Research article

Jordan matrix algebras defined by generators and relations

  • Received: 07 October 2021 Accepted: 22 November 2021 Published: 24 November 2021
  • MSC : 17C10, 16S10, 16S50

  • In the present paper we describe Jordan matrix algebras over a field by generators and relations. We prove that the minimun number of generators of some special Jordan matrix algebras over a field is 2.

    Citation: Yingyu Luo, Yu Wang, Junjie Gu, Huihui Wang. Jordan matrix algebras defined by generators and relations[J]. AIMS Mathematics, 2022, 7(2): 3047-3055. doi: 10.3934/math.2022168

    Related Papers:

    [1] Mohd Arif Raza, Huda Eid Almehmadi . Lie (Jordan) $ \sigma- $centralizer at the zero products on generalized matrix algebra. AIMS Mathematics, 2024, 9(10): 26631-26648. doi: 10.3934/math.20241295
    [2] Ai-qun Ma, Lin Chen, Zijie Qin . Jordan semi-triple derivations and Jordan centralizers on generalized quaternion algebras. AIMS Mathematics, 2023, 8(3): 6026-6035. doi: 10.3934/math.2023304
    [3] Xiuhai Fei, Zhonghua Wang, Cuixian Lu, Haifang Zhang . Higher Jordan triple derivations on $ * $-type trivial extension algebras. AIMS Mathematics, 2024, 9(3): 6933-6950. doi: 10.3934/math.2024338
    [4] Shan Li, Kaijia Luo, Jiankui Li . Generalized Lie $ n $-derivations on generalized matrix algebras. AIMS Mathematics, 2024, 9(10): 29386-29403. doi: 10.3934/math.20241424
    [5] Dan Liu, Jianhua Zhang, Mingliang Song . Local Lie derivations of generalized matrix algebras. AIMS Mathematics, 2023, 8(3): 6900-6912. doi: 10.3934/math.2023349
    [6] Gonca Kizilaslan . The altered Hermite matrix: implications and ramifications. AIMS Mathematics, 2024, 9(9): 25360-25375. doi: 10.3934/math.20241238
    [7] Yongge Tian . Miscellaneous reverse order laws and their equivalent facts for generalized inverses of a triple matrix product. AIMS Mathematics, 2021, 6(12): 13845-13886. doi: 10.3934/math.2021803
    [8] He Yuan, Zhuo Liu . Lie $ n $-centralizers of generalized matrix algebras. AIMS Mathematics, 2023, 8(6): 14609-14622. doi: 10.3934/math.2023747
    [9] Zengtai Gong, Jun Wu, Kun Liu . The dual fuzzy matrix equations: Extended solution, algebraic solution and solution. AIMS Mathematics, 2023, 8(3): 7310-7328. doi: 10.3934/math.2023368
    [10] Kezheng Zuo, Dragana S. Cvetković-Ilić, Jiale Gao . GBD and $ \mathcal{L} $-positive semidefinite elements in $ C^* $-algebras. AIMS Mathematics, 2025, 10(3): 6469-6479. doi: 10.3934/math.2025295
  • In the present paper we describe Jordan matrix algebras over a field by generators and relations. We prove that the minimun number of generators of some special Jordan matrix algebras over a field is 2.



    Let F be a field of characteristic not 2. Let A be an F-algebra. By A(+) we denote the Jordan algebra induced by A in the usual manner:

    ab=12(ab+ba).

    We call A(+) the special Jordan algebra. There exist Jordan algebras that are not special, they are called exceptional. Let S be a subset of A(+). By <S> we denote the subalgebra of A(+) generated by S. For more detailed introduction of Jordan algebras we refer the reader a book of Jacobson [7].

    Let X be a nonempty set. The free algebra on X over F will be denoted by F(X). Let F(X)(+) be the Jordan algebra induced by F(X) in the usual manner. Let R be a nonempty subset of F(X)(+). By (R) we denote the ideal of F(X)(+) generated by R. This forms the Jordan factor algebra F(X)(+)/(R). By the universal property of F(X), a function f:XA can be extended to an algebra homomorphism ˉf from F(X) into A. It is clear that ˉf induces an algebra homomorphism from F(X)(+) into A(+). Suppose that ˉf(R)=0. We note that there exists an algebra homomorphism ˆf from F(X)(+)/(R) into A(+).

    Set X={ξi|iI} and R={fj=fj(ξi1,,ξin(j))|jJ}. Note that every element in R is a Jordan polynomial. For example,

    2ξ1+ξ2ξ3ξ43.

    Denote the coset ξi+(R) in F(X)(+)/(R) by xi. Note that

    fj(xi1,,xin(j))=0

    for every jJ. Following the case of algebras in [1,Section 6.2], we write F(X)(+)/(R) as L(X;R)(+). We say that this Jordan algebra is defined by the generators xi and relations fj. We always hope that the number of generators of L(X,R)(+) is the minimum. For more detailed introduction of generators and relations of algebras we refer the reader to [1,Section 6.2].

    As we know, both matrix algebras and Jordan matrix algebras are important algebras that we often come across. We remand the reader to the papers [5,6,7,8,9,10,11,12,13] for a general theory of matrix Jordan algebras and the papers [2,3,4] that focus on polynomial identities of Jordan matrix algebras. It is easy to check that the minimun number of generators of matrix algebras over a field is 2 (see Proposition 1). However, it is not easy to determine the minimun number of generators of Jordan matrix algebras over a field.

    In the present paper we shall describe Jordan matrix algebras over a field by generators and relations (see Theorem 2.1). We prove that the minimun number of generators of some special Jordan matrix algebras over a field is 2.

    Let n2 be an integer. By Mn(F) we denote the algebra of all n×n matrices over F. By eij we denote the standard matrix unit of Mn(F). By δij we denote the symbol of Kronecker delta.

    We begin with the following simple result.

    Theorem 2.1. Let F be a field. Set

    X={ξ,η,ρ}.

    Set

    ξ11=ξ,ξ12=2ξ11η.

    We set inductively

    ξ1,i+1=2ξ1iη

    for all i=2,,n1. Similarly, we set inductively

    ξi+1,1=2ξi1ρ

    for all i=1,,n1. Furthemore, we set

    ξij=2ξi1ξ1jδijξ11

    for all i,j=2,,n. Let R be the following subset of L(X)(+):

    ξξ11;ηn1i=1ξi,i+1;ρn1i=1ξi+1,i;2ξijξstδjsξitδitξsj,i,j,s,t=1,,n;ni=1ξii1.

    We have that L(X,R)(+)Mn(F)(+).

    Proof. Set

    x=ξ+(R);y=η+(R);z=ρ+(R);xij=ξij+(R),i,j=1,,n.

    It follows from the elements in R that

    x=x11;y=n1i=1xi,i+1;z=n1i=1xi+1,i;2xijxst=δjsxit+δitxsj,i,j,s,t=1,,n;ni=1xii=1.

    It follows from the relation above that every element of L(X;R)(+) is a linear combination of the following set

    T={xij|i,j=1,2,,n}.

    We claim that T is an independent subset of L(X,R)(+). Suppose that

    ni,j=1λijxij=0 (2.1)

    for some λijF. We define a function f:XMn(F)(+) as follows:

    f(ξ)=e11,f(η)=n1i=1ei,i+1,f(ρ)=n1j=1ej+1,j.

    By the universal property of F(X) we have that there exists an algebra homomorphism ˉf:F(X)(+)Mn(F)(+) such that

    ˉf(ξ)=e11,ˉf(η)=n1i=1ei,i+1,ˉf(ρ)=n1j=1ej+1,j

    and

    ˉf(ξij)=2ˉf(ξi1ξ1j)δijˉf(ξ11=2ˉf(ξi1)ˉf(ξ1j)δijˉf(ξ11)=2ei1e1jδije11=eij

    for all i,j=1,,n. Note that {eij|i,j=1,,n} is a basis of Mn(F)(+). This implies that ˉf is surjective. It is easy to check that ˉf(R)=0. Hence there exists a surjective algebra homomorphism ˆf:L(X;R)(+)Mn(F)(+) such that

    ˆf(x)=e11,ˆf(y)=n1i=1ei,i+1,ˆf(z)=n1j=1ej+1,j

    and

    ˆf(xij)=eij

    for all i,j=1,,n. We get from (2.1) that

    ni=1λijeij=0.

    It implies that λij=0 for all i,j=1,,n. Consequently, T is a basis of L(X,R)(+). In view of the above relations we get that the Jordan operation table of T is the same as that of {eij|i,j=1,,n}, a standard basis of Mn(F)(+). Therefore L(X,R)(+)Mn(F)(+). The proof of the result is complete.

    We remark that Theorem 2.1 implies the following result:

    Corollary 1. Let F be a field. We have that

    Mn(F)(+)=e11,n1i=1ei,i+1,n1j=1ej+1,j.

    In view of Corollary 2.1 we see that every Jordan matrix algebra over a field can be generated by three elements.

    We remark that the minimun number of generators of matrix algebras over a field is 2. For example, we easily prove the following result. We give its proof for completeness.

    Proposition 2.1. Let F be a field. We have that

    Mn(F)=n1i=1ei,i+1,n1j=1ej+1,j.

    Proof. Set

    E=n1i=1ei,i+1,Q=n1j=1ej+1,j.

    We have that

    En1Qn1=e11∈<E,Q>.

    We get that <e11,E,Q>=<E,Q>. In view of Corollary 2.1 we note that Mn(F)(+)=<e11,E,Q>. This implies that

    Mn(F)=<e11,E,Q>=<E,Q>.

    This proves the result.

    We now give the main result of the paper, which shows that some special Jordan matrix algebras over a field can be generated by two elements.

    Theorem 2.2. Let F be a field. Let n3 be an integer. Suppose that char(F)=0 or char(F)>[3(n1)2], the integer part of 3(n1)2. Set

    X={ξ,η}.

    We set

    ai=i,i=1,,n2;an1=[3(n1)2];an=n1

    and

    (λ1λ2λn)=(a1,a21,,an1a2,a22,,an2an,a2n,,ann)1(100) (2.2)

    Set

    ξ11=λ1ξη+λ2(ξη)2++λn(ξη)n.

    We set

    ξ12=ξ11ξ.

    Furthermore, we set inductively

    ξ1,i+1=[i+12]1ξ1iξ

    for all i=1,,n2 and

    ξ1n=(n1)1ξ1,n1ξ.

    Similarly, we set

    ξ21=2ξ11η.

    We set inductively

    ξi+1,1=2ξi1η

    for all i=1,,n1. Moreover, we set

    ξij=2(ξi1ξ1j)δijξ11

    for all i,j=2,,n. Let R be the following subset of L(X)(+):

    ξn2i=12[i+12]ξi,i+12(n1)ξn1,n;ηn1i=1ξi+1,i;2ξijξstδjsξitδitξsj,i,j,s,t=1,,n;ni=1ξii1.

    We have that L(X,R)(+)Mn(F)(+). Moreover, the minimun number of generators of Mn(F)(+) is 2.

    Proof. Set

    x=ξ+(R);y=η+(R);xij=ξij+(R),i,j=1,,n.

    It follows from the elements in R that

    x=n2i=12[i+12]xi,i+1+2(n1)xn1,n;y=n1i=1xi+1,i;2xijxst=δjsxit+δitxsj,i,j,s,t=1,,n;ni=1xii=1.

    It follows from the relation above that every element of L(X;R)(+) is a linear combination of the following set

    T={xij|i,j=1,2,,n}.

    We claim that T is an independent subset of L(X,R)(+). Suppose that

    ni,j=1λijxij=0 (2.3)

    for some λijF. We define a function f:XMn(F)(+) as follows:

    f(ξ)=2(n2i=1[i+12]ei,i+1+(n1)en1,n),f(η)=n1j=1ej+1,j.

    By the universal property of F(X) we have that there exists an algebra homomorphism ˉf:F(X)(+)Mn(F)(+) such that

    ˉf(ξ)=2(n2i=1[i+12]ei,i+1+(n1)en1,n),ˉf(η)=n1j=1ej+1,j

    and

    ˉf(ξη)=ˉf(ξ)ˉf(η)=2(n2i=1[i+12]ei,i+1+(n1)en1,n)(n1j=1ej+1,j)=n1i=1ieii+[3(n1)2]en1,n1+(n1)enn=ni=1aieii.

    We get from (2.2) that

    ˉf(ξ11)=ˉf(λ1ξη+λ2(ξη)2++λn(ξη)n)=λ1ˉf(ξη)+λ2ˉf(ξη)2++λnˉf(ξη)n=λ1(ni=1aieii)+λ2(ni=1aieii)2   ++λn(ni=1aieii)n=(λ1a1+λ2a21++λnan1)e11++   (λ1an+λ2a2n++λnann)enn=e11.

    We have that

    ˉf(ξ12)=ˉf(ξ11ξ)=ˉf(ξ11)ˉf(ξ)=e11(n2i=12[i+12]ei,i+1+2(n1)en1,n)=e12

    and

    ˉf(ξ1,i+1)=[i+12]1ˉf(ξ1iξ)=e1,i+1

    for all i=1,,n2. Moreover, we have that

    ˉf(ξ1n)=(n1)1ˉf(ξ1,n1ξ)=e1n.

    Similarly, we have that

    ˉf(ξi1)=ei1

    for all i=2,,n1. Moreover, we have that

    ˉf(ξij)=2ˉf(ξi1ξ1j)δijˉf(ξ11)=2ei1e1jδije11=eij

    for all i,j=2,,n. Note that {eij|i,j=1,,n} is a basis of Mn(F)(+). This implies that ˉf is surjective. It is easy to check that ˉf(R)=0. Hence there exists a surjective algebra homomorphism ˆf:L(X;R)(+)Mn(F)(+) such that

    ˆf(x)=n2i=12[i+12]ei,i+1+2(n1)en1,n,ˆf(y)=n1j=1ej+1,j.

    Moreover, we have that

    ˆf(x1j)=e1j,ˆf(xi1)=ei1

    for all i,j=1,,n and so

    ˆf(xij)=eij

    for all i,j=1,,n. It follows from (2.3) that

    ni,j=1λijeij=0.

    This implies that λij=0 for all i,j=1,,n. Consequently, T is a basis of L(X,R)(+). In view of the above relations we see that the Jordan operation table of T is the same as that of {eij|i,j=1,2,,n}, a standard basis of Mn(F)(+). Therefore L(X,R)(+)Mn(F)(+).

    Suppose that Mn(F)(+)=<A> for some AMn(F)(+). It is clear that Mn(F)=<A>. This implies that Mn(F) is commutative, a contradiction. We get that the minimun number of generators of Mn(F)(+) is 2. The proof of the result is complete.

    We remark that Theorem 2.2 implies the following result:

    Corollary 2.2. Let F be a field. Let n3 be an integer. Suppose that char(F)=0 or char(F)>[3(n1)2]. We have that

    Mn(F)(+)=n2i=12[i+12]ei,i+1+2(n1)en1,n,n1j=1ej+1,j.

    The main conclusion of the paper is to show that the minimun number of generators of Mn(F)(+) (where n3 and char(F)=0 or char(F)>[3(n1)2]) is 2.

    The authors are grateful to the referees for useful comments.

    The authors declare no conflicts of interest in this paper.



    [1] M. Brešar, Introduction to nocommutative algebras, Springer, 2014. doi: 10.1007/978-3-319-08693-4.
    [2] L. Centrone, F. Martino, A note on cocharacter sequence of Jordan upper triangular matrix algebra, Commun. Algebra, 45 (2017), 1687–1695. doi: 10.1080/00927872.2016.1222408. doi: 10.1080/00927872.2016.1222408
    [3] L. Centrone, F. Martino, M. da Silva Souza, Specht property for some varieties of Jordan algebras of almost polynomial growth, J. Algebra, 521 (2019), 137–165. doi: 10.1016/j.jalgebra.2018.11.017. doi: 10.1016/j.jalgebra.2018.11.017
    [4] A. Cirrito, F. Martino, Ordinary and graded cocharacter of the Jordan algebra of 2×2 upper triangular matrices, Linear Algebra Appl., 451 (2004), 246–259. doi: 10.1016/j.laa.2014.03.011. doi: 10.1016/j.laa.2014.03.011
    [5] C. Costara, Nonlinear invertibility preserving maps on matrix algebras, Linear Algebra Appl., 602 (2020), 216–222. doi: 10.1016/j.laa.2020.05.010. doi: 10.1016/j.laa.2020.05.010
    [6] M. Grašič, Zero product determined Jordan algebra, Linear Multilinear Algebra, 59 (2011), 671–685. doi: 10.1080/03081087.2010.485199. doi: 10.1080/03081087.2010.485199
    [7] N. Jacobson, Structure and representations of Jordan algebras, Colloquium Publications, Vol. 39, American Mathematical Society, 1968.
    [8] M. Kochetov, F. Y. Yasumura, Group grading on the Lie and Jordan algebras of block-triangular matrices, J. Algebra, 537 (2019), 147–172. doi: 10.1016/j.jalgebra.2019.07.020. doi: 10.1016/j.jalgebra.2019.07.020
    [9] X. B. Ma, G. H. Ding, L. Wang, Square-zero determined matrix algebras, Linear Multilinear Algebra, 59 (2011), 1311–1317. doi: 10.1080/03081087.2010.539606. doi: 10.1080/03081087.2010.539606
    [10] K. McCrimmon, A taste of Jordan algebras, Springer, 2004. doi: 10.1007/b97489.
    [11] H. P. Pertersson, The isotopy problem for Jordan matrix algebras, Trans. Amer. Math. Soc., 244 (1978), 185–197. doi: 10.1090/S0002-9947-1978-0506615-7. doi: 10.1090/S0002-9947-1978-0506615-7
    [12] C. C. Xi, J. B. Zhang, Structure of centralizer matrix algebras, Linear Algebra Appl., 622 (2021), 215–249. doi: 10.1016/j.laa.2021.03.034. doi: 10.1016/j.laa.2021.03.034
    [13] D. Y. Wang, Q. Hu C. G. Xia, Jordan derivation of certain Jordan matrix algebras, Linear Multilinear Algebra, 56 (2008), 581–588. doi: 10.1080/03081080701492165. doi: 10.1080/03081080701492165
  • Reader Comments
  • © 2022 the Author(s), licensee AIMS Press. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0)
通讯作者: 陈斌, bchen63@163.com
  • 1. 

    沈阳化工大学材料科学与工程学院 沈阳 110142

  1. 本站搜索
  2. 百度学术搜索
  3. 万方数据库搜索
  4. CNKI搜索

Metrics

Article views(1994) PDF downloads(77) Cited by(0)

Other Articles By Authors

/

DownLoad:  Full-Size Img  PowerPoint
Return
Return

Catalog