Physical Sciences and Mathematics Commons^™

Wigner High-Electron-Correlation Regime Of Non-Uniform Density Systems: A Quantal-Density-Functional-Theory Study, Douglas Mortimer Achan

Dissertations, Theses, and Capstone Projects

The Wigner regime of a system of electrons in an external field is characterized by a low electron density and a high electron-interaction energy relative to the kinetic energy. The low correlation regime is in turn described by a high electron density and an electron-interaction energy smaller than the kinetic energy. The Wigner regime of a nonuniform electron density system is investigated via quantal density functional theory (QDFT). Within QDFT, the contributions of electron correlations due to the Pauli exclusion principle, Coulomb repulsion, and correlation-kinetic effects are separately delineated and explicitly defined. The nonuniform electron density system studied is that …

De Novo Design And Engineering Of Functional Metal And Porphyrin-Binding Protein Domains, Bernard Howard Everson

Dissertations, Theses, and Capstone Projects

In this work, I describe an approach to the rational, iterative design and characterization of two functional cofactor-binding protein domains. First, a hybrid computational/experimental method was developed with the aim of algorithmically generating a suite of porphyrin-binding protein sequences with minimal mutual sequence information. This method was explored by generating libraries of sequences, which were then expressed and evaluated for function. One successful sequence is shown to bind a variety of porphyrin-like cofactors, and exhibits light- activated electron transfer in mixed hemin:chlorin e6 and hemin:Zn(II)-protoporphyrin IX complexes. These results imply that many sophisticated functions such as cofactor binding and electron …

Geometry And Statistics Of Jammed Granular Matter, Mark Robert Kanner

Dissertations, Theses, and Capstone Projects

We use simulations of soft bidisperse disks to determine the properties of jammed packings and investigate the statistical mechanics of these systems. We have created a novel method for the classification of structural subunits of a packing and to calculate relevant physical quantities. The classification scheme is based on a 20 type decomposition of the Delaunay triangles extracted from the centers of the particles. Subunit frequencies are determined from geometrical properties and used to calculate the important macroscopic system quantities co-ordination number, packing fraction, and pressure. These relationships suggest that microscopic particle geometry plays an important role in observed macroscopic …

Strongly-Correlated 2d Electron Systems In Si-Mosfets, Shiqi Li

Dissertations, Theses, and Capstone Projects

Si-MOSFETs are basic building blocks of present-day integrated circuits. Above a threshold gate voltage, a layer of two-dimensional electrons is induced near the silicon-silicon dioxide interface of a Si-MOSFET. According to theory for noninteracting and weakly interacting electrons, no metallic state can exist in two dimensions in zero magnetic field in the limit of zero temperature. However, in strongly interacting electron systems the observation of a resistivity that changes from metallic to insulating temperature dependence has fueled a debate over whether this signals a quantum phase transition to a metallic phase in two dimensions.

In this thesis I will present …

Theories In Spin Dynamics Of Solid-State Nuclear Magnetic Resonance Spectroscopy, Eugene S. Mananga, Jalil Moghaddasi, Ajaz Sana, Mostafa Sadoqi

Publications and Research

This short review article presents theories used in solid-state nuclear magnetic resonance spectroscopy. Main theories used in NMR include the average Hamiltonian theory, the Floquet theory and the developing theories are the Fer expansion or the Floquet-Magnus expansion. These approaches provide solutions to the time-dependent Schrodinger equation which is a central problem in quantum physics in general and solid-state nuclear magnetic resonance in particular. Methods of these expansion schemes used as numerical integrators for solving the time dependent Schrodinger equation are presented. The action of their propagator operators is also presented. We highlight potential future theoretical and numerical directions such …

A Recipe For The Estimation Of Information Flow In A Dynamical System, Deniz Gencaga, Kevin H. Knuth, William B. Rossow

Publications and Research

Information-theoretic quantities, such as entropy and mutual information (MI), can be used to quantify the amount of information needed to describe a dataset or the information shared between two datasets. In the case of a dynamical system, the behavior of the relevant variables can be tightly coupled, such that information about one variable at a given instance in time may provide information about other variables at later instances in time. This is often viewed as a flow of information, and tracking such a flow can reveal relationships among the system variables. Since the MI is a symmetric quantity; an asymmetric …

A Principle Of Economy Predicts The Functional Architecture Of Grid Cells, Xue-Xin Wei, Jason Prentice, Vijay Balasubramanian

Publications and Research

Grid cells in the brain respond when an animal occupies a periodic lattice of ‘grid fields’ during navigation. Grids are organized in modules with different periodicity. We propose that the grid system implements a hierarchical code for space that economizes the number of neurons required to encode location with a given resolution across a range equal to the largest period. This theory predicts that (i) grid fields should lie on a triangular lattice, (ii) grid scales should follow a geometric progression, (iii) the ratio between adjacent grid scales should be √e for idealized neurons, and lie between 1.4 and 1.7 …

Differentiability Of Correlations In Realistic Quantum Mechanics, Alejandro Cabrera, Edson De Faria, Enrique Pujals, Charles Tresser

Publications and Research

We prove a version of Bell’s theorem in which the locality assumption is weakened. We start by assuming theoretical quantum mechanics and weak forms of relativistic causality and of realism (essentially the fact that observable values are well defined independently of whether or not they are measured). Under these hypotheses, we show that only one of the correlation functions that can be formulated in the framework of the usual Bell theorem is unknown. We prove that this unknown function must be differentiable at certain angular configuration points that include the origin. We also prove that, if this correlation is assumed …

Consequence Management: Evaluating And Developing International Responses To Nuclear And Radiological Disasters, Timothy Taylor

Dissertations and Theses

No abstract provided.

Automated Computation Of Scattering Amplitudes From Integrand Reduction To Monte Carlo Tools, Hans Van Deurzen, Gionata Luisoni, Pierpaolo Mastrolia, Giovanni Ossola, Zhibai Zhang

Publications and Research

After a general introduction about the calculation of one-loop scattering amplitudes via integrand-level techniques, which led to the construction of efficient and automated computational tools for NLO predictions, we briefly describe an approach to the reduction of scattering amplitudes based on integrand-level reduction via multivariate polynomial division also applicable beyond one-loop amplitudes. We also review the main features of the GoSam 2.0 automated framework for NLO calculations and show some of its application to Standard Model processes involving the production massive particles, such as the Higgs boson or top-quark pairs, obtained embedding of the virtual amplitudes produced by GoSam within …

Lectures On Thermodynamics And Statistical Mechanics, V P. Nair

Open Educational Resources

No abstract provided.