start-ver=1.4 cd-journal=joma no-vol=55 cd-vols= no-issue=1 article-no= start-page=191 end-page=200 dt-received= dt-revised= dt-accepted= dt-pub-year=2013 dt-pub=201301 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=ON HYPERBOLIC AREA OF THE MODULI OF Ɓ|ACUTE TRIANGLES en-subtitle= kn-subtitle= en-abstract= kn-abstract=A -acute triangle is a Euclidean triangle on the plane whose three angles are less than a given constant . In this note, we shall give an explicit formula computing the hyperbolic area A() of the moduli region of -acute triangles on the PoincarLe disk. It turns out that A() is a period in the sense of Kontsevich-Zagier if cot is a nonnegative algebraic number. en-copyright= kn-copyright= en-aut-name=KanesakaNaomi en-aut-sei=Kanesaka en-aut-mei=Naomi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=NakamuraHiroaki en-aut-sei=Nakamura en-aut-mei=Hiroaki kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= affil-num=1 en-affil= kn-affil=Department of Mathematics, Faculty of Science, Okayama University affil-num=2 en-affil= kn-affil=Department of Mathematics, Faculty of Science, Okayama University en-keyword=moduli space kn-keyword=moduli space en-keyword=Euclidean triangle kn-keyword=Euclidean triangle en-keyword=hyperbolic measure kn-keyword=hyperbolic measure END start-ver=1.4 cd-journal=joma no-vol=12 cd-vols= no-issue= article-no= start-page=123 end-page=133 dt-received= dt-revised= dt-accepted= dt-pub-year=2006 dt-pub=20060824 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Some classical views on the parameters of the Grothendieck-Teichm?eller group en-subtitle= kn-subtitle= en-abstract= kn-abstract=

We present two new formulas concerning behaviors of the standard parameters of the Grothendieck-Teichm?ller group GT , and discuss their relationships with classical mathematics. First, considering a non-Galois etale cover of P1 {0 1 infinity} of degree 4, we present a newtype equation satisfied by the Galois image in GT . Second, a certain equation in GL 2 (Z||Z2 ) satisfied by every element of GT is derived as an application of (profinite) free differential calculus.

en-copyright= kn-copyright= en-aut-name=NakamuraHiroaki en-aut-sei=Nakamura en-aut-mei=Hiroaki kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= affil-num=1 en-affil= kn-affil=Okayama University en-keyword=Grothendieck-Teichm?eller group kn-keyword=Grothendieck-Teichm?eller group en-keyword=Belyi function kn-keyword=Belyi function en-keyword=modular function kn-keyword=modular function END start-ver=1.4 cd-journal=joma no-vol=46 cd-vols= no-issue=1 article-no= start-page=39 end-page=76 dt-received= dt-revised= dt-accepted= dt-pub-year=2004 dt-pub=200401 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Eigenloci of 5 Point Configurations on the Riemann Sphere and the Grothendieck-Teichm・ler Group en-subtitle= kn-subtitle= en-abstract= kn-abstract= en-copyright= kn-copyright= en-aut-name=LochakPierre en-aut-sei=Lochak en-aut-mei=Pierre kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=NakamuraHiroaki en-aut-sei=Nakamura en-aut-mei=Hiroaki kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=SchnepsLeila en-aut-sei=Schneps en-aut-mei=Leila kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= affil-num=1 en-affil= kn-affil=175 rue de Chevaleret affil-num=2 en-affil= kn-affil=Okayama University affil-num=3 en-affil= kn-affil=175 rue de Chevaleret en-keyword=Riemann Spheres;Point Configurations;Grothendieck-Teichm?ler Group;Galois Group;Rational Numbers;Modular Group kn-keyword=Riemann Spheres;Point Configurations;Grothendieck-Teichm?ler Group;Galois Group;Rational Numbers;Modular Group END start-ver=1.4 cd-journal=joma no-vol=52 cd-vols= no-issue=1 article-no= start-page=61 end-page=63 dt-received= dt-revised= dt-accepted= dt-pub-year=2010 dt-pub=201001 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=BELYI FUNCTION ON X0(49) OF DEGREE 7 en-subtitle= kn-subtitle= en-abstract= kn-abstract= en-copyright= kn-copyright= en-aut-name=HoshinoKenji en-aut-sei=Hoshino en-aut-mei=Kenji kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=NakamuraHiroaki en-aut-sei=Nakamura en-aut-mei=Hiroaki kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= affil-num=1 en-affil= kn-affil=Department of Mathematics, Faculty of Science, Okayama University affil-num=2 en-affil= kn-affil=Department of Mathematics, Faculty of Science, Okayama University END