On the reduction of Yutsis graphs

نویسندگان

  • Dries Van Dyck
  • Veerle Fack
چکیده

General angular momentum recoupling coefficients can be expressed as a summation formula over products of 6-j coefficients. Yutsis, Levinson and Vanagas developed graphical techniques for representing the general recoupling coefficient as a cubic graph and they describe a set of reduction rules allowing a stepwise generation of the corresponding summation formula. This paper gives an overview of the stateof-the-art heuristic algorithms, used in the latest version of our GYutsis program, for calculating general recoupling coefficients. By means of an experimental setup we show that, in particular for problems of higher order, this approach yields summation formulae which are at least as good, but are often more concise than those obtained by previous algorithms. We also give a counter-example showing that that the widespread convention of reducing girth cycles first does not always lead to a shortest reduction.

برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید

ثبت نام

اگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید

منابع مشابه

Graph structural properties of non-Yutsis graphs allowing fast recognition

Yutsis graphs are connected simple graphs which can be partitioned into two vertex-induced trees. Cubic Yutsis graphs were introduced by Jaeger as cubic dual Hamiltonian graphs, and these are our main focus. Cubic Yutsis graphs also appear in the context of the quantum theory of angular momenta, where they are used to generate summation formulae for general recoupling coefficients. Large Yutsis...

متن کامل

To be or not to be Yutsis: Algorithms for the decision problem

Generalized recoupling coefficients or 3nj-coefficients can be expressed as multiple sums over products of Racah or 6j-coefficients [1]. The problem of finding an optimal summation formula (i.e. with a minimal number of Racah coefficients) for a given 3nj-coefficient is equivalent to finding an optimal reduction of a so-called Yutsis graph [2]. In terms of graph theory Yutsis graphs are connect...

متن کامل

Two-geodesic transitive graphs of prime power order

In a non-complete graph $Gamma$, a vertex triple $(u,v,w)$ with $v$ adjacent to both $u$ and $w$ is called a $2$-geodesic if $uneq w$ and $u,w$ are not adjacent. The graph $Gamma$ is said to be   $2$-geodesic transitive if its automorphism group is transitive on arcs, and also on 2-geodesics. We first produce a reduction theorem for the family of $2$-geodesic transitive graphs of prime power or...

متن کامل

Application of n-distance balanced graphs in distributing management and finding optimal logistical hubs

Optimization and reduction of costs in management of distribution and transportation of commodity are one of the main goals of many organizations. Using suitable models in supply chain in order to increase efficiency and appropriate location for support centers in logistical networks is highly important for planners and managers. Graph modeling can be used to analyze these problems and many oth...

متن کامل

Investigating the Causes for Repeating Periapical Radiographies in Radiology Department of School of Dentistry and the Effect of Education on its Reduction

Introduction: Despite quite a lot of risks resulting from repetitious radiographies, supervision on dental radiographies' repetition may serve as custody against radius. The aim of this study was to investigate the causes for repeating periapical radiography in radiology department of school of dentistry and the effect of education on repeatition reduction in Yazd University of Medical Sciences...

متن کامل

ذخیره در منابع من


  با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید

برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید

ثبت نام

اگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید

عنوان ژورنال:
  • Discrete Mathematics

دوره 307  شماره 

صفحات  -

تاریخ انتشار 2007