$f,g$ 2 linearly independent weight 12 entire modular form give rise to isomorphism between $SL_2(Z)backslash...












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Let $M_{12}$ be weight 12(integral weighted) entire modular form(i.e. holomorphic at cusps). So over $dim_C(M_{12})=2$. Now pick out any $f,gin M_{12}$ linearly independent.



$textbf{Q:}$ The book says $[f,g]:SL_2(Z)backslash Hto CP_1$ is isomorphism where $H$ is the upper half plane union all cusps. Does the book mean identify $SL_2(Z)backslash H$ not as an orbifold rather than simply a sphere without orbifold structure?(I could not see why this has to be biholomorphic if it is equipped with orbifold structure as there will be locally branched covering.) I can see this is obviously bijection but I do not see this as homeomorphism.



Ref. Zagier 1-2-3 Modular Forms pg 11 Cor 2.










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  • I think Zagier is just being imprecise. On p. 9, he remarks that the two elliptic points become singularities on $overline{Gamma(1) backslash mathfrak{h}}$, and since $mathbb{P}^1(mathbb{C})$ is nonsingular this means they can't be isomorphic. What he probably actually means is that once we resolve these singularities, the resulting nonsingular Riemann surface is isomorphic to $mathbb{P}^1(mathbb{C})$. One can resolve the singularities by defining specific charts that take into account these stabilizers: this is done for instance in $S2.2$ of Diamond and Shurman or $S1.8$ of Miyake.
    – André 3000
    Nov 22 '18 at 0:45
















1














Let $M_{12}$ be weight 12(integral weighted) entire modular form(i.e. holomorphic at cusps). So over $dim_C(M_{12})=2$. Now pick out any $f,gin M_{12}$ linearly independent.



$textbf{Q:}$ The book says $[f,g]:SL_2(Z)backslash Hto CP_1$ is isomorphism where $H$ is the upper half plane union all cusps. Does the book mean identify $SL_2(Z)backslash H$ not as an orbifold rather than simply a sphere without orbifold structure?(I could not see why this has to be biholomorphic if it is equipped with orbifold structure as there will be locally branched covering.) I can see this is obviously bijection but I do not see this as homeomorphism.



Ref. Zagier 1-2-3 Modular Forms pg 11 Cor 2.










share|cite|improve this question






















  • I think Zagier is just being imprecise. On p. 9, he remarks that the two elliptic points become singularities on $overline{Gamma(1) backslash mathfrak{h}}$, and since $mathbb{P}^1(mathbb{C})$ is nonsingular this means they can't be isomorphic. What he probably actually means is that once we resolve these singularities, the resulting nonsingular Riemann surface is isomorphic to $mathbb{P}^1(mathbb{C})$. One can resolve the singularities by defining specific charts that take into account these stabilizers: this is done for instance in $S2.2$ of Diamond and Shurman or $S1.8$ of Miyake.
    – André 3000
    Nov 22 '18 at 0:45














1












1








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0





Let $M_{12}$ be weight 12(integral weighted) entire modular form(i.e. holomorphic at cusps). So over $dim_C(M_{12})=2$. Now pick out any $f,gin M_{12}$ linearly independent.



$textbf{Q:}$ The book says $[f,g]:SL_2(Z)backslash Hto CP_1$ is isomorphism where $H$ is the upper half plane union all cusps. Does the book mean identify $SL_2(Z)backslash H$ not as an orbifold rather than simply a sphere without orbifold structure?(I could not see why this has to be biholomorphic if it is equipped with orbifold structure as there will be locally branched covering.) I can see this is obviously bijection but I do not see this as homeomorphism.



Ref. Zagier 1-2-3 Modular Forms pg 11 Cor 2.










share|cite|improve this question













Let $M_{12}$ be weight 12(integral weighted) entire modular form(i.e. holomorphic at cusps). So over $dim_C(M_{12})=2$. Now pick out any $f,gin M_{12}$ linearly independent.



$textbf{Q:}$ The book says $[f,g]:SL_2(Z)backslash Hto CP_1$ is isomorphism where $H$ is the upper half plane union all cusps. Does the book mean identify $SL_2(Z)backslash H$ not as an orbifold rather than simply a sphere without orbifold structure?(I could not see why this has to be biholomorphic if it is equipped with orbifold structure as there will be locally branched covering.) I can see this is obviously bijection but I do not see this as homeomorphism.



Ref. Zagier 1-2-3 Modular Forms pg 11 Cor 2.







complex-analysis algebraic-geometry






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asked Nov 21 '18 at 1:36









user45765

2,5952722




2,5952722












  • I think Zagier is just being imprecise. On p. 9, he remarks that the two elliptic points become singularities on $overline{Gamma(1) backslash mathfrak{h}}$, and since $mathbb{P}^1(mathbb{C})$ is nonsingular this means they can't be isomorphic. What he probably actually means is that once we resolve these singularities, the resulting nonsingular Riemann surface is isomorphic to $mathbb{P}^1(mathbb{C})$. One can resolve the singularities by defining specific charts that take into account these stabilizers: this is done for instance in $S2.2$ of Diamond and Shurman or $S1.8$ of Miyake.
    – André 3000
    Nov 22 '18 at 0:45


















  • I think Zagier is just being imprecise. On p. 9, he remarks that the two elliptic points become singularities on $overline{Gamma(1) backslash mathfrak{h}}$, and since $mathbb{P}^1(mathbb{C})$ is nonsingular this means they can't be isomorphic. What he probably actually means is that once we resolve these singularities, the resulting nonsingular Riemann surface is isomorphic to $mathbb{P}^1(mathbb{C})$. One can resolve the singularities by defining specific charts that take into account these stabilizers: this is done for instance in $S2.2$ of Diamond and Shurman or $S1.8$ of Miyake.
    – André 3000
    Nov 22 '18 at 0:45
















I think Zagier is just being imprecise. On p. 9, he remarks that the two elliptic points become singularities on $overline{Gamma(1) backslash mathfrak{h}}$, and since $mathbb{P}^1(mathbb{C})$ is nonsingular this means they can't be isomorphic. What he probably actually means is that once we resolve these singularities, the resulting nonsingular Riemann surface is isomorphic to $mathbb{P}^1(mathbb{C})$. One can resolve the singularities by defining specific charts that take into account these stabilizers: this is done for instance in $S2.2$ of Diamond and Shurman or $S1.8$ of Miyake.
– André 3000
Nov 22 '18 at 0:45




I think Zagier is just being imprecise. On p. 9, he remarks that the two elliptic points become singularities on $overline{Gamma(1) backslash mathfrak{h}}$, and since $mathbb{P}^1(mathbb{C})$ is nonsingular this means they can't be isomorphic. What he probably actually means is that once we resolve these singularities, the resulting nonsingular Riemann surface is isomorphic to $mathbb{P}^1(mathbb{C})$. One can resolve the singularities by defining specific charts that take into account these stabilizers: this is done for instance in $S2.2$ of Diamond and Shurman or $S1.8$ of Miyake.
– André 3000
Nov 22 '18 at 0:45










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