3,089 papers
2603.28975Remarks on "Further comments on "Rebuttal of "Refutation of "Comment on "Reply to "Comments on "A genuinely natural information measure" " " " " " "
It's a bit tedious, but as John Doe and Jean Roe have insisted on offering further comments on our comprehensive refutation of the former's already tiringly obstinate advances, we feel compelled to review their not even wrong opinions once again, hoping to put some sense back into the discourse.
2603.28975Mar 2026
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Particle-Hole Pair Localization on the Fermi Surface and its Impact on the Correlation Energy
In recent years it has been shown how approximate bosonization can be used to justify the random phase approximation for the correlation energy of interacting fermions in a mean-field scaling limit. At the core is the interpretation of particle-hole excitations close to the Fermi surface at bosons. The main two approaches however differ in emphasizing collective degrees of freedom (particle-hole pairs delocalized over patches on the Fermi surface) or particle-hole pairs exactly localized in momentum space. Both methods lead to equal precision for the correlation energy with regular interaction potentials. This poses the question how big the influence of delocalizing particle-hole pairs really is. In the present note we show that a description with few, completely collective bosonic degrees of freedom only yields an upper bound of about 92% of the optimal value. Nevertheless it is remarkable that such a simple approach comes that close to the optimal bound.
2603.24395Mar 2026
View2603.24028Determinant Formulas for Scattering Matrices of Schrödinger Operators with Finitely Many Concentric $δ$-Shells
We study stationary scattering for Schrödinger operators in $\mathbb R^3$ with finitely many concentric $δ$--shell interactions of constant real strengths. Starting from the self--adjoint realization and the boundary resolvent formula for this model, we show that, after partial--wave reduction, the same finite-dimensional boundary matrices that arise in the resolvent formula also determine the channel scattering coefficients. More precisely, for each angular momentum $\ell$, the channel coefficient $S_\ell(k)$ satisfies $S_\ell(k)=\det K_\ell(k^2-i0)/\det K_\ell(k^2+i0)$ for almost every $k>0$, where $K_\ell(z)=I_N+m_\ell(z)Θ$ is the $\ell$--th reduced boundary matrix. Thus, in each channel, the positive--energy scattering problem is reduced to a finite-dimensional matrix problem, and the scattering phase is recovered from $\det K_\ell(k^2+i0)$. We then study the first nontrivial case of two concentric shells in the $s$--wave channel, where the interaction between the shells produces nontrivial threshold effects. We derive an explicit formula for $S_0(k)$ and analyze its behavior as $k\downarrow0$. In the regular threshold regime, we obtain an explicit scattering length. We further identify a threshold--critical configuration characterized by the existence of a nontrivial zero--energy radial solution, regular at the origin, whose exterior constant term vanishes. In the corresponding nondegenerate exceptional case, the usual finite scattering length breaks down, and instead $S_0(k)\to -1$ as $k\downarrow0$.
2603.24028Mar 2026
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On symbol correspondences for quark systems II: Asymptotics
We study the semiclassical asymptotics of twisted algebras induced by symbol correspondences for quark systems ($SU(3)$-symmetric mechanical systems) as defined in our previous paper [3]. The linear span of harmonic functions on (co)adjoint orbits is identified with the space of polynomials on $\mathfrak{su}(3)$ restricted to these orbits, and we find two equivalent criteria for the asymptotic emergence of Poisson algebras from sequences of twisted algebras of harmonic functions on (co)adjoint orbits which are induced from sequences of symbol correspondences (the fuzzy orbits). Then, we proceed by ``gluing'' the fuzzy orbits along the unit sphere $\mathcal S^7\subset \mathfrak{su}(3)$, defining Magoo spheres, and studying their asymptotic limits. We end by highlighting the possible generalizations from $SU(3)$ to other compact symmetry groups, specially compact simply connected semisimple Lie groups, commenting on some peculiarities from our treatment for $SU(3)$ deserving further investigations.
2603.23893Mar 2026
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Factorized dispersion relations for two coupled systems
We establish that the dispersion relations of any physical system composed of two coupled subsystems, governed by a space-time homogeneous Lagrangian, admit a factorized form G_{1}G_{2}=γG_{\mathrm{c}}, where G_{1} and G_{2} are the subsystem dispersion functions, G_{\mathrm{c}} is the coupling function, and γis the coupling parameter. The result follows from a determinant expansion theorem applied to the block structure of the coupled system matrix, and is illustrated through three examples: the traveling wave tube, vibrations of an airplane wing, and the Mindlin-Reissner plate theory. For the Mindlin-Reissner example we carry out a complete asymptotic analysis of the coupled dispersion branches, establishing that the factorized form provides a precise quantitative measure of mode hybridization: all four branches carry the imprint of both subsystem factors for any nonzero coupling, while asymptotically recovering the identity of pure uncoupled modes at large frequencies and wavenumbers. We further analyze the universal local geometry of the coupled dispersion branches near their intersection - the cross-point model - showing it is generically hyperbolic, and present a mechanical analog in which the wavenumber is replaced by a scalar parameter, exhibiting the same factorized structure and avoided crossin
2603.23664Mar 2026
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Spectral Structure of the Mixed Hessian of the Dispersionless Toda $τ$-Function
We analyze the mixed Hessian of the dispersionless Toda $τ$-function for the $s$-fold symmetric one-harmonic polynomial conformal map. The inverse branch exhibits two distinct thresholds: an analytic threshold $ζ_c$, where the dominant square-root singularity reaches the circle of convergence, and a later geometric threshold $ζ_{\mathrm{univ}}>ζ_c$, where the map ceases to be univalent. We prove that the first spectral instability occurs already at $ζ_c$. In each symmetry sector, the weighted subcritical realization has exactly one logarithmically diverging eigenvalue, whereas the remaining spectrum stays bounded and, after removal of the singular direction, converges to that of a compact limiting remainder. We further continue the corresponding scalar Gram functions beyond $ζ_c$, showing that they admit a generalized hypergeometric description, a Cauchy--Stieltjes representation, and, for $1\le p\le s$, a realization as Weyl functions of bounded Jacobi operators. In particular, these scalar quantities remain finite at $ζ_{\mathrm{univ}}$. This identifies analytic criticality, rather than loss of univalence, as the first spectral threshold of the Toda Hessian.
2603.23424Mar 2026
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Deformation quantization for systems with second-class constraints in deformed fermionic phase space
In order to quantize systems involving second-class constraints, one should use Dirac bracket instead of Poisson bracket. Furthermore, one can specify a star product in which the term linear in $\hbar$ is proportional to the Dirac bracket. In this way an oscillator system in a deformed fermionic phase space is analyzed and the corresponding energy level and Wigner functions are evaluated according to scheme of deformation quantization. We also study the entanglement entropy induced by the deformation of the fermionic phase space.
2603.23411Mar 2026
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Interfacial instability as a trigger for dryout inception in two-phase CO2 flow
Progress in particle physic leads to increasing in detector luminosity and a consequent increasing overheating induced by Joule effect. An effective cooling strategy is the exploitation of CO\textsubscript{2} heat latency in phase-change. An additional challenge, relevant to detectors for High Energy Particles, is the consequent geometrical constrain due to the limited space avialable for the cooling system within the detector arrangement, leading to the implementation of cooling system by means of millichannels. In this context, at relative high vapour quality the liquid phase exhibits annular flow, anticipating the dryout. Dryout is a critical condition where the heat transfer coefficient dramatically drops and dangerous temperature levels can be reached, potentially leading to catastrophic consequences. Experimental evidences reveal that its behavior in two-phase annular flows differs from conventional refrigerants and the fundamental inception-mechanism is not yet understood. This study aims at investigating the key new idea whereby dryout inception is triggered by instability of the liquid-vapour interface. A mathematical model for two-phase annular flow is presented and the stability of the interface between the two fluids is studied through the linear theory. The stability analysis reduces to solving a coupled forth-order differential eigenvalue problem that is treated numerically with an in-house code based on the Chebyshev-$τ$ method. Numerical investigations identify a critical value for the vapour quality, named $x_{dry}$, that leads to interface instability. The resulting predictions on $x_{dry}$ are confirmed by experimental data collected from two independent experimental campaigns, validating the hypothesis that dryout inception is governed by interfacial instabilities.
2603.23371Mar 2026
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Dirac Operators, APS Boundary Conditions, and Spectral Flow on a Finite Warped Cylinder
We study the Dirac operator on a finite warped cylinder coupled to a background $U(1)$ gauge field. We identify the intrinsic endpoint operators defining the Atiyah-Patodi-Singer (APS) boundary condition and derive a determinant characterization of the modewise APS spectrum. In the constant-gauge, invertible setting, the endpoint reduced $η$ contributions cancel, so the APS index vanishes. For smooth gauge families, the APS projector becomes discontinuous when a boundary mode crosses zero. We therefore introduce a regularized APS-type family of self-adjoint endpoint conditions that remains continuous across such crossings. This regularized family admits a real-symplectic boundary formulation within the standard spectral-flow/Maslov framework: for nondegenerate regularization, the zero-mode set coincides with the boundary-zero set, and transverse boundary zeros give isolated regular crossings.
2603.23275Mar 2026
View2603.23257Information-theoretic structure for the Tsallis q-entropy in statistical physics
In this work, we derive information-theoretic properties for a modified Tsallis entropy, hereinafter referred to as q-entropy. We introduce the notions of joint q-entropy, conditional q-entropy, relative q-entropy, conditional mutual q-information, and establish several inequalities analogous to those of classical information theory. Within the context of Markov chains, these results are employed to prove a version of the second law of thermodynamics. Furthermore, we investigate the maximum entropy method in this setting. Finally, we prove a Tsallis version of the Shannon-McMillan-Breiman theorem and discuss the implications of these results in nonextensive statistical physics.
2603.23257Mar 2026
View2603.22974Edge density expansions for the classical Gaussian and Laguerre ensembles
Recent work of Bornemann has uncovered hitherto hidden integrable structures relating to the asymptotic expansion of quantities at the soft edge of Gaussian and Laguerre random matrix ensembles. These quantities are spacing distributions and the eigenvalue density, and the findings cover the cases of the three symmetry classes orthogonal, unitary and symplectic. In this work we give a different viewpoint on these results in the case of the soft edge scaled density, and in the Laguerre case we initiate an analogous study at the hard edge. Our tool is the scalar differential equation satisfied by the latter, known from earlier work. Unlike integral representations, these differential equations in soft edge scaling variables isolate the function of $N$ which is the expansion variable. Moreover, they give information on the correction terms which supplements the findings from the work of Bornemann. In the case of the Gaussian ensemble, we can demonstrate analogous features for Dyson index $β= 6$, which suggests a broader class of models, namely the classical $β$ ensembles, with asymptotic expansions exhibiting integrable features. For the Laguerre ensembles at the hard edge, we give the explicit form of the correction at second order for unitary symmetry, and at first order in the orthogonal and symplectic cases. Various differential relations are demonstrated.
2603.22974Mar 2026
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Spectral topology and edge modes for one-dimensional non-Hermitian photonic crystals
This work investigates edge modes in non-Hermitian photonic crystals with broken spectral reciprocity. In such systems, the spectra of the underlying operators generally form closed loops over the complex plane with nontrivial spectral topology, which gives rise to the so-called skin effect characterized by edge modes localized at interfaces. For discrete lattice models, the skin effect can be understood through the spectral theory of Toeplitz matrices. However, this mathematical framework no longer applies to continuous wave models, where finite-dimensional approximations break down. In this work, we employ a transfer matrix approach to describe wave propagation in one-dimensional periodic media and introduce a new spectral topological invariant based on the eigenvalues of the transfer matrix. The new topological invariant is equivalent to the winding number of the non-Hermitian spectrum and it enables the characterization of edge modes in one-dimensional non-Hermitian photonic crystals. The mathematical theory provides the theoretical foundation for the skin effect in continuous wave models.
2603.22515Mar 2026
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Multivariable Painleve'-II equation: connection formulas for asymptotic solutions
It is shown that a generalization of the Painlevé-II equation (P-II) to a system of coupled equations with symmetry breaking terms is integrable. A Lax pair for this system is used to relate the asymptotic behavior of the solutions at different infinities via an asymptotically exact WKB approach. The analysis relies on an exact solution of the quantum mechanical Demkov-Osherov model (DOM). An application to the problem of unstable vacuum decay during a second order phase transition provides precise scaling of the number of excitations, including subdominant contributions.
2603.22470Mar 2026
View2603.21773The Spectral Shift Function for Non-Self-Adjoint Perturbations
This paper is devoted to the definition and analysis of the spectral shift function (SSF) associated with non-self-adjoint perturbations of self-adjoint operators. Motivated by applications in scattering theory, we consider both trace-class and relatively trace-class perturbations. We extend the Lifshits-Kre__n trace formula to non-self-adjoint operators under suitable assumptions on the spectrum and the behavior of the resolvent. The role of spectral singularities is carefully analyzed, and we provide a generalization of the SSF using functional calculus. Finally, we apply our results to Schr{ö}dinger operators with complex-valued short-range potentials in dimension three. Toy models illustrate properties that one might hope to extend to general cases. In particular, they suggest that the SSF carries information on the presence of complex eigenvalues.
2603.21773Mar 2026
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Dimensional analysis with constraints
We develop a linear-algebraic framework for dimensional analysis in systems with constraints, particularly when variables are numerous or related by implicit relations so that direct elimination is impractical. By expressing both dimensional relations and constraints in logarithmic variables, the problem is reduced to a linear structure. This formulation yields a simple count of independent dimensionless quantities and, more importantly, a purely algebraic procedure to eliminate redundant ones without trial and error. The method is especially effective for systems with implicit or multiple constraints, and is illustrated with the classical drag force problem.
2603.21527Mar 2026
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Homogenization of point interactions
We consider a non-relativistic quantum particle in $\mathbb{R}^d$, $d=2$ or $d = 3$, interacting with singular zero-range potentials concentrated on a large collection of points. We analyze the homogenization regime where the intensities of the singular potentials and the distances between the points simultaneously go to zero as their number grows, while the total interaction strength remains finite. Assuming that the singular potentials have negative scattering lengths and are uniformly distributed, we prove the strong resolvent convergence as $N \to \infty$ of the family of operators to a Schrödinger operator with a regular electrostatic potential. The result is obtained via $Γ$-converge of the associated quadratic forms. Moreover, in presence of an external trapping potential, the convergence is lifted to uniform resolvent sense.
2603.21400Mar 2026
View2603.21200The non-uniform electron gas
The non-uniform (or inhomogeneous) electron gas has received much attention in many-body quantum mechanics and quantum chemistry in the early days of density functional theory, mainly as a theoretical device to construct gradient approximations via linear response theory. In this article, motivated by the recent works of Lewin, Lieb and Seiringer, we propose a definition of the quantum (resp. classical) non-uniform electron gas through the use of the grand-canonical Levy-Lieb functional (resp. the grand-canonical strictly correlated electrons functional), establish these systems as rigorous thermodynamic limits and analyze their basic properties. The non-uniformity of the gas comes from an arbitrary lattice-periodic background density.
2603.21200Mar 2026
View2603.21113Scattering for anisotropic potentials
We consider the scattering for the operator $H=H_o+V$, where the unperturbed operator $H_o$ is not assumed to be elliptic and the potential $V$ is anisotropic. Under some conditions on $H_o$ and $V$ we show that the wave operators for $H_o, H$ exist and are complete, $H$ has no singular continuous spectrum and the eigenvalues of $H$ can accumulate only to zero. For stronger conditions on $V$ the operator $H$ has finite number of eigenvalues only. Moreover, these results are applied to the invariance principle and for time-dependent potentials.
2603.21113Mar 2026
View2603.20776Propagation of Condensation via Neumann Localization in the Dilute Bose Gas
We prove a Neumann localization inequality for the Laplacian that includes a spectral gap. This result is obtained by partitioning a cube into overlapping families of subcubes and analysing the associated projection operators. The resulting operator inequality goes through a discrete Neumann Laplacian on the lattice of boxes and yields a quantitative spectral gap estimate. As an application, we consider the dilute Bose gas with Neumann boundary conditions. Combining the localization method with recently established free-energy lower bounds, we propagate strong condensation estimates from the Gross Pitaevskii scale to larger boxes of side length $R\sim a(ρa^3)^{-\frac{3}{4}-η}$.
2603.20776Mar 2026
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Vertex Centrality Reconstruction in an Inverse Problem for Information Diffusion
We consider an inverse problem in information diffusion modeled by random walks on combinatorial graphs. The problem concerns reconstruction of vertex centrality from the distribution of the first passage times observed on a subset of vertices. We adapt the boundary control method to obtain a direct algorithm that computes the unobserved vertex centrality. The algorithm is numerically implemented and validated on small graphs.
2603.20710Mar 2026
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