Masami Sekizawa （関沢 正躬）


Published papers

  1. Oldřich Kowalski and Masami Sekizawa: Existence and classification of three-dimensional Lorentzian manifolds with prescribed distinct Ricci eigenvalues. J. Geom. Phys. 99 (2016), 232–238. DOI: 10.1016/j.geomphys.2015.10.009
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  2. Oldřich Kowalski and Masami Sekizawa: The Riemann extensions with cyclic parallel Ricci tensor, Math. Nachr. 287 (2014), no. 8-9, 955–961. DOI: 10.1002/mana.201200299
  3. Oldřich Kowalski and Masami Sekizawa: Diagonalization of three-dimensional pseudo-Riemannian metrics, J. Geom. Phys. 74 (2013), 251–255. DOI: 10.1016/j.geomphys.2013.08.010
    Manuscript: diagonal.pdf 103 kB (corrected minor misprints in Theorem B)
  4. Oldřich Kowalski and Masami Sekizawa: Almost Osserman structures on natural Riemann extensions, Differential Geom. Appl. Volume 31(2013), 140–149. DOI: 10.1016/j.difgeo.2012.10.007
  5. Oldřich Kowalski and Masami Sekizawa: Invariance of the naturally lifted metrics on linear frame bundles over affine manifolds, Publ. Math. Debrecen.81(2012), no. 1-2, 235–242. DOI: 10.5486/PMD.2012.5303
  6. Oldřich Kowalski and Masami Sekizawa: Curvatures of the diagonal lift from an affine manifold to the linear frame bundle, Cent. Eur. J. Math. 10(3)(2012), 837–843. DOI: 10.2478/s11533-012-0033-7
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  7. Takamichi Satoh and Masami Sekizawa: Curvatures of tangent hyperquadric bundles, Differential Geom. Appl. 29(2011), Suppl. 1, S255–S260. DOI: 10.1016/j.difgeo.2011.04.050
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  8. Oldřich Kowalski and Masami Sekizawa: On natural Riemann extensions, Publ. Math. Debrecen 78(2011), no. 3-4, 709–721. DOI: 10.5486/PMD.2011.4992
  9. Oldřich Kowalski and Masami Sekizawa: Natural lifts in Riemannian geometry, “Variations, Geometry and Physics” in honour of Demeter Krupka’s sixty-fifth birthday, O. Krupková and D. J. Saunders (Editors), Nova Science Publishers, New York (2009), pp. 189–209.
  10. Masami Sekizawa: On Riemannian geometry of orthonormal frame bundles, Note Mat. 28 (2008), [2009 on cover], suppl. 1, 383–394 (2009). ISBN: 978-88-548-2664-9.
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  11. Oldřich Kowalski and Masami Sekizawa: On Riemannian geometry of tangent sphere bundles with arbitrary constant radius, Arch. Math. (Brno), 44(2008), no. 5, 391–401.
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  12. Oldřich Kowalski and Masami Sekizawa: On the geometry of orthonormal frame bundles II, Ann. Global Anal. Geom. 33(2008), no. 4, 357–371.
  13. Oldřich Kowalski and Masami Sekizawa: On the geometry of orthonormal frame bundles, Math. Nachr. 281(2008), no. 12, 1799–1809. DOI: 10.1002/mana.200610715
  14. Oldřich Kowalski and Masami Sekizawa: Invariance of g-natural metrics on linear frame bundles, Arch. Math. (Brno), 44(2008), no. 2, 139–147.
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  15. Oldřich Kowalski and Masami Sekizawa: Invariance of g-natural metrics on tangent bundles, Differential Geometry and its Applications, Proc. Conf., in Honour of Leonhard Euler, Olomouc, August 2007, World Sci. Publ., Hackensack, NJ, 2008, pp. 171–181.
  16. Oldřich Kowalski and Masami Sekizawa: Hypersurfaces of type number 2 in the hyperbolic four-space and their extensions to Riemannian geometry, Non-Euclidean geometries, 407–426, Math. Appl. (N. Y.), 581, Springer, New York, 2006.
  17. Oldřich Kowalski and Masami Sekizawa: On curvatures of linear frame bundles with naturally lifted metrics, Rend. Semin. Mat. Univ. Politec. Torino 63(2005), no. 3, 283–295.
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  18. Vladimíra Hájková, Oldřich Kowalski and Masami Sekizawa: On three-dimensional hypersurfaces with type number two in H4 and S4 treated in intrinsic way, Rend. Circ. Mat. Palermo(2) Suppl. no. 72(2004), 107–126.
    Proceedings
  19. Oldřich Kowalski and Masami Sekizawa: On Riemannian manifolds whose tangent sphere bundles can have nonnegative sectional curvature, Univ. Iagel. Acta Math. no. 40(2002), 245–256.
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  20. Oldřich Kowalski, Masami Sekizawa and Zdeněk Vlašek: Can tangent sphere bundles over Riemannian manifolds have strictly positive sectional curvature? Global differential geometry: the mathematical legacy of Alfred Gray (Bilbao, 2000), 110–118, Contemp. Math., 288, Amer. Math. Soc., Providence, RI, 2001.
  21. Oldřich Kowalski and Masami Sekizawa: On the scalar curvature of tangent sphere bundles with arbitrary constant radius, Proceedings of the 4th Panhellenic Conference on Geometry (Patras, 1999). Bull. Greek Math. Soc. 44(2000), 17–30.
  22. Oldřich Kowalski and Masami Sekizawa: Geometry of tangent sphere bundles with arbitrary constant radius, Proceedings of the Symposium Contemporary Mathematics, N. Bokan (Ed.), Faculty of Mathematics, University of Belgrade, Belgrade, 2000, pp. 219–228.
  23. Norio Hashimoto and Masami Sekizawa: Three-dimensional conformally flat pseudo-symmetric spaces of constant type, Arch. Math. (Brno) 36(2000), no. 4, 279–286.
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  24. Oldřich Kowalski and Masami Sekizawa: On tangent sphere bundles with small or large constant radius, Special issue in memory of Alfred Gray (1939–1998), Ann. Global Anal. Geom. 18(2000), no. 3-4, 207–219.
  25. Oldřich Kowalski and Masami Sekizawa: Pseudo-symmetric Spaces of Constant Type in Dimension Three, Personal Note, Prague-Tokyo, 1998.
    Manuscript: pspn.pdf 163 kB
  26. Oldřich Kowalski and Masami Sekizawa: Pseudo-symmetric spaces of constant type in dimension three—non-elliptic spaces, Bull. Tokyo Gakugei Univ. (4) 50(1998), 1–28.
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  27. Oldřich Kowalski and Masami Sekizawa: Pseudo-symmetric spaces of constant type in dimension three—elliptic spaces, Rend. Mat. Appl. (7) 17(1997), no. 3, 477–512.
  28. Oldřich Kowalski and Masami Sekizawa: Riemannian 3-manifolds with c-conullity two, Boll. Un. Mat. Ital. B (7) 11(1997), no. 2, suppl., 161–184.
  29. Oldřich Kowalski and Masami Sekizawa: Three-dimensional Riemannian manifolds of c-conullity two, Chapter 11 of the book “Riemannian manifolds of conullity two” by E. Boeckx, O. Kowalski and L. Vanhecke; published by World Scientific, Singapore-New Jersey-London-Hong Kong, 1996.
  30. Oldřich Kowalski and Masami Sekizawa: Local isometry classes of Riemannian 3-manifolds with constant Ricci eigenvalues ρ1 = ρ2≠ρ3 > 0, Arch. Math. (Brno) 32(1996), no. 2, 137–145.
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  31. Jun-iti Inoguti and Masami Sekizawa: Symmetries which preserve the characteristic vector field of K-contact manifolds, Note Mat. 13(1993), no. 2, 229–236.
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  32. Masami Sekizawa: Curvatures of tangent bundles with Cheeger-Gromoll metric, Tokyo J. Math. 14(1991), no. 2, 407–417.
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  33. Oldřich Kowalski and Masami Sekizawa: Natural transformations of Riemannian metrics on manifolds to metrics on tangent bundles—A classification—, Bull. Tokyo Gakugei Univ. (4) 40(1988), 1–29.
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  34. Masami Sekizawa: Natural transformations of vector fields on manifolds to vector fields on tangent bundles, Tsukuba J. Math. 12(1988), no. 1, 115–128.
    Article
  35. Masami Sekizawa: Natural transformations of symmetric affine connections on manifolds to metrics on linear frame bundles: a classification, Monatsh. Math. 105(1988), no. 3, 229–243.
  36. Oldřich Kowalski and Masami Sekizawa: Natural transformations of Riemannian metrics on manifolds to metrics on linear frame bundles—a classification, Differential geometry and its applications (Brno, 1986), 149–178, Math. Appl. (East European Ser.), 27, Reidel, Publ. Comp., Dordrecht, 1987.
  37. Masami Sekizawa: Natural transformations of affine connections on manifolds to metrics on cotangent bundles, Proceedings of the 14th winter school on abstract analysis (Srni, 1986), Rend. Circ. Mat. Palermo (2) Suppl. No. 14(1987), 129–142.
    Proceedings
  38. Masami Sekizawa: Lifts of generalized symmetric spaces to tangent bundles, Časopis Pěst. Mat. 112(1987), no. 3, 261–268.
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  39. Oldřich Kowalski and Masami Sekizawa: On 3-dimensional Riemannian Σ-spaces, Monatsh. Math. 103(1987), no. 4, 303–320.
  40. 関沢正躬 (Masami Sekizawa): プラハの数学 (Mathematics in Prague), 数学 (Sugaku) 38(1986), no. 4, 354–359.
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  41. Masami Sekizawa: On complete lifts of reductive homogeneous spaces and generalized symmetric spaces, Czechoslovak Math. J. 36(111)(1986), no. 4, 516–534.
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  42. Masami Sekizawa: Umbilics of conformally flat submanifolds in Euclidean space, Tôhoku Math. J. (2) 32(1980), no. 1, 99–109.
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  43. Yôsuke Ogawa and Masami Sekizawa: Hypersurfaces immersed in a conformally flat Riemannian manifold, Natur. Sci. Rep. Ochanomizu Univ. 27(1976), no. 2, 77–87.
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  44. Masami Sekizawa: Completeness of the k-th nullity foliations, J. Differential Geometry 11(1976), no. 3, 461–465.
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  45. Shun-ichi Tachibana and Masami Sekizawa: On the k-th nullity space of the Riemannian curvature tensor, Tôhoku Math. J. (2) 27(1975), 25–30.
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  46. Shun-ichi Tachibana and Masami Sekizawa: On the k-th relative nullity space of a Riemannian manifold in EN, Tamkang J. Math. 5(1974), no. 1, 133–138.
  47. Masami Sekizawa: The nullity spaces of the conformal curvature tensor, J. Math. Soc. Japan 25(1973), 125–131.
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  48. Masami Sekizawa: A theorem on a manifold of constant φ-holomorphic sectional curvature, Tensor (N.S.) 22(1971), 151–154.
  49. Masami Sekizawa: On conformal Killing tensors of degree 2 in Kählerian spaces, TRU Math. 6(1970), 1–5.
  50. Masami Sekizawa: A note on the complete lift of Φ-tensors to a tangent bundle, TRU Math. 5(1969), 43–45.
  51. Masami Sekizawa: On extended almost analytic vector fields in tangent bundles of manifolds with a non-linear connection, TRU Math. 4(1968), 14–20.