Interplay of charge, spin, orbital and lattice correlations in colossal magnetoresistance manganites

We derive a realistic microscopic model for doped colossal magnetoresistance manganites, which includes the dynamics of charge, spin, orbital and lattice degrees of freedom on a quantum mechanical level. The model respects the SU(2) spin symmetry and the full multiplet structure of the manganese ions within the cubic lattice. Concentrating on the hole doped domain ($0\le x\le 0.5$) we study the influence of the electron-lattice interaction on spin and orbital correlations by means of exact diagonalisation techniques. We find that the lattice can cause a considerable suppression of the coupling between spin and orbital degrees of freedom and show how changes in the magnetic correlations are reflected in dynamic phonon correlations. In addition, our calculation gives detailed insights into orbital correlations and demonstrates the possibility of complex orbital states.Comment: 8 pages, 12 figures; more detailed versio

A new model to describe the physics of VOPO

In the past different models for the magnetic salt vanadyl pyrophosphate (VOPO) were discussed. Neither a spin ladder nor an alternating chain are capable to describe recently measured magnetic excitations. In this paper we propose a 2D model that fits better to experimental observations.Comment: 4 pages, 6 figures include

Records on the vanishing of Fourier coefficients of Powers Of the Dedekind Eta Function

In this paper we significantly extend Serre's table on the vanishing properties of Fourier coefficients of odd powers of the Dedekind eta function. We address several conjectures of Cohen and Str\"omberg and give a partial answer to a question of Ono. In the even-power case, we extend Lehmer's conjecture on the coefficients of the discriminant function $\Delta$ to all non-CM-forms. All our results are supported with numerical data. For example all Fourier coefficients $a_9(n)$ of the $9$-th power of the Dedekind eta function are non-vanishing for $n \leq 10^{10}$. We also relate the non-vanishing of the Fourier coefficients of $\Delta^2$ to Maeda's conjecture.Comment: 13 page

Corporate governance, competition, the new international financial architecture and large corporations in emerging markets

This paper examines from the developing countries perspective important analytical and policy issues arising from: a) the current international discussions about corporate governance in relation to the New International Financial Architecture; b) changes in the international competitive environment being caused by the enormous international merger movement in advanced countries. The paper's main conclusions include: the thesis that the deeper causes of the Asian crisis were the flawed systems of corporate governance and a poor competitive environment in the affected countries is not supported by the evidence; emerging markets, as well as European countries, have successful records of fast long-term growth with different governance systems, indeed superior to those of Anglo-Saxon countries; corporate financing patterns in emerging markets in the 1990s continue to be anomalous, as they were in the 1980s; and the claim that developing country conglomerates are inefficient and financially precarious is not supported by evidence or analysis.Corporate governance, competition, emerging markets.

Corporate Governance, Competetion, The new International Financial Architecture and Large Corporations in Emerging Markets

This paper examines from the developing countries perspective important analytical and policy issues arising from: a) the current international discussions about corporate governance in relation to the New International Financial Architecture; b) changes in the international competitive environment being caused by the enormous international merger movement in advanced countries. The background to a) above is the emergence of corporate governance as a key issue in the current G7 proposals for the New International Financial Architecture. The G7 emphasis on corporate governance can be traced back to the thesis that the ‘deeper’ reasons for the Asian crisis lay in the microeconomic behaviour of corporations and businesses in the affected countries. The failings of the corporate governance mechanisms and distortions in the competitive process have received special scrutiny in such analyses. With respect to b) above, the context is that the largest corporations in advanced countries are currently in the process of potentially cartelising the world market place through a spate of cross-border mergers and take-overs. This huge merger movement raises serious policy concerns for developing countries. The paper's main conclusions are: 1. The thesis that the deeper causes of the Asian crisis were the flawed systems of corporate governance and a poor competitive environment in the affected countries is not supported by evidence. 2. The Anglo-Saxon model of widely held corporations with dispersed share ownership is by far the exception in developing countries and in much of continental Europe. Empirical evidence suggests that emerging markets, as well as European countries such as Italy, Sweden or Germany have successful records of fast long-term growth with different governance systems, indeed superior to those of Anglo-Saxon countries. 3. Empirical evidence does not support the view that the Asian crisis 1997 to 1999 was caused by crony capitalism. 4. Corporate financing patterns in emerging markets in the 1990s were broadly similar to those observed in the 1980s. Unlike their counterparts in advanced countries, large developing countries firms continued to rely overwhelmingly on external sources to finance their growth of total assets. 5. The analysis of this paper does not support the claim that developing country conglomerates are inefficient, financially precarious and necessarily create moral hazard. It also indicates that contrary to widely held beliefs, product market competition in emerging countries is no less intense than in advanced economies. Acknowledgements Please do not quote without permission from the authors. Comments are most welcome.Competition; Corporate Governance; Emerging Markets

The Kernel Polynomial Method

Efficient and stable algorithms for the calculation of spectral quantities and correlation functions are some of the key tools in computational condensed matter physics. In this article we review basic properties and recent developments of Chebyshev expansion based algorithms and the Kernel Polynomial Method. Characterized by a resource consumption that scales linearly with the problem dimension these methods enjoyed growing popularity over the last decade and found broad application not only in physics. Representative examples from the fields of disordered systems, strongly correlated electrons, electron-phonon interaction, and quantum spin systems we discuss in detail. In addition, we illustrate how the Kernel Polynomial Method is successfully embedded into other numerical techniques, such as Cluster Perturbation Theory or Monte Carlo simulation.Comment: 32 pages, 17 figs; revised versio

Archiving Latinxs on the U.S. Great Plains - Coming to the Plains

This panel examines the intricacies of archiving Latinxs in the US Great Plains. Latinx communities comprise a significant portion of the area’s population, yet regional archival holdings often under-represent these groups’ experiences and historical contributions. This panel will describe three universities’ approaches toward addressing this disparity, beginning with bilingual oral history projects “Voces of a Pandemic”, which explores the impact of COVID-19 on Latinx communities near Omaha, and “Coming to the Plains”, which examines immigration experiences of Latinx people in central Nebraska, conducted by the University of Nebraska at Omaha and University of Nebraska at Kearney respectively. The panel also recounts efforts by the Southwest Collection at Texas Tech University to archive the legacy of Latinx communities on Texas’s South Plains, namely through its “Recuerdos del Ayer” project that centers on building relationships with South Plains Latinx communities, incorporating translation of archival materials, creation of online and interactive exhibits, and expanding Latinx outreach efforts. Presenters: Robert Weaver, Texas Tech University Zach Hernández, Texas Tech University Wendy Guerra, University of Nebraska at Omaha Laurinda Weisse, University of Nebraska at Kearne