Faculty | Department of Electrical and Electronic Engineering Course of Electricity， Electronics and Communications |
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Position | Professor |

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Birthday |

Last Updated :2020/07/09

- Tokyo University of Science, Graduate School of Science

- 2016 04 - 現在, Toyo University, Faculty of Science and Engineering
- 2011 04 - 2016 03 , Toyo University, Faculty of Science and Engineering
- 2006 - 2007 , Kanagawa University, Faculty of Engineering
- 2004 - 2006 , Kanagawa University, Faculty of Engineering
- 2000 - 2004 , Kanagawa University, Faculty of Engineering

- Natural sciences, Basic analysis

- Operator Theory

- The Ando-Hiai inequalities for the solution of the generalized Karcher equation and related results, YAMAZAKI TAKEAKI, Journal of Mathematical Analysis and Applications, Journal of Mathematical Analysis and Applications, 479, (1) 531 - 545, 11 , Refereed
- UPPER AND LOWER BOUNDS, AND OPERATOR MONOTONICITY OF AN EXTENSION OF THE PETZ-HASEGAWA FUNCTION, Takayuki Furuta, Masatoshi Ito, Takeaki Yamazaki, Masahiro Yanagida, MATHEMATICAL INEQUALITIES & APPLICATIONS, MATHEMATICAL INEQUALITIES & APPLICATIONS, 21, (1) 155 - 164, 01 , Refereed
- Some properties of weighted operator means and characterizations of interpolational means, Yoichi Udagawa, Takeaki Yamazaki, Masahiro Yanagida, LINEAR ALGEBRA AND ITS APPLICATIONS, LINEAR ALGEBRA AND ITS APPLICATIONS, 517, 217 - 234, 03 , Refereed
- Some norm inequalities for matrix means, Rajendra Bhatia, Yongdo Lim, Takeaki Yamazaki, LINEAR ALGEBRA AND ITS APPLICATIONS, LINEAR ALGEBRA AND ITS APPLICATIONS, 501, 112 - 122, 07 , Refereed
- Equivalence relations among some inequalities on operator means, Wada, Shuhei, Yamazaki, Takeaki, Nihonkai Mathematical Journal, Nihonkai Mathematical Journal, 27, (1-2) 1 - 15, 06 , Refereed
- Norm inequalities for matrix geometric means of positive definite matrices, Jun Ichi Fujii, Yuki Seo, Takeaki Yamazaki, LINEAR & MULTILINEAR ALGEBRA, LINEAR & MULTILINEAR ALGEBRA, 64, (3) 512 - 526, 03 , Refereed
- On a family of operator means involving the power difference means, Yoichi Udagawa, Shuhei Wada, Takeaki Yamazaki, Masahiro Yanagida, LINEAR ALGEBRA AND ITS APPLICATIONS, LINEAR ALGEBRA AND ITS APPLICATIONS, 485, 124 - 131, 11 , Refereed
- Some generalized numerical radius inequalities for Hilbert space operators, Mostafa Sattari, Mohammad Sal Moslehian, Takeaki Yamazaki, LINEAR ALGEBRA AND ITS APPLICATIONS, LINEAR ALGEBRA AND ITS APPLICATIONS, 470, 216 - 227, 04 , Refereed
- Cartesian decomposition and numerical radius inequalities, Fuad Kittaneh, Mohammad Sal Moslehian, Takeaki Yamazaki, LINEAR ALGEBRA AND ITS APPLICATIONS, LINEAR ALGEBRA AND ITS APPLICATIONS, 471, 46 - 53, 04 , Refereed
- A converse of Loewner-Heinz inequality and applications to operator means, Mitsuru Uchiyama, Takeaki Yamazaki, JOURNAL OF MATHEMATICAL ANALYSIS AND APPLICATIONS, JOURNAL OF MATHEMATICAL ANALYSIS AND APPLICATIONS, 413, (1) 422 - 429, 05
- An elementary proof of arithmetic-geometric mean inequality of the weighted Riemannian mean of positive definite matrices, Takeaki Yamazaki, LINEAR ALGEBRA AND ITS APPLICATIONS, LINEAR ALGEBRA AND ITS APPLICATIONS, 438, (4) 1564 - 1569, 02
- THE RIEMANNIAN MEAN AND MATRIX INEQUALITIES RELATED TO THE ANDO-HIAI INEQUALITY AND CHAOTIC ORDER, Takeaki Yamazaki, OPERATORS AND MATRICES, OPERATORS AND MATRICES, 6, (3) 577 - 588, 09
- Multi-variable weighted geometric means of positive definite matrices, Hosoo Lee, Yongdo Lim, Takeaki Yamazaki, LINEAR ALGEBRA AND ITS APPLICATIONS, LINEAR ALGEBRA AND ITS APPLICATIONS, 435, (2) 307 - 322, 07
- On an elementary operator with w-hyponormal operator entries, M. Cho, S. V. Djordjevic, B. P. Duggal, T. Yamazaki, LINEAR ALGEBRA AND ITS APPLICATIONS, LINEAR ALGEBRA AND ITS APPLICATIONS, 433, (11-12) 2070 - 2079, 12
- Weighted geometric mean of n-operators with n-parameters, Changdo Jung, Hosoo Lee, Yongdo Lim, Takeaki Yamazaki, LINEAR ALGEBRA AND ITS APPLICATIONS, LINEAR ALGEBRA AND ITS APPLICATIONS, 432, (6) 1515 - 1530, 03
- On a new construction of geometric mean of n-operators, Changdo Jung, Hosoo Lee, Takeaki Yamazaki, LINEAR ALGEBRA AND ITS APPLICATIONS, LINEAR ALGEBRA AND ITS APPLICATIONS, 431, (9) 1477 - 1488, 10
- ON A GEOMETRIC PROPERTY OF POSITIVE DEFINITE MATRICES CONE, Masatoshi Ito, Yuki Seo, Takeaki Yamazaki, Masahiro Yanagida, BANACH JOURNAL OF MATHEMATICAL ANALYSIS, BANACH JOURNAL OF MATHEMATICAL ANALYSIS, 3, (2) 64 - 76
- A remark on support of the principal function for class a operators, Muneo Cho, Mariko Giga, Tadasi Huruya, Takeaki Yamazaki, INTEGRAL EQUATIONS AND OPERATOR THEORY, INTEGRAL EQUATIONS AND OPERATOR THEORY, 57, (3) 303 - 308, 03
- A remark on support of the principal function for class a operators, Muneo Cho, Mariko Giga, Tadasi Huruya, Takeaki Yamazaki, INTEGRAL EQUATIONS AND OPERATOR THEORY, INTEGRAL EQUATIONS AND OPERATOR THEORY, 57, (3) 303 - 308, 03
- An extension of Kantorovich inequality to n-operators via the geometric mean by Ando-Li-Mathias, Takeaki Yamazaki, LINEAR ALGEBRA AND ITS APPLICATIONS, LINEAR ALGEBRA AND ITS APPLICATIONS, 416, (2-3) 688 - 695, 07
- An operator transform from class A to the class of hyponormal operators and its application, M Cho, T Yamazaki, INTEGRAL EQUATIONS AND OPERATOR THEORY, INTEGRAL EQUATIONS AND OPERATOR THEORY, 53, (4) 497 - 508, 12
- The iterated Aluthge transforms of a 2-by-2 matrix converge, T Ando, T Yamazaki, LINEAR ALGEBRA AND ITS APPLICATIONS, LINEAR ALGEBRA AND ITS APPLICATIONS, 375, 299 - 309, 12
- On generalized numerical range of the Aluthge transformation, M Ito, H Nakazato, K Okubo, T Yamazaki, LINEAR ALGEBRA AND ITS APPLICATIONS, LINEAR ALGEBRA AND ITS APPLICATIONS, 370, 147 - 161, 09
- On generalized numerical range of the Aluthge transformation, M Ito, H Nakazato, K Okubo, T Yamazaki, LINEAR ALGEBRA AND ITS APPLICATIONS, LINEAR ALGEBRA AND ITS APPLICATIONS, 370, 147 - 161, 09
- On numerical range of the Aluthge transformation, T Yamazaki, LINEAR ALGEBRA AND ITS APPLICATIONS, LINEAR ALGEBRA AND ITS APPLICATIONS, 341, 111 - 117, 01

- On the operator equation AB=zBA, Scientiae Mathematicae Japonicae, 2009
- A remark on support of the principal function for class a operators, Muneo Cho, Mariko Giga, Tadasi Huruya, Takeaki Yamazaki, INTEGRAL EQUATIONS AND OPERATOR THEORY, 57, (3) 303 - 308, 2007 03 , Let T = U vertical bar T vertical bar be an invertible class A operator such that [ T*, T] is an element of C-1. Then we show that supp( g(T)) subset of sigma( T), where g(T) is the principal function of T. Moreover, we show that if T is pure, then supp( g(T)) = sigma( T).
- On upper and lower bounds of the numerical radius and an equality condition, Studia Mathematica, 2007
- An extension of Kantorovich inequality to n-operators via the geometric mean by Ando-Li-Mathias, Linear Algebra and its Applications, 2006
- On conparisons of norms and the numerical ranges of an operator with its generalized Aluthge transformation, Scientiae Mathematicae Japonicae, 2005
- An operator transform from class A to the class of hyponormal operators and its application, Integral Equations Operator Theory, Vol. 53 (2005)., 2005
- On numerical range and norm of the generalized Aluthge transform, 2005
- On single-valued extension property and Bishop's one of class A operators, 2004
- On the polar decomposition of the product of two operators and its applications, Integral Equations Operator Theory, vol. 49, 2004
- On the polar decomposition of the Aluthge transformation and related results, J. Operator Theory, Vol. 51, 2004
- Mosaic and principal functions of log-hyponormal operators, 2004
- Weakly chaotic order and its application to class A operators, 2004
- On the polar decomposition of the product of operators, 2004
- On some norm inequalities associated with the variance of an operator, 2004
- On numerical range and norm of the generalized Aluthge transform, 2004
- The iterated Aluthge transforms of a 2-by-2 matrix converge, T Ando, T Yamazaki, LINEAR ALGEBRA AND ITS APPLICATIONS, 375, 2003 12 , The Aluthge transform of a square complex matrix T with polar representation T = U\T\ is by definition Delta(T) equivalent to \T\U-1/2\T\(1/2). It has been conjectured that the iterates Delta(T), Delta(Delta (T)), . . . converge. We prove this when T is a 2-by-2 matrix. (C) 2003 Elsevier Inc. All rights reserved.
- On generalized numerical range of the Aluthge transformation, M Ito, H Nakazato, K Okubo, T Yamazaki, LINEAR ALGEBRA AND ITS APPLICATIONS, 370, 2003 09 , In this paper the authors show that the Aluthge transformation (T) over tilde of a matrix T and a polynomial f satisfy the inclusion relation W-C (f((T) over tilde)) subset of W-C (f(T)) for the generalized numerical range if C is a Hermitian matrix or a rank-one matrix. (C) 2003 Elsevier Inc. All rights reserved.
- On generalized numerical range of the Aluthge transformation, 2003
- The polar decomposition of the operators and its applications to binormal and centered operators, 2003
- Operator inequalities derived from new formula that Specht ratioS(1) can be expressed by generalized Kantorovich constant K(p): S(1)=e^K'(1), 2003
- An operator transform from class A to the class of hyponormal operators, 2003
- Relations among operator inequalities following from log Ageq log B, 2003
- Relations among operator orders and operator inequalities, 2003
- An operator transform from class A to the class of hyponormal operators and its application, 2003
- An operator transform from class A to the class of hyponormal operators, 2003
- On approximate point joint spectrum of p-hyponormal and log-hyponormal operators, Comment. Math. Prace Mat., 43(2003), 2003
- Relations between two operator inequalities and their applications to paranormal operators, Acta Sci. Math. (Szeged), 69(2003), 2003
- Generalizations of results on relations between Furuta-type inequalities, Acta Math Sci. (Szeged), 69(2003), 2003
- On generalized numerical range of the Aluthge transformation, Linear Algebra Appl., 370(2003), 2003
- On the polar decompositions of Aluthge transformation and powers of operators, 2002
- Generalizations of results on relations between Furuta-type inequalities, 2002
- Properties of Aluthge transformation on operator norms, The 6th workshop on numerical range and numerical radius, Auburn University, 2002
- Relations between two Furuta-type inequalities, The 10th ILAS conference, Auburn University, 2002
- On binormality of the Aluthge transformation, 2002
- On a relation between the polar decomposition and commutativity of operators, 2002
- Relations between two inequalities (B^fracr2A^pB^fracr2)^fracrp+rgeq B^r and A^pgeq (A^fracp2A^rA^fracp2)^fracpp+r and their applications, Integral Equations Operator Theory, 44(2002)., 2002
- Characterizations of log Ageq log B and normaloid operators via Heinz inequality, Integral Equations Operator Theory, 43(2002), 2002
- An expression of spectral radius via Aluthge transformation, Proc. Amer. Math. Soc., 130(2002), 2002
- On numerical range of the Aluthge transformation, Linear Algebra Appl.,341(2002), 2002
- Order prederving operator inequalities associated with Kantorovich inequality and Specht's theorem, 2001
- Several properties of Aluthge transformation, 2001
- Several properties of Aluthge transformation, 2001
- Order preserving operator inequalities and Aluthge transformation, KOTAC 2001 Operator theory and its applications, Cheju National University, 2001
- On numerical range of the Aluthge transformation, 2001
- Relations between two operator inequalities and their applications to paranormal operators, 2001
- Relations between two inequalities (B^fracr2A^pB^fracr2)^fracrp+r ge B^r and A^p ge (A^fracp2B^rA^fracp2)^fracpp+r and their applications, 2001
- Relations between two operator inequalities and their applications to paranormal operators, 2001
- On numerical range and polar decomposition of the Aluthge transformation, 2001
- Relations between two inequalities (B^fracr2A^pB^fracr2)^fracrp+r ge B^r and A^p ge (A^fracp2B^rA^fracp2)^fracpp+r and their applications, 2001
- parallelism between Aluthge transformation and powers of operators, Acta Sci. Math. (Szeged),67(2001), 2001
- Several properties on Aluthge transformation, 2001
- Characterizations of chaoric order associated with Kantorovich inequality, 2000
- a characterization of log-hyponormal operators via p-paranormality, Scientiae Mathematicae vol.3, 2000
- An extension of Specht's theorem via Kantorovich inequality and related results, T Yamazaki, MATHEMATICAL INEQUALITIES & APPLICATIONS, 3, (1) 89 - 96, 2000 01 , In this paper, we shall show the following result. "If MI greater than or equal to A greater than or equal to ml > 0 with M > m > 0, then K+(m(r), M-r, p/r)(1/p)(A(r)x, x)(1/r) greater than or equal to (A(p)x, x)(1/p) for p > r > 0, where K+(m, M, p) = (p-1)(p-1)/p(p) (M-p-m(p))(p)/(M-m)(mM(p)-Mm(p))(p-1)". This result is an extension of Specht's theorem [6] as a converse of the arithmetic-geometric mean inequality. "If x(1), x(2), ..., x(n) is an element of [m, M] with M > m > 0, then M-h (n)root x(1)x(2)...x(n) greater than or equal to x(1)+x(2)+...+x(n)/n where h = M/m > 1 and M-h = h(1/h-1)/e log h(1/h-1)". Secondly, we shall show an application for operator inequalities, that is, "if A greater than or equal to B greater than or equal to 0 satisfying MI greater than or equal to B greater than or equal to ml > 0 with M > m > 0, then A(p) - B-p greater than or equal to -(mM(p)-Mm(p))/M-m {K+(m,M,p)(1/p-1)-1} for p > 1.".
- Further extensions of characterizations of chaotic order associated with Kantorovich type inequalities, Scientiae Mathematicae.Vol.3, 2000
- Further extension of characterizations of chaotic order associated with Kantorovich type inequalities, 2000
- Extensions of paranormal operators and their properties, 2000
- A further generalization of paranormal operators, Scientiae Mathematicae vol.3, 2000
- Further extensions of characterizations of chaotic order associated with Kantorovich type inequalities, 2000
- Priperties on several classis including log-hyponormal operators, 2000
- On powers of p-hyponormal and log-hyponormal operators, 2000
- Order prederving operator inequalities associated with Kantorovich inequality and Specht's ratio, 2000
- Order prederving operator inequalities and related results, 2000
- On powers of class A(k) operators including p-hyponormal and log-hyponormal operators, 2000
- Recent applications of order preserving operator inequalities, 2000
- On powers of class A(k) operators including p-hyponormal and log-hyponormal operators, 2000
- Further extensions of characterizations of chaotic order associated with Kantorovich type inequalities, 2000
- Extensions of paranormal operators and their properties, 2000
- On powers of class A(k) operators including p-hyponormal and log-hyponormal operators,, 2000
- Extensions of paranormal operators and their properties,, 2000
- Further extensions of characterizations of chaotic order associated with Kantorovich type inequalities,, 2000
- Further characterizations of chaotic order via Specht's ratio, Math.Inequal.Appl., 2000
- Order prederving operator inequalities associated with Kantorovich inequality and Specht's ratio, 2000
- Order prederving operator inequalities associated with Kantorovich inequality and Specht's ratio, 2000
- Several properties on Aluthge transformation, 2000
- Order prederving operator inequalities and related results, 2000
- Several properties of Aluthge transformation, 2000
- On powers of class A( ) operators including p-hyponormal and log-hyponormal Operators, Mathematical Inequalities and Applications vol.3, 2000
- Simplified proof of characterization of chaotic order via Specht's ratio, Scientiae Mathematicae vol.2, 1999
- Extensions of teh results on p-hyponormal and log-hyponormal operators by Aluthge and Wang, SUT Journal of Mathematics vol.35, 1999
- Simplified proof of Tanahashi's result on the best possibility of generalized Furuta inequality, Mathematical Inequalities and Applications vol.2, 1999
- Characterizations of chaotic Order assosciated with Kantorovich inequality, Scientiae Mathematicae vol.2, 1999
- A subclass of paranormal including class of log-hyponormal and several related classes, 1999
- Characterizations of chaotic order associated with Kantorovich inequality, 1999
- Characterizations of chaoric order associated with Kantorovich inequality, 1999
- A subclass of paranormal including class of log-hyponormal and several related classes, 1999
- Characterizations of chaoric order associated with Kantorovich inequality, 1999
- A simplified proof of Tanahashi's result on the best possibility of generalized Furuta inequality, 1999
- Order preserving operator inequalities and their recent applications, 1999
- Extensions of the results on p-hyponormal and log-hyponormal operators by Aluthge and Wang, 1999
- Properties on several classes including log-hyponormal operators, 1999
- Further extensions of characterizations of chaotic order associated with Kantorovich type inequalities, 1999
- On powers of p-hyponormal and log-hyponormal operators, 1999
- An extension of order preserving operator inequalities, 1998
- Generalized operator functions implying order preserving operator inequalities, 1998
- Equivalence relations among Furuta-type inequalities with negative pwoers, Scientiae Mathematicae vol.1, 1998
- A subclass of paranormal operators including class of log-hyponormal and several related classes, Scientiae Mathematicae vol.1, 1998
- On order preserving inequalities with negative powers and a related conjecture, 1998
- Order preserving operator inequalities via Furuta inequality, Mathematica Japonica vol.48, 1998
- Operator functions implying generalized Furuta inezuality, Mathematical Inequalities and Applications vol.1, 1998
- A subclass of paranormal including class of log-hyponormal, 1998
- On a conjecture related to Furuta-type inequalities with negative powers, Nihonkai Mathematical Journal vol.9, 1998
- Generalized operator functions implying order preserving operator inequalities, 1998
- Order preserving operator inequalities via Furuta inequality, 1998
- Order preserving inequality associated with H"older-McCarthy and Kantorovich inequalities, 1998
- Equivalence relations among order preserving operator inequalities and a related open problem, 1998
- A conjecture on order preserving operator inequalities and related equivalence relations, 1998
- Generalized operator functions implying order preserving inequalities, 1998
- On order preserving inequalities with negative powers and a related conjecture, 1998
- A subclass of paranormal including class of log-hyponormal, 1998
- Order preserving inequality associated with H"older-McCarthy and Kantorovich inequalities, 1998
- A subclass of paranomal including class of log-hyponormal and severalrelated classes, 1998
- A characterization of chaotic order associated with Kantorovich inequality, 1998
- Characterizations of chaotic order associated with Kantorovich inequality, 1998
- A subclass of paranormal including class of log-hyponormal and several related classes, 1998
- Characterizations of chaotic order associated with Kantorovich inequality, 1998
- A subclass of paranormal including class of log-hyponormal and several related class, 1998
- Order preserving operator inequalities via Furuta inequality, 1997
- Operator functions implying order preserving inequalities,, 1997
- An order preserving operator inequality, 1997
- Generalized operator functions implying order preserving operator inequalities, 1997
- An extension of order preserving operator inequalities, 1997
- Equivalence relations among order preserving operator inequalities and a related open problem, 1997
- Generalized operator functions implying order preserving operator inequalities, 1997

- Power monotonicity for a path of operator means, YAMAZAKI TAKEAKI, International conference on Matrix Theory and Applications, 2019 05 24 , Invited
- Generalized Karcher equation, operator entropy and the Ando-Hiai ineuqlaity, YAMAZAKI TAKEAKI, Mathematical inequalities and Applications Conference 2018, 2018 07 06
- Generalized Karcher equations, operator entropies, and extensions, YAMAZAKI TAKEAKI, 2017 Korea-China International Conference on Matrix Theory with Applications, 2017 12 15 , Invited
- Properties of weighted operator means via generalized relative operator entropy, YAMAZAKI TAKEAKI, ILAS 2017, 2017 07 24 , Invited
- Some norm inequality for matrix means, YAMAZAKI TAKEAKI, YT004484, 2017 03 25
- Some norm inequalities for matrix means, YAMAZAKI TAKEAKI, MATRIX THEORY AND RELATED TOPICS, 2016 12 29 , Invited
- Some norm inequalities for matrix means, YAMAZAKI TAKEAKI, 2016 11 10
- Some recent topics on operator means, YAMAZAKI TAKEAKI, YT004484, 2016 09 03 , Invited
- Characterizations of the interpolational means and an application, YAMAZAKI TAKEAKI, 20th ILAS Conference, 2016 07 13 , Invited
- On interpolational means and an application, YAMAZAKI TAKEAKI, 2016 International workshop on matrix inequalities and matrix equations, 2016 06 10 , Invited
- Research of weighted operator means from two points of view, YAMAZAKI TAKEAKI, 2015 11 10
- On properties of weighted operator means due to Palfia and Petz, YAMAZAKI TAKEAKI, 2015 10 25 , Invited
- Some properties of weighted operator means due to Palfia and Petz, UDAGAWA YOICHI, YAMAZAKI TAKEAKI, YANAGIDA MASAHIRO, 2015 09 15
- Some properties of weighted operator means due to Palfia and Petz, YAMAZAKI TAKEAKI, Workshop on Quantum Information Theory and Related Topics, 2015 09 01 , Invited
- Some operator inequalities on operator means, YAMAZAKI TAKEAKI, Workshop on function spaces, harmonic analysis and related topics, 2015 04 27
- Equivalence relations among some inequalities on operator means, YAMAZAKI TAKEAKI, WADA SHUHEI, 2014 11 27
- A converse of Loewner-Heinz inequality and applications to operator means, YAMAZAKI TAKEAKI, 19th ILAS Conference, 2014 08 09
- Generalized Ando-Hiai inequality for matrix power mean, YAMAZAKI TAKEAKI, 2014 03 18
- On geometric mean of n-matrices and related results, YAMAZAKI TAKEAKI, The 7th Seminar on Linear Algebra and its Applications, 2014 02 26 , Invited
- Operator inequality and Operator mean, YAMAZAKI TAKEAKI, Mathematical Society of Japan, 2013 09 27 , Invited