## Duke Mathematical Journal

### A tropical approach to a generalized Hodge conjecture for positive currents

#### Abstract

In 1982, Demailly showed that the Hodge conjecture follows from the statement that all positive closed currents with rational cohomology class can be approximated by positive linear combinations of integration currents. Moreover, in 2012, he showed that the Hodge conjecture is equivalent to the statement that any $(p,p)$-dimensional closed current with rational cohomology class can be approximated by linear combinations of integration currents. In this article, we find a current which does not verify the former statement on a smooth projective variety for which the Hodge conjecture is known to hold. To construct this current, we extend the framework of “tropical currents”—recently introduced by the first author—from tori to toric varieties. We discuss extremality properties of tropical currents and show that the cohomology class of a tropical current is the recession of its underlying tropical variety. The counterexample is obtained from a tropical surface in $\mathbb{R}^{4}$ whose intersection form does not have the right signature in terms of the Hodge index theorem.

#### Article information

Source
Duke Math. J., Volume 166, Number 14 (2017), 2749-2813.

Dates
Revised: 27 February 2017
First available in Project Euclid: 6 September 2017

https://projecteuclid.org/euclid.dmj/1504684816

Digital Object Identifier
doi:10.1215/00127094-2017-0017

Mathematical Reviews number (MathSciNet)
MR3707289

Zentralblatt MATH identifier
06803182

#### Citation

Babaee, Farhad; Huh, June. A tropical approach to a generalized Hodge conjecture for positive currents. Duke Math. J. 166 (2017), no. 14, 2749--2813. doi:10.1215/00127094-2017-0017. https://projecteuclid.org/euclid.dmj/1504684816

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