Wilken Sam, Guerra Rodrigo E, Levine Dov, Chaikin Paul M
Physics Department, New York University, 726 Broadway, New York, New York 10003, USA.
Department of Physics, Technion, IIT, 32000 Haifa, Israel.
Phys Rev Lett. 2021 Jul 16;127(3):038002. doi: 10.1103/PhysRevLett.127.038002.
Sphere packing is an ancient problem. The densest packing is known to be a face-centered cubic (FCC) crystal, with space-filling fraction ϕ_{FCC}=π/sqrt[18]≈0.74. The densest "random packing," random close packing (RCP), is yet ill defined, although many experiments and simulations agree on a value ϕ_{RCP}≈0.64. We introduce a simple absorbing-state model, biased random organization (BRO), which exhibits a Manna class dynamical phase transition between absorbing and active states that has as its densest critical point ϕ_{c_{max}}≈0.64≈ϕ_{RCP} and, like other Manna class models, is hyperuniform at criticality. The configurations we obtain from BRO appear to be structurally identical to RCP configurations from other protocols. This leads us to conjecture that the highest-density absorbing state for an isotropic biased random organization model produces an ensemble of configurations that characterizes the state conventionally known as RCP.
球体堆积是一个古老的问题。已知最致密的堆积是面心立方（FCC）晶体，其空间填充率ϕFCC = π / √18 ≈ 0.74。尽管许多实验和模拟在ϕRCP ≈ 0.64这个值上达成了一致，但最致密的“随机堆积”，即随机密堆积（RCP），仍然没有明确的定义。我们引入了一个简单的吸收态模型，即有偏随机组织（BRO），它在吸收态和活跃态之间表现出一种曼纳类动力学相变，其最致密的临界点ϕc_max ≈ 0.64 ≈ ϕRCP，并且与其他曼纳类模型一样，在临界状态下是超均匀的。我们从BRO获得的构型在结构上似乎与其他协议的RCP构型相同。这使我们推测，各向同性有偏随机组织模型的最高密度吸收态产生了一组构型，这些构型表征了通常被称为RCP的状态。
