Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On the algebraic dimension of twistor spaces over the connected sum of
  four complex projective planes   We study the algebraic dimension of twistor spaces of positive type over
$4\bbfP^2$. We show that such a twistor space is Moishezon if and only if its
anticanonical class is not nef. More precisely, we show the equivalence of
being Moishezon with the existence of a smooth rational curve having negative
intersection number with the anticanonical class. Furthermore, we give precise
information on the dimension and base locus of the fundamental linear system
$|{-1/2}K|$. This implies, for example, $\dim|{-1/2}K|\leq a(Z)$. We
characterize those twistor spaces over $4\bbfP^2$, which contain a pencil of
divisors of degree one by the property $\dim|{-1/2}K| = 3$.

25
The categories of this paper are: patt-sol
19
The categories of this paper are: eess
1
The categories of this paper are: cs
8
The categories of this paper are: hep-ex
6
The categories of this paper are: astro-ph
13
The categories of this paper are: quant-ph
12
The categories of this paper are: nucl-th
7
The categories of this paper are: hep-th
27
The categories of this paper are: comp-gas
16
The categories of this paper are: stat
29
The categories of this paper are: funct-an
21
The categories of this paper are: adap-org
15
The categories of this paper are: nucl-ex
32
The categories of this paper are: atom-ph
36
The categories of this paper are: cmp-lg
5
The categories of this paper are: gr-qc