Quantum network utility: A framework for benchmarking quantum networks.

The central aim of quantum networks is to facilitate user connectivity via quantum channels, but there is an open need for benchmarking metrics to compare diverse quantum networks. Here, we propose a general framework for quantifying the performance of a quantum network by estimating the value created by connecting users through quantum channels. In this framework, we define the quantum network utility metric [Formula: see text] to capture the social and economic value of quantum networks. The proposed framework accommodates a variety of applications from secure communications to distributed sensing. As a case study, we investigate the example of distributed quantum computing in detail. We determine the scaling laws of quantum network utility, which suggest that distributed edge quantum computing has more potential for success than its classical equivalent. We believe the proposed utility-based framework will serve as a foundation for guiding and assessing the development of quantum network technologies and designs.

Conservation laws and the foundations of quantum mechanics.

In a recent paper, [Y. Aharonov, S. Popescu, D. Rohrlich, Proc. Natl. Acad. Sci. U.S.A.118 e1921529118 (2021)], it was argued that while the standard definition of conservation laws in quantum mechanics, which is of a statistical character, is perfectly valid, it misses essential features of nature and it can and must be revisited to address the issue of conservation/nonconservation in individual cases. Specifically, in the above paper, an experiment was presented in which it can be proven that in some individual cases, energy is not conserved, despite being conserved statistically. It was felt however that this is worrisome and that something must be wrong if there are individual instances in which conservation does not hold, even though this is not required by the standard conservation law. Here, we revisit that experiment and show that although its results are correct, there is a way to circumvent them and ensure individual case conservation in that situation. The solution is however quite unusual, challenging one of the basic assumptions of quantum mechanics, namely that any quantum state can be prepared, and it involves a time-holistic, double nonconservation effect. Our results bring light on the role of the preparation stage of the initial state of a particle and on the interplay of conservation laws and frames of reference. We also conjecture that when such a full analysis of any conservation experiment is performed, conservation is obeyed in every individual case.

Who benefits from voter identification laws?

In the first two decades of the twenty-first century, many American state governments implemented voter identification (ID) laws for elections held in their states. These laws, which commonly mandate photo ID and/or require significant effort by voters lacking ID, sparked an ongoing national debate over the tension between election security and access in a democratic society. The laws' proponents-primarily politicians in the Republican Party-claim that they prevent voter fraud, while Democratic opponents denounce the disproportionate burden they place on historically disadvantaged groups such as the poor and people of color. While these positions may reflect sincerely held beliefs, they also align with the political parties' rational electoral strategies because the groups most likely to be disenfranchised by the laws tend to support Democratic candidates. Are these partisan views on the impact of voter ID correct? Existing research focuses on how voter ID laws affect voter turnout and fraud. But the extent to which they produce observable electoral benefits for Republican candidates and/or penalize Democrats remains an open question. We examine how voter ID impacts the parties' electoral fortunes in races at the state level (state legislatures and governorships) and federal level (United States Congress and president) during 2003 to 2020. Our results suggest negligible average effects but with some heterogeneity over time. The first laws implemented produced a Democratic advantage, which weakened to near zero after 2012. We conclude that voter ID requirements motivate and mobilize supporters of both parties, ultimately mitigating their anticipated effects on election results.

Complex battlefields favor strong soldiers over large armies in social animal warfare.

In social animals, success can depend on the outcome of group battles. Theoretical models of warfare predict that group fighting ability is proportional to two key factors: the strength of each soldier in the group and group size. The relative importance of these factors is predicted to vary across environments [F. W. Lanchester, Aircraft in Warfare, the Dawn of the Fourth Arm (1916)]. Here, we provide an empirical validation of the theoretical prediction that open environments should favor superior numbers, whereas complex environments should favor stronger soldiers [R. N. Franks, L. W. Partridge, Anim. Behav. 45, 197-199 (1993)]. We first demonstrate this pattern using simulated battles between relatively strong and weak soldiers in a computer-driven algorithm. We then validate this result in real animals using an ant model system: In battles in which the number of strong native meat ant Iridomyrmex purpureus workers is constant while the number of weak non-native invasive Argentine ant Linepithema humile workers increases across treatments, fatalities of I. purpureus are lower in complex than in simple arenas. Our results provide controlled experimental evidence that investing in stronger soldiers is more effective in complex environments. This is a significant advance in the empirical study of nonhuman warfare and is important for understanding the competitive balance among native and non-native invasive ant species.

On the roles of function and selection in evolving systems.

Physical laws-such as the laws of motion, gravity, electromagnetism, and thermodynamics-codify the general behavior of varied macroscopic natural systems across space and time. We propose that an additional, hitherto-unarticulated law is required to characterize familiar macroscopic phenomena of our complex, evolving universe. An important feature of the classical laws of physics is the conceptual equivalence of specific characteristics shared by an extensive, seemingly diverse body of natural phenomena. Identifying potential equivalencies among disparate phenomena-for example, falling apples and orbiting moons or hot objects and compressed springs-has been instrumental in advancing the scientific understanding of our world through the articulation of laws of nature. A pervasive wonder of the natural world is the evolution of varied systems, including stars, minerals, atmospheres, and life. These evolving systems appear to be conceptually equivalent in that they display three notable attributes: 1) They form from numerous components that have the potential to adopt combinatorially vast numbers of different configurations; 2) processes exist that generate numerous different configurations; and 3) configurations are preferentially selected based on function. We identify universal concepts of selection-static persistence, dynamic persistence, and novelty generation-that underpin function and drive systems to evolve through the exchange of information between the environment and the system. Accordingly, we propose a "law of increasing functional information": The functional information of a system will increase (i.e., the system will evolve) if many different configurations of the system undergo selection for one or more functions.

Scaling laws in enzyme function reveal a new kind of biochemical universality.

All life on Earth is unified by its use of a shared set of component chemical compounds and reactions, providing a detailed model for universal biochemistry. However, this notion of universality is specific to known biochemistry and does not allow quantitative predictions about examples not yet observed. Here, we introduce a more generalizable concept of biochemical universality that is more akin to the kind of universality found in physics. Using annotated genomic datasets including an ensemble of 11,955 metagenomes, 1,282 archaea, 11,759 bacteria, and 200 eukaryotic taxa, we show how enzyme functions form universality classes with common scaling behavior in their relative abundances across the datasets. We verify that these scaling laws are not explained by the presence of compounds, reactions, and enzyme functions shared across known examples of life. We demonstrate how these scaling laws can be used as a tool for inferring properties of ancient life by comparing their predictions with a consensus model for the last universal common ancestor (LUCA). We also illustrate how network analyses shed light on the functional principles underlying the observed scaling behaviors. Together, our results establish the existence of a new kind of biochemical universality, independent of the details of life on Earth's component chemistry, with implications for guiding our search for missing biochemical diversity on Earth or for biochemistries that might deviate from the exact chemical makeup of life as we know it, such as at the origins of life, in alien environments, or in the design of synthetic life.

Generalized scaling of spin qubit coherence in over 12,000 host materials.

SignificanceAtomic defects in solid-state materials are promising candidates as quantum bits, or qubits. New materials are actively being investigated as hosts for new defect qubits; however, there are no unifying guidelines that can quantitatively predict qubit performance in a new material. One of the most critical property of qubits is their quantum coherence. While cluster correlation expansion (CCE) techniques are useful to simulate the coherence of electron spins in defects, they are computationally expensive to investigate broad classes of stable materials. Using CCE simulations, we reveal a general scaling relation between the electron spin coherence time and the properties of qubit host materials that enables rapid and quantitative exploration of new materials hosting spin defects.

Thermodynamics of evolution and the origin of life.

We outline a phenomenological theory of evolution and origin of life by combining the formalism of classical thermodynamics with a statistical description of learning. The maximum entropy principle constrained by the requirement for minimization of the loss function is employed to derive a canonical ensemble of organisms (population), the corresponding partition function (macroscopic counterpart of fitness), and free energy (macroscopic counterpart of additive fitness). We further define the biological counterparts of temperature (evolutionary temperature) as the measure of stochasticity of the evolutionary process and of chemical potential (evolutionary potential) as the amount of evolutionary work required to add a new trainable variable (such as an additional gene) to the evolving system. We then develop a phenomenological approach to the description of evolution, which involves modeling the grand potential as a function of the evolutionary temperature and evolutionary potential. We demonstrate how this phenomenological approach can be used to study the "ideal mutation" model of evolution and its generalizations. Finally, we show that, within this thermodynamics framework, major transitions in evolution, such as the transition from an ensemble of molecules to an ensemble of organisms, that is, the origin of life, can be modeled as a special case of bona fide physical phase transitions that are associated with the emergence of a new type of grand canonical ensemble and the corresponding new level of description.

A scoping review of the legal and ethical challenges with the use of normothermic regional perfusion in controlled donation after circulatory determination a death from 2005-2023.

Use of normothermic regional perfusion (NRP) to enable organ reconditioning and assessment in donation after circulatory determination of death (DCD) is controversial. We conducted a scoping review of peer-reviewed articles, news media, legal literature, and professional society position statements addressing ethical and/or legal issues in use of NRP in controlled DCD from January 1, 2005 to January 5, 2024. Thematic analysis, assessing the four principles of bioethics (autonomy, beneficence, non-maleficence, and justice) and sub-themes identified within each, was conducted for the 112 publications meeting inclusion criteria. More than 30 publications addressed the topic in each of 2022 and 2023, versus ≤6 per year previously. Non-maleficence was the most frequently addressed bioethical principle (111/112 publications), and most varied, with 14 subthemes. Attitudes towards NRP differed by type of NRP: Of 72 publications discussing thoracoabdominal NRP, 22 (30.6%) were 'In Favor', 39 (54.2%) 'Neutral', and 11 (15.3%) 'Against'; of 44 discussing abdominal NRP, 23 (52.3%) were 'In Favor', 20 (45.5%) 'Neutral', and 1 (2.3%) 'Against'. Attitudes differed by authors' country, degree, and affiliation, and by clinical focus of the publishing journal. Overall, our review shows the ethical and legal issues raised by NRP remain unresolved, and debate centered on non-maleficence.

Language-like efficiency and structure in house finch song.

Communication needs to be complex enough to be functional while minimizing learning and production costs. Recent work suggests that the vocalizations and gestures of some songbirds, cetaceans and great apes may conform to linguistic laws that reflect this trade-off between efficiency and complexity. In studies of non-human communication, though, clustering signals into types cannot be done a priori, and decisions about the appropriate grain of analysis may affect statistical signals in the data. The aim of this study was to assess the evidence for language-like efficiency and structure in house finch (Haemorhous mexicanus) song across three levels of granularity in syllable clustering. The results show strong evidence for Zipf's rank-frequency law, Zipf's law of abbreviation and Menzerath's law. Additional analyses show that house finch songs have small-world structure, thought to reflect systematic structure in syntax, and the mutual information decay of sequences is consistent with a combination of Markovian and hierarchical processes. These statistical patterns are robust across three levels of granularity in syllable clustering, pointing to a limited form of scale invariance. In sum, it appears that house finch song has been shaped by pressure for efficiency, possibly to offset the costs of female preferences for complexity.

Attitudes and Laws About Abortion Are Linked to Extrinsic Mortality Risk: A Life-History Perspective on Variability in Reproductive Rights.

Abortion policy is conventionally viewed as a political matter with religious overtones. This article offers a different view. From the perspective of evolutionary biology, abortion at a young age can represent prioritization of long-term development over immediate reproduction, a pattern established in other animal species as resulting from stable ecologies with low mortality risk. We examine whether laws and moral beliefs about abortions are linked to local mortality rates. Data from 50 U.S. states, 202 world societies, 2,596 adult individuals in 363 U.S. counties, and 147,260 respondents across the globe suggest that lower levels of mortality risk are associated with more permissive laws and attitudes toward abortion. Those associations were observed when we controlled for religiosity, political ideology, wealth, education, and industrialization. Integrating evolutionary and cultural perspectives offers an explanation as to why moral beliefs and legal norms about reproduction may be sensitive to levels of ecological adversity.

The Legal Landscape for Opioid Treatment Agreements.

Policy Points Opioid treatment agreements (OTAs) are controversial because of the lack of evidence that their use reduces opioid-related harms and the potential risks they pose of stigmatizing patients and undermining the clinician-patient relationship. Even so, their use is now required in most jurisdictions, and their use is influencing the outcomes of civil and criminal lawsuits. More research is needed to evaluate how OTAs are implemented given existing requirements. If additional research does not resolve the current level of uncertainty regarding OTA benefits, then policymakers in jurisdictions where they are required should consider eliminating OTA mandates or providing flexibility in the legal requirements to make room for clinicians and health care institutions to implement best practices. CONTEXT: Opioid treatment agreements (OTAs) are documents that clinicians present to patients when prescribing opioids that describe the risks of opioids and specify requirements that patients must meet to receive their medication. Notwithstanding a lack of evidence that OTAs effectively mitigate opioids' risks, professional organizations recommend that they be implemented, and jurisdictions increasingly require them. We sought to identify the jurisdictions that require OTAs, how OTAs might affect the outcomes of lawsuits that arise when things go wrong, and instances in which the law permits flexibility for clinicians and health care institutions to adopt best practices. METHODS: We surveyed the laws and regulations of all 50 states and the District of Columbia to identify which jurisdictions require the use of OTAs, the circumstances in which OTA use is mandatory, and the terms OTAs must include (if any). We also surveyed criminal and civil judicial decisions in which OTAs were discussed as evidence on which a court relied to make its decision to determine how OTA use influences litigation outcomes. FINDINGS: Results show that a slight majority (27) of jurisdictions now require OTAs. With one exception, the jurisdictions' requirements for OTA use are triggered at least in part by long-term prescribing. There is otherwise substantial variation and flexibility within OTA requirements. Results also show that even in jurisdictions where OTA use is not required by statute or regulation, OTA use can inform courts' reasoning in lawsuits involving patients or clinicians. Sometimes, but not always, OTA use legally protects clinicians from liability. CONCLUSIONS: Our results show that OTA use is entwined with legal obligations in various ways. Clinicians and health care institutions should identify ways for OTAs to enhance clinician-patient relationships and patient care within the bounds of relevant legal requirements and risks.

Range-limited Heaps' law for functional DNA words in the human genome.

Heaps' or Herdan-Heaps' law is a linguistic law describing the relationship between the vocabulary/dictionary size (type) and word counts (token) to be a power-law function. Its existence in genomes with certain definition of DNA words is unclear partly because the dictionary size in genome could be much smaller than that in a human language. We define a DNA word as a coding region in a genome that codes for a protein domain. Using human chromosomes and chromosome arms as individual samples, we establish the existence of Heaps' law in the human genome within limited range. Our definition of words in a genomic or proteomic context is different from other definitions such as over-represented k-mers which are much shorter in length. Although an approximate power-law distribution of protein domain sizes due to gene duplication and the related Zipf's law is well known, their translation to the Heaps' law in DNA words is not automatic. Several other animal genomes are shown herein also to exhibit range-limited Heaps' law with our definition of DNA words, though with various exponents. When tokens were randomly sampled and sample sizes reach to the maximum level, a deviation from the Heaps' law was observed, but a quadratic regression in log-log type-token plot fits the data perfectly. Investigation of type-token plot and its regression coefficients could provide an alternative narrative of reusage and redundancy of protein domains as well as creation of new protein domains from a linguistic perspective.

Two-layer elastic models for single-yeast compressibility with flat microlevers.

Unicellular organisms such as yeast can survive in very different environments, thanks to a polysaccharide wall that reinforces their extracellular membrane. This wall is not a static structure, as it is expected to be dynamically remodeled according to growth stage, division cycle, environmental osmotic pressure and ageing. It is therefore of great interest to study the mechanics of these organisms, but they are more difficult to study than other mammalian cells, in particular because of their small size (radius of a few microns) and their lack of an adhesion machinery. Using flat cantilevers, we perform compression experiments on single yeast cells (S. cerevisiae) on poly-L-lysine-coated grooved glass plates, in the limit of small deformation using an atomic force microscope (AFM). Thanks to a careful decomposition of force-displacement curves, we extract local scaling exponents that highlight the non-stationary characteristic of the yeast behavior upon compression. Our multi-scale nonlinear analysis of the AFM force-displacement curves provides evidence for non-stationary scaling laws. We propose to model these phenomena based on a two-component elastic system, where each layer follows a different scaling law..

Firearm Ownership: A Key Factor to Consider in Firearm Suicide Deaths in Children, Despite State Gun Laws.

INTRODUCTION: Firearm-related suicides among children present a significant public health concern and a tragic loss of young lives. This study explores the relationship between firearm-related suicides, gun ownership, and state-specific gun laws. METHODS: This retrospective cohort study collected data from the Centers for Disease Control and Prevention Wide-Ranging Online Data for Epidemiologic Research on children under 18 who died by firearm-related suicides between 2009 and 2016 in all 50 states and D.C. It also utilized data from the RAND State-Level Estimates of Household Firearm Ownership. The study focused on the rate of child firearm suicide deaths per 100,000 individuals. The key variable of interest was the percentage of guns owned per household in each state. Univariable analysis was conducted to examine the association between individual gun laws and child firearm suicide mortalities, while multivariable regression, adjusting for household gun ownership and significant firearm legislation, was employed to assess connection to child firearm suicide mortality. RESULTS: From 2009 to 2016, 3903 children died from firearm-related suicides in the United States. In our analysis, 15 out of 44 firearm laws were found to be associated with reducing the rates of firearm suicides among children (P < 0.05). However, multivariable regression showed that higher state gun ownership rates were the primary predictor of increased child fatalities from firearms, with children in such states being 325% more likely to die when analyzing handgun laws and 337% more likely when analyzing long gun laws, as indicated by coefficients of 4.25 and 4.37, respectively. No state laws alone notably improved death rates. CONCLUSIONS: Gun ownership has a stronger association with child suicide rates than state-specific gun laws. Given the weight of gun ownership, future research should prioritize comprehensive public health initiatives to prevent child firearm-related suicides.

Firearm-Related Juvenile Death Rates Correlate With Gun Ownership Rates, Measures of Guns in Circulation, and Leniency of Existing Firearm Laws Among U.S. States.

INTRODUCTION: Firearms now represent the leading cause of death in U.S. children. Therefore, this study aimed to determine if state-level rates of gun ownership, guns in circulation, and strictness of firearm-related laws are related to firearm-related mortality among both juveniles and overall populations. MATERIALS AND METHODS: State firearm mortality rates among the juvenile and overall populations were obtained from 2010 to 2020. The number of weapons registered with the Bureau of Alcohol, Tobacco, Firearms, and Explosives (ATF) and federal firearms licensees for each state were also recorded. Giffords Law Center Scorecard Rankings, a relative measure of the restrictiveness of each state's gun laws, were also collected. Unadjusted linear regressions modeled the relationships between firearm-associated mortality and ATF-registered weapons, federal firearm licensees, Giffords Center rankings, and gun ownership rates. Multivariable (adjusted) analyses were performed to control for poverty, unemployment, and poor mental health. RESULTS: Unadjusted analyses demonstrated that higher gun ownership rates and more lenient gun laws were associated with increased firearm-associated mortality among juveniles. Similarly, these measures as well as increased ATF-registered weapons and ATF federal firearm licensees were associated with increased firearm mortality in the overall population. In the adjusted analyses, more ATF-registered weapons, more ATF federal firearm licensees, higher gun ownership rates, and more lenient firearm laws were associated with increased firearm-related mortality in the overall population, while increased gun ownership and higher Giffords Center rankings were associated with increased firearm-associated mortality in the pediatric population. CONCLUSIONS: To reduce the toll of gun violence in the United States, policymakers should focus on implementing more restrictive firearm laws and reducing the prevalence of guns in their communities.

State laws addressing teen dating violence in US high schools: A difference-in-differences study.

OBJECTIVE: Teen dating violence (TDV) is prevalent with lifelong adverse consequences, and strategies to reduce its burden are needed. Many U.S. states have enacted laws to address TDV in schools, but few studies have examined their effectiveness. This study aimed to assess whether state TDV laws were associated with changes in physical TDV victimization among high school students. METHODS: We used repeated cross-sectional data of high school students from the Youth Risk Behavior Survey across 41 states from 1999 to 2019. Using a difference-in-differences approach with an event study design, we compared changes in past-year physical TDV in states that enacted TDV laws (n = 21) compared to states with no required laws (n = 20). Analyses accounted for clustering at the state-level and state and year-fixed effects. We conducted sensitivity analyses to assess the robustness of our findings. RESULTS: In our sample of 1,240,211 students, the prevalence of past-year physical TDV was 9.2% across all state-years. In 1999, the prevalence of TDV at the state-level ranged from 7.5 to 13.0%; in 2019, the prevalence ranged from 3.7 to 10.5%. There was no significant association between TDV laws and past-year physical TDV. Six or more waves after enactment, we observed a non-significant 1.7% percentage point reduction in TDV in states with TDV laws (95% CI: -3.6 to 0.3 percentage points; p = 0.10). CONCLUSIONS: We found no significant association between enactment of TDV laws and physical TDV among high school students. Further research is needed to understand how TDV laws are implemented and components of TDV laws that may influence effectiveness.

Identifying inconsistencies in exotic pet regulations that perpetuate trade in risky species.

Regulatory inconsistencies at different jurisdictional levels have contributed to the global expansion of the exotic pet trade, with resultant increases in the spread of invasive species and pathogens. Researchers have enumerated multiple limitations and environmental risks posed by international and national rules that govern the exotic pet trade, yet little attention has focused on the regulation of the exotic pet trade within national borders. We reviewed state-level regulations that apply to the trade of vertebrate animal taxa in the United States. Definitions and classifications for regulating different vertebrate taxa varied greatly across states, and the terms pet and companion animal were poorly defined and inconsistent across states. States implemented regulations that permit trade in exotic vertebrate pets that are banned from import into the United States owing to public health and conservation concerns. Once species have been imported into the United States, inconsistent internal regulations facilitate the movement of animals that pose substantial invasion and disease risks. Violations of state laws were typically listed as misdemeanors, and the median fine for violating state wildlife trade laws was $1000. Inconsistent and incomplete regulation of exotic vertebrate pets across state borders, in conjunction with limited penalties for violating regulations, has facilitated continued possession of exotic pets in states where these animals are banned. Based on our review of regulatory weaknesses, we conclude that a transition to a federally enforced list of vertebrate species that may be traded as pets is needed, with all other vertebrate species banned from the exotic pet trade unless their potential invasion and disease risks have been assessed and demonstrated to be low or nonexistent.

Identificación de las inconsistencias en las regulaciones de las mascotas exóticas que perpetúan el mercado de especies riesgosas Resumen Las inconsistencias regulatorias en diferentes niveles regulatorios han contribuido a la expansión mundial del mercado de mascotas exóticas, con un incremento resultante en la dispersión de especies invasoras y patógenos. Los investigadores han enumerado varias limitaciones y riesgos ambientales que representan las normas nacionales e internacionales que dictan el mercado de mascotas exóticas, pero se ha puesto poca atención en la regulación de este mercado dentro de las fronteras nacionales. Revisamos las regulaciones a nivel estatal que aplican al mercado de taxones de vertebrados en los Estados Unidos (EU). Entre los estados, las definiciones y clasificaciones para regular el mercado de los diferentes taxones de vertebrados variaron mucho y los términos mascota y animal de compañía contaban con definiciones deficientes e incoherentes. Los estados implementaron regulaciones que permiten el mercado de vertebrados como mascotas exóticas cuya importación está prohibida para los EU debido a cuestiones de salud pública y conservación. Una vez que las especies han sido importadas a los EU, las regulaciones internas incoherentes facilitan el traslado de animales que representan un riesgo importante de invasión y de enfermedad. Con frecuencia, las violaciones a las leyes estatales se denominaban delitos menores y la multa promedio por violar las leyes estatales de comercio de fauna era de $1,000. La regulación incompleta e incoherente del mercado de mascotas exóticas entre los límites estatales, en conjunto con las penalizaciones limitadas por violar las regulaciones, ha facilitado la posesión continua de mascotas exóticas en estados en donde estos animales están prohibidos. Con base en nuestra revisión de las debilidades regulatorias, concluimos que se necesita transitar a una lista con aplicación federal de especies de vertebrados que pueden ser comercializadas como mascotas, con todas las demás especies de vertebrados vetadas del mercado a menos de que se haya evaluado su riesgo potencial de invasión y de enfermedad y se haya demostrado que es bajo o inexistente.

State-Level Firearm Laws and Firearm Homicide in US Cities: Heterogenous Associations by City Characteristics.

Despite well-studied associations of state firearm laws with lower state- and county-level firearm homicide, there is a shortage of studies investigating differences in the effects of distinct state firearm law categories on various cities within the same state using identical methods. We examined associations of 5 categories of state firearm laws-pertaining to buyers, dealers, domestic violence, gun type/trafficking, and possession-with city-level firearm homicide, and then tested differential associations by city characteristics. City-level panel data on firearm homicide cases of 78 major cities from 2010 to 2020 was assessed from the Centers for Disease Control and Prevention's National Vital Statistics System. We modeled log-transformed firearm homicide rates as a function of firearm law scores, city, state, and year fixed effects, along with time-varying city-level confounders. We considered effect measure modification by poverty, unemployment, vacant housing, and income inequality. A one z-score increase in state gun type/trafficking, possession, and dealer law scores was associated with 25% (95% confidence interval [CI]:-0.37,-0.1), 19% (95% CI:-0.29,-0.07), and 17% (95% CI:-0.28, -0.4) lower firearm homicide rates, respectively. Protective associations were less pronounced in cities with high unemployment and high housing vacancy, but more pronounced in cities with high income inequality. In large US cities, state-level gun type/trafficking, possession, and dealer laws were associated with lower firearm homicide rates, but buyers and domestic violence laws were not. State firearm laws may have differential effects on firearm homicides based on city characteristics, and city-wide policies to enhance socioeconomic drivers may add benefits of firearm laws.

Scaling laws: legal and social complexity in US localities.

Law sets out the rules for society and the economy, particularly important for interactions between strangers. Legal code is a form of non-rival infrastructure, a public good important for investment and innovation. This paper investigates whether legal code complexity scales with population size in US localities. We analyse a corpus of municipal codes from 3259 cities and measure legal complexity using various metrics, including number of words, bytes, and compressed bytes. We find that legal complexity scales geometrically with jurisdiction population, with a scaling parameter of approximately 0.2 and an [Formula: see text] of approximately 0.2. The estimated scaling parameter is similar to gross domestic product per capita, consistent with an interpretation of legal codes as regulating social interactions per capita in cities. This article is part of the theme issue 'A complexity science approach to law and governance'.