16,364 research outputs found
Chiral structure of nucleon gravitational form factors
We study the low momentum behavior of nucleon gravitational form factors in
the framework of the heavy baryon chiral perturbation theory. At zero recoil
they determine the momentum and spin apportion between nucleon constituents.
Our result provides an insight into the response of the nucleon's pion cloud to
an external weak gravitational field and establishes a theoretical framework
for extrapolation of experimental and lattice data on the nucleon form factors
to zero momentum transfer. We also discuss form factors corresponding to
higher-rank tensor currents related to the moments of generalized parton
distributions.Comment: 10 pages, LaTeX, 1 figur
Baryons in Partially-Quenched Chiral Perturbation Theory
I discuss the inclusion of baryons into partially-quenched chiral
perturbation theory and describe one-loop calculations that have been
performed.Comment: Lattice2002(matrixel) : talk presented at Lattice 2002, 7 page
Beyond the Big Leave: The Future of U.S. Automotive Human Resources
Based on industry interviews and trends analyses, forecasts employment levels and hiring nationwide and in Michigan through 2016, and compiles automakers' input on technical needs, hiring criteria, and suggestions for training and education curricula
Arithmetic Properties of Overpartition Pairs
Bringmann and Lovejoy introduced a rank for overpartition pairs and
investigated its role in congruence properties of , the number of
overpartition pairs of n. In particular, they applied the theory of Klein forms
to show that there exist many Ramanujan-type congruences for the number
. In this paper, we shall derive two Ramanujan-type identities and
some explicit congruences for . Moreover, we find three ranks as
combinatorial interpretations of the fact that is divisible by
three for any n. We also construct infinite families of congruences for
modulo 3, 5, and 9.Comment: 19 page
Rearranging Pionless Effective Field Theory
We point out a redundancy in the operator structure of the pionless effective
field theory which dramatically simplifies computations. This redundancy is
best exploited by using dibaryon fields as fundamental degrees of freedom. In
turn, this suggests a new power counting scheme which sums range corrections to
all orders. We explore this method with a few simple observables: the deuteron
charge form factor, n p -> d gamma, and Compton scattering from the deuteron.
Higher dimension operators involving electroweak gauge fields are not
renormalized by the s-wave strong interactions, and therefore do not scale with
inverse powers of the renormalization scale. Thus, naive dimensional analysis
of these operators is sufficient to estimate their contribution to a given
process.Comment: 15 pages LaTeX, 9 eps figures, discussions extended and references
adde
Precision muon lifetime and capture experiments at PSI
The muLan experiment at the Paul Scherrer Institute will measure the lifetime
of the positive muon with a precision of 1 ppm, giving a value for the Fermi
coupling constant G_F at the level of 0.5 ppm. Meanwhile, by measuring the
observed lifetime of the negative muon in pure hydrogen, the muCap experiment
will determine the rate of muon capture, giving the proton's pseudoscalar
coupling g_p to 7%. This coupling can be calculated precisely from heavy baryon
chiral perturbation theory and therefore permits a test of QCD's chiral
symmetry.Comment: 4 pages, 2 figures; proceedings of the 6th International Workshop on
Neutrino Factories and Superbeams (NuFACT04), July 26-August 1, 2004, Osaka,
Japan; revised to add one reference (other small edits to conserve length
Discovery and Extraction of Protein Sequence Motif Information that Transcends Protein Family Boundaries
Protein sequence motifs are gathering more and more attention in the field of sequence analysis. The recurring patterns have the potential to determine the conformation, function and activities of the proteins. In our work, we obtained protein sequence motifs which are universally conserved across protein family boundaries. Therefore, unlike most popular motif discovering algorithms, our input dataset is extremely large. As a result, an efficient technique is essential. We use two granular computing models, Fuzzy Improved K-means (FIK) and Fuzzy Greedy K-means (FGK), in order to efficiently generate protein motif information. After that, we develop an efficient Super Granular SVM Feature Elimination model to further extract the motif information. During the motifs searching process, setting up a fixed window size in advance may simplify the computational complexity and increase the efficiency. However, due to the fixed size, our model may deliver a number of similar motifs simply shifted by some bases or including mismatches. We develop a new strategy named Positional Association Super-Rule to confront the problem of motifs generated from a fixed window size. It is a combination approach of the super-rule analysis and a novel Positional Association Rule algorithm. We use the super-rule concept to construct a Super-Rule-Tree (SRT) by a modified HHK clustering, which requires no parameter setup to identify the similarities and dissimilarities between the motifs. The positional association rule is created and applied to search similar motifs that are shifted some residues. By analyzing the motifs results generated by our approaches, we realize that these motifs are not only significant in sequence area, but also in secondary structure similarity and biochemical properties
Deuteron Compton Scattering in Effective Field Theory And Spin-Independent Nucleon Polarizabilities
Deuteron Compton scattering is calculated to in pionless
effective field theory using a dibaryon approach. The vector amplitude, which
was not included in the previous pionless calculations, contributes to the
cross section at and influences significantly the extracted
values of nucleon electric polarizability at incident photon energy 49 MeV. We
recommend future high precision deuteron compton scattering experiments being
performed at 25-35 MeV photon energy where the nucleon polarizability effects
are appreciable and the pionless effective field theory is most reliable. For
example, a measurement at 30 MeV with a 3% error will constrain the isoscalar
nucleon electric polarizability with a error.Comment: 11 pages, 5 figures include
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