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Topological Landscapes: A Terrain Metaphor for ScientificData

Description: Scientific visualization and illustration tools are designed to help people understand the structure and complexity of scientific data with images that are as informative and intuitive as possible. In this context, the use of metaphors plays an important role, since they make complex information easily accessible by using commonly known concepts. In this paper we propose a new metaphor, called 'Topological Landscapes', which facilitates understanding the topological structure of scalar functions. The basic idea is to construct a terrain with the same topology as a given dataset and to display the terrain as an easily understood representation of the actual input data. In this projection from an n-dimensional scalar function to a two-dimensional (2D) model we preserve function values of critical points, the persistence (function span) of topological features, and one possible additional metric property (in our examples volume). By displaying this topologically equivalent landscape together with the original data we harness the natural human proficiency in understanding terrain topography and make complex topological information easily accessible.
Date: August 1, 2007
Creator: Weber, Gunther H.; Bremer, Peer-Timo & Pascucci, Valerio
Partner: UNT Libraries Government Documents Department

Probing Late Neutrino Mass Properties With SupernovaNeutrinos

Description: Models of late-time neutrino mass generation contain new interactions of the cosmic background neutrinos with supernova relic neutrinos (SRNs). Exchange of an on-shell light scalar may lead to significant modification of the differential SRN flux observed at earth. We consider an Abelian U(1) model for generating neutrino masses at low scales, and show that there are cases for which the changes induced in the flux allow one to distinguish the Majorana or Dirac nature of neutrinos, as well as the type of neutrino mass hierarchy (normal or inverted or quasi-degenerate). In some region of parameter space the determination of the absolute values of the neutrino masses is also conceivable. Measurements of the presence of these effects may be possible at the next-generation water Cerenkov detectors enriched with Gadolinium, or a 100 kton liquid argon detector.
Date: August 8, 2007
Creator: Baker, Joseph; Goldberg, Haim; Perez, Gilad & Sarcevic, Ina
Partner: UNT Libraries Government Documents Department

Constraints and Casimirs for Super Poincare and Supertranslation Algebras in various dimensions

Description: We describe, for arbitrary dimensions the construction of a covariant and supersymmetric constraint for the massless Super Poincare algebra and we show that the constraint fixes uniquely the representation of the algebra. For the case of finite mass and in the absence of central charges we discuss a similar construction, which generalizes to arbitrary dimensions the concept of the superspin Casimir. Finally we discuss briefly the modifications introduced by central charges, both scalar and tensorial.
Date: November 3, 2004
Creator: Zumino, Bruno
Partner: UNT Libraries Government Documents Department

3-D full waveform inversion of seismic data; Part I. Theory

Description: Full waveform inversion of seismic data is a challenging subject partly because of the lack of precise knowledge of the source. Since currently available approaches involve some form of approximations to the source, inversion results are subject to the quality and the choice of the source information used. A new full waveform inversion scheme has been introduced (Lee and Kim, 2003) using normalized wavefield for simple two-dimensional (2-D) scalar problems. The method does not require source information, so potential inversion errors due to source estimation may be eliminated. A gather of seismic traces is first Fourier-transformed into the frequency domain and a normalized wavefield is obtained for each trace in the frequency domain. Normalization is done with respect to the frequency response of a reference trace selected from the gather, so the complex-valued normalized wavefield is source-independent and dimensionless. The inversion algorithm minimizes misfits between measured normalized wavefield and numerically computed normalized wavefield. In this paper the full waveform inversion is extended to three-dimensional (3-D) problems.
Date: May 12, 2003
Creator: Lee, Ki Ha
Partner: UNT Libraries Government Documents Department

Source-independent full waveform inversion of seismic data

Description: A rigorous full waveform inversion of seismic data has been a challenging subject partly because of the lack of precise knowledge of the source. Since currently available approaches involve some form of approximations to the source, inversion results are subject to the quality and the choice of the source information used. We propose a new full waveform inversion methodology that does not involve source spectrum information. Thus potential inversion errors due to source estimation can be eliminated. A gather of seismic traces is first Fourier-transformed into the frequency domain and a normalized wavefield is obtained for each trace in the frequency domain. Normalization is done with respect to the frequency response of a reference trace selected from the gather, so the complex-valued normalized wavefield is dimensionless. The source spectrum is eliminated during the normalization procedure. With its source spectrum eliminated, the normalized wavefield allows us construction of an inversion algorithm without the source information. The inversion algorithm minimizes misfits between measured normalized wavefield and numerically computed normalized wavefield. The proposed approach has been successfully demonstrated using a simple two-dimensional scalar problem.
Date: March 20, 2002
Creator: Lee, Ki Ha & Kim, Hee Joon
Partner: UNT Libraries Government Documents Department

A General Method for Calculating the External Magnetic Field from a Cylindrical Magnetic Source using Toroidal Functions

Description: An alternative method is developed to compute the magnetic field from a circular cylindrical magnetic source. Specifically, a Fourier series expansion whose coefficients are toroidal functions is introduced which yields an alternative to the more familiar spherical harmonic solution or the Elliptic integral solution. This alternate formulation coupled with a method called charge simulation allows one to compute the external magnetic field from an arbitrary magnetic source in terms of a toroidal expansion. This expansion is valid on any finite hypothetical external observation cylinder. In other words, the magnetic scalar potential or the magnetic field intensity is computed on a exterior cylinder which encloses the magnetic source. This method can be used to accurately compute the far field where a finite element formulation is known to be inaccurate.
Date: February 14, 2006
Creator: Selvaggi, J; Salon, S & Chari, O Kwon CVK
Partner: UNT Libraries Government Documents Department

From shock response spectrum to temporal moments and vice-versa

Description: Temporal momerils have been used in engineering mechanics to condense the information contained in the shock response spectrum into a few scalar quantities. This paper presents an application of temporal moments to the propagation of an explosive-driven shock wave through an assembly of metallic parts. For this particular application, it is shown that temporal moments characterize the response of the system better than other features traditionally used in the analysis of nonlinear, transient events, such as the peak response or 10% duration of event. The inverse problem is also illustrated: the original, time-domain signals and their shock response spectra can be reconstructed from the temporal moments. This property makes temporal moments features of choice for the analysis of experimental data or the development of numerical models because they are low-dimensional quantities; they capture transient dynamics well; and they can be used to re-generate the original time signals.
Date: January 1, 2002
Creator: Hemez, F. M. (Fran├žois M.) & Doebling, S. W. (Scott W.)
Partner: UNT Libraries Government Documents Department

Adventures in Coulomb Gauge

Description: We study the phase structure of SU(2) gauge theories at zero and high temperature, with and without scalar matter fields, in terms of the symmetric/broken realization of the remnant gauge symmetry which exists after fixing to Coulomb gauge. The symmetric realization is associated with a linearly rising color Coulomb potential (which we compute numerically), and is a necessary but not sufficient condition for confinement.
Date: September 26, 2003
Creator: Greensite, J. & Olejnik, S.
Partner: UNT Libraries Government Documents Department

A generalized vector-valued total variation algorithm

Description: We propose a simple but flexible method for solving the generalized vector-valued TV (VTV) functional, which includes both the {ell}{sup 2}-VTV and {ell}{sup 1}-VTV regularizations as special cases, to address the problems of deconvolution and denoising of vector-valued (e.g. color) images with Gaussian or salt-andpepper noise. This algorithm is the vectorial extension of the Iteratively Reweighted Norm (IRN) algorithm [I] originally developed for scalar (grayscale) images. This method offers competitive computational performance for denoising and deconvolving vector-valued images corrupted with Gaussian ({ell}{sup 2}-VTV case) and salt-and-pepper noise ({ell}{sup 1}-VTV case).
Date: January 1, 2009
Creator: Wohlberg, Brendt & Rodriguez, Paul
Partner: UNT Libraries Government Documents Department

Evidence for light scalar resonances in charm meson decays from Fermilab E791

Description: From Dalitz-plot analyses of D{sup +} {yields} {pi}{sup -}{pi}{sup +}{pi}{sup +} and D{sup +} {yields} K{sup -}{pi}{sup +}{pi}{sup +} decays, we find evidence for light and broad scalar resonances {sigma}(500) and {kappa}(800). From a Dalitz-plot analysis of D{sub s}{sup +} {yields} {pi}{sup -}{pi}{sup +}{pi}{sup +} decays, they measure the masses and decay widths of the scalar resonances f{sub 0}(980) and f{sub 0}(1370).
Date: January 24, 2003
Creator: Schwartz, Alan J.
Partner: UNT Libraries Government Documents Department

The stability of the scalar {chi}{sup 2}{phi} interaction

Description: A scalar field theory with a {chi}{dagger}{chi}{phi} interaction is known to be unstable. Yet it has been used frequently without any sign of instability in standard text book examples and research articles. In order to reconcile these seemingly conflicting results, we show that the theory is stable if the Fock space of all intermediate states is limited to a finite number of {chi}{bar {chi}} loops associated with field {chi} that appears quadradically in the interaction, and that instability arises only when intermediate states include these loops to all orders.
Date: February 16, 2001
Creator: Gross, Franz; Savkli, Cetin & Tjon, John
Partner: UNT Libraries Government Documents Department

The scalar glueball mass in Regge phenomenology

Description: The author shows that linear Regge trajectories for mesons and glueballs, and the cubic mass spectrum associated with them, determine a relation between the masses of the {rho} meson and the scalar glueball, M(0{sup ++}) = 3/{radical}2 M({rho}), which implies M(0{sup ++}) = 1620 {+-} 10 MeV. He also discusses a relation between the masses of the scalar and tensor glueballs, M(2{sup ++}) = {radical}2 M(0{sup ++}), which implies M(2{sup ++}) = 2290 {+-} 15 MeV.
Date: December 1, 1998
Creator: Burakovsky, L.
Partner: UNT Libraries Government Documents Department

A texture-based frameowrk for improving CFD data visualization in a virtual environment

Description: In the field of computational fluid dynamics (CFD) accurate representations of fluid phenomena can be simulated but require large amounts of data to represent the flow domain. Most datasets generated from a CFD simulation can be coarse, {approx} 10,000 nodes or cells, or very fine with node counts on the order of 1,000,000. A typical dataset solution can also contain multiple solutions for each node, pertaining to various properties of the flow at a particular node. Scalar properties such as density, temperature, pressure, and velocity magnitude are properties that are typically calculated and stored in a dataset solution. Solutions are not limited to just scalar properties. Vector quantities, such as velocity, are also often calculated and stored for a CFD simulation. Accessing all of this data efficiently during runtime is a key problem for visualization in an interactive application. Understanding simulation solutions requires a post-processing tool to convert the data into something more meaningful. Ideally, the application would present an interactive visual representation of the numerical data for any dataset that was simulated while maintaining the accuracy of the calculated solution. Most CFD applications currently sacrifice interactivity for accuracy, yielding highly detailed flow descriptions but limiting interaction for investigating the field.
Date: May 1, 2005
Creator: Biveins, Gerrick O'Ron
Partner: UNT Libraries Government Documents Department

Negative contributions to S in an effective field theory

Description: We show that an effective field theory that includes non-standard couplings between the electroweak gauge bosons and the top and bottom quarks may yield negative contributions to both the S and T oblique radiative electroweak parameters. We find that such an effective field theory provides a better fit to data than the standard model (the {chi}{sup 2} per degree of freedom is half as large). We examine in some detail an illustrative model where the exchange of heavy scalars produces the correct type of non-standard couplings.
Date: September 19, 1997
Creator: Dobrescu, Bogdan A. & Terning, John
Partner: UNT Libraries Government Documents Department

A strategy for a realization of a problem free Einstein - Hilbert action along with a problem free toy cosmology

Description: We describe features of a low energy effective Scalar-Tensor theory of gravity having a divergent non-minimal coupling at a point where a fermionic part of the action identically vanishes and is therefore non-dynamical. Under fairly general conditions, theories having a divergent non-minimal coupling at a point can support non-topological soliton solutions. The interior of all sufficiently large solitonic domains approach a unique limit point determined by the vanishing of the effective potential of the non-minimally coupled scalar field. This can lead to a realization of an effective Einstein-Hilbert action with no cosmological constant problem. A cosmology with characteristic features follows.
Date: July 12, 1999
Creator: Sethi, Daksh Lohiya and Meetu
Partner: UNT Libraries Government Documents Department

A texture-based framework for improving CFD data visualization in a virtual environment

Description: In the field of computational fluid dynamics (CFD) accurate representations of fluid phenomena can be simulated hut require large amounts of data to represent the flow domain. Most datasets generated from a CFD simulation can be coarse, {approx}10,000 nodes or cells, or very fine with node counts on the order of 1,000,000. A typical dataset solution can also contain multiple solutions for each node, pertaining to various properties of the flow at a particular node. Scalar properties such as density, temperature, pressure, and velocity magnitude are properties that are typically calculated and stored in a dataset solution. Solutions are not limited to just scalar properties. Vector quantities, such as velocity, are also often calculated and stored for a CFD simulation. Accessing all of this data efficiently during runtime is a key problem for visualization in an interactive application. Understanding simulation solutions requires a post-processing tool to convert the data into something more meaningful. Ideally, the application would present an interactive visual representation of the numerical data for any dataset that was simulated while maintaining the accuracy of the calculated solution. Most CFD applications currently sacrifice interactivity for accuracy, yielding highly detailed flow descriptions hut limiting interaction for investigating the field.
Date: May 5, 2005
Creator: Bivins, Gerrick O'Ron
Partner: UNT Libraries Government Documents Department

Evaluation of leading scalar and vector architectures for scientific computations

Description: The growing gap between sustained and peak performance for scientific applications is a well-known problem in high performance computing. The recent development of parallel vector systems offers the potential to reduce this gap for many computational science codes and deliver a substantial increase in computing capabilities. This project examines the performance of the cacheless vector Earth Simulator (ES) and compares it to superscalar cache-based IBM Power3 system. Results demonstrate that the ES is significantly faster than the Power3 architecture, highlighting the tremendous potential advantage of the ES for numerical simulation. However, vectorization of a particle-in-cell application (GTC) greatly increased the memory footprint preventing loop-level parallelism and limiting scalability potential.
Date: April 20, 2004
Creator: Simon, Horst D.; Oliker, Leonid; Canning, Andrew; Carter, Jonathan; Ethier, Stephane & Shalf, John
Partner: UNT Libraries Government Documents Department

On Quadratic Divergences in Supergravity, Vacuum Energy and theSupersymmetric Flavor Problem

Description: We examine the phenomenological consequences ofquadratically divergent contributions to the scalar potential insupergravity effective Lagrangians. We focus specifically on the effectof these corrections on the vacuum configurationof scalar fields insoftly-broken supersymmetric theory is and the role these correctionsplay in generating non-diagonal soft scalar masses. Both effects can onlybe properly studied when the divergences are regulated in a manifestlysupersymmetric manner -- something which has ths far been neglected inpast treatments. We show how a supersymmetric regularization can impactpast conclusions about both types of phenomena and discuss what types ofhigh-energy theories are likely to be safe from unwanted flavor-changingneutral current interactions in the context of supergravity theoriesderived from heterotic string compactifications.
Date: November 18, 2005
Creator: Gaillard, Mary K. & Nelson, Brent D.
Partner: UNT Libraries Government Documents Department

Visualization of Scalar Adaptive Mesh Refinement Data

Description: Adaptive Mesh Refinement (AMR) is a highly effective computation method for simulations that span a large range of spatiotemporal scales, such as astrophysical simulations, which must accommodate ranges from interstellar to sub-planetary. Most mainstream visualization tools still lack support for AMR grids as a first class data type and AMR code teams use custom built applications for AMR visualization. The Department of Energy's (DOE's) Science Discovery through Advanced Computing (SciDAC) Visualization and Analytics Center for Enabling Technologies (VACET) is currently working on extending VisIt, which is an open source visualization tool that accommodates AMR as a first-class data type. These efforts will bridge the gap between general-purpose visualization applications and highly specialized AMR visual analysis applications. Here, we give an overview of the state of the art in AMR scalar data visualization research.
Date: December 6, 2007
Creator: VACET; Weber, Gunther; Weber, Gunther H.; Beckner, Vince E.; Childs, Hank; Ligocki, Terry J. et al.
Partner: UNT Libraries Government Documents Department

Search for Beyond the Standard Model Physics at D0

Description: The standard model (SM) of particle physics has been remarkably successful at predicting the outcomes of particle physics experiments, but there are reasons to expect new physics at the electroweak scale. Over the last several years, there have been a number of searches for beyond the standard model (BSM) physics at D0. Here, we limit our focus to three: searches for diphoton events with large missing transverse energy (E{sub T}), searches for leptonic jets and E{sub T}, and searches for single vector-like quarks. We have discussed three recent searches at D0. There are many more, including limits on heavy neutral gauge boson in the ee channel, a search for scalar top quarks, a search for quirks, and limits on a new resonance decaying to WW or WZ.
Date: August 1, 2011
Creator: Kraus, James
Partner: UNT Libraries Government Documents Department

QUARKONIUM CORRELATORS AT FINITE TEMPERATURE AND POTENTIAL MODELS.

Description: We discuss the calculations of quarkonium spectral functions in potential models and their implications for the interpretation of the lattice data on quarkonium correlators. In particular, we find that melting of different quarkonium states does not lead to significant change in the Euclidean time correlators. The large change of the quarkonium correlators above deconfinement observed in the scalar and axial-vector channels appears to be due to the zero mode contribution.
Date: July 30, 2007
Creator: MOCSY,A. & PETRECZKY, P.
Partner: UNT Libraries Government Documents Department

Natural Little Hierarchy from Partially Goldstone Twin Higgs

Description: We construct a simple theory in which the fine-tuning of the standard model is significantly reduced. Radiative corrections to the quadratic part of the scalar potential are constrained to be symmetric under a global U(4) x U(4){prime} symmetry due to a discrete Z{sub 2} 'twin' parity, while the quartic part does not possess this symmetry. As a consequence, when the global symmetry is broken the Higgs fields emerge as light pseudo-Goldstone bosons, but with sizable quartic self-interactions. This structure allows the cutoff scale, {Lambda}, to be raised to the multi-TeV region without significant fine-tuning. In the minimal version of the theory, the amount of fine-tuning is about 15% for {Lambda} = 5 TeV, while it is about 30% in an extended model. This provides a solution to the little hierarchy problem. In the minimal model, the 'visible' particle content is exactly that of the two Higgs doublet standard model, while the extended model also contains extra vector-like fermions with masses {approx} (1 {approx} 2) TeV. At the LHC, our minimal model may appear exactly as the two Higgs doublet standard model, and new physics responsible for cutting off the divergences of the Higgs mass-squared parameter may not be discovered. Several possible processes that may be used to discriminate our model from the simple two Higgs doublet model are discussed for the LHC and for a linear collider.
Date: October 20, 2005
Creator: Chacko, Z.; Nomura, Yasunori; Papucci, Michele & Perez, Gilad
Partner: UNT Libraries Government Documents Department

Hunting the Scalar Glueball: Prospects for BES III

Description: The search for the ground state scalar glueball $G_0$ isreviewed. Spin zero glueballs will have unique dynamical properties ifthe $<G_0|\overline qq>$ amplitude is suppressed by chiralsymmetry, as it is to all orders in perturbation theory: for instance,mixing of $G_0$ with $\overline qq$ mesons would be suppressed, radiative$\jp$ decay would be a filter for new physics in the spin zero channel,and the decay $G_0 \rightarrow \overline KK$ could be enhanced relativeto $G_0 \rightarrow \pi \pi$. These properties are consistent with theidentification of $f_0(1710)$ as the largely unmixed ground state scalarglueball, while recent BES data implies that $f_0(1500)$ does not containthe dominant glueball admixture. Three hypotheses are discussed: that$G_0$ is 1) predominantly $f_0(1500)$ or 2) predominantly $f_0(1710)$ or3) is strongly mixed between $f_0(1500)$ and $f_0(1710)$.
Date: September 18, 2006
Creator: Chanowitz, Michael S.
Partner: UNT Libraries Government Documents Department

Computing the External Magnetic Scalar Potential due to an Unbalanced Six-Pole Permanent Magnet Motor

Description: The accurate computation of the external magnetic field from a permanent magnet motor is accomplished by first computing its magnetic scalar potential. In order to find a solution which is valid for any arbitrary point external to the motor, a number of proven methods have been employed. Firstly, A finite element model is developed which helps generate magnetic scalar potential values valid for points close to and outside the motor. Secondly, charge simulation is employed which generates an equivalent magnetic charge matrix. Finally, an equivalent multipole expansion is developed through the application of a toroidal harmonic expansion. This expansion yields the harmonic components of the external magnetic scalar potential which can be used to compute the magnetic field at any point outside the motor.
Date: February 12, 2007
Creator: Selvaggi, J.; Salon, S.; Kwon, O. & Chari, M. V. K.
Partner: UNT Libraries Government Documents Department