4,486 research outputs found
Avalanche in the Valley (Fermions, Anomaly and Unitarity in High-Energy Electroweak Interactions)
Problems related to fermions, unitarity and chiral anomaly in high energy
electroweak interactions, are investigated. Particular attention is paid to the
correct functional integration over fermion fields in the background of
instanton-anti\-instanton type configurations. This leads to an expansion of
correlation functions in terms of a small parameter, , when the
instanton-antiinstanton separation () is large compared to their sizes
(). Applying such a method to widely discussed cases of fermion-number
violation in the electroweak theory, we conclude that there are no theoretical
basis for expecting anomalous cross sections to become observable at energies
in the TeV region.Comment: 11 pages + 1 figure (not included
New Results on Non-Abelian Vortices - further insights into monopole, vortex and confinement
We discuss some of the latest results concerning the non-Abelian vortices.
The first concerns the construction of non-Abelian BPS vortices based on
general gauge groups of the form G= G' x U(1). In particular detailed results
about the vortex moduli space have been obtained for G'=SO(N) or USp(2N). The
second result is about the "fractional vortices", i.e., vortices of the minimum
winding but having substructures in the tension (or flux) density in the
transverse plane. Thirdly, we discuss briefly the monopole-vortex complex.Comment: Latex 20 page
Organopalladium catalyst on S-terminated GaAs(001)-(2Ă6) surface
Organopalladium molecules, such as Pd(CH3COO)2 ({Pd}), immobilized on the S-terminated GaAs(001), termed GaAsâSâ{Pd} have high catalytic activity and cycle durability in the MizorokiâHeck reaction. It is thought that the presence of GaâS bonds in the single atomic layer S-termination is essential for these catalytic properties despite the much higher thickness (~100 nm) of the {Pd} films. In this study, the authors demonstrate the retention of GaâS bonds in ultrathin GaAsâSâ{Pd} by using reflection high-energy electron diffraction and scanning tunneling microscopy (STM). The ultrathin GaAsâSâ{Pd} was prepared by using a vapor-deposition technique. Deposited {Pd} was observed as ~1 nm dotlike structures with STM. The adsorption rate of {Pd} was also investigated
Picosecond electrical spectroscopy using monolithic GaAs circuits
This article describes an experimental apparatus for free-space mm-wave transmission measurements (spectroscopy). GaAs nonlinear transmission lines and sampling circuits are used as picosecond pulse generators and detectors, with planar monolithic bowtie antennas with associated substrate lenses used as the radiating and receiving elements. The received pulse is 270 mV amplitude and 2.4 ps rise time. Through Fourier transformation of the received pulse, 30â250 GHz measurements are demonstrated with <=0.3 dB (rms) accuracy
Fermions, Anomaly and Unitarity in High-Energy Electroweak Scattering
We report the "state of the art" of the problem of violation in
high-energy electroweak scatterings. Results of various analyses point toward
(though do not prove rigorously yet) the "half-suppression", i.e., that the
violating cross section remains suppressed at least by the negative
exponent of the single instanton action, at all energies. Most interesting
techniques developed in this field are reviewed. Particular attention is paid
to unitarity constraints on the anomalous cross section, and to some conceptual
problem involving the use of the optical theorem in the presence of instantons.Comment: 59 (Latex) pages (+13 postscript figures (1075 blocks) available by
e-mail request), GEF-Th-17/199
An investigation of tooth loss factors in elderly patients using panoramic radiographs
Objectives The aim of this study was to observe the dental condition in a group of elderly patients over a period of 10 years in order to clarify important risk factors. Materials and methods Participants were elderly patients (in their eighties) who took panoramic radiographs between 2015 and 2016, and for whom panoramic radiographs taken around 10 year earlier were also available. The number of remaining and lost teeth, the Eichner Index, the presence or absence of molar occlusion, the respective condition of dental pulp, dental crowns, alveolar bone resorption, as well as periapical lesions were investigated through the analysis of panoramic radiographs. Additionally, other important variables were collected from patients' medical records. From the obtained panoramic radiograph sets, the patients' dental condition was investigated, and a systematic comparison was conducted. Results The analysis of the panoramic radiographs showed that the number of remaining teeth decreased from an average of 20.8-15.5, and the percentage of patients with 20 or more teeth decreased from 69.2 to 26.9%. A factor analysis investigating tooth loss risk suggested that tooth loss was associated with the bridge, P2 or greater resorption of the alveolar bone, and apical lesions, and gender (with males having a higher risk compared to females). Conclusions Teeth showing P2 or greater alveolar bone resorption, bridge, and apical lesions on panoramic radiographs are most likely to be lost in an elderly patient's near future. Consequently, this group should be encouraged to visit their dental clinics regularly and receive comprehensive instruction on individual self-care methods
Hierarchical clustering and formation of power-law correlation in 1-dimensional self-gravitating system
The process of formation of fractal structure in one-dimensional
self-gravitating system is examined numerically. It is clarified that
structures created in small spatial scale grow up to larger scale through
clustering of clusters, and form power-law correlation.Comment: 9pages,4figure
Extracting Supersymmetry-Breaking Effects from Wave-Function Renormalization
We show that in theories in which supersymmetry breaking is communicated by
renormalizable perturbative interactions, it is possible to extract the soft
terms for the observable fields from wave-function renormalization. Therefore
all the information about soft terms can be obtained from anomalous dimensions
and beta functions, with no need to further compute any Feynman diagram. This
method greatly simplifies calculations which are rather involved if performed
in terms of component fields. For illustrative purposes we reproduce known
results of theories with gauge-mediated supersymmetry breaking. We then use our
method to obtain new results of phenomenological importance. We calculate the
next-to-leading correction to the Higgs mass parameters, the two-loop soft
terms induced by messenger-matter superpotential couplings, and the soft terms
generated by messengers belonging to vector supermultiplets.Comment: Typos corrected, version to appear in Nucl. Phys.
The dihadron fragmentation function and its evolution
Dihadron fragmentation functions and their evolution are studied in the
process of annihilation. Under the collinear factorization
approximation and facilitated by the cut-vertex technique, the two hadron
inclusive cross section at leading order (LO) is shown to factorize into a
short distance parton cross section and a long distance dihadron fragmentation
function. We provide the definition of such a dihadron fragmentation function
in terms of parton matrix elements and derive its DGLAP evolution equation at
leading log. The evolution equation for the non-singlet quark fragmentation
function is solved numerically with a simple ansatz for the initial condition
and results are presented for cases of physical interest.Comment: 27 pages, 2 column, Revtex4, 21 figure
Nonabelian Faddeev-Niemi Decomposition of the SU(3) Yang-Mills Theory
Faddeev and Niemi (FN) have introduced an abelian gauge theory which
simulates dynamical abelianization in Yang-Mills theory (YM). It contains both
YM instantons and Wu-Yang monopoles and appears to be able to describe the
confining phase. Motivated by the meson degeneracy problem in dynamical
abelianization models, in this note we present a generalization of the FN
theory. We first generalize the Cho connection to dynamical symmetry breaking
pattern SU(N+1) -> U(N), and subsequently try to complete the Faddeev-Niemi
decomposition by keeping the missing degrees of freedom. While it is not
possible to write an on-shell complete FN decomposition, in the case of SU(3)
theory of physical interest we find an off-shell complete decomposition for
SU(3) -> U(2) which amounts to partial gauge fixing, generalizing naturally the
result found by Faddeev and Niemi for the abelian scenario SU(N+1) -> U(1)^N.
We discuss general topological aspects of these breakings, demonstrating for
example that the FN knot solitons never exist when the unbroken gauge symmetry
is nonabelian, and recovering the usual no-go theorems for colored dyons.Comment: Latex 30 page
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