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1. Noise in the LIGO livingston gravitational wave observatory due to trains

   https://doi.org/10.1088/1361-6382/acf01f  

   Glanzer, J.; Soni, S.; Spoon, J.; Effler, A.; González, G. (September 2023, Classical and Quantum Gravity)

   Abstract Environmental seismic disturbances limit the sensitivity of LIGO gravitational wave detectors. Trains near the LIGO Livingston detector produce low frequency (0.5– $10\mathrm{H}\mathrm{z}$) ground noise that couples into the gravitational wave sensitive frequency band (10– $100\mathrm{H}\mathrm{z}$) through light reflected in mirrors and other surfaces. We investigate the effect of trains during the Advanced LIGO third observing run, and propose a method to search for narrow band seismic frequencies responsible for contributing to increases in scattered light. Through the use of the linear regression tool Lasso (least absolute shrinkage and selection operator) and glitch correlations, we identify the most common seismic frequencies that correlate with increases in detector noise as 0.6– $0.8\mathrm{H}\mathrm{z}$, 1.7– $1.9\mathrm{H}\mathrm{z}$, 1.8– $2.0\mathrm{H}\mathrm{z}$, and 2.3– $2.5\mathrm{H}\mathrm{z}$in the LIGO Livingston corner station. 

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2. Electronic structure in a transition metal dipnictide TaAs ₂

   https://doi.org/10.1088/1361-648X/ad04fc  

   Regmi, Sabin; Huang, Cheng-Yi; Khan, Mojammel A.; Wang, Baokai; Pradhan Sakhya, Anup; Hosen, M. Mofazzel; Thompson, Jesse; Singh, Bahadur; Denlinger, Jonathan D.; Ishigami, Masahiro; et al (November 2023, Journal of Physics: Condensed Matter)

   Abstract The family of transition-metal dipnictides has been of theoretical and experimental interest because this family hosts topological states and extremely large magnetoresistance (MR). Recently, ${\mathrm{T}\mathrm{a}\mathrm{A}\mathrm{s}}_2$, a member of this family, has been predicted to support a topological crystalline insulating state. Here, by using high-resolution angle-resolved photoemission spectroscopy (ARPES), we reveal both closed and open pockets in the metallic Fermi surface (FS) and linearly dispersive bands on the ( $\bar{2}01$) surface, along with the presence of extreme MR observed from magneto-transport measurements. A comparison of the ARPES results with first-principles computations shows that the linearly dispersive bands on the measured surface of ${\mathrm{T}\mathrm{a}\mathrm{A}\mathrm{s}}_2$are trivial bulk bands. The absence of symmetry-protected surface state on the ( $\bar{2}01$) surface indicates its topologically dark nature. The presence of open FS features suggests that the open-orbit fermiology could contribute to the extremely large MR of ${\mathrm{T}\mathrm{a}\mathrm{A}\mathrm{s}}_2$. 

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3. Deciphering the sensitivity of urban canopy air temperature to anthropogenic heat flux with a forcing-feedback framework

   https://doi.org/10.1088/1748-9326/ace7e0  

   Wang, Linying; Sun, Ting; Zhou, Wenyu; Liu, Maofeng; Li, Dan (August 2023, Environmental Research Letters)

   Abstract The sensitivity of urban canopy air temperature ( $T_a$) to anthropogenic heat flux ( $Q_{AH}$) is known to vary with space and time, but the key factors controlling such spatiotemporal variabilities remain elusive. To quantify the contributions of different physical processes to the magnitude and variability of $\mathrm{\Delta }{T}_a/\mathrm{\Delta }{Q}_{AH}$(where $\mathrm{\Delta }$represents a change), we develop a forcing-feedback framework based on the energy budget of air within the urban canopy layer and apply it to diagnosing $\mathrm{\Delta }{T}_a/\mathrm{\Delta }{Q}_{AH}$simulated by the Community Land Model Urban over the contiguous United States (CONUS). In summer, the median $\mathrm{\Delta }{T}_a/\mathrm{\Delta }{Q}_{AH}$is around 0.01 $\text{K\hspace{0.17em}}{\left(\text{W\hspace{0.17em}}{\text{m}}^{-\text{2}}\right)}^{-1}$over the CONUS. Besides the direct effect of $Q_{AH}$on $T_a$, there are important feedbacks through changes in the surface temperature, the atmosphere–canopy air heat conductance ( $c_a$), and the surface–canopy air heat conductance. The positive and negative feedbacks nearly cancel each other out and $\mathrm{\Delta }{T}_a/\mathrm{\Delta }{Q}_{AH}$is mostly controlled by the direct effect in summer. In winter, $\mathrm{\Delta }{T}_a/\mathrm{\Delta }{Q}_{AH}$becomes stronger, with the median value increased by about 20% due to weakened negative feedback associated with $c_a$. The spatial and temporal (both seasonal and diurnal) variability of $\mathrm{\Delta }{T}_a/\mathrm{\Delta }{Q}_{AH}$as well as the nonlinear response of $\mathrm{\Delta }{T}_a$to $\mathrm{\Delta }{Q}_{AH}$are strongly related to the variability of $c_a$, highlighting the importance of correctly parameterizing convective heat transfer in urban canopy models. 

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4. Sharp decay rate for eigenfunctions of perturbed periodic Schrödinger operators

   https://doi.org/10.1088/1361-6544/adc653  

   Liu, Wencai; Matos, Rodrigo; Treuer, John N (April 2025, Nonlinearity)

   Abstract This paper investigates uniqueness results for perturbed periodic Schrödinger operators on ${\mathbb{Z}}^d$. Specifically, we consider operators of the form $H=-\mathrm{\Delta }+V+v$, where Δ is the discrete Laplacian, $V:{\mathbb{Z}}^d\to \mathbb{R}$is a periodic potential, and $v:{\mathbb{Z}}^d\to \mathbb{C}$represents a decaying impurity. We establish quantitative conditions under which the equation $-\mathrm{\Delta }u+Vu+vu=\lambda u$, for $\lambda \in \mathbb{C}$, admits only the trivial solution $u\equiv 0$. Key applications include the absence of embedded eigenvalues for operators with impurities decaying faster than any exponential function and the determination of sharp decay rates for eigenfunctions. Our findings extend previous works by providing precise decay conditions for impurities and analyzing different spectral regimes ofλ. 

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5. Stratospheric contribution to the summertime high surface ozone events over the western united states

   https://doi.org/10.1088/1748-9326/abba53  

   Wang, Xinyue; Wu, Yutian; Randel, William; Tilmes, Simone (October 2020, Environmental Research Letters)

   Abstract The stratospheric influence on summertime high surface ozone ( ${\mathrm{O}}_3$) events is examined using a twenty-year simulation from the Whole Atmosphere Community Climate Model. We find that ${\mathrm{O}}_3$transported from the stratosphere makes a significant contribution to the surface ${\mathrm{O}}_3$variability where background surface ${\mathrm{O}}_3$exceeds the 95thpercentile, especially over western U.S. Maximum covariance analysis is applied to ${\mathrm{O}}_3$anomalies paired with stratospheric ${\mathrm{O}}_3$tracer anomalies to identify the stratospheric intrusion and the underlying dynamical mechanism. The first leading mode corresponds to deep stratospheric intrusions in the western and northern tier of the U.S., and intensified northeasterlies in the mid-to-lower troposphere along the west coast, which also facilitate the transport to the eastern Pacific Ocean. The second leading mode corresponds to deep intrusions over the Intermountain Regions. Both modes are associated with eastward propagating baroclinic systems, which are amplified near the end of the North Pacific storm tracks, leading to strong descents over the western U.S. 

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