Shouhei Ma

Publications (12)0 Total impact

• Article: Rationality of some tetragonal loci

  Shouhei Ma
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  ABSTRACT: We prove that the moduli space of tetragonal curves of genus g>6 is rational when g is congruent to 1, 2, 5, 6, 9, 10 modulo 12 and not equal to 9, 45.
  02/2013;
• Article: Rationality of the moduli spaces of Eisenstein K3 surfaces

  Shouhei Ma, Hisanori Ohashi, Shingo Taki
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  ABSTRACT: K3 surfaces with non-symplectic symmetry of order 3 are classified by open sets of twenty-four complex ball quotients associated to Eisenstein lattices. We show that twenty-two of those moduli spaces are rational.
  08/2012;
• Article: The rationality of the moduli spaces of trigonal curves

  Shouhei Ma
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  ABSTRACT: The moduli spaces of trigonal curves are proven to be rational when the genus is divisible by 4.
  07/2012;
• Source

  Available from: ArXiv

  Article: Rationality of fields of invariants for some representations of SL(2)\timesSL(2)

  Shouhei Ma
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  ABSTRACT: We prove that the quotient by SL(2)\timesSL(2) of the space of bidegree (a, b) curves on P^1\timesP^1 is rational when ab is even and a\not=b.
  02/2012;
• Source

  Available from: ArXiv

  Article: Rationality of the moduli spaces of 2-elementary K3 surfaces

  Shouhei Ma
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  ABSTRACT: K3 surfaces with non-symplectic involution are classified by open sets of seventy-five arithmetic quotients of type IV. We prove that those moduli spaces are rational except two classical cases.
  10/2011;
• Source

  Available from: ArXiv

  Article: The rationality of the moduli spaces of trigonal curves of odd genus

  Shouhei Ma
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  ABSTRACT: The moduli spaces of trigonal curves of odd genus $g>4$ are proven to be rational. Comment: 7 pages
  12/2010;
• Source

  Available from: ArXiv

  Article: The unirationality of the moduli spaces of 2-elementary K3 surfaces (with an Appendix by Ken-Ichi Yoshikawa)

  Shouhei Ma
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  ABSTRACT: We prove that the moduli spaces of K3 surfaces with non-symplectic involutions are unirational. As a by-product we describe configuration spaces of 4<d<9 points in the projective plane as arithmetic quotients of type IV.
  11/2010;
• Source

  Available from: ArXiv

  Article: Decompositions of Abelian surface and quadratic forms

  Shouhei Ma
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  ABSTRACT: When a complex Abelian surface can be decomposed into a product of two elliptic curves, how many decompositions does the Abelian surface admit ? We provide arithmetic formulae for the number of decompositions of a complex Abelian surface. Comment: 27 pages
  06/2009;
• Source

  Available from: ArXiv

  Article: On K3 surfaces which dominate Kummer surfaces

  Shouhei Ma
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  ABSTRACT: We study isogeny relations between K3 surfaces and Kummer surfaces. Specifically, we prove a Torelli-type theorem for the existence of rational maps from K3 surfaces to Kummer surfaces, and a Kummer sandwich theorem for K3 surfaces with Shioda-Inose structure.
  05/2009;
• Source

  Available from: ArXiv

  Article: On the 0-dimensional cusps of the Kahler moduli of a K3 surface

  Shouhei Ma
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  ABSTRACT: Let S be a projective K3 surface. It is proved that the 0-dimensional cusps of the Kahler moduli of S are in one-to-one correspondence with the twisted Fourier-Mukai partners of S. This leads to a counting formula for the 0-dimensional cusps of the Kahler moduli. Applications to rational maps between K3 surfaces with large Picard numbers are given. When the Picard number of S is 1, the bijective correspondence is calculated explicitly. Comment: 24pages
  12/2008;
• Source

  Available from: ArXiv

  Article: Twisted Fourier-Mukai number of a K3 surface

  Shouhei Ma
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  ABSTRACT: We give a counting formula for the twisted Fourier-Mukai partners of a projective K3 surface. As an application, we describe all twisted Fourier-Mukai partners of a projective K3 surface of Picard number 1.
  05/2008;
• Source

  Available from: ArXiv

  Article: Fourier-Mukai partners of a K3 surface and the cusps of its Kahler moduli

  Shouhei Ma
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  ABSTRACT: Using lattice theory, we establish a one-to-one correspondence between the set of Fourier-Mukai partners of a projective $K3$ surface and the set of 0-dimensional standard cusps of its Kahler moduli. We also study the relation between twisted Fourier-Mukai partners and general 0-dimensional cusps, and the relation between Fourier-Mukai partners with elliptic fibrations and certain 1-dimensional cusps.
  05/2008;