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Axioms

Axioms is an international, peer-reviewed, open access journal of mathematics, mathematical logic and mathematical physics, published monthly online by MDPI.
Quartile Ranking JCR - Q2 (Mathematics, Applied)

All Articles (4,718)

Soft-core Coulomb fluids, exemplified by the two-dimensional Gaussian-charge one-component plasma, serve as fundamental benchmarks for both mathematical theory and computational modeling of coarse-grained dynamics, including stochastic density functional theory, dynamical density functional theory, and dissipative particle dynamics. In these systems, the conventional mean-field description, or the random phase approximation (RPA), is frequently employed due to its analytic simplicity; however, its validity is restricted to weak coupling regimes. Here we demonstrate that Coulomb correlations induce a structural crossover to a strongly correlated liquid where the nearest-neighbor distance saturates rather than decreasing monotonically, a behavior fundamentally incompatible with mean-field predictions. Central to our analysis is the emergence of a universal scaling law: when rescaled by the coupling constant, the short-range direct correlation function (DCF) collapses onto a single curve across the strong coupling regime. Exploiting this universality, we construct a closed-form analytic representation of the DCF using a two-Gaussian basis. This compact form accurately reproduces hypernetted-chain radial distribution functions and structure factors while ensuring exact compliance with thermodynamic sum rules. Beyond theoretical elegance, the proposed kernel offers a computationally efficient alternative to RPA-based approximations, enabling real-space dynamical methods to incorporate strong correlations without modifying long-range smoothed-charge electrostatics. Its analytic transparency bridges rigorous integral equation theory and practical dynamical kernels, additionally providing a physics-informed prior for emerging machine-learning models. Collectively, these results establish a mathematically rigorous testbed for advancing the modeling of strongly correlated soft matter systems.

6 February 2026

Upper and lower panels show the 
  Γ
-dependence of HNC results; here, the yellow triangles indicate RPA results, while the HNC color coding is as follows: gray (
  
    4
    ≤
    Γ
    ≤
    50
  
), blue (
  
    60
    ≤
    Γ
    ≤
    80
  
), and red (
  
    100
    ≤
    Γ
    ≤
    140
  
). The (upper panel) compares RDF peak positions 
  
    r
    max
  
 from HNC and RPA, while the (lower panel) presents the peak position 
  
    r
    peak
  
 of 
  
    
      c
      S
    
    
      (
      r
      )
    
  
 for 
  
    r
    ≥
    1
  
 (see inset in Figure 2) and the scaled Fourier component 
  
    
      c
      S
    
    
      (
      
        k
        min
      
      )
    
    /
    Γ
  
 at 
  
    
      k
      min
    
    =
    1
    /
    64
  
. Background shading identifies the scope of our theoretical framework: the orange-shaded regime (
  
    80
    ≤
    Γ
    ≤
    120
  
) highlights where the RDFs and structure factors are accurately reproduced by our proposed model. Our compact analytic representation of the short-range DCF further covers the green-shaded regions (
  
    60
    ≤
    Γ
    ≤
    80
  
 and 
  
    120
    ≤
    Γ
    ≤
    140
  
), for which a robust formula valid over 
  
    60
    ≤
    Γ
    ≤
    140
  
 is presented in Equations (5)–(7).

Complexity (number of spanning trees) is an essential and significant component in the design of communication networks (graphs). To ensure strong resistance and stiffness and to enhance the probability of a connection between two vertices, improvements to a network’s quality and perfection increase the number of trees that span it. Using block matrices and linear algebra techniques, we derive explicit formulas for the number of spanning trees of new graph families that are produced from star graphs in this study. The number of spanning trees in a graph is measured by the entropy of spanning trees, also known as asymptotic complexity, a graph theory metric that assesses the network’s structural robustness and dependability. Increased flexibility, stronger diverse connections, and improved resistance to random structural changes are all indicated by higher entropy. We also investigate the entropy of spanning trees on our graphs at the end of this study. Lastly, we compare the entropy of our graphs to that of other previously studied graphs with average degrees of four and five.

6 February 2026

The cog star graph, 
  
    C
    
      
        S
      
      
        n
      
    
  
.

Let ΦN(X,Y) be the N-th classical modular polynomial and let Z0(N)={(X,Y)C2ΦN(X,Y)=0} be the plane model of the modular curve X0(N). We present an explicit procedure that, for a prime , enumerates all non-cuspidal singular points of Z0() over C and outputs the corresponding pairs of distinct points on X0() mapping to each node. The method relies on the arithmetic (CM) classification of self-intersections of the map and on effective computations of proper ideal classes in imaginary quadratic orders. We also provide a complete and self-contained exposition of Kara’s proof of the automorphism-group equality in the self-intersection setting, making explicit where Kolyvagin’s conductor lemma is used essentially. Finally, we discuss termination, correctness, and practical complexity issues, and we report computational evidence for larger primes using a parallel implementation; in particular, for =389, we obtained 151,288 output pairs in 151,017 seconds on a 56-core machine.

6 February 2026

The plane model 
  
    
      Z
      0
    
    
      (
      3
      )
    
  
 (the affine curve 
  
    
      Φ
      3
    
    
      (
      X
      ,
      Y
      )
    
    =
    0
  
) together with its non-cuspidal singular points (nodes). Each node corresponds to a collision of two distinct points of 
  
    
      X
      0
    
    
      (
      3
      )
    
  
 under the map 
  
    
      Γ
      0
    
    
      (
      3
      )
    
    τ
    ↦
    
      (
      j
      
        (
        τ
        )
      
      ,
      j
      
        (
        3
        τ
        )
      
      )
    
  
, i.e., to a self-intersection coming from two non-equivalent 3-isogenies 
  
    E
    →
    
      E
      ′
    
  
. The plot was generated using Kainberger’s program [19].

Functional data are nowadays routinely collected and stored in a wide variety of fields. Their adequate use and analysis are a challenge for the scientific community. Mathematically, each function can be understood as a sequence of infinite related numbers. Therefore, for statisticians, functional data can be read as a collection of a strongly correlated infinite-dimensional variable. Most existing statistical procedures have been adapted to functional data scenarios. In this manuscript, we are interested in understanding the use of functions for constructing adequate ROC curves and, therefore, for carrying out binary classifications. In particular, we consider the problem of studying the real capacity of functions derived from tissue doppler imaging (TDI) for identifying cardiac dysfunction related to cardiotoxicity therapy (CRTCD) in breast cancer women with high levels of the protein human epidermal growth factor receptor 2 (HER2). With this goal, we use public and freely available data that has been already used for illustrating the use of functional data in the binary classification problem with very different take-home messages. This variability in the conclusions made us question the reproducibility of the results. Here, we explore five different functional approaches, and we think about the clinical use of the provided solutions and their potential overfitting. The main aim of this manuscript is identifying whether published results are excessively optimistic or if they adequately capture the actual capacity of TDI for accurately diagnostic CRTCD.

6 February 2026

CRTCD data. In blue, the 243 trajectories from the CRTCD-negative women; in red, the 27 trajectories from the CRTCD-positive women. Thick lines represent the average within each group. Points are the jittered values of the curves at Cycle = 0.65 (blue negative, red positive).

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Axioms - ISSN 2075-1680