Preregistered re-analysis of frozen simulation rows. In a central-spin model, information about the central spin is recorded redundantly in its environment, appearing as a plateau in the mutual-information curve between the system and environment fragments; the plateau's height measures the record's strength. On the substrate of configurations whose plateau is intact at the reference dose of an earlier flip-amplitude dose-response study (36 configurations), this study tests whether the substrate-median plateau height builds monotonically with spin-flip coupling strength across six doses. A single deterministic pass; no new simulation.
Universality is a pillar of modern critical phenomena. The standard scenario is that the two-point correlation algebraically decreases with the distance
r as $g(r)\ensuremath{\sim}{r}^{2\ensuremath{-}d\ensuremath{-}\ensuremath{\eta}}$, with
d the spatial dimension and $\ensuremath{\eta}$ the anomalous dimension. Very recently, a logarithmic universality was proposed to describe the extraordinary surface transition of the
O(N) system. In this logarithmic universality,
g(r) decays in a power of logarithmic distance as $g(r)\ensuremath{\sim}(\mathrm{ln}r{)}^{\ensuremath{-}\stackrel{^}{\ensuremath{\eta}}}$, dramatically different from the standard scenario. We explore the three-dimensional
XY model by Monte Carlo simulations, and provide strong evidence for the emergence of logarithmic universality. Moreover, we propose that the finite-size scaling of
g(r,L) has a two-distance behavior: simultaneously containing a large-distance plateau whose height decays logarithmically with
L as $g(L)\ensuremath{\sim}(\mathrm{ln}L{)}^{\ensuremath{-}{\stackrel{^}{\ensuremath{\eta}}}^{\ensuremath{'}}}$ as well as the
r-dependent term $g(r)\ensuremath{\sim}(\mathrm{ln}r{)}^{\ensuremath{-}\stackrel{^}{\ensuremath{\eta}}}$, with ${\stackrel{^}{\ensuremath{\eta}}}^{\ensuremath{'}}\ensuremath{\approx}\stackrel{^}{\ensuremath{\eta}}\ensuremath{-}1$. The critical exponent ${\stackrel{^}{\ensuremath{\eta}}}^{\ensuremath{'}}$, characterizing the height of the plateau, obeys the scaling relation ${\stackrel{^}{\ensuremath{\eta}}}^{\ensuremath{'}}=(N\ensuremath{-}1)/(2\ensuremath{\pi}\ensuremath{\alpha})$ with the RG parameter $\ensuremath{\alpha}$ of helicity modulus. Our picture can also explain the recent numerical results of a Heisenberg system. The advances on logarithmic universality significantly expand our understanding of critical universality.
自旋交换碰撞导致的原子相干性破坏（弛豫）是影响地磁勘探中使用的原子磁力仪灵敏度的重要因素，特别是在高温、非弱磁的情况下为主要影响因素。本文使用光致压窄（light narrowing）效应对其进行限制，通过调节泵浦光的光强与波长来提高原子的极化率，抑制自旋交换碰撞弛豫带来的磁共振线宽的展宽，进而提高磁力仪灵敏度。通过建立钾原子磁力仪理论模型，针对多种变量进行优化，分析其中的不同弛豫过程以及光致压窄效应对原子磁力仪灵敏度的提升。计算结果表明，在一般条件下对于2 cm×2 cm×2 cm的原子气室，温度为200 ℃时，将泵浦率由0 Hz提升到620 Hz，可以将磁共振响应线宽由25 kHz压窄至312 Hz，此时有最优灵敏度为0.171 fT/Hz1/2。计算结果揭示了泵浦光导致的光致展宽和自旋交换碰撞弛豫消除两种机制的竞争关系，并优化了系统参数对磁力计灵敏度的影响。