04/06/2011
MaierSaupe theory is the canonical mean field description of thermotropic nematic liquid crystals. In this paper, we examine the predictions of the theory in four spatial dimensions. Representations of the order parameter tensor and the existence of new phases are discussed. The phase diagram, based on numerical solution of the selfconsistent equations and Landau theory, is presented. Orientational order decreases as the number of spatial dimensions is increased.
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01/01/2006
We find a bound for the Goldie dimension of hereditary modules in terms of the cardinality of the generating sets of their quasiinjective hulls. Several consequences are deduced. In particular, it is shown that every finitely generated hereditary module with countably generated quasiinjective hull is noetherian. It is also shown that every right hereditary ring with finitely generated injective hull is right artinian, thus answering a long standing open question posed by Dung, Gómez Pardo and Wisbauer.
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01/01/2008
We investigate negacyclic and cyclic codes of length ps over the finite field Fpa. Negacyclic codes of length ps are precisely the ideals of the chain ring Fpa [x] / 〈xp^s+1〉. This structure is then used to obtain the Hamming distance distribution of the class of such negacyclic codes, which also provides Hamming weight distributions and enumerations of several codes. An onetoone correspondence between negacyclic and cyclic codes is established to carry accordingly those results of negacyclic codes to cyclic codes.
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06/01/2012
Let Q be the field of rational numbers. As a module over the ring Z of integers, Q is Zprojective, but QZ is not a projective module. Contrary to this situation, we show that over a prime right noetherian right hereditary right Vring R, a right module P is projective if and only if P is Rprojective. As a consequence of this we obtain the result stated in the title. Furthermore, we apply this to affirmatively answer a question that was left open in a recent work of Holston, LópezPermouth and Orhan Ertag (2012) by showing that over a right noetherian prime right SIring, quasiprojective right modules are projective or semisimple.
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01/01/2016
This paper overviews the study of skew Θλconstacyclic codes over finite fields and finite commutative chain rings. The structure of skew Θλconstacyclic codes and their duals are provided. Among other results, we also consider the Euclidean and Hermitian dual codes of skew Θcyclic andskew Θnegacyclic codes over finite chain rings in general and over Fpm + uFpm in particular. Moreover, general decoding procedure for decoding skew BCH codes with designed distance and an algorithm for decoding skew BCH codes are discussed.
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01/01/2013
A ring R is called a right weakly Vring (briefly, a right WVring) if every simple right Rmodule is Xinjective, where X is any cyclic right Rmodule with XR ≇ RR. In this note, we study the structure of right WVrings R and show that, if R is not a right Vring, then R has exactly three distinct ideals, 0 ⊂ J ⊂ R, where J is a nilpotent minimal right ideal of R such that R/J is a simple right Vdomain. In this case, if we assume additionally that RJ is finitely generated, then R is left Artinian and right uniserial with composition length 2. We also show that a strictly right WVring with Jacobson radical J is a Frobenius local ring if and only if the injective hull of JR is uniserial. Some other results are obtained in the connection with the Noetherian property of right WVrings and related rings.
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05/06/2013
Let p≠3 be any prime. A classification of constacyclic codes of length 3ps over the finite field Fpm is provided. Based on this, the structures in terms of polynomial generators of all such constacyclic codes and their duals are established. Among other results, we show that selfdual cyclic codes of length 3ps exist only when p=2, and in such case, those selfdual codes are listed.
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01/01/2016
The aim of this paper is to determine the algebraic structures of all λconstacyclic codes of length 2 p s over the finite commutative chain ring F p m + u F p m , where p is an odd prime and u 2 = 0 . For this purpose, the situation of λ is mainly divided into two cases separately. If the unit λ is not a square and λ = α + u β for nonzero elements α , β of F p m , it is shown that the ambient ring ( F p m + u F p m ) x / { x 2 p s  ( α + u β ) } is a chain ring with the unique maximal ideal { x 2  α 0 } , and thus ( α + u β ) constacyclic codes are { ( x 2  α 0 ) i } for 0 ≤ i ≤ 2 p s . If the unit λ is not a square and λ = γ for some nonzero element γ of F p m , such λconstacyclic codes are classified into 4 distinct types of ideals. The detailed structures of ideals in each type are provided. Among other results, the number of codewords and the dual of every λconstacyclic code are obtained.
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05/01/2015
For any different odd primes ℓ and p, structure of constacyclic codes of length 2ℓmpn over the finite field Fq of characteristic p and their duals is established in terms of their generator polynomials. Among other results, the characterization and enumeration of all linear complementary dual and selfdual constacyclic codes of length 2ℓmpn are obtained.
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11/20/2014
An equivalence relation is introduced on the nonzero elements of the finite field Fpm to classify constacyclic codes of arbitrary length over Fpm. According to the equivalence classes, all constacyclic codes of length ℓps over Fpm and their duals are characterized, where ℓ is a prime different from p and s is a positive integer. Selfdual cyclic codes of length ℓps over Fpm exist precisely when p is equal to two; in this case, all selfdual cyclic codes of length 2sℓ over F2m are presented.
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