论文标题

任意自旋粒子的固定结构

The coset construction for particles of arbitrary spin

论文作者

Landry, Michael J., Sun, Guanhao

论文摘要

当庞加莱不变的系统自发打破连续的内部对称性时,戈德石的定理要求在与破碎的对称发生器的一对一对应中存在无质量的零零激发。但是,当系统自发打破庞加莱对称性时,满足Goldstone定理的激发可能会非常不寻常。特别是,它们可能具有任何旋转,不需要是颗粒甚至准颗粒。但是,用于制定金石的有效动作的标准固定结构是相当限制的,并且无法产生Goldstone定理允许的全部可能性。我们通过假设自发打破庞加莱对称的系统的新型cost构造来对这个问题提出一种(部分)补救措施。这种新结构能够以广泛的金石激发(包括费米子的自由度)来产生有效的动作 - 即使所有对称性都是玻感的,也是如此。为了证明它的效用,我们专注于为各种旋转点粒子构建有效的动作。我们恢复了一个已知的结果,即旋转$ s $的粒子需要$ \ Mathcal n = 2S $ supersymmetricricric supersymmetric reparamporterage仪表对称性,我们在coset构造级别实现。在此过程中,我们发现无质量的颗粒需要一种新型的逆希格(Higgs)约束,该约束与在某些费米液体有效场理论中出现的动态逆希格(Higgs)约束具有一定的相似之处。然后,我们考虑除量子自旋外具有有限的空间范围并且可以自由旋转的颗粒。我们得出了这种颗粒的新作用,并在固有的量子自旋与物理旋转自由度之间找到了“自旋轨道”耦合。

When a Poincaré-invariant system spontaneously breaks continuous internal symmetries, Goldstones's theorem demands the existence of massless, spin-zero excitations in a one-to-one correspondence with the broken symmetry generators. When a system spontaneously breaks Poincaré symmetry, however, the kinds of excitations that satisfy Goldstone's theorem can be quite unusual. In particular, they may have any spin and need not be particles or even quasiparticles. The standard coset construction used to formulate effective actions of Goldstones, however, is rather restrictive and is incapable of generating the full spectrum of possibilities allowed by Goldstone's theorem. We propose a (partial) remedy to this problem by postulating a novel coset construction for systems that spontaneously break Poincaré symmetry. This new construction is capable of generating effective actions with a wide range of Goldstone excitations---including fermionic degrees of freedom---even when all symmetries are bosonic. To demonstrate it's utility, we focus on constructing effective actions for point particles of various spins. We recover the known result that a particle of spin $s$ requires an $\mathcal N=2s$ supersymmetric worldline reparameterization gauge symmetry, which we implement at the level of the coset construction. In the process, we discover that massless particles require a novel kind of inverse Higgs constraint that bears some resemblance to the dynamical inverse Higgs constraints that appear in certain fermi liquid effective field theories. We then consider particles that, in addition to quantum spin, have finite spatial extent and are free to rotate. We derive a novel action for such particles and find a `spin-orbital' coupling between the intrinsic quantum spin and the physical-rotation degrees of freedom.

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