Embedded Random Matrix Ensembles with Lie Symmetries: Results from U(Ω) Wigner-Racah algebra

16th Symmetries in Science

Kota, V.K.B.^1 ; Vyas, Manan^2,3

Physical Research Laboratory, Ahmedabad

380 009, India^1

Department of Physics and Astronomy, Washington State University, Pullman

WA

99164-2814, United States^2

Department of Physics, Yeshiva University, New York

NY

10016, United States^3

关键词: Analytical formulas;    Gaussian unitary ensemble;    Irreducible representations;    Lower order moments;    One-point functions;    Racah coefficients;    Random-matrix ensembles;    Two-body interactions;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/538/1/012011/pdf
DOI  :  10.1088/1742-6596/538/1/012011

来源: IOP

【 摘 要 】

Random matrix ensembles for a system of m number of fermions or bosons in Ω number of single particle levels each r-fold degenerate and interacting with two-body forces are considered. The spectrum generating algebra for these systems is U(rΩ) and a subalgebra of interest is U(rΩ) ⊃ U(Ω) ⊗ SU(r) algebra. Now, for random two-body interactions preserving SU(r) symmetry, one can introduce embedded Gaussian unitary ensemble of random matrices with U(Ω)⊗SU(r) embedding and this class of ensembles are denoted by EGUE(2)-SU(r). Ensembles with r 1,2 and 4 for fermions correspond to spinless fermions, fermions with spin and fermions with Wigner's spin-isospin SU(4) symmetry respectively. Similarly, for bosons r 1, 2 and 3 correspond to spinless bosons, two species boson systems and bosons with spin one respectively. The distinction between fermions and bosons is in the U(Ω) irreducible representations. General formulation based on Wigner-Racah algebra for lower order moments of the one- and two-point functions in eigenvalues generated by EGUE(2)- SU(r) is briefly reviewed. The final formulas for the moments involve only SU(Ω) Racah coefficients. For the fourth moment of the one-point function for r > 1 and for the higher order (> 4) bivariate moments of the two-point function for r ≥ 1, formulas are not available for the SU(Ω) Racah coefficients that are needed. It is necessary to derive analytical formulas for these or develop methods that give asymptotic results (an example for this is given in the paper) or develop methods that allow for their numerical evaluation. This important open problem is discussed in some detail.