We characterize optimal mechanisms for the multiple-good monopoly problem and
provide a framework to find them. We show that a mechanism is optimal if and
only if a measure $\mu$ derived from the buyer's type distribution satisfies
certain stochastic dominance conditions. This measure expresses the marginal
change in the seller's revenue under marginal changes in the rent paid to
subsets of buyer types. As a corollary, we characterize the optimality of
grand-bundling mechanisms, strengthening several results in the literature,
where only sufficient optimality conditions have been derived. As an
application, we show that the optimal mechanism for $n$ independent uniform
items each supported on $[c,c+1]$ is a grand-bundling mechanism, as long as $c$
is sufficiently large, extending Pavlov's result for $2$ items [Pavlov'11]. At
the same time, our characterization also implies that, for all $c$ and for all
sufficiently large $n$, the optimal mechanism for $n$ independent uniform items
supported on $[c,c+1]$ is not a grand bundling mechanism.

该研究研究了多商品垄断问题的最优机制，表明 CD（Cohen-Dehez）中的 mu 测度可以用于确定最优机制，带来了强化了的 Grand-Bundling 机制。