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Publications

In Journals


  1. Sachin Manjunath Naik and P. Sam Johnson, “Convergence of Complementable Operators”, Linear Algebra and its Applications (accepted for publication).
  2. Arup Majumdar and P. Sam Johnson, “The Moore-Penrose Inverses of Unbounded Closable Operators and the Cartesian Product of Closed Operators in Hilbert Spaces”, Linear and Multilinear Algebra (accepted for publication).
  3. Athira Satheesh K, P. Sam Johnson and K. Kamaraj, “Reverse Order Law for Moore-Penrose Inverse of Closed Operators and its Applications”, Indian Journal of Pure and Applied Mathematics (accepted for publication).
  4. Sachin Manjunath Naik and P. Sam Johnson, “Complementable Operators and their Schur Complements”, Indian Journal of Pure and Applied Mathematics (accepted for publication).
  5. Arup Majumdar and P. Sam Johnson, “A-Approximate Point Spectrum of A-Bounded Operators in Semi-Hilbertian Spaces”, Indian Journal of Pure and Applied Mathematics (accepted for publication).
  6. Shah Jahan and P. Sam Johnson, “Riesz Bases in Krein Spaces”, Indian Journal of Pure and Applied Mathematics (accepted for publication).
  7. Ayyanar K, P. Sam Johnson and A. Senthil Thilak, “Frame Scaling by Graphs”, Indian Journal of Pure and Applied Mathematics (accepted for publication).
  8. K. Mahesh Krishna and P. Sam Johnson, “Lipschitz p-Approximate Schauder Frames”, Kragujevac Journal of Mathematics, Volume 50, Number 2 (2026), pages 217-230 (to be published).
  9. Mohanarangan, H., P. Sam Johnson, and Harikrishanan P.K. “Direct Sum of Lower Semi-frames in Hilbert Spaces”, Gulf Journal of Mathematics, 19(2), 412-423, 2025.
  10. A. Senthil Thilak, Ayyanar K and P. Sam Johnson, ““On the Construction and Properties of Frames Using Incidence Matrix of Graphs and Their Spectra”, Proceedings of the Jangjeon Mathematical Society, 27 (2024), No. 4, pp. 549 - 564.
  11. Arup Majumdar, P. Sam Johnson and R. N. Mohapatra, “Hyers-Ulam Stability of Unbounded Closable Operators in Hilbert Spaces”, Mathematische Nachrichten, 297, No.10 (2024), 3887-3903.
  12. Shah Jahan and P. Sam Johnson, “Frame Operators for Frames in Krein Spaces”, European Journal of Mathematical Analysis, 4 (2024), Article 1 (10 pages).
  13. K. Mahesh Krishna and P. Sam Johnson, “Operator-Valued p-Approximate Schauder Frames”, J. Ramanujan Math. Soc. 38, No.3 (2023), 369-392.
  14. Athira Satheesh K, K. Kamaraj and P. Sam Johnson, “Algebraic Proofs of Characterizing Reverse Order Law for Closed Range Operators in Hilbert Spaces”, Eurasian Mathematical Journal, Volume 14, Number 3 (2023), 08-25.
  15. K. Mahesh Krishna and P. Sam Johnson, “Approximately Dual p-Approximate Schauder Frames”, Aust. J. Math. Anal. Appl. 20 (2023), No. 1, Article 22, 9 pages.
  16. K. Kamaraj, P. Sam Johnson and Athira Satheesh K, “Reverse Order Law for Generalized Inverses with Indefinite Hermitian Weights”, Filomat 37:3 (2023), 699-709.
  17. K. Mahesh Krishna and P. Sam Johnson, “Dilations of Linear Maps on Vector Spaces”, Operators and Matrices, Volume 16, Number 2 (2022), 465-477.
  18. P. Sam Johnson, “Closed EP and Hypo-EP Operators on Hilbert Spaces”, The Journal of Analysis (2022) 30:1377-1390.
  19. K. Mahesh Krishna and P. Sam Johnson, “Commutators Close to the Identity in Unital C*-Algebras”, Proceedings - Mathematical Sciences, Vol. 132, Issue 1, June 2022, Article 11, 08 pages.
  20. K. Kamaraj, P. Sam Johnson and Sachin Manjunath Naik, “Generalized Principal Pivot Transform and its Inheritance Properties”, The Journal of Analysis (2022) 30:1241-1256.
  21. Rashid A. and P. Sam Johnson, “P-Operators on Hilbert Spaces”, Palestine Journal of Mathematics, Vol.11 (3) 2022, 85-89.
  22. K. Mahesh Krishna and P. Sam Johnson, “Factorable Weak Operator-Valued Frames”, Annals of Functional Analysis, Vol. 13 (2022) No.1, Article 11, 36 pages.
  23. K. Mahesh Krishna and P. Sam Johnson, “The Noncommutative ℓ1−ℓ2 Inequality for Hilbert C*-Modules and the Exact Constant”, Nonlinear Functional Analysis and Applications, Volume 27, Issue 2, 249-259, 2022.
  24. K. Mahesh Krishna and P. Sam Johnson, “Expansion of Weak Reconstruction Sequences to Approximate Schauder Frames for Banach Spaces”, Asian-European Journal of Mathematics, Vol. 15, No. 3 (2022) 2250060 (6 pages)
  25. K. Mahesh Krishna and P. Sam Johnson, “Frames for Metric Spaces”, Results in Mathematics, Vol. 77, Issue 1, February 2022, Article 49, 30 pages.
  26. K. Mahesh Krishna, P. Sam Johnson and R. N. Mohapatra, “Multipliers for Operator-Valued Bessel Sequences and Generalized Hilbert-Schmidt Classes”, Journal of Applied Mathematics and Informatics, Vol. 40(2022), No. 1-2, pp. 153-171.
  27. K. Mahesh Krishna and P. Sam Johnson, “Dilation Theorem for p-Approximate Schauder Frames for Separable Banach Spaces”, Palestine Journal of Mathematics, Vol.11 (2) 2022, 384-394.
  28. K. Mahesh Krishna and P. Sam Johnson, “Perturbation of p-Approximate Schauder Frames for Separable Banach Spaces”, Poincare Journal of Analysis and Applications, Vol.8, No.1(II) (2021), 15-24.
  29. K. Mahesh Krishna and P. Sam Johnson, “New Identity on Parseval p-Approximate Schauder Frames and Applications”, Journal of Interdisciplinary Mathematics, Vol. 24 (2021), No. 7, 1751–1760.
  30. P. Sam Johnson, Vinoth A and K. Kamaraj, “Fuglede-Putnam Type Commutativity Theorems for EP Operators”, Malaya J. Mat. 9 (2021), No. 1, 709-714.
  31. K. Mahesh Krishna and P. Sam Johnson, “Towards Characterizations of Approximate Schauder Frame and Its Duals for Banach Spaces”, J. Pseudo-Differ. Oper. Appl., 12(1), 2021, Article 9, 13 pages.
  32. Athira Satheesh K, P. Sam Johnson and K. Kamaraj, “Estimates of Norms on Krein Spaces”, Aust. J. Math. Anal. Appl. 17 (2020), No. 2, Article 18, 10 pages.
  33. P. Sam Johnson, “On Semiclosed Operators with Closed Range”, Canad. J. Appl. Math. 2 (2020), No. 2, 18-22.
  34. P. Sam Johnson and S. Balaji, "Convergence of Operators with Closed Range", Khayyam J. Math. 5 (2019) No. 2, 132-138.
  35. Mahesh Krishna and P. Sam Johnson, "Quotient Operators and the Open Mapping Theorem", Filomat 32:18 (2018), 6221-6227.
  36. P. Sam Johnson and Vinoth A, "Product and Factorization of Hypo-EP Operators", Special Matrices 6 (2018), 376-382.
  37. B. Parvathalu and P. Sam Johnson, "Construction of Mercedes-Benz Frame in Rn", International Journal of Applied and Computational Mathematics, December 2017, Issue 1 Supplement, 511-519.
  38. G. Ramu and P. Sam Johnson, "Frames for Operators in Banach Spaces", Acta Mathematica Vietnamica, 42 (2017), 665-673.
  39. Vinoth A and P. Sam Johnson, "On Sum and Restriction of Hypo-EP Operators", Funct. Anal. Approx. Comput. 9 (1) (2017), 37-41.
  40. G. Ramu and P. Sam Johnson, "Frame Operators of K-frames", Boletin de la Sociedad Espanola de Matematica Aplicada, SeMA Journal (2016) 73 : 171-181.
  41. P. Sam Johnson and G. Ramu, "Class of Bounded Operators associated with an Atomic System", Tamkang Journal of Mathematics, Vol.46, No.1, 85-90, March 2015.
  42. P. Sam Johnson, “Multiplication Operators with Closed Range in Operator Algebras", Journal of Analysis and Number Theory, Vol. 1, No.1, 1-5, 2013.
  43. P. Sam Johnson and S. Balaji, “On Semiclosed Subspaces of Hilbert Spaces", International Journal of Pure and Applied Mathematics, Vol. 79, No. 2, 2012, 249-258.
  44. P. Sam Johnson and S. Balaji, “Hyers-Ulam Stability of Linear Operators in Frechet Spaces", Applied Mathematics and Information Sciences, Vol. 6, No.3, 525-528 (2012).
  45. P. Sam Johnson and S. Balaji, “On Linear Operators with Closed Range", Journal of Applied Mathematics and Bioinformatics, Vol.1, No.2, 2011, 175-182.
  46. P. Sam Johnson and C. Ganesa Moorthy, “Composition of Operators with Closed Range", The Journal of Analysis, 14(2006), 79-80.
  47. C. Ganesa Moorthy and P. Sam Johnson, “Composition of Closed Range Operators", The Journal of Analysis, 12(2004), 165-169.

In Conference Proceedings


  1. Ameya Vyas and P. Sam Johnson, “Anomaly Detection in Electric Powertrain System Software Behaviour", Published in: 14th International Conference on Computing Communication and Networking Technologies (ICCCNT), 06-08 July 2023, Delhi (Publisher: IEEE).
  2. Vinoth A and P. Sam Johnson, “Factorization of EP Operators in Krein Spaces", Mathematical Analysis and Computing, Springer Proceedings in Mathematics and Statistics, 344, pp. 359-364, 2021 (Proceedings of the International Conference on Mathematical Analysis and Computing held at SSN College of Engineering, Chennai on December 23-24, 2019).
  3. C. Ganesa Moorthy and P. Sam Johnson, “Closed Range - Multiplication Operators", Mathematical Analysis and Applications, Narosa Publishing House, pp 133-138, 2004 (Proceedings of the International Conference on Analysis and Discrete Structures held at Indian Institute of Technology, Kharagpur on December 22-24, 2002).

Papers Submitted


  1. Arup Majumdar and P. Sam Johnson, “Characterizations of Closed EP Operators on Hilbert Spaces”.
  2. Arup Majumdar and P. Sam Johnson, “A Formula of A-Spectral Radius for A1/2-Adjoint Operators on Semi-Hilbertian Spaces”.
  3. K. Mahesh Krishna, P. Sam Johnson and Harikrishnan Panackal, “Multipliers for Lipschitz p-Bessel Sequences in Metric Spaces”.
  4. Arup Majumdar, P. Sam Johnson and R. N. Mohapatra, “On the Generalized Cauchy Dual of Closed Operators in Hilbert Spaces”.