Entanglement area law from specific heat capacity

We study the scaling of entanglement in low-energy states of quantum many-body models on lattices of arbitrary dimensions. We allow for unbounded Hamiltonians such that systems with bosonic degrees of freedom are included. We show that if at low enough temperatures the specific heat capacity of the model decays exponentially with inverse temperature, the entanglement in every low-energy state satisfies an area law (with a logarithmic correction). This behaviour of the heat capacity is typically observed in gapped systems. Assuming merely that the low-temperature specific heat decays polynomially with temperature, we find a subvolume scaling of entanglement. Our results give experimentally verifiable conditions for area laws, show that they are a generic property of low-energy states of matter, and, to the best of our knowledge, constitute the first proof of an area law for unbounded Hamiltonians beyond those that are integrable.Comment: v3 now featuring bosonic system

Equivalence of Statistical Mechanical Ensembles for Non-Critical Quantum Systems

We consider the problem of whether the canonical and microcanonical ensembles are locally equivalent for short-ranged quantum Hamiltonians of $N$ spins arranged on a $d$-dimensional lattices. For any temperature for which the system has a finite correlation length, we prove that the canonical and microcanonical state are approximately equal on regions containing up to $O(N^{1/(d+1)})$ spins. The proof rests on a variant of the Berry--Esseen theorem for quantum lattice systems and ideas from quantum information theory

Thermalization and Return to Equilibrium on Finite Quantum Lattice Systems

Thermal states are the bedrock of statistical physics. Nevertheless, when and how they actually arise in closed quantum systems is not fully understood. We consider this question for systems with local Hamiltonians on finite quantum lattices. In a first step, we show that states with exponentially decaying correlations equilibrate after a quantum quench. Then we show that the equilibrium state is locally equivalent to a thermal state, provided that the free energy of the equilibrium state is sufficiently small and the thermal state has exponentially decaying correlations. As an application, we look at a related important question: When are thermal states stable against noise? In other words, if we locally disturb a closed quantum system in a thermal state, will it return to thermal equilibrium? We rigorously show that this occurs when the correlations in the thermal state are exponentially decaying. All our results come with finite-size bounds, which are crucial for the growing field of quantum thermodynamics and other physical applications.Comment: 8 pages (5 for main text and 3 for appendices); v2 is essentially the published versio

Charge Transfer Fluctuations as a QGP Signal

In this study, we analyze the recently proposed charge transfer fluctuations within a finite pseudo-rapidity space. As the charge transfer fluctuation is a measure of the local charge correlation length, it is capable of detecting inhomogeneity in the hot and dense matter created by heavy ion collisions. We predict that going from peripheral to central collisions, the charge transfer fluctuations at midrapidity should decrease substantially while the charge transfer fluctuations at the edges of the observation window should decrease by a small amount. These are consequences of having a strongly inhomogeneous matter where the QGP component is concentrated around midrapidity. We also show how to constrain the values of the charge correlations lengths in both the hadronic phase and the QGP phase using the charge transfer fluctuations. Current manuscript is based on the preprints hep-ph/0503085 (to appear in Physical Review C) and nucl-th/0506025.Comment: To appear in the proceedings of 18th International Conference on Ultrarelativistic Nucleus-Nucleus Collisions: Quark Matter 2005 (QM 2005), Budapest, Hungary, 4-9 Aug 200

The 1941 Iowa corn yield test

The Iowa Corn Yield Test attempts to supply performance records to the buyer and producer of various hybrids offered for sale to the Iowa farmer. Iowa has become “hybrid corn conscious” since 1935 when 3.1 percent of the Iowa corn acreage was planted to hybrid seed. In 1941, 95 percent of the corn acreage was estimated to have been planted to hybrid seed. Each year the Iowa farmer is confronted with the problem of knowing which hybrid to buy. The Iowa Corn Yield Test may help in solving this problem by giving some indication of the performance of various hybrids in different parts of the state. Records are determined for acre yield, percent stand, lodging, moisture, dropped ears and damaged kernels. Significant differences in yield and in other characteristics between hybrids, providing they are equal in stand, grown under the same environmental conditions may be attributed to genetic differences

The 1940 Iowa corn yield test

The Iowa Com Yield Test makes available to purchasers and producers alike the performance records of different kinds of corn. Many of these kinds are offered for sale to Iowa farmers. If these performance records are properly studied they should help the purchaser to select the com best adapted for his purposes. The testing fields of the Iowa Com Yield Test were located in 12 systematically scattered areas of the state. The data should, therefore, be helpful to the seed producer by indicating the range of adaptation of the different strains and hybrid combinations and the performance under different soil and climatic conditions. Nine out of 10 corn acres in Iowa are planted to hybrid corn. It is, therefore, important to determine the adaptation and performance of various combinations in different parts of the state. The data presented in this bulletin include acre yield, lodging, maturity, dropped ears and damaged kernels. Significant differences in yield between different kinds of corn with equal stands, grown in adequately replicated tests, may be attributed to genetic differences under the environmental conditions of the test

1938 Iowa corn yield test

A total of 1,110 district entries was made in the 12 fields of the 1938 Iowa Corn Yield Test. These were divided into three groups on the basis of the indicated seed grown by the entrant in 1937; Regular Open-Pollinated, Regular Hybrids, and Experimental Hybrids

1939 Iowa corn yield test

1. The purpose of the 1939 Iowa Corn Yield Test was to determine for each district and section of the state those kinds of corn which perform best. 2. The state was divided into four sections for the tests. Each section was composed of three districts in each of which was located a testing field. 3. A total of 1,214 district entries was made in the 12 fields. These entries were divided into two classes, regular and experimental, depending upon the quantity of seed indicated to have been grown by the entrant in 1938. 4. The seed for planting the entries in the regular class was obtained by the Iowa Corn and Small Grain Growers’ Association from warehouses, on the open market and from farmers who had purchased the seed to plant. The seed for planting the experimental entries was supplied by the entrant. 5. Each regular entry was planted in 10 plots and each experimental entry in five plots in each field where tested. 6. Data were obtained for each entry on percentage stand, ear height, acre yield, percentage lodging, moisture content, percentage of dropped ears and damaged kernels. 7. A performance score was computed for each entry. In computing this score the yield was weighted 50 percent, dry corn 20 percent, and lodging resistance, ears on stalks and undamaged kernels 10 percent each. The entries are arranged in tables 7 to 22, inclusive, according to their performance score. 8. The difference in yield necesary to be considered significant was calculated and is included in the performance data for each district and each section. Because of the increased number of replications in the regular classes the bushels necessary for significance are generally smaller than in the experimental classes. 9. The average yield, moisture percentage and percentage of lodged plants for those section entries which were in the 1939 test and in tests of the same previous years were calculated. These data offer a more reliable basis for predicting the future performance of these entries than the results of any one year. 10. The long ripening season of 1939 permitted late, unadapted kinds of corn to mature in the Northern Section where they normally would be too late. Many of the hybrids which performed well in the Northern and North Central sections might be wholly unsatisfactory in a season with a less favorable fall. 11. The average yield of all hybrids was greater than that of the open-pollinated varieties in each of the 12 districts. The average advantage of the hybrids for the entire state was 14.0 percent. All of the hybrids in the test, however, were not superior. In 6 of the 12 districts the lowest yield was made by an open-pollinated variety, in 2 by an experimental hybrid and in 4 by a regular hybrid. 12. Differences in yield between hybrids with identical pedigrees may be largely accounted for by differences in percentage of stand. The use of proper seed stock, proper isolation and good detasseling are very necessary, but the maximum yield from a certain combination can be obtained only when the seed is processed and planted in such a manner that a high germination results. 13. The Banner Trophy was awarded to William Dockendorff & Sons on the basis of the performance of an entry of Iowa Hybrid 939 made by them in the Northern Section. This hybrid had a performance score of 108.73. It yielded 16.9 percent more than the average of the entries in its class and exceeded the yield of the average of the open-pollinated varieties by 20.8 bushels to the acre. This entry had a higher than average percentage of dropped ears and a lower than average percentage of lodged plants

Quantum Hall conductance of two-terminal graphene devices

Measurement and theory of the two-terminal conductance of monolayer and bilayer graphene in the quantum Hall regime are compared. We examine features of conductance as a function of gate voltage that allow monolayer, bilayer, and gapped samples to be distinguished, including N-shaped distortions of quantum Hall plateaus and conductance peaks and dips at the charge neutrality point. Generally good agreement is found between measurement and theory. Possible origins of discrepancies are discussed