Skip to main content
Fixed typo (sorry, didn't get it in the last edit)
Source Link
LSpice
  • 12.9k
  • 4
  • 45
  • 69

For $d$ odd these two components are disconnected, because $I$ and $-I$ induce opposite orientation. For $d$ even, you have an involution, which takes a lattice to a complex conjugate lattice. This involution takes a lattice $\tau_1, \dotsc, \tau_{2d}$ to a complex conjugate lattice $\bar\tau_1, \dotsc, \bar\tau_{2d}$, and has many fixed points.

$\DeclareMathOperator\GL{GL}$However, be very careful about this: "By this https://mathoverflow.net/q/126329 the moduli space of complex $d$-tori is $X = \GL_{d}(\mathbb{C})\backslash{\GL_{2d}(\mathbb{R})}/{\GL_{2d}(\mathbb{Z})}$": for $d\geq 2$, this double quotient is very non-Hausdorff, because $\mathbb{R})/{\GL_{2d}(\mathbb{Z})}$$\GL_{2d}(\mathbb{Z})$ acts on $\GL_{d}(\mathbb{C})\backslash{\GL_{2d}}$$\GL_{d}(\mathbb{C})\backslash{\GL_{2d}(\mathbb{R})}$ with dense orbits, as follows from Ratner theory. It's not very good idea to consider this quotient as an orbifold, because it has codiscrete topology: all open sets are either empty or everything. Detailed explanation is found in Ergodic complex structures on hyperkahler manifolds.

For $d$ odd these two components are disconnected, because $I$ and $-I$ induce opposite orientation. For $d$ even, you have an involution, which takes a lattice to a complex conjugate lattice. This involution takes a lattice $\tau_1, \dotsc, \tau_{2d}$ to a complex conjugate lattice $\bar\tau_1, \dotsc, \bar\tau_{2d}$, and has many fixed points.

$\DeclareMathOperator\GL{GL}$However, be very careful about this: "By this https://mathoverflow.net/q/126329 the moduli space of complex $d$-tori is $X = \GL_{d}(\mathbb{C})\backslash{\GL_{2d}(\mathbb{R})}/{\GL_{2d}(\mathbb{Z})}$": for $d\geq 2$, this double quotient is very non-Hausdorff, because $\mathbb{R})/{\GL_{2d}(\mathbb{Z})}$ acts on $\GL_{d}(\mathbb{C})\backslash{\GL_{2d}}$ with dense orbits, as follows from Ratner theory. It's not very good idea to consider this quotient as an orbifold, because it has codiscrete topology: all open sets are either empty or everything. Detailed explanation is found in Ergodic complex structures on hyperkahler manifolds.

For $d$ odd these two components are disconnected, because $I$ and $-I$ induce opposite orientation. For $d$ even, you have an involution, which takes a lattice to a complex conjugate lattice. This involution takes a lattice $\tau_1, \dotsc, \tau_{2d}$ to a complex conjugate lattice $\bar\tau_1, \dotsc, \bar\tau_{2d}$, and has many fixed points.

$\DeclareMathOperator\GL{GL}$However, be very careful about this: "By this https://mathoverflow.net/q/126329 the moduli space of complex $d$-tori is $X = \GL_{d}(\mathbb{C})\backslash{\GL_{2d}(\mathbb{R})}/{\GL_{2d}(\mathbb{Z})}$": for $d\geq 2$, this double quotient is very non-Hausdorff, because $\GL_{2d}(\mathbb{Z})$ acts on $\GL_{d}(\mathbb{C})\backslash{\GL_{2d}(\mathbb{R})}$ with dense orbits, as follows from Ratner theory. It's not very good idea to consider this quotient as an orbifold, because it has codiscrete topology: all open sets are either empty or everything. Detailed explanation is found in Ergodic complex structures on hyperkahler manifolds.

`\dotsc` and `\DeclareMathOperator`
Source Link
LSpice
  • 12.9k
  • 4
  • 45
  • 69

For $d$ odd these two components are disconnected, because $I$ and $-I$ induce opposite orientation. For $d$ even, you have an involution, which takes a lattice to a complex conjugate lattice. This involution takes a lattice $\tau_1, ..., \tau_{2d}$$\tau_1, \dotsc, \tau_{2d}$ to a complex conjugate lattice $\bar\tau_1, ..., \bar\tau_{2d}$$\bar\tau_1, \dotsc, \bar\tau_{2d}$, and has many fixed points.

However$\DeclareMathOperator\GL{GL}$However, be very careful about this: "By this https://mathoverflow.net/q/126329 the moduli space of complex $d$-tori is $X = GL_{d}(\mathbb{C})\backslash GL_{2d}(\mathbb{R})/GL_{2d}(\mathbb{Z})$$X = \GL_{d}(\mathbb{C})\backslash{\GL_{2d}(\mathbb{R})}/{\GL_{2d}(\mathbb{Z})}$": for $d\geq 2$, this double quotient is very non-Hausdorff, because $\mathbb{R})/GL_{2d}(\mathbb{Z})$$\mathbb{R})/{\GL_{2d}(\mathbb{Z})}$ acts on $GL_{d}(\mathbb{C})\backslash GL_{2d}$$\GL_{d}(\mathbb{C})\backslash{\GL_{2d}}$ with dense orbits, as follows from Ratner theory. It's not very good idea to consider this quotient as an orbifold, because it has codiscrete topology: all open sets are either empty or everything. Detailed explanation is found in this paper: https://arxiv.org/abs/1306.1498Ergodic complex structures on hyperkahler manifolds ("Ergodic complex structures on hyperkahler manifolds").

For $d$ odd these two components are disconnected, because $I$ and $-I$ induce opposite orientation. For $d$ even, you have an involution, which takes a lattice to a complex conjugate lattice. This involution takes a lattice $\tau_1, ..., \tau_{2d}$ to a complex conjugate lattice $\bar\tau_1, ..., \bar\tau_{2d}$, and has many fixed points.

However, be very careful about this: "By this https://mathoverflow.net/q/126329 the moduli space of complex $d$-tori is $X = GL_{d}(\mathbb{C})\backslash GL_{2d}(\mathbb{R})/GL_{2d}(\mathbb{Z})$": for $d\geq 2$, this double quotient is very non-Hausdorff, because $\mathbb{R})/GL_{2d}(\mathbb{Z})$ acts on $GL_{d}(\mathbb{C})\backslash GL_{2d}$ with dense orbits, as follows from Ratner theory. It's not very good idea to consider this quotient as an orbifold, because it has codiscrete topology: all open sets are either empty or everything. Detailed explanation is found in this paper: https://arxiv.org/abs/1306.1498 ("Ergodic complex structures on hyperkahler manifolds")

For $d$ odd these two components are disconnected, because $I$ and $-I$ induce opposite orientation. For $d$ even, you have an involution, which takes a lattice to a complex conjugate lattice. This involution takes a lattice $\tau_1, \dotsc, \tau_{2d}$ to a complex conjugate lattice $\bar\tau_1, \dotsc, \bar\tau_{2d}$, and has many fixed points.

$\DeclareMathOperator\GL{GL}$However, be very careful about this: "By this https://mathoverflow.net/q/126329 the moduli space of complex $d$-tori is $X = \GL_{d}(\mathbb{C})\backslash{\GL_{2d}(\mathbb{R})}/{\GL_{2d}(\mathbb{Z})}$": for $d\geq 2$, this double quotient is very non-Hausdorff, because $\mathbb{R})/{\GL_{2d}(\mathbb{Z})}$ acts on $\GL_{d}(\mathbb{C})\backslash{\GL_{2d}}$ with dense orbits, as follows from Ratner theory. It's not very good idea to consider this quotient as an orbifold, because it has codiscrete topology: all open sets are either empty or everything. Detailed explanation is found in Ergodic complex structures on hyperkahler manifolds.

Source Link
Misha Verbitsky
  • 9.2k
  • 1
  • 28
  • 48

For $d$ odd these two components are disconnected, because $I$ and $-I$ induce opposite orientation. For $d$ even, you have an involution, which takes a lattice to a complex conjugate lattice. This involution takes a lattice $\tau_1, ..., \tau_{2d}$ to a complex conjugate lattice $\bar\tau_1, ..., \bar\tau_{2d}$, and has many fixed points.

However, be very careful about this: "By this https://mathoverflow.net/q/126329 the moduli space of complex $d$-tori is $X = GL_{d}(\mathbb{C})\backslash GL_{2d}(\mathbb{R})/GL_{2d}(\mathbb{Z})$": for $d\geq 2$, this double quotient is very non-Hausdorff, because $\mathbb{R})/GL_{2d}(\mathbb{Z})$ acts on $GL_{d}(\mathbb{C})\backslash GL_{2d}$ with dense orbits, as follows from Ratner theory. It's not very good idea to consider this quotient as an orbifold, because it has codiscrete topology: all open sets are either empty or everything. Detailed explanation is found in this paper: https://arxiv.org/abs/1306.1498 ("Ergodic complex structures on hyperkahler manifolds")