We propose a mechanism explaining the approximately linear growth of Covid19 world total cases as well as the slow linear decrease of the daily new cases (and daily deaths) observed (in average) in USA and Italy. In our explanation, we regard a given population (the whole world or a single nation) as composed by many sub-clusters which, after lockdown, evolve essentially independently. The interaction is modeled by the fact that the outbreak time of the epidemic in a sub-cluster is a random variable with probability density slowly varying in time. The explanation is independent of the law according to which the epidemic evolves in the single sub cluster.

中文翻译：

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Covid19流行中的线性行为是锁定的影响

我们提出一种机制来解释Covid19世界总病例数的近似线性增长以及在美国和意大利观察到的（平均）每日新病例（和每日死亡）的缓慢线性下降。在我们的解释中，我们将给定的人口（整个世界或单个国家）视为由许多子集群组成，这些子集群在锁定后基本上独立地发展。相互作用是通过以下事实来建模的：子集群中流行病的爆发时间是一个随机变量，其概率密度随时间缓慢变化。该解释独立于流行病在单个子集群中发展所依据的法律。