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Search Results: 1 - 10 of 1797 matches for " Shigefumi Mori "
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On Q-conic bundles
Shigefumi Mori,Yuri Prokhorov
Mathematics , 2006,
Abstract: A $\mathbb Q$-conic bundle is a proper morphism from a threefold with only terminal singularities to a normal surface such that fibers are connected and the anti-canonical divisor is relatively ample. We study the structure of $\mathbb Q$-conic bundles near their singular fibers. One corollary to our main results is that the base surface of every $\mathbb Q$-conic bundle has only Du Val singularities of type A (a positive solution of a conjecture by Iskovskikh). We obtain the complete classification of $\mathbb Q$-conic bundles under the additional assumption that the singular fiber is irreducible and the base surface is singular.
On Q-conic bundles, II
Shigefumi Mori,Yuri Prokhorov
Mathematics , 2007,
Abstract: A $\mathbb Q$-conic bundle germ is a proper morphism from a threefold with only terminal singularities to the germ $(Z \ni o)$ of a normal surface such that fibers are connected and the anti-canonical divisor is relatively ample. We obtain the complete classification of $\mathbb Q$-conic bundle germs when the base surface germ is singular. This is a generalization of our previous paper math/0603736, which further assumed that the fiber over $o$ is irreducible.
Threefold extremal contractions of type IA
Shigefumi Mori,Yuri Prokhorov
Mathematics , 2010, DOI: 10.1215/21562261-1214393
Abstract: Let $(X,C)$ be a germ of a threefold $X$ with terminal singularities along an irreducible reduced complete curve $C$ with a contraction $f: (X,C)\to (Z,o)$ such that $C=f^{-1}(o)_{\red}$ and $-K_X$ is ample. Assume that a general member $F\in |-K_X|$ meets $C$ only at one point $P$ and furthermore $(F,P)$ is Du Val of type A if index$(X,P)=4$. We classify all such germs in terms of a general member $H\in |O_X|$ containing $C$.
Multiple fibers of del Pezzo fibrations
Shigefumi Mori,Yuri Prokhorov
Mathematics , 2008,
Abstract: We prove that a terminal three-dimensional del Pezzo fibration has no fibers of multiplicity $\ge 6$. We also obtain a rough classification possible configurations of singular points on multiple fibers and give some examples.
On Q-conic bundles, III
Shigefumi Mori,Yuri Prokhorov
Mathematics , 2008,
Abstract: A Q-conic bundle germ is a proper morphism from a threefold with only terminal singularities to the germ $(Z \ni o)$ of a normal surface such that fibers are connected and the anti-canonical divisor is relatively ample. Building upon our previous paper [math/0603736], we prove the existence of a Du Val anti-canonical member under the assumption that the central fiber is irreducible.
Quotients by Groupoids
Sean Keel,Shigefumi Mori
Mathematics , 1995,
Abstract: We show that if a flat group scheme acts properly, with finite stabilizers, on an algebraic space, then a quotient exists as a separated algebraic space. More generally we show any flat groupid for which the family of stabilizers is finite has a uniform geometric, uniform categorical quotient in the category of algebraic spaces. Our argument is elementary and essentially self contained.
Threefold extremal contractions of types (IC) and (IIB)
Shigefumi Mori,Yuri Prokhorov
Mathematics , 2011, DOI: 10.1017/S0013091513000850
Abstract: Let $(X,C)$ be a germ of a threefold $X$ with terminal singularities along an irreducible reduced complete curve $C$ with a contraction $f: (X,C)\to (Z,o)$ such that $C=f^{-1}(o)_{red}$ and $-K_X$ is ample. Assume that $(X,C)$ contains a point of type (IC) or (IIB). We complete the classification of such germs in terms of a general member $H\in |\mathcal O_X|$ containing $C$.
q-Deformed Bi-Local Fields II
Haruki Toyoda,Shigefumi Naka
Symmetry, Integrability and Geometry : Methods and Applications , 2006,
Abstract: We study a way of q-deformation of the bi-local system, the two particle system bounded by a relativistic harmonic oscillator type of potential, from both points of view of mass spectra and the behavior of scattering amplitudes. In our formulation, the deformation is done so that P^2, the square of center of mass momentum, enters into the deformation parameters of relative coordinates. As a result, the wave equation of the bi-local system becomes nonlinear with respect to P^2; then, the propagator of the bi-local system suffers significant change so as to get a convergent self energy to the second order. The study is also made on the covariant q-deformation in four dimensional spacetime.
q-Deformed Bi-Local Fields II
Haruki Toyoda,Shigefumi Naka
Mathematics , 2006, DOI: 10.3842/SIGMA.2006.031
Abstract: We study a way of $q$-deformation of the bi-local system, the two particle system bounded by a relativistic harmonic oscillator type of potential, from both points of view of mass spectra and the behavior of scattering amplitudes. In our formulation, the deformation is done so that $P^2$, the square of center of mass momentum, enters into the deformation parameters of relative coordinates. As a result, the wave equation of the bi-local system becomes nonlinear with respect to $P^2$; then, the propagator of the bi-local system suffers significant change so as to get a convergent self energy to the second order. The study is also made on the covariant $q$-deformation in four dimensional spacetime.
Japanese Are Modest Even When They Are Winners: Competence Ratings of Winners and Losers in Social Comparison  [PDF]
Kazuo Mori, Hideko Mori
Psychology (PSYCH) , 2013, DOI: 10.4236/psych.2013.411119
Abstract:

Social comparison experiments in two different social conditions, competing between friends and between strangers, were carried out with 88 Japanese male undergraduates. Participants were asked to come to the laboratory in friend pairs to participate in the experiment. Two pairs were randomly combined for each experimental session. In the Between-Friends condition, one of the two pairs solved 20 anagrams competitively while the other pair observed them. In the Between-Strangers condition, one performer and one observer were randomly chosen in each pair and the performers solved anagram tasks competitively. As in our previous study, the anagram tasks were presented utilizing a presentation trick so that one performer-and-observer group viewed easier anagrams than the other group without their noticing the difference. As intended, those who viewed the easier anagrams outperformed the others, becoming winners in all sessions. No participants noticed the trick. After the task, all four participants rated the ability of the two performers including themselves. Their ability ratings showed that they tended to evaluate their own ability modestly. Even winners consistently rated themselves lower than the others rated them. Two possible explanations of why Japanese participants made such modest responses were presented and discussed.

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