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1. On p-Group Isomorphism: search-to-decision, counting-to-decision, and nilpotency class reductions via tensors

   https://doi.org/10.1145/3625308  

   Grochow, Joshua A.; Qiao, Youming (September 2023, ACM Transactions on Computation Theory)

   In this paper we study some classical complexity-theoretic questions regarding GroupIsomorphism(GpI). We focus onp-groups (groups of prime power order) with oddp, which are believed to be a bottleneck case for GpI, and work in the model of matrix groups over finite fields. Our main results are as follows. •Although search-to-decision and counting-to-decision reductions have been known for over four decades for GraphIsomorphism(GI), they had remained open for GpI, explicitly asked by Arvind & Torán (Bull. EATCS, 2005). Extending methods from TensorIsomorphism(Grochow & Qiao, ITCS 2021), we show moderately exponential-time such reductions withinp-groups of class 2 and exponentp.•Despitethe widely held belief thatp-groups of class 2 and exponentpare the hardest cases of GpI, there was no reduction to these groups from any larger class of groups. Again using methods from Tensor Isomorphism (ibid.), we show the first such reduction, namely from isomorphism testing ofp-groups of “small” class and exponentpto those of class two and exponentp. For the first results, our main innovation is to develop linear-algebraic analogues of classical graph coloring gadgets, a key technique in studying the structural complexity ofGI. Unlike the graph coloring gadgets, which support restricting to various subgroups of the symmetric group, the problems we study require restricting to various subgroups of the general linear group, which entails significantly different and more complicated gadgets. The analysis of one of our gadgets relies on a classical result from group theory regarding random generation of classical groups (Kantor & Lubotzky, Geom. Dedicata, 1990). For the nilpotency class reduction, we combine a runtime analysis of the Lazard correspondence with TensorIsomorphism-completeness results (Grochow & Qiao, ibid.). 

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2. M icro P rof : Code-level Attribution of Unnecessary Data Transfer in Microservice Applications

   https://doi.org/10.1145/3622787  

   Tariq, Syed Salauddin; Menard, Lance; Su, Pengfei; Roy, Probir (September 2023, ACM Transactions on Architecture and Code Optimization)

   The microservice architecture style has gained popularity due to its ability to fault isolation, ease of scaling applications, and developer’s agility. However, writing applications in the microservice design style has its challenges. Due to the loosely coupled nature, services communicate with others through standard communication APIs. This incurs significant overhead in the application due to communication protocol and data transformation. An inefficient service communication at the microservice application logic can further overwhelm the application. We perform a grey literature review showing that unnecessary data transfer is a real challenge in the industry. To the best of our knowledge, no effective tool is currently available to accurately identify the origins of unnecessary microservice communications that lead to significant performance overhead and provide guidance for optimization. To bridge the knowledge gap, we propose MicroProf, a dynamic program analysis tool to detect unnecessary data transfer in Java-based microservice applications. At the implementation level, MicroProfproposes novel techniques such as remote object sampling and hardware debug registers to monitor remote object usage. MicroProfreports the unnecessary data transfer at the application source code level. Furthermore, MicroProfpinpoints the opportunities for communication API optimization. MicroProfis evaluated on four well-known applications involving two real-world applications and two benchmarks, identifying five inefficient remote invocations. Guided by MicroProf, API optimization achieves an 87.5% reduction in the number of fields within REST API responses. The empirical evaluation further reveals that the optimized services experience a speedup of up to 4.59 ×. 

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3. Investigating the [C ii]-to-H i Conversion Factor and the H i Gas Budget of Galaxies at z ≈ 6 with Hydrodynamic Simulations

   https://doi.org/10.3847/2041-8213/ac982c  

   Vizgan, David; Heintz, Kasper E.; Greve, Thomas R.; Narayanan, Desika; Davé, Romeel; Olsen, Karen P.; Popping, Gergö; Watson, Darach (October 2022, The Astrophysical Journal Letters)

   Abstract One of the most fundamental baryonic matter components of galaxies is the neutral atomic hydrogen (Hi). At low redshifts, this component can be traced directly through the 21 cm transition, but to infer the Higas content of the most distant galaxies, a viable tracer is needed. We here investigate the fidelity of the fine-structure transition of the (²P_3/2−²P_1/3) transition of singly ionized carbon Ciiat 158μm as a proxy for Hiin a set simulated galaxies atz≈ 6, following the work by Heintz et al. We select 11,125 star-forming galaxies from thesimbasimulations, with far-infrared line emissions postprocessed and modeled within the Sigameframework. We find a strong connection between Ciiand Hi, with the relation between this Cii-to-Hirelation (β_[CII]) being anticorrelated with the gas-phase metallicity of the simulated galaxies. We further use these simulations to make predictions for the total baryonic matter content of galaxies atz≈ 6, and specifically the Higas mass fraction. We find mean values ofM_{H I}/M_⋆= 1.4 andM_{H I}/M_bar,tot= 0.45. These results provide strong evidence for Hibeing the dominant baryonic matter component by mass in galaxies atz≈ 6. 

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4. Pileup and Infrared Radiation Annihilation (PIRANHA): a paradigm for continuous jet grooming

   https://doi.org/10.1007/JHEP09(2023)157  

   Alipour-fard, Samuel; Komiske, Patrick T.; Metodiev, Eric M.; Thaler, Jesse (September 2023, Journal of High Energy Physics)

   A<sc>bstract</sc> Jet grooming is an important strategy for analyzing relativistic particle collisions in the presence of contaminating radiation. Most jet grooming techniques introduce hard cutoffs to remove soft radiation, leading to discontinuous behavior and associated experimental and theoretical challenges. In this paper, we introduce Pileup and Infrared Radiation Annihilation (Piranha), a paradigm for continuous jet grooming that overcomes the discontinuity and infrared sensitivity of hard-cutoff grooming procedures. We motivate Piranhafrom the perspective of optimal transport and the Energy Mover’s Distance and review Apollonius Subtraction and Iterated Voronoi Subtraction as examples of Piranha-style grooming. We then introduce a new tree-based implementation of Piranha, Recursive Subtraction, with reduced computational costs. Finally, we demonstrate the performance of Recursive Subtraction in mitigating sensitivity to soft distortions from hadronization and detector effects, and additive contamination from pileup and the underlying event. 

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5. Ain’t No Mountain High Enough: Semiparametric Modeling of LIGO–Virgo’s Binary Black Hole Mass Distribution

   https://doi.org/10.3847/1538-4357/ac3667  

   Edelman, Bruce; Doctor, Zoheyr; Godfrey, Jaxen; Farr, Ben (January 2022, The Astrophysical Journal)

   Abstract We introduce a semiparametric model for the primary mass distribution of binary black holes (BBHs) observed with gravitational waves (GWs) that applies a cubic-spline perturbation to a power law. We apply this model to the 46 BBHs included in the second gravitational-wave transient catalog (GWTC-2). The spline perturbation model recovers a consistent primary mass distribution with previous results, corroborating the existence of a peak at 35M_⊙(>97% credibility) found with the Powerlaw+Peakmodel. The peak could be the result of pulsational pair-instability supernovae. The spline perturbation model finds potential signs of additional features in the primary mass distribution at lower masses similar to those previously reported by Tiwari and Fairhurst. However, with fluctuations due to small-number statistics, the simpler Powerlaw+Peakand BrokenPowerlawmodels are both still perfectly consistent with observations. Our semiparametric approach serves as a way to bridge the gap between parametric and nonparametric models to more accurately measure the BBH mass distribution. With larger catalogs we will be able to use this model to resolve possible additional features that could be used to perform cosmological measurements and will build on our understanding of BBH formation, stellar evolution, and nuclear astrophysics. 

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