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The basis digraphs of p-schemes [article]

Ilia Ponomarenko, Amir Rahnamai Barghi
2007 arXiv   pre-print
It is proved that association schemes with bipartite basis graphs are exactly 2-schemes. This result follows from a characterization of p-schemes for an arbitrary prime p in terms of basis digraphs.
arXiv:0710.0046v1 fatcat:od3yahsqa5ghngceqhtxuh537e

On circular-arc graphs with association schemes [article]

Fatemeh Raei Barandagh, Amir Rahnamai Barghi
2015 arXiv   pre-print
In this paper, we give a characterization of the class of all circular-arc graphs whose schemes are association. Moreover, all association schemes which are the scheme of a circular-arc graph are characterized, specially it is proved that they are Schurian.
arXiv:1501.06315v1 fatcat:qedlf2yek5cnledvhsdqnmsahm

On Characters of a Class of P-polynomial table algebras and applications [article]

Masoumeh Koohestani, Amir Rahnamai Barghi, Amirhossein Amiraslani
2019 arXiv   pre-print
arXiv:1907.04821v1 fatcat:xcycdqjl45awpjdkirpq5s22gq

Non-Isomorphic Graphs with Cospectral Symmetric Powers

Amir Rahnamai Barghi, Ilya Ponomarenko
2009 Electronic Journal of Combinatorics  
The symmetric $m$-th power of a graph is the graph whose vertices are $m$-subsets of vertices and in which two $m$-subsets are adjacent if and only if their symmetric difference is an edge of the original graph. It was conjectured that there exists a fixed $m$ such that any two graphs are isomorphic if and only if their $m$-th symmetric powers are cospectral. In this paper we show that given a positive integer $m$ there exist infinitely many pairs of non-isomorphic graphs with cospectral $m$-th
more » ... symmetric powers. Our construction is based on theory of multidimensional extensions of coherent configurations.
doi:10.37236/209 fatcat:eliorw72hjhxnjnm7a4thdnz5m

On the Nomura algebras of formally self-dual association schemes of class 2

Amir Rahnamai Barghi, Azam Hosseini
2013 Transactions on Combinatorics  
‎‎In this paper‎, ‎the type-II matrices on (negative) Latin square graphs are considered and it is proved that‎, ‎under certain conditions‎, ‎the Nomura algebras of such type-II matrices are trivial‎. ‎In addition‎, ‎we construct type-II matrices on doubly regular tournaments and show that the Nomura algebras of such matrices are also trivial‎.
doaj:2d97d447a55a42d98676998226cd4440 fatcat:2u7c3htxhncmxjvmqh5nfslbgq

On $p$-schemes with the same degrees of thin radical and thin residue

2015 Turkish Journal of Mathematics  
doi:10.3906/mat-1402-76 fatcat:mlcqshi7qnd2jcjn2xzp45zuwa

On the rank of p-schemes

Fatemeh Barandagh, Amir Rahnamai Barghi
Let n > 1 be an integer and p be a prime number. Denote by C p n the class of non-thin association p-schemes of degree p n. A sharp upper and lower bounds on the rank of schemes in C p n with a certain order of thin radical are obtained. Moreover, all schemes in this class whose rank are equal to the lower bound are characterized and some schemes in this class whose rank are equal to the upper bound are constructed. Finally, it is shown that the scheme with minimum rank in C p n is unique up to
more » ... isomorphism, and it is a fusion of any association p-schemes with degree p n .

Standard character condition for table algebras

Amir Rahnamai Barghi, Javad Bagherian
2010 unpublished
It is well known that the complex adjacency algebra A of an association scheme has a specific module, namely the standard module, that contains the regular module of A as a submodule. The character afforded by the standard module is called the standard character. In this paper we first define the concept of standard character for C-algebras and we say that a C-algebra has the standard character condition if it admits the standard character. Among other results we acquire a necessary and
more » ... nt condition for a table algebra to originate from an association scheme. Finally, we prove that given a C-algebra admits the standard character and its all degrees are integers if and only if so its dual.

Analyzing Dynamic Football Passing Network

Amir Rahnamai Barghi, Université D'Ottawa / University Of Ottawa, Université D'Ottawa / University Of Ottawa
In this thesis we are concerned with the analysis of football matches represented as passing graphs, where players are nodes and directed edges indicate the passing of the ball. As opposed to previous work, we label the edges of the graph with the time instants when the ball is passed between two players, thus constructing a time-varying graph. We then employ techniques from social network analysis to study centrality roles and other indicators, keeping into account the evolution of the game in
more » ... time. More precisely, we focus on degree centrality, closeness, betweenness, pagerank, eigenvector centrality, and clustering coefficient, and we compute these measures dividing the overall play time into time windows following two different models. The results are to be compared with a static analysis performed on a unique time window. Our study provides observations that are different and possibly more accurate than the ones that can be obtained by a static analysis, opening the door to a dynamic study of football matches.
doi:10.20381/ruor-6796 fatcat:dodcn5votjbyjgw65bbi4b457m

Author Index - Index des auteurs

2005 Canadian mathematical bulletin  
Rahnamai Barghi Degree Homogeneous Subgroups 394 Djoković, D.Ž., F. Szechtman, K.  ...  See Allen Herman B 500 B Baracco, Luca Extension of Holomorphic Functions From One Side of a Hypersurface 41 Barghi, A. Rahnamai See John D. Dixon 161 Betancor, Jorge J.  ... 
doi:10.4153/cmb-2005-060-5 fatcat:46zar2ze7raszbqamabqqtqb6m

Page 6 of Mathematical Reviews Vol. , Issue 2002A [page]

2002 Mathematical Reviews  
R rtain multiplication Darafsheh, -generations of the Rahnamai Barghi njugacy classes of a rs on the Ashrafi and G. A. Moghani nway group Co; for p > 5 (209 -215); A ind M.  ...  Zahedi On positive implicative hyper K-ideals of types 1, 2,3 and 4 (283 291); Amir Daneshgar and Amir Hashemi, A general n I/O system theory (292-299); B.  ... 

Page 1345 of Mathematical Reviews Vol. , Issue Author Index [page]

Mathematical Reviews  
(see 2002a:00020) 20D15 (20E45) — (with Rahnamai-Barghi, A.) On automorphisms of a class of special p-groups. (English summary) Arch. Math. (Basel) 77 (2001), no. 4, 289-293.  ...  (with Rahnamai-Barghi, A.) On the conjugacy classes of a p-group. (English summary) Proceedings of the 3\st Iranian Mathematics Conference (Tehran, 2000), 216-219, Univ. Tehran, Tehran, 2000.  ... 

Page 1707 of Mathematical Reviews Vol. , Issue Index [page]

Mathematical Reviews  
Rahmatullah Rahnamai Barghi, A. On commutative quasi-hyperrings. (English summary) /tal. J. Pure Appl. Math.  ...  (Jesus Rodriguez Lombardero) 2003k:58004 58A32 (S3C05) Rahmati, Farhad (with Hashemi, Amir) A note on the Fitting ideals in free resolutions. (English summary) Kyungpook Math.  ...