17,835 research outputs found
Generalized Background-Field Method
The graphical method discussed previously can be used to create new gauges
not reachable by the path-integral formalism. By this means a new gauge is
designed for more efficient two-loop QCD calculations. It is related to but
simpler than the ordinary background-field gauge, in that even the triple-gluon
vertices for internal lines contain only four terms, not the usual six. This
reduction simplifies the calculation inspite of the necessity to include other
vertices for compensation. Like the ordinary background-field gauge, this
generalized background-field gauge also preserves gauge invariance of the
external particles. As a check of the result and an illustration for the
reduction in labour, an explicit calculation of the two-loop QCD
-function is carried out in this new gauge. It results in a saving of
45% of computation compared to the ordinary background-field gauge.Comment: 17 pages, Latex, 18 figures in Postscrip
LSI/VLSI design for testability analysis and general approach
The incorporation of testability characteristics into large scale digital design is not only necessary for, but also pertinent to effective device testing and enhancement of device reliability. There are at least three major DFT techniques, namely, the self checking, the LSSD, and the partitioning techniques, each of which can be incorporated into a logic design to achieve a specific set of testability and reliability requirements. Detailed analysis of the design theory, implementation, fault coverage, hardware requirements, application limitations, etc., of each of these techniques are also presented
Magneto-Seebeck effect in spin-valve with in-plane thermal gradient
We present measurements of magneto-Seebeck effect on a spin valve with
in-plane thermal gradient. We measured open circuit voltage and short circuit
current by applying a temperature gradient across a spin valve stack, where one
of the ferromagnetic layers is pinned. We found a clear hysteresis in these two
quantities as a function of magnetic field. From these measurements, the
magneto-Seebeck effect was found to be 0.82%.Comment: 10 Pages, 7 figure
A one-sided Prime Ideal Principle for noncommutative rings
Completely prime right ideals are introduced as a one-sided generalization of
the concept of a prime ideal in a commutative ring. Some of their basic
properties are investigated, pointing out both similarities and differences
between these right ideals and their commutative counterparts. We prove the
Completely Prime Ideal Principle, a theorem stating that right ideals that are
maximal in a specific sense must be completely prime. We offer a number of
applications of the Completely Prime Ideal Principle arising from many diverse
concepts in rings and modules. These applications show how completely prime
right ideals control the one-sided structure of a ring, and they recover
earlier theorems stating that certain noncommutative rings are domains (namely,
proper right PCI rings and rings with the right restricted minimum condition
that are not right artinian). In order to provide a deeper understanding of the
set of completely prime right ideals in a general ring, we study the special
subset of comonoform right ideals.Comment: 38 page
Multiple Reggeon Exchange from Summing QCD Feynman Diagrams
Multiple reggeon exchange supplies subleading logs that may be used to
restore unitarity to the Low-Nussinov Pomeron, provided it can be proven that
the sum of Feynman diagrams to all orders gives rise to such multiple regge
exchanges. This question cannot be easily tackled in the usual way except for
very low-order diagrams, on account of delicate cancellations present in the
sum which necessitate individual Feynman diagrams to be computed to subleading
orders. Moreover, it is not clear that sums of high-order Feynman diagrams with
complicated criss-crossing of lines can lead to factorization implied by the
multi-regge scenario. Both of these difficulties can be overcome by using the
recently developed nonabelian cut diagrams. We are then able to show that the
sum of -channel-ladder diagrams to all orders does lead to such multiple
reggeon exchanges.Comment: uu-encoded latex file with 11 postscript figures (20 pages
String Organization of Field Theories: Duality and Gauge Invariance
String theories should reduce to ordinary four-dimensional field theories at
low energies. Yet the formulation of the two are so different that such a
connection, if it exists, is not immediately obvious. With the Schwinger
proper-time representation, and the spinor helicity technique, it has been
shown that field theories can indeed be written in a string-like manner, thus
resulting in simplifications in practical calculations, and providing novel
insights into gauge and gravitational theories. This paper continues the study
of string organization of field theories by focusing on the question of local
duality. It is shown that a single expression for the sum of many diagrams can
indeed be written for QED, thereby simulating the duality property in strings.
The relation between a single diagram and the dual sum is somewhat analogous to
the relation between a old- fashioned perturbation diagram and a Feynman
diagram. Dual expressions are particularly significant for gauge theories
because they are gauge invariant while expressions for single diagrams are not.Comment: 20 pages in Latex, including seven figures in postscrip
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