Superconductivity and antiferromagnetism in the two-dimensional Hubbard model: a variational study

A variational ground state of the repulsive Hubbard model on a square lattice is investigated numerically for an intermediate coupling strength (U = 8t) and for moderate sizes (from 6 x 6 to 10 x 10). Our ansatz is clearly superior to other widely used variational wave functions. The results for order parameters and correlation functions provide new insight for the antiferromagnetic state at half filling as well as strong evidence for a superconducting phase away from half filling.Comment: 4 pages, 4 figure

When For Better Is For Worse: Immigration Law’s Gendered Impact on Foreign Polygamous Marriage

The United States has banned polygamous immigrants since the late nineteenth century. Enacted amid isolationist fears that an influx of polygamists would cause moral deterioration, the polygamy bar remains a resolute, if often overlooked, feature of modern immigration law. The current immigration scheme continues this tradition, rendering immigrants who intend to practice polygamy in the United States categorically ineligible for legal-permanent-resident status. As a result, the immigration bar allows polygamous men to immigrate with a wife of their choosing and the children from each of their marriages. Their other wives, however, are deemed inadmissible to the United States. This Note explores the immigration bar’s disproportionate effect on the foreign wives of polygamous immigrants. In addition to precluding the other wives of polygamous immigrants from legal permanent-resident status, the current immigration bar also renders such women ineligible for humanitarian ingress. After offering a comparative analysis of how Canada and the United Kingdom reconcile their respective policies against polygamy with the burgeoning question of women’s rights, this Note proposes that Congress likewise treat foreign women in polygamous unions with a degree of equity

Superconductivity in the two-dimensional Hubbard model?

A refined variational wave function for the two-dimensional repulsive Hubbard model is studied numerically, with the aim of approaching the difficult crossover regime of intermediate values of U. The issue of a superconducting ground state with d-wave symmetry is investigated for an average electron density n=0.8125 and for U=8t. Due to finite-size effects a clear-cut answer to this fundamental question has not yet been reached.Comment: 5 pages, 1 figure, Proc. 30th Int. Conf. of Theoretical Physics, Ustron, Poland, 2006, to be published in phys. stat. so

Junior Recital, Kevin Eichenberger, jazz bass

The presentation of this junior recital will fulfill in part the requirements for the Bachelor of Music degree in Jazz Studies. Kevin Eichenberger studies jazz bass with Victor Dvoskin

Variational ground states of the two-dimensional Hubbard model

Recent refinements of analytical and numerical methods have improved our understanding of the ground-state phase diagram of the two-dimensional (2D) Hubbard model. Here we focus on variational approaches, but comparisons with both Quantum Cluster and Gaussian Monte Carlo methods are also made. Our own ansatz leads to an antiferromagnetic ground state at half filling with a slightly reduced staggered order parameter (as compared to simple mean-field theory). Away from half filling, we find d-wave superconductivity, but confined to densities where the Fermi surface passes through the antiferromagnetic zone boundary (if hopping between both nearest-neighbour and next-nearest-neighbour sites is considered). Our results agree surprisingly well with recent numerical studies using the Quantum Cluster method. An interesting trend is found by comparing gap parameters (antiferromagnetic or superconducting) obtained with different variational wave functions. They vary by an order of magnitude and thus cannot be taken as a characteristic energy scale. In contrast, the order parameter is much less sensitive to the degree of sophistication of the variational schemes, at least at and near half filling.Comment: 18 pages, 4 figures, to be published in New J. Phy

Foreign Ownership of Agricultural Land in the United States: A Case Study Concerning the 2023 Grassroots Policy and Legislative Landscape

Historically, foreign ownership of land in the United States has existed for centuries. Many state laws expressly allow for foreign ownership of agricultural land in their state. However, this study will find that a push to amend these laws has begun in recent years in state and federal legislatures. Grassroots member-focused agricultural organizations, representative of the agricultural community, have also seen a shift in member-developed policy. This shift is toward an attitude of concern and increased oversight of foreign land investment. From the data gathered, it can be inferred that public awareness in the agricultural community is increasing concerning foreign ownership of agricultural land in the United States and is trending toward an attitude of concern, increased monitoring of the issue, and in some cases, outright prohibition

Senior Recital, Kevin Eichenberger, double bass

The presentation of this senior recital will fulfill in part the requirements for the Bachelor of Music degree in Jazz Studies. Kevin Eichenberger studies double bass with Victor Dvoskin

Foreign Ownership of Agricultural Land in the United States: A Case Study Concerning the 2023 Grassroots Policy and Legislative Landscape

Historically, foreign ownership of land in the United States has existed for centuries. Many state laws expressly allow for foreign ownership of agricultural land in their state. However, this study will find that a push to amend these laws has begun in recent years in state and federal legislatures. Grassroots member-focused agricultural organizations, representative of the agricultural community, have also seen a shift in member-developed policy. This shift is toward an attitude of concern and increased oversight of foreign land investment. From the data gathered, it can be inferred that public awareness in the agricultural community is increasing concerning foreign ownership of agricultural land in the United States and is trending toward an attitude of concern, increased monitoring of the issue, and in some cases, outright prohibition