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Title: Stochastic processes in the social sciences: markets, prices and wealth distributions.
Creator: Romero, Natalia E., Charles E. Schmidt College of Science, Department of Physics
Abstract/Description: The present work uses statistical mechanics tools to investigate the dynamics of markets, prices, trades and wealth distribution. We studied the evolution of market dynamics in different stages of historical development by analyzing commodity prices from two distinct periods : ancient Babylon, and medieval and early modern England. We find that the first-digit distributrions of both Babylon and England commodity prices follow Benford's Law, indicating that the data represent empirical...
Show moreThe present work uses statistical mechanics tools to investigate the dynamics of markets, prices, trades and wealth distribution. We studied the evolution of market dynamics in different stages of historical development by analyzing commodity prices from two distinct periods : ancient Babylon, and medieval and early modern England. We find that the first-digit distributrions of both Babylon and England commodity prices follow Benford's Law, indicating that the data represent empirical observations typically arising from a free market. Further, we find that the normalized prices of both Babylon and England agricultural commodities are characterized by stretched exponential distributions, and exhibit persistent correlations of a power law type over long periods of up to several centuries, in contrast to contemporary markets. Our findings suggest that similar market interactions may underlie the dynamics of ancient agricultural commodity prices, and that these interactions may remain stable across centuries. To further investigate the dynamics of markets, we present the analogy between transfers of money between individuals and the transfer of energy through particle collisions by means of the kinetic theory of gases. We introduce a theoretical framework of how micro rules of trading lead to the emergence of income and wealth distribution. Particularly, we study the effects of different types of distribution of savings/investments among individuals in a society and different welfare/subsidies redistribution policies. Results show that while considering savings propensities, the models approach empirical distributions of wealth quite well. The effect of redistribution better captures specific features of the distributions which earlier models failed to do. Moreover, the models still preserve the exponential decay observed in empirical income distributions reported by tax data and surveys.
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Date Issued: 2012
PURL: http://purl.flvc.org/FAU/3352825
Subject Headings: Stochastic processes, Mathematical models, Consumption (Economics), Mathematical models, Business cycles, Mathematical models, Statics and dynamics (Social sciences), Mathematical models
Format: Document (PDF)

Title: Computational methods in metallic alloys within multiple scattering theory.
Creator: Rusanu, Aurelian, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Physics
Abstract/Description: Designing materials, particularly at the nano-scale, is an important scientific research area. It includes a large spectrum of basic science and technological developments. In order to provide results that are relevant to real materials, quantum mechanical simulations involving thousands to millions of atoms must be carried out. The locally self-consistent multiple scattering (LSMS) method is the method of choice for such calculations because it has a technical feature called order-N scaling....
Show moreDesigning materials, particularly at the nano-scale, is an important scientific research area. It includes a large spectrum of basic science and technological developments. In order to provide results that are relevant to real materials, quantum mechanical simulations involving thousands to millions of atoms must be carried out. The locally self-consistent multiple scattering (LSMS) method is the method of choice for such calculations because it has a technical feature called order-N scaling. We describe an implementation of the LSMS for massively parallel supercomputers using k-space and real-space methods. For magnetic materials, the constrained local moment approach and the exchange interaction method are used. We demonstrate our approach by calculating the electronic and magnetic structure of an iron nano-particle embedded in an iron aluminide crystal matrix.
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Date Issued: 2005
PURL: http://purl.flvc.org/fcla/dt/12176
Subject Headings: Physics, Condensed Matter
Format: Document (PDF)

Title: Cosmological studies with spatially homogenous models and quantum field effects in Kantowski-Sachs universe.
Creator: Sabir, Abdenour, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Physics
Abstract/Description: Perhaps constructing a complete theory of quantum gravity, has been one of the greatest challenges for theoretical physicists in the last few decades, a theory that would reconcile general relativity and quantum mechanics. Addressing this issue, we are drawing a parallel between the Schrodinger and Klein-Gordon equation in quantum mechanics and Schrodinger-based or Klein-Gordon based wave equation in canonical quantum gravity. In particular we analyze the quantum geometrodynamics Schrodinger...
Show morePerhaps constructing a complete theory of quantum gravity, has been one of the greatest challenges for theoretical physicists in the last few decades, a theory that would reconcile general relativity and quantum mechanics. Addressing this issue, we are drawing a parallel between the Schrodinger and Klein-Gordon equation in quantum mechanics and Schrodinger-based or Klein-Gordon based wave equation in canonical quantum gravity. In particular we analyze the quantum geometrodynamics Schrodinger equation for a homogeneous cosmological model and we study the quantum field effects for the &PHgr;6 scalar field in Kantowski-Sachs universe. In essence, we present a unified view of quantum gravity by establishing a parallel between our study and the usual quantum mechanics. Thus, the first part of this dissertation deals with the quantization of Bianchi type IX space-time where the concept of time is derived by imposing the constraints as expectation values over the true dynamical-degrees of freedom of the gravitational field. Thus, we obtained a Schrodinger type wave equation instead of the Wheeler-DeWitt which is associated with the problem of time in quantum gravity [1]. The main technical difference between our proposed equation and other quantum cosmology approaches is in our treatment of the constraints. Ordinarily, the equation cannot be solved simply by separating the coordinates variables, and only under some specific conditions imposed on the background that one may obtain exact analytical expressions. In the second part, we evaluated the one-loop renormalized effective potential for the massive self interacting &PHgr;6 theory the spatially homogenous and anisotropic Kantowki-Sachs Universe. We concluded that regularizing the theory in (3 + 1) dimensional space-time may not be possible. Finally, we looked at the time evolution of the critical temperature that is associated with our model.
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Date Issued: 2005
PURL: http://purl.flvc.org/fau/fd/FADT12125
Subject Headings: Physics, General
Format: Document (PDF)

Title: MODIFIED f(R) THEORY OF GRAVITY: AN ALTERNATIVE GRAVITY THEORY.
Creator: Saiedi, Hamidreza, Wille, Luc T., Florida Atlantic University, Department of Physics, Charles E. Schmidt College of Science
Abstract/Description: Through the variational principle, we review the gravitational field equations in Einstein gravity and modified f(R) gravity theories. Metric and Palatini formalisms are two different approaches that are employed to obtain the field equations in the context of f(R) theory of gravity. In this framework, we attempt to investigate the energy conditions in Friedmann-Lemaitre-Robertson-Walker (FLRW) metric using the Raychaudhuri equation. Then, we focus on wormhole geometries and their...
Show moreThrough the variational principle, we review the gravitational field equations in Einstein gravity and modified f(R) gravity theories. Metric and Palatini formalisms are two different approaches that are employed to obtain the field equations in the context of f(R) theory of gravity. In this framework, we attempt to investigate the energy conditions in Friedmann-Lemaitre-Robertson-Walker (FLRW) metric using the Raychaudhuri equation. Then, we focus on wormhole geometries and their thermodynamics behavior in Palatini and metric versions of modified f(R) gravity, separately. To violate the null and the weak energy conditions, wormhole spacetimes need an exotic matter. It has been shown that in f(R) gravity the matter threading the wormholes serves the energy conditions, and it is the derivative terms of the higher order curvature that may be explained as a gravitational fluid, that supports these geometries. Therefore, in f(R) gravity theory it is not required to introduce exotic matter in order to have traversable wormholes. In the framework of metric and Palatini f(R) gravity, we investigate the thermodynamic properties of evolving wormholes. We obtain an expression for the variation of the total entropy to discuss the thermodynamic behavior of wormhole spacetimes. The investigation has been extended to the apparent and event horizons. Eventually, we apply the radius of these horizons to determine the validity of the generalized second law of thermodynamics. This law states that the rate of change of total entropy is positive.
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Date Issued: 2022
PURL: http://purl.flvc.org/fau/fd/FA00013879
Subject Headings: Gravity, Gravitational fields--Mathematics, Wormholes (Physics)
Format: Document (PDF)

Title: Discerning protein similarities and folding dynamics through methods in statistical physics and molecular dynamics simulations.
Creator: Sardiu, Mihaela E., Florida Atlantic University, Charles E. Schmidt College of Science, Department of Physics
Abstract/Description: One of the most important tasks in biophysics is to understand proteins. It has long been observed that sequence similarity, structural similarity, and functional similarity among proteins are highly correlated. Inspired by this observation, sequence comparison is often employed to retrieve similar/related protein sequences. However, the central issue of assigning statistical significance to the proteins retrieved remains a challenging problem. How a directed polymer/percolation model can...
Show moreOne of the most important tasks in biophysics is to understand proteins. It has long been observed that sequence similarity, structural similarity, and functional similarity among proteins are highly correlated. Inspired by this observation, sequence comparison is often employed to retrieve similar/related protein sequences. However, the central issue of assigning statistical significance to the proteins retrieved remains a challenging problem. How a directed polymer/percolation model can shed light in understanding the statistics of global sequence alignments, which is also the fundamental building block for multiple sequence alignment in many multiple alignment applications, is revealed in my thesis. In terms of understanding proteins' specific functionality, it is essential to know how protein sequences determine their unique three dimensional structures and folding kinetics. A careful analysis of the amino acid arrangements in proteins with known structures may provide insights to this issue. In my thesis, I will present a statistical analysis on tertiary contacts to gain more accurate estimates of the preference of amino acid interactions. This analysis reveals an unusually large contact between cysteines, indicating an effective attractive potential among them. The nontrivial role of cysteine-cysteine interactions in protein folding is discussed in my thesis. A new concept termed target-focusing is also introduced.
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Date Issued: 2005
PURL: http://purl.flvc.org/fcla/dt/12152
Subject Headings: Statistics, Physics, Molecular, Biophysics, General
Format: Document (PDF)

Title: Dosimetric and Radiobiological Plan Evaluation Parameters for Fractionated High-Dose Rate GYN Brachytherapy.
Creator: Shojaei, Marjan, Pella, Silvia, Leventouri, Theodora, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Physics
Abstract/Description: Intracavitary high-dose-rate brachytherapy (HDRBT) is a treatment option for endometrial cancer, depending on the cancer stage. Because of the steep high dose gradient of HDRBT, very small differences in the treatment plans, surrounding organ’s anatomy, or procedures during the treatment could potentially cause significant dose variation to the tumor, as well as organs at risks (OAR) nearby the treatment area, which could result in unwanted radiobiological side effects. In this retrospective...
Show moreIntracavitary high-dose-rate brachytherapy (HDRBT) is a treatment option for endometrial cancer, depending on the cancer stage. Because of the steep high dose gradient of HDRBT, very small differences in the treatment plans, surrounding organ’s anatomy, or procedures during the treatment could potentially cause significant dose variation to the tumor, as well as organs at risks (OAR) nearby the treatment area, which could result in unwanted radiobiological side effects. In this retrospective study, the radiobiological plan evaluation parameters Equivalent Uniform Dose (EUD), Normal Tissue Complication Probability (NTCP) are used as assessment tools to evaluate HDRBT plans. Furthermore, gynecological applicator position in the coordinate system, and possible dose variations to the tumor and critical organs from the initial fraction in comparison with subsequent fractions over the entire multi fractionated treatment are studied. The evaluations were performed for 118 HDR treatment plans for 30 patients by registration of the subsequent treatment plans into the initial CT-image guided plan. Dose fractionation regimens varied from 4Gy to 7Gy per fraction, 1 or 2 fractions per week, depending on the cancer stage. Our results demonstrate no significant radiobiological impacts on organs at risks (OAR). In addition, the results of the applicator positions’ study indicate that improvement of immobilization and localization devices are recommended.
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Date Issued: 2018
PURL: http://purl.flvc.org/fau/fd/FA00013144
Subject Headings: Brachytherapy, Radiobiology, Radiation dosimetry--Evaluation
Format: Document (PDF)

Title: New method of collecting output factors for commissioming linear accelerators with special emphasis on small fields and intensity modualted readiation therapy.
Creator: Smith, Cindy, Pella, Silvia, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Physics
Abstract/Description: Common methods for commissioning linear accelerators often neglect beam data for small fields. Examining the methods of beam data collection and modeling for commissioning linear accelerators revealed little to no discussion of the protocols for fields smaller than 4 cm x 4 cm. This leads to decreased confidence levels in the dose calculations and associated monitor units (MUs) for Intensity Modulated Radiation Therapy (IMRT). The parameters of commissioning the Novalis linear accelerator ...
Show moreCommon methods for commissioning linear accelerators often neglect beam data for small fields. Examining the methods of beam data collection and modeling for commissioning linear accelerators revealed little to no discussion of the protocols for fields smaller than 4 cm x 4 cm. This leads to decreased confidence levels in the dose calculations and associated monitor units (MUs) for Intensity Modulated Radiation Therapy (IMRT). The parameters of commissioning the Novalis linear accelerator (linac) on the Eclipse Treatment Planning System (TPS) led to the study of challenges collecting data for very small fields. The focus of this thesis is the examination of the protocols for output factor collection and their impact on dose calculations by the TPS for IMRT treatment plans. Improving output factor collection methods, led to significant improvement in absolute dose calculations which correlated with the complexity of the plans.
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Date Issued: 2014
PURL: http://purl.flvc.org/fau/fd/FA00004161
Subject Headings: Coherence (Nuclear physics), Linear accelerators in medicine, Medical physics, Nuclear medicine, Particle beams, Radiation -- Dosage, Radiotherapy -- Positioning
Format: Document (PDF)

Title: MEASUREMENTS OF TERRESTRIAL OH ABUNDANCES BY SPECTROSCOPIC OBSERVATION OF RESONANCE ABSORPTION OF SUNLIGHT.
Creator: SPERANZA, PATRICK DANIEL, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Physics
Abstract/Description: Measurements of the atmospheric hydroxyl radical (OH) abundance were made at Boca Raton, Florida, (26° 22' N, 80° 6' W) during the period March 14 through April 9, 1977. Observations were made on the P1(1) line of the A^2sigma+ - x^2pi(0,0) rotation band of OH at 3081.7A. By the use of the high resolution Pepsios (poly-etalon pressure scanning interferometric optical spectrometer) spectrometer, the narrow absorption curve due to terrestrial OH was distinguished from the broad solar Fraunhofer...
Show moreMeasurements of the atmospheric hydroxyl radical (OH) abundance were made at Boca Raton, Florida, (26° 22' N, 80° 6' W) during the period March 14 through April 9, 1977. Observations were made on the P1(1) line of the A^2sigma+ - x^2pi(0,0) rotation band of OH at 3081.7A. By the use of the high resolution Pepsios (poly-etalon pressure scanning interferometric optical spectrometer) spectrometer, the narrow absorption curve due to terrestrial OH was distinguished from the broad solar Fraunhofer line. Measurements of the amount of atmospheric OH absorption indicated an average vertical column abundance of (2.0 +- 0.8) (10^13) molecules/cm^2 for this observation period.
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Date Issued: 1977
PURL: http://purl.flvc.org/fcla/dt/13848
Subject Headings: Hydroxides--Absorption and adsorption, Atmospheric ozone
Format: Document (PDF)

Title: Reduced representation of neural networks.
Creator: Stefanescu, Roxana A., Charles E. Schmidt College of Science, Department of Physics
Abstract/Description: Experimental and computational investigations addressing how various neural functions are achieved in the brain converged in recent years to a unified idea that the neural activity underlying most of the cognitive functions is distributed over large scale networks comprising various cortical and subcortical areas. Modeling approaches represent these areas and their connections using diverse models of neurocomputational units engaged in graph-like or neural field-like structures. Regardless of...
Show moreExperimental and computational investigations addressing how various neural functions are achieved in the brain converged in recent years to a unified idea that the neural activity underlying most of the cognitive functions is distributed over large scale networks comprising various cortical and subcortical areas. Modeling approaches represent these areas and their connections using diverse models of neurocomputational units engaged in graph-like or neural field-like structures. Regardless of the manner of network implementation, simulations of large scale networks have encountered significant difficulties mainly due to the time delay introduced by the long range connections. To decrease the computational effort, it is common to assume severe approximations to simplify the descriptions of the neural dynamics associated with the system's units. In this dissertation we propose an alternative framework allowing the prevention of such strong assumptions while efficiently representing th e dynamics of a complex neural network. First, we consider the dynamics of small scale networks of globally coupled non-identical excitatory and inhibitory neurons, which could realistically instantiate a neurocomputational unit. We identify the most significant dynamical features the neural population exhibits in different parametric configuration, including multi-cluster dynamics, multi-scale synchronization and oscillator death. Then, using mode decomposition techniques, we construct analytically low dimensional representations of the network dynamics and show that these reduced systems capture the dynamical features of the entire neural population. The cases of linear and synaptic coupling are discussed in detail. In chapter 5, we extend this approach for spatially extended neural networks., We consider the dynamical behavior of a neural field-like network, which incorporates many biologically realistic characteristics such as heterogeneous local and global connectivity as well as dispersion in the neural membrane excitability. We show that in this case as well, we can construct a reduced representation, which may capture well the dynamical features of the full system. The method outlined in this dissertation provides a consistent way to represent complex dynamical features of various neural networks in a computationally efficient manner.
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Date Issued: 2009
PURL: http://purl.flvc.org/FAU/369387
Subject Headings: Molecular neurobiology, Neural networks (Neurobiology), Brain, Mathematical models, Cognitive neuroscience, Recognition (Psychology)
Format: Document (PDF)

Title: Improved Methodology of Static HDMLC Virtual Cone based Rapid Arcs for Stereotactic Ablative Radiotherapy.
Creator: Stevens, Ryan, Shang, Charles, Muhammad, Wazir, Florida Atlantic University, Department of Physics, Charles E. Schmidt College of Science
Abstract/Description: Physical cones equipped on GammaKnife, Cyberknife, and C-arm linacs have been the standard practice in Stereotactic Ablative Radiotherapy (SART) for small intracranial lesions, such as treating trigeminal or glossopharyngeal neuralgia targets. The advancement of high-definition multi-leaf collimators (HDMLC), treatment planning systems, and small field dosimetry now allows for treatment without the need for an auxiliary mounted physical cone. This treatment type uses the “virtual cone”, a...
Show morePhysical cones equipped on GammaKnife, Cyberknife, and C-arm linacs have been the standard practice in Stereotactic Ablative Radiotherapy (SART) for small intracranial lesions, such as treating trigeminal or glossopharyngeal neuralgia targets. The advancement of high-definition multi-leaf collimators (HDMLC), treatment planning systems, and small field dosimetry now allows for treatment without the need for an auxiliary mounted physical cone. This treatment type uses the “virtual cone”, a permanent high-definition MLC, arrangement to deliver “very small fields” with comparable spherical dose distributions to physical cones. The virtual cone therapy, on a Varian Edge™ linac using multiple non-coplanar arcs with static HDMLCs, is a comparable technique that can be used to treat small intracranial neuralgia or other small lesions. In this investigation, two flattening filter free (FFF) photon beams, 6MV FFF and 10MV FFF, were tested for optimal delivery and safety conditions for treating intracranial lesions. The virtual cone method on a Varian Edge™ Linear accelerator using rapid arc stereotactic radiosurgery was used to treat cranial neuralgia for chronic pain for six patients. Absolute dose, relative dose measurements, and monitor units were the main characteristics that were examined to decide which energy was the best for treatment. Source-to-axis distances (SAD) of 100cm measurements were taken at depths of 10cm and 5cm, respectively.
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Date Issued: 2020
PURL: http://purl.flvc.org/fau/fd/FA00013630
Subject Headings: Radiotherapy, Radiation dosimetry, Stereotaxic Techniques
Format: Document (PDF)

Title: Development of a Monte Carlo Simulation Model for Varian ProBeam Compact Single-Room Proton Therapy System using GEANT4.
Creator: String, Shawn, Muhammad, Wazir, Shang, Charles, Florida Atlantic University, Department of Physics, Charles E. Schmidt College of Science
Abstract/Description: Proton therapy with pencil beam scanning technique is a novel technique to treat cancer patients due to its unique biophysical properties. However, a small error in dose calculation may lead towards undesired greater uncertainties in planed doses. This project aims to create a simulation model of Varian ProBeam Compact using the GEANT4 Monte Carlo simulation tool kit. Experimental data from the first clinical ProBeam Compact system at South Florida Proton Therapy Institute was used to...
Show moreProton therapy with pencil beam scanning technique is a novel technique to treat cancer patients due to its unique biophysical properties. However, a small error in dose calculation may lead towards undesired greater uncertainties in planed doses. This project aims to create a simulation model of Varian ProBeam Compact using the GEANT4 Monte Carlo simulation tool kit. Experimental data from the first clinical ProBeam Compact system at South Florida Proton Therapy Institute was used to validate the simulation model. A comparison was made between the experimental and simulated Integrated Depth-Dose curves using a 2%/2mm gamma index test with 100% of points passing. The beam spot standard deviation sizes (s!) were compared using percent deviation. All simulated s! matched the experimental s! within 2.5%, except 70 and 80 MeV. The model can be used to develop a more comprehensive model as an independent dose verification tool and further investigate dose distribution.
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Date Issued: 2020
PURL: http://purl.flvc.org/fau/fd/FA00013547
Subject Headings: Proton Therapy, Monte-Carlo-Simulation, Radiotherapy Dosage
Format: Document (PDF)

Title: Narrow and broad band photoluminescence spectroscopy of Cd(x)Zn(1-x)Se semiconductor.
Creator: Sweiti, Ayman, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Physics
Abstract/Description: In this dissertation I have used photoluminescence (PL) spectrometric analysis to measure the temperature dependence of the spectral features of the direct band gap semiconductor CdxZn1-xSe , for two nominal concentrations x = 0.25, 0.50, in the temperature range 25--300 K. The effective concentrations were obtained from analysis of the spectra. The parameters that describe the temperature dependence of the line width broadening have been evaluated using different models. The PL broadband...
Show moreIn this dissertation I have used photoluminescence (PL) spectrometric analysis to measure the temperature dependence of the spectral features of the direct band gap semiconductor CdxZn1-xSe , for two nominal concentrations x = 0.25, 0.50, in the temperature range 25--300 K. The effective concentrations were obtained from analysis of the spectra. The parameters that describe the temperature dependence of the line width broadening have been evaluated using different models. The PL broadband characteristics of Cd0.22Zn0.78Se and Cd0.41Zn0.59Se are also investigated within the energy range 1.36--2.40 eV and temperature range 25--305 K. Two broad bands are observed, the higher energy band I centered at 1.991 and 1.773 eV, the lower energy band II centered at 1.844 and 1.705 eV for the two samples, respectively. The emission bands are attributed to donor-acceptor pair transitions. The energy scheme shows two donors and two acceptor levels, the binding energies of the donors for Cd 0.22Zn0.78Se are 29 and 208 meV below the conduction band, the binding energies of the acceptors 472 and 511 meV above the valence band. The binding energies of the donors for Cd0.41Zn 0.59Se are 27 and 137 meV, the binding energies of the acceptors 393 and 423 eV. A significant blue shift in energy with increasing temperature was observed for the lower energy band. The ionization temperatures for the deep donors are 279 and 287 K for Cd0.22Zn0.78Se and Cd0.41Zn0.59Se, respectively.
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Date Issued: 2003
PURL: http://purl.flvc.org/fau/fd/FADT12075
Subject Headings: Chemistry, Analytical, Physics, Condensed Matter
Format: Document (PDF)

Title: Spatiotemporal patterns of neural fields in a spherical cortex with general connectivity.
Creator: Tayefeh, Vahid, Fuchs, Armin, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Physics
Abstract/Description: The human brain consists of billions of neurons and these neurons pool together in groups at different scales. On one hand, these neural entities tend to behave as single units and on the other hand show collective macroscopic patterns of activity. The neural units communicate with each other and process information over time. This communication is through small electrical impulses which at the macroscopic scale are measurable as brain waves. The electric field that is produced collectively...
Show moreThe human brain consists of billions of neurons and these neurons pool together in groups at different scales. On one hand, these neural entities tend to behave as single units and on the other hand show collective macroscopic patterns of activity. The neural units communicate with each other and process information over time. This communication is through small electrical impulses which at the macroscopic scale are measurable as brain waves. The electric field that is produced collectively by macroscopic groups of neurons within the brain can be measured on the surface of the skull via a brain imaging modality called Electroencephalography (EEG). The brain as a neural system has variant connection topology, in which an area might not only be connected to its adjacent neighbors homogeneously but also distant areas can directly transfer brain activity [16]. Timing of these brain activity communications between different neural units bring up overall emerging spatiotemporal patterns. The dynamics of these patterns and formation of neural activities in cortical surface is influenced by the presence of long-range connections between heterogeneous neural units. Brain activity at large-scale is thought to be involved in the information processing and the implementation of cognitive functions of the brain. This research aims to determine how the spatiotemporal pattern formation phenomena in the brain depend on its connection topology. This connection topology consists of homogeneous connections in local cortical areas alongside the couplings between distant functional units as heterogeneous connections. Homogeneous connectivity or synaptic weight distribution representing the large-scale anatomy of cortex is assumed to depend on the Euclidean distance between interacting neural units. Altering characteristics of inhomogeneous pathways as control parameters guide the brain pattern formation through phase transitions at critical points. In this research, linear stability analysis is applied to a macroscopic neural field in a one-dimensional circular and a twodimensional spherical model of the brain in order to find destabilization mechanism and subsequently emerging patterns.
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Date Issued: 2018
PURL: http://purl.flvc.org/fau/fd/FA00013119
Subject Headings: Cerebral cortex, Neural circuitry, Electroencephalography, Neural fields, Spatiotemporal patterns
Format: Document (PDF)

Title: AN IMPROVED NEUTRINO TRANSPORT ALGORITHM FOR THE CHIMERA SUPERNOVA CODE.
Creator: Tejedor, Ruben Dario, Bruenn, Stephen W., Tichy, Wolfgang, Florida Atlantic University, Department of Physics, Charles E. Schmidt College of Science
Abstract/Description: Core-Collapse Supernovae (CCSNe) are some of the most powerful events in the universe liberating an astonishing 3×1053 ergs of the gravitational binding energy released by the collapse of the stellar core to a nascent neutron star (PNS) that is formed in these events. The visible display is capable of outshining the entire galaxy where it inhabits. Most of this energy, ~ 99%, is carried away by neutrinos of all flavors, however. According to the favored theory of CCSNe, the production and...
Show moreCore-Collapse Supernovae (CCSNe) are some of the most powerful events in the universe liberating an astonishing 3×1053 ergs of the gravitational binding energy released by the collapse of the stellar core to a nascent neutron star (PNS) that is formed in these events. The visible display is capable of outshining the entire galaxy where it inhabits. Most of this energy, ~ 99%, is carried away by neutrinos of all flavors, however. According to the favored theory of CCSNe, the production and transport of neutrinos from the dense core through the less dense mantle is believed to deposit energy in the mantle and thereby initiate the supernova explosion. Numerically modeling these events realistically to validate the model therefore requires an accurate neutrino transport algorithm coupled to sophisticated neutrino microphysics to compute the emission, transport, and energy deposition of neutrinos. The CHIMERA code is a radiation-hydrodynamics code that has been developed to numerically model CCSNe in multiple spatial dimensions. The neutrino transport algorithm currently incorporated in CHIMERA is based upon the Multigroup Flux-Limited Diffusion (MGFLD) method. This current method basically uses only the zeroth angular moment of the Boltzmann equation and closes the system with terms dropped from the first angular moment to produce a diffusion-like equation. A flux-limiter is added to interpolate between the diffusive and free-streaming regimes, and to prevent the algorithm from computing acausal, i.e., faster than light transport, in regions where the neutrino mean free paths are large.
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Date Issued: 2023
PURL: http://purl.flvc.org/fau/fd/FA00014293
Subject Headings: Supernovae, Neutrinos, Astrophysics
Format: Document (PDF)

Title: Magnetic, thermodynamic, and structural studies of manganese oxides.
Creator: Terashita, Hirotoshi, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Physics
Abstract/Description: Magnetic, thermodynamic, and structural properties of the manganese oxides La1-xCa xMnO3 are studied. Neutron powder diffraction reveals two distinct crystallographic phases as well as two magnetic (ferromagnetic and antiferromagnetic) phases for 0.08
Show moreMagnetic, thermodynamic, and structural properties of the manganese oxides La1-xCa xMnO3 are studied. Neutron powder diffraction reveals two distinct crystallographic phases as well as two magnetic (ferromagnetic and antiferromagnetic) phases for 0.08 < x < 0.14. Details of the compositional dependence of the phase fractions is discussed in the context of local ferromagnetism. Comparisons of magnetic and crystallographic properties are made to the analogous electron-doped Ca1- yLayMnO3 (0 < y < 0.20) system. Thermodynamic properties of La1- xCaxMnO 3 (0 < x < 0.54) are investigated for possible applications in magnetic refrigeration. A maximum magnetic entropy change of 5.5 J/kg K and a corresponding temperature change of 2 K are estimated for x = 0.28. The magnetocaloric effect in antiferromagnetic and charge-ordering compounds is found to be small.
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Date Issued: 2005
PURL: http://purl.flvc.org/fau/fd/FADT12133
Subject Headings: Physics, Condensed Matter
Format: Document (PDF)

Title: Central Moments of Squeezed States: A Coincidence Statistics Analogue.
Creator: Tison, Christopher C., Miller, Warner A., Alsing, Paul M., Florida Atlantic University, Charles E. Schmidt College of Science, Department of Physics
Abstract/Description: As a subset of quantum optics, single photons are one of the competing physical resources for quantum information processing. When used as carriers of quantum information, they have no equal. For the processing of quantum information, single photons have proven difficult to scale beyond the order of ⇠ 10 photons. The lack of single-photon-level interaction has led to creative approaches which rely on postselection to filter the possible measured outcomes to those which appear as though...
Show moreAs a subset of quantum optics, single photons are one of the competing physical resources for quantum information processing. When used as carriers of quantum information, they have no equal. For the processing of quantum information, single photons have proven difficult to scale beyond the order of ⇠ 10 photons. The lack of single-photon-level interaction has led to creative approaches which rely on postselection to filter the possible measured outcomes to those which appear as though interaction occurred. This approach of post-selection leans heavily on the ability to not only generate but also detect scores of single photons simultaneously and with near perfect efficiency. Our work relaxes the emphasis which has been placed on single photons for quantum information processing to that of states with, in principle, an arbitrary number of photons. Central moment expectations on two-mode squeezed states are shown to exhibit post-selection behavior which reflects the single-photon counterpart. These measures are proven to be robust to loss and return entangled state statistics on average. With naive estimation of the central moment, states with ~ 20 modes are within reach with current technology, closing the gap between quantum states which can and cannot be classically simulated.
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Date Issued: 2018
PURL: http://purl.flvc.org/fau/fd/FA00005951
Subject Headings: Squeezed states (Optics), Quantum optics, Photons, Integrated optics
Format: Document (PDF)

Title: Binary neutron star mergeres: simulations with arbitrarily spinning stars.
Creator: Tsatsin, Petr, Marronetti, Pedro, Charles E. Schmidt College of Science, Department of Physics
Abstract/Description: The starting point of any general relativistic numerical simulation is a solution of the Hamiltonian and momentum constraints that (ideally) represents an astrophysically realistic scenario. This dissertation presents a new method to produce initial data sets for binary neutron stars with arbitrary spins and orbital eccentricities. The method only provides approximate solutions to the constraints. However, it was shown that the corresponding constraint violations subside after a few orbits,...
Show moreThe starting point of any general relativistic numerical simulation is a solution of the Hamiltonian and momentum constraints that (ideally) represents an astrophysically realistic scenario. This dissertation presents a new method to produce initial data sets for binary neutron stars with arbitrary spins and orbital eccentricities. The method only provides approximate solutions to the constraints. However, it was shown that the corresponding constraint violations subside after a few orbits, becoming comparable to those found in evolutions of standard conformally flat, helically symmetric binary initial data. This dissertation presents the first spinning neutron star binary simulations in circular orbits with a orbital eccentricity less then 0.01. The initial data sets corresponding to binaries with spins aligned, zero and anti-aligned with the orbital angular momentum were evolved in time. These simulations show the orbital “hang-up” effect previously seen in binary black holes. Additionally, they show orbital eccentricities that can be up to one order of magnitude smaller than those found in helically symmetric initial sets evolutions.
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Date Issued: 2013
PURL: http://purl.flvc.org/fau/fd/FA0004067
Subject Headings: Astrophysics, Black holes (Astronomy), General relativity (Physics), Gravitational waves, Neutron stars, Particles (Nuclear physics)
Format: Document (PDF)

Title: Hamiltonian Methods in the Quantization of Gauge Systems.
Creator: Vaulin, Ruslan, Florida Atlantic University, Miller, Warner A., Charles E. Schmidt College of Science, Department of Physics
Abstract/Description: The new formalism for quantization of gauge systems based on the concept of the dynamical Hamiltonian recently introduced as a basis for the canonical theory of quantum gravity was considered in the context of general gauge theories. This and other Hamiltonian methods, that include Dirac's theory of extended Hamiltonian and the Hamiltonian reduction formalism were critically examined. It was established that the classical theories of constrained gauge systems formulated within the framework...
Show moreThe new formalism for quantization of gauge systems based on the concept of the dynamical Hamiltonian recently introduced as a basis for the canonical theory of quantum gravity was considered in the context of general gauge theories. This and other Hamiltonian methods, that include Dirac's theory of extended Hamiltonian and the Hamiltonian reduction formalism were critically examined. It was established that the classical theories of constrained gauge systems formulated within the framework of either of the approaches are equivalent. The central to the proof of equivalence was the fact that the gauge symmetries resuIt in the constraints of the first class in Dirac's terminology that Iead to redundancy of equations of motion for some of the canonica variables. Nevertheless, analysis of the quantum theories showed that in general, the quantum theory of the dynamical Hamiltonian is inequivalent to those of the extended Hamiltonian and the Hamiltonian reduction. The new method of quantization was applied to a number of gauge systems, including the theory of relativistic particle, the Bianchi type IX cosmological model and spinor electrodynamics along side with the traditional methods of quantization. In all of the cases considered the quantum theory of the dynamical Hamiltonian was found to be well-defined and to possess the appropriate classical limit. In particular, the quantization procedure for the Bianchi type IX cosmological spacetime did not run into any of the known problems with quantizing the theory of General Relativity. On the other hand, in the case of the quantum electrodynamics the dynamical Hamiltonian approach led to the quantum theory with the modified self-interaction in the matter sector. The possible consequence of this for the quantization of the full theory of General Relativity including the matter fields are discussed.
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Date Issued: 2006
PURL: http://purl.flvc.org/fau/fd/FA00000882
Subject Headings: Quantum field theory, Mathematical physics, Evolution equations, Nonlinear, Hamiltonian systems
Format: Document (PDF)

Title: A characterization of the LAP Aquarius Phantom for external LAP laser alignment and magnetic resonance geometric distortion verification for stereotactic radiation surgery patient simulation.
Creator: Vergara, Daniel, Charles E. Schmidt College of Science, Department of Physics
Abstract/Description: The Thesis explores additional applications of LAP's Aquarius external laser alignment verification Phantom by examining geometric accuracy of magnetic resonance images commonly used for planning intracranial stereotactic radiation surgery (ICSRS) cases. The scans were performed with MRI protocols used for ICSRS, and head and neck diagnosis, and their images fused to computerized tomographic (CT) images. The geometric distortions (GDs) were measured against the CT in all axial, sagittal, and...
Show moreThe Thesis explores additional applications of LAP's Aquarius external laser alignment verification Phantom by examining geometric accuracy of magnetic resonance images commonly used for planning intracranial stereotactic radiation surgery (ICSRS) cases. The scans were performed with MRI protocols used for ICSRS, and head and neck diagnosis, and their images fused to computerized tomographic (CT) images. The geometric distortions (GDs) were measured against the CT in all axial, sagittal, and coronal directions at different levels. Using the Aquarius Phantom, one is able to detect GD in ICSRS planning MRI acquisitions, and align the external LAP patient alignment lasers, by following the LAP QA protocol. GDs up to about 2 mm are observed at the distal regions of the longitudinal axis in the SRS treatment planning MR images. Based on the results, one may recommend the use of the Aquarius Phantom to determine if margins should be included for SRS treatment planning.
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Date Issued: 2012
PURL: http://purl.flvc.org/FAU/3352878
Subject Headings: Radiotherapy, Techniques, Medical physics, Imaging systems in medicine, Tomographic images, Computerized axial tomography
Format: Document (PDF)

Title: LOOP QUANTUM GRAVITY DYNAMICS: MODELS AND APPLICATIONS.
Creator: Vilensky, Ilya, Engle, Jonathan, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Physics
Abstract/Description: In this dissertation we study the dynamics of loop quantum gravity and its applications. We propose a tunneling phenomenon of a black hole-white hole transition and derive an amplitude for such transition using the spinfoam framework. We investigate a special class of kinematical states for loop quantum gravity - Bell spin networks - and show that their entanglement entropy obeys the area law. We develop a new spinfoam vertex amplitude that has the correct semi-classical limit. We then apply...
Show moreIn this dissertation we study the dynamics of loop quantum gravity and its applications. We propose a tunneling phenomenon of a black hole-white hole transition and derive an amplitude for such transition using the spinfoam framework. We investigate a special class of kinematical states for loop quantum gravity - Bell spin networks - and show that their entanglement entropy obeys the area law. We develop a new spinfoam vertex amplitude that has the correct semi-classical limit. We then apply this new amplitude to calculate the graviton propagator and a cosmological transition amplitude. The results of these calculations show feasibility of computations with the new amplitude and its viability as a spinfoam model. Finally, we use physical principles to radically constrain ambiguities in the cosmological dynamics and derive unique Hamiltonian dynamics for Friedmann-Robertson-Walker and Bianchi I cosmologies.
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Date Issued: 2019
PURL: http://purl.flvc.org/fau/fd/FA00013349
Subject Headings: Quantum gravity, Loop quantum gravity, Cosmology, Spinfoam
Format: Document (PDF)

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