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1. Lower Bounds Against Sparse Symmetric Functions of ACC Circuits: Expanding the Reach of #SAT Algorithms

   https://doi.org/10.1007/s00224-022-10106-8  

   Vyas, Nikhil ; Williams, R. Ryan ( November 2022 , Theory of Computing Systems)

   We continue the program of proving circuit lower bounds via circuit satisfiability algorithms. So far, this program has yielded several concrete results, proving that functions in$\mathsf {Quasi}\text {-}\mathsf {NP} = \mathsf {NTIME}[n^{(\log n)^{O(1)}}]$$\mathrm{Quasi}-\mathrm{NP}=\mathrm{NTIME}\left[n^{{\left(\log n\right)}^{O\left(1\right)}}\right]$and other complexity classes do not have small circuits (in the worst case and/or on average) from various circuit classes$\mathcal { C}$$C$, by showing that$\mathcal { C}$$C$admits non-trivial satisfiability and/or#SAT algorithms which beat exhaustive search by a minor amount. In this paper, we present a new strong lower bound consequence of having a non-trivial#SAT algorithm for a circuit class${\mathcal C}$$C$. Say that a symmetric Boolean functionf(x₁,…,x_n) issparseif it outputs 1 onO(1) values of${\sum }_{i} x_{i}$${\sum }_i{x}_i$. We show that for every sparsef, and for all “typical”$\mathcal { C}$$C$, faster#SAT algorithms for$\mathcal { C}$$C$circuits imply lower bounds against the circuit class$f \circ \mathcal { C}$$f\circ C$, which may bestrongerthan$\mathcal { C}$$C$itself. In particular:

   #SAT algorithms forn^k-size$\mathcal { C}$$C$-circuits running in 2ⁿ/n^ktime (for allk) implyNEXPdoes not have$(f \circ \mathcal { C})$$(f\circ C)$-circuits of polynomial size.

   #SAT algorithms for$2^{n^{{\varepsilon }}}$$2^{n^{\epsilon }}$-size$\mathcal { C}$$C$-circuits running in$2^{n-n^{{\varepsilon }}}$$2^{n-n^{\epsilon }}$time (for someε> 0) implyQuasi-NPdoes not have$(f \circ \mathcal { C})$$(f\circ C)$-circuits of polynomial size.

   Applying#SAT algorithms from the literature, one immediate corollary of our results is thatQuasi-NPdoes not haveEMAJ∘ACC⁰∘THRcircuits of polynomialmore »size, whereEMAJis the “exact majority” function, improving previous lower bounds againstACC⁰[Williams JACM’14] andACC⁰∘THR[Williams STOC’14], [Murray-Williams STOC’18]. This is the first nontrivial lower bound against such a circuit class.

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2. Defect activation and annihilation in CIGS solar cells: an operando x-ray microscopy study

   https://doi.org/10.1088/2515-7655/ab5fa6  

   Stuckelberger, Michael E. ; Nietzold, Tara ; West, Bradley ; Farshchi, Rouin ; Poplavskyy, Dmitry ; Bailey, Jeff ; Lai, Barry ; Maser, Jörg M. ; Bertoni, Mariana I. ( February 2020 , Journal of Physics: Energy)

   The efficiency of thin-film solar cells with a Cu(${\mathrm{In}}_{1-x}$Ga_x)Se₂absorber is limited by nanoscopic inhomogeneities and defects. Traditional characterization methods are challenged by the multi-scale evaluation of the performance at defects that are buried in the device structures. Multi-modal x-ray microscopy offers a unique tool-set to probe the performance in fully assembled solar cells, and to correlate the performance with composition down to the micro- and nanoscale. We applied this approach to the mapping of temperature-dependent recombination for Cu(${\mathrm{In}}_{1-x}$Ga_x)Se₂solar cells with different absorber grain sizes, evaluating the same areas from room temperature to$100°\mathrm{C}$. It was found that poor performing areas in the large-grain sample are correlated with a Cu-deficient phase, whereas defects in the small-grain sample are not correlated with the distribution of Cu. In both samples, classes of recombination sites were identified, where defects were activated or annihilated by temperature. More generally, the methodology of combinedoperandoandin situx-ray microscopy was established at the physical limit of spatial resolution given by the device itself. As proof-of-principle, the measurement of nanoscopic current generation in a solar cell is demonstrated with applied bias voltage and bias light.
3. Nanospectroscopy Captures Nanoscale Compositional Zonation in Barite Solid Solutions

   https://doi.org/10.1038/s41598-018-31335-3  

   Ling, Florence T. ; Hunter, Heather A. ; Fitts, Jeffrey P. ; Peters, Catherine A. ; Acerbo, Alvin S. ; Huang, Xiaojing ; Yan, Hanfei ; Nazaretski, Evgeny ; Chu, Yong S. ( August 2018 , Scientific Reports)

   Scientists have long suspected that compositionally zoned particles can form under far-from equilibrium precipitation conditions, but their inferences have been based on bulk solid and solution measurements. We are the first to directly observe nanoscale trace element compositional zonation in <10 µm-sized particles using X-ray fluorescence nanospectroscopy at the Hard X-ray Nanoprobe (HXN) Beamline at National Synchrotron Light Source II (NSLS-II). Through high-resolution images, compositional zonation was observed in barite (BaSO₄) particles precipitated from aqueous solution, in which Sr²⁺cations as well as HAsO₄²⁻anions were co-precipitated into (Ba,Sr)SO₄or Ba(SO₄,HAsO₄) solid solutions. Under high salinity conditions (NaCl ≥ 1.0 M), bands contained ~3.5 to ~5 times more trace element compared to the center of the particle formed in early stages of particle growth. Quantitative analysis of Sr and As fractional substitution allowed us to determine that different crystallographic growth directions incorporated trace elements to different extents. These findings provide supporting evidence that barite solid solutions have great potential for trace element incorporation; this has significant implications for environmental and engineered systems that remove hazardous substances from water.
4. Anderson–Kitaev spin liquid

   https://doi.org/10.1038/s41535-020-00285-3  

   Yamada, Masahiko G. ( November 2020 , npj Quantum Materials)

   The bond-disordered Kitaev model attracts much attention due to the experimental relevance inα-RuCl₃andA₃LiIr₂O₆(A= H, D, Ag, etc.). Applying a magnetic field to break the time-reversal symmetry leads to a strong modulation in mass terms for Dirac cones. Because of the smallness of the flux gap of the Kitaev model, a small bond disorder can have large influence on itinerant Majorana fermions. The quantization of the thermal Hall conductivityκ^xy/Tdisappears by a quantum Hall transition induced by a small disorder, andκ^xy/Tshows a rapid crossover into a state with a negligible Hall current. We call this immobile liquid state Anderson–Kitaev spin liquid (AKSL). Especially, the critical disorder strengthδJ_c1~ 0.05 in the unit of the Kitaev interaction would have many implications for the stability of Kitaev spin liquids.
5. Recent Updates to the Gas-phase Chemical Reactions and Molecular Lines in CLOUDY: Their Effects on Millimeter and Submillimeter Molecular Line Predictions

   https://doi.org/10.3847/1538-4357/ac7789  

   Shaw, Gargi ; Ferland, G. J. ; Chatzikos, M. ( July 2022 , The Astrophysical Journal)

   Here, we present our current updates to the gas-phase chemical reaction rates and molecular lines in the spectral synthesis codecloudy, and its implications in spectroscopic modeling of various astrophysical environments. We include energy levels, and radiative and collisional rates for HF, CF⁺, HC₃N, ArH⁺, HCl, HCN, CN, CH, and CH₂. Simultaneously, we expand our molecular network involving these molecules. For this purpose, we have added 561 new reactions and have updated the existing 165 molecular reaction rates involving these molecules. As a result,cloudynow predicts all the lines arising from these nine molecules. In addition, we also update H₂–H₂collisional data up to rotational levelsJ= 31 forv= 0. We demonstrate spectroscopic simulations of these molecules for a few astrophysical environments. Our existing model for globules in the Crab Nebula successfully predicts the observed column density of ArH⁺. Our model predicts a detectable amount of HeH⁺, OH⁺, and CH⁺for the Crab Nebula. We also model the interstellar medium toward HD185418, W31C, and NGC 253, and our predictions match with most of the observed column densities within the observed error bars. Very often molecular lines trace various physical conditions. Hence, this update will be very supportive for spectroscopic modeling of various astrophysical environments,more »particularly involving submillimeter and mid-infrared observations using the Atacama Large Millimeter/submillimeter Array and the James Webb Space Telescope, respectively.

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