连续自旋光子的热力学
Thermodynamics of Continuous Spin photons
AI总结：
该研究探讨了连续自旋粒子作为光子的可能性，证明其热力学行为良好，主要螺旋度模式快速热化，其他模式热化时间由T/ρ决定，并在高能尺度产生可检验的偏差。
摘要：
狭义相对论允许无质量粒子具有不同的整数（或半整数）螺旋度态，这些态在洛伦兹推进下发生混合，类似于有质量粒子的自旋态。这类无质量粒子被称为连续自旋粒子（CSPs），该术语由维格纳提出，其显著特征在于拥有无穷多的自旋极化态。推进下的混合由具有动量单位的自旋尺度 $\rho$ 控制。通常，我们假设 $\rho=0$。已知CSPs的相互作用满足某些简单性质，其中之一是 $\rho\rightarrow 0$ 极限通常恢复无质量标量、光子或引力子的熟悉相互作用，而所有其他极化态在该极限下退耦。因此，人们可以提出疑问：标准模型的光子是否可能是一个具有小而非零 $\rho$ 的CSP？关于这一可能性，最初由维格纳提出的一个担忧是，无穷多的极化态可能对热力学构成问题。为解决此问题，我们研究了与等温物质耦合的CSP光子气体在CSP螺旋度模式和相空间中的热演化。我们发现，由洛伦兹对称性决定的相互作用结构保证了良好的热力学行为。当CSP光子与带电物质的相互作用被开启时，主要的 $h=\pm 1$ 螺旋度模式迅速热化，而其他模式则需要越来越长的时间尺度来热化，这些时间尺度由 $T/\rho$ 的幂次决定。在熟悉的热系统中，CSP光子的行为类似于QED光子，其有效相对论自由度带有小的依赖于 $\rho$ 和时间的修正。在与 $\rho$ 相当的能量尺度上，会出现与熟悉热行为的显著偏差，这可能具有可检验的实验后果。
英文摘要：
Special relativity allows massless particles to have states of different integer (or half-integer) helicities that mix under boosts, much like the spin-states of a massive particle. Such massless particles are known as continuous spin particles (CSPs), a term coined by Wigner, and they are notable for their infinite tower of spin polarizations. The mixing under boosts is controlled by a spin-scale $ρ$ with units of momentum. Normally, we assume $ρ=0$. The interactions of CSPs are known to satisfy certain simple properties, one of which is that the $ρ\rightarrow 0$ limit generically recovers familiar interactions of massless scalars, photons, or gravitons, with all other polarizations decoupling in this limit. Thus, one can ask if the photon of the Standard Model is a CSP at small but non-zero $ρ$. One concern about this possibility -- originally raised by Wigner -- is that the infinite tower of polarizations could pose problems for thermodynamics. To address this question, we study the thermal evolution of a CSP photon gas coupled to isothermal matter, across CSP helicity modes and phase space. We find that the structure of the interactions dictated by Lorentz symmetry imply well behaved thermodynamics. When the CSP photon's interactions to charged matter are turned on, the primary $h=\pm 1$ helicity modes thermalize quickly, while the other modes require increasingly long time-scales to thermalize, set by powers of $T/ρ$. In familiar thermal systems, the CSP photon behaves like the QED photon with small $ρ$- and time- dependent corrections to its effective relativistic degrees of freedom. Sizable departures from familiar thermal behavior arise at energy scales comparable to $ρ$ and could have testable experimental consequences.
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