4,185 research outputs found
Performance statistics of the FORTRAN 4 /H/ library for the IBM system/360
Test procedures and results for accuracy and timing tests of the basic IBM 360/50 FORTRAN 4 /H/ subroutine library are reported. The testing was undertaken to verify performance capability and as a prelude to providing some replacement routines of improved performance
Rotation of Low-mass Stars in Taurus with K2
We present an analysis of K2 light curves (LCs) from Campaigns 4 and 13 for members of the young (~3 Myr) Taurus association, in addition to an older (~30 Myr) population of stars that is largely in the foreground of the Taurus molecular clouds. Out of 156 of the highest-confidence Taurus members, we find that 81% are periodic. Our sample of young foreground stars is biased and incomplete, but nearly all stars (37/38) are periodic. The overall distribution of rotation rates as a function of color (a proxy for mass) is similar to that found in other clusters: the slowest rotators are among the early M spectral types, with faster rotation toward both earlier FGK and later M types. The relationship between period and color/mass exhibited by older clusters such as the Pleiades is already in place by Taurus age. The foreground population has very few stars but is consistent with the USco and Pleiades period distributions. As found in other young clusters, stars with disks rotate on average slower, and few with disks are found rotating faster than ~2 days. The overall amplitude of the LCs decreases with age, and higher-mass stars have generally lower amplitudes than lower-mass stars. Stars with disks have on average larger amplitudes than stars without disks, though the physical mechanisms driving the variability and the resulting LC morphologies are also different between these two classes
A Search for Pulsation in Very Low-mass Stars and Brown Dwarfs
Brown dwarfs and very low-mass stars constitute a crucial link between the intertwined processes of star formation and planet formation. To date, however, observational methods to uncover their formation mechanism or determine important properties such as mass and age have been lacking. Pulsation powered by deuterium burning in brown dwarfs and very low-mass stars is a newly suggested phenomenon that offers unprecedented opportunities to probe the interiors and evolution of these objects. We report on a photometric campaign to search for low-amplitude pulsations among young star-cluster members using a number of telescopes
Transport Properties of a spinon Fermi surface coupled to a U(1) gauge field
With the organic compound -(BEDT-TTF)-Cu(CN) in mind, we
consider a spin liquid system where a spinon Fermi surface is coupled to a U(1)
gauge field. Using the non-equilibrium Green's function formalism, we derive
the Quantum Boltzmann Equation (QBE) for this system. In this system, however,
one cannot a priori assume the existence of Landau quasiparticles. We show that
even without this assumption one can still derive a linearized equation for a
generalized distribution function. We show that the divergence of the effective
mass and of the finite temperature self-energy do not enter these transport
coefficients and thus they are well-defined. Moreover, using a variational
method, we calculate the temperature dependence of the spin resistivity and
thermal conductivity of this system.Comment: 12 page
Rotation of Late-Type Stars in Praesepe with K2
We have Fourier analyzed 941 K2 light curves of likely members of Praesepe,
measuring periods for 86% and increasing the number of rotation periods (P) by
nearly a factor of four. The distribution of P vs. (V-K), a mass proxy, has
three different regimes: (V-K)<1.3, where the rotation rate rapidly slows as
mass decreases; 1.3<(V-K)<4.5, where the rotation rate slows more gradually as
mass decreases; and (V-K)>4.5, where the rotation rate rapidly increases as
mass decreases. In this last regime, there is a bimodal distribution of
periods, with few between 2 and 10 days. We interpret this to mean
that once M stars start to slow down, they do so rapidly. The K2 period-color
distribution in Praesepe (790 Myr) is much different than in the Pleiades
(125 Myr) for late F, G, K, and early-M stars; the overall distribution
moves to longer periods, and is better described by 2 line segments. For mid-M
stars, the relationship has similarly broad scatter, and is steeper in
Praesepe. The diversity of lightcurves and of periodogram types is similar in
the two clusters; about a quarter of the periodic stars in both clusters have
multiple significant periods. Multi-periodic stars dominate among the higher
masses, starting at a bluer color in Praesepe ((V-K)1.5) than in the
Pleiades ((V-K)2.6). In Praesepe, there are relatively more light curves
that have two widely separated periods, 6 days. Some of these could
be examples of M star binaries where one star has spun down but the other has
not.Comment: Accepted by Ap
New Records of Vascular Plants in the Yukon Territory VII
Based on field reconnaissance mainly in 2003 in Kluane National Park but also many other areas throughout the Yukon, information is provided on geographically significant plant occurrences. Thirteen native taxa, Agrostis humilis, Blysmopsis rufa, Carex bebbii, C. lenticularis var. dolia, C. nigricans, C. sartwellii, C. siccata, Diphasiastrum sitchense, Najas flexilis, Oxytropis arctica var. arctica, Oxytropis arctica var. murrayi, Saxifraga nelsoniana ssp. carlottae and Swertia perennis and two introduced taxa, Bromus japonicus and Leymus mollis ssp. mollis s.l. are reported new to the flora of the Yukon Territory. Significant range extensions for 109 native and eight introduced taxa are included and three species, Clematis occidentalis, Polygonum persicaria, and Verbena hastata are deleted from the flora
UR-350 Quantum Game Theory
Quantum computing is a computing paradigm that utilizes the properties of quantum mechanics such as superposition, interface and entanglement for data processing and other tasks. Quantum computing can be used to work on the same problems existing supercomputers do but in a much more efficient manner. Classical game theory is a process of modeling that is widely used in AI applications. The extension of this theory to the quantum field is known as quantum game theory. It can be a promising tool for overcoming critical problems in quantum communication and the implementation of quantum artificial intelligence. Quantum game theory allows the player(s) to formulate strategies differing from the conventional way of playing a game. We review the performance of classical and quantum strategies on five classical games by analyzing the logic and outcomes of each approach
Theory and Application of Dissociative Electron Capture in Molecular Identification
The coupling of an electron monochromator (EM) to a mass spectrometer (MS)
has created a new analytical technique, EM-MS, for the investigation of
electrophilic compounds. This method provides a powerful tool for molecular
identification of compounds contained in complex matrices, such as
environmental samples. EM-MS expands the application and selectivity of
traditional MS through the inclusion of a new dimension in the space of
molecular characteristics--the electron resonance energy spectrum. However,
before this tool can realize its full potential, it will be necessary to create
a library of resonance energy scans from standards of the molecules for which
EM-MS offers a practical means of detection. Here, an approach supplementing
direct measurement with chemical inference and quantum scattering theory is
presented to demonstrate the feasibility of directly calculating resonance
energy spectra. This approach makes use of the symmetry of the
transition-matrix element of the captured electron to discriminate between the
spectra of isomers. As a way of validating this approach, the resonance values
for twenty-five nitrated aromatic compounds were measured along with their
relative abundance. Subsequently, the spectra for the isomers of nitrotoluene
were shown to be consistent with the symmetry-based model. The initial success
of this treatment suggests that it might be possible to predict negative ion
resonances and thus create a library of EM-MS standards.Comment: 18 pages, 7 figure
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