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Unit Matrix


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A unit matrix is aninteger matrix consisting of all 1s. Them×n unit matrix is often denotedJ_(mn), orJ_n ifm=n. Square unit matricesJ_n havedeterminant 0 forn>=2.

Anm×n unit matrix can be generated in theWolfram Language asConstantArray[1,{m,n}].

LetR be acommutative ring with amultiplicative identity. Then the term "unit matrix" is also used to refer to ann×n square matrixA with entries inR for which there exists ann×n square matrixB such that

 AB=BA=I_n,

withI_n is theidentity matrix (MacDuffee 1943, p. 27; Marcus and Minc 1988, p. 69; Marcus and Minc 1992, p. 42).

The term "unit matrix" is sometimes also used as a synonym foridentitymatrix (Akivis and Goldberg 1972, p. 71).


See also

Identity Matrix,UnimodularMatrix,Unitary Matrix

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References

Akivis, M. A. and Goldberg, V. V.An Introduction to Linear Algebra and Tensors. New York: Dover, 1972.Brenner, J. and Cummings, L. "The Hadamard Maximum Determinant Problem."Amer. Math. Monthly79, 626-630, 1972.MacDuffee, C. C.Vectors and Matrices. Washington, DC: Math. Assoc. Amer., 1943.Marcus, M. and Minc, H.Introduction to Linear Algebra. New York: Dover, 1988.Marcus, M. and Minc, H.A Survey of Matrix Theory and Matrix Inequalities. New York: Dover, 1992.

Referenced on Wolfram|Alpha

Unit Matrix

Cite this as:

Weisstein, Eric W. "Unit Matrix." FromMathWorld--A Wolfram Resource.https://mathworld.wolfram.com/UnitMatrix.html

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Created, developed and nurtured by Eric Weisstein at Wolfram Research

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