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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Transverse Momentum Distributions from Lattice QCD without Wilson Lines

The transverse-momentum-dependent distributions (TMDs), which are defined by gauge-invariant 3D parton correlators with staple-shaped lightlike Wilson lines, can be calculated from quark and gluon correlators fixed in the Coulomb gauge on a Euclidean lattice. These quantities can be expressed gauge invariantly as the correlators of Coulomb-gauge-dressed fields, which reduce to the standard TMD correlators under principal-value prescription in the infinite boost limit. In the framework of large-momentum effective theory, a quasi-TMD defined from such correlators in a large-momentum hadron state can be matched to the TMD via a factorization formula, whose exact form is derived using soft collinear effective theory and verified at one-loop order. Compared to the currently used gauge-invariant correlators, this new method can substantially improve statistical precision and simplify renormalization for the time-reversal-even TMDs, which will greatly enhance the predicative power of lattice QCD in the nonperturbative region.

Effective field theory↗
DOE OSTI2025

Chiral rank-$k$ truncations for the multigrid preconditioner of Wilson fermions in lattice QCD

We present a modification to the setup algorithm for the multigrid preconditioner of Wilson fermions in lattice QCD. A larger number of test vectors than that used in conventional multigrid is generated by the smoother. This set of test vectors is then truncated by a singular value decomposition on the chiral components of the test vectors, which are subsequently used to form the prolongation and restriction matrices of the multigrid hierarchy. This modification is demonstrated to improve the convergence of linear equations on an anisotropic lattice with 𝑚𝜋 ≈ 280 MeV from the Hadron Spectrum Collaboration and an isotropic lattice with 𝑚𝜋 ≈ 220 MeV from the MILC Collaboration. The lattice volume dependence of the method is also examined.

Whyte, Travis [Jülich Supercomputing Center, Jülic↗
DOE OSTI2025

Generalized Ginsparg-Wilson relations: Fermionic anomalies on the lattice

The Ginsparg-Wilson (GW) relation elegantly captures how the anomalous chiral symmetry of a Dirac fermion manifests on the lattice. In this talk, we discuss how the GW relation and its closed-form solution, the overlap operator, can be generalized to Majorana or Dirac fermions in any dimension for finite symmetry transformations (continuous or discrete). We find an exact symmetry which reproduces both perturbative and global anomalies on the lattice. These generalized GW fermions are boundary theories of various bulk symmetry-protected topological phases and thus provide an explicit lattice realization of the fermionic bulk-boundary correspondence central to recent proposals for chiral gauge theories on the lattice.

Singh, Hersh [Fermilab] (ORCID:0000000220026959)↗
NASA NTRS1973

Modernization of the 60-inch telescope at the Mount Wilson Observatory

A contract for modernization of the Mount Wilson 60-inch telescope was awarded. Under this contract, the original hour angle and declination drives were replaced, digital coordinate readouts were added, a Cassegrain/ coude flip cage was built and installed, the telescope was completely rewired, a new control console was installed, and a coude spectrograph was completed. Extensive building modifications also were made to provide a working floor at mezzanine level for a computer and a coude observing room. These modifications and additions were completed by February 1970, and the telescope returned to regular and continuous use for stellar and planetary astronomy.

Source record↗
NASA NTRS1976

The Mount Wilson solar magnetograph - Scanning and data system

The paper describes a computer-operated image-scanning and data-collection system for the magnetograph at the Mt. Wilson 150-foot Tower telescope. The system is based on a minicomputer with a 32K word core memory and a generalized interface unit for controlling image motion, a keyboard, and an associated television screen. Operation of the solar image guider and the data-collection assembly is outlined along with the observation and data-reduction procedures. Advantages of the system include the ability to move the image in almost any conceivable fashion, a wide choice of integration times, and increased accuracy in magnetic and Doppler calibrations as well as in setting of the magnetic zero level.

Howard, R.↗
NASA NTRS1979

Chromospheric scaling laws, width-luminosity correlations, and the Wilson-Bappu effect

Simple scaling laws for the thickness and mean electron density of stellar chromospheres as functions of surface gravity and chromospheric heating are proposed. These scaling laws are shown to be a consequence of hydrostatic equilibrium, the influence of gas ionization on plasma cooling functions, and the assumption that chromospheric heating is relatively constant with height. It is argued that line width-luminosity correlations similar to those observed in the Ca II K and Mg II k resonance lines are implied by the chromospheric scaling laws if the outer edges of the K and k emission cores are formed in the Lorentzian wings of the absorption profile. The results are compared with the Wilson-Bappu effect, empirical width-luminosity correlations for Ca II K1 minimum features, and solar-plage profiles of the Ca II K and Mg II k resonance lines.

Ayres, T. R.↗
NASA NTRS1983

Solar rotation results at Mount Wilson

Solar rotation results from Doppler velocity measurements made at Mount Wilson over a period of more than 14 years are presented based on a single reduction procedure. The observations were made with the wavelength 5250.2 A line of Fe I, and wavelength shifts of the line were simultaneously recorded. Data from 188 rotations are presented. Measurements of scattered light along with its effect on the measured rotation rate are given.

Howard, R.↗
NASA NTRS1983

The Mount Wilson magnetograph

In the summer of 1957, an instrument quite similar to the prototype solar magnetograph described by Babcock (1953) was installed at the 150-foot tower telescope at the Mount Wilson Observatory, and daily magnetograph observations of the full disk of the sun were started. During the following years, the instrument was modified and improved on several occasions. The present investigation is concerned with the present state of the magnetograph, which was largely rebuilt during 1981. Attention is given to the spectrograph entrance slit, the diffraction grating, the exit slit, the employed microprocessor, the setup procedure, the magnetic signal, the Doppler signal, and a solar magnetogram.

Howard, R.↗
NASA NTRS1984

Coma morphology and dust-emission pattern of periodic Comet Halley. I - High-resolution images taken at Mount Wilson in 1910

A radial/rotational shift-difference algorithm has been developed to improve visibility of the May-June 1910 high-resolution images taken at Mount Wilson of Comet Halley. Dust features for a period of up to three days were identified, which consisted of discrete active areas emitting dust continuously from the sunlit hemisphere of the rotating nucleus. A lower limit of the comet's rotation period was approximated at one day, and expansion velocities of the dust features were determined to be in the range of 0.2-0.3 km/s. Based on relative photometry of a bright jet, it was proposed that the column density of dust ejecta in the jet exceeded the density in the coma by a factor greater than or approximately equal to two, and that, if narrow along the line of light, the jet might have had a particle number concentration much higher than the coma background. Also noted are numerous ion features.

Larson, S. M.↗
NASA NTRS1984

Recalibration of Mount Wilson Doppler measurements (Research note)

The dispersion calibration of spectroscopic velocity measurements made with the 150-ft tower telescope at Mt. Wilson Observatory is revised upward by 0.55 percent on the basis of observations of the six lines of comparable shape and equivalent width nearest the 5250.2-A line of Fe-I used in the solar Doppler rate measurements. The dispersion results are presented in a graph, and the superiority of the Kitt Peak wavelength tables (Pierce and Breckenridge, 1973) over those of Moore et al. (1966) is demonstrated. As a result of the recalibration, all recent spectroscopic velocities from this telescope must be revised downward by 0.55 percent.

Snodgrass, H. B.↗
NASA NTRS1984

Rotation of the sun measured from Mount Wilson white-light images

The instrumentation, data and data reduction procedures used in white light observations of sunspot rotation rates are described. The study covered 62 yr of rotation observations. The data were all gathered using the same Mt. Wilson telescope, which has had three different main lenses in the interval 1981-82. Details of the exposure calibration and lens operation procedures are provided. The data were treated in terms of eight evenly space determinations of the solar limb and account was taken of all sunspots within 60 deg of the central meridian. Spot movements were traced in terms of groups of contiguous individual spots. Large spots rotated slower than small spots, a condition attributed to greater viscous drag in the larger flux tubes in the photosphere. The data tend to confirm theories that the photospheric gas revolves at a different rate than the sunspots.

Howard, R.↗
NASA NTRS1985

The 1984 solar oscillation program of the Mount Wilson 60-foot tower

The instrumentation, data, and preliminary results from the summer, 1984, solar oscillation observing program which was carried out using the 60-foot tower telescope of the Mt. Wilson Observatory are described. This program was carried out with a dedicated solar oscillation observing system and obtained full-disk Dopplergrams every 40 seconds for up to 11 hours per day. Between June and September, 1984, observations were obtained with a Na magneto-optical filter on 90 different days. The data analysis has progressed to the point that spherical harmonic filter functions were employed to generate a few one-dimensional power spectra from a single day's observations.

Rhodes, E. J., Jr.↗
NASA NTRS1987

Wilson Cycle studies

The main activity relating to the study during this half year was a three week field trip to study Chinese sedimentary basins (June 10 to July 3, 1986) at no cost to the project. This study, while of a reconnaissance character, permitted progress in understanding how the processes of island arc-collision and micro-continental collision operated during the Paleozoic in far western China (especially the Junggar and Tarim basins and in the intervening Tien Shan Mountains). These effects of the continuing collision of India and Asia on the area were also studied. Most specifically, these result in the elevation of the Tien Shan to more than 4 km above sea level and the depression of Turfan to move 150m below sea level. Both thrusting and large-scale strike-slip motion are important in producing these elevation changes. Some effort during the half year was also devoted to the study of greenstone-belts in terms of the Wilson Cycle.

Burke, Kevin↗
NASA NTRS1986

The 1984 solar oscillation program of the Mt. Wilson 60-foot tower

The instrumentation, data, and preliminary results from the summer, 1984, solar oscillation observing program which was carried out using the 60-foot tower telescope of the Mt. Wilson Observatory are described. This program was carried out with a dedicated solar oscillation observing system and obtained full-disk Dopplergrams every 40 seconds for up to 11 hours per day. Between June and September, 1984, observations were obtained with a Na magneto-optical filter on 90 different days. The data analysis has progressed to the point that spherical harmonic filter functions were employed to generate a few one-dimensional power spectra from a single day's observations.

Rhodes, Edward J., Jr.↗
NASA NTRS1987

Estimates of the solar internal angular velocity obtained with the Mt. Wilson 60-foot solar tower

Estimates are obtained of the solar internal angular velocity from measurements of the frequency splittings of p-mode oscillations. A 16-day time series of full-disk Dopplergrams obtained during July and August 1984 at the 60-foot tower telescope of the Mt. Wilson Observatory is analyzed. Power spectra were computed for all of the zonal, tesseral, and sectoral p-modes from l = 0 to 89 and for all of the sectoral p-modes from l = 90 to 200. A mean power spectrum was calculated for each degree up to 89. The frequency differences of all of the different nonzonal modes were calculated for these mean power spectra.

Rhodes, Edward J., Jr.↗
NASA NTRS1988

Infrared Observations of Comets Halley and Wilson and Properties of the Grains

The presented papers and discussions at a workshop held at Cornell Univ. are summarized. The infrared observations of Comet Halley and Comet Wilson are reviewed and they are related to optical properties and composition of cometary grains. Relevant laboratory studies are also discussed. Recommendations are made for future infrared comet observations and supporting laboratory investigations.

Hanner, Martha S.↗