What can can be said about the sum of a positive semidefinite matrix rank M and a diagonal matrix rank...












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Let's consider the matrix A which is a N dimensional real positive semi-definite square matrix of rank M with M < N and a N dimensional real diagonal matrix D. What can be said about the matrix B = A + D?



If M = N, it is easy to prove exploiting eigenvalue decomposition that B can be any real symmetric matrix. Now I would like to understand which kind of matrices B can be represented if A has rank M < N. If this matrix can be characterised for instance through their eigenvalue spectrum or other properties.










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    0














    Let's consider the matrix A which is a N dimensional real positive semi-definite square matrix of rank M with M < N and a N dimensional real diagonal matrix D. What can be said about the matrix B = A + D?



    If M = N, it is easy to prove exploiting eigenvalue decomposition that B can be any real symmetric matrix. Now I would like to understand which kind of matrices B can be represented if A has rank M < N. If this matrix can be characterised for instance through their eigenvalue spectrum or other properties.










    share|cite|improve this question

























      0












      0








      0







      Let's consider the matrix A which is a N dimensional real positive semi-definite square matrix of rank M with M < N and a N dimensional real diagonal matrix D. What can be said about the matrix B = A + D?



      If M = N, it is easy to prove exploiting eigenvalue decomposition that B can be any real symmetric matrix. Now I would like to understand which kind of matrices B can be represented if A has rank M < N. If this matrix can be characterised for instance through their eigenvalue spectrum or other properties.










      share|cite|improve this question













      Let's consider the matrix A which is a N dimensional real positive semi-definite square matrix of rank M with M < N and a N dimensional real diagonal matrix D. What can be said about the matrix B = A + D?



      If M = N, it is easy to prove exploiting eigenvalue decomposition that B can be any real symmetric matrix. Now I would like to understand which kind of matrices B can be represented if A has rank M < N. If this matrix can be characterised for instance through their eigenvalue spectrum or other properties.







      linear-algebra abstract-algebra matrices eigenvalues-eigenvectors diagonalization






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      share|cite|improve this question











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      share|cite|improve this question










      asked Nov 29 at 10:06









      Nik

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