\(
\def\CC{{\mathbb C}}
\def\RR{{\mathbb R}}
\def\NN{{\mathbb N}}
\def\ZZ{{\mathbb Z}}
\def\QQ{{\mathbb Q}}
\def\TT{{\mathbb T}}
\def\CF{{\operatorname{CF}^\bullet}}
\def\HF{{\operatorname{HF}^\bullet}}
\def\SH{{\operatorname{SH}^\bullet}}
\def\ot{{\leftarrow}}
\def\st{\;:\;}
\def\Fuk{{\operatorname{Fuk}}}
\def\emprod{m}
\def\cone{\operatorname{Cone}}
\def\Flux{\operatorname{Flux}}
\def\li{i}
\def\ev{\operatorname{ev}}
\def\id{\operatorname{id}}
\def\grad{\operatorname{grad}}
\def\ind{\operatorname{ind}}
\def\weight{\operatorname{wt}}
\def\Sym{\operatorname{Sym}}
\def\HeF{\widehat{CHF}^\bullet}
\def\HHeF{\widehat{HHF}^\bullet}
\def\Spinc{\operatorname{Spin}^c}
\def\min{\operatorname{min}}
\def\div{\operatorname{div}}
\def\SH{{\operatorname{SH}^\bullet}}
\def\CF{{\operatorname{CF}^\bullet}}
\def\Tw{{\operatorname{Tw}}}
\def\Log{{\operatorname{Log}}}
\def\TropB{{\operatorname{TropB}}}
\def\wt{{\operatorname{wt}}}
\def\Span{{\operatorname{span}}}
\def\Crit{\operatorname{Crit}}
\def\CritVal{\operatorname{CritVal}}
\def\FS{\operatorname{FS}}
\def\Sing{\operatorname{Sing}}
\def\Coh{\operatorname{Coh}}
\def\Vect{\operatorname{Vect}}
\def\into{\hookrightarrow}
\def\tensor{\otimes}
\def\CP{\mathbb{CP}}
\def\eps{\varepsilon}
\)
Symplectic snippets
\(A\)-model Yukawa coupling
definition 0.0.1 [Mirror symmetry motivation notes]
We use the genus-zero Gromov--Witten invariants from genus-zero Gromov--Witten invariant.
Let \(X\) be a smooth projective Calabi--Yau threefold. The \(A\)-model Yukawa coupling is the formal trilinear form on divisor classes \(\alpha_1,\alpha_2,\alpha_3\in H^{1,1}(X;\CC)\) given by
\[
\langle \alpha_1,\alpha_2,\alpha_3\rangle_A
=
\int_X\alpha_1\wedge\alpha_2\wedge\alpha_3
+
\sum_{0\neq \beta\in H_2(X;\ZZ)_{\mathrm{eff}}}
\langle \alpha_1,\alpha_2,\alpha_3\rangle_{0,\beta}\,q^\beta.
\]
The first term is the classical triple intersection product. The remaining terms are genus-zero Gromov--Witten quantum corrections. If the complexified Kähler parameter is \([B]+i[\omega]\), then one common convention is
\[
q^\beta=\exp\left(2\pi i\int_\beta(B+i\omega)\right).
\]
Different sign conventions for \(q^\beta\) appear in the literature.