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5,392 Matching Results
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Axions in String Theory
In the context of string theory, axions appear to provide the most plausible solution of the strong CP problem. However, as has been known for a long time, in many string-based models, the axion coupling parameter Fa is several orders of magnitude higher than the standard cosmological bounds. We re-examine this problem in a variety of models, showing that Fa is close to the GUT scale or above in many models that have GUT-like phenomenology, as well as some that do not. On the other hand, in some models with Standard Model gauge fields supported on vanishing cycles, it is possible for Fa to be well below the GUT scale.
Date:
June 9, 2006
Creator:
Svrcek, Peter; /Stanford U., Phys. Dept. /SLAC; Witten, Edward & /Princeton, Inst. Advanced Study
Object Type:
Report
System:
The UNT Digital Library
Advanced accelerator theory development
A new accelerator technology, the dielectric wall accelerator (DWA), is potentially an ultra compact accelerator/pulsed power driver. This new accelerator relies on three new components: the ultra-high gradient insulator, the asymmetric Blumlein and low jitter switches. In this report, we focused our attention on the first two components of the DWA system the insulators and the asymmetric Blumlein. First, we sought to develop the necessary design tools to model and scale the behavior of the high gradient insulator. To perform this task we concentrated on modeling the discharge processes (i.e., initiation and creation of the surface discharge). In addition, because these high gradient structures exhibit favorable microwave properties in certain accelerator configurations, we performed experiments and calculations to determine the relevant electromagnetic properties. Second, we performed circuit modeling to understand energy coupling to dynamic loads by the asymmetric Blumlein. Further, we have experimentally observed a non-linear coupling effect in certain asymmetric Blumlein configurations. That is, as these structures are stacked into a complete module, the output voltage does not sum linearly and a lower than expected output voltage results. Although we solved this effect experimentally, we performed calculations to understand this effect more fully to allow better optimization of this …
Date:
February 9, 1998
Creator:
Sampayan, S.E.; Houck, T.L.; Poole, B.; Tishchenko, N.; Vitello, P.A. & Wang, I.
Object Type:
Report
System:
The UNT Digital Library
Continuum Edge Gyrokinetic Theory and Simulations
The following results are presented from the development and application of TEMPEST, a fully nonlinear (full-f) five dimensional (3d2v) gyrokinetic continuum edge-plasma code. (1) As a test of the interaction of collisions and parallel streaming, TEMPEST is compared with published analytic and numerical results for endloss of particles confined by combined electrostatic and magnetic wells. Good agreement is found over a wide range of collisionality, confining potential, and mirror ratio; and the required velocity space resolution is modest. (2) In a large-aspect-ratio circular geometry, excellent agreement is found for a neoclassical equilibrium with parallel ion flow in the banana regime with zero temperature gradient and radial electric field. (3) The four-dimensional (2d2v) version of the code produces the first self-consistent simulation results of collisionless damping of geodesic acoustic modes and zonal flow (Rosenbluth-Hinton residual) with Boltzmann electrons using a full-f code. The electric field is also found to agree with the standard neoclassical expression for steep density and ion temperature gradients in the banana regime. In divertor geometry, it is found that the endloss of particles and energy induces parallel flow stronger than the core neoclassical predictions in the SOL. (5) Our 5D gyrokinetic formulation yields a set of nonlinear …
Date:
January 9, 2007
Creator:
Xu, X. Q.; Xiong, Z.; Dorr, M. R.; Hittinger, J. A.; Bodi, K.; Candy, J. et al.
Object Type:
Article
System:
The UNT Digital Library
Theory and Fluid Simulations of Boundary Plasma Fluctuations
Theoretical and computational investigations are presented of boundary plasma microturbulence that take into account important effects of the geometry of diverted tokamaks--in particular, the effect of x-point magnetic shear and the termination of field lines on divertor plates. We first generalize our previous 'heuristic boundary condition' which describes, in a lumped model, the closure of currents in the vicinity of the x-point region to encompass three current-closure mechanisms. We then use this boundary condition to derive the dispersion relation for low-beta flute-like modes in the divertor-leg region under the combined drives of curvature, sheath impedance, and divertor tilt effects. The results indicate the possibility of strongly growing instabilities, driven by sheath boundary conditions, and localized in either the private or common flux region of the divertor leg depending on the radial tilt of divertor plates. We re-visit the issue of x-point effects on blobs, examining the transition from blobs terminated by x-point shear to blobs that extend over both the main SOL and divertor legs. We find that, for a main-SOL blob, this transition occurs without a free-acceleration period as previously thought, with x-point termination conditions applying until the blob has expanded to reach the divertor plate. We also derive …
Date:
January 9, 2007
Creator:
Cohen, R. H.; LaBombard, B.; LoDestro, L. L.; Rognlien, T. D.; Ryutov, D. D.; Terry, J. L. et al.
Object Type:
Article
System:
The UNT Digital Library
Theory and Simulation of the Physics of Space Charge Dominated Beams
This report describes modeling of intense electron and ion beams in the space charge dominated regime. Space charge collective modes play an important role in the transport of intense beams over long distances. These modes were first observed in particle-in-cell simulations. The work presented here is closely tied to the University of Maryland Electron Ring (UMER) experiment and has application to accelerators for heavy ion beam fusion.
Date:
December 9, 2002
Creator:
Haber, Irving
Object Type:
Report
System:
The UNT Digital Library
How Religion Frames Health Norms: A Structural Theory Approach
This review looks at the religious communities influence health-related behaviors of adherents in important ways for public health promotion. Questions remain about the processes involved and resultant health promotion actions of the religious adherents.
Date:
April 9, 2018
Creator:
Mpofu, Elias
Object Type:
Article
System:
The UNT Digital Library
Overview of Theory and Simulations in the Heavy Ion Fusion ScienceVirtual National Laboratory
The Heavy Ion Fusion Science Virtual National Laboratory (HIFS-VNL) is a collaboration of Lawrence Berkeley National Laboratory, Lawrence Livermore National Laboratory, and Princeton Plasma Physics Laboratory. These laboratories, in cooperation with researchers at other institutions, are carrying out a coordinated effort to apply intense ion beams as drivers for studies of the physics of matter at extreme conditions, and ultimately for inertial fusion energy. Progress on this endeavor depends upon coordinated application of experiments, theory, and simulations. This paper describes the state of the art, with an emphasis on the coordination of modeling and experiment; developments in the simulation tools, and in the methods that underly them, are also treated.
Date:
July 9, 2006
Creator:
Friedman, Alex
Object Type:
Article
System:
The UNT Digital Library
Final Report for Project ``Theory of ultra-relativistic heavy-ion collisions''
In the course of this project the Ohio State University group led by the PI, Professor Ulrich Heinz, developed a comprehensive theoretical picture of the dynamical evolution of ultra-relativistic heavy-ion collisions and of the numerous experimental observables that can be used to diagnose the evolving and short-lived hot and dense fireball created in such collisions. Starting from a qualitative understanding of the main features based on earlier research during the last decade of the twentieth century on collisions at lower energies, the group exploited newly developed theoretical tools and the stream of new high-quality data from the Relativistic Heavy Ion Collider at Brookhaven National Laboratory (which started operations in the summer of the year 2000) to arrive at an increasingly quantitative description of the experimentally observed phenomena. Work done at Ohio State University (OSU) was instrumental in the discovery during the years 2001-2003 that quark-gluon plasma (QGP) created in nuclear collisions at RHIC behaves like an almost perfect liquid with minimal viscosity. The tool of relativistic fluid dynamics for viscous liquids developed at OSU in the years 2005-2007 opened the possibility to quantitatively determine the value of the QGP viscosity empirically from experimental measurements of the collective flow patterns established …
Date:
November 9, 2012
Creator:
Heinz, Ulrich W.
Object Type:
Report
System:
The UNT Digital Library
Nonequilibrium Gyrokinetic Fluctuation Theory and Sampling Noise in Gyrokinetic Particle-in-cell Simulations
The present state of the theory of fluctuations in gyrokinetic GK plasmas and especially its application to sampling noise in GK particle-in-cell PIC simulations is reviewed. Topics addressed include the Δf method, the fluctuation-dissipation theorem for both classical and GK many-body plasmas, the Klimontovich formalism, sampling noise in PIC simulations, statistical closure for partial differential equations, the theoretical foundations of spectral balance in the presence of arbitrary noise sources, and the derivation of Kadomtsev-type equations from the general formalism.
Date:
October 9, 2007
Creator:
Krommes, John A.
Object Type:
Report
System:
The UNT Digital Library
The 4He Total Photo-Absorption Cross Section With Two- Plus Three-Nucleon Interactions From Chiral Effective Field Theory
The total photo-absorption cross section of {sup 4}He is evaluated microscopically using two- (NN) and three-nucleon (NNN) interactions based upon chiral effective field theory ({chi}EFT). The calculation is performed using the Lorentz integral transform method along with the ab initio no-core shell model approach. An important feature of the present study is the consistency of the NN and NNN interactions and also, through the Siegert theorem, of the two- and three-body current operators. This is due to the application of the {chi}EFT framework. The inclusion of the NNN interaction produces a suppression of the peak height and enhancement of the tail of the cross section. We compare to calculations obtained using other interactions and to representative experiments. The rather confused experimental situation in the giant resonance region prevents discrimination among different interaction models.
Date:
March 9, 2007
Creator:
Quaglioni, S & Navratil, P
Object Type:
Article
System:
The UNT Digital Library
Exploring the Relationship Between the Motivation and Behavioral Predisposition of Self-Disclosure on Social Media Applications
This paper examines social media users' self-disclosure.
Date:
November 9, 2018
Creator:
Lee, Kijung & Song, Il-Yeol
Object Type:
Paper
System:
The UNT Digital Library
The Faculty It Liaison Program: Using Participatory Design to Build Possibilities With Technology
This paper proposes a workshop describing a faculty IT liaison program that uses the Bonded Design methodology to encourage interaction and communication between faculty members and information technology professionals.
Date:
November 9, 2018
Creator:
Nesset, Valerie & Bible, J. Brice
Object Type:
Paper
System:
The UNT Digital Library
Arts and Humanities Academics Information Needs in Digital Era
This paper examines arts and humanities academics' scholarly information needs and their means of accessing scholarly e-content in today digital environment.
Date:
November 9, 2018
Creator:
Arshad, Alia & Ameen, Kanwal
Object Type:
Paper
System:
The UNT Digital Library
Bridging, Bonding, and Maintained Social Capital as Predictors of Psychological Well-Being in a WhatsApp Group
This paper reports findings from a study to understand how participants build and maintain social capital through group communication on WhatsApp.
Date:
November 9, 2018
Creator:
Samuel, Noah Oluwafemi
Object Type:
Paper
System:
The UNT Digital Library
Knowledge Management Initiatives Applied to Social Innovation
This paper aims to analyze knowledge management initiatives used in Social Innovation.
Date:
November 9, 2018
Creator:
Zandavali, Carla; Dominik Dos Santos Figueiredo, Yohani; Aparecida Dandolini, Gertrudes & Artur de Souza, Joaoã
Object Type:
Paper
System:
The UNT Digital Library
Heavy-Quarkonium Production in High Energy Proton-Proton Collisions at RHIC
We update the study of the total {psi} and {Upsilon} production cross section in proton-proton collisions at RHIC energies using the QCD-based Color-Singlet (CS) Model, including next-to-leading order partonic matrix elements. We also include charm-quark initiated processes which appear at leading order in {alpha}{sub s}, but which have so far been overlooked in such studies. Contrary to earlier claims, we show that the CS yield is consistent with measurements over a broad range of J/{psi} rapidities. We also find that charm-quark initiated processes, including both intrinsic and sea-like charm components, typically contribute at least 20 % of the direct J/{psi} yield, improving the agreement with data both for the integrated cross section and its rapidity dependence. The key signature for such processes is the observation of a charm-quark jet opposite in azimuthal angle {phi} to the detected J/{psi}. Our results have impact on the proper interpretation of heavy-quarkonium production in heavy-ion collisions and its use as a probe for the quark-gluon plasma.
Date:
December 9, 2009
Creator:
Brodsky, Stanley J. & Lansberg, Jean-Philippe
Object Type:
Article
System:
The UNT Digital Library
Tests of quantum mechanics at a {phi}-factory
Unique tests of quantum mechanics, which can only be performed at a 0-factory, are proposed for Da0ne. Each of these tests consists of measuring the difference between the predicted and the actual amount of interference between two processes leading from a single pure initial state to a single pure final state of a kaon system. Estimates are made of the upper limits that will be set for the amount of violation if the predictions of quantum mechanics turn out to be correct. They are of the order a fraction of one percent. For the case where, on the contrary, a significant violation is found, several decoherence mechanisms are considered.
Date:
August 9, 1994
Creator:
Eberhard, P.H.
Object Type:
Report
System:
The UNT Digital Library
www.fermiqcd.net
FermiQCD is a C++ library for fast development of parallel lattice QCD applications. The expression FermiQCD Collaboration is used as a collective name to indicate both the users of the software and its contributors. One of the main differences between FermiQCD and libraries developed by other collaborations is that it follows an object oriented design as opposed to a procedural design. FermiQCD should not be identified exclusively with the implementation of the algorithms but, rather, with the strict specifications that define its Application Program Interface. One should think of FermiQCD as a language on its own (a superset of the C++ language), designed to describe Lattice QCD algorithms. The objects of the language include complex numbers (mdp-complex), matrices (mdp-matrix), lattices (mdp-lattice), fields (gauge-field, fermi-field, staggered-field), propagators (fermi-propagator) and actions. Algorithms written in terms of these objects are automatically parallel.
Date:
March 9, 2004
Creator:
al., Massino Di Pierro et
Object Type:
Article
System:
The UNT Digital Library
Nuclear physics research operation: Monthly report, August 1958
This report details activities of the Nuclear Physics Research Operation for the month of August 1958.
Date:
September 9, 1958
Creator:
Faulkner, J. E.
Object Type:
Report
System:
The UNT Digital Library
Science and art in heavy-ion collisions
One of the more intriguing phenomena discovered in heavy-ion physics is the seeming appearance of high energy structure in the excitation spectra of inelastically scattered heavy ions. For reasons illustrated, these may well be a phenomena unique to heavy ions and their explanation perhaps unique to TDHF.
Date:
August 9, 1982
Creator:
Weiss, M.S.
Object Type:
Article
System:
The UNT Digital Library
Modular invariant gaugino condensation
The construction of effective supergravity lagrangians for gaugino condensation is reviewed and recent results are presented that are consistent with modular invariance and yield a positive definite potential of the noscale type. Possible implications for phenomenology are briefly discussed. 29 refs.
Date:
May 9, 1991
Creator:
Gaillard, M. K.
Object Type:
Article
System:
The UNT Digital Library
Pacific Northwest GridWise™ Testbed Demonstration Projects; Part I. Olympic Peninsula Project
This report describes the implementation and results of a field demonstration wherein residential electric water heaters and thermostats, commercial building space conditioning, municipal water pump loads, and several distributed generators were coordinated to manage constrained feeder electrical distribution through the two-way communication of load status and electric price signals. The field demonstration took place in Washington and Oregon and was paid for by the U.S. Department of Energy and several northwest utilities. Price is found to be an effective control signal for managing transmission or distribution congestion. Real-time signals at 5-minute intervals are shown to shift controlled load in time. The behaviors of customers and their responses under fixed, time-of-use, and real-time price contracts are compared. Peak loads are effectively reduced on the experimental feeder. A novel application of portfolio theory is applied to the selection of an optimal mix of customer contract types.
Date:
January 9, 2008
Creator:
Hammerstrom, Donald J.; Ambrosio, Ron; Carlon, Teresa A.; DeSteese, John G.; Horst, Gale R.; Kajfasz, Robert et al.
Object Type:
Report
System:
The UNT Digital Library
America 2000 and Special Education: Can the Two Be Merged?
This paper uses systems theory and force field analysis to evaluate the potential for combining special education with America 2000 national educational strategy and goals.
Date:
April 9, 1993
Creator:
Pazey, Barbara L.
Object Type:
Paper
System:
The UNT Digital Library
Running Head: Faithful Health Norms
This article applies a structural theory analysis to understand the ways by which religious adherents adopt and enact health norms.
Date:
January 18, 2018
Creator:
Mpofu, Elias
Object Type:
Article
System:
The UNT Digital Library