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1. A periodic isoperimetric problem related to the unique games conjecture

   https://doi.org/10.1002/rsa.20877  

   Heilman, Steven (July 2019, Random Structures & Algorithms)

   We prove the endpoint case of a conjecture of Khot and Moshkovitz related to the unique games conjecture, less a small error. Letn ≥ 2. Suppose a subset Ω ofn‐dimensional Euclidean spacesatisfies −Ω = Ω^cand Ω + v = Ω^c(up to measure zero sets) for every standard basis vector. For anyand for anyq ≥ 1, letand let. For anyx ∈ ∂Ω, letN(x) denote the exterior normal vector atxsuch that ‖N(x)‖₂ = 1. Let. Our main result shows thatBhas the smallest Gaussian surface area among all such subsets Ω, less a small error:In particular,Standard arguments extend these results to a corresponding weak inequality for noise stability. Removing the factor 6 × 10⁻⁹would prove the endpoint case of the Khot‐Moshkovitz conjecture. Lastly, we prove a Euclidean analogue of the Khot and Moshkovitz conjecture. The full conjecture of Khot and Moshkovitz provides strong evidence for the truth of the unique games conjecture, a central conjecture in theoretical computer science that is closely related to the P versus NP problem. So, our results also provide evidence for the truth of the unique games conjecture. Nevertheless, this paper does not prove any case of the unique games conjecture. 

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2. Multiwavelength Observations of a New Redback Millisecond Pulsar 4FGL J1910.7−5320

   https://doi.org/10.3847/1538-4357/acae8a  

   Au, Ka-Yui; Strader, Jay; Swihart, Samuel J.; Lin, Lupin C. C.; Kong, Albert K. H.; Takata, Jumpei; Hui, Chung-Yue; Panurach, Teresa; Molina, Isabella; Aydi, Elias; et al (January 2023, The Astrophysical Journal)

   Abstract We present the study of multiwavelength observations of an unidentified Fermi Large Area Telescope (LAT) source, 4FGL J1910.7−5320, a new candidate redback millisecond pulsar binary. In the 4FGL 95% error region of 4FGL J1910.7−5320, we find a possible binary with a 8.36 hr orbital period from the Catalina Real-Time Transient Survey, confirmed by optical spectroscopy using the SOAR telescope. This optical source was recently independently discovered as a redback pulsar by the TRAPUM project, confirming our prediction. We fit the optical spectral energy distributions of 4FGL J1910.7−5320 with a blackbody model, inferring a maximum distance of 4.1 kpc by assuming that the companion fills its Roche lobe with a radius ofR= 0.7R_☉. Using a 12.6 ks Chandra X-ray observation, we identified an X-ray counterpart for 4FGL J1910.7−5320, with a spectrum that can be described by an absorbed power law with a photon index of 1.0 ± 0.4. The spectrally hard X-ray emission shows tentative evidence for orbital variability. Using more than 12 yr of Fermi-LAT data, we refined the position of theγ-ray source, and the optical candidate still lies within the 68% positional error circle. In addition to 4FGL J1910.7−5320, we find a variable optical source with a periodic signal of 4.28 hr inside the 4FGL catalog 95% error region of another unidentified Fermi source, 4FGL J2029.5−4237. However, theγ-ray source does not have a significant X-ray counterpart in an 11.7 ks Chandra observation, with a 3σflux upper limit of 2.4 × 10⁻¹⁴erg cm⁻²s⁻¹(0.3–7 keV). Moreover, the optical source is outside our updated Fermi-LAT 95% error circle. These observational facts all suggest that this new redback millisecond pulsar powers the gamma-ray source 4FGL J1910.7−5320 while 4FGL J2029.5−4237 is unlikely theγ-ray counterpart to the 4.28 hr variable. 

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3. Ti ₂ CT _x MXene‐based all‐optical modulator

   https://doi.org/10.1002/inf2.12052  

   Yi, Jun; Li, Jie; Huang, Shuohan; Hu, Longyu; Miao, Lili; Zhao, Chujun; Wen, Shuangchun; Mochalin, Vadym N.; Rao, Apparao M. (December 2019, InfoMat)

   Abstract MXenes, a new class of 2D transition metal carbides, nitrides, and carbonitrides, have attracted much attention due to their outstanding properties. Here, we report the broadband spatial self‐phase modulation of Ti₂CT_xMXene nanosheets dispersed in deionized water in the visible to near‐infrared regime, highlighting the broadband nonlinear optical (NLO) response of Ti₂CT_xMXene. Using ultrafast pulsed laser excitation, the nonlinear refractive indexn₂and the third‐order nonlinear susceptibilityof Ti₂CT_xMXene were measured to be ∼10⁻¹³m²/W and ∼ 10⁻¹⁰esu, respectively. Leveraging the large optical nonlinearity of Ti₂CT_xMXene, an all‐optical modulator in the visible regime was fabricated based on the spatial cross‐phase modulation effect. This work suggests that 2D MXenes are ideal broadband NLO materials with excellent prospects in NLO applications. image 

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4. Energy and bandwidth efficiency optimization of quantum-enabled optical communication channels

   https://doi.org/10.1038/s41534-022-00573-9  

   Jabir, M. V.; Annafianto, N. Fajar R.; Burenkov, I. A.; Battou, A.; Polyakov, S. V. (May 2022, npj Quantum Information)

   Abstract We present a systematic study of quantum receivers and modulation methods enabling resource efficient quantum-enhanced optical communication. We introduce quantum-inspired modulation schemes that theoretically yield a better resource efficiency than legacy protocols. Experimentally, we demonstrate below the shot-noise limit symbol error rates forM ≤ 16 legacy and quantum-inspired communication alphabets using software-configurable optical communication time-resolving quantum receiver testbed. Further, we experimentally verify that our quantum-inspired modulation schemes boost the accuracy of practical quantum measurements and significantly optimize the combined use of energy and bandwidth for communication alphabets that are longer thanM = 4 symbols. 

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5. Global response patterns of plant photosynthesis to nitrogen addition: A meta‐analysis

   https://doi.org/10.1111/gcb.15071  

   Liang, Xingyun; Zhang, Tong; Lu, Xiankai; Ellsworth, David S; BassiriRad, Hormoz; You, Chengming; Wang, Dong; He, Pengcheng; Deng, Qi; Liu, Hui; et al (June 2020, Global Change Biology)

   Abstract A mechanistic understanding of plant photosynthetic response is needed to reliably predict changes in terrestrial carbon (C) gain under conditions of chronically elevated atmospheric nitrogen (N) deposition. Here, using 2,683 observations from 240 journal articles, we conducted a global meta‐analysis to reveal effects of N addition on 14 photosynthesis‐related traits and affecting moderators. We found that across 320 terrestrial plant species, leaf N was enhanced comparably on mass basis (N_mass, +18.4%) and area basis (N_area, +14.3%), with no changes in specific leaf area or leaf mass per area. Total leaf area (TLA) was increased significantly, as indicated by the increases in total leaf biomass (+46.5%), leaf area per plant (+29.7%), and leaf area index (LAI, +24.4%). To a lesser extent than for TLA, N addition significantly enhanced leaf photosynthetic rate per area (A_area, +12.6%), stomatal conductance (g_s, +7.5%), and transpiration rate (E, +10.5%). The responses ofA_areawere positively related with that ofg_s, with no changes in instantaneous water‐use efficiency and only slight increases in long‐term water‐use efficiency (+2.5%) inferred from¹³C composition. The responses of traits depended on biological, experimental, and environmental moderators. As experimental duration and N load increased, the responses of LAI andA_areadiminished while that ofEincreased significantly. The observed patterns of increases in both TLA andEindicate that N deposition will increase the amount of water used by plants. Taken together, N deposition will enhance gross photosynthetic C gain of the terrestrial plants while increasing their water loss to the atmosphere, but the effects on C gain might diminish over time and that on plant water use would be amplified if N deposition persists. 

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