Pome

Theorem 14.29.1DD001DBBE659

Theorem 14.29.1.DD001DBBE659 On $X=\mathbb P^3$, with block homogeneous coordinates $[A:B]$ and Fubini–Study form $\omega _ X$, put

\[ t=\frac{|A|^2}{|A|^2+|B|^2},\qquad a=\frac1{1+\mathrm{e}},\qquad b=\frac{\mathrm{e}}{1+\mathrm{e}},\qquad f_*(t)=(t-a)^2(t-b)^2. \]

There exist a smooth nonclosed Hermitian form $\omega $ and distinct smooth $\omega $-plurisubharmonic functions $u,v$, normalized by $\sup _ Xu=\sup _ Xv=0$, with

B358F4101DED 14.29.2
\begin{equation} (\omega +\mathrm{dd}^{\mathrm{c}}u)^3=(\omega +\mathrm{dd}^{\mathrm{c}}v)^3=f_*(t)\omega _ X^3. \end{equation}

Both solution forms are positive away from the two connected real analytic hypersurfaces $\{ t=a\} $, $\{ t=b\} $, and have complex rank two on them. The density is real analytic on $X$, and it vanishes exactly to second order in the direction transverse to these hypersurfaces. For every $n\geq 4$ the same assertions hold on $\mathbb {P}^3\times \mathbb {P}^{n-3}$, with the pulled-back density and the product Fubini–Study volume, and with rank $n-1$ on the two product hypersurfaces.

Proof. We use the forms $P,Q,R$ and the function $r$ of 14.26.2. By (14.26.4), the construction reduces to finding scalar coefficients with a prescribed product. By (14.26.6),

07B68FE9B8BC 14.29.3
\begin{equation} \omega _ X^3=6(\sigma ')^2P\wedge Q\wedge R, \qquad \sigma '=\sigma (r)\sigma (-r)>0. \end{equation}
$\square$

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