arXiv subjects

Timothy T. Chang

Publications and source records attributed to Timothy T. Chang.

2 recordsLinked to original sources

arXiv2024

Systematic-free limit on new light scalar bosons via isotope shift spectroscopy in Ca$^+$

We report a precise measurement of the isotope shifts in the $4^2$S$_{1/2} \rightarrow 3^2$D$_{3/2}$ electric quadrupole transition at 732~nm in $^{40 - 42,44,48}$Ca$^+$ via high-resolution laser spectroscopy of co-trapped ions, finding measured shifts of 2,775,392,374.8(6.0), 5,347,679,835.1(5.9), and 10,003,129,115.1(5.7)\,Hz between $^{42,44,48}$Ca$^+$and $^{40}$Ca$^+$, respectively. When combined with prior measurements on the $4^2$S$_{1/2} \rightarrow 3^2$D$_{5/2}$ transition [Phys. Rev. A 100, 022514 (2019), https://journals.aps.org/pra/abstract/10.1103/PhysRevA.100.022514] a King Plot analysis shows the data to be consistent with linearity below the level of parts per billion. This observed linearity, which is free of nuclear systematics, improves the previous isotope-shift based limits of Ca$^+$ for couplings of a scalar boson beyond the Standard Model to electrons and neutrons by a factor of 3. Our new limit excludes part of the coupling range remaining for a new physics interpretation after accounting for one higher-order nuclear term in the nonlinear King plot of Yb/Yb$^+$.

physics.atom-ph↗

arXiv2022

Enhancing synchronization by optimal correlated noise

From the flashes of fireflies to Josephson junctions and power infrastructure, networks of coupled phase oscillators provide a powerful framework to describe synchronization phenomena in many natural and engineered systems. Most real-world networks are under the influence of noisy, random inputs, potentially inhibiting synchronization. While noise is unavoidable, here we show that there exist optimal noise patterns which minimize desynchronizing effects and even enhance order. Specifically, using analytical arguments we show that in the case of a two-oscillator model, there exists a sharp transition from a regime where the optimal synchrony-enhancing noise is perfectly anti-correlated, to one where the optimal noise is correlated. More generally, we then use numerical optimization methods to demonstrate that there exist anti-correlated noise patterns that optimally enhance synchronization in large complex oscillator networks. Our results may have implications in real-world networks such as power grids and neuronal networks, which are subject to significant amounts of correlated input noise.

nlin.AO↗