Jucys–Murphy element

{{Short description|Elements in representations of the symmetric group}}{{No footnotes|date=November 2021}}

In mathematics, the Jucys–Murphy elements in the group algebra \mathbb{C} [S_n] of the symmetric group, named after Algimantas Adolfas Jucys and G. E. Murphy, are defined as a sum of transpositions by the formula:

:X_1=0, ~~~ X_k= (1 \; k)+ (2 \; k)+\cdots+(k-1 \; k), ~~~ k=2,\dots,n.

They play an important role in the representation theory of the symmetric group.

Properties

They generate a commutative subalgebra of \mathbb{C} [ S_n] . Moreover, Xn commutes with all elements of \mathbb{C} [S_{n-1}] .

The vectors constituting the basis of Young's "seminormal representation" are eigenvectors for the action of Xn. For any standard Young tableau U we have:

:X_k v_U =c_k(U) v_U, ~~~ k=1,\dots,n,

where ck(U) is the content b − a of the cell (ab) occupied by k in the standard Young tableau U.

Theorem (Jucys): The center Z(\mathbb{C} [S_n]) of the group algebra \mathbb{C} [S_n] of the symmetric group is generated by the symmetric polynomials in the elements Xk.

Theorem (Jucys): Let t be a formal variable commuting with everything, then the following identity for polynomials in variable t with values in the group algebra \mathbb{C} [S_n] holds true:

: (t+X_1) (t+X_2) \cdots (t+X_n)= \sum_{\sigma \in S_n} \sigma t^{\text{number of cycles of }\sigma}.

Theorem (OkounkovVershik): The subalgebra of \mathbb{C} [S_n] generated by the centers

: Z(\mathbb{C} [ S_1]), Z(\mathbb{C} [ S_2]), \ldots, Z(\mathbb{C} [ S_{n-1}]), Z(\mathbb{C} [S_n])

is exactly the subalgebra generated by the Jucys–Murphy elements Xk.

See also

References

  • {{Citation

|title=A New Approach to the Representation Theory of the Symmetric Groups. 2

|authorlink1=Okounkov

|first1=Andrei |last1=Okounkov

|authorlink2=Vershik

|first2=Anatoly |last2=Vershik

|year=2004

|volume=307

|journal=Zapiski Seminarov POMI

|arxiv = math.RT/0503040

|postscript= (revised English version). }}

  • {{citation

|title=Symmetric polynomials and the center of the symmetric group ring

|authorlink1=Algimantas Adolfas Jucys

|first1=Algimantas Adolfas |last1=Jucys

| year=1974 | journal=Rep. Mathematical Phys. | volume=5 | issue=1 | pages=107–112

| doi=10.1016/0034-4877(74)90019-6

|bibcode=1974RpMP....5..107J}}

  • {{citation

|title=On the Young operators of the symmetric group

|authorlink1=Algimantas Adolfas Jucys

|first1=Algimantas Adolfas |last1=Jucys

| year=1966 | journal=Lietuvos Fizikos Rinkinys | volume=6 | pages=163–180

|url=https://www.lietuvos-fizikai.lt/chessidr/straipsniai/LietFizRink/LFR-1966-v6-p179-AlgJucys-On_the_Young_operators_of_the_symmetric_groups.pdf

}}

  • {{citation

|title=Factorization of Young projection operators for the symmetric group

|authorlink1=Algimantas Adolfas Jucys

|first1=Algimantas Adolfas |last1=Jucys

| year=1971 | journal=Lietuvos Fizikos Rinkinys | volume=11 | pages=5–10

|url=https://www.lietuvos-fizikai.lt/chessidr/straipsniai/LietFizRink/LFR-1971-v11-p5-AlgJucys-Factorization_of_Young_projection_operators_for_the_symmetric_group.pdf

}}

  • {{citation

|title=A new construction of Young's seminormal representation of the symmetric group

|first1=G. E. |last1=Murphy

| year=1981 | journal=J. Algebra | volume=69 | pages=287–297

|doi=10.1016/0021-8693(81)90205-2

|issue=2

|doi-access=free

}}

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Category:Permutation groups

Category:Representation theory

Category:Symmetry

Category:Representation theory of finite groups

Category:Symmetric functions