3,831 research outputs found
More on coupling coefficients for the most degenerate representations of SO(n)
We present explicit closed-form expressions for the general group-theoretical
factor appearing in the alpha-topology of a high-temperature expansion of
SO(n)-symmetric lattice models. This object, which is closely related to
6j-symbols for the most degenerate representation of SO(n), is discussed in
detail.Comment: 9 pages including 1 table, uses IOP macros Update of Introduction and
Discussion, References adde
Alternative Mathematical Technique to Determine LS Spectral Terms
We presented an alternative computational method for determining the
permitted LS spectral terms arising from electronic configurations. This
method makes the direct calculation of LS terms possible. Using only basic
algebra, we derived our theory from LS-coupling scheme and Pauli exclusion
principle. As an application, we have performed the most complete set of
calculations to date of the spectral terms arising from electronic
configurations, and the representative results were shown. As another
application on deducing LS-coupling rules, for two equivalent electrons, we
deduced the famous Even Rule; for three equivalent electrons, we derived a new
simple rule.Comment: Submitted to Phys. Rev.
Two-Center Integrals for r_{ij}^{n} Polynomial Correlated Wave Functions
All integrals needed to evaluate the correlated wave functions with
polynomial terms of inter-electronic distance are included. For this form of
the wave function, the integrals needed can be expressed as a product of
integrals involving at most four electrons
Hadroproduction of the Chi1 and Chi2 States of Charmonium in 800 GeV/c Proton-Silicon Interactions
The cross sections for the hadroproduction of the Chi1 and Chi2 states of
charmonium in proton-silicon collisions at sqrt{s}=38.8 GeV have been measured
in Fermilab fixed target Experiment 771. The Chi states were observed via their
radiative decay to J/psi+gamma, where the photon converted to e+e- in the
material of the spectrometer. The measured values for the Chi1 and Chi2 cross
sections for x_F>0 are 263+-69(stat)+-32(syst) and 498+-143(stat)+-67(syst) nb
per nucleon respectively. The resulting sigma(Chi1}/sigma(Chi2) ratio of
0.53+-0.20(stat)+-0.07(syst), although somewhat larger than most theoretical
expectations, can be accomodated by the latest theoretical estimates.Comment: 4 pages, 4 figure
Baryon stopping and hyperon enhancement in the improved dual parton model
We present an improved version of the dual parton model which contains a new
realization of the diquark breaking mechanism of baryon stopping. We reproduce
in this way the net baryon yield in nuclear collisions. The model, which also
considers strings originating from diquark-antidiquark pairs in the nucleon
sea, reproduces the observed yields of p and Lambda and their antiparticles and
underestimates cascades by less than 50 %. However, Omega's are underestimated
by a factor five. Agreement with data is restored by final state interaction,
with an averaged cross-section as small as 0.14 mb. Hyperon yields increase
significantly faster than antihyperons, in agreement with experiment.Comment: 40 pages, 18 postscript figure
Low power radiometric partial discharge sensor using composite transistor-reset integrator
The measurement of partial discharge provides a means of monitoring insulation health in high-voltage equipment. Traditional partial discharge measurements require separate installation for each item of plant to physically connect sensors with specific items. Wireless measurement methods provide an attractive and scalable alternative. Existing wireless monitoring technologies which use time-difference-of-arrival of a partial discharge signal at multiple, spatially separated, sensors place high demands on power consumption and cost due to a requirement for rapid sampling. A recently proposed partial discharge monitoring system using a wireless sensor network and measuring received signal strength only, has potential cost and scalability advantages. An incoherent wireless sensor incorporating a transistor-reset integrator has been developed that reduces the measurement bandwidth of the PD events and alleviates the need for high-speed sampling. It is based on composite amplifier techniques to reduce the power requirements by a factor of approximately four without compromising precision. The accuracy of the proposed sensor is compared to that obtained using a high-speed digital sampling oscilloscope. Received energies were measured over a 10 m distance in 1 m increments and produced an error within 1 dB beyond 4 m and 3.2 dB at shorter distances, resulting in a measurement accuracy within 1 m
POEMMA: Probe Of Extreme Multi-Messenger Astrophysics
The Probe Of Extreme Multi-Messenger Astrophysics (POEMMA) mission is being
designed to establish charged-particle astronomy with ultra-high energy cosmic
rays (UHECRs) and to observe cosmogenic tau neutrinos (CTNs). The study of
UHECRs and CTNs from space will yield orders-of-magnitude increase in
statistics of observed UHECRs at the highest energies, and the observation of
the cosmogenic flux of neutrinos for a range of UHECR models. These
observations should solve the long-standing puzzle of the origin of the highest
energy particles ever observed, providing a new window onto the most energetic
environments and events in the Universe, while studying particle interactions
well beyond accelerator energies. The discovery of CTNs will help solve the
puzzle of the origin of UHECRs and begin a new field of Astroparticle Physics
with the study of neutrino properties at ultra-high energies.Comment: 8 pages, in the Proceedings of the 35th International Cosmic Ray
Conference, ICRC217, Busan, Kore
Nuclear pairing: new perspectives
Nuclear pairing correlations are known to play an important role in various
single-particle and collective aspects of nuclear structure. After the first
idea by A. Bohr, B. Mottelson and D. Pines on similarity of nuclear pairing to
electron superconductivity, S.T. Belyaev gave a thorough analysis of the
manifestations of pairing in complex nuclei. The current revival of interest in
nuclear pairing is connected to the shift of modern nuclear physics towards
nuclei far from stability; many loosely bound nuclei are particle-stable only
due to the pairing. The theoretical methods borrowed from macroscopic
superconductivity turn out to be insufficient for finite systems as nuclei, in
particular for the cases of weak pairing and proximity of continuum states. We
suggest a simple numerical procedure of exact solution of the nuclear pairing
problem and discuss the physical features of this complete solution. We show
also how the continuum states can be naturally included in the consideration
bridging the gap between the structure and reactions. The path from coherent
pairing to chaos and thermalization and perspectives of new theoretical
approaches based on the full solution of pairing are discussed.Comment: 47 pages, 11 figure
Churn, Baby, Churn: Strategic Dynamics Among Dominant and Fringe Firms in a Segmented Industry
This paper integrates and extends the literatures on industry evolution and dominant firms to develop a dynamic theory of dominant and fringe competitive interaction in a segmented industry. It argues that a dominant firm, seeing contraction of growth in its current segment(s), enters new segments in which it can exploit its technological strengths, but that are sufficiently distant to avoid cannibalization. The dominant firm acts as a low-cost Stackelberg leader, driving down prices and triggering a sales takeoff in the new segment. We identify a “churn” effect associated with dominant firm entry: fringe firms that precede the dominant firm into the segment tend to exit the segment, while new fringe firms enter, causing a net increase in the number of firms in the segment. As the segment matures and sales decline in the segment, the process repeats itself. We examine the predictions of the theory with a study of price, quantity, entry, and exit across 24 product classes in the desktop laser printer industry from 1984 to 1996. Using descriptive statistics, hazard rate models, and panel data methods, we find empirical support for the theoretical predictions
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