local Hubbard model is investigated within a two-pole approximation that leads to a set of correlation functions, which play an important role as a source of anomalies as the pseudogap. For a giving range of G and n{sub T} (where n{sub T}=n{sub ↑}+n{sub ↓}), the specific heat as a function of the temperature presents a two peak structure. Nevertehelesss, the presence of a pseudogap eliminates the two peak structure. The effects of the second nearest-neighbor hopping on C(T) are also investigated.
Nonlocal order parameters for the 1D Hubbard model.
Montorsi, Arianna; Roncaglia, Marco
2012-12-07
We characterize the Mott-insulator and Luther-Emery phases of the 1D Hubbard model through correlators that measure the parity of spin and charge strings along the chain. These nonlocal quantities order in the corresponding gapped phases and vanish at the critical point U(c)=0, thus configuring as hidden order parameters. The Mott insulator consists of bound doublon-holon pairs, which in the Luther-Emery phase turn into electron pairs with opposite spins, both unbinding at U(c). The behavior of the parity correlators is captured by an effective free spinless fermion model.
Mott Quantum Criticality in the Anisotropic 2D Hubbard Model
Lenz, Benjamin; Manmana, Salvatore R.; Pruschke, Thomas; Assaad, Fakher F.; Raczkowski, Marcin
2015-01-01
We present evidence for Mott quantum criticality in an anisotropic two-dimensional system of coupled Hubbard chains at half-filling. In this scenario emerging from variational cluster approximation and cluster dynamical mean-field theory, the interchain hopping $t_{\\perp}$ acts as a control parameter driving the second-order critical end point $T_c$ of the metal-insulator transition down to zero at $t_{\\perp}^{c}/t\\simeq 0.2$. Below $t_{\\perp}^{c}$, the volume of the hole and electron Fermi p...
Operating with External Arguments of Douady and Hubbard
Directory of Open Access Journals (Sweden)
G. Pastor
2007-01-01
Full Text Available The external arguments of the external rays theory of Douady and Hubbard is a valuable tool in order to analyze the Mandelbrot set, a typical case of discrete dynamical system used to study nonlinear phenomena. We suggest here a general method for the calculation of the external arguments of external rays landing at the hyperbolic components root points of the Mandelbrot set. Likewise, we present a general method for the calculation of the external arguments of external rays landing at Misiurewicz points.
Fermion Coherent State Studies of One-Dimensional Hubbard Model
Institute of Scientific and Technical Information of China (English)
LIN Ji; GAO Xian-Long; WANG Ke-Lin
2007-01-01
We present a comparative study of the ground state of the one-dimensional Hubbard model. We first use a new fermion coherent state method in the framework of Fermi liquid theory by introducing a hole operator and considering the interactions of two pairs electrons and holes. We construct the ground state of the Hubbard model as ｜〉 = [f + ∑′ψc+k1σ1 h+k2σ2 c+k3σ3 h+k4σ4 ∏exp(ρc+k1σ1 h+k2σ2)] [〉0, where ψ and ρ are the coupling constants. Our results are then compared to those of variational methods, density functional theory based on the exact solvable Bethe ansatz solutions, variational Monto-Carlo method (VMC) as well as to the exact result of the infinite system. We find satisfactory agreement between the fermion coherent state scheme and the VMC data, and provide a new picture to deal with the strongly correlated system.
Mujeres malditas pintadas de gris : el arte de Romaine Brooks
Directory of Open Access Journals (Sweden)
Amparo Serrano de Haro
1994-01-01
Full Text Available A pesar de su morbosa elegancia y fatídica sensualidad, los retratos de Romaine Brooks, grises como la nostalgia, son aceptados y considerados dignos de atención crítica desde hace muy poco tiempo. Romaine Brooks,norteamericana nacida en Roma en 1874, cuyas pinturas gozaron de una gran popularidad en el París de principios de siglo XX, fue prácticamente olvidada a partir de los años treinta. La donación de buena parte de su obra al Museo Nacional de Washington a fines de los años 60 y la exposición antológica de su obra en 1971 (un año después de su muerte, iniciaron lo que sería un proceso de recuperación de su figura y su pintura.
Hubbard Model Approach to X-ray Spectroscopy
Ahmed, Towfiq
We have implemented a Hubbard model based first-principles approach for real-space calculations of x-ray spectroscopy, which allows one to study excited state electronic structure of correlated systems. Theoretical understanding of many electronic features in d and f electron systems remains beyond the scope of conventional density functional theory (DFT). In this work our main effort is to go beyond the local density approximation (LDA) by incorporating the Hubbard model within the real-space multiple-scattering Green's function (RSGF) formalism. Historically, the first theoretical description of correlated systems was published by Sir Neville Mott and others in 1937. They realized that the insulating gap and antiferromagnetism in the transition metal oxides are mainly caused by the strong on-site Coulomb interaction of the localized unfilled 3d orbitals. Even with the recent progress of first principles methods (e.g. DFT) and model Hamiltonian approaches (e.g., Hubbard-Anderson model), the electronic description of many of these systems remains a non-trivial combination of both. X-ray absorption near edge spectra (XANES) and x-ray emission spectra (XES) are very powerful spectroscopic probes for many electronic features near Fermi energy (EF), which are caused by the on-site Coulomb interaction of localized electrons. In this work we focus on three different cases of many-body effects due to the interaction of localized d electrons. Here, for the first time, we have applied the Hubbard model in the real-space multiple scattering (RSGF) formalism for the calculation of x-ray spectra of Mott insulators (e.g., NiO and MnO). Secondly, we have implemented in our RSGF approach a doping dependent self-energy that was constructed from a single-band Hubbard model for the over doped high-T c cuprate La2-xSrxCuO4. Finally our RSGF calculation of XANES is calculated with the spectral function from Lee and Hedin's charge transfer satellite model. For all these cases our
Institute of Scientific and Technical Information of China (English)
中底为王
2012-01-01
在跑鞋品牌里要论谁最具专业科技性，身为“四大跑鞋品牌”之一的BROOKS 相信是很多跑步迷心中的首选。2011年BROOKS推出了极具创新精神的中底缓震技术DNA,为整个跑步界投下了重磅炸弹，
A geologic framework for mineralization in the western Brooks Range
Young, Lorne E.
2004-01-01
The Brooks Range is a 950-km-long north-vergent fold and thrust belt, which was formed during Mesozoic convergence of the continental Arctic Alaska terrane and the oceanic Angayucham terrane and was further shortened and uplifted in Tertiary time. The Arctic Alaska terrane consists of parautochthonous rocks and the Endicott Mountains and De Long Mountains subterranes. The Endicott Mountains allochthon of the western Brooks Range is the setting for many sulfide and barite occurrences, such as the supergiant Red Dog zinc-lead mine. Mineralization is sediment hosted and most commonly is present in black shale and carbonate turbidites of the Mississippian Kuna Formation. The reconstructed Kuna basin is a 200 by +600 km feature that represents the culmination of a remarkable chain of events that includes three fluvial-deltaic and two or more orogenic cycles, Middle Devonian to Mississippian episodes of extension and igneous activity, and the emergence of a seaward Lower Proterozoic landmass that may have constituted a barrier to marine circulation. Mississippian extension and related horst-and-graben architecture in the western Brooks Range is manifested in part by strong facies variability between coeval units of allochthons and structural plates. Shallow marine to possibly nonmarine arkose, platform to shelf carbonate, slope-to-basin shale, chert and carbonate turbidites, and submarine volcanic rocks are all represented in Mississippian time. The structural setting of Mississippian sedimentation, volcanism, and mineralization in the Kuna basin may be comparable to documented Devono-Mississippian extensional sags or half-grabens in the subsurface north of the Brooks Range. Climate, terrestrial ecosystems, multiple fluvial-deltaic aquifers, and structural architecture affected the liberation, movement, and redeposition of metals in ways that are incompletely understood.
Consiglio, Anthony; Tian, Zhiting
2016-11-01
The wide bandgap semiconductor, ZnO, has gained interest recently as a promising option for use in power electronics such as thermoelectric and piezoelectric generators, as well as optoelectronic devices. Though much work has been done to improve its electronic properties, relatively little is known of its thermal transport properties with large variations in measured thermal conductivity. In this study, we examine the effects of a Hubbard corrected energy functional on the lattice thermal conductivity of wurtzite ZnO calculated using density functional theory and an iterative solution to the Boltzmann transport equation. Showing good agreement with existing experimental measurements, and with a detailed analysis of the mode-dependence and phonon properties, the results from this study highlight the importance of the Hubbard correction in calculations of thermal transport properties of materials with strongly correlated electron systems.
Energy Technology Data Exchange (ETDEWEB)
Olalde-Velasco, P; Jimenez-Mier, J; Denlinger, JD; Hussain, Z; Yang, WL
2011-07-11
We report the most direct experimental verification of Mott-Hubbard and charge-transfer insulators through x-ray emission spectroscopy in transition-metal (TM) fluorides. The p-d hybridization features in the spectra allow a straightforward energy alignment of the anion-2p and metal-3d valence states, which visually shows the difference between the two types of insulators. Furthermore, in parallel with the theoretical Zaanen-Sawatzky-Allen diagram, a complete experimental systematics of the 3d Coulomb interaction and the 2p-3d charge-transfer energy is reported and could serve as a universal experimental trend for other TM systems including oxides.
Broad-scale patterns of Brook Trout responses to introduced Brown Trout in New York
McKenna, James E.; Slattery, Michael T.; Kean M. Clifford,
2013-01-01
Brook Trout Salvelinus fontinalis and Brown Trout Salmo trutta are valuable sport fish that coexist in many parts of the world due to stocking introductions. Causes for the decline of Brook Trout within their native range are not clear but include competition with Brown Trout, habitat alteration, and repetitive stocking practices. New York State contains a large portion of the Brook Trout's native range, where both species are maintained by stocking and other management actions. We used artificial neural network models, regression, principal components analysis, and simulation to evaluate the effects of Brown Trout, environmental conditions, and stocking on the distribution of Brook Trout in the center of their native range. We found evidence for the decline of Brook Trout in the presence of Brown Trout across many watersheds; 22% of sampled reaches where both species were expected to occur contained only Brown Trout. However, a model of the direct relationship between Brook Trout and Brown Trout abundance explained less than 1% of data variation. Ordination showed extensive overlap of Brook Trout and Brown Trout habitat conditions, with only small components of the hypervolume (multidimensional space) being distinctive. Subsequent analysis indicated higher abundances of Brook Trout in highly forested areas, while Brown Trout were more abundant in areas with relatively high proportions of agriculture. Simulation results indicated that direct interactions and habitat conditions were relatively minor factors compared with the effects of repeated stocking of Brown Trout into Brook Trout habitat. Intensive annual stocking of Brown Trout could eliminate resident Brook Trout in less than a decade. Ecological differences, harvest behavior, and other habitat changes can exacerbate Brook Trout losses. Custom stocking scenarios with Brown Trout introductions at relatively low proportions of resident Brook Trout populations may be able to sustain healthy populations of both
Marine Geophysical Surveying Along the Hubbard Glacier Terminus, Southeast Alaska
Goff, J. A.; Davis, M.; Gulick, S. P.; Lawson, D. E.; Willems, B. A.
2010-12-01
Tidewater glaciers are a challenging environment for marine investigations, owing to the dangers associated with calving and restrictions on operations due to dense floating ice. We report here on recent efforts to conduct marine geophysical surveys proximal to the ice face of Hubbard Glacier, in Disenchantment Bay, Alaska. Hubbard is an advancing tidewater glacier that has twice recently (1986 and 2002) impinged on Gilbert Point, which separates Russell Fiord from Disenchantment Bay, thereby temporarily creating a glacially-dammed Russell Lake. Continued advance will likely form a more permanent dam, rerouting brackish outflow waters into the Situk River, near Yakutat, Alaska. Our primary interest is in studying the development and motion of the morainal bank which, for an advancing tidewater glacier, stabilizes it against rapid retreat. For survey work, we operated with a small, fast, aluminum-hulled vessel and a captain experienced in operating in ice-bound conditions, providing a high margin of safety and maneuverability. Differencing of multibeam bathymetric data acquired in different years can identify and quantify areas of deposition and erosion on the morainal bank front and in Disenchantment Bay proper, where accumulation rates are typically > 1 m/yr within 1 km of the glacier terminus. The advance or retreat rate of the morainal bank can be determined by changes in the bed elevation through time; we document advance rates that average > 30 m/yr in Disenchantment Bay, but which vary substantially over different time periods and at different positions along the ice face. Georeferencing of available satellite imagery allows us to directly compare the position of the glacial terminus with the position of the morainal bank. From 1978 to 1999, and then to 2006, the advances in terminus and morainal bank positions were closely synchronized along the length of the glacier face. In the shallower Russell Fiord side of the terminus, a sediment ridge was mapped both
The physiological response of diploid and triploid brook trout to exhaustive exercise.
Hyndman, C A; Kieffer, J D; Benfey, T J
2003-01-01
Using triploidy as an experimental model, we examined whether cell size limits the post-exercise recovery process in fish. Because triploids generally possess larger cells, which could affect many physiological and biochemical processes, we hypothesized that triploids would take longer to recover from exhaustive exercise compared to diploids. To test this, we measured plasma lactate, glucose and osmolality, and white muscle energy stores (glycogen, phosphocreatine and ATP) and lactate before and immediately following exhaustive exercise and during recovery at 2 and 4 h post-exercise. In addition, oxygen consumption and ammonia excretion rates were determined before and after exhaustive exercise. Overall, diploid and triploid brook trout showed similar metabolic responses exercise, but plasma osmolality, white muscle lactate, white muscle ATP and post-exercise oxygen consumption rates recovered earlier in triploids compared to diploids. The results of this study suggest that the characteristic larger cell size of triploidy does not limit the physiological response to, or recovery from, exhaustive exercise.
Quantum phase diagrams of the Jaynes–Cummings Hubbard models in non-rectangular lattices
Zhang, Jun; Jiang, Ying
2017-03-01
In this paper, we investigate systematically the quantum phase transition between the Mott-insulator and superfluid states of the Jaynes–Cummings Hubbard model in triangular, square, honeycomb and kagomé lattices. With the help of Green’s function method, by treating the hopping term in the Jaynes–Cummings Hubbard model as perturbation, we calculate the phase boundaries of Jaynes–Cummings Hubbard models on different geometrical lattices analytically up to second order for both detuning Δ =0 and Δ \
Ferromagnetic Ground States in Face-Centered Cubic Hubbard Clusters
Souza, T. X. R.; Macedo, C. A.
2016-01-01
In this study, the ground state energies of face-centered cubic Hubbard clusters are analyzed using the Lanczos method. Examination of the ground state energy as a function of the number of particle per site n showed an energy minimum for face-centered cubic structures. This energy minimum decreased in n with increasing coulombic interaction parameter U. We found that the ground state energy had a minimum at n = 0.6, when U = 3W, where W denotes the non-interacting energy bandwidth and the face-centered cubic structure was ferromagnetic. These results, when compared with the properties of nickel, shows strong similarity with other finite temperature analyses in the literature and supports the Hirsh’s conjecture that the interatomic direct exchange interaction dominates in driving the system into a ferromagnetic phase. PMID:27583653
Gutzwiller study of extended Hubbard models with fixed boson densities
Energy Technology Data Exchange (ETDEWEB)
Kimura, Takashi [Department of Information Sciences, Kanagawa University, 2946 Tsuchiya, Hiratsuka, Kanagawa 259-1293 (Japan)
2011-12-15
We studied all possible ground states, including supersolid (SS) phases and phase separations of hard-core- and soft-core-extended Bose-Hubbard models with fixed boson densities by using the Gutzwiller variational wave function and the linear programming method. We found that the phase diagram of the soft-core model depends strongly on its transfer integral. Furthermore, for a large transfer integral, we showed that an SS phase can be the ground state even below or at half filling against the phase separation. We also found that the density difference between nearest-neighbor sites, which indicates the density order of the SS phase, depends strongly on the boson density and transfer integral.
Dynamical instability in the S =1 Bose-Hubbard model
Asaoka, Rui; Tsuchiura, Hiroki; Yamashita, Makoto; Toga, Yuta
2016-01-01
We study the dynamical instabilities of superfluid flows in the S =1 Bose-Hubbard model. The time evolution of each spin component in a condensate is calculated based on the dynamical Gutzwiller approximation for a wide range of interactions, from a weakly correlated regime to a strongly correlated regime near the Mott-insulator transition. Owing to the spin-dependent interactions, the superfluid flow of the spin-1 condensate decays at a different critical momentum from a spinless case when the interaction strength is the same. We furthermore calculate the dynamical phase diagram of this model and clarify that the obtained phase boundary has very different features depending on whether the average number of particles per site is even or odd. Finally, we analyze the density and spin modulations that appear in association with the dynamical instability. We find that spin modulations are highly sensitive to the presence of a uniform magnetic field.
The Bose-Hubbard model with squeezed dissipation
Quijandría, Fernando; Naether, Uta; Porras, Diego; José García-Ripoll, Juan; Zueco, David
2015-03-01
The stationary properties of the Bose-Hubbard model under squeezed dissipation are investigated. The dissipative model does not possess a U(1) symmetry but conserves parity. We find that =0 always holds, so no symmetry breaking occurs. Without the onsite repulsion, the linear case is known to be critical. At the critical point the system freezes to an EPR state with infinite two mode entanglement. We show here that the correlations are rapidly destroyed whenever the repulsion is switched on. As we increase the latter, the system approaches a thermal state with an effective temperature defined in terms of the squeezing parameter in the dissipators. We characterize this transition by means of a Gutzwiller ansatz and the Gaussian Hartree-Fock-Bogoliubov approximation.
Charge diffusion in the one-dimensional Hubbard model
Steinigeweg, R.; Jin, F.; De Raedt, H.; Michielsen, K.; Gemmer, J.
2017-08-01
We study the real-time and real-space dynamics of charge in the one-dimensional Hubbard model in the limit of high temperatures. To this end, we prepare pure initial states with sharply peaked density profiles and calculate the time evolution of these nonequilibrium states, by using numerical forward-propagation approaches to chains as long as 20 sites. For a class of typical states, we find excellent agreement with linear-response theory and unveil the existence of remarkably clean charge diffusion in the regime of strong particle-particle interactions. We additionally demonstrate that, in the half-filling sector, this diffusive behavior does not depend on certain details of our initial conditions, i.e., it occurs for five different realizations with random and nonrandom internal degrees of freedom, single and double occupation of the central site, and displacement of spin-up and spin-down particles.
Mott Quantum Criticality in the Anisotropic 2D Hubbard Model
Lenz, Benjamin; Manmana, Salvatore R.; Pruschke, Thomas; Assaad, Fakher F.; Raczkowski, Marcin
2016-02-01
We present evidence for Mott quantum criticality in an anisotropic two-dimensional system of coupled Hubbard chains at half-filling. In this scenario emerging from variational cluster approximation and cluster dynamical mean-field theory, the interchain hopping t⊥ acts as a control parameter driving the second-order critical end point Tc of the metal-insulator transition down to zero at t⊥c/t ≃0.2 . Below t⊥c, the volume of the hole and electron Fermi pockets of a compensated metal vanishes continuously at the Mott transition. Above t⊥c, the volume reduction of the pockets is cut off by a first-order transition. We discuss the relevance of our findings to a putative quantum critical point in layered organic conductors, whose location remains elusive so far.
SENSORY EVALUATION OF HUBBARD JV CHICKENS MEAT AFTER PROPOLIS APPLICATION IN THEIR DIET
National Research Council Canada - National Science Library
Peter Hascík; Jozef Garlík; Ibrahim Omer Elamin Elimam; Vladimíra Knazovická; Juraj Cubon; Miroslav Krocko
2014-01-01
In this experiment, propolis extract was applied in the diet of Hubbard JV broiler chickens and we tested its influence on the sensory quality of breast and thigh muscles prepared by baking at 200...
Pairing in the two-dimensional Hubbard model: An exact diagonalization study
Lin, H. Q.; Hirsch, J. E.; Scalapino, D. J.
1988-05-01
We have studied the pair susceptibilities for all possible pair wave functions that fit on a two-dimensional (2D) eight-site Hubbard cluster by exact diagonalization of the Hamiltonian. Band fillings corresponding to four and six electrons were studied (two or four holes in the half-filled band) for a wide range of Hubbard interaction strengths and temperatures. Our results show that all pairing susceptibilities are suppressed by the Hubbard repulsion. We have also carried out perturbation-theory calculations which show that the leading-order U2 contributions to the d-wave pair susceptibility suppresses d-wave pairing over a significant temperature range. These results are consistent with recent Monte Carlo results and provide further evidence suggesting that the 2D Hubbard model does not exhibit superconductivity.
Fermionic Symmetry-Protected Topological Phase in a Two-Dimensional Hubbard Model
Chen, Cheng-Chien; Muechler, Lukas; Car, Roberto; Neupert, Titus; Maciejko, Joseph
2016-08-01
We study the two-dimensional (2D) Hubbard model using exact diagonalization for spin-1 /2 fermions on the triangular and honeycomb lattices decorated with a single hexagon per site. In certain parameter ranges, the Hubbard model maps to a quantum compass model on those lattices. On the triangular lattice, the compass model exhibits collinear stripe antiferromagnetism, implying d -density wave charge order in the original Hubbard model. On the honeycomb lattice, the compass model has a unique, quantum disordered ground state that transforms nontrivially under lattice reflection. The ground state of the Hubbard model on the decorated honeycomb lattice is thus a 2D fermionic symmetry-protected topological phase. This state—protected by time-reversal and reflection symmetries—cannot be connected adiabatically to a free-fermion topological phase.
MEAT PERFORMANCE OF CHICKENS HUBBARD JV AFTER APPLICATION OF PROPOLIS EXTRACT
Directory of Open Access Journals (Sweden)
Peter Haščík
2013-10-01
Full Text Available Influence of propolis extract on meat performance of chickens’ hybrid combination Hubbard JV was evaluated in this experiment. The feed mixture has been made without addition antibiotic preparation and coccidiostats. However, propolis extract was added to the feed mixtures of experimental groups during the whole fattening period in followed amounts: 150 mg kg-1 (1st experimental group – E1 and 450 mg kg-1 (2nd experimental group – E2. Fattening lasted 42 days. Live body weight increased by 7.63 g in E1 and by 14.13 g in E2 compared with control group (1507.37 g. Carcass body weight was higher in experimental groups (1022.37 g – E1 and 1019.75 g – E2 compared with control group (1005.12 g. The weight of giblets was lower in experimental groups (117.79 g – E1 and 117.16 g – E2 compared with control group (119.06 g. The carcass yield of chickens was higher in E1 (75.27% compared with control group (74.92%, Carcass yield of chickens was higher in E1 (75.27% compared with control group (74.92% but E2 (74.76% was lowest. and there were no significant differences (P ≥ 0.05 among the groups. Propolis extract did not influence the meat performance. Slight increase of live body, resp. of carcass body weight at the end of fattening can have a positive effect on the overall economics of chicken meat production.Based on the results, propolis extract is available supplement for chickens fattening.
Brooks Range and eastern Alps: a tectonic comparison
Energy Technology Data Exchange (ETDEWEB)
Helwig, J.A.
1985-04-01
A comparison of the tectonic evolution of the Brooks Range (BR) and the Eastern Alps (EA) reveals a remarkable parallelism. Both of these Mesozoic-Cenozoic orogenic belts are underlain by sialic crust formed in an earlier Paleozoic orogenic cycle. The old basement is revealed in major tectonic windows: the Tauern Fenster (EA) and the Doonerak Window-Schwatka Mountains (BR) - which are unconformably overlapped by transgressive, neritic marine clastic to carbonate successions - the Permo-Triassic through Hochstegenkalk sequence (EA), and the Kekiktuk-Kayak-Lisburne sequence (BR). These successions are passive-margin sequences that pass southward, in palinspastically restored cross sections, to synchronous deep-water facies deposited on ophiolitic basement - Bunderschiefer on Triassic-Jurassic ophiolites (EA) and Kuna facies or Etivluk sequence on upper Paleozoic ophiolites (BR). Onset of subduction-collision is marked by olistostromal facies - Cretaceous wildflysch (EA) and Jura-Cretaceous Okpikruak Formation (BR) - and the development of major flysch-molasse successions in the foreland basins of the collisional fold and thrust belts. Important major contrasts between these two mountain ranges reside in their colliding blocks and their post-orogenic histories. Alpine orogenesis was driven by continent-continent collision, closing out a young, narrow ocean, whereas Brooks Range deformation appears to have originated by arc-continent collision, closing out an older, broad (.)ocean. Younger Cenozoic deformation is extensional and strike-slip in the Eastern Alps, producing disjunctive basins, but Cenozoic deformation in the Brooks Range is diverse and includes compression in the east and extension in the far west.
Off-site interaction effect in the Extended Hubbard Model with SCRPA method
Harir, S.; Bennai, M.; Boughaleb, Y.
2009-01-01
The Self Consistent Random Phase Approximation (SCRPA) and a Direct Analytical (DA) method are proposed to solve the Extended Hubbard Model in 1D. We have considered an Extended Hubbard Model (EHM) including on-site and off-site interactions for closed chains in one dimension with periodic boundary conditions. The comparison of the SCRPA results with ones obtained by a Direct Analytical approach shows that the SCRPA treats the problem of these closed chains with a rigorous manner. The analysi...
Exact solutions of the high dimensional hard-core Fermi-Hubbard model
Institute of Scientific and Technical Information of China (English)
PAN; Feng
2001-01-01
［1］Hubbard, J., Electron correlations in narrow energy bands, Proc. R. Soc. London, A, 963, 276: 238.［2］Hubbard, J., Electron correlations in narrow energy bands II. The degenerate band case, Proc. R. Soc. London A, 963, A277: 237.［3］Anderson, P. W., The resonating valence bond state in La2CuOand superconductivity, Science, 987, 235: 96.［4］Lieb, E. H, Wu, F. Y., Absence of Mott transition in an exact solution of the short-range one-band model in one dimension, Phys. Rev. Lett., 968, 20: 445.［5］Ogata, M., Shiba, H., Bethe-ansatz wave function, momentum distribution, and spin correlation in the one-dimensional strongly correlated Hubbard model, Phys. Rev., 990, B4: 326.［6］Ogata, M., Sugiyama, T., Shiba, H., Magnetic-field effects on the correlation functions in the one-dimensional strongly correlated Hubbard model, Phys. Rev., 990, B43: 840.［7］Mei, C., Chen, L., Study of the interaction between two electrons in the single band Hubbard model, Z. Phys., 988, B72: 429.［8］Caspers, W. J., Iske, P. L., Exact spectrum for n electrons in the single band Hubbard model, Physica, 989, A, 57: 033.［9］Kirson, M. W., A dynamical supersymmetry in the Hubbard model, Phys. Rev. Lett., 997, 78: 24.［10］Woynarovich, F., Excitations with complex wavefunctions in a Hubbard chain: II. States with several pairs of complex wavenumbers, J. Phys., 982, C5: 97.
Classical behaviour of various variables in an open Bose-Hubbard system
Institute of Scientific and Technical Information of China (English)
Nikola Buri(c)
2011-01-01
Quantum dispersions of various sets of dynamical variables of an open Bose-Hubbard system in a classical limit are studied.To this end,an open system is described in terms of stochastic evolution of its quantum pure states.It is shown that the class of variables that display classical behaviour crucially depends on the type of noise.This is relevant in the mean-field approximation of open Bose-Hubbard dynamics.
Scattering resonances and two-particle bound states of the extended Hubbard model
Energy Technology Data Exchange (ETDEWEB)
Valiente, M; Petrosyan, D [Institute of Electronic Structure and Laser, FORTH, 71110 Heraklion, Crete (Greece)
2009-06-28
We present a complete derivation of two-particle states of the one-dimensional extended Bose-Hubbard model involving attractive or repulsive on-site and nearest-neighbour interactions. We find that this system possesses scattering resonances and two families of energy-dependent interaction-bound states which are not present in the Hubbard model with the on-site interaction alone. (fast track communication)
Histopathology of fish. IV. A granuloma of brook trout
Wood, E.M.; Yasutake, W.T.
1956-01-01
In the summer of 1952, Snieszko and Griffin (1955) diagnosed kidney disease in brook trout from the Fish and Wildlife Service's station at Berlin, New Hampshire. During the examination of these fish, a peculiar lesion was observed in the vicinity of the gastric caeca. In very advanced cases, hard, glistening, white masses of tissue bearing a striking resemblance to mature testes often filled the abdominal cavity. In the initial examinations, the material was actually mistaken for normal testicular tissue. Subsequently, it was recognized as an entirely aberrant, proliferating tumor-like mass.
Quantum simulation of the Hubbard model with dopant atoms in silicon.
Salfi, J; Mol, J A; Rahman, R; Klimeck, G; Simmons, M Y; Hollenberg, L C L; Rogge, S
2016-04-20
In quantum simulation, many-body phenomena are probed in controllable quantum systems. Recently, simulation of Bose-Hubbard Hamiltonians using cold atoms revealed previously hidden local correlations. However, fermionic many-body Hubbard phenomena such as unconventional superconductivity and spin liquids are more difficult to simulate using cold atoms. To date the required single-site measurements and cooling remain problematic, while only ensemble measurements have been achieved. Here we simulate a two-site Hubbard Hamiltonian at low effective temperatures with single-site resolution using subsurface dopants in silicon. We measure quasi-particle tunnelling maps of spin-resolved states with atomic resolution, finding interference processes from which the entanglement entropy and Hubbard interactions are quantified. Entanglement, determined by spin and orbital degrees of freedom, increases with increasing valence bond length. We find separation-tunable Hubbard interaction strengths that are suitable for simulating strongly correlated phenomena in larger arrays of dopants, establishing dopants as a platform for quantum simulation of the Hubbard model.
The Why, What, and Impact of GPA at Oxford Brookes University
Andrews, Matthew
2016-01-01
This paper examines the introduction at Oxford Brookes University of a Grade Point Average (GPA) scheme alongside the traditional honours degree classification. It considers the reasons for the introduction of GPA, the way in which the scheme was implemented, and offers an insight into the impact of GPA at Brookes. Finally, the paper considers…
Direct Probing of the Mott Crossover in the SU(N Fermi-Hubbard Model
Directory of Open Access Journals (Sweden)
Christian Hofrichter
2016-06-01
Full Text Available We report on a detailed experimental investigation of the equation of state (EoS of the three-dimensional Fermi-Hubbard model (FHM in its generalized SU(N-symmetric form, using a degenerate ytterbium gas in an optical lattice. In its more common spin-1/2 form, the FHM is a central model of condensed-matter physics. The generalization to N>2 was first used to describe multi-orbital materials and is expected to exhibit novel many-body phases in a complex phase diagram. By realizing and locally probing the SU(N FHM with ultracold atoms, we obtain model-free access to thermodynamic quantities. The measurement of the EoS and the local compressibility allows us to characterize the crossover from a compressible metal to an incompressible Mott insulator. We reach specific entropies above Néel order but below that of uncorrelated spins. Having access to the EoS of such a system represents an important step towards probing predicted novel SU(N phases.
Dark-polariton bound pairs in the modified Jaynes-Cummings-Hubbard model
Maggitti, A.; Radonjić, M.; Jelenković, B. M.
2016-01-01
We investigate a one-dimensional modified Jaynes-Cummings-Hubbard chain of N identical QED cavities with nearest-neighbor photon tunneling and periodic boundary conditions. Each cavity contains an embedded three-level atom which is coupled to a cavity mode and an external classical control field. In the case of two excitations and common large detuning of two Raman-resonant fields, we show the emergence of two different species of dark-polariton bound pairs (DPBPs) that are mutually localized in their relative spatial coordinates. Due to the high degree of controllability, we show the appearance of either one or two DPBPs, having the energies within the energy gaps between three bands of mutually delocalized eigenstates. Interestingly, in a different parameter regime with negatively detuned Raman fields, we find that the ground state of the system is a DPBP which can be utilized for the photon storage, retrieval, and controllable state preparation. Moreover, we propose an experimental realization of our model system.
Fermionic Hubbard model with Rashba or Dresselhaus spin-orbit coupling
Sun, Fadi; Ye, Jinwu; Liu, Wu-Ming
2017-06-01
In this work, we investigate the possible dramatic effects of Rashba or Dresselhaus spin-orbit coupling (SOC) on the fermionic Hubbard model in a two-dimensional square lattice. In the strong coupling limit, it leads to the rotated antiferromagnetic Heisenberg model which is a new class of quantum spin model. For a special equivalent class, we identify a new spin-orbital entangled commensurate ground (Y-y) state subject to strong quantum fluctuations at T = 0. We evaluate the quantum fluctuations by the spin wave expansion up to order 1/{S}2. In some SOC parameter regimes, the Y-y state supports a massive relativistic incommensurate magnon (C-IC) with its two gap minima positions continuously tuned by the SOC parameters. The C-IC magnons dominate all the low temperature thermodynamic quantities and also lead to the separation of the peak positions between the longitudinal and the transverse spin structure factors. In the weak coupling limit, any weak repulsive interaction also leads to a weak Y-y state. There is only a crossover from the weak to the strong coupling. High temperature expansions of the specific heats in both weak and strong coupling are presented. The dramatic roles to be played by these C-IC magnons at generic SOC parameters or under various external probes are hinted at. Experimental applications to both layered noncentrosymmetric materials and cold atoms are discussed.
Mott transition in a two-leg Bose-Hubbard ladder under an artificial magnetic field
Keleş, Ahmet; Oktel, M. Ö.
2015-01-01
We consider the Bose-Hubbard model on a two-leg ladder under an artificial magnetic field and investigate the superfluid-to-Mott insulator transition in this setting. Recently, this system has been experimentally realized [M. Atala et al., Nature Phys. 10, 588 (2014), 10.1038/nphys2998], albeit in a parameter regime that is far from the Mott transition boundary. Depending on the strength of the magnetic field, the single-particle spectrum has either a single ground state or two degenerate ground states. The transition between these two phases is reflected in the many-particle properties. We first investigate these phases through the Bogoliubov approximation in the superfluid regime and calculate the transition boundary for weak interactions. For stronger interactions the system is expected to form a Mott insulator. We calculate the Mott transition boundary as a function of the magnetic field and interleg coupling with mean-field theory, strong-coupling expansion, and density matrix renormalization group (DMRG). Finally, using the DMRG, we investigate the particle-hole excitation gaps of this system at different filling factors and find peaks at simple fractions, indicating the possibility of correlated phases.
Phase diagram of the half-filled ionic Hubbard model
Bag, Soumen; Garg, Arti; Krishnamurthy, H. R.
2015-06-01
We study the phase diagram of the ionic Hubbard model (IHM) at half filling on a Bethe lattice of infinite connectivity using dynamical mean-field theory (DMFT), with two impurity solvers, namely, iterated perturbation theory (IPT) and continuous time quantum Monte Carlo (CTQMC). The physics of the IHM is governed by the competition between the staggered ionic potential Δ and the on-site Hubbard U . We find that for a finite Δ and at zero temperature, long-range antiferromagnetic (AFM) order sets in beyond a threshold U =UA F via a first-order phase transition. For U smaller than UA F the system is a correlated band insulator. Both methods show a clear evidence for a quantum transition to a half-metal (HM) phase just after the AFM order is turned on, followed by the formation of an AFM insulator on further increasing U . We show that the results obtained within both methods have good qualitative and quantitative consistency in the intermediate-to-strong-coupling regime at zero temperature as well as at finite temperature. On increasing the temperature, the AFM order is lost via a first-order phase transition at a transition temperature TA F(U ,Δ ) [or, equivalently, on decreasing U below UA F(T ,Δ ) ], within both methods, for weak to intermediate values of U /t . In the strongly correlated regime, where the effective low-energy Hamiltonian is the Heisenberg model, IPT is unable to capture the thermal (Neel) transition from the AFM phase to the paramagnetic phase, but the CTQMC does. At a finite temperature T , DMFT +CTQMC shows a second phase transition (not seen within DMFT +IPT ) on increasing U beyond UA F. At UN>UA F , when the Neel temperature TN for the effective Heisenberg model becomes lower than T , the AFM order is lost via a second-order transition. For U ≫Δ , TN˜t2/U (1 -x2) , where x =2 Δ /U and thus TN increases with increase in Δ /U . In the three-dimensional parameter space of (U /t ,T /t ,andΔ /t ) , as T increases, the surface of first
SENSORY EVALUATION OF HUBBARD JV CHICKENS MEAT AFTER PROPOLIS APPLICATION IN THEIR DIET
Directory of Open Access Journals (Sweden)
Peter Haščík
2014-02-01
Full Text Available In this experiment, propolis extract was applied in the diet of Hubbard JV broiler chickens and we tested its influence on the sensory quality of breast and thigh muscles prepared by baking at 200 °C for 60 minutes, followed by final baking for 10-15 minutes. Five groups were created: one control (C and four experimental (I, II, III, IV groups. Each group consisted of 100 chickens. Fattening lasted 42 days. Chickens were fed by ad libitum system. The identical starter feed mixture were administered till the 21st day of age. From the 22nd to 42nd day of age, chickens were fed by growth feed mixture in all groups. Feed mixtures were made without antibiotics and coccidiostats. Propolis extract was added to experimental groups at doses of 150 mg.kg-1 (I, 450 mg.kg-1 (II, 600 mg.kg-1 (III and 800 mg.kg-1 (IV. Breast and thigh muscles of 60 chickens from each group were prepared by baking and were anonymously assessed by six-member committee, which evaluated the smell, taste, juiciness and tenderness of meat in five-point scale. No significant differences (P ≥ 0.05 were found in smell, taste, juiciness and tenderness of breast and thigh muscles between the control and experimental groups. Sensory quality of chicken meat is one of the most important links for its use in food chain. The results of experiment confirmed, that propolis extract in those quantities can be applied in chicken nutrition, because sensory quality of chicken meat has not been worsen after its application.
Antiferromagnetism and d-wave superconductivity in the Hubbard model
Energy Technology Data Exchange (ETDEWEB)
Krahl, H.C.
2007-07-25
The two-dimensional Hubbard model is a promising effective model for the electronic degrees of freedom in the copper-oxide planes of high temperature superconductors. We present a functional renormalization group approach to this model with focus on antiferromagnetism and d-wave superconductivity. In order to make the relevant degrees of freedom more explicitly accessible on all length scales, we introduce composite bosonic fields mediating the interaction between the fermions. Spontaneous symmetry breaking is reflected in a non-vanishing expectation value of a bosonic field. The emergence of a coupling in the d-wave pairing channel triggered by spin wave fluctuations is demonstrated. Furthermore, the highest temperature at which the interaction strength for the electrons diverges in the renormalization flow is calculated for both antiferromagnetism and d-wave superconductivity over a wide range of doping. This ''pseudo-critical'' temperature signals the onset of local ordering. Moreover, the temperature dependence of d-wave superconducting order is studied within a simplified model characterized by a single coupling in the d-wave pairing channel. The phase transition within this model is found to be of the Kosterlitz-Thouless type. (orig.)
Superconductivity from doublon condensation in the ionic Hubbard model
Samanta, Abhisek; Sensarma, Rajdeep
2016-12-01
In the ionic Hubbard model, the on-site repulsion U , which drives a Mott insulator, and the ionic potential V , which drives a band insulator, compete with each other to open up a window of charge fluctuations when U ˜V . We study this model on square and cubic lattices in the limit of large U and V , with V ˜U . Using an effective Hamiltonian and a slave-boson approach with both doublons and holons, we find that the system undergoes a phase transition as a function of V from an antiferromagnetic Mott insulator to a paramagnetic insulator with strong singlet correlations, which is driven by a condensate of "neutral" doublon-holon pairs. On further increasing V , the system undergoes another phase transition to a superconducting phase driven by condensate of "charged" doublons and holons. The superfluid phase, characterized by the presence of a coherent (but gapped) fermionic quasiparticle and h c /e flux quantization, has a high Tc˜t , which shows a dome-shaped behavior as a function of V . The paramagnetic insulator phase has a deconfined U(1) gauge field and associated gapless photon excitations. We also discuss how these phases can be detected in the ultracold-atom context.
Stony Brook's Graduate Courses in Clear, Vivid, Conversational Communication
Bass, E.
2011-12-01
Graduate students in the sciences at Stony Brook University are taking for-credit courses to learn to communicate more effectively about science with people outside their disciplines, including public officials, the press, students, potential funders and employers, colleagues in other fields, and the general public. Five Communicating Science courses are offered; two more will be added in January, 2012. The courses are offered by the School of Journalism and developed by the Center for Communicating Science (CCS). This interdisciplinary center was founded in 2009, with the participation of Alan Alda, the actor, writer, director and longtime advocate for science, who is a Visiting Professor at Stony Brook. At the core of the program are three 1-credit (14-hour) modules that rely on experiential learning, repeated practice and immediate, interactive feedback. In Distilling Your Message, students practice speaking clearly, vividly and conversationally about their work at different levels of complexity and formality to different audiences, using storytelling techniques where appropriate. In Writing for the Public, they extend these skills into writing. In Improvisation for Scientists, the most unconventional of the courses, students play improvisational theater games to help themselves connect more directly, personally and responsively with their audiences. In their first two semesters, the courses are expected to serve about 90 students, taking a total of about 180 credits. Most of the courses have filled quickly, mixing master's and doctoral students from more than a dozen fields, including marine and atmospheric sciences. Three to six credits of Communicating Science courses are required for students in two programs, an MA in Marine Conservation and Policy and an Advanced Certificate in Health Communications. The content and methods of the courses are based largely on lessons learned from evaluations of all-day workshops that CCS has conducted for more than 250
Schubert in Stony Brook and Kinks in Vienna
van Nieuwenhuizen, P.
Wolfgang Kummer became my friend during the many years I have been visiting Vienna in January. He created a marvellous Institute for Theoretical Physics with an enthusiastic group of students, postdocs and colleagues. Great Institutes need a central person to grow around. Two such Institutes I have been attached to are Utrecht where M. Veltman created a school of field theorists, and Stony Brook where C.N. Yang was the natural leader. In Vienna Wolfgang played a similar role. His mere presence during seminars gave a sense of enthusiasm and direction, and his active participation was an example for younger physicists not to be shy and also ask further clarifications when needed. In particular I was impressed by his collaboration with students. Almost every afternoon I would find him sitting with one or two students at his desk or in the conference room, trying to understand new problems in dilaton gravity, and discussing and calculating with them on equal footing. I invited Wolfgang to visit Stony Brook, but he was noncommittal, and I soon found out that he was seriously ill. Yet, he would come in everyday, and be the life of the Institute. Every year with his wife Lore we would go out one evening in Vienna, either to a play or a concert. These were great evenings as I will describe below. Near the end, I would phone him at his home, and we would talk physics. He remained optimistic about his chances, but then suddenly all went wrong and he died. I miss a dear friend. Below is the story of how we became friends…
Emergent lattices with geometrical frustration in doped extended Hubbard models
Kaneko, Ryui; Tocchio, Luca F.; Valentí, Roser; Gros, Claudius
2016-11-01
Spontaneous charge ordering occurring in correlated systems may be considered as a possible route to generate effective lattice structures with unconventional couplings. For this purpose we investigate the phase diagram of doped extended Hubbard models on two lattices: (i) the honeycomb lattice with on-site U and nearest-neighbor V Coulomb interactions at 3 /4 filling (n =3 /2 ) and (ii) the triangular lattice with on-site U , nearest-neighbor V , and next-nearest-neighbor V' Coulomb interactions at 3 /8 filling (n =3 /4 ). We consider various approaches including mean-field approximations, perturbation theory, and variational Monte Carlo. For the honeycomb case (i), charge order induces an effective triangular lattice at large values of U /t and V /t , where t is the nearest-neighbor hopping integral. The nearest-neighbor spin exchange interactions on this effective triangular lattice are antiferromagnetic in most of the phase diagram, while they become ferromagnetic when U is much larger than V . At U /t ˜(V/t ) 3 , ferromagnetic and antiferromagnetic exchange interactions nearly cancel out, leading to a system with four-spin ring-exchange interactions. On the other hand, for the triangular case (ii) at large U and finite V', we find no charge order for small V , an effective kagome lattice for intermediate V , and one-dimensional charge order for large V . These results indicate that Coulomb interactions induce [case (i)] or enhance [case(ii)] emergent geometrical frustration of the spin degrees of freedom in the system, by forming charge order.
Staggered Flux State in Two-Dimensional Hubbard Models
Yokoyama, Hisatoshi; Tamura, Shun; Ogata, Masao
2016-12-01
The stability and other properties of a staggered flux (SF) state or a correlated d-density wave state are studied for the Hubbard (t-t'-U) model on extended square lattices, as a low-lying state that competes with the dx2 - y2-wave superconductivity (d-SC) and possibly causes the pseudogap phenomena in underdoped high-Tc cuprates and organic κ-BEDT-TTF salts. In calculations, a variational Monte Carlo method is used. In the trial wave function, a configuration-dependent phase factor, which is vital to treat a current-carrying state for a large U/t, is introduced in addition to ordinary correlation factors. Varying U/t, t'/t, and the doping rate (δ) systematically, we show that the SF state becomes more stable than the normal state (projected Fermi sea) for a strongly correlated (U/t ≳ 5) and underdoped (δ ≲ 0.16) area. The decrease in energy is sizable, particularly in the area where Mott physics prevails and the circular current (order parameter) is strongly suppressed. These features are consistent with those for the t-J model. The effect of the frustration t'/t plays a crucial role in preserving charge homogeneity and appropriately describing the behavior of hole- and electron-doped cuprates and κ-BEDT-TTF salts. We argue that the SF state does not coexist with d-SC and is not a "normal state" from which d-SC arises. We also show that a spin current (flux or nematic) state is never stabilized in the same regime.
Attractive Hubbard model with disorder and the generalized Anderson theorem
Energy Technology Data Exchange (ETDEWEB)
Kuchinskii, E. Z., E-mail: kuchinsk@iep.uran.ru; Kuleeva, N. A., E-mail: strigina@iep.uran.ru; Sadovskii, M. V., E-mail: sadovski@iep.uran.ru [Russian Academy of Sciences, Institute for Electrophysics, Ural Branch (Russian Federation)
2015-06-15
Using the generalized DMFT+Σ approach, we study the influence of disorder on single-particle properties of the normal phase and the superconducting transition temperature in the attractive Hubbard model. A wide range of attractive potentials U is studied, from the weak coupling region, where both the instability of the normal phase and superconductivity are well described by the BCS model, to the strong-coupling region, where the superconducting transition is due to Bose-Einstein condensation (BEC) of compact Cooper pairs, formed at temperatures much higher than the superconducting transition temperature. We study two typical models of the conduction band with semi-elliptic and flat densities of states, respectively appropriate for three-dimensional and two-dimensional systems. For the semi-elliptic density of states, the disorder influence on all single-particle properties (e.g., density of states) is universal for an arbitrary strength of electronic correlations and disorder and is due to only the general disorder widening of the conduction band. In the case of a flat density of states, universality is absent in the general case, but still the disorder influence is mainly due to band widening, and the universal behavior is restored for large enough disorder. Using the combination of DMFT+Σ and Nozieres-Schmitt-Rink approximations, we study the disorder influence on the superconducting transition temperature T{sub c} for a range of characteristic values of U and disorder, including the BCS-BEC crossover region and the limit of strong-coupling. Disorder can either suppress T{sub c} (in the weak-coupling region) or significantly increase T{sub c} (in the strong-coupling region). However, in all cases, the generalized Anderson theorem is valid and all changes of the superconducting critical temperature are essentially due to only the general disorder widening of the conduction band.
Energy of ground state in B-B'-U-Hubbard model in approximation of static fluctuations
Mironov, G I
2002-01-01
To explain some features of CuO sub 2 base high-temperature superconductors (HTSC) one should take account of possibility of electron transfer to the crystalline structure mode next to the nearest one. It terms of approximation of static fluctuations one calculated the energy of ground state in two-dimensional B-B'-U Hubbard model. Lattice is assumed to consist of two sublattices formed by various type atoms. The calculation results of ground state energy are compared with the precise solution for one-dimensional Hubbard model derived previously. Comparison of the precise and the approximated solutions shows that approximation of static fluctuations describes adequately behavior of the Hubbard studied model within both weak and strong correlation ranges
One-electron singular spectral features of the 1D Hubbard model at finite magnetic field
Carmelo, J. M. P.; Čadež, T.
2017-01-01
The momentum, electronic density, spin density, and interaction dependences of the exponents that control the (k , ω)-plane singular features of the σ = ↑ , ↓ one-electron spectral functions of the 1D Hubbard model at finite magnetic field are studied. The usual half-filling concepts of one-electron lower Hubbard band and upper Hubbard band are defined in terms of the rotated electrons associated with the model Bethe-ansatz solution for all electronic density and spin density values and the whole finite repulsion range. Such rotated electrons are the link of the non-perturbative relation between the electrons and the pseudofermions. Our results further clarify the microscopic processes through which the pseudofermion dynamical theory accounts for the one-electron matrix elements between the ground state and excited energy eigenstates.
Hund's coupling and the metal-insulator transition in the two-band Hubbard model
Pruschke, Th.; Bulla, R.
2005-03-01
The Mott-Hubbard metal-insulator transition is investigated in a two-band Hubbard model within dynamical mean-field theory. To this end, we use a suitable extension of Wilson’s numerical renormalization group for the solution of the effective two-band single-impurity Anderson model. This method is non-perturbative and, in particular, allows to take into account the full exchange part of the Hund’s rule coupling between the two orbitals. We discuss in detail the influence of the various Coulomb interactions on thermodynamic and dynamic properties, for both the impurity and the lattice model. The exchange part of the Hund’s rule coupling turns out to play an important role for the physics of the two-band Hubbard model and for the nature of the Mott-transition.
Kato, Shinya; Inaba, Kensuke; Sugawa, Seiji; Shibata, Kosuke; Yamamoto, Ryuta; Yamashita, Makoto; Takahashi, Yoshiro
2016-04-01
A system of ultracold atoms in an optical lattice has been regarded as an ideal quantum simulator for a Hubbard model with extremely high controllability of the system parameters. While making use of the controllability, a comprehensive measurement across the weakly to strongly interacting regimes in the Hubbard model to discuss the quantum many-body state is still limited. Here we observe a great change in the excitation energy spectra across the two regimes in an atomic Bose-Hubbard system by using a spectroscopic technique, which can resolve the site occupancy in the lattice. By quantitatively comparing the observed spectra and numerical simulations based on sum rule relations and a binary fluid treatment under a finite temperature Gutzwiller approximation, we show that the spectra reflect the coexistence of a delocalized superfluid state and a localized insulating state across the two regimes.
Observation of spatial charge and spin correlations in the 2D Fermi-Hubbard model.
Cheuk, Lawrence W; Nichols, Matthew A; Lawrence, Katherine R; Okan, Melih; Zhang, Hao; Khatami, Ehsan; Trivedi, Nandini; Paiva, Thereza; Rigol, Marcos; Zwierlein, Martin W
2016-09-16
Strong electron correlations lie at the origin of high-temperature superconductivity. Its essence is believed to be captured by the Fermi-Hubbard model of repulsively interacting fermions on a lattice. Here we report on the site-resolved observation of charge and spin correlations in the two-dimensional (2D) Fermi-Hubbard model realized with ultracold atoms. Antiferromagnetic spin correlations are maximal at half-filling and weaken monotonically upon doping. At large doping, nearest-neighbor correlations between singly charged sites are negative, revealing the formation of a correlation hole, the suppressed probability of finding two fermions near each other. As the doping is reduced, the correlations become positive, signaling strong bunching of doublons and holes, in agreement with numerical calculations. The dynamics of the doublon-hole correlations should play an important role for transport in the Fermi-Hubbard model.
Tudorache, C; O'Keefe, R A; Benfey, T J
2010-02-01
The effect of flume length and impingement time on post-exercise lactate concentrations in brook charr Salvelinus fontinalis were examined. Swimming in longer flumes increased lactate concentrations, as does impingement after swimming in short flumes.
75 FR 38716 - Safety Zone; Vietnam Veterans of America Fireworks Display, Brookings, OR
2010-07-06
...-9319, e-mail D13-SG-SecPortlandWWM@uscg.mil . If you have questions on viewing the docket, call Renee V... America are holding a fireworks display near Brookings, Oregon on July 4, 2010. Due to the...
Environmental contaminants in fish from Mere Brook - U.S. Naval Air Station, Brunswick, Maine
US Fish and Wildlife Service, Department of the Interior — Mere Brook bisects three former landfills at the U.S. Naval Air Station in Brunswick, Maine (NASB). Leachate, soil, and sediment analyzed during Superfund remedial...
Olemuse teater. Kantor ja Brook / Jan Kott ; tõlk. Eva-Liisa Linder
Kott, Jan
2004-01-01
T. Kantori lavastustest "Surnud klass" ja "Wielopole Wielopole" ning P. Brooki "Carmeni" lavastusest. Tõlgitud raamatust : Jan Kott. The Theatre of Essence: Kantor and Brook.- The Theatre of Essence and other Essays. Evanston, Northwestern University Press, 1984, lk. 159-165
Olemuse teater. Kantor ja Brook / Jan Kott ; tõlk. Eva-Liisa Linder
Kott, Jan
2004-01-01
T. Kantori lavastustest "Surnud klass" ja "Wielopole Wielopole" ning P. Brooki "Carmeni" lavastusest. Tõlgitud raamatust : Jan Kott. The Theatre of Essence: Kantor and Brook.- The Theatre of Essence and other Essays. Evanston, Northwestern University Press, 1984, lk. 159-165
Vermont Center for Geographic Information — The Foote Brook, located in Johnson, Vermont, is known to biologists and anglers as a high quality stream with significant natural reproduction of rainbow, brown,...
Vermont Center for Geographic Information — The Foote Brook, located in Johnson, Vermont, is known to biologists and anglers as a high quality stream with significant natural reproduction of rainbow, brown,...
CRED 5 m Gridded bathymetry of Brooks Banks, Hawaii, USA (Arc ASCII format)
National Oceanic and Atmospheric Administration, Department of Commerce — Gridded bathymetry (5m) of the shelf and slope environments of Brooks Banks, Hawaii, USA. The ASCII includes multibeam bathymetry from the Simrad EM300, Simrad...
Coideal Quantum Affine Algebra and Boundary Scattering of the Deformed Hubbard Chain
de Leeuw, Marius; Regelskis, Vidas
2011-01-01
We consider boundary scattering for a semi-infinite one-dimensional deformed Hubbard chain with boundary conditions of the same type as for the Y=0 giant graviton in the AdS/CFT correspondence. We show that the recently constructed quantum affine algebra of the deformed Hubbard chain has a coideal subalgebra which is consistent with the reflection (boundary Yang-Baxter) equation. We derive the corresponding reflection matrix and furthermore show that the aforementioned algebra in the rational limit specializes to the (generalized) twisted Yangian of the Y = 0 giant graviton.
Numerical Study of Luttinger Liquid Regime of Two-Leg Hubbard Ladders
Institute of Scientific and Technical Information of China (English)
CHENG Kuan; LIU Yu-Liang
2005-01-01
@@ We investigate two-leg Hubbard ladders in the Luttinger liquid regime by the density-matrix renormalization group method. Applicability of the bond concept in this region is discussed in a quantitative comparison of power-law decay exponents, energy components and anti-bond occupations between ladders and chains. The interaction between bond and anti-bond bands induced by finite Hubbard repulsion U is emphasized by our numerical results. Our quantitative results are useful for the justification of the validity of various analytical approaches.
Interplay between electron-phonon interaction and Hubbard repulsion: Bipolaron formation
Energy Technology Data Exchange (ETDEWEB)
Nath, S.; Mondal, N. S.; Ghosh, N. K., E-mail: nanda.ku@rediffmail.com [Department of Physics, University of Kalyani, Kalyani-741235, West Bengal (India)
2015-06-24
In the weak coupling limit, the 2D Hubbard model extended by on-site (local) and inter-site (long range) electron-phonon (EP) interaction has been investigated within Lanczos method of exact diagonalization (ED). On-site (S0) bipolaron formation has been favored by on-site EP interaction induced effective attraction between electrons. But, inter-site phonon mediated interaction between electrons helps to form both S0 and neighboring site (S1) bipolaron. It is further observed that both types of bipolaron formation are suppressed by on-site Hubbard repulsion.
2008-02-01
Both versions of Brooks FDTD are parallelized for Beowulf clusters and have run on more than one hundred processors. In addition to code, a number of...rewritten in C. Both versions of Brooks FDTD are parallelized for Beowulf clusters and have run on more than one hundred processors. In addition to...have made significant contributions include: Aldon Lyssy, who volunteered to scavenge and build the first Beowulf : Peter Gajsek who lead the first
Schill, Daniel J.; Meyer, Kevin A.; Hansen, Michael J.
2017-01-01
Eradication of nonnative Brook Trout Salvelinus fontinalis populations is difficult to achieve with standard techniques, such as electrofishing removal or piscicides; new approaches are needed. A novel concept is to stock “supermale” hatchery fish with wild conspecifics. Supermales (MYY) have two Y-chromosomes, resulting in offspring that are all males; over time, successful supermale reproduction could eradicate the wild population. We constructed an age-structured stochastic model to investigate the effects of manually suppressing wild fish and stocking MYY fingerlings on the long-term viability of hypothetical nonnative Brook Trout populations. In streams, an annual stocking rate of supermales equivalent to 50% of wild age-0 Brook Trout density combined with an annual selective suppression rate equivalent to 50% of wild Brook Trout density resulted in a time to extirpation of only 2–4 years if supermale fitness was equivalent to wild male fitness. However, time to extirpation in streams was 5–15 years if supermale fitness was 80% lower than wild male fitness. In alpine lakes, higher supermale stocking rates and nonselective gillnetting were required to eradicate Brook Trout populations. If supermales were assumed to be as fit as wild males, however, any supermale stocking rate greater than 49% in alpine lakes or 60% in streams achieved eradication in 10 years or less, regardless of the suppression rate. Because manual suppression and the stocking of MYY fingerlings can readily be conducted at the levels assumed in our simulations, use of such an integrated pest management (IPM) approach could extirpate undesirable Brook Trout populations within reasonably short periods of time. Given the recent successful development of an MYY Brook Trout broodstock capable of producing large numbers of MYY fingerlings and given the positive results of the present simulations for both streams and alpine lakes, field testing of MYY stocking is warranted within an
Landscape models of brook trout abundance and distribution in lotic habitat with field validation
McKenna, James E.; Johnson, James H.
2011-01-01
Brook trout Salvelinus fontinalis are native fish in decline owing to environmental changes. Predictions of their potential distribution and a better understanding of their relationship to habitat conditions would enhance the management and conservation of this valuable species. We used over 7,800 brook trout observations throughout New York State and georeferenced, multiscale landscape condition data to develop four regionally specific artificial neural network models to predict brook trout abundance in rivers and streams. Land cover data provided a general signature of human activity, but other habitat variables were resistant to anthropogenic changes (i.e., changing on a geological time scale). The resulting models predict the potential for any stream to support brook trout. The models were validated by holding 20% of the data out as a test set and by comparison with additional field collections from a variety of habitat types. The models performed well, explaining more than 90% of data variability. Errors were often associated with small spatial displacements of predicted values. When compared with the additional field collections (39 sites), 92% of the predictions were off by only a single class from the field-observed abundances. Among “least-disturbed” field collection sites, all predictions were correct or off by a single abundance class, except for one where brown trout Salmo trutta were present. Other degrading factors were evident at most sites where brook trout were absent or less abundant than predicted. The most important habitat variables included landscape slope, stream and drainage network sizes, water temperature, and extent of forest cover. Predicted brook trout abundances were applied to all New York streams, providing a synoptic map of the distribution of brook trout habitat potential. These fish models set benchmarks of best potential for streams to support brook trout under broad-scale human influences and can assist with planning and
Charles Lewis Brook: third Director of the BAA Variable Star Section
Shears, Jeremy
2011-01-01
Charles Lewis Brook, MA, FRAS, FRMetS (1855 - 1939) served as Director of the BAA Variable Star Section from 1910 to 1921. During this time he was not merely interested in collecting the observations of the members (to which he also contributed), but he also spent considerable amounts of time analysing the data and preparing numerous publications on the findings. This paper discusses Brook's life and work, with a particular focus on his contribution to variable star astronomy.
Dynamics of fermionic Hubbard models after interaction quenches in one and two dimensions
Energy Technology Data Exchange (ETDEWEB)
Hamerla, Simone Anke
2013-10-15
In the last years the impressive progress on the experimental side led to a variety of new experiments allowing to address systems out of equilibrium. In this way the behavior of such systems far from equilibrium is no longer a purely theoretical issue but indeed observable. New experimental techniques, like particles trapped in optical lattices, render a realization of quantum systems with nearly arbitrary system parameters possible and provide a possibility to study their time evolution. Systems out of equilibrium are characterized by the fact, that these systems are in highly excited states giving rise to totally new fascinating properties. In the present thesis one- and two-dimensional fermionic Hubbard models out of equilibrium are discussed. The system is taken out of equilibrium by a so-called interaction quench. At the beginning the system is prepared in the groundstate of the non-interacting Hamiltonian. At a time t the interaction between the fermions is suddenly turned on so that the time evolution is governed by the whole, interacting Hamiltonian. Hence the system is prepared in the groundstate of one Hamiltonian but evolves according to a different Hamiltonian. Consequently the system ends up in a highly excited state. To describe such a system a method based on an expansion of the Heisenberg equations of motion to highest order possible is developed in this thesis. This method provides an exact description of the time evolution on short and intermediate time scales after the quench. As the method reveal exact results and does not rely on any perturbative assumption, a study of arbitrarily large interaction strengths is possible. Besides, the method is one of the few methods capable of two-dimensional systems. In the following the method used in this thesis is explained and advantages and disadvantages of the approach are thematized. For this purpose the results of the developed iterated equation of motion approach are compared to results obtained in
Movement patterns of Brook Trout in a restored coastal stream system in southern Massachusetts
Snook, Erin L.; Letcher, Benjamin H.; Dubreuil, Todd L.; Zydlewski, Joseph; O'Donnell, Matthew J.; Whiteley, Andrew R.; Hurley, Stephen T.; Danylchuk, Andy J.
2016-01-01
Coastal Brook Trout (Salvelinus fontinalis) populations are found from northern Canada to New England. The extent of anadromy generally decreases with latitude, but the ecology and movements of more southern populations are poorly understood. We conducted a 33-month acoustic telemetry study of Brook Trout in Red Brook, MA, and adjacent Buttermilk Bay (marine system) using 16 fixed acoustic receivers and surgically implanting acoustic transmitters in 84 individuals. Tagged Brook Trout used the stream, estuary (50% of individuals) and bay (10% of individuals). Movements into full sea water were brief when occurring. GAMM models revealed that transitions between habitat areas occurred most often in spring and fall. Environmental data suggest that use of the saline environment is limited by summer temperatures in the bay. Movements may also be related to moon phase. Compared to more northern coastal populations of Brook Trout, the Red Brook population appears to be less anadromous overall, yet the estuarine segment of the system may have considerable ecological importance as a food resource.
Yanagisawa, Takashi
2016-11-01
The ground state of the two-dimensional (2D) Hubbard model is investigated by adopting improved wave functions that take into account intersite electron correlation beyond the Gutzwiller ansatz. The ground-state energy is lowered considerably, giving the best estimate of the ground-state energy for the 2D Hubbard model. There is a crossover from weakly to strongly correlated regions as the on-site Coulomb interaction U increases. The antiferromagnetic correlation induced by U is reduced for hole doping when U is large, being greater than the bandwidth, thus increasing the kinetic energy gain. The spin and charge fluctuations are induced in the strongly correlated region. These antiferromagnetic and kinetic charge fluctuations induce electron pairings, which results in high-temperature superconductivity.
Nutrient Storage and Release Following Perturbation of an Experimental Forest Ecosystem
Havig, J. R.; Keller, C. K.
2001-12-01
Chemical weathering and chemical denudation are being studied in a "sandbox" red pine ecosystem at the Hubbard Brook Experimental Forest. The sandbox is a 7.5 m x 7.5 m x 1.5 m granitic sand-filled lysimeter with suction porewater samplers installed at 15 cm, 35 cm, and 95 cm depths, and a tipping-bucket drainage collector at the bottom. In May of 1998, photosynthetic input to the subsurface was halted by removal of the above-ground portions of the 15-year-old trees. The purpose of this perturbation was to study subsurface hydrology and decomposition in the absence of physical disturbance, and their effects on nutrient loss from the system. Elimination of transpiration has increased water and nutrient export while drainage concentrations have remained the same if not increased. The greatest concentration increases for all ions occur at the 15 cm porewater depth. Potassium and chloride both show large increases shortly after the tree cut, and calcium, magnesium and nitrate all show large increases the second growing season after the tree cut. Sodium and fluoride concentrations have shown little change in response to the cut. For all ions, concentrations are markedly independent of discharge and porewater residence time, i.e. there is little evidence of kinetic water-mineral reactions. Nutrient mass balances and nutrient ratios in drainage indicate that most of the nutrients released are from the litter layer. Results of this study suggest that a combination of soil-chemical and decomposition mechanisms along subsurface flow pathways can attenuate nutrient loss from perturbed sites, whereas surface runoff pathways may amplify nutrient loss.
Learning to Communicate Science: Stony Brook University's Approach
Bass, E.
2012-12-01
Stony Brook University offers an unusual series of short courses to help science graduate students learn to communicate more effectively about science with people outside their disciplines, including the public, public officials, potential funders and employers, students, the press, and colleagues in other fields. The courses include six 1-credit (14-hour) modules in oral and written communication that rely on practice and interactive feedback. More than 120 master's and PhD students, from more than 16 departments, have taken at least one of the courses since spring 2011. Most students who try one module end up taking two or three. An additional course for medical and nursing students was added in fall 2012. The courses are offered in the School of Journalism and were developed by the Center for Communicating Science (CCS). CCS was founded in 2009, with the participation of Alan Alda, the actor, writer, and longtime advocate for science, who is a Visiting Professor at Stony Brook. The Communicating Science courses have received strong institutional support and enthusiastic reviews. They are required by two programs, an MA in Marine Conservation and Policy and an Advanced Certificate in Health Communications. Two successive Provosts have subsidized course costs for PhD students, and Graduate School leaders are working to establish a steady funding stream to allow expansion of the program. Our aspiration at CCS is for every science graduate student to receive some training in communicating about science to the public. Several factors have helped in establishing the program: --CCS' multidisciplinary nature helped build support, with participation by faculty from across the campus, including not only the natural sciences, engineering, and medicine, but journalism, theatre arts, and the Writing Program, as well as nearby Brookhaven National Laboratory and Cold Spring Harbor Laboratory. --Before offering courses, CCS conducted all-day workshops and high
Enterococcus rivorum sp. nov., from water of pristine brooks.
Niemi, R Maarit; Ollinkangas, Tuula; Paulin, Lars; Svec, Pavel; Vandamme, Peter; Karkman, Antti; Kosina, Marcel; Lindström, Kristina
2012-09-01
A significant number of Enterococcus strains from pristine waters of two brooks in Finland formed a distinct cluster on the basis of whole-cell protein fingerprinting by one-dimensional SDS-PAGE. The strains shared the following characteristics. Cells were ovoid, Gram-positive-staining and non-spore-forming, appearing singly or in pairs or chains. They were facultatively anaerobic and catalase-negative. Growth in broth containing 6.5 % NaCl or at 45 °C was weak or absent. Production of D antigen was variable. The strains tolerated 60 °C for 30 min, 40 % bile and tellurite, hydrolysed aesculin strongly and gelatin weakly, produced no acid from hippurate and did not reduce it, grew weakly at 10 °C, showed a strong reaction for the Voges-Proskauer test and produced acid from methyl α-d-glucoside, mannitol, sorbitol and sucrose, with weak or no production of acid from methyl α-d-mannoside, l-arabinose, gluconate and l-xylose. Several of the strains were selected for identification on the basis of sequencing of almost the whole 16S rRNA gene and partial atpA and pheS genes and of (GTG)(5)-PCR fingerprints. Partial atpA and pheS gene sequencing was also performed for those type strains of Enterococcus species without available sequences in the database. The pristine brook isolates formed a novel species, for which the name Enterococcus rivorum sp. nov. (type strain S299(T) = HAMBI 3055(T) = LMG 25899(T) = CCM 7986(T)) is proposed. On the basis of 16S rRNA gene sequence similarity, E. rivorum sp. nov. is related to the Enterococcus faecalis genogoup. It is distinguished from described Enterococcus species on the basis of 16S rRNA, atpA and pheS gene sequences and whole-cell protein and (GTG)(5)-PCR fingerprints. It is most closely related to E. faecalis, but DNA-DNA hybridization confirms it to represent a novel species.
Energy Technology Data Exchange (ETDEWEB)
Afchain, St
2005-02-15
The Hubbard model is the simplest model to describe the behaviour of fermions on a network, it takes into account only fermion scattering and only interactions with other fermions located on the same site. Half-filling means that the total number of fermions is equal to half the number of sites. In the first chapter we show how we can pass trough successive approximations from a very general Hamiltonian to the Hubbard Hamiltonian. The second chapter is dedicated to the passage from the Hamiltonian formalism to the Grassmanian functional formalism. The main idea is to show that the correlation functions of the Hamiltonian approach can be described through fermionic functional integrals which implies the possibility of speaking of the model in terms of field theory. The chapter 3 deals with the main constructive techniques that allow the strict and consistent construction of models inside the frame of field theory. We show by proving the violation of a condition concerning self-energy, that the two-dimensional Hubbard model at half-filling has not the behaviour of a Fermi liquid in the Landau's interpretation. (A.C.)
Energy Technology Data Exchange (ETDEWEB)
1986-09-30
Fields Brook is located in the City of Ashtabula, Ohio and drains a 5.6-square mile watershed (defined as the 'site'). The 3.5 mile main channel of Fields Brook flows through an industrial area that is one of the largest and most diversified concentrations of chemical plants in Ohio. Industrial sources have contaminated the sediment in Fields Brook with a variety of organic and heavy metal pollutants, including TCE, PCE, chlorobenzene, vinyl chloride, arsenic, zinc, mercury and chromium. Base-neutral compounds including hexachloroethane, toluenediamine and toluene diisocyanate also were detected in Fields Brook sediments. Sediments taken from the Ashtabula River in the vicinity of Fields Brook are contaminated with PCBs. The U.S. EPA believes that the amount of contamination entering the brook at this time has been substantially reduced due to the recent development of pollution control laws and discharge-permitting requirements.
The role of local repulsion in superconductivity in the Hubbard-Holstein model
Lin, Chungwei; Wang, Bingnan; Teo, Koon Hoo
2017-01-01
We examine the superconducting solution in the Hubbard-Holstein model using Dynamical Mean Field Theory. The Holstein term introduces the site-independent Boson fields coupling to local electron density, and has two competing influences on superconductivity: The Boson field mediates the effective electron-electron attraction, which is essential for the S-wave electron pairing; the same coupling to the Boson fields also induces the polaron effect, which makes the system less metallic and thus suppresses superconductivity. The Hubbard term introduces an energy penalty U when two electrons occupy the same site, which is expected to suppress superconductivity. By solving the Hubbard-Holstein model using Dynamical Mean Field theory, we find that the Hubbard U can be beneficial to superconductivity under some circumstances. In particular, we demonstrate that when the Boson energy Ω is small, a weak local repulsion actually stabilizesthe S-wave superconducting state. This behavior can be understood as an interplay between superconductivity, the polaron effect, and the on-site repulsion: As the polaron effect is strong and suppresses superconductivity in the small Ω regime, the weak on-site repulsion reduces the polaron effect and effectively enhances superconductivity. Our calculation elucidates the role of local repulsion in the conventional S-wave superconductors.
Wijk, van A.J.P.
1980-01-01
The simultaneous selection for yield of herbage and seed in Setaria sphacelata (Schumach.) Stapf and Hubbard ex Moss was studied, and the amount of variation present for each of these traits in relation to various plant characteristics was assessed in a spaced plant population and its open-pollinate
POLARONS IN THE 3-BAND PEIERLS-HUBBARD MODEL - AN EXACT DIAGONALIZATION STUDY
DOBRY, A; GRECO, A; LORENZANA, J; RIERA, J
1994-01-01
We have studied the three-band Peierls-Hubbard model describing the Cu-O layers in high-T(c) superconductors by using Lanczos diagonalization and assuming infinite mass for the ions. When the system is doped with one hole, and for lambda (the electron-lattice coupling strength) greater than a critic
Phase Transitions in the Hubbard Model for a Half Filled Band
Jonkman, Harry Th.; Kommandeur, Jan
1982-01-01
The phase-transitions for a half-filled band can be numerically calculated from the Hubbard Hamiltonian with an exponential inter-site dependence of the transfer integral. Even for four sites with four electrons the results compare very well with experiments on spin susceptibilities and the intensit
The simplified Hubbard model in one and two dimensions. Thermodynamic and dynamic properties
Vries, Pedro de; Michielsen, Kristel; Raedt, Hans De
1993-01-01
Thermodynamic and dynamic properties of the one and two-dimensional simplified Hubbard model are studied. At zero temperature and half filling, no metal-insulator transition occurs for nonzero coupling U and the system is an antiferromagnetic insulator. The behavior of the gap in the single-particle
THE SIMPLIFIED HUBBARD-MODEL IN ONE AND 2 DIMENSIONS - THERMODYNAMIC AND DYNAMIC PROPERTIES
DEVRIES, P; MICHIELSEN, K; DERAEDT, H
1993-01-01
Thermodynamic and dynamic properties of the one and two-dimensional simplified Hubbard model are studied. At zero temperature and half filling, no metal-insulator transition occurs for nonzero coupling U and the system is an antiferromagnetic insulator. The behavior of the gap in the single-particle
Mott metal-insulator transition in the doped Hubbard-Holstein model
Kurdestany, Jamshid Moradi; Satpathy, S.
2017-08-01
Motivated by the current interest in the understanding of the Mott insulators away from half-filling, observed in many perovskite oxides, we study the Mott metal-insulator transition in the doped Hubbard-Holstein model using the Hartree-Fock mean field theory. The Hubbard-Holstein model is the simplest model containing both the Coulomb and the electron-lattice interactions, which are important ingredients in the physics of the perovskite oxides. In contrast to the half-filled Hubbard model, which always results in a single phase (either metallic or insulating), our results show that away from half-filling, a mixed phase of metallic and insulating regions occurs. As the dopant concentration is increased, the metallic part progressively grows in volume, until it exceeds the percolation threshold, leading to percolative conduction. This happens above a critical dopant concentration δc, which, depending on the strength of the electron-lattice interaction, can be a significant fraction of unity. This means that the material could be insulating even for a substantial amount of doping, in contrast to the expectation that doped holes would destroy the insulating behavior of the half-filled Hubbard model. While effects of fluctuation beyond the mean field remain an open question, our results provide a starting point for the understanding of the density-driven metal-insulator transition observed in many complex oxides.
Superconducting, magnetic, and charge correlations in the doped two-chain Hubbard model
Asai, Y
1995-01-01
Superconducting, magnetic, and charge correlation functions and dynamic spin correlation functions of the doped two-chain Hubbard model is studied with the projector Quantum Monte carlo method and Lanczos recursion method. Of the three correlation functions, the interchain singlet superconducting correlation function is the most long range. Our data is not consistent with the Luther-Emery picture.
SINGLE-PARTICLE SELF-ENERGY AND OPTICAL CONDUCTIVITY OF THE SIMPLIFIED HUBBARD-MODEL
de Vries, Pedro; Michielsen, Kristel; Raedt, Hans De
1994-01-01
It is shown that the single-particle self-energy of the one and two-dimensional simplified Hubbard model exhibits different behavior characterized by Fermi-liquid, non-Fermi-liquid quasiparticle, or non-quasiparticle excitations, as a function of the strength of the on-site Coulomb repulsion U, temp
New phases in an extended Hubbard model explicitly including atomic polarizabilities
Brink, van de J.; Meinders, M.B.J.; Lorenzana, J.; Eder, R.; Sawatzky, G.A.
1996-01-01
We consider the influence of a nearest-neighbor Coulomb interaction in an extended Hubbard model and introduce a new interaction term which simulates atomic polarizabilities. This has the effect of screening the on-site Coulomb interaction for charged excitations, unlike a neighbor Coulomb interacti
Gutzwiller variational wave function for multiorbital Hubbard models in finite dimensions
Münster, Kevin zu; Bünemann, Jörg
2016-07-01
We develop a diagrammatic method for the evaluation of general multiband Gutzwiller wave functions in finite dimensions. Our approach provides a systematic improvement of the widely used Gutzwiller approximation. As a first application, we investigate itinerant ferromagnetism and correlation-induced deformations of the Fermi surface for a two-band Hubbard model on a square lattice.
Catapodium marinum (L.) Hubbard, Scirpus planifolius Grimm en Trifolium micranthum Viv. op Goeree
Westhoff, V.; Leeuwen, van C.G.
1962-01-01
The mediterranean-atlantic species Catapodium marinum (L.) Hubbard reaches its northern limit on the continent in the Netherlands. Up to 1959 only 2 localities on the Dutch coast were known. In 1961 the species was discovered in large quantities on the brackish estuary shore of the island of Goeree,
Separable interactions and liquid 3He : V. Phase diagram in the presence of a Hubbard interaction
Capel, H.W.; Nijhoff, F.W.; Breems, A. den
1986-01-01
A comparison is made between the various extrema of the Landau expansion of liquid 3He derived in a previous paper. As an application the phase diagram is investigated in the presence of an external magnetic field assuming that the Hubbard interaction is small as compared to the pairing interaction
Mott-Hubbard and Anderson transitions in dynamical mean-field theory
Energy Technology Data Exchange (ETDEWEB)
Byczuk, Krzysztof [Institute of Theoretical Physics, Warsaw University, ul. Hoza 69, PL-00-681 Warsaw (Poland)]. E-mail: byczuk@fuw.edu.pl; Hofstetter, Walter [Condensed Matter Theory Group, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Vollhardt, Dieter [Theoretical Physics III, Center for Electronic Correlations and Magnetism, Institute for Physics, University of Augsburg, D-86135 Augsburg (Germany)
2005-04-30
The Anderson-Hubbard Hamiltonian at half-filling is investigated within dynamical mean-field theory at zero temperature. The local density of states is calculated by taking the geometric and arithmetic mean, respectively. The non-magnetic ground state phase diagrams obtained within the different averaging schemes are compared.
Energy Technology Data Exchange (ETDEWEB)
Kolorenc, Jindrich [Institute of Physics ASCR, Prague (Czech Republic); University of Hamburg, Hamburg (Germany); Shick, Alexander B. [Institute of Physics ASCR, Prague (Czech Republic); Havela, Ladislav [Charles University, Prague (Czech Republic); Lichtenstein, Alexander I. [University of Hamburg, Hamburg (Germany)
2010-07-01
We provide a numerically efficient procedure to perform LDA+Hubbard I calculations including self-consistency over the charge density in the FP-LAPW basis. The method is applied to Pu, Am, and PuAm and PuCe alloys. Our results for valence photoemission spectra (PES) agree with experimental data and with previous LDA+DMFT calculations. Analysis of the J=5/2 and J=7/2 contributions to the f-occupation supports the intermediate-coupling picture of f-states in heavy actinides. The electronic specific heat coefficient is calculated for PuAm and PuCe alloys in reasonable agreement with recent experiments. We show that Pu atoms keep their mixed-valence character in these alloys. Next, we study electronic and spectral properties of Pu-based superconductor PuCoGa{sub 5} and obtain good agreement with experimental PES. Finally, we analyze surface effects. In Pu monolayer, we find substantial modification of PES due to 5f-electron localization consistent with experimental observations.
Conservation genetics of Lake Superior brook trout: Issues, questions, and directions
Wilson, C.C.; Stott, W.; Miller, L.; D'Amelio, S.; Jennings, Martin J.; Cooper, A.M.
2008-01-01
Parallel efforts by several genetic research groups have tackled common themes relating to management concerns about and recent rehabilitation opportunities for coaster brook trout Salvelinus fontinalis in Lake Superior. The questions that have been addressed include the evolutionary and genetic status of coaster brook trout, the degree of relatedness among coaster populations and their relationship to riverine tributary brook trout populations, and the role and effectiveness of stocking in maintaining and restoring coasters to Lake Superior. Congruent genetic results indicate that coasters are an ecotype (life history variant) rather than an evolutionarily significant unit or genetically distinct strain. Regional structure exists among brook trout stocks, coasters being produced from local populations. Introgression of hatchery genes into wild populations appears to vary regionally and may relate to local population size, habitat integrity, and anthropogenic pressures. Tracking the genetic diversity and integrity associated with captive breeding programs is helping to ensure that the fish used for stocking are representative of their source populations and appropriate for rehabilitation efforts. Comparative analysis of shared samples among collaborating laboratories is enabling standardization of genotype scoring and interpretation as well as the development of a common toolkit for assessing genetic structure and diversity. Incorporation of genetic data into rehabilitation projects will facilitate monitoring efforts and subsequent adaptive management. Together, these multifaceted efforts provide comprehensive insights into the biology of coaster brook trout and enhance restoration options. ?? Copyright by the American Fisheries Society 2008.
Science in Flux: NASA's Nuclear Program at Plum Brook Station 1955-2005
Bowles, Mark D.
2006-01-01
Science in Flux traces the history of one of the most powerful nuclear test reactors in the United States and the only nuclear facility ever built by NASA. In the late 1950's NASA constructed Plum Brook Station on a vast tract of undeveloped land near Sandusky, Ohio. Once fully operational in 1963, it supported basic research for NASA's nuclear rocket program (NERVA). Plum Brook represents a significant, if largely forgotten, story of nuclear research, political change, and the professional culture of the scientists and engineers who devoted their lives to construct and operate the facility. In 1973, after only a decade of research, the government shut Plum Brook down before many of its experiments could be completed. Even the valiant attempt to redefine the reactor as an environmental analysis tool failed, and the facility went silent. The reactors lay in costly, but quiet standby for nearly a quarter-century before the Nuclear Regulatory Commission decided to decommission the reactors and clean up the site. The history of Plum Brook reveals the perils and potentials of that nuclear technology. As NASA, Congress, and space enthusiasts all begin looking once again at the nuclear option for sending humans to Mars, the echoes of Plum Brook's past will resonate with current policy and space initiatives.
HPLC and ELISA analyses of larval bile acids from Pacific and western brook lampreys
Yun, S.-S.; Scott, A.P.; Bayer, J.M.; Seelye, J.G.; Close, D.A.; Li, W.
2003-01-01
Comparative studies were performed on two native lamprey species, Pacific lamprey (Lampetra tridentata) and western brook lamprey (Lampetra richardsoni) from the Pacific coast along with sea lamprey (Petromyzon marinus) from the Great Lakes, to investigate their bile acid production and release. HPLC and ELISA analyses of the gall bladders and liver extract revealed that the major bile acid compound from Pacific and western brook larval lampreys was petromyzonol sulfate (PZS), previously identified as a migratory pheromone in larval sea lamprey. An ELISA for PZS has been developed in a working range of 20pg-10ng per well. The tissue concentrations of PZS in gall bladder were 127.40, 145.86, and 276.96??g/g body mass in sea lamprey, Pacific lamprey, and western brook lamprey, respectively. Releasing rates for PZS in the three species were measured using ELISA to find that western brook and sea lamprey released PZS 20 times higher than Pacific lamprey did. Further studies are required to determine whether PZS is a chemical cue in Pacific and western brook lampreys. ?? 2003 Elsevier Inc. All rights reserved.
Diagenesis of the Lisburne Group, northeastern Brooks Range, Alaska
Energy Technology Data Exchange (ETDEWEB)
Carlson, R.C.; Goldstein, R.H.; Enos, P. [and others
1995-05-01
Petrographic cathodoluminescence studies of the cement stratigraphy of the Lisburne Group yield insights on its diagenetic history. Crosscutting relationships between features of subaerial exposure and calcite cements show that early generations of nonferroan, nonluminescent and multibanded-luminescent calcites are synchronous with or postdated by subaerial exposure surfaces within the Lisburne. Surfaces of subaerial exposure occur at 18 horizons within the Lisburne and are distinguished by features as laminated crusts, rhizoliths, autoclastic breccia, fissure fills, mud cracks, and erosional surfaces. Crosscutting relationships also occur between calcite cements and clasts in karst breccias and conglomerates that formed along the sub-Permian unconformity at the top of the Lisburne. The sub-Permian unconformity postdates later generations of calcite cement. These cements formed in the following sequence: nonferroan to low-ferroan, dully luminescent calcite; ferroan, very-dully luminescent calcite; and second generation of nonferroan, multibanded calcite. The crosscutting relationships not only constrain the timing of cement precipitation, but also suggest that the cements probably were precipitated from meteoric groundwaters introduced during subaerial exposure of the Lisburne platform. Late cements in the Lisburne postdate the Permian Echooka Formation. These cements are low-ferroan, moderately-bright to dully luminescent calcite, followed by a second generation of ferroan, very-dully luminescent calcite. Features of compaction and pressure solution are coincident with the precipitation of the late ferroan calcite and further constrain its timing to deep burial of the Lisburne. The youngest phase of calcite cement precipitated in the Lisburne Group is nonferroan, very-dully luminescent calcite. It commonly fills tectonically-induced shear fractures, indicating precipitation after the onset of Cretaceous (and/or Cenozoic) tectonism in the northeastern Brooks Range.
National Oceanic and Atmospheric Administration, Department of Commerce — The final year of a multi-year effort to study Lophelia coral communities in the Gulf of Mexico is occurring on the TDI-Brooks research vessel, Brooks McCall,...
Field report: Exploring the Doonerak fenster of the central Brooks Range, Alaska, USA
Directory of Open Access Journals (Sweden)
Justin V. Strauss
2017-07-01
Full Text Available Arctic Alaska is a ‘suspect’ terrane that encompasses approximately 20% of Alaska, stretching from the southern Brooks Range all the way to the continental shelves of the Chukchi and Beaufort Seas. Although the origin and subsequent travels of this large crustal fragment are debated among geologists, most researchers agree upon its composite nature and exotic origin. To constrain the early geological history of this terrane, we describe a recent expedition to the Doonerak fenster of the central Brooks Range. This area has long been regarded as a key locality for understanding the structural evolution of the Mesozoic–Cenozoic Brooks Range orogen; however, our target was different: a unique sequence of volcanic and siliciclastic rocks (Apoon assemblage exposed beneath a profound pre-Mississippian unconformity, which we argue is of key importance to understanding the early Paleozoic tectonic history of northern Alaska and the greater Arctic.
Directory of Open Access Journals (Sweden)
Moghadam Hooman K
2011-07-01
Full Text Available Abstract Background Salmonids are regarded as 4R derivative species, having experienced 4 whole genome duplication events in their ancestry. Many duplicated chromosome regions still share extensive homology with one another which is maintained primarily through male-based homeologous chromosome pairings during meiosis. The formation of quadrivalents during meiosis leads to pseudolinkage. This phenomenon is more prevalent within 5 of the 12 ancestral teleost linkage groups in salmonids. Results We constructed a genetic linkage map for brook charr and used this in combination with the genetic map from Arctic charr, to make comparisons with the genetic map of rainbow trout. Although not all chromosome arms are currently mapped, some homologous chromosome rearrangements were evident between Arctic charr and brook charr. Notably, 10 chromosome arms in brook charr representing 5 metacentric chromosomes in Arctic charr have undergone rearrangements. Three metacentrics have one arm translocated and fused with another chromosome arm in brook charr to a make a new metacentrics while two metacentrics are represented by 4 acrocentric pairs in brook charr. In two cases (i.e., BC-4 and BC-16, an apparent polymorphism was observed with the identification of both a putative metacentric structure (similar to metacentric AC-4 = BC-4 and a joining of acrocentric AC-16 + one arm of AC-28 = BC-16, as well as two separate acrocentric linkage groups evident in the mapping parents. Forty-six of the expected 50 karyotypic arms could be inter-generically assigned. SEX in brook charr (BC-4 was localized to the same homologous linkage group region as in Arctic charr (AC-4. The homeologous affinities detected in the two charr species facilitated the identification of 20 (expected number = 25 shared syntenic regions with rainbow trout, although it is likely that some of these regions were partial or overlapping arm regions. Conclusions Inter-generic comparisons among 2
Saha, Srilekha; Maiti, Santanu K.; Karmakar, S. N.
2016-01-01
Electronic behavior of a 1D Aubry chain with Hubbard interaction is critically analyzed in presence of electric field. Multiple energy bands are generated as a result of Hubbard correlation and Aubry potential, and, within these bands localized states are developed under the application of electric field. Within a tight-binding framework we compute electronic transmission probability and average density of states using Green's function approach where the interaction parameter is treated under...
William Keith Brooks and the naturalist's defense of Darwinism in the late-nineteenth century.
Nash, Richard
2015-06-01
William Keith Brooks was an American zoologist at Johns Hopkins University from 1876 until his death in 1908. Over the course of his career, Brooks staunchly defended Darwinism, arguing for the centrality of natural selection in evolutionary theory at a time when alternative theories, such as neo-Lamarckism, grew prominent in American biology. In his book The Law of Heredity (1883), Brooks addressed problems raised by Darwin's theory of pangenesis. In modifying and developing Darwin's pangenesis, Brooks proposed a new theory of heredity that sought to avoid the pitfalls of Darwin's hypothesis. In so doing he strengthened Darwin's theory of natural selection by undermining arguments for the inheritance of acquired characteristics. In later attacks on neo-Lamarckism, Brooks consistently defended Darwin's theory of natural selection on logical grounds, continued to challenge the idea of the inheritance of acquired characteristics, and argued that natural selection best explained a wide range of adaptations. Finally, he critiqued Galton's statistical view of heredity and argued that Galton had resurrected an outmoded typological concept of species, one which Darwin and other naturalists had shown to be incorrect. Brooks's ideas resemble the "biological species concept" of the twentieth century, as developed by evolutionary biologist Ernst Mayr and others. The late-nineteenth century was not a period of total "eclipse" of Darwinism, as biologists and historians have hitherto seen it. Although the "Modern Synthesis" refers to the reconciliation of post-Mendelian genetics with evolution by natural selection, we might adjust our understanding of how the synthesis developed by seeing it as the culmination of a longer discussion that extends back to the late-nineteenth century.
Drude Weight,Optical Conductivity of Two-Dimensional Hubbard Model at Half Filling
Institute of Scientific and Technical Information of China (English)
XU Lei; ZHANG Jun
2008-01-01
We study the Drude weight D and optical conductivity of the two-dimensional (2D) Hubbard model at half filling with staggered magnetic flux (SMF).When SMF being introduced,the hopping integrals are modulated by the magnetic flux.The optical sum rule,which is related to the mean kinetic energy of band electrons,is evaluated for this 2D Hubbard Hamiltonian.Our present result gives the dependence of the kinetic energy,D and the optical conductivity on SMF and U.At half filling D vanishes exponentially with system size.We also find in the frequency dependence of the optical conductivity,there is &function peak at ω≈2|m|U and the incoherent excitations begin to present themselves extended to a higher energy region.
Superconductivity in an attractive two-band Hubbard model with second nearest neighbors
Peraza-Salcedo, D. A.; Rodríguez-Núñez, J. J.; Bonalde, I.; Schmidt, A. A.
2017-04-01
This work extends the calculations performed by G. Litak, T. Örd, K. Rägo, and A. Vargunin, Physica C 483, 30 (2012), by including second nearest neighbors in an attractive two-orbital Hubbard model. We assumed that both the intra-orbital (Ui, i, with i = 1 , 2) and the inter-orbital Hubbard correlations (Ui, j, with i ≠ j) are negative; namely, Ui, j ≤ 0, ∀(i, j). We calculated the T - n phase diagram in the mean-field approximation. For a finite chemical potential ξ10 and a certain second nearest-neighbor parameter t2 superconductivity develops in two dome-like regions, each of which has its own energy gap. Notoriously, for t2 / |t1 | = 0.70 and ξ10 / |t1 | = 3 , where t1 is the nearest-neighbor parameter, Tc becomes zero around n = 2.5 .
Quantum gates and architecture for the quantum simulation of the Fermi-Hubbard model
Dallaire-Demers, Pierre-Luc; Wilhelm, Frank K.
2016-12-01
Quantum computers are the ideal platform for quantum simulations. Given enough coherent operations and qubits, such machines can be leveraged to simulate strongly correlated materials, where intricate quantum effects give rise to counterintuitive macroscopic phenomena such as high-temperature superconductivity. In this paper, we provide a gate decomposition and an architecture for a quantum simulator used to simulate the Fermi-Hubbard model in a hybrid variational quantum-classical algorithm. We propose a simple planar implementation-independent layout of qubits that can also be used to simulate more general fermionic systems. By working through a concrete application, we show the gate decomposition used to simulate the Hamiltonian of a cluster of the Fermi-Hubbard model. We briefly analyze the Trotter-Suzuki errors and estimate the scaling properties of the algorithm for more complex applications.
Spin-spin correlations between two Kondo impurities coupled to an open Hubbard chain
Tiegel, A. C.; Dargel, P. E.; Hallberg, K. A.; Frahm, H.; Pruschke, T.
2013-02-01
In order to study the interplay between Kondo and Ruderman-Kittel-Kasuya-Yosida interaction, we calculate the spin-spin correlation functions between two Kondo impurities coupled to different sites of a half-filled open Hubbard chain. Using the density-matrix renormalization group (DMRG), we reexamine the exponents for the power-law decay of the correlation function between the two impurity spins as a function of the antiferromagnetic coupling J, the Hubbard interaction U, and the distance R between the impurities. The exponents for finite systems obtained in this work deviate from previously published DMRG calculations. We furthermore show that the long-distance behavior of the exponents is the same for impurities coupled to the bulk or to both ends of the chain. We note that a universal exponent for the asymptotic behavior can not be extracted from these finite-size systems with open boundary conditions.
Universal Quantum Computation by Scattering in the Fermi-Hubbard Model
Bao, Ning; Salton, Grant; Thomas, Nathaniel
2014-01-01
The Hubbard model may be the simplest model of particles interacting on a lattice, but simulation of its dynamics remains beyond the reach of current numerical methods. In this article, we show that general quantum computations can be encoded into the physics of wave packets propagating through a planar graph, with scattering interactions governed by the fermionic Hubbard model. Therefore, simulating the model on planar graphs is as hard as simulating quantum computation. We give two different arguments, demonstrating that the simulation is difficult both for wave packets prepared as excitations of the fermionic vacuum, and for hole wave packets at filling fraction one-half in the limit of strong coupling. In the latter case, which is described by the t-J model, there is only reflection and no transmission in the scattering events, as would be the case for classical hard spheres. In that sense, the construction provides a quantum mechanical analog of the Fredkin-Toffoli billiard ball computer.
Detecting phase transitions and crossovers in Hubbard models using the fidelity susceptibility
Huang, Li; Wang, Yilin; Wang, Lei; Werner, Philipp
2016-12-01
A generalized version of the fidelity susceptibility of single-band and multiorbital Hubbard models is systematically studied using single-site dynamical mean-field theory in combination with a hybridization expansion continuous-time quantum Monte Carlo impurity solver. We find that the fidelity susceptibility is extremely sensitive to changes in the state of the system. It can be used as a numerically inexpensive tool to detect and characterize a broad range of phase transitions and crossovers in Hubbard models, including (orbital-selective) Mott metal-insulator transitions, magnetic phase transitions, high-spin to low-spin transitions, Fermi-liquid to non-Fermi-liquid crossovers, and spin-freezing crossovers.
Topological Hubbard model and its high-temperature quantum Hall effect.
Neupert, Titus; Santos, Luiz; Ryu, Shinsei; Chamon, Claudio; Mudry, Christopher
2012-01-27
The quintessential two-dimensional lattice model that describes the competition between the kinetic energy of electrons and their short-range repulsive interactions is the repulsive Hubbard model. We study a time-reversal symmetric variant of the repulsive Hubbard model defined on a planar lattice: Whereas the interaction is unchanged, any fully occupied band supports a quantized spin Hall effect. We show that at 1/2 filling of this band, the ground state develops spontaneously and simultaneously Ising ferromagnetic long-range order and a quantized charge Hall effect when the interaction is sufficiently strong. We ponder on the possible practical applications, beyond metrology, that the quantized charge Hall effect might have if it could be realized at high temperatures and without external magnetic fields in strongly correlated materials.
Low-lying Photoexcited States of a One-Dimensional Ionic Extended Hubbard Model
Yokoi, Kota; Maeshima, Nobuya; Hino, Ken-ichi
2017-10-01
We investigate the properties of low-lying photoexcited states of a one-dimensional (1D) ionic extended Hubbard model at half-filling. Numerical analysis by using the full and Lanczos diagonalization methods shows that, in the ionic phase, there exist low-lying photoexcited states below the charge transfer gap. As a result of comparison with numerical data for the 1D antiferromagnetic (AF) Heisenberg model, it was found that, for a small alternating potential Δ, these low-lying photoexcited states are spin excitations, which is consistent with a previous analytical study [Katsura et al., Phys. Rev. Lett. 103, 177402 (2009)]. As Δ increases, the spectral intensity of the 1D ionic extended Hubbard model rapidly deviates from that of the 1D AF Heisenberg model and it is clarified that this deviation is due to the neutral-ionic domain wall, an elementary excitation near the neutral-ionic transition point.
Singlet exciton condensation and bond-order-wave phase in the extended Hubbard model
Hafez-Torbati, Mohsen; Uhrig, Götz S.
2017-09-01
The competition of interactions implies the compensation of standard mechanisms, which leads to the emergence of exotic phases between conventional phases. The extended Hubbard model (EHM) is a fundamental example for the competition of the local Hubbard interaction and the nearest-neighbor density-density interaction, which at half-filling and in one dimension leads to a bond-order wave (BOW) between a charge-density wave (CDW) and a quasi-long-range order Mott insulator. We study the full momentum-resolved excitation spectrum of the one-dimensional EHM in the CDW phase, and we clarify the relation between different elementary energy gaps. We show that the CDW-to-BOW transition is driven by the softening of a singlet exciton at momentum π . The BOW is realized as the condensate of this singlet exciton.
Random-resistor network description for hopping transport in the presence of Hubbard interaction
Bleibaum, O; Bryksin, V V
2003-01-01
On the basis of the linearized rate equations for hopping electrons in the presence of Hubbard interaction we derive a random resistor network analogue of the transport equations. In contrast to the ordinary Miller-Abraham network our network has two nodes per site. The occurrence of the second node is related to the capability of the system to propagate excitations, and thus is characteristic for the interacting situation. Our random resistor network can be used for the investigation of the transport properties in alternating electric fields and for the investigation of properties of excitations. The network analogue is applied to the calculation of the dynamical conductivity in the nearest-neighbour hopping regime for all Hubbard-interaction strength.
Random-resistor network description for hopping transport in the presence of Hubbard interaction
Energy Technology Data Exchange (ETDEWEB)
Bleibaum, O [Department of Physics and Materials Science Institute, University of Oregon, Eugene, OR 97403 (United States); Boettger, H [Institut fuer Theoretische Physik, Otto-von-Guericke, Universitaet Magdeburg, 399016 Magdeburg (Germany); Bryksin, V V [A F Ioffe Physico-Technical Institute, 194021 St Petersburg (Russian Federation)
2003-03-19
On the basis of the linearized rate equations for hopping electrons in the presence of Hubbard interaction we derive a random resistor network analogue of the transport equations. In contrast to the ordinary Miller-Abraham network our network has two nodes per site. The occurrence of the second node is related to the capability of the system to propagate excitations, and thus is characteristic for the interacting situation. Our random resistor network can be used for the investigation of the transport properties in alternating electric fields and for the investigation of properties of excitations. The network analogue is applied to the calculation of the dynamical conductivity in the nearest-neighbour hopping regime for all Hubbard-interaction strength.
Structure of the Red Dog District, western Brooks Range, Alaska
de Vera, Jean-Pierre P.; McClay, K. R.
2004-01-01
The Red Dog district of the western Brooks Range of northern Alaska, which includes the sediment-hosted Zn-Pb-Ag ± Ba deposits at Red Dog, Su-Lik, and Anarraaq, contains one of the world's largest reserves of zinc. This paper presents a new model for the structural development of the area and shows that understanding the structure is crucial for future exploration efforts and new mineral discoveries in the district. In the Red Dog district, a telescoped Late Devonian through Jurassic continental passive margin is exposed in a series of subhorizontally stacked, internally imbricated, and regionally folded thrust sheets. These sheets were emplaced during the Middle Jurassic to Late Cretaceous Brookian orogeny and subsequently were uplifted by late tectonic activity in the Tertiary. The thrust sheet stack comprises seven tectonostratigraphically distinct allochthonous sheets, three of which have been subject to regional and detailed structural analysis. The lowermost of these is the Endicott Mountains allochthon, which is overlain by the structurally higher Picnic Creek and Kelly River allochthons. Each individual allochthon is itself internally imbricated into a series of tectonostratigraphically coherent and distinct thrust plates and subplates. This structural style gives rise to duplex development and imbrication at a range of scales, from a few meters to tens of kilometers. The variable mechanical properties of the lithologic units of the ancient passive margin resulted in changes in structural styles and scales of structures across allochthon boundaries. Structural mapping and analysis of the district indicate a dominant northwest to west-northwest direction of regional tectonic transport. Local north to north-northeast transport of thrust sheets is interpreted to reflect the influence of underlying lateral and/or oblique ramps, which may have been controlled by inherited basin margin structures. Some thrust-sheet stacking patterns suggest out
Real-space renormalization group study of the Hubbard model on a non-bipartite lattice
Directory of Open Access Journals (Sweden)
R. D. Levine
2002-01-01
Full Text Available Abstract: We present the real-space block renormalization group equations for fermion systems described by a Hubbard Hamiltonian on a triangular lattice with hexagonal blocks. The conditions that keep the equations from proliferation of the couplings are derived. Computational results are presented including the occurrence of a first-order metal-insulator transition at the critical value of U/t Ã¢Â‰Âˆ 12.5.
Aligia, A A; Anfossi, A; Arrachea, L; Degli Esposti Boschi, C; Dobry, A O; Gazza, C; Montorsi, A; Ortolani, F; Torio, M E
2007-11-16
We determine the quantum phase diagram of the one-dimensional Hubbard model with bond-charge interaction X in addition to the usual Coulomb repulsion U>0 at half-filling. For large enough Xtransition to a spontaneously dimerized bond-ordered wave phase and then a charge transition to a novel phase in which the dominant correlations at large distances correspond to an incommensurate singlet superconductor.
Universal conductivity in the boson Hubbard model in a magnetic field
Cha, Min-Chul; Girvin, S. M.
1993-01-01
The universal conductivity at the zero-temperature superconductor-insulator transition of the two-dimensional boson Hubbard model is studied for cases both with and without magnetic field by Monte Carlo simulations of the (2+1)-dimensional classical $XY$-model with disorder represented by random bonds correlated along the imaginary time dimension. The effect of magnetic field is characterized by the frustration $f$. From the scaling behavior of the stiffness, we determine the quantum dynamica...
Emulating the 1-Dimensional Fermi-Hubbard Model with Superconducting Qubits
Reiner, Jan-Michael; Marthaler, Michael; Schön, Gerd
A chain of qubits with both ZZ and XX couplings is described by a Hamiltonian which coincides with the Fermi-Hubbard model in one dimension. The qubit system can thus be used to study the quantum properties of this model. We investigate the specific implementation of such an analog quantum simulator by a chain of tunable Transmon qubits, where the ZZ interaction arises due to an inductive coupling and the XX interaction due to a capacitive coupling.
Semmler, Denis; Byczuk, Krzysztof; Hofstetter, Walter
2009-01-01
Strongly correlated fermions in a crystal or in an optical lattice in the presence of binary alloy disorder are investigated. We employ the statistical dynamical mean-field theory, which incorporates both, local fluctuations due to disorder and local correlations due to interaction, to solve the Anderson-Hubbard model. Localization due to disorder is studied by means of the probability distribution function of the local density of states. We obtain a complete paramagnetic ground state phase d...
Standard model of the rare earths analyzed from the Hubbard I approximation
Locht, I. L. M.; Kvashnin, Y. O.; Rodrigues, D. C. M.; Pereiro, M.; Bergman, A.; Bergqvist, L.; Lichtenstein, A. I.; Katsnelson, M. I.; Delin, A.; Klautau, A. B.; Johansson, B.; Di Marco, I.; Eriksson, O.
2016-08-01
In this work we examine critically the electronic structure of the rare-earth elements by use of the so-called Hubbard I approximation. From the theoretical side all measured features of both occupied and unoccupied states are reproduced, without significant deviations between observations and theory. We also examine cohesive properties like the equilibrium volume and bulk modulus, where we find, in general, a good agreement between theory and measurements. In addition, we have reproduced the spin and orbital moments of these elements as they are reflected from measurements of the saturation moment. We have also employed the Hubbard I approximation to extract the interatomic exchange parameters of an effective spin Hamiltonian for the heavy rare earths. We show that the Hubbard I approximation gives results which are consistent with calculations where 4 f electrons are treated as core states for Gd. The latter approach was also used to address the series of the heavy/late rare earths. Via Monte Carlo simulations we obtained ordering temperatures which reproduce measurements within about 20 % . We have further illustrated the accuracy of these exchange parameters by comparing measured and calculated magnetic configurations for the heavy rare earths and the magnon dispersion for Gd. The Hubbard I approximation is compared to other theories of the electronic structure, and we argue that it is superior. We discuss the relevance of our results in general and how this makes it possible to treat the electronic structure of materials containing rare-earth elements, such as permanent magnets, magnetostrictive compounds, photovoltaics, optical fibers, topological insulators, and molecular magnets.
Exact solution of a generalized two-sites Bose-Hubbard model
Filho, Gilberto N Santos
2016-01-01
I introduce a new parametrization of a bosonic Lax operator for the algebraic Bethe ansatz method with the $gl(2)$-invariant $R$-matrix and use it to present the exact solution of a generalized two-sites Bose-Hubbard model with asymmetric tunnelling. In the no interaction limit I show that the Bethe ansatz equations can be written as a $S^{N-1}$ sphere, where $N$ is the total number of atoms in the condensate.
Anisotropic Hubbard model on a triangular lattice - spin dynamics in HoMnO3
Indian Academy of Sciences (India)
Saptarshi Ghosh; Avinash Singh
2008-01-01
The recent neutron scattering data for spin-wave dispersion in HoMnO3 are well-described by an anisotropic Hubbard model on a triangular lattice with a planar (XY) spin anisotropy. Best fit indicates that magnetic excitations in HoMnO3 correspond to the strong-coupling limit / > ∼ 15, with planar exchange energy = 42/ ≃ 2.5 meV and planar anisotropy ≃ 0.35 meV.
Metallization of solid molecular hydrogen in two dimensions: Mott-Hubbard-type transition
Biborski, Andrzej; Kådzielawa, Andrzej P.; Spałek, Józef
2017-08-01
We analyze the pressure-induced metal-insulator transition in a two-dimensional vertical stack of H2 molecules in (x-y) plane, and show that it represents a striking example of the Mott-Hubbard-type transition. Our combined exact diagonalization approach, formulated and solved in the second quantization formalism, includes also simultaneous ab initio readjustment of the single-particle wave functions, contained in the model microscopic parameters. The system is studied as a function of applied side force (generalized pressure), both in the H2-molecular and H-quasiatomic states. Extended Hubbard model is taken at the start, together with longer-range electron-electron interactions incorporated into the scheme. The stacked molecular plane transforms discontinuously into a (quasi)atomic state under the applied force via a two-step transition: the first between molecular insulating phases and the second from the molecular to the quasiatomic metallic phase. No quasiatomic insulating phase occurs. All the transitions are accompanied by abrupt changes of the bond length and the intermolecular distance (lattice parameter), as well as by discontinuous changes of the principal electronic properties, which are characteristic of the Mott-Hubbard transition here associated with the jumps of the predetermined equilibrium lattice parameter and the effective bond length. The phase transition can be interpreted in terms of the solid hydrogen metallization under pressure exerted by, e.g., the substrate covered with a monomolecular H2 film of the vertically stacked molecules. Both the Mott and Hubbard criteria at the insulator to metal transition are discussed.
Exact many-electron ground states on diamond and triangle Hubbard chains
2008-01-01
We construct exact ground states of interacting electrons on triangle and diamond Hubbard chains. The construction requires (i) a rewriting of the Hamiltonian into positive semidefinite form, (ii) the construction of a many-electron ground state of this Hamiltonian, and (iii) the proof of the uniqueness of the ground state. This approach works in any dimension, requires no integrability of the model, and only demands sufficiently many microscopic parameters in the Hamiltonian which have to fu...
Supersolid Phase in One-Dimensional Hard-Core Boson Hubbard Model with a Superlattice Potential
Institute of Scientific and Technical Information of China (English)
GUO Huai-Ming; LIANG Ying
2008-01-01
The ground state of the one-dimensional hard-core boson Hubbard model with a superlattice potential is studied by quantum Monte Carlo methods. We demonstrate that besides the CDW phase and the Mort insulator phase, the supersolid phase emerges due to the presence of the superlattice potential, which reflects the competition with the hopping term. We also study the densities of sublattices and have a clear idea about the distribution of the bosons on the lattice.
Quantum phase transition and von Neumann entropy of quasiperiodic Hubbard chains
Institute of Scientific and Technical Information of China (English)
Zhu Xuan; Tong Pei-Qing
2008-01-01
The half-filled Hubbard chains with the Fibonacci and Harper modulating site potentials are studied in a selfconsistent mean-field approximation.A new order parameter is introduced to describe a charge density order.We also calculate the yon Neumann entropy of the ground state.The results show that the yon Neumann entropy can identify a CDW/SDW (charge density wave/spin density wave) transition for quasiperiodic models.
Bethe states for the two-site Bose–Hubbard model: A binomial approach
Directory of Open Access Journals (Sweden)
Gilberto Santos
2015-06-01
Full Text Available We calculate explicitly the Bethe vectors states by the algebraic Bethe ansatz method with the gl(2-invariant R-matrix for the two-site Bose–Hubbard model. Using a binomial expansion of the n-th power of a sum of two operators we get and solve a recursion equation. We calculate the scalar product and the norm of the Bethe vectors states. The form factors of the imbalance current operator are also computed.
Methodes d'amas quantiques a temperature finie appliquees au modele de Hubbard
Plouffe, Dany
Depuis leur decouverte dans les annees 80, les supraconducteurs a haute temperature critique ont suscite beaucoup d'interet en physique du solide. Comprendre l'origine des phases observees dans ces materiaux, telle la supraconductivite, est l'un des grands defis de la physique theorique du solide des 25 dernieres annees. L'un des mecanismes pressentis pour expliquer ces phenomenes est la forte interaction electron-electron. Le modele de Hubbard est l'un des modeles les plus simples pour tenir compte de ces interactions. Malgre la simplicite apparente de ce modele, certaines de ses caracteristiques, dont son diagramme de phase, ne sont toujours pas bien etablies, et ce malgre plusieurs avancements theoriques dans les dernieres annees. Cette etude se consacre a faire une analyse de methodes numeriques permettant de calculer diverses proprietes du modele de Hubbard en fonction de la temperature. Nous decrivons des methodes (la VCA et la CPT) qui permettent de calculer approximativement la fonction de Green a temperature finie sur un systeme infini a partir de la fonction de Green calculee sur un amas de taille finie. Pour calculer ces fonctions de Green, nous allons utiliser des methodes permettant de reduire considerablement les efforts numeriques necessaires pour les calculs des moyennes thermodynamiques, en reduisant considerablement l'espace des etats a considerer dans ces moyennes. Bien que cette etude vise d'abord a developper des methodes d'amas pour resoudre le modele de Hubbard a temperature finie de facon generale ainsi qu'a etudier les proprietes de base de ce modele, nous allons l'appliquer a des conditions qui s'approchent de supraconducteurs a haute temperature critique. Les methodes presentees dans cette etude permettent de tracer un diagramme de phase pour l'antiferromagnetisme et la supraconductivite qui presentent plusieurs similarites avec celui des supraconducteurs a haute temperature. Mots-cles : modele de Hubbard, thermodynamique
Doh, Hyeonjin; Salk, Sung-Ho Suck
1996-01-01
Using the Hubbard model Hamiltonian in a mean field level, we examine the variation of antiferromagnetic strength with applied magnetic field. It is demonstrated that minima in the antiferromagnetic strength exist at the the even integer denominator values of rational number for magnetic flux per plaquette. The undulatory behavior of antiferromagnetic strength with the external magnetic field is found. It is seen to be related to the undulatory net statistical phase owing to the influence of ...
Relative and center-of-mass motion in the attractive Bose-Hubbard model
DEFF Research Database (Denmark)
Sørensen, Ole Søe; Gammelmark, Søren; Mølmer, Klaus
2012-01-01
We present first-principles numerical calculations for few-particle solutions of the attractive Bose-Hubbard model with periodic boundary conditions. We show that the low-energy many-body states found by numerical diagonalization can be written as translational superposition states of compact com...... composite systems of particles. These compact states break the translational symmetry of the problem, and their center-of-mass and internal excitations offer simple explanations of the energy spectrum of the full model....
Two-site Hubbard molecule with a spinless electron-positron pair
Cossu, Fabrizio
2012-12-19
We determine the eigenvalues of the two-site Hubbard molecule with one electron and one positron to describe the characteristics of electron-positron interactions in solids. While the effect of hopping is, in general, opposite to the effect of on-site interaction, we find a complex scenario for the electron-positron pair with a non-vanishing potential drop. We give analytical solutions and discuss the combined effects of the model parameters.
Coexistence of Incommensurate Magnetism and Superconductivity in the Two-Dimensional Hubbard Model.
Yamase, Hiroyuki; Eberlein, Andreas; Metzner, Walter
2016-03-04
We analyze the competition of magnetism and superconductivity in the two-dimensional Hubbard model with a moderate interaction strength, including the possibility of incommensurate spiral magnetic order. Using an unbiased renormalization group approach, we compute magnetic and superconducting order parameters in the ground state. In addition to previously established regions of Néel order coexisting with d-wave superconductivity, the calculations reveal further coexistence regions where superconductivity is accompanied by incommensurate magnetic order.
Ground state phase diagram of the half-filled bilayer Hubbard model
Golor, Michael; Reckling, Timo; Classen, Laura; Scherer, Michael M.; Wessel, Stefan
2014-01-01
Employing a combination of functional renormalization group calculations and projective determinantal quantum Monte Carlo simulations, we examine the Hubbard model on the square lattice bilayer at half filling. From this combined analysis, we obtain a comprehensive account on the ground state phase diagram with respect to the extent of the system's metallic and (antiferromagnetically ordered) Mott-insulating as well as band-insulating regions. By means of an unbiased functional renormalizatio...
Schäfer, T.; Ciuchi, S.; Wallerberger, M.; Thunström, P.; Gunnarsson, O.; Sangiovanni, G.; Rohringer, G.; Toschi, A.
2016-12-01
We analyze the highly nonperturbative regime surrounding the Mott-Hubbard metal-to-insulator transition (MIT) by means of dynamical mean field theory (DMFT) calculations at the two-particle level. By extending the results of Schäfer et al. [Phys. Rev. Lett. 110, 246405 (2013), 10.1103/PhysRevLett.110.246405] we show the existence of infinitely many lines in the phase diagram of the Hubbard model where the local Bethe-Salpeter equations, and the related irreducible vertex functions, become singular in the charge as well as the particle-particle channel. By comparing our numerical data for the Hubbard model with analytical calculations for exactly solvable systems of increasing complexity [disordered binary mixture (BM), Falicov-Kimball (FK), and atomic limit (AL)], we have (i) identified two different kinds of divergence lines; (ii) classified them in terms of the frequency structure of the associated singular eigenvectors; and (iii) investigated their relation to the emergence of multiple branches in the Luttinger-Ward functional. In this way, we could distinguish the situations where the multiple divergences simply reflect the emergence of an underlying, single energy scale ν* below which perturbation theory is no longer applicable, from those where the breakdown of perturbation theory affects, not trivially, different energy regimes. Finally, we discuss the implications of our results on the theoretical understanding of the nonperturbative physics around the MIT and for future developments of many-body algorithms applicable in this regime.
Quantum phase diagram of the half filled Hubbard model with bond-charge interaction
Energy Technology Data Exchange (ETDEWEB)
Dobry, A.O., E-mail: dobry@ifir-conicet.gov.a [Facultad de Ciencias Exactas Ingenieria y Agrimensura, Universidad Nacional de Rosario and Instituto de Fisica Rosario, Bv. 27 de Febrero 210 bis, 2000 Rosario (Argentina); Aligia, A.A. [Centro Atomico Bariloche and Instituto Balseiro, Comision Nacional de Energia Atomica, 8400 Bariloche (Argentina)
2011-02-21
Using quantum field theory and bosonization, we determine the quantum phase diagram of the one-dimensional Hubbard model with bond-charge interaction X in addition to the usual Coulomb repulsion U at half-filling, for small values of the interactions. We show that it is essential to take into account formally irrelevant terms of order X. They generate relevant terms proportional to X{sup 2} in the flow of the renormalization group (RG). These terms are calculated using operator product expansions. The model shows three phases separated by a charge transition at U=U{sub c} and a spin transition at U=U{sub s}>U{sub c}. For UU{sub s}, the system is in the spin-density wave phase as in the usual Hubbard model. For intermediate values U{sub c}Hubbard model with X=0. We obtain that the charge transition remains at U{sub c}=0 for X{ne}0. Solving the RG equations for the spin sector, we provide an analytical expression for U{sub s}(X). The results, with only one adjustable parameter, are in excellent agreement with numerical ones for X
Energy Technology Data Exchange (ETDEWEB)
Mishra, A.K., E-mail: mishra@imsc.res.i [Insitituto Nacional de Pesquidas Espaciais - INPE, P.O. Box 103, CP 515, S. J. Campos, SP 12245-970 (Brazil); Kishore, R., E-mail: kishore@las.inpe.b [Insitituto Nacional de Pesquidas Espaciais - INPE, P.O. Box 103, CP 515, S. J. Campos, SP 12245-970 (Brazil)
2009-10-15
The exact nested Bethe ansatz solution for the one dimensional (1-D) U infinity Hubbard model show that the state vectors are a product of spin-less fermion and spin wavefunctions, or an appropriate superposition of such factorized wavefunctions. The spin-less fermion component of the wavefunctions ensures no double occupancy at any site. It had been demonstrated that the nested Bethe ansatz wavefunctions in the U infinity limit obey orthofermi statistics. Gutzwiller projection operator formalism is the another well known technique employed to handle U infinity Hubbard model. In general, this approach does not lead to spin-less fermion wavefunctions. Therefore, the nested Bethe ansatz and Gutzwiller projection operator approach give rise to different kinds of the wavefunctions for the U infinity limit of 1-D Hubbard Hamiltonian. To compare the consequences of this dissimilarity in the wavefunctions, we have obtained the ground state energy of a finite system consisting of three particles on a four site closed chain. It is shown that in the nested Bethe ansatz implemented through orthofermion algebra, all the permissible 2{sup 3} spin configurations are degenerate in the ground state. This eight fold degeneracy of the ground state is absent in the Gutzwiller projection operator approach. This finding becomes relevant in the context of known exact U infinity results, which require that all the energy levels are 2{sup N}-fold degenerate for an N particle system.
Flow equations and the strong-coupling expansion for the Hubbard model
Stein, Jürgen
1997-07-01
Applying the method of continuous unitary transformations to a class of Hubbard models, we reexamine the derivation of the t/U expansion for the strong-coupling case. The flow equations for the coupling parameters of the higher order effective interactions can be solved exactly, resulting in a systematic expansion of the Hamiltonian in powers of t/U, valid for any lattice in arbitrary dimension and for general band filling. The expansion ensures a correct treatment of the operator products generated by the transformation, and only involves the explicit recursive calculation of numerical coefficients. This scheme provides a unifying framework to study the strong-coupling expansion for the Hubbard model, which clarifies and circumvents several difficulties inherent to earlier approaches. Our results are compared with those of other methods, and it is shown that the freedom in the choice of the unitary transformation that eliminates interactions between different Hubbard bands can affect the effective Hamiltonian only at order t 3/U2 or higher.
Purkayastha, Archak; Dhar, Abhishek; Kulkarni, Manas
2016-11-01
Recent experiments in hybrid-quantum systems facilitate the potential realization of one of the most fundamental interacting Hamiltonian-reservoir systems, namely the single-site Bose-Hubbard model coupled to two reservoirs at different temperatures. Using Redfield equations in a Born-Markov approximation, we compute nonequilibrium average particle number, energy, and currents beyond linear response regime, both time dynamics and steady state, and investigate its dependence on various tunable parameters analytically. We find interesting scaling laws in high-temperature regimes that are independent of choice of bath spectral functions. We also demonstrate that the system shows very interesting particle and energy current rectification properties which can be controlled via the relative strength of interaction and temperatures, as well as via the degree of asymmetry in system-bath coupling. Specifically, we find inversion of direction of energy rectification as a function of the relative strength of the interaction strength and the temperatures. We also show that, in the limit of low-temperature and high interaction strength, our results are consistent with the nonequilibrium spin-Boson model. Our results are experimentally relevant not only to hybrid quantum systems but also in other areas such as molecular junctions.
System-parameter dependence of the metallic phase of the non-doped 2D Hubbard model
Energy Technology Data Exchange (ETDEWEB)
Yamaji, K., E-mail: yamaji-kuni@aist.go.j [Nanoelectronics Research Institute, AIST Central 2, 1-1-1 Umezono, Tsukuba 305-8568 (Japan); Yanagisawa, T. [Nanoelectronics Research Institute, AIST Central 2, 1-1-1 Umezono, Tsukuba 305-8568 (Japan); Miyazaki, M. [Hakodate National College of Technology, 14-1 Tokura-cho, Hakodate 042-8501 (Japan); Kadono, R. [Institute of Materials Structure Science, KEK, 1-1 Oho, Tsukuba 305-0801 (Japan)
2009-10-15
Naito et al. reported that some non-doped T'-214-type compounds drive high-T{sub c} superconductivity. The compounds are considered to be metallic since on-site Coulomb energy U is moderate and the Fermi surface is much deformed in these compounds. In order to confirm this picture and extract electronic structure information, we have examined the phase diagram of the metallic state of the 2D Hubbard model as a function of U and t' (with t'' we fixed at -t'/2 here; t' and t'' are the second- and third-neighbor transfer energies, respectively) by means of the variational Monte-Carlo method. We employed a Jastrow-type Gutzwiller trial wave function. In the studied range of U 2-12, the boundary value for |t'| at which SDW disappears increases almost linearly with U. Jump-wise transition to the Mott insulator state was not observed. Using the boundary curve and experimental band parameter values, we estimate U approx 5 for T'-214 compounds. Preceding works are discussed in the last part.
Dalmonte, M.; Lechner, W.; Cai, Zi; Mattioli, M.; Läuchli, A. M.; Pupillo, G.
2015-07-01
We investigate the quantum phases of hard-core bosonic atoms in an extended Hubbard model where particles interact via soft-shoulder potentials in one dimension. Using a combination of field-theoretical methods and strong-coupling perturbation theory, we demonstrate that the low-energy phase can be a conformal cluster Luttinger liquid (CLL) phase with central charge c =1 , where the microscopic degrees of freedom correspond to mesoscopic ensembles of particles. Using numerical density-matrix renormalization-group methods, we demonstrate that the CLL phase [first predicted in M. Mattioli et al., Phys. Rev. Lett. 111, 165302 (2013), 10.1103/PhysRevLett.111.165302] is separated from a conventional Tomonaga-Luttinger liquid by an exotic critical point with central charge c =3/2 . The latter is expression of an emergent conformal supersymmetry, which is not present in the original Hamiltonian. We discuss the observability of the CLL phase in realistic experimental settings with weakly dressed Rydberg atoms confined to optical lattices. Using quantum Monte Carlo simulations, we show that the typical features of CLLs are stable up to comparatively high temperatures. Using exact diagonalizations and quantum trajectory methods, we provide a protocol for adiabatic state preparation as well as quantitative estimates on the effects of particle losses.
Near Realtime Monitoring of Tidewater Glacier Advance and Retreat: Hubbard Glacier, Southeast Alaska
Finnegan, D. C.; Lawson, D. E.; Hanlon, G.; Kalli, G.
2007-12-01
Tidewater glaciers advance and retreat seasonally as part of the well-documented tidewater glacier cycle. Quantitative factors that influence tidewater glacier activity are often difficult to capture. The accurate collection of such data is a key to better understanding this cycle. In this paper, we describe the results of current research at Hubbard Glacier to quantify realtime glacier terminus activity using high-resolution ranging measurements and local meteorologic conditions. Hubbard Glacier is the largest non-polar tidewater glacier in the world. It encompasses an area of 3500 sq km and flows 120 km from the flanks of Mt Logan (5959 m) in the Wrangell St. Elias Mountains (Canada) to sea level where its terminus widens to ~11.5 km. In contrast to most glaciers in Southeast Alaska, Hubbard Glacier continues to advance and thicken and is predicted to continue for the foreseeable future. Our data provide unique, high-resolution (4 times daily) measurements of ice margin motion along a section of the terminus near Gilbert Point. Gilbert Point is the location of past ice dams formed by Hubbard Glacier (1986, 2002) both of which failed and generated massive outburst floods. This location is critical to understanding the potential for future ice dam formation by Hubbard Glacier. Preliminary results of monitoring since late 2006 indicate variable rates in ice motion within periods of overall advance and retreat. A seasonal advance of the glacier occurred from March to mid-June 2007, advancing 280 m in 98 days at an average of 2.85 m/day, but with daily average rates occasionally as high as 10 m/day. A period of retreat began in mid-June with a large calving event that removed 60 m of ice from the terminus in less than a day. This seasonal retreat has continued with retreat rates varying from 1.11 m/day in the first 45 days to 2.39 m/day between August 1st and 30th, 2007.
SOIL ALUMINUM DISTRIBUTION IN THE NEAR-STREAM ZONE AT THE BEAR BROOK WATERSHED IN MAINE
Near-stream and upslope soil chemical properties were analyzed to infer linkages between soil and surface water chemistry at the Bear Brook Watershed in Maine [BBWM]. Organic and mineral soil samples were collected along six 20 m transects perpendicular to the stream and one 200 ...
The Spine of Literature: A Conversation between Eudora Welty and Cleanth Brooks.
Taylor, Caroline
1988-01-01
Describes a discussion between Cleanth Brooks and Eudora Welty about the state of the story in today's fiction. Characterizes the narrative form as the spine of literature. Points out that, too often, contemporary writers neglect this form of writing and instead emphasize a type of prose poetry. Notes that authors today overemphasize the present…
The Spine of Literature: A Conversation between Eudora Welty and Cleanth Brooks.
Taylor, Caroline
1988-01-01
Describes a discussion between Cleanth Brooks and Eudora Welty about the state of the story in today's fiction. Characterizes the narrative form as the spine of literature. Points out that, too often, contemporary writers neglect this form of writing and instead emphasize a type of prose poetry. Notes that authors today overemphasize the present…
On the identity of Cervus nigricans Brooke, 1877, with remarks upon other deer from the Philippines
Dobroruka, L.J.
1971-01-01
A great number of papers deal with the deer of the Philippine Islands but in spite of this fact the taxonomy and the nomenclature are still not clear. The first author who recapitulated all known facts about the Philippine deer was Brooke (1877), who also described a new species, Cervus nigricans.
IMPACTS OF MARINE AEROSOLS ON SURFACE WATER CHEMISTRY AT BEAR BROOK WATERSHED, MAINE USA
The East Bear catchment at Bear Brook Watershed, Maine receives moderate (for the eastern U.S.) amounts of Cl- in wet and dry deposition. In 1989, Cl- in precipitation ranged from 2 to 55 eq/L. Dry, occult, and wet deposition plus evapotranspiration resulted in stream Cl- averagi...
Noaksson, E.; Linderoth, M.; Bosveld, A.T.C.; Norrgren, L.; Zebühr, Y.; Balk, L.
2003-01-01
Lake Molnbyggen was previously found to harbour a large number of sexually immature female perch (Perca fluviatilis) suffering from endocrine disruption. In an attempt to pin-point the source of the endocrine-disrupting substance(s) (EDSs), brook trout (Salvelinus fontinalis) from Vadbacken, a strea
Weck, Philippe F; Kim, Eunja
2016-09-29
The structure-property relationships of bulk CeO2 and Ce2O3 have been investigated using AM05 and PBEsol exchange-correlation functionals within the frameworks of Hubbard-corrected density functional theory (DFT+U) and density functional perturbation theory (DFPT+U). Compared with conventional PBE+U, RPBE+U, PW91+U and LDA+U functionals, AM05+U and PBEsol+U describe experimental crystalline parameters and properties of CeO2 and Ce2O3 with superior accuracy, especially when +U is chosen close to its value derived by the linear-response approach. The present findings call for a reexamination of some of the problematic oxide materials featuring strong f- and d-electron correlation using AM05+U and PBEsol+U.
Reliability of the Suchey-Brooks method for a French contemporary population.
Savall, Frédéric; Rérolle, Camille; Hérin, Fabrice; Dédouit, Fabrice; Rougé, Daniel; Telmon, Norbert; Saint-Martin, Pauline
2016-09-01
The Suchey-Brooks method is commonly used for pubic symphyseal aging in forensic cases. However, inter-population variability is a problem affected by several factors such as geographical location and secular trends. The aim of our study was to test the reliability of the Suchey-Brooks method on a virtual sample of contemporary French males. We carried out a retrospective study of 680 pubic symphysis from adult males undergoing clinical Multislice Computed Tomography in two hospitals between January 2013 and July 2014 (Toulouse and Tours, France). The reliability of the Suchey-Brooks method was tested by the calculation of inaccuracy and bias between real and estimated ages, and the mean age for each stage and the mean stage for each 10-years age interval were compared. The degree of inaccuracy and bias increased with age and inaccuracy exceeded 20 years for individuals over 65 years of age. The results are consistent with an overestimation of the real age for stages I and II and an underestimation of the real age for stages IV, V and VI. Furthermore, the mean stages of the reference sample were significantly lower for the 14-25 age group and significantly higher for individuals over 35 years old. Age estimation is potentially limited by differential inter-population error rates between geographical locations. Furthermore, the effects of secular trends are also supported by research in European countries showing a reduction in the age of attainment of indicators of biological maturity during the past few decades. The results suggest that the Suchey-Brooks method should be used with caution in France. Our study supports previous findings and in the future, the Suchey-Brooks method could benefit from re-evaluation of the aging standards by the establishment of new virtual reference samples.
Nystrom, Elizabeth A.; Burns, Douglas A.
2011-01-01
TOPMODEL, a physically based, variable-source area rainfall-runoff model, was used to simulate streamflow and depth to water table for the period January 2007-September 2009 in the 65.6 square kilometers of Fishing Brook Watershed in northern New York. The Fishing Brook Watershed is located in the headwaters of the Hudson River and is predominantly forested with a humid, cool continental climate. The motivation for applying this model at Fishing Brook was to provide a simulation that would be effective later at this site in modeling the interaction of hydrologic processes with mercury dynamics.
CRED 20 m Gridded bathymetry of Brooks Banks and St.Rogatien Bank, Hawaii, USA (NetCDF format)
National Oceanic and Atmospheric Administration, Department of Commerce — Gridded bathymetry (20m) of the shelf and slope environments of Brooks Banks and St. Rogatien, Hawaii, USA. The netCDF grid includes multibeam bathymetry from the...
National Oceanic and Atmospheric Administration, Department of Commerce — Reson 8101ER multibeam Data were collected between 13-15 October 2006 aboard NOAA Survey Launch Acoustic Habitat Investigator (AHI) Brooks Banks in the Northwestern...
CRED 20 m Gridded bathymetry of Brooks Banks and St. Rogatien Bank, Hawaii, USA (Arc ASCII format)
National Oceanic and Atmospheric Administration, Department of Commerce — Gridded bathymetry (20m) of the shelf and slope environments of Brooks Banks and St. Rogatien, Hawaii, USA. The ASCII includes multibeam bathymetry from the Simrad...
National Research Council Canada - National Science Library
Pankaj S. Bhatnagar
2013-01-01
The present study aims at extracting the fossil database www.paleodb.org to compare extinct megafauna genera, Mammuthus Brookes, 1828 and Mammut Blumenbach, 1799 along with its close reletive, Zygolophodon (Vacek, 1877...
p-wave superconductivity in a two-dimensional generalized Hubbard model
Energy Technology Data Exchange (ETDEWEB)
Millan, J. Samuel [Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico (UNAM), Apartado Postal 70-360, 04510, Mexico D.F. (Mexico); Facultad de Ingenieria, UNACAR, 24180, Cd. de Carmen, Campeche (Mexico); Perez, Luis A. [Instituto de Fisica, UNAM, Apartado Postal 20-364, 01000, Mexico D.F. (Mexico); Wang Chumin [Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico (UNAM), Apartado Postal 70-360, 04510, Mexico D.F. (Mexico)]. E-mail: chumin@servidor.unam.mx
2005-02-21
In this Letter, we consider a two-dimensional Hubbard model that includes a second-neighbor correlated hopping interaction, and we find a triplet p-wave superconducting ground state within the BCS formalism. A small distortion of the square-lattice right angles is introduced in order to break the degeneracy of kx+/-ky oriented p-wave pairing states. For the strong coupling limit, analytical results are obtained. An analysis of the superconducting critical temperature reveals the existence of an optimal electron density and the gap ratio exhibits a non-BCS behavior. Finally, the particular case of strontium ruthenate is examined.
Doping driven metal-insulator transitions and charge orderings in the extended Hubbard model
Kapcia, K J; Capone, M; Amaricci, A
2016-01-01
We perform a thorough study of an extended Hubbard model featuring local and nearest-neighbor Coulomb repulsion. Using dynamical mean-field theory we investigated the zero temperature phase-diagram of this model as a function of the chemical doping. The interplay between local and non-local interaction drives a variety of phase-transitions connecting two distinct charge-ordered insulators, i.e., half-filled and quarter-filled, a charge-ordered metal and a Mott insulating phase. We characterize these transitions and the relative stability of the solutions and we show that the two interactions conspire to stabilize the quarter-filled charge ordered phase.
Phase diagram of the extended Hubbard chain with charge-dipole interactions
Torio, M. E.; Aligia, A. A.; Hallberg, K.; Ceccatto, H. A.
2000-01-01
We consider a modified extended Hubbard model (EHM) which, in addition to the on-site repulsion U and nearest-neighbor repulsion V, includes polarization effects in second-order perturbation theory. The model is equivalent to an EHM with renormalized U plus a next-nearest-neighbor repulsion term. Using a method based on topological quantum numbers (charge and spin Berry phases), we generalize to finite hopping t the quantum phase diagram in one dimension constructed by van den Brink et al. (P...
Ultralong-range order in the Fermi-Hubbard model with long-range interactions
van Loon, Erik G. C. P.; Katsnelson, Mikhail I.; Lemeshko, Mikhail
2015-08-01
We use the dual boson approach to reveal the phase diagram of the Fermi-Hubbard model with long-range dipole-dipole interactions. By using a large-scale finite-temperature calculation on a 64 ×64 square lattice we demonstrate the existence of a novel phase, possessing an "ultralong-range" order. The fingerprint of this phase—the density correlation function—features a nontrivial behavior on a scale of tens of lattice sites. We study the properties and the stability of the ultralong-range-ordered phase, and show that it is accessible in modern experiments with ultracold polar molecules and magnetic atoms.
Critical behavior near the Mott transition in the half-filled asymmetric Hubbard model
Energy Technology Data Exchange (ETDEWEB)
Hoang, Anh-Tuan, E-mail: hatuan@iop.vast.ac.vn [Institute of Physics, Vietnam Academy of Science and Technology, Hanoi (Viet Nam); Le, Duc-Anh [Faculty of Physics, Hanoi National University of Education, Xuan Thuy 136, Cau Giay, Hanoi 10000 (Viet Nam)
2016-03-15
We study the half-filled asymmetric Hubbard model within the two-site dynamical mean field theory. At zero temperature, explicit expressions of the critical interaction U{sub c} for the Mott transition and the local self-energy are analytically derived. Critical behavior of the quasiparticle weights and the double occupancy are obtained analytically as functions of the on-site interaction U and the hopping asymmetry r. Our results are in good agreement with the ones obtained by much more sophisticated theory.
Fractional charge separation in the hard-core Bose Hubbard Model on the Kagome Lattice
Zhang, Xue Feng; Eggert, Sebastian
2013-03-01
We consider the hard core Bose Hubbard Model on a Kagome lattice with fixed (open) boundary conditions on two edges. We find that the fixed boundary conditions lift the degeneracy and freeze the system at 1/3 and 2/3 filling at small hopping. At larger hopping strengths, fractional charges spontaneously separate and are free to move to the edges of the system, which leads to a novel compressible phase with solid order. The compressibility is due to excitations on the edge which display a chrial symmetry breaking that is reminiscent of the quantum Hall effect. Large scale Monte Carlo simulations confirm the analytical calculations.
Spontaneously Symmetry-Breaking States in the Attractive SU(N) Hubbard Model
Koga, Akihisa; Yanatori, Hiromasa
2017-03-01
We investigate spontaneously symmetry-breaking states in the attractive SU(N) Hubbard model at half filling. Combining dynamical mean-field theory with the continuous-time quantum Monte Carlo method, we obtain finite-temperature phase diagrams for the superfluid state. When N > 2, a second-order phase transition occurs in the weak coupling region, while a first-order phase transition with hysteresis appears in the strong coupling region. We also discuss the stability of the density wave state and clarify the component dependence of the maximum critical temperature.
Many-site coherence revivals in the extended Bose-Hubbard model and the Gutzwiller approximation
Energy Technology Data Exchange (ETDEWEB)
Fischer, Uwe R.; Xiong Bo [Seoul National University, Department of Physics and Astronomy, Center for Theoretical Physics, 151-747 Seoul (Korea, Republic of)
2011-12-15
We investigate the collapse and revival of first-order coherence in deep optical lattices when long-range interactions are turned on and find that the first few revival peaks are strongly attenuated already for moderate values of the nearest-neighbor interaction coupling. It is shown that the conventionally employed Gutzwiller wave function, with only on-site number dependence of the variational amplitudes, leads to incorrect predictions for the collapse and revival oscillations within the extended Bose-Hubbard model. We provide a modified variant of the Gutzwiller ansatz, reproducing the analytically calculated time dependence of first-order coherence in the limit of zero tunneling.
Irrigação da bolsa cloacal em Gallus gallus domesticus (Matrizes de corte Hubbard
Directory of Open Access Journals (Sweden)
Marcelo Ismar Silva Santana
2003-01-01
Full Text Available The Cloacal Bursa's arteries of 30 females Hubbard were injected with 50% Neoprene Latex 450 solution, and submited to dissection. The ages of the birds was to 10 to 12 weeks. The vessel's origin, number and sequence were studied The results showed the participation of the left and right internal pudendal artery in all cases, witch the association of the cranial mesenteric artery (333,33%, to median caudal artery (3,33%, and to left internal iliac artery (3,33%. The total branches number, without considering its origin, varied in 2 to 9, being 4 branches the major frequency. The vessels distribuition was the same in each bird.
Sauter-Schwinger like tunneling in tilted Bose-Hubbard lattices in the Mott phase
Queisser, Friedemann; Schützhold, Ralf
2011-01-01
We study the Mott phase of the Bose-Hubbard model on a tilted lattice. On the (Gutzwiller) mean-field level, the tilt has no effect -- but quantum fluctuations entail particle-hole pair creation via tunneling. For small potential gradients (long-wavelength limit), we derive a quantitative analogy to the Sauter-Schwinger effect, i.e., electron-positron pair creation out of the vacuum by an electric field. For large tilts, we obtain resonant tunneling related to Bloch oscillations.
Unified Solutions of the Hard-Core Fermi-and Bose-Hubbard Models
Institute of Scientific and Technical Information of China (English)
PAN Feng; DAI Lian-Rong
2003-01-01
A unified algebraic approach to both the hard-core Fermi- and Bose-Hubbard models is extended to boththe finite- and infinite-site with periodic condition cases. Excitation energies and the corresponding wavefunctions ofboth the models with nearest neighbor hopping are exactly derived by using a new and simple algebraic method. It isfound that spectra of both the models are determined simply by eigenvalue problem of N × N hopping matrix, where Nis the number of sites for finite system or the period of sites for infinite system.
Metal-Insulator Transition in the Hubbard Model: Correlations and Spiral Magnetic Structures
Timirgazin, Marat A.; Igoshev, Petr A.; Arzhnikov, Anatoly K.; Irkhin, Valentin Yu.
2016-12-01
The metal-insulator transition (MIT) for the square, simple cubic, and body-centered cubic lattices is investigated within the t-t^' Hubbard model at half-filling by using both the generalized for the case of spiral order Hartree-Fock approximation (HFA) and Kotliar-Ruckenstein slave-boson approach. It turns out that the magnetic scenario of MIT becomes superior over the non-magnetic one. The electron correlations lead to some suppression of the spiral phases in comparison with HFA. We found the presence of a metallic antiferromagnetic (spiral) phase in the case of three-dimensional lattices.
Transport Properties near Quantum Critical Point in 2D Hubbard Model
Chen, Kuang-Shing; Pathak, Sandeep; Yang, Shuxiang; Su, Shi-Quan; Galanakis, Dimitris; Mikelsons, Karlis; Moreno, Juana; Jarrell, Mark
2011-03-01
We obtain high quality estimates of the self energy Σ (K , ω) by direct analytic continuation of Σ (K , iωn) obtained from Continuous-Time Quantum Monte Carlo. We use these results to investigate the transport properties near the quantum critical point found in the 2D Hubbard model at finite doping. Resistivity, thermal conductivity, Wiedemann-Franz Law, and thermopower are examined in the Fermi liquid, Marginal Fermi liquid (MFL), and pseudo-gap regions. Σ (k , ω) with k along the nodal direction displays temperature-dependent scaling similar to that seen in the experiment. A next-nearest neighbor hopping tOISE-0730290.
On the origin of quantum criticality found at finite doping in 2D Hubbard model
Yang, Shuxiang; Fotso, Herbert; Moreno, Juana; Jarrell, Mark
2011-03-01
To better understand the excitations responsible for quantum criticality (QC) found at finite doping in the 2D Hubbard model, we analyze the vertices for different scattering channels obtained from the Dynamical Cluster Continuous-Time Quantum Monte Carlo simulation. By decomposing these vertices using the parquet equations we find that both superconductivity and the charge instabilities responsible for the QC come from the crossed spin channel contribution, and thus are driven by the spin-fluctuations. On contrast, the spin instability comes from the fully irreducible spin vertex contribution. We acknowledge the support from NSF OISE-0730290 and DOE SciDAC DE-FC02-06ER25792.
The Mott metal-insulator transition in half-filled two-dimensional Hubbard models
Directory of Open Access Journals (Sweden)
Peyman Sahebsara
2008-06-01
Full Text Available We study the Mott transition in the two dimensional Hubbard model by using the variational cluster approximation. The transition potential obtained is roughly Uc ≈ 2 and 6 for square and triangular lattices, respectively. A comparison between results of this approximation and other quantum cluster methods is presented. Our zero-temperature calculation at strong coupling show that the transition on the triangular and square lattices occur at lower values of compared with other numerical techniques such as DMFT, CDMFT, and DCA. We also study the thermodynamic limit by an extrapolation to infinite size.
Absence of full many-body localization in the disordered Hubbard chain
Prelovšek, P.; Barišić, O. S.; Žnidarič, M.
2016-12-01
We present numerical results within the one-dimensional disordered Hubbard model for several characteristic indicators of the many-body localization (MBL). Considering traditionally studied charge disorder (i.e., the same disorder strength for both spin orientations) we find that even at strong disorder all signatures consistently show that while charge degree of freedom is nonergodic, the spin is delocalized and ergodic. This indicates the absence of the full MBL in the model that has been simulated in recent cold-atom experiments. Full localization can be restored if spin-dependent disorder is used instead.
Phase diagram of the bosonic Kondo-Hubbard model
Energy Technology Data Exchange (ETDEWEB)
Foss-Feig, Michael; Rey, Ana Maria [JILA, National Institute of Standards and Technology, and University of Colorado, Boulder, Colorado 80309 (United States)
2011-11-15
We study a bosonic version of the Kondo lattice model with an onsite repulsion in the conduction band, implemented with alkali-metal atoms in two bands of an optical lattice. Using both weak- and strong-coupling perturbation theory, we find that at unit filling of the conduction bosons the superfluid-to-Mott-insulator transition should be accompanied by a magnetic transition from a ferromagnet (in the superfluid) to a paramagnet (in the Mott insulator). Furthermore, an analytic treatment of Gutzwiller mean-field theory reveals that quantum spin fluctuations induced by the Kondo exchange cause the otherwise continuous superfluid-to-Mott-insulator phase transition to be first order. We show that lattice separability imposes a serious constraint on proposals to exploit excited bands for quantum simulations, and discuss a way to overcome this constraint in the context of our model by using an experimentally realized nonseparable lattice. A method to probe the first-order nature of the transition based on collapses and revivals of the matter-wave field is also discussed.
Thornton, Emily J; Duda, Jeff; Quinn, Thomas P
2016-01-01
Resource competition between animals is influenced by a number of factors including the species, size and relative abundance of competing individuals. Stream-dwelling animals often experience variably available food resources, and some employ territorial behaviors to increase their access to food. We investigated the factors that affect dominance between resident, non-native brook trout and recolonizing juvenile coho salmon in the Elwha River, WA, USA, to see if brook trout are likely to disrupt coho salmon recolonization via interference competition. During dyadic laboratory feeding trials, we hypothesized that fish size, not species, would determine which individuals consumed the most food items, and that species would have no effect. We found that species, not size, played a significant role in dominance; coho salmon won 95% of trials, even when only 52% the length of their brook trout competitors. As the pairs of competing fish spent more time together during a trial sequence, coho salmon began to consume more food, and brook trout began to lose more, suggesting that the results of early trials influenced fish performance later. In group trials, we hypothesized that group composition and species would not influence fish foraging success. In single species groups, coho salmon consumed more than brook trout, but the ranges overlapped. Brook trout consumption remained constant through all treatments, but coho salmon consumed more food in treatments with fewer coho salmon, suggesting that coho salmon experienced more intra- than inter-specific competition and that brook trout do not pose a substantial challenge. Based on our results, we think it is unlikely that competition from brook trout will disrupt Elwha River recolonization by coho salmon.
Johnson, T H; Yuan, Y; Bao, W; Clark, S R; Foot, C; Jaksch, D
2016-06-17
We investigate cold bosonic impurity atoms trapped in a vortex lattice formed by condensed bosons of another species. We describe the dynamics of the impurities by a bosonic Hubbard model containing occupation-dependent parameters to capture the effects of strong impurity-impurity interactions. These include both a repulsive direct interaction and an attractive effective interaction mediated by the Bose-Einstein condensate. The occupation dependence of these two competing interactions drastically affects the Hubbard model phase diagram, including causing the disappearance of some Mott lobes.
Saha, Srilekha; Maiti, Santanu K.; Karmakar, S. N.
2016-09-01
Electronic behavior of a 1D Aubry chain with Hubbard interaction is critically analyzed in presence of electric field. Multiple energy bands are generated as a result of Hubbard correlation and Aubry potential, and, within these bands localized states are developed under the application of electric field. Within a tight-binding framework we compute electronic transmission probability and average density of states using Green's function approach where the interaction parameter is treated under Hartree-Fock mean field scheme. From our analysis we find that selective transmission can be obtained by tuning injecting electron energy, and thus, the present model can be utilized as a controlled switching device.
Vences, M; Andreone, F; Glaw, F; Kosuch, J; Meyer, A; Schaefer, H-C; Veith, M
2002-08-01
The treefrog genus Boophis is one of the most species-rich endemic amphibian groups of Madagascar. It consists of species specialized to breeding in brooks (48 species) and ponds (10 species). We reconstructed the phylogeny of Boophis using 16S ribosomal DNA sequences (558 bp) from 27 species. Brook-breeders were monophyletic and probably derived from an ancestral pond-breeding lineage. Pond-breeders were paraphyletic. The disparity in diversification among pond-breeders and brook-breeders was notable among endemic Malagasy frogs, although it was not significant when considering Boophis alone. Sibling species which have different advertisement calls but are virtually indistinguishable by morphology were common among brook-breeders; genetic divergence between these species was high (modal 8% total pairwise divergence). Substitution rates in brook-breeding species were significantly higher than in pond-breeders. Speciation of pond-breeders may be hindered by their usually more synchronous reproduction and a higher vagility which enhances gene flow, while a higher potential of spatial segregation and speciation may exist along brooks.
Gary D. Grossman; Robert E. Ratajczak; C. Michael Wagner; J. Todd Petty
2010-01-01
1. We used information theoretic statistics [Akaikeâs Information Criterion (AIC)] and regression analysis in a multiple hypothesis testing approach to assess the processes capable of explaining long-term demographic variation in a lightly exploited brook trout population in Ball Creek, NC. We sampled a 100-m-long second-order site during both spring and autumn 1991â...
Market Assessment of Brooke Army Medical Center - A Strategy for Today and the Future
1985-08-01
ticipation and representation in communitywide social or sports activi- ties are invited and strongly supported by the BAMC leadership. The purpose of...or individuals with supervisory responsibility in the outpatient setting (e.g., chief of podiatry , chief of occupational therapy, chief of physical... Sports events and activities (e.g., nutrition care run and wellness fair). c. Television and newspaper health spots. II. Increase Brooke Army
Hubbard models with nearly flat bands: Ground-state ferromagnetism driven by kinetic energy
Müller, Patrick; Richter, Johannes; Derzhko, Oleg
2016-04-01
We consider the standard repulsive Hubbard model with a flat lowest-energy band for two one-dimensional lattices (diamond chain and ladder) as well as for a two-dimensional lattice (bilayer) at half filling of the flat band. The considered models do not fall in the class of Mielke-Tasaki flat-band ferromagnets, since they do not obey the connectivity conditions. However, the ground-state ferromagnetism can emerge, if the flat band becomes dispersive. To study this kinetic-energy-driven ferromagnetism we use perturbation theory and exact diagonalization of finite lattices. We find as a typical scenario that small and moderate dispersion may lead to a ferromagnetic ground state for sufficiently large on-site Hubbard repulsion U >Uc , where Uc increases monotonically with the acquired bandwidth. However, we also observe for some specific parameter cases, that (i) ferromagnetism appears at already very small Uc, (ii) ferromagnetism does not show up at all, (iii) the critical on-site repulsion Uc is a nonmonotonic function of the bandwidth, or that (iv) a critical bandwidth is needed to open the window for ground-state ferromagnetism.
FEATURES OF CULTIVATION OF BROILERS OF HUBBARD REDBRO CROSS IN FARMS FOR “ORGANIC” MEAT
Directory of Open Access Journals (Sweden)
Hakonov S. M.
2016-06-01
Full Text Available This article is devoted to studying the influence of conditions of keeping and feedings on broilers of Hubbard RedBro cross, and the quality of the received products in case of application of floor and cellular content in the conditions of a farm. It was found that when receiving a feed of its own production with the use of feed ingredients grown in farms without pesticides, recorded a statistically significant reduction in the potentially dangerous health animal substances. As compared with a factory forage therein reduced pesticide content by 14 times, mercury and arsenic is 24 times, 5 times cadmium, lead 10 times. Results of studying of economic indicators of cultivation of broilers of cross Hubbard RedBro and also chemical composition and quality of carcasses demonstrated that the essential difference between a floor and cellular condition of keeping is not established, however use of a diet on the basis of what forages promoted statistically reliable decrease in concentration of toxic metals in muscles of a bird of experienced groups. As a result it was found that use of the researched compound feed in diets of broilers raised indicators of biosafety and provided ecologically safe (“organic” meat products of poultry farming
Superconductivity, Mott-Hubbard states, and molecular orbital order in intercalated fullerides
Iwasa, Y
2003-01-01
This article reviews the current status of chemically doped fullerene superconductors and related compounds, with particular focus on Mott-Hubbard states and the role of molecular orbital degeneracy. Alkaline-earth metal fullerides produce superconductors of several kinds, all of which have states with higher valence than (C sub 6 sub 0) sup 6 sup - , where the second lowest unoccupied molecular orbital (the LUMO + 1 state) is filled. Alkali-metal-doped fullerides, on the other hand, afford superconductors only at the stoichiometry A sub 3 C sub 6 sub 0 (A denotes alkali metal) and in basically fcc structures. The metallicity and superconductivity of A sub 3 C sub 6 sub 0 compounds are destroyed either by reduction of the crystal symmetry or by change in the valence of C sub 6 sub 0. This difference is attributed to the narrower bandwidth in the A sub 3 C sub 6 sub 0 system, causing electronic instability in Jahn-Teller insulators and Mott-Hubbard insulators. The latter metal-insulator transition is driven by...
Interplay between electron correlations and quantum orders in the Hubbard model
Witczak-Kremp, William
We discuss the appearance of quantum orders in the Hubbard model for interacting electrons, at half-filling. Such phases do not have local order parameters and need to be characterized by the quantum mechanical properties of their ground state. On one hand, we study the Mott transition from a metal to a spin liquid insulator in two dimensions, of potential relevance to some layered organic compounds. The correlation-driven transition occurs at fixed filling and involves fractionalization of the electron: upon entering the insulator, a Fermi surface of neutral spinons coupled to an internal gauge field emerges. We focus on the transport properties near the quantum critical point and find that the emergent gauge uctuations play a key role in determining the universal scaling. Second, motivated by a class of three-dimensional transition metal oxides, the pyrochlore iridates, we study the interplay of non-trivial band topology and correlations. Building on the strong spin orbit coupling in these compounds, we construct a general microscopic Hubbard model and determine its mean-field phase diagram, which contains topological insulators, Weyl semimetals, axion insulators and various antiferromagnets. We also discuss the effects many-body correlations on theses phases. We close by examining a fractionalized topological insulator that combines the two main themes of the thesis: fractionalization and non-trivial band topology. Specifically, we study how the twodimensional protected surface states of a topological Mott insulator interact with a threedimensional emergent gauge field. Various correlation effects on observables are identified.
Hybrid-space density matrix renormalization group study of the doped two-dimensional Hubbard model
Ehlers, G.; White, S. R.; Noack, R. M.
2017-03-01
The performance of the density matrix renormalization group (DMRG) is strongly influenced by the choice of the local basis of the underlying physical lattice. We demonstrate that, for the two-dimensional Hubbard model, the hybrid-real-momentum-space formulation of the DMRG is computationally more efficient than the standard real-space formulation. In particular, we show that the computational cost for fixed bond dimension of the hybrid-space DMRG is approximately independent of the width of the lattice, in contrast to the real-space DMRG, for which it is proportional to the width squared. We apply the hybrid-space algorithm to calculate the ground state of the doped two-dimensional Hubbard model on cylinders of width four and six sites; at n =0.875 filling, the ground state exhibits a striped charge-density distribution with a wavelength of eight sites for both U /t =4.0 and 8.0 . We find that the strength of the charge ordering depends on U /t and on the boundary conditions. Furthermore, we investigate the magnetic ordering as well as the decay of the static spin, charge, and pair-field correlation functions.
Edge-Corrected Mean-Field Hubbard Model: Principle and Applications in 2D Materials
Directory of Open Access Journals (Sweden)
Xi Zhang
2017-05-01
Full Text Available This work reviews the current progress of tight-binding methods and the recent edge-modified mean-field Hubbard model. Undercoordinated atoms (atoms not fully coordinated exist at a high rate in nanomaterials with their impact overlooked. A quantum theory was proposed to calculate electronic structure of nanomaterials by incorporating bond order-length-strength (BOLS correlation to mean-field Hubbard model, i.e., BOLS-HM. Consistency between the BOLS-HM calculation and density functional theory (DFT calculation on 2D materials verified that (i bond contractions and potential well depression occur at the edge of graphene, phosphorene, and antimonene nanoribbons; (ii the physical origin of the band gap opening of graphene, phosphorene, and antimonene nanoribbons lays in the enhancement of edge potentials and hopping integrals due to the shorter and stronger bonds between undercoordinated atoms; (iii the band gap of 2D material nanoribbons expand as the width decreases due to the increasing under-coordination effects of edges which modulates the conductive behaviors; and (iv non-bond electrons at the edges and atomic vacancies of 2D material accompanied with the broken bond contribute to the Dirac-Fermi polaron (DFP with a local magnetic moment.
Stearns, Leigh A.; Hamilton, Gordon S.; van der Veen, C. J.; Finnegan, D. C.; O'Neel, Shad; Scheick, J. B.; Lawson, D. E.
2015-01-01
Hubbard Glacier, located in southeast Alaska, is the world's largest non-polar tidewater glacier. It has been steadily advancing since it was first mapped in 1895; occasionally, the advance creates an ice or sediment dam that blocks a tributary fjord (Russell Fiord). The sustained advance raises the probability of long-term closure in the near-future, which will strongly impact the ecosystem of Russell Fiord and the nearby community of Yakutat. Here, we examine a 43-year record of flow speeds and terminus position to understand the large-scale dynamics of Hubbard Glacier. Our long-term record shows that the rate of terminus advance has increased slightly since 1895, with the exception of a slowed advance between approximately 1972 and 1984. The short-lived closure events in 1986 and 2002 were not initiated by perturbations in ice velocity or environmental forcings, but were likely due to fluctuations in sedimentation patterns at the terminus. This study points to the significance of a coupled system where short-term velocity fluctuations and morainal shoal development control tidewater glacier terminus position.
Phase diagram of the t U2 Hamiltonian of the weak coupling Hubbard model
Yanagisawa, Takashi
2008-02-01
We determine the symmetry of Cooper pairs, on the basis of the perturbation theory in terms of the Coulomb interaction U, for the two-dimensional Hubbard model on the square lattice. The phase diagram is investigated in detail. The Hubbard model for small U is mapped on to an effective Hamiltonian with the attractive interaction using the canonical transformation: Heff = eSHe-S. The gap equation of the weak coupling formulation is solved without numerical ambiguity to determine the symmetry of Cooper pairs. The superconducting gap crucially depends on the position of the van Hove singularity. We show the phase diagram in the plane of the electron filling ne and the next nearest-neighbor transfer t'. The d-wave pairing is dominant for the square lattice in a wide range of ne and t'. The d-wave pairing is also stable for the square lattice with anisotropic t'. The three-band d-p model is also investigated, for which the d-wave pairing is stable in a wide range of ne and tpp (the transfer between neighboring oxygen atoms). In the weak coupling analysis, the second-neighbor transfer parameter -t' could not be so large so that the optimum doping rate is in the range of 0.8 < ne < 0.85.
FFLO Excitonic State in the Three-Chain Hubbard Model for Ta2NiSe5
Yamada, Takemi; Domon, Kaoru; Ōno, Yoshiaki
2016-05-01
The three-chain Hubbard model for Ta2NiSe5, known as a candidate material for an excitonic insulator, is investigated over the wide range of the energy gap D between the twofold degenerate conduction bands and the nondegenerate valence band including both semiconducting (D > 0) and semimetallic (D NiSe5 under high pressure.
Phase-separated charge-density-wave phase in the two-species extended Bose-Hubbard model
Mishra, Tapan; Sahoo, B. K.; Pai, Ramesh V.
We study the quantum phase transitions in a two component Bose mixture in a one-dimensional optical lattice. The calculations have been performed in the framework of the extended Bose-Hubbard model using the finite size density matrix renormalization group method. We obtain different phase
Corboz, P.
2016-01-01
An infinite projected entangled-pair state (iPEPS) is a variational tensor network ansatz for two-dimensional wave functions in the thermodynamic limit where the accuracy can be systematically controlled by the bond dimension D. We show that for the doped Hubbard model in the strongly correlated reg
Finite-size effects for the gap in the excitation spectrum of the one-dimensional Hubbard model
Colomé-Tatché, M.; Matveenko, S.I.; Shlyapnikov, G.V.
2010-01-01
We study finite-size effects for the gap of the quasiparticle excitation spectrum in the weakly interacting regime one-dimensional Hubbard model with on-site attraction. Two types of corrections to the result of the thermodynamic limit are obtained. Aside from a power law (conformal) correction due
Finite-size effects for the gap in the excitation spectrum of the one-dimensional Hubbard model
Colomé-Tatché, M.; Matveenko, S.I.; Shlyapnikov, G.V.
2010-01-01
We study finite-size effects for the gap of the quasiparticle excitation spectrum in the weakly interacting regime one-dimensional Hubbard model with on-site attraction. Two types of corrections to the result of the thermodynamic limit are obtained. Aside from a power law (conformal) correction due
Conductivite dans le modele de Hubbard bi-dimensionnel a faible couplage
Bergeron, Dominic
Le modele de Hubbard bi-dimensionnel (2D) est souvent considere comme le modele minimal pour les supraconducteurs a haute temperature critique a base d'oxyde de cuivre (SCHT). Sur un reseau carre, ce modele possede les phases qui sont communes a tous les SCHT, la phase antiferromagnetique, la phase supraconductrice et la phase dite du pseudogap. Il n'a pas de solution exacte, toutefois, plusieurs methodes approximatives permettent d'etudier ses proprietes de facon numerique. Les proprietes optiques et de transport sont bien connues dans les SCHT et sont donc de bonne candidates pour valider un modele theorique et aider a comprendre mieux la physique de ces materiaux. La presente these porte sur le calcul de ces proprietes pour le modele de Hubbard 2D a couplage faible ou intermediaire. La methode de calcul utilisee est l'approche auto-coherente a deux particules (ACDP), qui est non-perturbative et inclue l'effet des fluctuations de spin et de charge a toutes les longueurs d'onde. La derivation complete de l'expression de la conductivite dans l'approche ACDP est presentee. Cette expression contient ce qu'on appelle les corrections de vertex, qui tiennent compte des correlations entre quasi-particules. Pour rendre possible le calcul numerique de ces corrections, des algorithmes utilisant, entre autres, des transformees de Fourier rapides et des splines cubiques sont developpes. Les calculs sont faits pour le reseau carre avec sauts aux plus proches voisins autour du point critique antiferromagnetique. Aux dopages plus faibles que le point critique, la conductivite optique presente une bosse dans l'infrarouge moyen a basse temperature, tel qu'observe dans plusieurs SCHT. Dans la resistivite en fonction de la temperature, on trouve un comportement isolant dans le pseudogap lorsque les corrections de vertex sont negligees et metallique lorsqu'elles sont prises en compte. Pres du point critique, la resistivite est lineaire en T a basse temperature et devient
Energy Technology Data Exchange (ETDEWEB)
Catherine L. Hanks
2008-12-31
Naturally occurring fractures can play a key role in the evolution and producibility of a hydrocarbon accumulation. Understanding the evolution of fractures in the Brooks Range/Colville basin system of northern Alaska is critical to developing a better working model of the hydrocarbon potential of the region. This study addressed this problem by collecting detailed and regional data on fracture distribution and character, structural geometry, temperature, the timing of deformation along the Brooks Range rangefront and adjacent parts of the Colville basin, and the in situ stress distribution within the Colville basin. This new and existing data then were used to develop a model of how fractures evolved in northern Alaska, both spatially and temporally. The results of the study indicate that fractures formed episodically throughout the evolution of northern Alaska, due to a variety of mechanisms. Four distinct fracture sets were observed. The earliest fractures formed in deep parts of the Colville basin and in the underlying Ellesmerian sequence rocks as these rocks experienced compression associated with the growing Brooks Range fold-and-thrust belt. The orientation of these deep basin fractures was controlled by the maximum in situ horizontal stress in the basin at the time of their formation, which was perpendicular to the active Brooks Range thrust front. This orientation stayed consistently NS-striking for most of the early history of the Brooks Range and Colville basin, but changed to NW-striking with the development of the northeastern Brooks Range during the early Tertiary. Subsequent incorporation of these rocks into the fold-and-thrust belt resulted in overprinting of these deep basin fractures by fractures caused by thrusting and related folding. The youngest fractures developed as rocks were uplifted and exposed. While this general order of fracturing remains consistent across the Brooks Range and adjacent Colville basin, the absolute age at any one
Nynca, J; Dietrich, G J; Dobosz, S; Zalewski, T; Ciereszko, A
2015-01-15
The aim of this study was to test the influence of postthaw storage time on sperm motility parameters of brook trout (n = 9). Furthermore, we examined the effect of sperm-to-egg ratios of 300,000:1 and 600,000:1 on fertility of postthaw, cryopreserved, brook trout sperm. The application of a cryopreservation procedure produced very high postthaw sperm motility (56.8 ± 4.0%). The cryopreserved sperm of brook trout could be stored up to 60 minutes without loss of the percentage of sperm motility (52.0 ± 9.0%). The fertilization capacity of brook trout postthaw sperm was comparable with the fertilization rate of fresh semen at a sperm-to-egg ratio as low as 300,000:1 (42.4 ± 14.0% and 36.5 ± 11.0% for eyed and hatched stages, respectively). The possibility of postthaw semen storage for the prolonged time and the obtainment of high fertilization rate at low sperm-to-egg ratio can lead to the significant improvement of brook trout semen cryopreservation procedure.
Navrátil, Tomas; Norton, Stephen A; Fernandez, Ivan J; Nelson, Sarah J
2010-12-01
Mean annual concentration of SO4(-2) in wet-only deposition has decreased between 1988 and 2006 at the paired watershed study at Bear Brook Watershed in Maine, USA (BBWM) due to substantially decreased emissions of SO(2). Emissions of NO(x) have not changed substantially, but deposition has declined slightly at BBWM. Base cations, NH4+, and Cl(-) concentrations were largely unchanged, with small irregular changes of <1 μeq L(-1) per year from 1988 to 2006. Precipitation chemistry, hydrology, vegetation, and temperature drive seasonal stream chemistry. Low flow periods were typical in June-October, with relatively greater contributions of deeper flow solutions with higher pH; higher concentrations of acid-neutralizing capacity, Si, and non-marine Na; and low concentrations of inorganic Al. High flow periods during November-May were typically dominated by solutions following shallow flow paths, which were characterized by lower pH and higher Al and DOC concentrations. Biological activity strongly controlled NO3- and K(+). They were depressed during the growing season and elevated in the fall. Since 1987, East Bear Brook (EB), the reference stream, has been slowly responding to reduced but still elevated acid deposition. Calcium and Mg have declined fairly steadily and faster than SO4(-2), with consequent acidification (lower pH and higher inorganic Al). Eighteen years of experimental treatment with (NH(4))(2)SO(4) enhanced acidification of West Bear Brook's (WB) watershed. Despite the manipulation, NH4+ concentration remained below detection limits at WB, while leaching of NO3- increased. The seasonal pattern for NO3- concentrations in WB, however, remained similar to EB. Mean monthly concentrations of SO4(-2) have increased in WB since 1989, initially only during periods of high flow, but gradually also during base flow. Increases in mean monthly concentrations of Ca(2+), Mg(2+), and K(+) due to the manipulation occurred from 1989 until about 1995, during the
Exact many-electron ground states on the diamond Hubbard chain
Gulacsi, Zsolt; Kampf, Arno; Vollhardt, Dieter
2008-03-01
Exact ground states of interacting electrons on the diamond Hubbard chain in a magnetic field are constructed which exhibit a wide range of properties such as flat-band ferromagnetism, correlation induced metallic, half-metallic, or insulating behavior [1]. The properties of these ground states can be tuned by changing the magnetic flux, local potentials, or electron density.The results show that the studied simple one-dimensional structure displays remarkably complex physical properties. The virtue of tuning different ground states through external parameters points to new possibilities for the design of electronic devices which can switch between insulating or conducting and nonmagnetic or (fully or partially spin polarized) ferromagnetic states, open new routes for the design of spin-valve devices and gate induced ferromagnetism. [1] Z. Gulacsi, A. Kampf, D. Vollhardt, Phys. Rev. Lett. 99, 026404(2007).
Superconducting phase and pairing fluctuations in the half-filled two-dimensional Hubbard model.
Sentef, Michael; Werner, Philipp; Gull, Emanuel; Kampf, Arno P
2011-09-16
The two-dimensional Hubbard model exhibits superconductivity with d-wave symmetry even at half-filling in the presence of a next-nearest neighbor hopping. Using plaquette cluster dynamical mean-field theory with a continuous-time quantum Monte Carlo impurity solver, we reveal the non-Fermi liquid character of the metallic phase in proximity to the superconducting state. Specifically, the low-frequency scattering rate for momenta near (π, 0) varies nonmonotonically at low temperatures, and the dc conductivity is T linear at elevated temperatures with an upturn upon cooling. Evidence is provided that pairing fluctuations dominate the normal-conducting state even considerably above the superconducting transition temperature.
Nonequilibrium dynamical mean-field study of the nonthermal fixed point in the Hubbard model
Tsuji, Naoto; Eckstein, Martin; Werner, Philipp
2014-03-01
A fundamental question of whether and how an isolated quantum many-body system thermalizes has been posed and attracted broad interest since its ideal realization using cold atomic gases. In particular, it has been indicated by various theoretical studies that the system does not immediately thermalize but often shows ``prethermalization'' as a quasi-stationary state, where local observables quickly arrive at the thermal values while the full momentum distribution stays nonthermal for long time. Here we study the thermalization process for the fermionic Hubbard model in the presence of the antiferromagnetic long-range order. Time evolution is obtained by the nonequilibrium dynamical mean-field theory. Due to classical fluctuations, prethermalization is prevented, and the transient dynamics is governed by a nonthermal fixed point, which we discuss belongs to a universality class distinct from the conventional Ginzburg-Landau theory.
A family of affine quantum group invariant integrable extensions of the Hubbard Hamiltonian
Energy Technology Data Exchange (ETDEWEB)
Avakyan, A. [Erevanskij Fizicheskij Inst., Erevan (Armenia); Hakobyan, T. [Erevanskij Fizicheskij Inst., Erevan (Armenia); Sedrakyan, A. [Erevanskij Fizicheskij Inst., Erevan (Armenia)
1997-04-21
We construct a family of spin chain Hamiltonians, which have the affine quantum group symmetry U{sub q}g. Their eigenvalues coincide with the eigenvalues of the usual spin chain Hamiltonians, but have the degeneracy of levels, corresponding to the affine U{sub q}g. The space of states of these spin chains is formed by the tensor product of the fully reducible representations of the quantum group. The fermionic representations of the constructed spin chain Hamiltonians show that we have obtained new extensions of the Hubbard Hamiltonians. All of them are integrable and have the affine quantum group symmetry. The exact ground state of such type of model is presented, exhibiting superconducting behavior via the {eta}-pairing mechanism. (orig.).
Mott transition in the multi-band Hubbard model in infinite dimensions
Energy Technology Data Exchange (ETDEWEB)
Ono, Yoshiaki; Bulla, Ralf; Potthoff, Michael
2003-05-01
The Mott metal-insulator transition in the multi-band Hubbard model in infinite dimensions is studied by using the linearized dynamical mean-field theory. The critical interaction U{sub c} is obtained analytically. For the symmetric case and for orbital degeneracy M we find U{sub c}=(4M+2){radical}L{sub 2} where L{sub 2} is the second moment of the non-interacting density of states. We also derive an analytical expression for the discontinuity of the chemical potential {mu}(n) at the filling n=M for U>U{sub c}. The findings are in good agreement with numerical results obtained from the exact diagonalization method.
Zhao, Hongbo; Engelbrecht, Jan R.
2000-03-01
At the Mean Field level (G. Murthy and R. Shankar, J. Phys. Condens. Matter, 7) (1995), the frustration due to an external field first makes the uniform BCS ground state unstable to an incommensurate (qne0) superconducting state and then to a spin-polarized Fermi Liquid state. Our interest is how fluctuations modify this picture, as well as the normal state of this system which has a quantum critical point. We use the Fluctuation-Exchange Approximation for the 2D Attractive Hubbard Model, to study this system beyond the Mean-Field level. Earlier work in zero field has shown that this numerical method successfully captures the critical scaling of the KT superconducting transition upon cooling in the normal state. Here we investigate how the pair-breaking external field modifies this picture, and the development of incommensurate pairing.
Excitons in the one-dimensional Hubbard model: a real-time study.
Al-Hassanieh, K A; Reboredo, F A; Feiguin, A E; González, I; Dagotto, E
2008-04-25
We study the real-time dynamics of a hole and doubly occupied site pair, namely, a holon and a doublon, in a 1D Hubbard insulator with on-site and nearest-neighbor Coulomb repulsion. Our analysis shows that the pair is long-lived and the expected decay mechanism to underlying spin excitations is actually inefficient. For a nonzero intersite Coulomb repulsion, we observe that part of the wave function remains in a bound state. Our study also provides insight on the holon-doublon propagation in real space. Because of the one-dimensional nature of the problem, these particles move in opposite directions even in the absence of an applied electric field. The potential relevance of our results to solar cell applications is discussed.
Low quasiparticle coherence temperature in the one-band Hubbard model: A slave-boson approach
Mezio, Alejandro; McKenzie, Ross H.
2017-07-01
We use the Kotliar-Ruckenstein slave-boson formalism to study the temperature dependence of paramagnetic phases of the one-band Hubbard model for a variety of band structures. We calculate the Fermi liquid quasiparticle spectral weight Z and identify the temperature at which it decreases significantly to a crossover to a bad metal region. Near the Mott metal-insulator transition, this coherence temperature Tcoh is much lower than the Fermi temperature of the uncorrelated Fermi gas, as is observed in a broad range of strongly correlated electron materials. After a proper rescaling of temperature and interaction, we find a universal behavior that is independent of the band structure of the system. We obtain the temperature-interaction phase diagram as function of doping, and we compare the temperature dependence of the double occupancy, entropy, and charge compressibility with previous results obtained with dynamical mean-field theory. We analyze the stability of the method by calculating the charge compressibility.
Off-site interaction effect in the Extended Hubbard Model with the SCRPA method
Energy Technology Data Exchange (ETDEWEB)
Harir, S [Laboratoire de Physique de la Matiere Condensee, Faculte des Sciences Ben M' Sik, Universite Hassan II-Mohammedia Casablanca (Morocco); Bennai, M [Laboratoire de Physique de la Matiere Condensee, Faculte des Sciences Ben M' Sik, Universite Hassan II-Mohammedia Casablanca (Morocco); Boughaleb, Y [Laboratoire de Physique de la Matiere Condensee, Faculte des Sciences Ben M' Sik, Universite Hassan II-Mohammedia Casablanca (Morocco)
2007-10-15
The self consistent random phase approximation (SCRPA) and a direct analytical (DA) method are proposed to solve the Extended Hubbard Model (EHM) in one dimension (1D). We have considered an EHM including on-site and off-site interactions for closed chains in 1D with periodic boundary conditions. The comparison of the SCRPA results with the ones obtained by a DA approach shows that the SCRPA treats the problem of these closed chains in a rigorous manner. The analysis of the nearest-neighbour repulsion effect on the dynamics of our closed chains shows that this repulsive interaction between the electrons of the neighbouring atoms induces supplementary conductivity, since, the SCRPA energygap vanishes when these closed chains are governed by a strong repulsive on-site interaction and intermediate nearest-neighbour repulsion.
Spin-spin interaction effect in 2D Extended Hubbard Model
Zouhair, A.; Harir, S.; Bennai, M.; Boughaleb, Y.
2014-09-01
Using an exact diagonlization for finite square lattice and taking into account the periodic boundary conditions in the two directions, we study the spin-spin interaction effect on some local electronic properties for antiferromagnetic correlated electrons system. We have considered an Extended Hubbard Model (EHM) including on-site coulomb interaction energy U and spin-spin interaction term J. The diagonlization of this 2D EHM model allows us to study J effect on some local properties for finite square lattice. The analysis of the obtained results shows that the introduction of spin-spin interaction induces a supplementary conductivity for antiferromagnetic correlated electrons system, even in the strong on-site interaction regime.
Off-site interaction effect in the Extended Hubbard Model with the SCRPA method
Harir, S.; Bennai, M.; Boughaleb, Y.
2007-10-01
The self consistent random phase approximation (SCRPA) and a direct analytical (DA) method are proposed to solve the Extended Hubbard Model (EHM) in one dimension (1D). We have considered an EHM including on-site and off-site interactions for closed chains in 1D with periodic boundary conditions. The comparison of the SCRPA results with the ones obtained by a DA approach shows that the SCRPA treats the problem of these closed chains in a rigorous manner. The analysis of the nearest-neighbour repulsion effect on the dynamics of our closed chains shows that this repulsive interaction between the electrons of the neighbouring atoms induces supplementary conductivity, since, the SCRPA energygap vanishes when these closed chains are governed by a strong repulsive on-site interaction and intermediate nearest-neighbour repulsion.
One-step approach to ARPES from strongly correlated solids: A Mott-Hubbard system
Kuzian, R. O.; Krasovskii, E. E.
2016-09-01
An expression is derived for angle-resolved photocurrent from a semi-infinite correlated system. Within the sudden approximation, the photocurrent is proportional to the spectral function of a one-particle two-time retarded Green's function G of an operator that creates an electron in a special quantum state χ localized at the surface. For a system described by a many-body single-band model, we present an analytical expression that relates the Green's function G with the Green's function of an infinite crystal Gb ,k(ω ) in Wannier representation. The role of final states and of the crystal surface is analyzed for a model Green's function of the infinite crystal with a three-peak spectral function typical of a Mott-Hubbard metal. The momentum dependences of both the quasiparticle pole position and the spectral weight of the incoherent band manifest themselves in the shape of the photocurrent energy distribution curve.
Emulating the one-dimensional Fermi-Hubbard model by a double chain of qubits
Reiner, Jan-Michael; Marthaler, Michael; Braumüller, Jochen; Weides, Martin; Schön, Gerd
2016-09-01
The Jordan-Wigner transformation maps a one-dimensional (1D) spin-1 /2 system onto a fermionic model without spin degree of freedom. A double chain of quantum bits with X X and Z Z couplings of neighboring qubits along and between the chains, respectively, can be mapped on a spin-full 1D Fermi-Hubbard model. The qubit system can thus be used to emulate the quantum properties of this model. We analyze physical implementations of such analog quantum simulators, including one based on transmon qubits, where the Z Z interaction arises due to an inductive coupling and the X X interaction due to a capacitive interaction. We propose protocols to gain confidence in the results of the simulation through measurements of local operators.
Bose-Hubbard models with staggered flux: Quantum phases, collective excitation, and tricriticality
Yao, Juan; Zhang, Shizhong
2014-08-01
We study the quantum phases of a Bose-Hubbard model with staggered magnetic flux in two dimensions, as was realized recently [M. Aidelsburger, M. Atala, M. Lohse, J. T. Barreiro, B. Paredes, and I. Bloch, Phys. Rev. Lett. 107, 255301 (2011), 10.1103/PhysRevLett.107.255301]. Within mean-field theory, we show how the structure of the condensates evolves from the weak- to the strong-coupling limit, exhibiting a tricritical point at the Mott-superfluid transition. Nontrivial topological structures (Dirac points) in the quasiparticle (hole) excitations in the Mott state are found within random phase approximation and we discuss how interaction modifies their structures. The excitation gap in the Mott state closes at different k points when approaching the superfluid states, which is consistent with the findings of mean-field theory.
Wu, Wei; Ferrero, Michel; Georges, Antoine; Kozik, Evgeny
2017-07-01
We introduce a method for summing Feynman's perturbation series based on diagrammatic Monte Carlo that significantly improves its convergence properties. This allows us to investigate in a controllable manner the pseudogap regime of the Hubbard model and to study the nodal/antinodal dichotomy at low doping and intermediate coupling. Marked differences from the weak-coupling scenario are manifest, such as a higher degree of incoherence at the antinodes than at the "hot spots". Our results show that the pseudogap and reduction of quasiparticle coherence at the antinode is due to antiferromagnetic spin correlations centered around the commensurate (π ,π ) wave vector. In contrast, the dominant source of scattering at the node is associated with incommensurate momentum transfer. Umklapp scattering is found to play a key role in the nodal/antinodal dichotomy.
Moradi Kurdestany, Jamshid; Satpathy, Sashi
Motivated by the recent progress in understanding of Mott insulators away from half filling, observed in many perovskite oxides, we study the metal-insulator transition in the Hubbard-Holstein model, which contains both the Coulomb and the electron-lattice (Jahn Teller) interactions by using the Gutzwiller variational method. We find that strong electron-lattice Interaction leads to phase separation, which however can be frustrated due to the long-range Coulomb interaction, resulting in a mixed phase consisting of puddles of metallic phases embedded in an insulating matrix. When the dopant concentration exceeds a threshold value xc , the metallic part forms a percolating network leading to metallic conduction. Depending on the strength of the electron-lattice interaction, xc can be of the order of 0.05 - 0.20 or so, which is the typical value observed in the perovskites.
Gutzwiller wave function for finite systems: superconductivity in the Hubbard model
Tomski, Andrzej; Kaczmarczyk, Jan
2016-05-01
We study the superconducting phase of the Hubbard model using the Gutzwiller variational wave function (GWF) and the recently proposed diagrammatic expansion technique (DE-GWF). The DE-GWF method works on the level of the full GWF and in the thermodynamic limit. Here, we consider a finite-size system to study the accuracy of the results as a function of the system size (which is practically unrestricted). We show that the finite-size scaling used, e.g. in the variational Monte Carlo method can lead to significant, uncontrolled errors. The presented research is the first step towards applying the DE-GWF method in studies of inhomogeneous situations, including systems with impurities, defects, inhomogeneous phases, or disorder.
Analytical diagonalization study of a two-orbital Hubbard model on a two-site molecule
Energy Technology Data Exchange (ETDEWEB)
Amendola, Maria Emilia, E-mail: canio@sa.infn.it [Dipartimento di Matematica, Università di Salerno, I-84084 Fisciano (Italy); Romano, Alfonso [CNR-SPIN, I-84084 Fisciano (Italy); Dipartimento di Fisica “E. R. Caianiello”, Università di Salerno, I-84084 Fisciano (Italy); Noce, Canio, E-mail: canio@sa.infn.it [CNR-SPIN, I-84084 Fisciano (Italy); Dipartimento di Fisica “E. R. Caianiello”, Università di Salerno, I-84084 Fisciano (Italy)
2015-12-15
We present the exact solution of a two-orbital Hubbard model on a two-site molecule for arbitrary electron filling and arbitrary interaction couplings. The knowledge of the many-particle spectrum, determined via a diagonalization procedure performed by fully taking into account the symmetry properties of the model, has been used to investigate the temperature dependence of charge, spin and orbital response functions as well as of the intra- and inter-orbital on-site occupations. We point out that this study may allow easy access to many interesting features of the model and may serve as a reference tool for various numerical or perturbation methods dealing with complex correlated electron models defined on a lattice, in particular in the case in which strong local interactions dominate over kinetic effects.
Schüler, M; Rösner, M; Wehling, T O; Lichtenstein, A I; Katsnelson, M I
2013-07-19
To understand how nonlocal Coulomb interactions affect the phase diagram of correlated electron materials, we report on a method to approximate a correlated lattice model with nonlocal interactions by an effective Hubbard model with on-site interactions U(*) only. The effective model is defined by the Peierls-Feynman-Bogoliubov variational principle. We find that the local part of the interaction U is reduced according to U(*)=U-V[over ¯], where V[over ¯] is a weighted average of nonlocal interactions. For graphene, silicene, and benzene we show that the nonlocal Coulomb interaction can decrease the effective local interaction by more than a factor of 2 in a wide doping range.
GREEN'S FUNCTIONS OF INFINITE-U ASYMMETRIC HUBBARD MODEL: FALICOV-KIMBALL LIMIT
Directory of Open Access Journals (Sweden)
I.V.Stasyuk
2003-01-01
Full Text Available The asymmetric Hubbard model is used in investigating the lattice gas of the moving particles of two types. The model is considered within the dynamical mean-field method. The effective single-site problem is formulated in terms of the auxiliary Fermi-field. To solve the problem an approximate analytical method based on the irreducible Green's function technique is used. This approach is tested on the Falicov-Kimball limit (when the mobility of ions of either type is infinitesimally small of the infinite-U case of the model considered. The dependence of chemical potentials on concentration is calculated using the one-particle Green's functions, and different approximations are compared with the exact results obtained thermodynamically. The densities of states of localized particles are obtained for different temperatures and particle concentrations. The phase transitions are investigated for the case of the Falicov-Kimball limit in different thermodynamic regimes.
Czarnik, Piotr; Rams, Marek M.; Dziarmaga, Jacek
2016-12-01
A Gibbs operator e-β H for a two-dimensional (2D) lattice system with a Hamiltonian H can be represented by a 3D tensor network, with the third dimension being the imaginary time (inverse temperature) β . Coarse graining the network along β results in a 2D projected entangled-pair operator (PEPO) with a finite bond dimension. The coarse graining is performed by a tree tensor network of isometries. They are optimized variationally to maximize the accuracy of the PEPO as a representation of the 2D thermal state e-β H. The algorithm is applied to the two-dimensional Hubbard model on an infinite square lattice. Benchmark results at finite temperature are obtained that are consistent with the best cluster dynamical mean-field theory and power-series expansion in the regime of parameters where they yield mutually consistent results.
Spectral properties of the one-dimensional Hubbard model: cluster dynamical mean-field approaches
Go, Ara; Jeon, Gun Sang
2011-03-01
We investigate static and dynamic properties of the one-dimensional Hubbard model using cluster extensions of the dynamical mean-field theory. It is shown that the two different extensions, the cellular dynamical mean-field theory and the dynamic cluster approximation, yield the ground-state properties which are qualitatively in good agreement with each other. We compare the results with the Bethe ansatz results to check the accuracy of the calculation with finite sizes of clusters. We also analyze the spectral properties of the model with the focus on the spin-charge separation and discuss the dependency on the cluster size in the two approaches. This research was supported by Basic Science Research Program through the National Research Foundation of Korea(NRF) funded by the Ministry of Education, Science and Technology(2010-0010937).
Algebraic geometry methods associated to the one-dimensional Hubbard model
Energy Technology Data Exchange (ETDEWEB)
Martins, M.J., E-mail: martins@df.ufscar.br
2016-06-15
In this paper we study the covering vertex model of the one-dimensional Hubbard Hamiltonian constructed by Shastry in the realm of algebraic geometry. We show that the Lax operator sits in a genus one curve which is not isomorphic but only isogenous to the curve suitable for the AdS/CFT context. We provide an uniformization of the Lax operator in terms of ratios of theta functions allowing us to establish relativistic like properties such as crossing and unitarity. We show that the respective R-matrix weights lie on an Abelian surface being birational to the product of two elliptic curves with distinct J-invariants. One of the curves is isomorphic to that of the Lax operator but the other is solely fourfold isogenous. These results clarify the reason the R-matrix can not be written using only difference of spectral parameters of the Lax operator.
Quantum criticality in the 2D Hubbard: from weak to strong coupling
Galanakis, Dimitrios; Mikelsons, Karlis; Khatami, Ehsan; Zhang, Peng; Xu, Zhaoxin; Moreno, Juana; Jarrell, Mark
2010-03-01
We study the phase diagram of the two-dimensional Hubbard model in the vicinity of the quantum critical point which separates the fermi liquid from the pseudogap region. We use the Dynamical Cluster Approximation (DCA) in conjunction with the weak-coupling continuous time quantum Monte Carlo (CTQMC) cluster solver. We measure the filling nc and the density of states at the critical point as a function of the Coulomb interaction U. We observe a change in behavior when the Coulomb interaction is of the order of the bandwidth. We also evaluate the temperature range in which the system is under the influence of the quantum critical point and compare it with the effective spin coupling Jeff. We discuss the consistency of these results with various mechanisms of quantum criticality. This research is supported by NSF DMR-0706379 and OISE-0952300.
Two fermions in a double well: exploring a fundamental building block of the Hubbard model.
Murmann, Simon; Bergschneider, Andrea; Klinkhamer, Vincent M; Zürn, Gerhard; Lompe, Thomas; Jochim, Selim
2015-02-27
We have prepared two ultracold fermionic atoms in an isolated double-well potential and obtained full control over the quantum state of this system. In particular, we can independently control the interaction strength between the particles, their tunneling rate between the wells and the tilt of the potential. By introducing repulsive (attractive) interparticle interactions we have realized the two-particle analog of a Mott-insulating (charge-density-wave) state. We have also spectroscopically observed how second-order tunneling affects the energy of the system. This work realizes the first step of a bottom-up approach to deterministically create a single-site addressable realization of a ground-state Fermi-Hubbard system.
Nonequilibrium dynamics of the Bose-Hubbard model: a projection-operator approach.
Trefzger, C; Sengupta, K
2011-03-04
We study the phase diagram and nonequilibrium dynamics involving ramp of the hopping amplitude J(t)=Jt/τ with ramp time τ of the Bose-Hubbard model at zero temperature using a projection-operator formalism which allows us to incorporate the effects of quantum fluctuations beyond mean-field approximations in the strong-coupling regime. Our formalism yields a phase diagram which provides a near exact match with quantum Monte Carlo results in three dimensions. We also compute the residual energy Q, the superfluid order parameter Δ(t), the equal-time order parameter correlation function C(t), and the wave function overlap F which yields the defect formation probability P during nonequilibrium dynamics of the model. We find that Q, F, and P do not exhibit the expected universal scaling. We explain this absence of universality and show that our results compare well with recent experiments.
Topological phase transitions and universality in the Haldane-Hubbard model
Giuliani, Alessandro; Jauslin, Ian; Mastropietro, Vieri; Porta, Marcello
2016-11-01
We study the Haldane-Hubbard model by exact renormalization group techniques. We analytically construct the topological phase diagram, for weak interactions. We predict that many-body interactions induce a shift of the transition line: in particular, repulsive interactions enlarge the topologically nontrivial region. The presence of new intermediate phases, absent in the noninteracting case, is rigorously excluded at weak coupling. Despite the nontrivial renormalization of the wave function and of the Fermi velocity, the conductivity is universal: at the renormalized critical line, both the discontinuity of the transverse conductivity and the longitudinal conductivity are independent of the interaction, thanks to remarkable cancellations due to lattice Ward identities. In contrast to the quantization of the transverse conductivity, the universality of the longitudinal conductivity cannot be explained via topological arguments.
Fishery survey and related limnological conditions of Williams Lake, Hubbard County, Minnesota
Taylor, W.W.; LaBaugh, J.W.; Freeberg, M.H.; Dowling, D.C.
1985-01-01
Bluegill (Lepomis macrochirus), pumpkinseed sunfish (Lepomis gibbosus), largemouth bass (Micropterus salmoides), yellow perch (Perca flavescens) rock bass (Amploplites rupestris), black crappie (Pomozis nigromaculatus), and northern pike (Esox lucius) were found in Williams Lake, Hubbard County, Minnesota, during a fishery survey of the lake in late August 1982. The most abundant fish were the bluegills. These fish live in the large littoral zone of the lake; this zone underlies 55% of the surface area of the lake. The most ubiquitous benthic invertebrate in the littoral zone (amphipods) and the most abundant benthic invertebrate (chironomid larvae) were major food sources for the bluegill. Other organisms found in the stomach contents of fish collected in this survey were zooplankton, gastropods, Diptera larvae, odonates, terrestrial insects, and other fish. Daphnia were the only zooplankters of a diverse plankton community that were found in stomach contents. The abundance of fish other than bluegill was typical for a system in which northern pike is the major predator.
Effect of interactions, disorder and magnetic field in the Hubbard model in two dimensions
Indian Academy of Sciences (India)
N Trivedi; P J H Denteneer; D Heidarian; R T Scaletar
2005-06-01
The effects of both interactions and Zeeman magnetic field in disordered electronic systems are explored in the Hubbard model on a square lattice. We investigate the thermodynamic (density, magnetization, density of states) and transport (conductivity) properties using determinantal quantum Monte Carlo and inhomogeneous Hartree Fock techniques. We find that at half filling there is a novel metallic phase at intermediate disorder that is sandwiched between a Mott insulator and an Anderson insulator. The metallic phase is highly inhomogeneous and coexists with antiferromagnetic long-range order. At quarter filling also the combined effects of disorder and interactions produce a conducting state which can be destroyed by applying a Zeeman field, resulting in a magnetic field-driven transition. We discuss the implication of our results for experiments.
Phase Diagram of the Frustrated Square-Lattice Hubbard Model: Variational Cluster Approach
Misumi, Kazuma; Kaneko, Tatsuya; Ohta, Yukinori
2016-06-01
The variational cluster approximation is used to study the frustrated Hubbard model at half filling defined on the two-dimensional square lattice with anisotropic next-nearest-neighbor hopping parameters. We calculate the ground-state phase diagrams of the model in a wide parameter space for a variety of lattice geometries, including square, crossed-square, and triangular lattices. We examine the Mott metal-insulator transition and show that, in the Mott insulating phase, magnetic phases with Néel, collinear, and spiral orders appear in relevant parameter regions, and in an intermediate region between these phases, a nonmagnetic insulating phase caused by the quantum fluctuations in the geometrically frustrated spin degrees of freedom emerges.
Quantum disordered insulating phase in the frustrated cubic-lattice Hubbard model
Laubach, Manuel; Joshi, Darshan G.; Reuther, Johannes; Thomale, Ronny; Vojta, Matthias; Rachel, Stephan
2016-01-01
In the quest for quantum spin liquids in three spatial dimensions (3D), we study the half-filled Hubbard model on the simple cubic lattice with hopping processes up to third neighbors. Employing the variational cluster approach (VCA), we determine the zero-temperature phase diagram: In addition to a paramagnetic metal at small interaction strength U and various antiferromagnetic insulators at large U , we find an intermediate-U antiferromagnetic metal. Most interestingly, we also identify a nonmagnetic insulating region, extending from intermediate to strong U . Using VCA results in the large-U limit, we establish the phase diagram of the corresponding J1-J2-J3 Heisenberg model. This is qualitatively confirmed—including the nonmagnetic region—using spin-wave theory. Further analysis reveals a striking similarity to the behavior of the J1-J2 square-lattice Heisenberg model, suggesting that the nonmagnetic region may host a 3D spin-liquid phase.
Revealing hidden antiferromagnetic correlations in doped Hubbard chains via string correlators
Hilker, Timon A.; Salomon, Guillaume; Grusdt, Fabian; Omran, Ahmed; Boll, Martin; Demler, Eugene; Bloch, Immanuel; Gross, Christian
2017-08-01
Topological phases, like the Haldane phase in spin-1 chains, defy characterization through local order parameters. Instead, nonlocal string order parameters can be employed to reveal their hidden order. Similar diluted magnetic correlations appear in doped one-dimensional lattice systems owing to the phenomenon of spin-charge separation. Here we report on the direct observation of such hidden magnetic correlations via quantum gas microscopy of hole-doped ultracold Fermi-Hubbard chains. The measurement of nonlocal spin-density correlation functions reveals a hidden finite-range antiferromagnetic order, a direct consequence of spin-charge separation. Our technique, which measures nonlocal order directly, can be readily extended to higher dimensions to study the complex interplay between magnetic order and density fluctuations.
Yang, H. F.; Fan, C. C.; Liu, Z. T.; Yao, Q.; Li, M. Y.; Liu, J. S.; Jiang, M. H.; Shen, D. W.
2016-09-01
In the prototypical 4 d system (Sr ,Ca ) RuO3 , the degree and origin of electron correlations, and how they correlate with physical properties, still remain elusive, though extensive studies have been performed. In this work we present a comparative electronic structure study of high-quality epitaxial CaRuO3 and SrRuO3 thin films, by means of reactive molecular beam epitaxy and in situ angle-resolved photoemission spectroscopy. We found that while SrRuO3 possesses sharp features signaling the Fermi liquid state, the isostructural CaRuO3 exhibits broad features and its spectral weight is markedly transferred from the Fermi level to -1.2 eV forming a "hump" structure which resembles the Mott-Hubbard system (Sr ,Ca ) VO3 . We suggest that this hump is the precursor of the lower Hubbard band, and the U /W (U and W represent the on-site Coulomb interactions and bandwidth, respectively) of our CaRuO3 thin film is much larger than that of SrRuO3. In addition, we discuss the origin of electron correlations as well as the ferromagnetism in SrRuO3 which is absent in CaRuO3. Our findings put constraints on future studies, and also show that perovskite ruthenates are indeed an experimentally tunable system for the study of electron correlations.
Filling-dependent doublon dynamics in the one-dimensional Hubbard model
Rausch, Roman; Potthoff, Michael
2017-01-01
The fate of a local two-hole doublon excitation in the one-dimensional Fermi-Hubbard model is systematically studied for strong Hubbard interaction U in the entire filling range using the density-matrix renormalization group (DMRG) and the Bethe ansatz. For strong U , two holes at the same site form a compound object whose decay is impeded by the lack of phase space. Still, a partial decay is possible on an extremely short time scale where phase-space arguments do not yet apply. We argue that the initial decay and the resulting intermediate state are relevant for experiments performed with ultracold atoms loaded into an optical lattice as well as for (time-resolved) CVV Auger-electron spectroscopy. The detailed discussion comprises the mixed ballistic-diffusive real-time propagation of the doublon through the lattice, its partial decay on the short time scale as a function of filling and interaction strength, as well as the analysis of the decay products, which are metastable on the intermediate time scale that is numerically accessible and which show up in the two-hole excitation (Auger) spectrum. The ambivalent role of singly occupied sites is key to understanding the doublon physics; for high fillings, ground-state configurations with single occupancies are recognized to strongly relax the kinematic constraints and to open up decay channels. For fillings close to half-filling, however, their presence actually blocks the doublon decay. Finally, the analysis of the continua in the two-hole spectrum excludes a picture where the doublon decays into unbound electron holes for generic fillings, different from the limiting case of the completely filled band. We demonstrate that the decay products as well as the doublon propagation should rather be understood in terms of Bethe ansatz eigenstates.
A quantum gas microscope for detecting single atoms in a Hubbard-regime optical lattice.
Bakr, Waseem S; Gillen, Jonathon I; Peng, Amy; Fölling, Simon; Greiner, Markus
2009-11-05
Recent years have seen tremendous progress in creating complex atomic many-body quantum systems. One approach is to use macroscopic, effectively thermodynamic ensembles of ultracold atoms to create quantum gases and strongly correlated states of matter, and to analyse the bulk properties of the ensemble. For example, bosonic and fermionic atoms in a Hubbard-regime optical lattice can be used for quantum simulations of solid-state models. The opposite approach is to build up microscopic quantum systems atom-by-atom, with complete control over all degrees of freedom. The atoms or ions act as qubits and allow the realization of quantum gates, with the goal of creating highly controllable quantum information systems. Until now, the macroscopic and microscopic strategies have been fairly disconnected. Here we present a quantum gas 'microscope' that bridges the two approaches, realizing a system in which atoms of a macroscopic ensemble are detected individually and a complete set of degrees of freedom for each of them is determined through preparation and measurement. By implementing a high-resolution optical imaging system, single atoms are detected with near-unity fidelity on individual sites of a Hubbard-regime optical lattice. The lattice itself is generated by projecting a holographic mask through the imaging system. It has an arbitrary geometry, chosen to support both strong tunnel coupling between lattice sites and strong on-site confinement. Our approach can be used to directly detect strongly correlated states of matter; in the context of condensed matter simulation, this corresponds to the detection of individual electrons in the simulated crystal. Also, the quantum gas microscope may enable addressing and read-out of large-scale quantum information systems based on ultracold atoms.
Spatial structure of morphological and neutral genetic variation in Brook Trout
Kazyak, David C.; Hilderbrand, Robert H.; Keller, Stephen R.; Colaw, Mark C.; Holloway, Amanda E.; Morgan, Raymond P.; King, Timothy L.
2015-01-01
Brook Trout Salvelinus fontinalis exhibit exceptional levels of life history variation, remarkable genetic variability, and fine-scale population structure. In many cases, neighboring populations may be highly differentiated from one another to an extent that is comparable with species-level distinctions in other taxa. Although genetic samples have been collected from hundreds of populations and tens of thousands of individuals, little is known about whether differentiation at neutral markers reflects phenotypic differences among Brook Trout populations. We compared differentiation in morphology and neutral molecular markers among populations from four geographically proximate locations (all within 24 km) to examine how genetic diversity covaries with morphology. We found significant differences among and/or within streams for all three morphological axes examined and identified the source stream of many individuals based on morphology (52.3% classification efficiency). Although molecular and morphological differentiation among streams ranged considerably (mean pairwise FST: 0.023–0.264; pairwise PST: 0.000–0.339), the two measures were not significantly correlated. While in some cases morphological characters appear to have diverged to a greater extent than expected by neutral genetic drift, many traits were conserved to a greater extent than were neutral genetic markers. Thus, while Brook Trout exhibit fine-scale spatial patterns in both morphology and neutral genetic diversity, these types of biological variabilities are being structured by different ecological and evolutionary processes. The relative influences of genetic drift versus selection and phenotypic plasticity in shaping morphology appear to vary among populations occupying nearby streams.
New orbit recalculations of comet C/1890 F1 Brooks and its dynamical evolution
Królikowska, Małgorzata; Dybczyński, Piotr A.
2016-08-01
C/1890 F1 Brooks belongs to a group of 19 comets used by Jan Oort to support his famous hypothesis on the existence of a spherical cloud containing hundreds of billions of comets with orbits of semi-major axes between 50 000 and 150 000 au. Comet Brooks stands out from this group because of a long series of astrometric observations as well as a nearly 2-yr-long observational arc. Rich observational material makes this comet an ideal target for testing the rationality of an effort to recalculate astrometric positions on the basis of original (comet-star) measurements using modern star catalogues. This paper presents the results of such a new analysis based on two different methods: (i) automatic re-reduction based on cometary positions and the (comet-star) measurements and (ii) partially automatic re-reduction based on the contemporary data for the reference stars originally used. We show that both methods offer a significant reduction in the uncertainty of orbital elements. Based on the most preferred orbital solution, the dynamical evolution of comet Brooks during three consecutive perihelion passages is discussed. We conclude that C/1890 F1 is a dynamically old comet that passed the Sun at a distance below 5 au during its previous perihelion passage. Furthermore, its next perihelion passage will be a little closer than during the 1890-1892 apparition. C/1890 F1 is interesting also because it suffered extremely small planetary perturbations when it travelled through the planetary zone. Therefore, in the next passage through perihelion, it will once again be a comet from the Oort spike.
Berberian, B J; Sulica, V I; Kao, G F
1990-07-01
Four cases of rare familial multiple eccrine spiradenomas showing features of dermal cylindromas and associated with epithelioma adenoides cysticum of Brooke are reported. Skin biopsy specimens were obtained from three generations of this family and routine histochemical and immunoperoxidase stains were used. The eldest affected family member had multiple disfiguring facial and scalp tumors, which precipitated episodes of depression. Unlike other cutaneous genetic disorders, such as neurofibromatosis and tuberous sclerosis, the cutaneous adnexal tumors occurring in these patients continue to erupt and grow during their lifetimes.
Kerry Heckenberg
2014-01-01
Much of the critical response to Brook Andrew’s reinterpretation of images from a colonial archive in his 2008 series The Island situated the work in a tradition of post-colonial critique of documentary images. But is this an adequate account of either Andrew’s work or the archive in question, William Blandowski’s Australien in 142 Photographischen Abbildungen (1862)? This essay looks at practices involving copying and their impact on understandings of authenticity, the role of art in science...
Thermal Vacuum Testing of ICPTA RCS at Plum Brook B-2
Atwell, M. J.; Hurlbert, E. A.; Melcher, J. C.; Morehead, R. L.
2017-01-01
Vacuum and thermal vacuum testing of the Integrated Cryogenic Propulsion Test Article (ICPTA) was performed at the Plum Brook B-2 facility as a part of a system checkout and facility characterization effort. Multiple test objectives included: integrated Reaction Control System (RCS) characterization, cold helium pressurization system characterization, modal propellant gaging experiment (Orion), CFM propellant loading experiments, main engine characterization. The ICPTA is a test bed for LOX/LCH4 technologies built in 2016 using new components and hardware from the former Morpheus vehicle and other projects.
Directory of Open Access Journals (Sweden)
Irena Vardić
2007-01-01
Full Text Available Pathogenic bacterium Renibacterium salmoninarum causes kidney disease with high mortality rate and considerable economic losses in salmonid farming. Thus, application of fast and sensitive method for R. salmoninarum diagnosis is of great importance. This paper describes detection of R. salmoninarum in brook trout tissue with gross clinical signs of disease by nested RT–PCR. Determination of partial sequence of bacterial msa gene was done prior to comparison with similar sequences from different R. salmoninarum isolates. Nested RT–PCR proved to be a rapid and valuable diagnostic tool for R. salmoninarum detection, and sequence analysis confirmed previously reported genetic uniformity of this bacteria
Ivanoff, Michael A.; Medalie, Laura
1997-01-01
This report provides the results of a detailed Level II analysis of scour potential at structure WALDTH00450021 on Town Highway 45 crossing Joes Brook, Walden, Vermont (figures 1–8). A Level II study is a basic engineering analysis of the site, including a quantitative analysis of stream stability and scour (U.S. Department of Transportation, 1993). Results of a Level I scour investigation also are included in Appendix E of this report. A Level I investigation provides a qualitative geomorphic characterization of the study site. Information on the bridge, gleaned from Vermont Agency of Transportation (VTAOT) files, was compiled prior to conducting Level I and Level II analyses and is found in Appendix D. The VTAOT files state that the stream is Coles Brook, both the USGS and the VTAOT maps state that it is Joes Brook.
2010-01-20
... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF ENERGY Federal Energy Regulatory Commission J&T Hydro Company; H. Dean Brooks and W. Bruce Cox; Notice of Application... 30, 2009, J&T Hydro Company (transferor) and W. Dean Brooks, and H. Bruce Cox (transferees) filed...
Gershenzon, Naum I; Dominic, David F; Mehnert, Edward; Okwen, Roland T
2015-01-01
Geological heterogeneities essentially affect the dynamics of a CO2 plume in subsurface environments. Previously we showed how the dynamics of a CO2 plume is influenced by the multi-scale stratal architecture in deep saline reservoirs. The results strongly suggest that representing small-scale features is critical to understanding capillary trapping processes. Here we present the result of simulation of CO2 trapping using two different conventional approaches, i.e. Brooks-Corey and van Genuchten, for the capillary pressure curves. We showed that capillary trapping and dissolution rates are very different for the Brooks-Corey and van Genuchten approaches when heterogeneity and hysteresis are both represented.
Rebecca R. Bourgault; Donald S. Ross; Scott W. Bailey; Thomas D. Bullen; Kevin J. McGuire; John P. Gannon
2017-01-01
Emerging evidence shows that interactions between soils and subsurface flow paths contribute to spatial variations in stream water chemistry in headwater catchments. However, few have yet attempted to quantify chemical variations in soils at catchment and hillslope scales. Watershed 3 (WS3) at Hubbard Brook Experimental Forest, New Hampshire, USA, was studied in order...
Reply to Smith and Shortle: Lacking evidence of hydraulic efficiency changes
Mark B. Green; Amey S. Bailey; Scott W. Bailey; John J. Battles; John L. Campbell; Charles T. Driscoll; Timothy J. Fahey; Lucie C. Lepine; Gene E. Likens; Scott V. Ollinger; Paul G. Schaberg
2013-01-01
After calcium silicate amendment to an entire watershed at the Hubbard Brook Experimental Forest, evapotranspiration (ET) increased by ~20% for 2 y, broadly attributed to a fertilization of tree physiology (1). We suggested that the increase in ET most likely arose from enhanced transpiration due to increased stomatal conductance (gs) associated with increased...
Stable water isotopes suggest sub-canopy water recycling in a northern forested catchment
Mark B. Green; Bethany K. Laursen; John L. Campbell; Kevin J. McGuire; Eric P. Kelsey
2015-01-01
Stable water isotopes provide a means of tracing many hydrologic processes, including poorly understood dynamics like soil water interactions with the atmosphere. We present a four-year dataset of biweekly water isotope samples from eight fluxes and stores in a headwater catchment at the Hubbard Brook Experimental Forest, New Hampshire, USA. We use Dansgaard's...
John P. Gannon; Scott W. Bailey; Kevin J. McGuire
2014-01-01
A network of shallow groundwater wells in a headwater catchment at the Hubbard Brook Experimental Forest in New Hampshire, U.S. was used to investigate the hydrologic behavior of five distinct soil morphological units. The soil morphological units were hypothesized to be indicative of distinct water table regimes. Water table fluctuations in the wells were...
John P. Gannon; Kevin J. McGuire; Scott W. Bailey; Rebecca R. Bourgault; Donald S. Ross
2017-01-01
Measurements of soil water potential and water table fluctuations suggest that morphologically distinct soils in a headwater catchment at the Hubbard Brook Experimental Forest in New Hampshire formed as a result of variations in saturated and unsaturated hydrologic fluxes in the mineral soil. Previous work showed that each group of these soils had distinct water table...
Turecek, Aaron M.; Danforth, William W.; Baldwin, Wayne E.; Barnhardt, Walter A.
2012-01-01
The U.S. Geological Survey conducted a high-resolution geophysical survey within Red Brook Harbor, Massachusetts, from September 28 through November 17, 2009. Red Brook Harbor is located on the eastern edge of Buzzards Bay, south of the Cape Cod Canal. The survey area was approximately 7 square kilometers, with depths ranging from 0 to approximately 10 meters. Data were collected aboard the U.S. Geological Survey Research Vessel Rafael. The research vessel was equipped with a 234-kilohertz interferometric sonar system to collect bathymetry and backscatter data, a dual frequency (3.5- and 200-kilohertz) compression high-intensity radar pulse seismic reflection profiler to collect subbottom data, a sound velocity profiler to acquire speed of sound within the water column, and a sea floor sampling device to collect sediment samples, video, and photographs. The survey was part of an ongoing cooperative effort between the U.S. Geological Survey and the Massachusetts Office of Coastal Zone Management to map the geology of the Massachusetts inner continental shelf. In addition to inclusion within the cooperative geologic mapping effort, these data will be used to assess the shallow-water mapping capability of the geophysical systems deployed for this project, with an emphasis on identifying resolution benchmarks for the interferometric sonar system.
Plant communities as indicators of salt marsh hydrology A study at Goose Fare Brook, Saco, Maine
Energy Technology Data Exchange (ETDEWEB)
Millette, P.M. (Univ. of Maine, Orono, ME (United States). Dept. of Geological Sciences)
1993-03-01
Salt marsh stratigraphy often relies on vegetation fragment distribution as an indicator of paleo-sea level. This study is attempting to validate the use of Spartina alterniflora and Spartina patens at Goose Fare Brook in Saco, Maine as paleo-sea level indicators. Plant zones were mapped and each zone boundary was surveyed to describe the relationship between sea level and plant species zonation. Data showing the contact elevations between S. patens and S. alterniflora were examined, and contacts from different environments in the marsh were compared. Differences in contact elevations ranged from only a few centimeters to more than eighty centimeters. Three series of groundwater monitoring wells were installed along transects. Within a single transect, one well was placed in the creek bottom, measuring the free water surface, and one was placed at each of several plant zone boundaries. Strip chart recordings from one series of monitoring wells show the flood dominated patterns of tidally influenced groundwater fluctuations in the wells. Root depths of 100 plugs each of S. alterniflora and S. patens were also measured. A comparison of these measurements and those from monitoring wells will assist in the determination of the average length of submergence time for each species. Preliminary findings suggest that sea level is not the only force affecting the modern zonation of these two indicator plants in Goose Fare Brook.
Structural provinces of the northeastern Brooks Range, Arctic National Wildlife Refuge, Alaska
Energy Technology Data Exchange (ETDEWEB)
Wallace, W.K.; Hanks, C.L. (Univ. of Alaska, Fairbanks (USA))
1990-07-01
The dominant Cenozoic structures of the northeastern Brooks Range are anticlinoria with cores of sub-Mississippian rocks, reflecting a regional north-vergent duplex with a floor thrust in the sub-Mississippian sequence and a roof thrust in the Mississippian Kayak Shale. The number of horses forming each anticlinorium and the structural style of the overlying Mississippian and younger cover sequence varies regionally, providing a basis for dividing the northeastern Brooks Range into structural provinces. In the western province, each anticlinorium contains a single horse, and shortening above the Kayak Shale was accommodated mainly by detachment folds. To the north in the Sadlerochit Mountains, the Kayak Shale is depositionally discontinuous and rocks elsewhere separated by this detachment deformed together. In the eastern province, each anticlinorium contains multiple horses, and shortening above the Kayak Shale was accommodated largely by thrust duplication of Mississippian through Triassic rocks. In the narrow central province, the Devonian Okpilak batholith was detached from its roots, internally shortened along shear zones and by penetrative strain, and transported northward. Because the Kayak Shale is locally absent, the Mississippian and younger cover sequence deformed in part penetratively along with the batholith. 13 figs.
New orbit recalculations of comet C/1890 F1 Brooks and its dynamical evolution
Królikowska, Małgorzata
2016-01-01
C/1890 F1 Brooks belongs to a group of nineteen comets used by Jan Oort to support his famous hypothesis on the existence of a spherical cloud containing hundreds of billions of comets with orbits of semimajor axes between 50 and 150 thousand au. Comet Brooks stands out from this group because of a long series of astrometric observations as well as nearly two-year long observational arc. Rich observational material makes this comet an ideal target for testing the rationality of an effort to recalculate astrometric positions on the basis of original (comet-star)-measurements using modern star catalogues. This paper presents the results of such new analysis based on two different methods: (i) automatic re-reduction based on cometary positions and the (comet-star)-measurements, and (ii) partially automatic re-reduction based on the contemporary data for originally used reference stars. We show that both methods offer a significant reduction of orbital elements uncertainties. Based on the most preferred orbital s...
Gomes, N; Clay, R T; Mazumdar, S
2013-09-25
A frustrated, effective ½-filled band Hubbard-Heisenberg model has been proposed for describing the strongly dimerized charge-transfer solid families κ-(ET)2X and Z[Pd(dmit)2]2. In addition to showing unconventional superconductivity, these materials also exhibit antiferromagnetism, candidate spin-liquid phases, and, in the case of Z=EtMe3P, a spin-gapped phase that has sometimes been referred to as a valence bond solid. We show that neither superconductivity nor the valence bond order phase occurs within the Hubbard-Heisenberg model. We suggest that a description based on ¼-filling, that is reached when the carrier concentration per molecule instead of per dimer is considered, thus may be appropriate.
NASA's Hydrogen Outpost: The Rocket Systems Area at Plum Brook Station
Arrighi, Robert S.
2016-01-01
"There was pretty much a general knowledge about hydrogen and its capabilities," recalled former researcher Robert Graham. "The question was, could you use it in a rocket engine? Do we have the technology to handle it? How will it cool? Will it produce so much heat release that we can't cool the engine? These were the questions that we had to address." The National Aeronautics and Space Administration's (NASA) Glenn Research Center, referred to historically as the Lewis Research Center, made a concerted effort to answer these and related questions in the 1950s and 1960s. The center played a critical role transforming hydrogen's theoretical potential into a flight-ready propellant. Since then NASA has utilized liquid hydrogen to send humans and robots to the Moon, propel dozens of spacecraft across the universe, orbit scores of satellite systems, and power 135 space shuttle flights. Rocket pioneers had recognized hydrogen's potential early on, but its extremely low boiling temperature and low density made it impracticable as a fuel. The Lewis laboratory first demonstrated that liquid hydrogen could be safely utilized in rocket and aircraft propulsion systems, then perfected techniques to store, pump, and cleanly burn the fuel, as well as use it to cool the engine. The Rocket Systems Area at Lewis's remote testing area, Plum Brook Station, played a little known, but important role in the center's hydrogen research efforts. This publication focuses on the activities at the Rocket Systems Area, but it also discusses hydrogen's role in NASA's space program and Lewis's overall hydrogen work. The Rocket Systems Area included nine physically modest test sites and three test stands dedicated to liquid-hydrogen-related research. In 1962 Cleveland Plain Dealer reporter Karl Abram claimed, "The rocket facility looks more like a petroleum refinery. Its test rigs sprout pipes, valves and tanks. During the night test runs, excess hydrogen is burned from special stacks in the best
Shastry, Sriram
2009-03-01
An exactly solvable model of spin half particles on a certain 2-dimensional frustrated lattice has been recently realized in the compound SrCu2(BO3)2, and other similar systems have been found more recently. These systems appear to be ideal testing grounds for contemporary theoretical ideas on the role of correlations and frustration in Mott Hubbard systems. In this talk I will summarize the work on these systems emphasizing their role in testing key concepts.
Kumar, Manoranjan; Soos, Zolt'an G.
2011-01-01
The bond order wave (BOW) phase of the extended Hubbard model (EHM) in one dimension (1D) is characterized at intermediate correlation $U = 4t$ by exact treatment of $N$-site systems. Linear coupling to lattice (Peierls) phonons and molecular (Holstein) vibrations are treated in the adiabatic approximation. The molar magnetic susceptibility $\\chi_M(T)$ is obtained directly up to $N = 10$. The goal is to find the consequences of a doubly degenerate ground state (gs) and finite magnetic gap $E_...
Hayward, A. L. C.; Martin, A. M.
2016-02-01
We investigate the ground-state behavior of Jaynes-Cummings-Hubbard lattices in the presence of a synthetic magnetic field, via a Gutzwiller ansatz. Specifically, we study the superfluid-Mott transition and the formation of vortex lattices in the superfluid regime. We find a suppression of the superfluid fraction due to the frustration induced by the incommensurate magnetic and spacial lattice lengths. We also predict the formation of triangular vortex lattices inside the superfluid regime.
Gadomski, P.; Finnegan, D. C.; Lawson, D. E.; Hanlon, G.
2009-12-01
Quantitative high-resolution, multi-year datasets on tidewater glacier terminus activity are difficult and expensive to obtain and few in number. Furthermore, numerous factors influence terminus dynamics, thus requiring a holistic approach to data gathering to understand such activity. This paper describes ongoing research at Hubbard Glacier in Southeast Alaska and how these efforts are improving our understanding of an actively advancing tidewater margin. Hubbard Glacier, the largest tidewater glacier in North America, flows ~125 km from Mt Logan (5959 m) in the St. Elias Mountains to sea level where its terminus continues to thicken, widen and advance at an average rate of 32m/yr. Continued advance of the Hubbard Glacier may dam the channel linking Russell Fiord with Disenchantment Bay and potentially result in flooding of the Situk River destroying a fishery that provides the economic base for the community of Yakutat. As part of a multi-year investigation to monitor and assess the risk of dam formation by Hubbard Glacier, near real-time meteorological and terminus motion data are being monitored, while detailed field and remote sensing investigations quantify glacier activity. These investigations have included bathymetric mapping and hydrographic surveys, aerial and ground-based LiDAR topographic surveys, time-lapse photography and recurring satellite imagery of the glacier since 2005. Over the approximate three years of continuous near-realtime field-based monitoring the duration, patterns and daily rates of terminus advance and retreat are proving to be similar from year to year. These patterns suggest that the onset of advance and retreat may be linked to climate and extreme variations in the tidal cycle are influential in slowing terminus advance and causing periods of retreat to be superimposed onto longer durations of advance. These results when linked to time-lapse photography provide insight into ice marginal mechanisms of calving, while the results of
Hückel-Hubbard-Ohno modeling of π-bonds in ethene and ethyne with application to trans-polyacetylene
Timár, Máté; Barcza, Gergely; Gebhard, Florian; Veis, Libor; Legeza, Örs
Quantum chemistry calculations provide the potential energy between two carbon atoms in ethane (H$_3$C$-$CH$_3$), ethene (H$_2$C$=$CH$_2$), and ethyne (HC$\\equiv$CH) as a function of the atomic distance. Based on the energy function for the $\\sigma$-bond in ethane, $V_{\\sigma}(r)$, we use the H\\"uckel model with Hubbard--Ohno interaction for the $\\pi$~electrons to describe the energies $V_{\\sigma\\pi}(r)$ and $V_{\\sigma\\pi\\pi}(r)$ for the $\\sigma\\pi$ double bond in ethene and the $\\sigma\\pi\\pi$ triple bond in ethyne, respectively. The fit of the force functions shows that the Peierls coupling can be estimated with some precision whereas the Hubbard-Ohno parameters are insignificant at the distances under consideration. We apply the H\\"uckel-Hubbard-Ohno model to describe the bond lengths and the energies of elementary electronic excitations of trans-polyacetylene, (CH)$_n$, and adjust the $\\sigma$-bond potential for conjugated polymers.
Nocera, A.; Soltanieh-ha, M.; Perroni, C. A.; Cataudella, V.; Feiguin, A. E.
2014-11-01
We calculate the spectral function of the one-dimensional Hubbard-Holstein model using the time-dependent density matrix renormalization group, focusing on the regime of large local Coulomb repulsion, and away from electronic half-filling. We argue that, from weak to intermediate electron-phonon coupling, phonons interact only with the electronic charge, and not with the spin degrees of freedom. For strong electron-phonon interaction, spinon and holon bands are not discernible anymore and the system is well described by a spinless polaronic liquid. In this regime, we observe multiple peaks in the spectrum with an energy separation corresponding to the energy of the lattice vibrations (i.e., phonons). We support the numerical results by introducing a well controlled analytical approach based on Ogata-Shiba's factorized wave function, showing that the spectrum can be understood as a convolution of three contributions, originating from charge, spin, and lattice sectors. We recognize and interpret these signatures in the spectral properties and discuss the experimental implications.
Araujo-Lopez, Eduard; Varilla, Luis Alcala; Seriani, Nicola; Montoya, Javier A.
2016-11-01
Theoretical ab initio studies done so far on the structural properties of the titanium dioxide anatase (001) surface, have not reported simultaneously the complete set of cell and interatomic parameters for this system or its bulk. Here we present a complete report of these quantities within a spin polarized Density Functional Theory calculation, including also the Hubbard term and the van der Waals dispersion contribution. We show that within this approach it is possible to find a description of TiO2 anatase using DFT, that correlates better with experimental results than most theoretical studies reported previously. This good level of agreement has an advantage with respect to other very accurate studies which have performed computationally expensive calculations involving hybrid functionals, in that our method tends to be faster while also including the van der Waals dispersion contributions in addition to the treatment of correlations. The observed high-quality description of a system like TiO2 within this approach is important and encouraging; specially because it treats properly a d-shell element that is possibly going to have, for many applications of interest, long-range interaction with molecules, e.g. in studies of photocatalysis, where one needs all the relevant physics of the system to be included. We support this claim with an example of the effects that long-range interactions have on a CO2 molecule at the (001) surface.
Saha, Madhumita; Maiti, Santanu K.
2016-10-01
The interplay between Hubbard interaction, long-range hopping and disorder on persistent current in a mesoscopic one-dimensional conducting ring threaded by a magnetic flux ϕ is analyzed in detail. Two different methods, exact numerical diagonalization and Hartree-Fock mean field theory, are used to obtain numerical results from the many-body Hamiltonian. The current in a disordered ring gets enhanced as a result of electronic correlation and it becomes more significant when contributions from higher order hoppings, even if they are too small compared to nearest-neighbor hopping, are taken into account. Certainly this can be an interesting observation in the era of long-standing controversy between theoretical and experimental results of persistent current amplitudes. Along with these we also find half-flux quantum periodic current for some typical electron fillings and kink-like structures at different magnetic fluxes apart from ϕ = 0 and ±ϕ0 / 2. The scaling behavior of current is also discussed for the sake of completeness of our present analysis.
Deng, Haiming; Dai, Hui; Huang, Jiahao; Qin, Xizhou; Xu, Jun; Zhong, Honghua; He, Chunshan; Lee, Chaohong
2015-08-01
We present a cluster Gutzwiller mean-field study for ground states and time-evolution dynamics in the Bose-Hubbard ladder (BHL), which can be realized by loading Bose atoms in double-well optical lattices. In our cluster mean-field approach, we treat each double-well unit of two lattice sites as a coherent whole for composing the cluster Gutzwiller ansatz, which may remain some residual correlations in each two-site unit. For an unbiased BHL, in addition to conventional superfluid phase and integer Mott insulator phases, we find that there are exotic fractional insulator phases if the interchain tunneling is much stronger than the intrachain one. The fractional insulator phases cannot be found by using a conventional mean-field treatment based upon the single-site Gutzwiller ansatz. For a biased BHL, we find there appear single-atom tunneling and interaction blockade if the system is dominated by the interplay between the on-site interaction and the interchain bias. In the many-body Landau-Zener process, in which the interchain bias is linearly swept from negative to positive or vice versa, our numerical results are qualitatively consistent with the experimental observation [Nat. Phys. 7, 61 (2011), 10.1038/nphys1801]. Our cluster bosonic Gutzwiller treatment is of promising perspectives in exploring exotic quantum phases and time-evolution dynamics of bosonic particles in superlattices.
The microsomal metabolism of phenol (11 degrees C) over an annual reproductive cycle from June to December has been studied using fall spawning adult brook trout (Salvelinus fontinalis). Incubations were optimized for time, cofactor connection, pH, and microsomal protein concentr...
Striker, Lora K.; Medalie, Laura
1997-01-01
This report provides the results of a detailed Level II analysis of scour potential at structure WALDTH00020007 on Town Highway 2 crossing Coles Brook, Walden, Vermont (figures 1–8). Coles Brook is also referred to as Joes Brook. A Level II study is a basic engineering analysis of the site, including a quantitative analysis of stream stability and scour (U.S. Department of Transportation, 1993). Results of a Level I scour investigation also are included in Appendix E of this report. A Level I investigation provides a qualitative geomorphic characterization of the study site. Information on the bridge, gleaned from Vermont Agency of Transportation (VTAOT) files, was compiled prior to conducting Level I and Level II analyses and is found in Appendix D. The site is in the New England Upland section of the New England physiographic province in north-eastern Vermont. The 12.8-mi2 drainage area is in a predominantly rural and forested basin. In the vicinity of the study site, the surface cover is predominantly shrub and brushland. In the study area, Coles Brook has a sinuous channel with a slope of approximately 0.005 ft/
Gafney, Leo; Bynum, R. David; Sheppard, Keith
2015-01-01
This report describes the origin and development of CESAME (The Center for Science and Mathematics Education) at Stony Brook University. The analysis identifies key ingredients in areas of personnel, funding, organizational structures, educational priorities, collaboration, and institutionalization. After a discussion of relevant issues in…
2010-08-25
... Environmental Policy Act; NASA Glenn Research Center Plum Brook Station Wind Farm Project AGENCY: National... and to conduct scoping for the NASA Glenn Research Center (GRC). SUMMARY: NASA intends to conduct... Project located near Sandusky, Ohio, pursuant to the National Environmental Policy Act of 1969, as...
Zhang, Yuejiao
2013-01-01
This article examines the influential Chinese science book "Brush Talks from Dream Brook," written by Shen Kuo in the 11th century. I suggest that "Brush Talks" reveals a tension between institutionalized science and science in the public, and a gap between the making of scientific knowledge and the communication of such…
Benjamin H. Letcher; Jason A Coombs; Keith H. Nislow
2011-01-01
Phenotypic variation in body size can result from within-cohort variation in birth dates, among-individual growth variation and size-selective processes. We explore the relative effects of these processes on the maintenance of wide observed body size variation in stream-dwelling brook trout (Salvelinus fontinalis). Based on the analyses of multiple...
Sherin, Bruce
2015-01-01
In this commentary, the author presents his thoughts on two papers appearing in this special issue. The first, "The Importance of Language in Students' Reasoning about Heat in Thermodynamic Processes," by David T. Brookes and Eugenia Etkina (See: EJ1060728), and the second, "Varying Use of Conceptual Metaphors Across Levels of…
Sloss, Brian L.; Jennings, Martin J.; Franckowiak, R.; Pratt, D.M.
2008-01-01
Rehabilitation of migratory ('coaster') brook trout Salvelinus fontinalis along Lake Superior's south shore is a topic of high interest among resource stakeholders and management agencies. Proposed strategies for rehabilitation of this brook trout life history variant in Wisconsin include supplemental stocking, watershed management, habitat rehabilitation, harvest regulations, or a combination thereof. In an effort to evaluate the success of coaster brook trout rehabilitation efforts, we collected genetic data from four populations of interest (Whittlesey Creek, Bois Brule River, Bark River, and Graveyard Creek) and the hatchery sources used in the Whittlesey Creek supplementation experiment. We characterized the genetic diversity of 30 individuals from each of four populations using 13 microsatellite DNA loci. Levels of genetic variation were consistent with those in similar studies conducted throughout the basin. Significant genetic variation among the populations was observed, enabling adequate population delineation through assignment tests. Overall, 208 of the 211 sampled fish (98.6%) were correctly assigned to their population of origin. Simulated F1 hybrids between two hatchery strains and the Whittlesey Creek population were identifiable in the majority of attempts (90.5-100% accuracy with 0-2.5% error). The genetic markers and analytical techniques described provide the ability to monitor the concurrent coaster brook trout rehabilitation efforts along Wisconsin's Lake Superior south shore, including the detection of hybridization between hatchery and native populations. ?? Copyright by the American Fisheries Society 2008.
Directory of Open Access Journals (Sweden)
Horká Petra
2017-01-01
Full Text Available Quantifying patterns of prey resource use is fundamental to identify mechanisms enabling the coexistence of related fish species. Trophic interactions between the native brown trout, Salmo trutta, and the introduced brook trout, Salvelinus fontinalis, were studied monthly from May to October in three mountain streams in Central Europe (Czech Republic. To evaluate whether the feeding habits differ between separated and coexisting populations of these species, one locality where both species coexist, and two allopatric populations of either species were studied. Across the study period, the mean stomach fullness of fish varied, being highest in spring and declining through autumn. The diet overlap (Schoener's overlap index between the species increased through the studied season (from 54.5% in July to 81.5% in October. In allopatry, both species had nearly the same feeding habits. However, in sympatry, brook trout consumed higher proportion of terrestrial invertebrates, while brown trout showed no changes either in the proportions of aquatic and terrestrial prey utilized or in the selectivity for prey categories in comparison to allopatric conditions. The dietary shift observed for brook trout, but not for brown trout, suggests that brown trout is a stronger competitor in the studied sympatric locality, leading the brook trout to change its feeding habits to reduce interspecific competition.
Brownlee, Annalis H; Sullivan, Patrick F; Csank, Adam Z; Sveinbjörnsson, Bjartmar; Ellison, Sarah B Z
2016-01-01
Increment cores from the boreal forest have long been used to reconstruct past climates. However, in recent years, numerous studies have revealed a deterioration of the correlation between temperature and tree growth that is commonly referred to as divergence. In the Brooks Range of northern Alaska, USA, studies of white spruce (Picea glauca) revealed that trees in the west generally showed positive growth trends, while trees in the central and eastern Brooks Range showed mixed and negative trends during late 20th century warming. The growing season climate of the eastern Brooks Range is thought to be drier than the west. On this basis, divergent tree growth in the eastern Brooks Range has been attributed to drought stress. To investigate the hypothesis that drought-induced stomatal closure can explain divergence in the Brooks Range, we synthesized all of the Brooks Range white spruce data available in the International Tree Ring Data Bank (ITRDB) and collected increment cores from our primary sites in each of four watersheds along a west-to-east gradient near the Arctic treeline. For cores from our sites, we measured ring widths and calculated carbon isotope discrimination (δ13C), intrinsic water-use efficiency (iWUE), and needle intercellular CO2 concentration (C(i)) from δ13C in tree-ring alpha-cellulose. We hypothesized that trees exhibiting divergence would show a corresponding decline in δ13C, a decline in C(i), and a strong increase in iWUE. Consistent with the ITRDB data, trees at our western and central sites generally showed an increase in the strength of the temperature-growth correlation during late 20th century warming, while trees at our eastern site showed strong divergence. Divergent tree growth was not, however, associated with declining δ13C. Meanwhile, estimates of C(i) showed a strong increase at all of our study sites, indicating that more substrate was available for photosynthesis in the early 21st than in the early 20th century. Our
Pallister, John S.; Budahn, James R.; Murchey, Benita L.
1989-11-01
The Angayucham Mountains (north margin of the Yukon-Koyukuk province) are made up of an imbricate stack of four to eight east-west trending, steeply dipping, fault slabs composed of Paleozoic (Devonian to Mississippean), Middle to Late Triassic, and Early Jurassic oceanic upper crustal rocks (pillow basalt, subordinate diabase, basaltic tuff, and radiolarian chert). Field relations and geochemical characteristics of the basaltic rocks suggest that the fault slabs were derived from an oceanic plateau or island setting and were emplaced onto the Brooks Range continental margin. The basalts are variably metamorphosed to prehnite-pumpellyite and low-greenschist facies. Major element analyses suggest that many are hypersthene-normative olivine tholeiites. Classification based on immobile trace elements confirms the tholeiitic character of most of the basalts but suggests that some had primary compositions transitional to alkali basalt. Although field and petrographic features of the basalts are similar, trace element characteristics allow definition of geographically distinct suites. A central outcrop belt along the crest of the mountains is made up of basalt with relatively flat rare earth element (REE) patterns. This belt is flanked to the north and south by LREE (light rare earth element)-enriched basalts. Radiolarian and conodont ages from interpillow and interlayered chert and limestone indicate that the central belt of basalts is Triassic in age, the southern belt is Jurassic in age, and the northern belt contains a mixture of Paleozoic and Mesozoic ages. Data for most of the basalts cluster in the "within-plate basalt" fields of trace element discriminant diagrams; none have trace-element characteristics of island arc basalt. The Triassic and Jurassic basalts are geochemically most akin to modern oceanic plateau and island basalts. Field evidence also favors an oceanic plateau or island setting. The great composite thickness of pillow basalt probably resulted
On the particle-hole symmetry of the fermionic spinless Hubbard model in D=1
Directory of Open Access Journals (Sweden)
M.T. Thomaz
2014-06-01
Full Text Available We revisit the particle-hole symmetry of the one-dimensional (D=1 fermionic spinless Hubbard model, associating that symmetry to the invariance of the Helmholtz free energy of the one-dimensional spin-1/2 XXZ Heisenberg model, under reversal of the longitudinal magnetic field and at any finite temperature. Upon comparing two regimes of that chain model so that the number of particles in one regime equals the number of holes in the other, one finds that, in general, their thermodynamics is similar, but not identical: both models share the specific heat and entropy functions, but not the internal energy per site, the first-neighbor correlation functions, and the number of particles per site. Due to that symmetry, the difference between the first-neighbor correlation functions is proportional to the z-component of magnetization of the XXZ Heisenberg model. The results presented in this paper are valid for any value of the interaction strength parameter V, which describes the attractive/null/repulsive interaction of neighboring fermions.
Delocalization effect of the Hubbard repulsion in two dimensions and exact terms
Gulacsi, Zsolt
2009-03-01
The physical reasons explaining the delocalization effect of the Hubbard repulsion U leading in 2D to an insulator to metal transition are analyzed. The study is made in exact terms by deducing exact ground states and ground state expectation values of interest based on a positive semidefinite operator technique [1]. First it is shown that always when this effect is observed, U acts on the background of a macroscopic degeneracy present in a multiband type of system. After this step I demonstrate that acting in such conditions, by strongly diminishing the double occupancy, U spreads out the contributions in the ground state wave function, hence strongly increases the one-particle localization length, and consequently extends the one-particle behavior producing conditions for a delocalization effect [2]. [3pt] References: [1] Z. Gulacsi, D. Vollhardt, Phys. Rev. Lett. 91,186401(2003); Z. Gulacsi, A. Kampf, D. Vollhardt, Phys. Rev. Lett. 99,026404(2007). [2] Z. Gulacsi, Phys. Rev. B77,245113(2008).
Charge ordering and phase separation in the infinite dimensional extended Hubbard model
Tong, Ning-Hua; Shen, Shun-Qing; Bulla, Ralf
2004-08-01
We study the extended Hubbard model with both on-site (U) and nearest neighbor (V) Coulomb repulsion using the exact diagonalization method within the dynamical mean field theory. For a fixed U (U=2.0) , the T-n phase diagrams are obtained for V=1.4 and V=1.2 , at which the ground state of n=1/2 system is charge-ordered and charge-disordered, respectively. In both cases, robust charge order is found at finite temperature and in an extended filling regime around n=1/2 . The order parameter changes nonmonotonously with temperature. For V=1.4 , phase separation between charge-ordered and charge-disordered phases is observed in the low temperature and n<0.5 regime. It is described by an “S”-shaped structure of the n-μ curve. For V=1.2 , the ground state is charge-disordered, and a reentrant charge-ordering transition is observed for 0.42
Quantum Geometry of the ``Fuzzy-Lattice'' Hubbard Model and the Fractional Chern Insulator
Vijay, Sagar; Haldane, F. D. M.
2013-03-01
Recent studies of interacting particles on tight-binding lattices with broken time-reversal symmetry reveal ``zero-field'' fractional quantum Hall (FQH) phases (fractional Chern insulators, FCI). In a partially-filled Landau level, the non-commutative guiding-centers are the residual degrees of freedom, requiring a ``quantum geometry'' Hilbert-space description (a real-space Schrödinger description can only apply in the ``classical geometry'' of unprojected coordinates). The continuum description does not apply on a lattice, where we describe emergence of the FCI from a non-commutative quantum lattice geometry. We define a ``fuzzy lattice'' by projecting a one-particle bandstructure (with more than one orbital per unit cell) into a single band, and then renormalize the orbital on each site to unit weight. The resulting overcomplete basis of local states is analogous to a basis of more than one coherent state per flux quantum in a Landau level. The overlap matrix characterizes ``quantum geometry'' on the ``fuzzy lattice'', defining a ``quantum distance'' measure and Berry fluxes through elementary lattice triangles. We study quantum geometry at transitions between topologically-distinct instances of a fuzzy lattice, as well as N-body states with local Hubbard interactions. supported by NSF MRSEC Grant DMR-0819860
Ginzburg-Landau expansion in BCS-BEC crossover region of disordered attractive Hubbard model
Kuchinskii, E. Z.; Kuleeva, N. A.; Sadovskii, M. V.
2017-01-01
We have studied disorder effects on the coefficients of Ginzburg-Landau expansion for attractive Hubbard model within the generalized DMFT+Σ approximation for the wide region of the values of attractive potential U—from the weak-coupling limit, where superconductivity is described by BCS model, towards the strong coupling, where superconducting transition is related to Bose-Einstein condensation (BEC) of compact Cooper pairs. For the case of semi-elliptic initial density of states disorder influence on the coefficients A and B before the square and the fourth power of the order parameter is universal for at all values of electronic correlations and is related only to the widening of the initial conduction band (density of states) by disorder. Similar universal behavior is valid for superconducting critical temperature Tc (the generalized Anderson theorem) and specific heat discontinuity at the transition. This universality is absent for the coefficient C before the gradient term, which in accordance with the standard theory of "dirty" superconductors is strongly suppressed by disorder in the weak-coupling region, but can slightly grow in BCS-BEC crossover region, becoming almost independent of disorder in the strong coupling region. This leads to rather weak disorder dependence of the penetration depth and coherence length, as well as the slope of the upper critical magnetic field at Tc, in BCS-BEC crossover and strong coupling regions.
Phase diagram of the extended Hubbard chain with charge-dipole interactions
Torio, M. E.; Aligia, A. A.; Hallberg, K.; Ceccatto, H. A.
2000-09-01
We consider a modified extended Hubbard model (EHM) which, in addition to the on-site repulsion U and nearest-neighbor repulsion V, includes polarization effects in second-order perturbation theory. The model is equivalent to an EHM with renormalized U plus a next-nearest-neighbor repulsion term. Using a method based on topological quantum numbers (charge and spin Berry phases), we generalize to finite hopping t the quantum phase diagram in one dimension constructed by van den Brink et al. [Phys. Rev. Lett. 75, 4658 (1995)]. At hopping t=0 there are two charge density-wave phases, one spin density-wave phase, and one intermediate phase with charge and spin ordering, depending on the parameter values. At t≠0 the nature of each phase is confirmed by studying correlation functions. However, in addition to the strong-coupling phases, a small region with bond ordering appears. The region occupied by the intermediate phase first increases and then decreases with increasing t, until it finally disappears for t of the order but larger than U. For small t, the topological transitions agree with the results of second-order perturbation theory.
Self-consistent Keldysh approach to quenches in the weakly interacting Bose-Hubbard model
Lo Gullo, N.; Dell'Anna, L.
2016-11-01
We present a nonequilibrium Green's-functional approach to study the dynamics following a quench in weakly interacting Bose-Hubbard model (BHM). The technique is based on the self-consistent solution of a set of equations which represents a particular case of the most general set of Hedin's equations for the interacting single-particle Green's function. We use the ladder approximation as a skeleton diagram for the two-particle scattering amplitude useful, through the self-energy in the Dyson equation, for finding the interacting single-particle Green's function. This scheme is then implemented numerically by a parallelized code. We exploit this approach to study the correlation propagation after a quench in the interaction parameter, for one and two dimensions. In particular, we show how our approach is able to recover the crossover from the ballistic to the diffusive regime by increasing the boson-boson interaction. Finally we also discuss the role of a thermal initial state on the dynamics both for one- and two-dimensional BHMs, finding that, surprisingly, at high temperature a ballistic evolution is restored.
Stability of superfluid phases in the 2D spin-polarized attractive Hubbard model
Kujawa-Cichy, A.; Micnas, R.
2011-08-01
We study the evolution from the weak coupling (BCS-like limit) to the strong coupling limit of tightly bound local pairs (LPs) with increasing attraction, in the presence of the Zeeman magnetic field (h) for d=2, within the spin-polarized attractive Hubbard model. The broken symmetry Hartree approximation as well as the strong coupling expansion are used. We also apply the Kosterlitz-Thouless (KT) scenario to determine the phase coherence temperatures. For spin-independent hopping integrals (t↑=t↓), we find no stable homogeneous polarized superfluid (SCM) state in the ground state for the strong attraction and obtain that for a two-component Fermi system on a 2D lattice with population imbalance, phase separation (PS) is favoured for a fixed particle concentration, even on the LP (BEC) side. We also examine the influence of spin-dependent hopping integrals (mass imbalance) on the stability of the SCM phase. We find a topological quantum phase transition (Lifshitz type) from the unpolarized superfluid phase (SC0) to SCM and tricritical points in the h-|U| and t↑/t↓-|U| ground-state phase diagrams. We also construct the finite temperature phase diagrams for both t↑=t↓ and t↑≠t↓ and analyze the possibility of occurrence of a spin-polarized KT superfluid.
Competing order in the fermionic Hubbard model on the hexagonal graphene lattice
Buividovich, Pavel; Ulybyshev, Maksim; von Smekal, Lorenz
2016-01-01
We study the phase diagram of the fermionic Hubbard model on the hexagonal lattice in the space of on-site and nearest neighbor couplings with Hybrid-Monte-Carlo simulations. With pure on-site repulsion this allows to determine the critical coupling strength for spin-density wave formation with the standard approach of introducing a small mass term, explicitly breaking the sublattice symmetry. The analogous mass term for charge-density wave formation above a critical nearest-neighbor repulsion, on the other hand, would introduce a fermion sign problem. The competition between the two and the phase diagram in the space of the two coouplings can however be studied in simulations without explicit sublattice symmetry breaking. Our results compare qualitatively well with the Hartree-Fock phase diagram. We furthermore demonstrate how spin-symmetry breaking by the Euclidean time discretization can be avoided also, when using an improved fermion action based on an exponetial transfer matrix with exact sublattice symm...
Interaction-induced topological and magnetic phases in the Hofstadter-Hubbard model
Kumar, Pramod; Mertz, Thomas; Hofstetter, Walter
2016-09-01
Interaction effects have been a subject of contemporary interest in topological phases of matter. But in the presence of interactions, the accurate determination of topological invariants in their general form is difficult due to their dependence on multiple integrals containing Green's functions and their derivatives. Here we employ the recently proposed "effective topological Hamiltonian" approach to explore interaction-induced topological phases in the time-reversal-invariant Hofstadter-Hubbard model. Within this approach, the zero-frequency part of the self-energy is sufficient to determine the correct topological invariant. We combine the topological Hamiltonian approach with the local self-energy approximation, both for the static and the full dynamical self-energy evaluated using dynamical mean field theory (DMFT), and present the resulting phase diagram in the presence of many-body interactions. We investigate the emergence of quantum spin Hall (QSH) states for different interaction strengths by calculating the Z2 invariant. The interplay of strong correlations and a staggered potential also induces magnetic long-range order with an associated first order transition. We present results for the staggered magnetization (ms), staggered occupancy (ns), and double occupancy across the transition.
Energy Technology Data Exchange (ETDEWEB)
Lopez-Aguilar, F.; Costa-Quintana, J. (Dept. de Fisica, Grupo de Electromagnetismo, Univ. Autonoma de Barcelona, Bellaterra, E-08193 Barcelona (ES))
1992-07-10
In this paper, the authors give a method for obtaining the renormalized electronic structure of the Hubbard systems. The first step is the determination of the self-energy beyond the Hartree-Fock approximation. This self-energy is constructed from several dielectric response functions. The second step is the determination of the quasiparticle band structure calculation which is performed from an appropriate modification of the augmented plane wave method. The third step consists in the determination of the renormalized density of states deduced from the spectral functions. The analysis of the renormalized density of states of the strongly correlated systems leads to the conclusion that there exist three types of resonances in their electronic structures, the lower energy resonances (LER), the middle energy resonances (MER) and the upper energy resonances (UER). In addition, the authors analyze the conditions for which the Luttinger theorem is satisfied. All of these questions are determined in a characteristic example which allows to test the theoretical method.
Quantum signatures of charge flipping vortices in the Bose-Hubbard trimer.
Jason, Peter; Johansson, Magnus
2016-11-01
In this work we study quantum signatures of charge flipping vortices, found in the classical discrete nonlinear Schrödinger trimer, by use of the Bose-Hubbard model. We are able to identify such signatures in the quantum energy eigenstates, for instance when comparing the site amplitudes of the classical charge flipping vortices with the probability distribution over different particle configurations. It is also discussed how to construct quantum states that correspond to the classical charge flipping vortices and which effects can lead to deviations between the classical and quantum dynamics. We also examine properties of certain coherent states: classical-like quantum states that can be used to derive the classical model. Several quantum signatures are identified when studying the dynamics of these coherent states, for example, when comparing the average number of particles on a site with the classical site amplitude, when comparing the quantum and classical currents and topological charge, and when studying the evolution of the quantum probability amplitudes. The flipping of the quantum currents are found to be an especially robust feature of these states.
Ab initio derivation of multi-orbital extended Hubbard model for molecular crystals
Tsuchiizu, Masahisa; Omori, Yukiko; Suzumura, Yoshikazu; Bonnet, Marie-Laure; Robert, Vincent
2012-01-01
From configuration interaction (CI) ab initio calculations, we derive an effective two-orbital extended Hubbard model based on the gerade (g) and ungerade (u) molecular orbitals (MOs) of the charge-transfer molecular conductor (TTM-TTP)I3 and the single-component molecular conductor [Au(tmdt)2]. First, by focusing on the isolated molecule, we determine the parameters for the model Hamiltonian so as to reproduce the CI Hamiltonian matrix. Next, we extend the analysis to two neighboring molecule pairs in the crystal and we perform similar calculations to evaluate the inter-molecular interactions. From the resulting tight-binding parameters, we analyze the band structure to confirm that two bands overlap and mix in together, supporting the multi-band feature. Furthermore, using a fragment decomposition, we derive the effective model based on the fragment MOs and show that the staking TTM-TTP molecules can be described by the zig-zag two-leg ladder with the inter-molecular transfer integral being larger than the intra-fragment transfer integral within the molecule. The inter-site interactions between the fragments follow a Coulomb law, supporting the fragment decomposition strategy.
Robust Supersolidity in the V1- V2 Extended Bose-Hubbard Model
Greene, Nicole; Pixley, Jedediah
2016-05-01
Motivated by ultra-cold atomic gases with long-range interactions in an optical lattice we study the effects of the next-nearest neighbor interaction on the extended Bose-Hubbard model on a square lattice. Using the variational Gutzwiller approach with a four-site unit cell we determine the ground state phase diagrams as a function of the model parameters. We focus on the interplay of each interaction between the nearest neighbor (V1) , the next-nearest neighbor (V2) , and the onsite repulsion (U). We find various super-solid phases that can be described by one of the ordering wave-vectors (π, 0), (0, π) , and (π, π) . In the limits V1, V2 U we find phases reminiscent of the limit V2 = 0 but with a richer super solid structure. For V1
Correlations in the ground state of the one-dimensional Hubbard model
Energy Technology Data Exchange (ETDEWEB)
Wang Qingwei, E-mail: wqw03@mails.thu.edu.c [Institute for Advanced Study, Tsinghua University, Beijing 100084 (China); Liu Yuliang, E-mail: ylliu@ruc.edu.c [Department of Physics, Renmin University of China, Beijing 100872 (China)
2009-12-14
With eigenfunctional theory and a rigorous expression of exchange-correlation energy of a general interacting electron system, we study the ground state properties of the one-dimensional Hubbard model, and calculate the ground-state energy as well as the charge gap at half-filling for arbitrary coupling strength u=U/(4t) and electron density n{sub c}. We find that the simple linear approximation of the phase field works well in weak coupling case, but it becomes inappropriate as the on-site Coulomb interaction becomes strong where the fluctuations of the bosonic auxiliary field are strong. Then we propose a new scheme by adding Gutzwiller projection which suppresses the density fluctuations and the new results are quite close to the exact ones up to considerably strong coupling strength u=3.0 and for arbitrary electron density n{sub c}. Our calculation scheme is proved to be effective for strongly correlated electron systems in one dimension, and its extension to higher dimensions is straightforward.
Pseudospin representation of the two-site Anderson-Hubbard model
Wortis, Rachel; Kennett, Malcolm
The state of an Anderson localized system can be described in terms of the occupation of a set of single-particle wave functions which are localized in space. When interactions are added, single-particle wave functions are no longer well defined, so what is a useful description of the state of a many-body localized system and what about it is localized? Given that any system with Hilbert-space dimension 2N may be described by an Ising-type Hamiltonian, it has been proposed that in a fully many-body localized system the Ising pseudospins in this representation may be chosen to be local. Actually constructing these spins is non-trivial. While a number of approaches have been proposed, few explicit examples exist and almost all work has been on spin systems. Here we present the Hamiltonian of a two-site Hubbard model with disorder and nearest-neighbor interactions written in terms of pseudospins, and we explore the form of these pseudospins and their evolution as a function of hopping amplitude. Supported by NSERC of Canada.
Phonon-like excitations in the two-state Bose-Hubbard model
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I.V. Stasyuk
2015-12-01
Full Text Available The spectrum of phonon-like collective excitations in the system of Bose-atoms in optical lattice (more generally, in the system of quantum particles described by the Bose-Hubbard model is investigated. Such excitations appear due to displacements of particles with respect to their local equilibrium positions. The two-level model taking into account the transitions of bosons between the ground state and the first excited state in potential wells, as well as interaction between them, is used. Calculations are performed within the random phase approximation in the hard-core boson limit. It is shown that excitation spectrum in normal phase consists of the one exciton-like band, while in the phase with BE condensate an additional band appears. The positions, spectral weights and widths of bands strongly depend on chemical potential of bosons and temperature. The conditions of stability of a system with respect to the lowering of symmetry and displacement modulation are discussed.
Two-state Bose-Hubbard model in the hard-core boson limit
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O.V. Velychk
2011-03-01
Full Text Available Phase transition into the phase with Bose-Einstein (BE condensate in the two-band Bose-Hubbard model with the particle hopping in the excited band only is investigated. Instability connected with such a transition (which appears at excitation energies δ0|, where |t'0| is the particle hopping parameter is considered. The re-entrant behaviour of spinodales is revealed in the hard-core boson limit in the region of positive values of chemical potential. It is found that the order of the phase transition undergoes a change in this case and becomes the first one; the re-entrant transition into the normal phase does not take place in reality. First order phase transitions also exist at negative values of δ (under the condition δ>δcrit≈ − 0.12|t'0|. At μ0|, μ phase diagrams are built and localizations of tricritical points are established. The conditions are found at which the separation on the normal phase and the phase with the BE condensate takes place.
Renormalized parameters and perturbation theory in dynamical mean-field theory for the Hubbard model
Hewson, A. C.
2016-11-01
We calculate the renormalized parameters for the quasiparticles and their interactions for the Hubbard model in the paramagnetic phase as deduced from the low-energy Fermi-liquid fixed point using the results of a numerical renormalization-group calculation (NRG) and dynamical mean-field theory (DMFT). Even in the low-density limit there is significant renormalization of the local quasiparticle interaction U ˜, in agreement with estimates based on the two-particle scattering theory of J. Kanamori [Prog. Theor. Phys. 30, 275 (1963), 10.1143/PTP.30.275]. On the approach to the Mott transition we find a finite ratio for U ˜/D ˜ , where 2 D ˜ is the renormalized bandwidth, which is independent of whether the transition is approached by increasing the on-site interaction U or on increasing the density to half filling. The leading ω2 term in the self-energy and the local dynamical spin and charge susceptibilities are calculated within the renormalized perturbation theory (RPT) and compared with the results calculated directly from the NRG-DMFT. We also suggest, more generally from the DMFT, how an approximate expression for the q ,ω spin susceptibility χ (q ,ω ) can be derived from repeated quasiparticle scattering with a local renormalized scattering vertex.
Competing instabilities in a two band Hubbard model on a square lattice
Shi, Chuntai; Tsai, Shan-Wen
2012-02-01
We study a two band Hubbard model on a two dimensional square lattice. In particular, we focus on the cases wherein one band is doped to have a small electron pocket while the other band is doped to have a hole pocket and the Fermi lines of these two pockets are nearly nested. Similar models have been studied extensively in the context related to the Iron-based material where the interactions between electrons are always repulsive. Here we investigate the generalized cases that the interactions between the fermions within the same band U1 and U2 and the interactions between electrons in different bands U12 can be tuned independently. Such models can potentially be realized in a cold atom system where the manipulation of the interaction is possible by taking advantage of the Feshbach resonance. The freedom of tuning the strength and the sign (repulsive or attractive) of the interactions, combined with the nearly nested Fermi lines, allows both the density wave phases and the pairing phases to be potential candidates for the ground state. We employ the functional renormalization group approach so that we can investigate the competition between these possible instabilities on an equal footing.
Electron-phonon vertex in the two-dimensional one-band Hubbard model
Huang, Z. B.; Hanke, W.; Arrigoni, E.; Scalapino, D. J.
2003-12-01
Using quantum Monte Carlo techniques, we study the effects of electronic correlations on the effective electron-phonon (el-ph) coupling in a two-dimensional one-band Hubbard model. We consider a momentum-independent bare ionic el-ph coupling. In the weak- and intermediate-correlation regimes, we find that the on-site Coulomb interaction U acts to effectively suppress the ionic el-ph coupling at all electron and phonon momenta. In this regime, our numerical simulations are in good agreement with the results of perturbation theory to order U2. However, entering the strong-correlation regime, we find that the forward-scattering process stops decreasing and begins to substantially increase as a function of U, leading to an effective el-ph coupling which is peaked in the forward direction. Whereas at weak and intermediate Coulomb interactions, screening is the dominant correlation effect suppressing the el-ph coupling, at larger U values irreducible vertex corrections become more important and give rise to this increase. These vertex corrections depend crucially on the renormalized electronic structure of the strongly correlated system.
Kang, Hye-Eun; Kim, Jung Nyun; Yoon, Tae-Ho; Park, Kyeong Dong; Park, Won Gyu; Park, Hyun; Kim, Hyun Woo
2016-07-01
We characterized the complete mitochondrial genome of Squilloides leptosquilla (Brooks, 1886) collected from the southern waters of Korea, which is newly recorded into the Korean carcinological fauna. The total mitochondrial genome length of S. leptosquilla was 16,376 bp. This circular DNA encodes 13 proteins, two ribosomal RNAs, and 22 transfer RNAs, as well as a putative control region. Compared with other decapod crustacean mitochondrial genomes, the overall A + T content was relatively high (71.1%) as those among other stomatopod species. Nine and four protein-coding genes are encoded on the H-strand and on the L-strand, respectively. The short non-coding region (210 bp) between tRNA(Glu) and tRNA(Phe) may be the good candidate as the molecular marker to discriminate S. leptosequilla from other stomatopods.
Meredith, Matthew M.; Parry, Erin M.; Guay, Justin A.; Markham, Nicholas O.; Danner, G. Russell; Johnson, Keith A.; Barkay, Tamar; Fekete, Frank A.
2013-01-01
Twenty-nine bacterial isolates representing eight genera from the gastrointestinal tracts of feral brook trout Salvelinus fontinalis (Mitchell) demonstrated multiple maximal antibiotic resistances and concomitant broad-spectrum mercury (Hg) resistance. Equivalent viable plate counts on tryptic soy agar supplemented with either 0 or 25 μM HgCl2 verified the ubiquity of mercury resistance in this microbial environment. Mercury levels in lake water samples measured 1.5 ng L−1; mercury concentrations in fish filets ranged from 81.8 to 1,080 ng g−1 and correlated with fish length. The presence of similar antibiotic and Hg resistance patterns in multiple genera of gastrointestinal microflora supports a growing body of research that multiple selective genes can be transferred horizontally in the presence of an unrelated individual selective pressure. We present data that bioaccumulation of non-point source Hg pollution could be a selective pressure to accumulate both antibiotic and Hg resistant bacteria. PMID:22850694
Incidence of pigmented skin tumors in a population of wild Montseny brook newt (Calotriton arnoldi).
Martínez-Silvestre, Albert; Amat, Fèlix; Bargalló, Ferran; Carranza, Salvador
2011-04-01
We report the presence of pigmented skin tumors in three populations of the endangered amphibian Montseny brook newt, Calotriton arnoldi, one of the European amphibian species with the smallest distribution range (40 km(2) in the Montseny Natural Park, Catalonia, Spain). Examination of one of the tumors by light microscopy was consistent with chromatophoroma and was most suggestive of a melanophoroma. Tumors were not found in juveniles. In adults, only two of three populations were affected. The proportions of males and females affected were not significantly different, but there was a positive correlation between body size and presence of tumors in both sexes. The etiology of chromatophoromas remains unknown but, in our study, they do not appear to have been caused by water quality or Ultraviolet B.
Directory of Open Access Journals (Sweden)
Kerry Heckenberg
2014-12-01
Full Text Available Much of the critical response to Brook Andrew’s reinterpretation of images from a colonial archive in his 2008 series The Island situated the work in a tradition of post-colonial critique of documentary images. But is this an adequate account of either Andrew’s work or the archive in question, William Blandowski’s Australien in 142 Photographischen Abbildungen (1862? This essay looks at practices involving copying and their impact on understandings of authenticity, the role of art in science, the nature of the observer and visual communication in relation to the broad scope of Blandowski’s archive, but particularly with regard to Andrew’s intervention in it. By examining the way that the past is brought into the present in the Island series, this essay seeks to facilitate a more richly nuanced understanding of these works that is cognizant of the historical issues involved.
Wright, J E; May, B; Stoneking, M; Lee, G M
1980-01-01
Electrophoretic variation involving three alleles is described for the duplicated loci for supernatant aspartate aminotransferase (AAT-1,2), from muscle extracts of brook trout. Both loci exhibit largely disomic inheritance. Exceptional progeny types are proposed to be the result of a form of tetrasomic inheritance. Nonrandom segregation was found among the progeny of males doubly heterozygous for AAT markers; where so-called linkage phase was known, this nonrandom assortment was shown to be pseudolinkage (78.9 percent recombination). Analyses of joint segregation of triply heterozygous males for the AAT-(1,2) loci and for the single alpha glycerophosphate dehydrogenase locus (AGP-1) revealed true linkage of AGP-1 with one AAT locus (mean r = 11 percent), but pseudolinkage with the other AAT locus (r = 74 percent). Intraindividual variation for homoeologous multivalent pairing of two acrocentric with two metacentric chromosomes in males, but with bivalent pairing in females, is proposed to account for pseudolinkage and for the tetrasomically inherited types.
Aeromonas cavernicola sp. nov., isolated from fresh water of a brook in a cavern.
Martínez-Murcia, Antonio; Beaz-Hidalgo, Roxana; Svec, Pavel; Saavedra, Ma José; Figueras, Ma José; Sedlacek, Ivo
2013-02-01
Aeromonas P2973 was isolated from the water of a brook in a cavern in the Czech Republic. This isolate could not be biochemically identified at the species level, considering all updated species descriptions. Subsequent extensive phenotypic characterisation, DNA-DNA hybridisation, 16S rRNA gene sequencing and a Multi-Locus Phylogenetic Analysis (MLPA) of the concatenated sequence of 7 housekeeping genes (gyrB, rpoD, recA, dnaJ, gyrA, dnaX and atpD; 4705 bp) was employed in an attempt to ascertain the taxonomy of this isolate. Based on this polyphasic approach, we describe a novel species of the genus Aeromonas, for which the name Aeromonas cavernicola sp. nov. is proposed, with strain CCM7641(T) (DSM24474(T), CECT7862(T)) as the type strain.
Jadamec, Margarete A.; Wallace, Wesley K.
2014-05-01
To gain insights into the processes governing the thrust-truncation of anticlines, we conducted a field study of the thrust-truncated folds in the remote Brooks Range of northern Alaska, where there is a transition in fold style from symmetric detachment folds to thrust-truncated asymmetric folds. In order to document the detailed geometry of the km-scale folds exposed in cliff-forming, largely inaccessible outcrops, a new surveying technique was developed that combines data from a theodolite and laser range finder. The field observations, survey profiles, and cross section reconstructions, indicate that late-stage thrust breakthrough of the anticlines within the mechanically competent Lisburne Group carbonates accommodated continued shortening when other mechanisms became unfeasible, including fold tightening, forelimb rotation, and parasitic folding in the anticline forelimbs. These results provide constraints on the processes that govern the transition from buckle folding to thrust truncation in fold-and-thrust belts worldwide.
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Marylène BOULET, Éric NORMANDEAU, Bérénice BOUGAS, Céline AUDET,Louis BERNATCHEZ
2012-02-01
Full Text Available Most salmonid taxa have an anadromous life history strategy, whereby fish migrate to saltwater habitats for a growth period before returning to freshwater habitats for spawning. Moreover, several species are characterized by different life history tactics whereby resident and anadromous forms may occur in genetically differentiated populations within a same species, as well as polymorphism within a population. The molecular mechanisms underlying the physiological differences between anadromous and resident forms during the first transition from freshwater to saltwater environments are only partially understood. Insofar research has typically focused on species of the genus Salmo. Here, using a 16,000 cDNA array, we tested the hypothesis that anadromous brook charr Salvelinus fontinalis are characterized by differences in their transcriptome relative to resident brook charr before the anadromous fish migration. Families originating from parapatric populations of anadromous and resident charr were reared in controlled environments mimicking natural temperature and photoperiod, and sampled in spring, while still in fresh water. While anadromous and resident charr showed similar transcriptome profiles in white muscle, they were characterized by striking differences in their gill transcriptome profiles. Genes that were upregulated in the gills of anadromous charr were principally involved in metabolism (mitochondrial electron transport chain, glucose metabolism, and protein synthesis, development (tissue differentiation and innate immunity. We discuss the nature of these transcriptomic differences in relation to molecular mechanisms underlying the expression of anadromous and resident life history tactics and suggest that the anadromous charr express some of the molecular processes present in other migratory salmonids [Current Zoology 58 (1: 158–170, 2012].
Institute of Scientific and Technical Information of China (English)
Marylène BOULET; (E)ric NORMANDEAU; Bérénice BOUGAS; Cé1ine AUDET; Louis BERNATCHEZ
2012-01-01
Most salmonid taxa have an anadromous life history strategy,whereby fish migrate to saltwater habitats for a growth period before returning to freshwater habitats for spawning.Moreover,several species are characterized by different life history tactics whereby resident and anadromous forms may occur in genetically differentiated populations within a same species,as well as polymorphism within a population.The molecular mechanisms underlying the physiological differences between anadromous and resident forms during the first transition from freshwater to saltwater environments are only partially understood.Insofar research has typically focused on species of the genus Salmo.Here,using a 16,000 cDNA array,we tested the hypothesis that anadromous brook charr Salvelinus fontinalis are characterized by differences in their transcriptome relative to resident brook charr before the anadromous fish migration.Families originating from parapatric populations of anadromous and resident charr were reared in controlled environments mimicking natural temperature and photoperiod,and sampled in spring,while still in fresh water.While anadromous and resident charr showed similar transcriptome profdes in white muscle,they were characterized by striking differences in their gill transcriptome profiles.Genes that were upregulated in the gills of anadromous charr were principally involved in metabolism (mitochondrial electron transport chain,glucose metabolism,and protein synthesis),development (tissue differentiation) and innate immunity.We discuss the nature of these transcriptomic differences in relation to molecular mechanisms underlying the expression of anadromous and resident life history tactics and suggest that the anadromous chart express some of the molecular processes present in other migratory salmonids [Current Zoology 58 (1):158-170,2012].
Effects of coal pile leachate on Taylor Brook in western Massachusetts
Energy Technology Data Exchange (ETDEWEB)
Tan, B.; Coler, R.A.
1986-01-01
The metals in Taylor Brook, a second-order stream that receives the runoff and leachate from a coal pile, were analyzed and evaluated for toxicity. Al, Fe and Mn levels were highest immediately downstream from the coal pile at site 4, where the pH was 4.9. The water at this site was soft (41 ppm). Ca and Mg were predominantly unbound, yet maximum binding with organic acids occurred. The increase in SO/sub 4/ concentrations (fourfold) and HCO/sub 3/:SO/sub 4/ ratios indicated little or no buffer capacity but the SO/sub 4/:NO/sub 3/:Cl ratios showed that the effect was local rather than a consequence of acid precipitation alone. The 96-h LC50 values for guppies in water from sites 4 and 3 were 26 and 100%, respectively. The increase of Al (80-fold) was inversely proportional to pH, but this proportionality was more pronounced at site 4 than at site 3. The 36-h LC50 values obtained on the addition of Al and acidity to water from site 3 at the levels measured in water from site 4 were 24% and greater than 100%, respectively. When compared with the values (17% and 49%) derived for site 4 water, the data indicate that the toxicity was principally exerted by aluminium. Residual oxygen data also suggest that fish mortality was primarily a function of Al. Additions of Al (0.3 ppm) to Taylor Brook control site water resulted in increased toxicity to guppies, while added acidity (pH 4.5) has no marked effect. 18 references.
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C. C. Brauer
2014-02-01
Full Text Available The Wageningen Lowland Runoff Simulator (WALRUS is a new parametric (conceptual rainfall-runoff model which accounts explicitly for processes that are important in lowland areas, such as groundwater-unsaturated zone coupling, wetness-dependent flowroutes, groundwater–surface water feedbacks, and seepage and surface water supply (see companion paper by Brauer et al., 2014. Lowland catchments can be divided into slightly sloping, freely draining catchments and flat polders with controlled water levels. Here, we apply WALRUS to two contrasting Dutch catchments: the Hupsel Brook catchment and Cabauw polder. In both catchments, WALRUS performs well: Nash–Sutcliffe efficiencies obtained after calibration on one year of discharge observations are 0.87 for the Hupsel Brook catchment and 0.83 for the Cabauw polder, with values of 0.74 and 0.76 for validation. The model also performs well during floods and droughts and can forecast the effect of control operations. Through the dynamic division between quick and slow flowroutes controlled by a wetness index, temporal and spatial variability in groundwater depths can be accounted for, which results in adequate simulation of discharge peaks as well as low flows. The performance of WALRUS is most sensitive to the parameter controlling the wetness index and the groundwater reservoir constant, and to a lesser extent to the quickflow reservoir constant. The effects of these three parameters can be identified in the discharge time series, which indicates that the model is not overparameterised (parsimonious. Forcing uncertainty was found to have a larger effect on modelled discharge than parameter uncertainty and uncertainty in initial conditions.
Changes in seasonal climate outpace compensatory density-dependence in eastern brook trout
Bassar, Ronald D.; Letcher, Benjamin H.; Nislow, Keith H.; Whiteley, Andrew R.
2016-01-01
Understanding how multiple extrinsic (density-independent) factors and intrinsic (density-dependent) mechanisms influence population dynamics has become increasingly urgent in the face of rapidly changing climates. It is particularly unclear how multiple extrinsic factors with contrasting effects among seasons are related to declines in population numbers and changes in mean body size and whether there is a strong role for density-dependence. The primary goal of this study was to identify the roles of seasonal variation in climate driven environmental direct effects (mean stream flow and temperature) versus density-dependence on population size and mean body size in eastern brook trout (Salvelinus fontinalis). We use data from a 10-year capture-mark-recapture study of eastern brook trout in four streams in Western Massachusetts, USA to parameterize a discrete-time population projection model. The model integrates matrix modeling techniques used to characterize discrete population structures (age, habitat type and season) with integral projection models (IPMs) that characterize demographic rates as continuous functions of organismal traits (in this case body size). Using both stochastic and deterministic analyses we show that decreases in population size are due to changes in stream flow and temperature and that these changes are larger than what can be compensated for through density-dependent responses. We also show that the declines are due mostly to increasing mean stream temperatures decreasing the survival of the youngest age class. In contrast, increases in mean body size over the same period are the result of indirect changes in density with a lesser direct role of climate-driven environmental change.
Brauer, C. C.; Torfs, P. J. J. F.; Teuling, A. J.; Uijlenhoet, R.
2014-10-01
The Wageningen Lowland Runoff Simulator (WALRUS) is a new parametric (conceptual) rainfall-runoff model which accounts explicitly for processes that are important in lowland areas, such as groundwater-unsaturated zone coupling, wetness-dependent flowroutes, groundwater-surface water feedbacks, and seepage and surface water supply (see companion paper by Brauer et al., 2014). Lowland catchments can be divided into slightly sloping, freely draining catchments and flat polders with controlled water levels. Here, we apply WALRUS to two contrasting Dutch catchments: the Hupsel Brook catchment and the Cabauw polder. In both catchments, WALRUS performs well: Nash-Sutcliffe efficiencies obtained after calibration on 1 year of discharge observations are 0.87 for the Hupsel Brook catchment and 0.83 for the Cabauw polder, with values of 0.74 and 0.76 for validation. The model also performs well during floods and droughts and can forecast the effect of control operations. Through the dynamic division between quick and slow flowroutes controlled by a wetness index, temporal and spatial variability in groundwater depths can be accounted for, which results in adequate simulation of discharge peaks as well as low flows. The performance of WALRUS is most sensitive to the parameter controlling the wetness index and the groundwater reservoir constant, and to a lesser extent to the quickflow reservoir constant. The effects of these three parameters can be identified in the discharge time series, which indicates that the model is not overparameterised (parsimonious). Forcing uncertainty was found to have a larger effect on modelled discharge than parameter uncertainty and uncertainty in initial conditions.
Brauer, C. C.; Torfs, P. J. J. F.; Teuling, A. J.; Uijlenhoet, R.
2014-02-01
The Wageningen Lowland Runoff Simulator (WALRUS) is a new parametric (conceptual) rainfall-runoff model which accounts explicitly for processes that are important in lowland areas, such as groundwater-unsaturated zone coupling, wetness-dependent flowroutes, groundwater-surface water feedbacks, and seepage and surface water supply (see companion paper by Brauer et al., 2014). Lowland catchments can be divided into slightly sloping, freely draining catchments and flat polders with controlled water levels. Here, we apply WALRUS to two contrasting Dutch catchments: the Hupsel Brook catchment and Cabauw polder. In both catchments, WALRUS performs well: Nash-Sutcliffe efficiencies obtained after calibration on one year of discharge observations are 0.87 for the Hupsel Brook catchment and 0.83 for the Cabauw polder, with values of 0.74 and 0.76 for validation. The model also performs well during floods and droughts and can forecast the effect of control operations. Through the dynamic division between quick and slow flowroutes controlled by a wetness index, temporal and spatial variability in groundwater depths can be accounted for, which results in adequate simulation of discharge peaks as well as low flows. The performance of WALRUS is most sensitive to the parameter controlling the wetness index and the groundwater reservoir constant, and to a lesser extent to the quickflow reservoir constant. The effects of these three parameters can be identified in the discharge time series, which indicates that the model is not overparameterised (parsimonious). Forcing uncertainty was found to have a larger effect on modelled discharge than parameter uncertainty and uncertainty in initial conditions.
Krimmer, A N; Paul, A J; Hontela, A; Rasmussen, J B
2011-09-01
This study presents an experimental analysis of the effects of midwinter flow reduction (50-75%, reduction in discharge in 4 h daily pulses) on the physical habitat and on behaviour and physiology of overwintering brook trout Salvelinus fontinalis in a small mountain stream. Flow reduction did not result in significant lowering of temperature or formation of surface or subsurface ice. The main findings were (1) daily movement by S. fontinalis increased (c. 2·5-fold) during flow reduction, but was limited to small-scale relocations (banks were the preferred habitat and availability of these habitats was reduced during flow reduction. (3) Although both experimental and reference fish did lose mass and condition during the experiment, no effects of flow reduction on stress indicators (blood cortisol or glucose) or bioenergetics (total body fat, water content or mass loss) were detected, probably because access to the preferred type of cover remained available. Like other salmonids, S. fontinalis moves little and seeks physical cover during winter. Unlike many of the more studied salmonids, however, this species overwinters successfully in small groundwater-rich streams that often remain ice-free, and this study identifies undercut banks as the critical winter habitat rather than substratum cover.
Ginzburg-Landau expansion in strongly disordered attractive Anderson-Hubbard model
Kuchinskii, E. Z.; Kuleeva, N. A.; Sadovskii, M. V.
2017-07-01
We have studied disordering effects on the coefficients of Ginzburg-Landau expansion in powers of superconducting order parameter in the attractive Anderson-Hubbard model within the generalized DMFT+Σ approximation. We consider the wide region of attractive potentials U from the weak coupling region, where superconductivity is described by BCS model, to the strong coupling region, where the superconducting transition is related with Bose-Einstein condensation (BEC) of compact Cooper pairs formed at temperatures essentially larger than the temperature of superconducting transition, and a wide range of disorder—from weak to strong, where the system is in the vicinity of Anderson transition. In the case of semielliptic bare density of states, disorder's influence upon the coefficients A and B of the square and the fourth power of the order parameter is universal for any value of electron correlation and is related only to the general disorder widening of the bare band (generalized Anderson theorem). Such universality is absent for the gradient term expansion coefficient C. In the usual theory of "dirty" superconductors, the C coefficient drops with the growth of disorder. In the limit of strong disorder in BCS limit, the coefficient C is very sensitive to the effects of Anderson localization, which lead to its further drop with disorder growth up to the region of the Anderson insulator. In the region of BCS-BEC crossover and in BEC limit, the coefficient C and all related physical properties are weakly dependent on disorder. In particular, this leads to relatively weak disorder dependence of both penetration depth and coherence lengths, as well as of related slope of the upper critical magnetic field at superconducting transition, in the region of very strong coupling.
Effective theory and emergent SU(2 ) symmetry in the flat bands of attractive Hubbard models
Tovmasyan, Murad; Peotta, Sebastiano; Törmä, Päivi; Huber, Sebastian D.
2016-12-01
In a partially filled flat Bloch band electrons do not have a well defined Fermi surface and hence the low-energy theory is not a Fermi liquid. Nevertheless, under the influence of an attractive interaction, a superconductor well described by the Bardeen-Cooper-Schrieffer (BCS) wave function can arise. Here we study the low-energy effective Hamiltonian of a generic Hubbard model with a flat band. We obtain an effective Hamiltonian for the flat band physics by eliminating higher-lying bands via the perturbative Schrieffer-Wolff transformation. At first order in the interaction energy we recover the usual procedure of projecting the interaction term onto the flat band Wannier functions. We show that the BCS wave function is the exact ground state of the projected interaction Hamiltonian, if a simple uniform pairing condition on the single-particle states is satisfied, and that the compressibility is diverging as a consequence of an emergent SU(2 ) symmetry. This symmetry is broken by second-order interband transitions resulting in a finite compressibility, which we illustrate for a one-dimensional ladder with two perfectly flat bands. These results motivate a further approximation leading to an effective ferromagnetic Heisenberg model. The gauge-invariant result for the superfluid weight of a flat band can be obtained from the ferromagnetic Heisenberg model only if the maximally localized Wannier functions in the Marzari-Vanderbilt sense are used. Finally, we prove an important inequality D ≥W2 between the Drude weight D and the winding number W , which guarantees ballistic transport for topologically nontrivial flat bands in one dimension.
Lu, Yongchuan; Wang, Chen
2016-10-01
We investigate the ground-state behavior of the Dicke-Hubbard model including counter-rotating terms. By generalizing an extended coherent-state approach within mean-field theory, we self-consistently obtain the ground-state energy and delocalized order parameter. Localization-delocalization quantum phase transition of photons is clearly observed by breaking the parity symmetry. Particularly, Mott lobes are fully suppressed, and the delocalized order parameter shows monotonic enhancement by increasing qubit-cavity coupling strength, in sharp contrast to the Dicke-Hubbard model under rotating-wave approximation. Moreover, the corresponding phase boundaries are stabilized by decreasing photon hopping strength, compared to the Rabi-Hubbard model.
Altmeyer, Michaela; Guterding, Daniel; Hirschfeld, P. J.; Maier, Thomas A.; Valentí, Roser; Scalapino, Douglas J.
2016-12-01
In the framework of a multiorbital Hubbard model description of superconductivity, a matrix formulation of the superconducting pairing interaction that has been widely used is designed to treat spin, charge, and orbital fluctuations within a random phase approximation (RPA). In terms of Feynman diagrams, this takes into account particle-hole ladder and bubble contributions as expected. It turns out, however, that this matrix formulation also generates additional terms which have the diagrammatic structure of vertex corrections. Here we examine these terms and discuss the relationship between the matrix-RPA superconducting pairing interaction and the Feynman diagrams that it sums.
Weak-coupling approach to the semi-infinite Hubbard model: Non-locality of the self-energy
Potthoff, M.; Nolting, W.
1997-01-01
The Hubbard model on a semi-infinite three-dimensional lattice is considered to investigate electron-correlation effects at single-crystal surfaces. The standard second-order perturbation theory in the interaction U is used to calculate the electronic self-energy and the quasi-particle density of states (QDOS) in the bulk as well as in the vicinity of the surface. Within a real-space representation we fully account for the non-locality of the self-energy and examine the quality of the local a...
Phase transitions in Bose-Fermi-Hubbard model in the heavy fermion limit: Hard-core boson approach
Directory of Open Access Journals (Sweden)
I.V. Stasyuk
2015-12-01
Full Text Available Phase transitions are investigated in the Bose-Fermi-Hubbard model in the mean field and hard-core boson approximations for the case of infinitely small fermion transfer and repulsive on-site boson-fermion interaction. The behavior of the Bose-Einstein condensate order parameter and grand canonical potential is analyzed as functions of the chemical potential of bosons at zero temperature. The possibility of change of order of the phase transition to the superfluid phase in the regime of fixed values of the chemical potentials of Bose- and Fermi-particles is established. The relevant phase diagrams are built.
Daley, P.; Wortis, R.
2016-05-01
Non-interacting systems with bounded disorder have been shown to exhibit sharp density of state peaks at the band edge which coincide with an energy range of abruptly suppressed localization. Recent work has shown that these features also occur in the presence of on-site interactions in ensembles of two-site Anderson-Hubbard systems at half filling. Here we demonstrate that this effect in interacting systems persists away from half filling, and moreover that energy regions with suppressed localization continue to appear in ensembles of larger systems despite a loss of sharp features in the density of states.
Large-U limit of a Hubbard model in a magnetic field: Chiral spin interactions and paramagnetism
Sen, Diptiman; Chitra, R.
1995-01-01
We consider the large-U limit of the one-band Hubbard model at half-filling on a nonbipartite two-dimensional lattice. An external magnetic field can induce a three-spin chiral interaction at order 1/U2. We discuss situations in which, at low temperatures, the chiral term may have a larger effect than the Pauli coupling of electron spins to a magnetic field. We present a model that explicitly demonstrates this. The ground state is a singlet with a gap; hence the spin susceptibility is zero while the chiral susceptibility is finite and paramagnetic.
Institute of Scientific and Technical Information of China (English)
王为忠; 姚凯伦
2002-01-01
Using an exact diagonalization method, we study an extended Hubbard model with an electron-lattice interaction for an organic ferromagnetic chain with radical coupling. The result shows that the ferromagnetic ground state originates from the antiferromagnetic correlation between adjoining sites, which is enhanced by the on-site e-e repulsion. The intersite e-e repulsion induces the inhomogeneous distribution of the charge density. The dimerization is decreased by the e-e interaction and the radical coupling. The electron--lattice interaction and the radical coupling can transfer the spin density and charge density between the main chain and the radicals.
Striker, Lora K.; Ivanoff, Michael A.
1997-01-01
This report provides the results of a detailed Level II analysis of scour potential at structure WALDTH00180022 on Town Highway 18 crossing Coles Brook also known as Joes Brook, Walden, Vermont (figures 1–8). A Level II study is a basic engineering analysis of the site, including a quantitative analysis of stream stability and scour (U.S. Department of Transportation, 1993). Results of a Level I scour investigation also are included in Appendix E of this report. A Level I investigation provides a qualitative geomorphic characterization of the study site. Information on the bridge, gleaned from Vermont Agency of Transportation (VTAOT) files, was compiled prior to conducting Level I and Level II analyses and is found in Appendix D.
Kurashige, Y.; Nakano, T.; Kasubuchi, E.; Maruo, M.; Domitsu, H.
2015-03-01
The river mouth of Kitagawa Brook is normally stagnant because it is easily closed by sand and gravel transported by littoral currents of Biwa Lake, Japan. A new urban area exists in the basin and sewerage works were constructed in the early 1990s, so contaminated water with a bad odour had flowed into the brook before the sewerage works. To reduce the smell, the river mouth was excavated to narrow the channel in the early 1980s. Thus, river-bed sediment after this excavation only occurs at the river mouth. From the upper 24 cm of a sediment core, we found 19 strata of leaves which were supplied from deciduous trees in autumn. We also found several gravel layers which were supplied from the lake during severe storms. The combination of veins and gravel layers were reconstructed for about 20 years of sediment records with an error of two to three years.
Kanno, Yoichiro; Vokoun, Jason C.; Letcher, Benjamin H.
2011-01-01
Brook trout Salvelinus fontinalis populations have declined in much of the native range in eastern North America and populations are typically relegated to small headwater streams in Connecticut, USA. We used sibship reconstruction to infer mating systems, dispersal and effective population size of resident (non-anadromous) brook trout in two headwater stream channel networks in Connecticut. Brook trout were captured via backpack electrofishing using spatially continuous sampling in the two headwaters (channel network lengths of 4.4 and 7.7 km). Eight microsatellite loci were genotyped in a total of 740 individuals (80–140 mm) subsampled in a stratified random design from all 50 m-reaches in which trout were captured. Sibship reconstruction indicated that males and females were both mostly polygamous although single pair matings were also inferred. Breeder sex ratio was inferred to be nearly 1:1. Few large-sized fullsib families (>3 individuals) were inferred and the majority of individuals were inferred to have no fullsibs among those fish genotyped (family size = 1). The median stream channel distance between pairs of individuals belonging to the same large-sized fullsib families (>3 individuals) was 100 m (range: 0–1,850 m) and 250 m (range: 0–2,350 m) in the two study sites, indicating limited dispersal at least for the size class of individuals analyzed. Using a sibship assignment method, the effective population size for the two streams was estimated at 91 (95%CI: 67–123) and 210 (95%CI: 172–259), corresponding to the ratio of effective-to-census population size of 0.06 and 0.12, respectively. Both-sex polygamy, low variation in reproductive success, and a balanced sex ratio may help maintain genetic diversity of brook trout populations with small breeder sizes persisting in headwater channel networks.
Doppler, Tobias; Lück, Alfred; Popow, Gabriel; Strahm, Ivo; Winiger, Luca; Gaj, Marcel; Singer, Heinz; Stamm, Christian
2010-05-01
Soil applied herbicides can be transported from their point of application (agricultural field) to surface waters during rain events. There they can have harmful effects on aquatic species. Since the spatial distribution of mobilization and transport processes is very heterogeneous, the contributions of different fields to the total load in a surface water body may differ considerably. The localization of especially critical areas (contributing areas) can help to efficiently minimize herbicide inputs to surface waters. An agricultural field becomes a contributing area when three conditions are met: 1) herbicides are applied, 2) herbicides are mobilized on the field and 3) the mobilized herbicides are transported rapidly to the surface water. In spring 2009, a controlled herbicide application was performed on corn fields in a small (ca 1 km2) catchment with intensive crop production in the Swiss plateau. Subsequently water samples were taken at different locations in the catchment with a high temporal resolution during rain events. We observed both saturation excess and hortonian overland flow during the field campaign. Both can be important mobilization processes depending on the intensity and quantity of the rain. This can lead to different contributing areas during different types of rain events. We will show data on the spatial distribution of herbicide loads during different types of rain events. Also the connectivity of the fields with the brook is spatially heterogeneous. Most of the fields are disconnected from the brook by internal sinks in the catchment, which prevents surface runoff from entering the brook directly. Surface runoff from these disconnected areas can only enter the brook rapidly via macropore-flow into tile drains beneath the internal sinks or via direct shortcuts to the drainage system (maintenance manholes, farmyard or road drains). We will show spatially distributed data on herbicide concentration in purely subsurface systems which shows
Energy Technology Data Exchange (ETDEWEB)
Proville, L
1998-03-30
This thesis brings its contribution to the bipolaronic theory which might explain the origin of superconductivity at high temperature. A polaron is a quasiparticle made up of a localized electron and a deformation in the crystal structure. 2 electrons in singlet states localized on the same site form a bipolaron. Whenever the Coulomb repulsion between the 2 electrons is too strong bipolaron turns into 2 no bound polarons. We study the existence and the mobility of bipolarons. We describe the electron-phonon interaction by the Holstein term and the Coulomb repulsion by the Hubbard term. 2 assumptions are made: - the local electron-phonon interaction is strong and opposes the Coulomb repulsion between Hubbard type electrons - the system is close to the adiabatic limit. The system is reduced to 2 electrons in order to allow an exact treatment and the investigation of some bipolaronic bound states. At 2-dimensions the existence of bipolarons requires a very strong coupling which forbids any classical mobility. In some cases an important tunneling effect appears and we show that mobile bipolarons exist in a particular parameter range. Near the adiabatic limit we prove that polaronic and bipolaronic structures exist for a great number of electrons. (A.C.) 33 refs.
Can brook trout survive climate change in large rivers? If it rains.
Merriam, Eric R; Fernandez, Rodrigo; Petty, J Todd; Zegre, Nicolas
2017-12-31
We provide an assessment of thermal characteristics and climate change vulnerability for brook trout (Salvelinus fontinalis) habitats in the upper Shavers Fork sub-watershed, West Virginia. Spatial and temporal (2001-2015) variability in observed summer (6/1-8/31) stream temperatures was quantified in 23 (9 tributary, 14 main-stem) reaches. We developed a mixed effects model to predict site-specific mean daily stream temperature from air temperature and discharge and coupled this model with a hydrologic model to predict future (2016-2100) changes in stream temperature under low (RCP 4.5) and high (RCP 8.5) emissions scenarios. Observed mean daily stream temperature exceeded the 21°C brook trout physiological threshold in all but one main-stem site, and 3 sites exceeded proposed thermal limits for either 63- and 7-day mean stream temperature. We modeled mean daily stream temperature with a high degree of certainty (R(2)=0.93; RMSE=0.76°C). Predicted increases in mean daily stream temperature in main-stem and tributary reaches ranged from 0.2°C (RCP 4.5) to 1.2°C (RCP 8.5). Between 2091 and 2100, the average number of days with mean daily stream temperature>21°C increased within main-stem sites under the RCP 4.5 (0-1.2days) and 8.5 (0-13) scenarios; however, no site is expected to exceed 63- or 7-day thermal limits. During the warmest 10years, ≥5 main-stem sites exceeded the 63- or 7-day thermal tolerance limits under both climate emissions scenarios. Years with the greatest increases in stream temperature were characterized by low mean daily discharge. Main-stem reaches below major tributaries never exceed thermal limits, despite neighboring reaches having among the highest observed and predicted stream temperatures. Persistence of thermal refugia within upper Shavers Fork would enable persistence of metapopulation structure and life history processes. However, this will only be possible if projected increases in discharge are realized and offset expected
Energy Technology Data Exchange (ETDEWEB)
Wallace, W.K.; Hanks, C.L.
1988-01-01
The structural style of the range-front region of the northeastern Brooks Range in Arctic National Wildlife Refuge (ANWR) is strongly controlled by (1) the existence of detachment horizons in both pre-Mississippian rocks and the unconformably overlying Mississippian to Lower Cretaceous cover sequence, and (2) lithology and structural competency of the pre-Mississippian rocks. These variables strongly influence lateral changes in structural style. The Brooks Range of northwestern ANWR is dominated by a series of narrow linear anticlinoria, whereas in northeastern ANWR the Brooks Range is characterized by only two broad and strongly arcuate anticlinoria. In both areas, the anticlinoria are controlled by the geometry of a duplex bounded by a floor thrust in pre-Mississippian rocks and a roof thrust in the Kayak Shale, near the base of the cover sequence. In the west, where the pre-Mississippian partially consists of structurally competent carbonates, each anticlinorium marks a single horse in the duplex. However, in the east, pre-Mississippian rocks are relatively incompetent and each anticlinorium is cored by multiple horses. In the west, shortening above the roof thrust is by detachment folding, except where the shale detachment horizon is depositionally absent. In contrast, in eastern ANWR shortening above the roof thrust is by major thrust duplication of the entire cover sequence, perhaps due to lithology and thickness changes within the detachment horizon.
Storck, D.A.; Lacombe, Pierre
1996-01-01
This report presents the results of a study designed to determine whether Green Pond Brook and its tributaries contain contaminated streambed sediments and to characterize the quaity of water in the brook. Results of previous investigations at Picatinny Arsenal, Morris County, New Jersey, indicate that significant contamination of ground water, surface water, and soil is present at the arsenal. Forty-five streambed-material samples were collected for analysis to determine whether contaminants have migrated to the brook from the surrounding area. Samples were analyzed for trace elements, base/neutral- and acid-etractable compounds, insecticides, and other constituents. Results of an electromagnetic-conductivity and natural-gamma-ray survey were used to describe the distribution of particle sizes in streambed and substreambed sediments. Historical results of analyses of streambed-material and surface-water samples also are presented. Samples of streambed material from three areas in Green Pond Brook and its tributaries contained organic and (or) inorganic constituents in concentrations greater than those typically found at the arsenal. These areas are Green Pond Brook, from the area near the outflow of Picatinny Lake downstream to Farley Avenue; Bear Swamp Brook, from the area near building 241 downstream to the confluence with Green Pond Brook; and Green Pond Brook, from the open burning area downstream to the dam near building 1178. Contaminants identified include trace elements, polynuclear aromatic hydrocarbons, polychlorinated biphenyls, and organochlorine insecticides. Surface water in Green Pond Brook contained several volatile organic compounds, including trichloroethylene, tetrachloroethylene, and 1,2-dichloroethylene, at maximum concen- trations of 3.8, 4.6, and 11 micrograms per liter, respectively. Volatilization is expected to remove volatile organic compounds in the steep, fast- flowing reaches of the brook. No organic or inorganic constituents were
Formation of Hubbard-like bands as a fingerprint of strong electron-electron interactions in FeSe
Watson, Matthew D.; Backes, Steffen; Haghighirad, Amir A.; Hoesch, Moritz; Kim, Timur K.; Coldea, Amalia I.; Valentí, Roser
2017-02-01
We use angle-resolved photoemission spectroscopy (ARPES) to explore the electronic structure of single crystals of FeSe over a wide range of binding energies and study the effects of strong electron-electron correlations. We provide evidence for the existence of "Hubbard-like bands" at high binding energies consisting of incoherent many-body excitations originating from Fe 3 d states in addition to the renormalized quasiparticle bands near the Fermi level. Many high-energy features of the observed ARPES data can be accounted for when incorporating the effects of strong local Coulomb interactions in calculations of the spectral function via dynamical mean-field theory, including the formation of a Hubbard-like band. This shows that over the energy scale of several eV, local correlations arising from the on-site Coulomb repulsion and Hund's coupling are essential for a proper understanding of the electronic structure of FeSe and other related iron-based superconductors.
Chung, Chung-Hou; Lee, Der-Hau; Chao, Sung-Po
2014-07-01
We study the quantum phases and phase transitions of the Kane-Mele Hubbard (KMH) model on a zigzag ribbon of honeycomb lattice at a finite size via the weak-coupling renormalization group (RG) approach. In the noninteracting limit, the Kane-Mele (KM) model is known to support topological edge states where electrons show helical property with orientations of the spin and momentum being locked. The effective interedge hopping terms are generated due to finite-size effect. In the presence of an on-site Coulomb (Hubbard) interaction and the interedge hoppings, special focus is put on the stability of the topological edge states (TI phase) in the KMH model against (i) the charge and spin gaped (II) phase, (ii) the charge gaped but spin gapless (IC) phase, and (iii) the spin gaped but charge gapless (CI) phase depending on the number (even/odd) of the zigzag ribbons, doping level (electron filling factor) and the ratio of the Coulomb interaction to the interedge tunneling. We discuss different phase diagrams for even and odd numbers of zigzag ribbons. We find the TI-CI, II-IC, and II-CI quantum phase transitions are of the Kosterlitz-Thouless (KT) type. By computing various correlation functions, we further analyze the nature and leading instabilities of these phases. The relevance of our results for graphene is discussed.
Qin, Mingpu; Zhang, Shiwei
2016-01-01
Ground state properties of the Hubbard model on a two-dimensional square lattice are studied by the auxiliary-field quantum Monte Carlo method. Accurate results for energy, double occupancy, effective hopping, magnetization, and momentum distribution are calculated for interaction strengths of U/t from 2 to 8, for a range of densities including half-filling and n = 0.3, 0.5, 0.6, 0.75, and 0.875. At half-filling, the results are numerically exact. Away from half-filling, the constrained path Monte Carlo method is employed to control the sign problem. Our results are obtained with several advances in the computational algorithm, which are described in detail. We discuss the advantages of generalized Hartree-Fock trial wave functions and its connection to pairing wave functions, as well as the interplay with different forms of Hubbard-Stratonovich decompositions. We study the use of different twist angle sets when applying the twist averaged boundary conditions. We propose the use of quasi-random sequences, whi...
Lawson, D. E.; Gulick, S. P. S.; Goff, J. A.
2015-12-01
Hubbard Glacier has been steadily advancing into tidewater > 200 years; advance over last 40 years has averaged ~34 m/yr, although at spatially variable rates across the terminus (14-80 m/yr) and with a seasonal advance and retreat cycle of ~100 m to 300 m, but as much as 600 m. The advance of the terminus is synchronous with the movement of the morainal bank that underlies it. The mechanics of this motion and the related sedimentological processes responsible for this coordinated advance of the grounding line are based largely on inferences from geophysical surveys of remnant morainal banks. In situ and repeated observations of the submarine margin are required to improve our understanding of how the terminus advances into deep fjords. We conducted initial submarine observations using a Bluefin 9M AUV (Autonomous Underwater Vehicle) and acquired high-resolution swath bathymetry and sidescan backscatter along a ~2 km long section of the ice face of the glacier. Onboard oceanographic measurements and surface CTD casts were obtained during AUV deployment. Decimeter-scale imagery of the seabed reveals numerous erosional and depositional bedforms and gravitational features next to the ice face and down the morainal bank's proximal slope. The moraine surface adjacent to the ice face is coarse, apparently swept clear of finer materials, exhibits gravel stripes and boulder lags. The slope into the fjord displays a sequence of bedforms from barchan-shaped dunes up to 15 m on a side to barchanoid transverse ridges >50 m long to transverse ridges >100 m long. This transition implies increased sand supply to the bed downslope. Channels, erosional gullies and scours cross the upper slope, while localized slump and flow failures occur sporadically across the face. We speculate that high concentration bottom flows originating from turbulent subglacial discharge are likely processes creating the barchan forms and that the flow velocity reduces with distance from the grounding
Le modele de Hubbard bidimensionnel a faible couplage: Thermodynamique et phenomenes critiques
Roy, Sebastien
Une etude systematique du modele de Hubbard en deux dimensions a faible couplage a l'aide de la theorie Auto-Coherente a Deux Particules (ACDP) dans le diagramme temperature-dopage-interaction-sauts permet de mettre en evidence l'influence des fluctuations magnetiques sur les proprietes thermodynamiques du systeme electronique sur reseau. Le regime classique renormalise a temperature finie pres du dopage nul est marque par la grandeur de la longueur de correlation de spin comparee a la longueur thermique de de Broglie et est caracterisee par un accroissement drastique de la longueur de correlation de spin. Cette croissance exponentielle a dopage nul marque la presence d'un pic de chaleur specifique en fonction de la temperature a basse temperature. Une temperature de crossover est alors associee a la temperature a laquelle la longueur de correlation de spin est egale a la longueur thermique de de Broglie. C'est a cette temperature caracteristique, ou est observee l'ouverture du pseudogap dans le poids spectral, que se situe le maximum du pic de chaleur specifique. La presence de ce pic a des consequences sur l'evolution du potentiel chimique avec le dopage lorsque l'uniformite thermodynamique est respectee. Les contraintes imposees par les lois de la thermodynamique font en sorte que l'evolution du potentiel chimique avec le dopage est non triviale. On demontre entre autres que le potentiel chimique est proportionnel a la double occupation qui est reliee au moment local. Par ailleurs, une derivation de la fonction de mise a l'echelle de la susceptibilite de spin a frequence nulle au voisinage d'un point critique marque sans equivoque la presence d'un point critique quantique en dopage pour une valeur donnee de l'interaction. Ce point critique, associe a une transition de phase magnetique en fonction du dopage a temperature nulle, induit un comportement non trivial sur les proprietes physiques du systeme a temperature finie. L'approche quantitative ACDP permet de
Transport and optical conductivity in the Hubbard model: A high-temperature expansion perspective
Perepelitsky, Edward; Galatas, Andrew; Mravlje, Jernej; Žitko, Rok; Khatami, Ehsan; Shastry, B. Sriram; Georges, Antoine
2016-12-01
We derive analytical expressions for the spectral moments of the dynamical response functions of the Hubbard model using the high-temperature series expansion. We consider generic dimension d as well as the infinite-d limit, arbitrary electron density n , and both finite and infinite repulsion U . We use moment-reconstruction methods to obtain the one-electron spectral function, the self-energy, and the optical conductivity. They are all smooth functions at high temperature and, at large U , they are featureless with characteristic widths of the order of the lattice hopping parameter t . In the infinite-d limit, we compare the series expansion results with accurate numerical renormalization group and interaction expansion quantum Monte Carlo results. We find excellent agreement down to surprisingly low temperatures, throughout most of the bad-metal regime, which applies for T ≳(1 -n )D , the Brinkman-Rice scale. The resistivity increases linearly in T at high temperature without saturation. This results from the 1 /T behavior of the compressibility or kinetic energy, which play the role of the effective carrier number. In contrast, the scattering time (or diffusion constant) saturates at high T . We find that σ (n ,T )≈(1 -n )σ (n =0 ,T ) to a very good approximation for all n , with σ (n =0 ,T )∝t /T at high temperatures. The saturation at small n occurs due to a compensation between the density dependence of the effective number of carriers and that of the scattering time. The T dependence of the resistivity displays a kneelike feature which signals a crossover to the intermediate-temperature regime where the diffusion constant (or scattering time) starts increasing with decreasing T . At high temperatures, the thermopower obeys the Heikes formula, while the Wiedemann-Franz law is violated with the Lorenz number vanishing as 1 /T2 . The relevance of our calculations to experiments probing high-temperature transport in materials with strong electronic
Directory of Open Access Journals (Sweden)
Quentin Rougemont
2016-04-01
Full Text Available Inferring the history of isolation and gene flow during species divergence is a central question in evolutionary biology. The European river lamprey (Lampetra fluviatilis and brook lamprey (L. planeri show a low reproductive isolation but have highly distinct life histories, the former being parasitic-anadromous and the latter non-parasitic and freshwater resident. Here we used microsatellite data from six replicated population pairs to reconstruct their history of divergence using an approximate Bayesian computation framework combined with a random forest model. In most population pairs, scenarios of divergence with recent isolation were outcompeted by scenarios proposing ongoing gene flow, namely the Secondary Contact (SC and Isolation with Migration (IM models. The estimation of demographic parameters under the SC model indicated a time of secondary contact close to the time of speciation, explaining why SC and IM models could not be discriminated. In case of an ancient secondary contact, the historical signal of divergence is lost and neutral markers converge to the same equilibrium as under the less parameterized model allowing ongoing gene flow. Our results imply that models of secondary contacts should be systematically compared to models of divergence with gene flow; given the difficulty to discriminate among these models, we suggest that genome-wide data are needed to adequately reconstruct divergence history.
Energy Technology Data Exchange (ETDEWEB)
James R. Webb; Bernard J. Cosby; Frank A. Deviney, Jr.; James N. Galloway; Suzanne W. Maben; Arthur J. Bulger [University of Virginia, Charlottesville, VA (United States). Department of Environmental Sciences
2004-08-01
Streamwater composition data obtained through periodic sampling of streams that support brook trout (Salvelinus fontinalis) in the mountains of western Virginia were examined for evidence of recovery from acidification during the 1988-2001 period. Measurements of sulfate deposition in precipitation indicate that sulfate deposition in the region declined approximately 40% between 1985 and 2000. While no significant regional trends in acid-base constituents were observed for the set (n = 65) of western Virginia study streams, significant regional trends were observed for a subset (n = 14) of streams in Shenandoah National Park (SNP). For the subset of SNP streams, the median increase in acid-neutralizing capacity (ANC) was 0.168 {mu} equiv L{sup -1} year{sup -1} and the median decrease in sulfate concentration was -0.229 {mu}equiv L{sup -1} year{sup -1}. Although these trends are consistent with recovery from acidification, the degree of apparent recovery is small compared to estimates of historic acidification in SNP streams and much less than observed in other, more northern regions in the United States. Correlation between sulfate concentration trends and current sulfate concentrations in streamwater suggests that recovery from stream acidification in the western Virginia region is determined by sulfur retention processes in watershed soils. A transient increase in nitrate concentrations that occurred among some western Virginia streams following forest defoliation by the gypsy moth (Lymantria dispar) complicates interpretation of the observed patterns of change in acid-base status. 28 refs., 6 figs., 1 tab.
Can personality predict individual differences in brook trout spatial learning ability?
White, S L; Wagner, T; Gowan, C; Braithwaite, V A
2017-08-01
While differences in individual personality are common in animal populations, understanding the ecological significance of variation has not yet been resolved. Evidence suggests that personality may influence learning and memory; a finding that could improve our understanding of the evolutionary processes that produce and maintain intraspecific behavioural heterogeneity. Here, we tested whether boldness, the most studied personality trait in fish, could predict learning ability in brook trout. After quantifying boldness, fish were trained to find a hidden food patch in a maze environment. Stable landmark cues were provided to indicate the location of food and, at the conclusion of training, cues were rearranged to test for learning. There was a negative relationship between boldness and learning as shy fish were increasingly more successful at navigating the maze and locating food during training trials compared to bold fish. In the altered testing environment, only shy fish continued using cues to search for food. Overall, the learning rate of bold fish was found to be lower than that of shy fish for several metrics suggesting that personality could have widespread effects on behaviour. Because learning can increase plasticity to environmental change, these results have significant implications for fish conservation. Copyright © 2016 Elsevier B.V. All rights reserved.
Hiding in Plain Sight: A Case for Cryptic Metapopulations in Brook Trout (Salvelinus fontinalis.
Directory of Open Access Journals (Sweden)
David C Kazyak
Full Text Available A fundamental issue in the management and conservation of biodiversity is how to define a population. Spatially contiguous fish occupying a stream network have often been considered to represent a single, homogenous population. However, they may also represent multiple discrete populations, a single population with genetic isolation-by-distance, or a metapopulation. We used microsatellite DNA and a large-scale mark-recapture study to assess population structure in a spatially contiguous sample of Brook Trout (Salvelinus fontinalis, a species of conservation concern. We found evidence for limited genetic exchange across small spatial scales and in the absence of barriers to physical movement. Mark-recapture and stationary passive integrated transponder antenna records demonstrated that fish from two tributaries very seldom moved into the opposite tributary, but movements between the tributaries and mainstem were more common. Using Bayesian genetic clustering, we identified two genetic groups that exhibited significantly different growth rates over three years of study, yet survival rates were very similar. Our study highlights the importance of considering the possibility of multiple genetically distinct populations occurring within spatially contiguous habitats, and suggests the existence of a cryptic metapopulation: a spatially continuous distribution of organisms exhibiting metapopulation-like behaviors.
Evans, Richard K.; Hill, Gerald M.
2014-01-01
Very large space environment test facilities present unique engineering challenges in the design of facility data systems. Data systems of this scale must be versatile enough to meet the wide range of data acquisition and measurement requirements from a diverse set of customers and test programs, but also must minimize design changes to maintain reliability and serviceability. This paper presents an overview of the common architecture and capabilities of the facility data acquisition systems available at two of the world's largest space environment test facilities located at the NASA Glenn Research Center's Plum Brook Station in Sandusky, Ohio; namely, the Space Propulsion Research Facility (commonly known as the B-2 facility) and the Space Power Facility (SPF). The common architecture of the data systems is presented along with details on system scalability and efficient measurement systems analysis and verification. The architecture highlights a modular design, which utilizes fully-remotely managed components, enabling the data systems to be highly configurable and support multiple test locations with a wide-range of measurement types and very large system channel counts.
NASA Plum Brook's B-2 test facility-Thermal vacuum and propellant test facility
Kudlac, Maureen; Weaver, Harold; Cmar, Mark
2012-06-01
The National Aeronautics and Space Administration (NASA) Glenn Research Center (GRC) Plum Brook Station (PBS) Spacecraft Propulsion Research Facility, commonly referred to as B-2, is NASA's third largest thermal vacuum facility. It is the largest designed to store and transfer large quantities of liquid hydrogen and liquid oxygen, and is perfectly suited to support developmental testing of upper stage chemical propulsion systems as well as fully integrated stages. The facility is also capable of providing thermal-vacuum simulation services to support testing of large lightweight structures, Cryogenic Fluid Management (CFM) systems, electric propulsion test programs, and other In-Space propulsion programs. A recently completed integrated system test demonstrated the refurbished thermal vacuum capabilities of the facility. The test used the modernized data acquisition and control system to monitor the facility. The heat sink provided a uniform temperature environment of approximately 77K. The modernized infrared lamp array produced a nominal heat flux of 1.4 kW/m2. With the lamp array and heat sink operating simultaneously, the thermal systems produced a heat flux pattern simulating radiation to space on one surface and solar exposure on the other surface.
NASA Plum Brook's B-2 Test Facility: Thermal Vacuum and Propellant Test Facility
Kudlac, Maureen T.; Weaver, Harold F.; Cmar, Mark D.
2012-01-01
The National Aeronautics and Space Administration (NASA) Glenn Research Center (GRC) Plum Brook Station (PBS) Spacecraft Propulsion Research Facility, commonly referred to as B-2, is NASA's third largest thermal vacuum facility. It is the largest designed to store and transfer large quantities of liquid hydrogen and liquid oxygen, and is perfectly suited to support developmental testing of upper stage chemical propulsion systems as well as fully integrated stages. The facility is also capable of providing thermal-vacuum simulation services to support testing of large lightweight structures, Cryogenic Fluid Management (CFM) systems, electric propulsion test programs, and other In-Space propulsion programs. A recently completed integrated system test demonstrated the refurbished thermal vacuum capabilities of the facility. The test used the modernized data acquisition and control system to monitor the facility. The heat sink provided a uniform temperature environment of approximately 77 K. The modernized infrared lamp array produced a nominal heat flux of 1.4 kW/sq m. With the lamp array and heat sink operating simultaneously, the thermal systems produced a heat flux pattern simulating radiation to space on one surface and solar exposure on the other surface.
Lateral continuity of the Blarney Creek Thrust, Doonerak Windown, Central Brooks Range, Alaska
Energy Technology Data Exchange (ETDEWEB)
Seidensticker, C.M.; Julian, F.E.; Phelps, J.C.; Oldow, J.S.; Avellemant, H.G.
1985-04-01
The contact between Carboniferous and lower Paleozoic rocks, exposed along the northern margin of the Doonerak window in the central Brooks Range, is a major thrust fault called the Blarney Creek thrust (BCT). The BCT has been traced over a distance of 25 km, from Falsoola Mountain to Wien Mountain. The tectonic nature of this contact is demonstrated by: (1) omission of stratigraphic units above and below the BCT; (2) large angular discordance in orientation of first-generation cleavage at the BCT; (3) numerous thrust imbricates developed in the upper-plate Carboniferous section that sole into the BCT; and (4) truncation of an upper-plate graben structure at the BCT. Lack of evidence for pre-Carboniferous deformation in the lower plate casts doubt on the interpretation of the contact as an angular unconformity. However, the localized presence below the BCT of Mississippian Kekiktuk Conglomerate and Kayak Shale, in apparent depositional contact with lower Paleozoic rocks, suggests that the BCT follows an originally disconformable contact between the Carboniferous and lower Paleozoic rocks. The juxtaposition of younger over older rocks at the BCT is explained by calling upon the BCT to act as the upper detachment surface of a duplex structure. Duplex development involves initial imbrication of the Carboniferous section using the BCT as a basal decollement, followed by formation of deeper thrusts in the lower Paleozoic section, which ramp up and merge into the BCT.
Flow path studies in forested watersheds of heatwater tributaries of Brush Brook, Vermont
Ross, Donald S.; Bartlett, Richmond J.; Magdoff, Frederick R.; Walsh, Gregory J.
1994-09-01
An investigation was undertaken into how headwater tributaries of Brush Brook, Vermont, could have average pH differences of almost two units (4.75 and 6.7). Sampling along four tributaries revealed that most of one tributary, below an area of seeps, had consistently higher pH, Ca2+, Mg2+, and K+, and lower Al than other sites. Bedrock mapping showed numerous fractures in vicinity of the seeps. A portion of this tributary's watershed and a portion of an acid tributary's watershed were intensively mapped for soil depth. Sampling showed the widespread existence of dense basal till in the watershed of the acid tributary but none in that of the near-neutral stream. Lateral flow, found above the dense till, was chemically similar to that of the acid tributary and to solutions sampled from soil B horizons. There were no differences in the average pH of nonseep soils sampled from either watershed. Flow paths are hypothesized to be through the B horizons in the acid tributaries and from below the soil profile in the near-neutral tributary. The acid catchment should be more sensitive to environmental change.
Analysis of reinjection problems at the Stony Brook ATES field test site
Supkow, D. J.; Shultz, J. A.
1982-12-01
Aquifer Thermal Energy Storage (ATES) is one of several energy storage technologies being investigated by the DOE to determine the feasibility of reducing energy consumption by means of energy management systems. The State University of New York, (SUNY) Stony Brook, Long Island, New York site was selected by Battelle PNL for a Phase 1 investigation to determine the feasibility of an ATES demonstration to seasonally store chill energy by injecting chilled water in the winter and recovering it at a maximum rate of 100 MBTU/hr (30 MW) in the summer. The Phase 1 study was performed during 1981 by Dames & Moore under subcontract to Batelle PLN. The pumping and injection tests were performed using two wells in a doublet configuration. Well PI-1 is a previously existing well and PI-2 was installed specifically for this investigation. Both wells are screened in the Upper Magothy aquifer from approximately 300 to 350 feet below ground surface. Nine observation wells were also installed as a portion of the investigation to monitor water level and aquifer temperature changes during the test.
Rombach, C.S.; Layer, P.W.
2004-01-01
A compilation of published geochronology of rocks and minerals from the western and central Brooks Range provides a framework for understanding the complex history of the Brooks Range and northern Alaska. A simplified timeline of events comprises (1) Devonian extension, (2) Mississippian extension and Zn-Pb-Ag mineralization, (3) a passive interval, (4) pre-Brooks Range orogeny rock-formation and thermal event, (5) inception of Brooks Range orogeny, (6) exhumation and the end of main-stage deformation, and (7) subsequent episodic deformation. This compilation is supplemented by new 40Ar/39Ar dates of white mica from the Anarraaq and Red Dog Zn-Pb-Ag (+ barite) deposits from the western Brooks Range. The deposits are hosted in black shale and carbonate rocks of the Late Mississippian-Early Pennsylvanian Kuna Formation. Quartz-pyrite-white mica grains in sedimentary rocks above the Anarraaq deposit yield an age of 195.0 ?? 2.0 Ma, and paragenetically late quartz-pyrite-white mica from the Main orebody at the Red Dog deposit has an age of 126.1 ?? 0.7 Ma. These white micas are much younger than the age of Zn-Pb-Ag mineralization at Red Dog (338 ?? 5.8 Ma Re-Os age of pyrite). The date for white mica from Anarraaq (???195 Ma) appears to be related to a large-scale thermal event in the region immediately before the inception of the Brooks Range orogeny. The white mica from the Red Dog deposit (???126 Ma) correlates with the later stages of the orogeny, a period of blueschist metamorphism, extension, and rapid exhumation, which varied with geographic location. These dates suggest that the Red Dog deposits underwent significant hydrothermal overprinting during multiple episodes of the Brooks Range orogeny. ?? 2004 by Economic Geology.
Domon, Kaoru; Yamada, Takemi; Ōno, Yoshiaki
2016-06-01
We examine the free energy and the thermodynamic properties in the three-chain Hubbard model for Ta2NiSe5 to clarify the phase transitions between the uniform and the FFLO excitonic states which are expected to be observed in Ta2NiSe5 under high pressure.
Novelli, Fabio; Fausti, Daniele; Reul, Julia; Cilento, Federico; van Loosdrecht, Paul H. M.; Nugroho, Agung A.; Palstra, Thomas T. M.; Grueninger, Markus; Parmigiani, Fulvio
2012-01-01
Revealing the nature of charge excitations in strongly correlated electron systems is crucial to understanding their exotic properties. Here we use broadband ultrafast pump-probe spectroscopy in the visible range to study low-energy transitions across the Mott-Hubbard gap in the orbitally ordered in
Energy Technology Data Exchange (ETDEWEB)
Enríquez, Marco; Rosas-Ortiz, Oscar, E-mail: orosas@fis.cinvestav.mx
2013-12-15
We review the properties of the Kronecker (direct, or tensor) product of square matrices A⊗B⊗C⋯ in terms of Hubbard operators. In its simplest form, a Hubbard operator X{sub n}{sup i,j} can be expressed as the n-square matrix which has entry 1 in position (i,j) and zero in all other entries. The algebra and group properties of the observables that define a multipartite quantum system are notably straightforward in such a framework. In particular, we use the Kronecker product in Hubbard notation to get the Clebsch–Gordan decomposition of the product group SU(2)×SU(2). Finally, the n-dimensional irreducible representations so obtained are used to derive closed forms of the Clebsch–Gordan coefficients that rule the addition of angular momenta. Our results can be further developed in many different directions. -- Highlights: •The Kronecker product is studied in terms of Hubbard operators. •Complicated calculations involving large matrices are reduced to simple relations of subscripts. •The algebraic properties of the quantum observables of multipartite systems are studied. •The Clebsch–Gordan coefficients are given in terms of hypergeometric {sub 3}F{sub 2} functions. •The results can be further developed in many different directions.
Cavanagh, Andrew F; Adler, Lynn S; Hazzard, Ruth V
2010-12-01
Winter squash is a vital agricultural commodity worldwide. In the Northeastern United States, the primary insect pest is the striped cucumber beetle, Acalymma vittatum F. Using a Blue Hubbard squash (Cucurbita maxima Duchesne) perimeter trap crop system can reduce insecticide use by >90% in butternut squash (C. moschata Poir), the primary winter squash grown in this region. Despite the savings in insecticide costs, growers may be reluctant to give up field space for a perimeter crop of Blue Hubbard squash, which comprises only 5% of the winter squash market in New England as compared with 19% for buttercup squash. Finding a more marketable trap crop would lower the barrier for adoption of this system. We tested eight varieties of three species of cucurbits for attractiveness to beetles relative to Blue Hubbard and butternut squash, and chose buttercup squash as the most promising replacement. We compared the effect of a buttercup border, Blue Hubbard border, or control (no border) on beetle numbers, herbivory, insecticide use, pollination, and pollen limitation in the main crop. We found that buttercup squash performed equally well as Blue Hubbard as a trap crop, with 97% reduction in total insecticide use compared with control fields. Honey bees (Apis mellifera L.) and squash bees (Peponapis pruinosa Say) were the predominant pollinators, and border treatments did not affect visitation. Hand pollination did not increase reproduction or yield, indicating that natural pollination was sufficient for full yield. This study confirms the effectiveness of perimeter trap crop systems and offers growers a more marketable trap crop for managing cucumber beetle damage.
Exact zero-temperature correlation functions for two-leg Hubbard ladders and carbon nanotubes
Konik, Robert; Ludwig, Andreas W. W.
2001-10-01
Motivated by recent work of Lin, Balents, and Fisher [Phys. Rev. B 58, 1794 (1998)], we compute correlation functions at zero temperature for weakly coupled two-leg Hubbard ladders and (N,N) armchair carbon nanotubes. In this paper it was argued that such systems renormalize towards the SO(8) Gross-Neveu model, an integrable theory. We exploit this integrability to perform the computation at the SO(8) invariant point. Any terms breaking the SO(8) symmetry can be treated systematically in perturbation theory, leading to a model with the same qualitative features as the integrable theory. Using said correlators, we determine the optical conductivity, the single-particle spectral function, and the I-V curve for tunneling into the system from an external metallic lead. The frequency, ω, dependent optical conductivity is determined exactly for ω3m (m being the fermion particle mass in the SO(8) Gross-Neveu model). It is characterized by a sharp ``exciton'' peak at ω=3m, followed by the onset of the particle-hole continuum beginning at ω=2m. Interactions modify this onset to σ(ω+2m)~ω1/2 and not the ω-1/2 one would expect from the van Hove singularity in the density of states. Similarly, we obtain the exact single-particle spectral function for energies less than 3m. The latter possesses a δ function peak arising from single-particle excitations, together with a two-particle continuum for ω>=2m. The final quantity we compute is the tunneling I-V curve to lowest nonvanishing order in the tunneling matrix elements. For this quantity, we present exact results for voltages, V<(1+3)m. The resulting differential conductance is marked by a finite jump at ω=2m, the energy of the onset of tunneling into the continuum of two-particle states. Through integrability, we are able to characterize this jump exactly. All calculations are done through form-factor expansions of correlation functions. These give exact closed form expressions for spectral functions because the SO
A Quantum Mermin-Wagner Theorem for a Generalized Hubbard Model
Directory of Open Access Journals (Sweden)
Mark Kelbert
2013-01-01
Full Text Available This paper is the second in a series of papers considering symmetry properties of bosonic quantum systems over 2D graphs, with continuous spins, in the spirit of the Mermin-Wagner theorem. In the model considered here the phase space of a single spin is ℋ1=L2(M, where M is a d-dimensional unit torus M=ℝd/ℤd with a flat metric. The phase space of k spins is ℋk=L2sym(Mk, the subspace of L2(Mk formed by functions symmetric under the permutations of the arguments. The Fock space H=⊕k=0,1,…ℋk yields the phase space of a system of a varying (but finite number of particles. We associate a space H≃H(i with each vertex i∈Γ of a graph (Γ,ℰ satisfying a special bidimensionality property. (Physically, vertex i represents a heavy “atom” or “ion” that does not move but attracts a number of “light” particles. The kinetic energy part of the Hamiltonian includes (i -Δ/2, the minus a half of the Laplace operator on M, responsible for the motion of a particle while “trapped” by a given atom, and (ii an integral term describing possible “jumps” where a particle may join another atom. The potential part is an operator of multiplication by a function (the potential energy of a classical configuration which is a sum of (a one-body potentials U(1(x, x∈M, describing a field generated by a heavy atom, (b two-body potentials U(2(x,y, x,y∈M, showing the interaction between pairs of particles belonging to the same atom, and (c two-body potentials V(x,y, x,y∈M, scaled along the graph distance d(i,j between vertices i,j∈Γ, which gives the interaction between particles belonging to different atoms. The system under consideration can be considered as a generalized (bosonic Hubbard model. We assume that a connected Lie group G acts on M, represented by a Euclidean space or torus of dimension d'≤d, preserving the metric and the volume in M. Furthermore, we suppose that the potentials U(1, U(2, and V are G-invariant. The result
Sutherland, Ben J.G.; Rico, Ciro; Audet, Céline; Bernatchez, Louis
2017-01-01
Whole-genome duplication (WGD) can have large impacts on genome evolution, and much remains unknown about these impacts. This includes the mechanisms of coping with a duplicated sex determination system and whether this has an impact on increasing the diversity of sex determination mechanisms. Other impacts include sexual conflict, where alleles having different optimums in each sex can result in sequestration of genes into nonrecombining sex chromosomes. Sex chromosome development itself may involve sex-specific recombination rate (i.e., heterochiasmy), which is also poorly understood. The family Salmonidae is a model system for these phenomena, having undergone autotetraploidization and subsequent rediploidization in most of the genome at the base of the lineage. The salmonid master sex determining gene is known, and many species have nonhomologous sex chromosomes, putatively due to transposition of this gene. In this study, we identify the sex chromosome of Brook Charr Salvelinus fontinalis and compare sex chromosome identities across the lineage (eight species and four genera). Although nonhomology is frequent, homologous sex chromosomes and other consistencies are present in distantly related species, indicating probable convergence on specific sex and neo-sex chromosomes. We also characterize strong heterochiasmy with 2.7-fold more crossovers in maternal than paternal haplotypes with paternal crossovers biased to chromosome ends. When considering only rediploidized chromosomes, the overall heterochiasmy trend remains, although with only 1.9-fold more recombination in the female than the male. Y chromosome crossovers are restricted to a single end of the chromosome, and this chromosome contains a large interspecific inversion, although its status between males and females remains unknown. Finally, we identify quantitative trait loci (QTL) for 21 unique growth, reproductive, and stress-related phenotypes to improve knowledge of the genetic architecture of these
Caledonian Deformation in Polydeformed Pre-Mississippian Rocks of the Northeast Brooks Range, Alaska
Johnson, B. G.; Toro, J.; Benowitz, J.
2013-12-01
In the northeastern Brooks Range of Alaska there are polydeformed metasedimentary and metavolcanic rocks exposed below a major pre-Mississippian unconformity. Elsewhere in northern Alaska it has been challenging to correlate the tectonic fabrics of these early Paleozoic to Neoproterozoic rocks to the different orogenic events of the Arctic because of the strong overprint of Mesozoic and Tertiary Brookian deformation. However, our recent field investigations along the Kongakut and Aichiklik rivers of ANWR have identified an older (pre-Brookian) structural event based on the orientation of penetrative cleavage planes and a contrast in folding style to Brookian structures. Many of the cleavage planes are north dipping and orientated parallel to the axial planes of south-vergent folds. Although metamorphic grade is generally low, in localized areas the cleavage planes contain white micas, whose petrologic and isotopic characteristics indicate that they crystallized during fabric formation. 40Ar/39Ar dating of the white micas yield a metamorphic age of ~400 Ma (Early Devonian). This is evidence for a south-directed structural event which is contemporaneous with Caledonian deformation in East Greenland and Svalbard. Stratigraphicaly, the basement consists of a diverse package of highly deformed marine clastic sediments, and a thick section of basaltic to andesitic flows and volcaniclastic rocks, the Whale Mountain volcanics, which have a sharp southern contact but grade northward and upwards into the clastic rocks. All units are metamorphosed to lower greenschist facies. We are currently investigating the age and geochemical characteristics of the Whale Mountain volcanics to determine their tectonic affinity and role in the assemblage of the North Slope block of Northern Alaska.
Directory of Open Access Journals (Sweden)
Luciano Lazzarini Wolff
2007-05-01
Full Text Available The population structure of Phalloceros caudimaculatus was studied in a brook (sites A and B existing in the CEDETEG - Guarapuava/PR. Fourteen length classes of 3 mm amplitude were defined for P. caudimaculatus. The widest length amplitude and the average and maximum sizes were observed in females. Females were significantly more predominant in the whole sample and more frequent in all length classes. The sexual proportion data, showed that the number of females was superior to that of males throughout most of the year. Young occurrence peaks were registered in November and March. Pregnant females were present from March to April, from July to August and in January, characterizing the reproductive season. At sampling site A, a higher occurrence of pregnant females and young was observed.A estrutura populacional de Phalloceros caudimaculatus foi estudada em um riacho (pontos A e B existente no CEDETEG - Guarapuava/PR. Para P. caudimaculatus foram encontradas 14 classes de comprimento com amplitude de 3,0mm. A maior amplitude de comprimento e os maiores tamanhos médios e máximos foram observados nas fêmeas. As fêmeas foram significativamente predominantes na amostra total e mais abundantes em todas as classes de comprimento. Pela proporção sexual pode-se detectar que o número de fêmeas é superior ao de machos a maior parte do ano. Os picos de ocorrência de jovens foram registrados nos meses de novembro e março. As fêmeas grávidas estiveram presentes nos bimestres de março-abril, julho-agosto e no mês de janeiro, caracterizando a época reprodutiva. No ponto de coleta A foi observado uma maior ocorrência de fêmeas grávidas e de jovens.
Darrow, Margaret M.; Gyswyt, Nora L.; Simpson, Jocelyn M.; Daanen, Ronald P.; Hubbard, Trent D.
2016-05-01
Frozen debris lobes (FDLs) are elongated, lobate permafrost features that mostly move through shear in zones near their bases. We present a comprehensive overview of eight FDLs within the Dalton Highway corridor (southern Brooks Range, Alaska), including their catchment geology and rock strengths, lobe soil characteristics, surface movement measurements collected between 2012 and 2015, and analysis of historic and modern imagery from 1955 to 2014. Field mapping and rock strength data indicate that the metasedimentary and metavolcanic bedrock forming the majority of the lobe catchments has very low to medium strength and is heavily fractured, thus easily contributing to FDL formation. The eight investigated FDLs consist of platy rocks typical of their catchments, organic debris, and an ice-poor soil matrix; massive ice, however, is present within FDLs as infiltration ice, concentrated within cracks open to the surface. Exposure of infiltration ice in retrogressive thaw slumps (RTSs) and associated debris flows leads to increased movement and various stages of destabilization, resulting in morphological differences among the lobes. Analysis of historic imagery indicates that movement of the eight investigated FDLs has been asynchronous over the study period, and since 1955, there has been an overall increase in movement rates of the investigated FDLs. The formation of surface features, such as cracks, scarps, and RTSs, suggests that the increased movement rates correlate to general instability, and even at their current distances, FDLs are impacting infrastructure through increased sediment mobilization. FDL-A is the largest of the investigated FDLs. As of August 2015, FDL-A was 39.2 m from the toe of the Dalton Highway embankment. Based on its current distance and rate of movement, we predict that FDL-A will reach the Dalton Highway alignment by 2023.
Jang, Seung I; Lillehoj, Hyun S; Lee, Sung-Hyen; Lee, Kyung Woo; Lillehoj, Erik P; Hong, Yeong Ho; An, Dong-Jun; Jeoung, D Hye-Young; Chun, Ji-Eun
2013-09-01
Necrotic enteritis is an enteric disease of poultry resulting from infection by Clostridium perfringens with coinfection by Eimeria spp. constituting a major risk factor for disease pathogenesis. This study compared three commercial broiler chicken lines using an experimental model of necrotic enteritis. Day-old male Cobb, Ross, and Hubbard broilers were orally infected with viable C. perfringens and E. maxima and fed a high-protein diet to promote the development of experimental disease. Body weight loss, intestinal lesions, and serum antibody levels against alpha-toxin and necrotic enteritis B-like (NetB) toxin were measured as parameters of disease susceptibility and host immune response. Cobb chickens exhibited increased body weight loss compared with Ross and Hubbard breeds and greater gut lesion severity compared with Ross chickens. NetB antibody levels were greater in Cobb chickens compared with the Ross or Hubbard groups. These results suggest that Cobb chickens may be more susceptible to necrotic enteritis in the field compared with the Ross and Hubbard lines.
DEFF Research Database (Denmark)
Patrick, Christopher; Thygesen, Kristian Sommer
2016-01-01
In non-self-consistent calculations of the total energy within the random-phase approximation (RPA) for electronic correlation, it is necessary to choose a single-particle Hamiltonian whose solutions are used to construct the electronic density and noninteracting response function. Here we invest...... and qualitatively different from that found from calculations employingU-corrected (semi)local functionals.However we also find that the+U term cannot be used to correct the RPA’s poor description of the heat of formation of NiO....... investigate the effect of including a Hubbard-U term in this single-particle Hamiltonian, to better describe the on-site correlation of 3d electrons in the transitionmetal compounds ZnS, TiO2, and NiO.We find that the RPA lattice constants are essentially independent of U, despite large changes...
Energy Technology Data Exchange (ETDEWEB)
Feng, Y.; Jaramillo, R.; Banerjee, A.; Honig, J. M.; Rosenbaum, T. F. (X-Ray Science Division); (Univ. of Chicago); (Harvard Univ.); (Purdue Univ.)
2011-01-01
We use synchrotron x-ray diffraction and electrical transport under pressure to probe both the magnetism and the structure of single-crystal NiS{sub 2} across its Mott-Hubbard transition. In the insulator, the low-temperature antiferromagnetic order results from superexchange among correlated electrons and couples to a (1/2, 1/2, 1/2) superlattice distortion. Applying pressure suppresses the insulating state, but enhances the magnetism as the superexchange increases with decreasing lattice constant. By comparing our results under pressure to previous studies of doped crystals, we show that this dependence of the magnetism on the lattice constant is consistent for both band broadening and band filling. In the high-pressure metallic phase the lattice symmetry is reduced from cubic to monoclinic, pointing to the primary influence of charge correlations at the transition. There exists a wide regime of phase separation that may be a general characteristic of correlated quantum matter.
Patel, Niravkumar D.; Mukherjee, Anamitra; Kaushal, Nitin; Moreo, Adriana; Dagotto, Elbio
2017-08-01
We employ a recently developed computational many-body technique to study for the first time the half-filled Anderson-Hubbard model at finite temperature and arbitrary correlation U and disorder V strengths. Interestingly, the narrow zero temperature metallic range induced by disorder from the Mott insulator expands with increasing temperature in a manner resembling a quantum critical point. Our study of the resistivity temperature scaling Tα for this metal reveals non-Fermi liquid characteristics. Moreover, a continuous dependence of α on U and V from linear to nearly quadratic is observed. We argue that these exotic results arise from a systematic change with U and V of the "effective" disorder, a combination of quenched disorder and intrinsic localized spins.
Hewson, Alex C; Bauer, Johannes
2010-03-24
We show that information on the probability density of local fluctuations can be obtained from a numerical renormalization group calculation of a reduced density matrix. We apply this approach to the Anderson-Holstein impurity model to calculate the ground state probability density ρ(x) for the displacement x of the local oscillator. From this density we can deduce an effective local potential for the oscillator and compare its form with that obtained from a semiclassical approximation as a function of the coupling strength. The method is extended to the infinite dimensional Holstein-Hubbard model using dynamical mean field theory. We use this approach to compare the probability densities for the displacement of the local oscillator in the normal, antiferromagnetic and charge ordered phases.
LeBlanc, J. P. F.; Antipov, Andrey E.; Becca, Federico; Bulik, Ireneusz W.; Chan, Garnet Kin-Lic; Chung, Chia-Min; Deng, Youjin; Ferrero, Michel; Henderson, Thomas M.; Jiménez-Hoyos, Carlos A.; Kozik, E.; Liu, Xuan-Wen; Millis, Andrew J.; Prokof'ev, N. V.; Qin, Mingpu; Scuseria, Gustavo E.; Shi, Hao; Svistunov, B. V.; Tocchio, Luca F.; Tupitsyn, I. S.; White, Steven R.; Zhang, Shiwei; Zheng, Bo-Xiao; Zhu, Zhenyue; Gull, Emanuel; Simons Collaboration on the Many-Electron Problem
2015-10-01
Numerical results for ground-state and excited-state properties (energies, double occupancies, and Matsubara-axis self-energies) of the single-orbital Hubbard model on a two-dimensional square lattice are presented, in order to provide an assessment of our ability to compute accurate results in the thermodynamic limit. Many methods are employed, including auxiliary-field quantum Monte Carlo, bare and bold-line diagrammatic Monte Carlo, method of dual fermions, density matrix embedding theory, density matrix renormalization group, dynamical cluster approximation, diffusion Monte Carlo within a fixed-node approximation, unrestricted coupled cluster theory, and multireference projected Hartree-Fock methods. Comparison of results obtained by different methods allows for the identification of uncertainties and systematic errors. The importance of extrapolation to converged thermodynamic-limit values is emphasized. Cases where agreement between different methods is obtained establish benchmark results that may be useful in the validation of new approaches and the improvement of existing methods.
Leblanc, James
In this talk we present numerical results for ground state and excited state properties (energies, double occupancies, and Matsubara-axis self energies) of the single-orbital Hubbard model on a two-dimensional square lattice. In order to provide an assessment of our ability to compute accurate results in the thermodynamic limit we employ numerous methods including auxiliary field quantum Monte Carlo, bare and bold-line diagrammatic Monte Carlo, method of dual fermions, density matrix embedding theory, density matrix renormalization group, dynamical cluster approximation, diffusion Monte Carlo within a fixed node approximation, unrestricted coupled cluster theory, and multireference projected Hartree-Fock. We illustrate cases where agreement between different methods is obtained in order to establish benchmark results that should be useful in the validation of future results.
Energy Technology Data Exchange (ETDEWEB)
Wallace, W.K.; Hanks, C.L.
1988-02-01
The structural style of the range-front region of the northeastern Brooks Range in Arctic National Wildlife Refuge (ANWR) is strongly controlled by (1) the existence of detachment horizons in both pre-Mississippian rocks and the unconformably overlying Mississippian to Lower Cretaceous cover sequence, and (2) lithology and structural competency of the pre-Mississippian rocks. These variables strongly influence lateral changes in structural style. The Brooks Range of northwestern ANWR is dominated by a series of narrow linear anticlinoria, whereas in northeastern ANWR the Brooks Range is characterized by only two broad and strongly arcuate anticlinoria. In both areas, the anticlinoria are controlled by the geometry of a duplex bounded by a floor thrust in pre-Mississippian rocks and a roof thrust in the Kayak Shale, near the base of the cover sequence. In the west, where the pre-Mississippian partially consists of structurally competent carbonates, each anticlinorium marks a single horse in the duplex. However, in the east, pre-Mississippian rocks are relatively incompetent and each anticlinorium is cored by multiple horses. In the west, shortening above the roof thrust is by detachment folding, except where the shale detachment horizon is depositionally absent. In contrast, in eastern ANWR shortening above the roof thrust is by major thrust duplication of the entire cover sequence, perhaps due to lithology and thickness changes within the detachment horizon. A Devonian batholith marks the boundary between the eastern and western structural provinces. The thrust-controlled range front of eastern ANWR extends north of the batholith, suggesting that the batholith itself may be underlain by a thrust fault.
Thomas, Scott R.; Lee, Jinho; Stephens, John W.; Hostler, Robert W., Jr.; VonKamp, William D.
2010-01-01
The Hypersonic Tunnel Facility (HTF) located at the NASA Glenn Research Center s Plum Brook Station in Sandusky, Ohio, is the nation s only large-scale, non-vitiated, hypersonic propulsion test facility. The HTF, with its 4-story graphite induction heater, is capable of duplicating Mach 5, 6, and 7 flight conditions. This unique propulsion system test facility has experienced several standby and reactivation cycles. The intent of the paper is to overview the HTF capabilities to the propulsion community, present the current status of HTF, and share the lessons learned from putting a large-scale facility into mothball status for a later restart
1986-09-01
as a referral center as the basis for developing a marketing strategy . D MTRIPUO =1 ~ ’ 0 N Approved Z.r =uzic :eI’,.~e: I, Dj rzut.:n Un. ::ed 20...have become the principal constituency group that holds the key to meeting this goal. In this regard, a marketing strategy must be developed...Brooke Army Medical Center’s Health Service Region towards BAMC as a referral center as the basis 9 for developing a marketing strategy . Objectives The
Burns, R.L.; Medalie, Laura
1998-01-01
This report provides the results of a detailed Level II analysis of scour potential at structure TOWNTH00290037 on Town Highway 29 crossing Mill Brook, Townshend, Vermont (figures 1–8). A Level II study is a basic engineering analysis of the site, including a quantitative analysis of stream stability and scour (FHWA, 1993). Results of a Level I scour investigation also are included in Appendix E of this report. A Level I investigation provides a qualitative geomorphic characterization of the study site. Information on the bridge, gleaned from Vermont Agency of Transportation (VTAOT) files, was compiled prior to conducting Level I and Level II analyses and is found in appendix D.
Burns, Ronda L.; Degnan, James R.
1998-01-01
This report provides the results of a detailed Level II analysis of scour potential at structure WODFTH00010002 on Town Highway 1 crossing Hell Hollow Brook, Woodford, Vermont (figures 1-8). A Level II study is a basic engineering analysis of the site, including a quantitative analysis of stream stability and scour (FHWA, 1993). Results of a Level I scour investigation also are included in appendix E of this report. A Level I investigation provides a qualitative geomorphic characterization of the study site. Information on the bridge, gleaned from Vermont Agency of Transportation (VTAOT) files, was compiled prior to conducting Level I and Level II analyses and is found in appendix D.
Directory of Open Access Journals (Sweden)
Pankaj S. Bhatnagar
2013-12-01
Full Text Available The present study aims at extracting the fossil database www.paleodb.org to compare extinct megafauna genera, Mammuthus Brookes, 1828 and Mammut Blumenbach, 1799 along with its close reletive, Zygolophodon (Vacek, 1877. Taxon count indicated 9 species for the former genus, and a dozen species for the latter two genera taken together. Mammuthus scored higher than Mammut and Zygolophodon in occurrences. They were found in North America, Europe, Asia and Africa but additionally, Mammuthus was found in South America as well. As two families diverged about 27 m years ago, these differences are important.
Bergeron, Normand E.; Constantin, Pierre-Marc; Goerig, Elsa; Castro-Santos, Theodore R.
2016-01-01
We used video recording and near-infrared illumination to document the spatial behavior of brook trout of various sizes attempting to pass corrugated culverts under different hydraulic conditions. Semi-automated image analysis was used to digitize fish position at high temporal resolution inside the culvert, which allowed calculation of various spatial behavior metrics, including instantaneous ground and swimming speed, path complexity, distance from side walls, velocity preference ratio (mean velocity at fish lateral position/mean crosssectional velocity) as well as number and duration of stops in forward progression. The presentation summarizes the main results and discusses how they could be used to improve fish passage performance in culverts.
Smith, D.M.; Welsh, S.A.; Turk, P.J.
2011-01-01
In this laboratory study, we quantified substrate selection by small (large (100-150 mm) ammocoetes of the least brook lamprey (Lampetra aepyptera). In aquaria, ammocoetes were given a choice to burrow into six equally-available substrate types: small gravel (2.360-4.750 mm), coarse sand (0.500-1.400 mm), fine sand (0.125-0.500 mm), organic substrate (approximately 70% decomposing leaves/stems and organic sediment particles, and 30% silt and fine sand), an even mixture of silt, clay, and fine sand, and silt/clay (population sizes. ?? 2011 Springer Science+Business Media B.V.
Fitzpatrick, Faith A.; Peppler, Marie C.; Saad, David A.; Pratt, Dennis M.; Lenz, Bernard N.
2015-01-01
In 2002–03, the U.S. Geological Survey conducted a study of the geomorphic, flood, and groundwater-flow characteristics of five Bayfield Peninsula streams, Wisconsin (Cranberry River, Bark River, Raspberry River, Sioux River, and Whittlesey Creek) to determine the physical limitations for brook-trout habitat. The goals of the study were threefold: (1) to describe geomorphic characteristics and processes, (2) to determine how land-cover characteristics affect flood peaks, and (3) to determine how regional groundwater flow patterns affect base flow.
Nature of hydrothermal fluids at the shale-hosted Red Dog Zn-Pb-Ag deposits, Brooks Range, Alaska
Leach, David L.; Marsh, Erin E.; Emsbo, Poul; Rombach, Cameron; Kelley, Karen D.; Anthony, Michael W.
2004-01-01
The Red Dog Zn-Pb-Ag district in the western Brooks Range, northern Alaska, contains numerous shale-hosted Zn-Pb sulfide and barite deposits in organic-rich siliceous mudstone and shale, chert, and carbonate rocks of the Carboniferous Kuna Formation. The giant Red Dog shale-hosted deposits consist of a cluster of four orebodies (Main, Qanaiyaq, Aqqaluk, and Paalaaq) that lie within distinct thrust panels that offset a single ore deposit during the Mesozoic Brookian orogeny. These Zn-Pb-Ag-barite orebodies contain one of the world's largest reserves and resources of zinc.
Energy Technology Data Exchange (ETDEWEB)
Erika N. Bailey
2011-10-10
In 1941, the War Department acquired approximately 9,000 acres of land near Sandusky, Ohio and constructed a munitions plant. The Plum Brook Ordnance Works Plant produced munitions, such as TNT, until the end of World War II. Following the war, the land remained idle until the National Advisory Committee for Aeronautics later called the National Aeronautics and Space Administration (NASA) obtained 500 acres to construct a nuclear research reactor designed to study the effects of radiation on materials used in space flight. The research reactor was put into operation in 1961 and was the first of fifteen test facilities eventually built by NASA at the Plum Brook Station. By 1963, NASA had acquired the remaining land at Plum Brook for these additional test facilities
MacGillivray, Neil
2015-09-18
This article reviews the life and work of Sir William O'Shaughnessy Brooke (formerly Sir William Brooke O'Shaughnessy), an Edinburgh doctor of medicine and Fellow of the Royal Society who as a young doctor in London analysed the blood and excreta of cholera victims, an action which led to the first successful use of intravenous replacement therapy. His career in India was distinguished in several spheres: chemistry, pharmacology in which he introduced cannabis indica to Europe, and in the field of electric telegraphy where he became the superintendent of telegraphs for India.
1981-09-01
E. EDGAR , III As stated Colonel, Corps of Engineers Division Engineer S-. 10 5 I FARM BROOK SITE 2B DAM CT 01547 I iCONNECTICUT COASTAL BASIN HAMDEN...construction is complete. Prepared by: Edgar P. Steele T. R. Wire Subj: Connecticut WP-08, Farm Brook, Site 2B Reviewed and Approved by: lorn P...30 D. REa-NFORC.EQ ~ZNCETE IPE OP BERM ELEV. 64.0 50LE0, 00 - ORINAL (5ROUND LINE 0ow~~l;Dow REAM ANE 3-0-005 FT/FT.- CONCRETE CRADLE -~GROUT R
Population response to habitat fragmentation in a stream-dwelling brook trout population
Letcher, B.H.; Nislow, K.H.; Coombs, J.A.; O'Donnell, M. J.; Dubreuil, T.L.
2007-01-01
Fragmentation can strongly influence population persistence and expression of life-history strategies in spatially-structured populations. In this study, we directly estimated size-specific dispersal, growth, and survival of stream-dwelling brook trout in a stream network with connected and naturally-isolated tributaries. We used multiple-generation, individual-based data to develop and parameterize a size-class and location-based population projection model, allowing us to test effects of fragmentation on population dynamics at local (i.e., subpopulation) and system-wide (i.e., metapopulation) scales, and to identify demographic rates which influence the persistence of isolated and fragmented populations. In the naturally-isolated tributary, persistence was associated with higher early juvenile survival (-45% greater), shorter generation time (one-half) and strong selection against large body size compared to the open system, resulting in a stage-distribution skewed towards younger, smaller fish. Simulating barriers to upstream migration into two currently-connected tribuory populations caused rapid (2-6 generations) local extinction. These local extinctions in turn increased the likelihood of system-wide extinction, as tributaries could no longer function as population sources. Extinction could be prevented in the open system if sufficient immigrants from downstream areas were available, but the influx of individuals necessary to counteract fragmentation effects was high (7-46% of the total population annually). In the absence of sufficient immigration, a demographic change (higher early survival characteristic of the isolated tributary) was also sufficient to rescue the population from fragmentation, suggesting that the observed differences in size distributions between the naturally-isolated and open system may reflect an evolutionary response to isolation. Combined with strong genetic divergence between the isolated tributary and open system, these results
Winearls, Joan
2008-01-01
British by birth Allan Cyril Brooks (1869-1946) emigrated to Canada in the 1880s, and became one of the most important North American bird illustrators during the first half of the twentieth century. Brooks was one of the leading ornithologists and wildlife collectors of the time; he corresponded extensively with other ornithologists and supplied specimens to many major North American museums. From the 1890s on he hoped to support himself by painting birds and mammals, but this was not possible in Canada at that time and he was forced to turn to American sources for illustration commissions. His work can be compared with that of his contemporary, the leading American bird painter Louis Agassiz Fuertes (1874-1927), and there are striking similarities and differences in their careers. This paper discusses the work of a talented, self-taught wildlife artist working in a North American milieu, his difficulties and successes in a newly developing field, and his quest for Canadian recognition.
Castro-Santos, Theodore; Sanz-Ronda, Francisco Javier; Ruiz-Legazpi, Jorge
2013-01-01
Sprinting behavior of free-ranging fish has long been thought to exceed that of captive fish. Here we present data from wild-caught brook trout (Salvelinus fontinalis) and brown trout (Salmo trutta), volitionally entering and sprinting against high-velocity flows in an open-channel flume. Performance of the two species was nearly identical, with the species attaining absolute speeds > 25 body lengths·s−1. These speeds far exceed previously published observations for any salmonid species and contribute to the mounting evidence that commonly accepted estimates of swimming performance are low. Brook trout demonstrated two distinct modes in the relationship between swim speed and fatigue time, similar to the shift from prolonged to sprint mode described by other authors, but in this case occurring at speeds > 19 body lengths·s−1. This is the first demonstration of multiple modes of sprint swimming at such high swim speeds. Neither species optimized for distance maximization, however, indicating that physiological limits alone are poor predictors of swimming performance. By combining distributions of volitional swim speeds with endurance, we were able to account for >80% of the variation in distance traversed by both species.
Directory of Open Access Journals (Sweden)
Pablo J. López-González
2010-08-01
Full Text Available Examination of recent benthic material collected during several cruises in the Gulf of Cadiz (NE Atlantic and the Strait of Sicily (Mediterranean has allowed the taxonomic reassessment of some previously identified specimens belonging to the monogeneric gorgonian family Dendrobrachiidae Brook, 1889. Dendrobrachia fallax Brook, 1889 is the type species of the single genus in this family, and was originally described from Ascension Island (South Atlantic. Subsequently, other authors reported the presence of this species in Cape Verde Islands (north-eastern Atlantic and some Mediterranean localities (Alboran Sea and the Strait of Sicily. The study of the specimen from the Prince of Monaco collections in Cape Verde Islands, and recently collected material from the Gulf of Cadiz (north-eastern Atlantic and in the south of Malta (Mediterranean, materials previously considered as D. fallax, allow us to recognize two undescribed species in this genus. All previous records of D. fallax from the north-eastern Atlantic and Mediterranean should be considered incorrect. Opresko and Bayer (1991 added two additional species of Dendrobrachia. Two new species are described here and compared with their congeners.
Ayotte, Joseph D.; Medalie, Laura
1996-01-01
This report provides the results of a detailed Level II analysis of scour potential at structure BLOOTH00020001 on town highway 2 crossing Mill Brook, Bloomfield, Vermont (figures 1–8). A Level II study is a basic engineering analysis of the site, including a quantitative analysis of stream stability and scour (U.S. Department of Transportation, 1993). Results of a Level I scour investigation also are included in Appendix E of this report. A Level I investigation provides a qualitative geomorphic characterization of the study site. Information on the bridge, gleaned from Vermont Agency of Transportation (VTAOT) files, was compiled prior to conducting Level I and Level II analyses and is found in Appendix D. The site is in the White Mountain section of the New England Upland physiographic province of north-east Vermont in the town of Bloomfield. The 4.85-mi2 drainage area is in a predominantly rural and forested basin. In the vicinity of the study site, the banks have dense woody vegetation coverage. In the study area, Mill Brook has an incised, sinuous channel with a slope of approximately 0.03 ft/ft, an average channel top width of 28 ft and an average channel depth of 4 ft. The predominant channel bed materials are gravel and cobbles (D50 is 57.3 mm or 0.188 ft). The geomorphic assessment at the time of the Level I and Level II site visit on July 6, 1995,
Johnson, James H.; Chalupnicki, Marc; Abbett, Ross; Diaz, Avriel R; Nack, Christopher C
2017-01-01
Fish feeding ecology has been shown to vary over a 24-h period in terms of the prey consumed and feeding intensity. Consequently, in order to best determine the interspecific feeding associations within a fish community, examination of the diet at multiple times over a 24-h period is often necessary. We examined the diel feeding ecology of three fish species that were numerically dominant in a Lake Ontario embayment during summer. The diet of each of the three species, subyearling pumpkinseed Lepomis gibbosus, golden shiner Notemigonus crysoleucus, and brook silverside Labidesthes sicculus, was distinct with no significant overlap in diet composition occurring within any of the 4-h time intervals. The diet composition of each species suggested that brook silverside were feeding at the surface (terrestrial invertebrates and aquatic surface dwelling hemipterans) whereas subyearling pumpkinseed (amphipods) and golden shiner (tipulids) were feeding on different benthic prey. Differences in feeding periodicity were most pronounced for subyearling pumpkinseed. Our findings provide valuable insights on interspecific feeding associations among these three fish species during summer in a Lake Ontario embayment.
Trabant, Dennis C.; March, Rod S.; Thomas, Donald S.
2003-01-01
Hubbard Glacier, the largest calving glacier on the North American Continent (25 percent larger than Rhode Island), advanced across the entrance to 35-mile-long Russell Fiord during June 2002, temporarily turning it into a lake. Hubbard Glacier has been advancing for more than 100 years and has twice closed the entrance to Russell Fiord during the last 16 years by squeezing and pushing submarine glacial sediments across the mouth of the fiord. Water flowing into the cutoff fiord from mountain streams and glacier melt causes the level of Russell Lake to rise. However, both the 1986 and 2002 dams failed before the lake altitude rose enough for water to spill over a low pass at the far end of the fiord and enter the Situk River drainage, a world-class sport and commercial fishery near Yakutat, Alaska.
Gomes, Clélio Brasil Cardoso
2013-01-01
Estudamos a transi¸c ao de fase superfluido-isolante de Mott (SF-MI) em redes ´opticas via modelo Jaynes-Cummings-Hubbard utilizando a aproxima¸c ao de f´ermions. Inicialmente fazemos uma revis ao do modelo Jaynes-Cummings que descreve a intera¸c ao de um ´atomo de dois n´ıveis com um campo eletromagn´etico quantizado. Em seguida estudamos as propriedades da transi¸c ao de fase SF-MI no modelo Bose-Hubbard e discutimos as caracter´ısticas das duas fase qu anticas e as condi¸c ...
Zitzler, R.; Pruschke, Th.; Bulla, R.
2004-05-01
We discuss the magnetic phase diagram for the Hubbard model with magnetic frustration obtained within the dynamical mean-field theory. Most interesting is the appearance of a first-order paramagnetic metal to antiferromagnetic insulator transition for the magnetically frustrated lattice at half filling. For finite doping the antiferromagnetic phase is susceptible to phase separation and competes with an itinerant ferromagnetic phase (Nagaoka ferromagnetism), leading to an unexpectedly rich magnetic phase diagram.
Energy Technology Data Exchange (ETDEWEB)
Zitzler, R.; Pruschke, Th. E-mail: pruschke@theorie.physik.uni-goettingen.de; Bulla, R
2004-05-01
We discuss the magnetic phase diagram for the Hubbard model with magnetic frustration obtained within the dynamical mean-field theory. Most interesting is the appearance of a first-order paramagnetic metal to antiferromagnetic insulator transition for the magnetically frustrated lattice at half filling. For finite doping the antiferromagnetic phase is susceptible to phase separation and competes with an itinerant ferromagnetic phase (Nagaoka ferromagnetism), leading to an unexpectedly rich magnetic phase diagram.
Saha, Madhumita; Maiti, Santanu K.
2016-01-01
The interplay between Hubbard interaction, long-range hopping and disorder on persistent current in a mesoscopic one-dimensional conducting ring threaded by a magnetic flux $\\phi$ is analyzed in detail. Two different methods, exact numerical diagonalization and Hartree-Fock mean field theory, are used to obtain numerical results from the many-body Hamiltonian. The current in a disordered ring gets enhanced as a result of electronic correlation and it becomes more significant when contribution...
Yoshioka, Hideo
2002-08-01
Magnetic properties in a charge-ordered state are examined for the extended Hubbard model at half-filling. Magnetic excitations, magnetic susceptibilities and a nuclear spin relaxation rate are calculated with taking account of fluctuations around the mean-field solution. The relevance of the present results to the observation in the 1:1 organic conductors, (TTM-TTP)I3, is discussed.
Energy Technology Data Exchange (ETDEWEB)
Brehm, Sascha
2009-02-26
Two-particle excitations, such as spin and charge excitations, play a key role in high-T{sub c} cuprate superconductors (HTSC). Due to the antiferromagnetism of the parent compound the magnetic excitations are supposed to be directly related to the mechanism of superconductivity. In particular, the so-called resonance mode is a promising candidate for the pairing glue, a bosonic excitation mediating the electronic pairing. In addition, its interactions with itinerant electrons may be responsible for some of the observed properties of HTSC. Hence, getting to the bottom of the resonance mode is crucial for a deeper understanding of the cuprate materials. To analyze the corresponding two-particle correlation functions we develop in the present thesis a new, non-perturbative and parameter-free technique for T=0 which is based on the Variational Cluster Approach (VCA, an embedded cluster method for one-particle Green's functions). Guided by the spirit of the VCA we extract an effective electron-hole vertex from an isolated cluster and use a fully renormalized bubble susceptibility {chi}{sub 0} including the VCA one-particle propagators. Within our new approach, the magnetic excitations of HTSC are shown to be reproduced for the Hubbard model within the relevant strong-coupling regime. Exceptionally, the famous resonance mode occurring in the underdoped regime within the superconductivity-induced gap of spin-flip electron-hole excitations is obtained. Its intensity and hourglass dispersion are in good overall agreement with experiments. Furthermore, characteristic features such as the position in energy of the resonance mode and the difference of the imaginary part of the susceptibility in the superconducting and the normal states are in accord with Inelastic Neutron Scattering (INS) experiments. For the first time, a strongly-correlated parameter-free calculation revealed these salient magnetic properties supporting the S=1 magnetic exciton scenario for the
Barringer, Thomas
1996-01-01
Flood magnitude and frequency of Monongahela Brook in Deptford Township, Gloucester County, New Jersey, were determined by using the rational method. Flood-magnitude and -frequency estimates, as well as drainage-basin characteristics, are included in this report. The 100-year-flood estimate is 80 cubic feet per second.
New York State Office of the Comptroller, Albany. Div. of Management Audit.
This audit report assesses the propriety and economy of space leasing practices of the State University of New York at Stony Brook (SUNY-SB) for the period July 1, 1994 through December 31, 1996, specifically those related to a health center that includes five professional schools, a 536-bed teaching hospital, and a 350-bed veterans' home. Some of…