Mathematical Physics · Cross-listed from math.AP
Dispersion for the wave equation with Robin boundary conditions on a 2D convex model domain
Diego Sánchez Sanz
This paper presents a study of dispersion for the two-dimensional Friedlander model with Neumann and Robin boundary conditions, thereby extending previous works treating only Dirichlet boundary conditions. By considering an Airy-type special function, we obtain a parametrix construction similar to the Dirichlet case but with additional terms requiring careful control. By studying the dispersion of this parametrix, we obtain the same dispersive estimates as in previous results for the Dirichlet case, and therefore the same Strichartz estimates.
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Mathematical Physics · Cross-listed from math.AP
Global Strong Solutions for the Affine Darken Class of Maxwell-Stefan Diffusion Systems
Dieter Bothe
The core-diagonal closure of Bothe and Druet identifies multicomponent Darken
diffusion as a thermodynamically consistent Maxwell-Stefan model in which the constitutive data are species tracer diffusivities. Building on the Stieltjes-coordinate and De Giorgi regularity framework introduced in our recent preprint for additive Maxwell-Stefan frictions, we prove global maximal-$L^p$ strong well-posedness, without smallness assumptions, for the affine Darken class with composition-dependent scalar coefficients and uniformly positive tracer diffusivities. We show that this is exactly the maximal Darken class preserving the fixed Stieltjes eigenframe underlying the global argument. For general smooth, uniformly positive Darken tracer diffusivities we also derive the direct constrained flux form, exact mixing-
entropy symmetrization, Fisher dissipation, composition-uniform normal ellipticity, and local strong well-posedness. Solutions in the affine class remain uniformly separated from the simplex boundary, become classical for positive times, and converge exponentially to
equilibrium. Constant multiplicative frictions, including repeated factors, are covered by grouping species with equal factors.
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Mathematical Physics · Cross-listed from cond-mat.soft
From a three-fluid junction to Young's law: Constitutive and rigid-support limits of wetting
Dieter Bothe
Young's law on a rigid solid and the Neumann balance at a three-fluid junction describe different admissible motions. We connect them through an ordered continuum construction. An affine viscoelastic third phase first acquires permanent deformation
memory in the no-relaxation limit at fixed modulus. Independently specified material-surface laws distinguish surface free energy from mechanical surface stress. On the deformable support, displacement of solid material and migration of the wet-dry partition give separate
equilibrium conditions. Stiffening an anchored support suppresses displacement at a fixed macroscopic observation distance but leaves reversible migration possible. The surviving variation gives Young's law; the constrained mechanics remains as a reaction carrying normal and, in general, tangential capillary loads. Two complementary results substantiate this reduction. A clamped finite-strain model with circular
liquid interfaces yields uniform convergence of reduced energies and recovery of the spatial Young angle for global almost minimisers. A separate quadratic half-space model gives convergence of stationary migration derivatives and a nonzero limiting traction distribution. The results explain how a local Neumann-like ridge can coexist with a Young angle measured against the distant wall, while distinguishing
geometric convergence from the control of migration and reaction forces.
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Mathematical Physics
Uniform displacement bounds and Gibbs limits for periodic one-dimensional Riesz gases
Yan Ru Pei
For the neutral periodic one-dimensional Riesz gas with pair potential locally $-|x|^a$, $0<a<1$, we prove a particle-displacement variance bound of order $\beta^{-1}$, uniformly in the number of particles. Log-concavity also gives exponential displacement tails. Every stationary periodic thermodynamic limit is simple, has intensity one, and admits a stationary ordered matching to the unit
lattice with the same bounds. Each limit satisfies the canonical Gibbs equations for the full-line interaction, with an ordinary symmetric spatial principal value for the exterior potential. The matching implies uniformly bounded interval number variance and a positive limiting second moment of the reciprocal-
lattice Fourier average at sufficiently low temperature. The main estimate compares the inverse random Hessian, through deterministic electrical flows, to a transient long-range network.
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Mathematical Physics
Critical and near-critical influence bounds for ferromagnetic Ising models
Yan Ru Pei
For a ferromagnetic Ising model on a graph of maximum degree $\Delta\ge3$, we prove a bound of order $\sqrt n$ on every row of the influence
matrix at the tree uniqueness threshold. The estimate is uniform in the degree, the external fields, and all pinnings. More generally, if the couplings are bounded by $\beta$ and $\varepsilon=((\Delta-1)\tanh\beta-1)_+$, the bound is $C(\sqrt n+n\varepsilon)$. The proof combines a pointwise cavity bound with a positive-series magnetization tilt and the field comparison
theorem of Ding, Song and Sun. The critical estimate removes the logarithm in recent general graphical bounds for the ferromagnetic case. As a consequence, zero-field single-site Glauber dynamics mixes in
polynomial time throughout the supercritical window $\varepsilon=O(\sqrt{\log n/n})$, with the
polynomial degree depending on the window size.
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Mathematical Physics · Cross-listed from hep-th
Six Particles, Infinite Optimism: Towards Positivity Bounds for Six-Point Amplitudes
Stefan Kremminger and Andrew J. Tolley
The systematic generalisation of the well-established $S$-
matrix positivity and bootstrap bounds from $2 \to 2$ scattering processes to higher-point amplitudes has, to date, remained elusive. To address this, we consider a large class of tree-level UV-completions of a single-scalar EFT. Specifically, we consider the most general renormalisable $N$-scalar theory in $D=4$. By explicitly computing tree-level amplitudes for four-, five- and six-point scattering and expanding at low energies, we can search for positivity relations among the expansion coefficients. We find that quite generally positivity bounds are unavailable due to contamination from a specific class of Feynman diagrams that are linear in sign-indefinite cubic couplings. However, by isolating a sector of the full crossing-symmetric low-energy amplitude that is unaffected by these sign-indefinite cubic couplings, we find that selected six-, five- and four-point Wilson coefficients organise into positive semi-definite
matrices. While a violation of these positivity statements only implies that a given EFT is inconsistent with our class of UV completions, the result helps to guide towards what more general positivity bounds for higher-point interactions could, and could not, look like.
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Mathematical Physics · Cross-listed from cs.LG
Hybrid coupling with numerics-informed neural networks and the overlapping Schwarz alternating method
George Chumbipuma, Irina Tezaur, Alejandro Diaz et al. (+1 more)
We develop a hybrid modeling framework for coupling pre-trained numerics-informed neural networks (NINNs) with classical full order models (FOMs) using the overlapping Schwarz alternating method. We consider the two-dimensional advection-
diffusion equation in the advection-dominated, Peclet-number 10^6 regime. We first demonstrate that, unlike the corresponding physics-informed neural network (PINN), a monolithic NINN can be accurately trained on our model problem without domain decomposition. We then employ overlapping multiplicative Schwarz as a deployment mechanism for coupling a pre-trained, subdomain-local NINN with a neighboring FOM, with the NINN weights held fixed throughout the Schwarz iteration. We consider two training approaches for the subdomain-local NINNs: a top-down approach, in which boundary data are obtained from a coupled Schwarz solve on the full domain with a FOM on each subdomain (FOM-FOM Schwarz), and a bottom-up approach, in which boundary traces are generated synthetically on the NINN subdomain without requiring any full-domain solves. The resulting hybrid NINN-FOM solutions agree closely with the corresponding FOM-FOM Schwarz solutions, with the top-down and bottom-up training approaches yielding comparable accuracy.
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All authors George Chumbipuma, Irina Tezaur, Alejandro Diaz, Beatrice Riviere
Mathematical Physics · Cross-listed from cs.LG
Adaptive hybrid coupling with operator inference, the overlapping Schwarz alternating method and reinforcement learning
Trishit Mondal, Irina Tezaur and Anthony Gruber
Hybrid domain decomposition methods provide a flexible framework for coupling full order models (FOMs) and reduced order models (ROMs), but typically assume the model assigned to each subdomain is fixed throughout a simulation. This is limiting for transient problems in which localized features propagate through the domain and the regions requiring high-fidelity resolution change over time. We introduce a reinforcement learning (RL)-based approach for online adaptation of FOM-ROM models coupled via the overlapping Schwarz alternating method (O-SAM), an iterative domain decomposition method that solves subdomain-local problems while exchanging solution information through transmission boundary conditions on overlapping interfaces. Deep Q-networks (DQNs) are trained offline to select among subdomain-local FOMs and pre-trained Operator Inference (OpInf) ROMs using a reward balancing accuracy, cost, and model-switching frequency. Once trained, the policies are deployed predictively on problem instances not seen during training, without requiring a reference FOM solution. We demonstrate the approach on two examples: a 1D advection-
diffusion problem with a moving front, and a 3D linear elastic wave propagation problem implemented in the Norma.jl solid mechanics code. For the advection-
diffusion benchmark, the learned policy dynamically allocates high-fidelity resolution as the front propagates and outperforms static FOM/ROM assignments; letting the
agent also adapt the domain decomposition provides no further benefit. For the elastic wave
benchmark, learned policies for two and three subdomain decompositions track the propagating wave by assigning FOMs to subdomains containing the wave and ROMs elsewhere, as expected. Our results demonstrate the potential of RL to enable predictive online adaptation of model fidelity within Schwarz-based hybrid simulations.
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Mathematical Physics · Cross-listed from quant-ph
Depth analysis of the Quantum Approximate Optimization Algorithm with a Grover mixer
Bojko N. Bakalov and Dimitar Grantcharov
We study the
Quantum Approximate Optimization
Algorithm with a Grover mixer and independently sampled cost and mixing angles. Under a
lattice condition on the cost values carried by the initial state, we prove a depth-independent lower bound for the variance of the loss at every depth, together with the same bound for the derivative with respect to the final mixing angle. The estimate is instance-dependent and, for fixed locality, is inverse
polynomial in the number of
qubits for integer-valued local objective functions with uniformly bounded local terms, in particular for MaxCut. We also establish Grover-type reachability bounds showing that the depth required to approximate a prescribed carried eigenspace is bounded below by a constant multiple of the inverse square root of its initial probability.
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Mathematical Physics
Canonical and symplectic analysis of the Holst action in the $G\rightarrow 0$ limit
Victor Julian Pérez-Aquino and Alberto Escalante
By using the Dirac and symplectic formalisms, the analysis of the Holst action in the $G \rightarrow 0$ limit is performed. We study the theory's full canonical structure and
symmetries. In particular, we focus on the cases $\gamma = i$ and $\gamma \neq i$, aiming to obtain Smolin's auto-self-dual model in terms of the Ashtekar variables and a Barbero-type formulation. We then perform the symplectic analysis and discuss the principal insight of these formalisms.
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Mathematical Physics · Cross-listed from math.PR
String equation for conformal loop ensemble on Liouville quantum gravity sphere
Xin Sun, Baojun Wu and Shengjing Xu
Matrix models express partition functions of random surfaces with prescribed boundary lengths through string equations. We give a probabilistic realization of this structure in Liouville
quantum gravity (LQG). For $\gamma^2\in(8/3,4)$, we construct the
quantum $n$-hole sphere from a
quantum disk decorated by an independent conformal loop ensemble (CLE) and compute its area Laplace transform at fixed boundary lengths. The transform depends only on the total boundary length apart from a simple prefactor and is determined by a hypergeometric string equation. We derive this equation from stable Lévy excursions using LQG/CLE coupling. The conformal welding equation yields symmetric
polynomials that represent integrated LQG/CLE coupling observables. These
polynomials converge to Weil–Petersson volumes of spheres with $n$ geodesic boundaries as $\gamma\downarrow0$.
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Mathematical Physics
An additional possibilities of the standard method of inverting the Radon transform
D.S. Anikonov, S.G. Kazantsev and D.S. Konovalova
The problem of inverting the Radon integral transform in finite-dimensional Euclidean space is considered. The relevance of this topic for probing issues is indicated. It is noted that for the latter direction, it is natural to consider the integrand as discontinuous function. However, the available inversion formulas are only proven for differentiable functions. Therefore, the question of obtaining formulas for discontinuous functions arises. It is set that the required results can be obtained by some modification of available proofs for smooth functions.
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Mathematical Physics
Monodromy Eigenvectors for Difference Equations with Root-of-Unity Step
Vitaly Tarasov and Alexander Varchenko
A qKZ-type discrete flat connection with multiplicative step $p$ has monodromy operators when $p$ is a root of unity. The monodromy operators are commuting endomorphisms of the connection. We construct their eigensections and
eigenvalues. The construction is based on the presentation of the discrete flat connection as a discrete Gauss-Manin connection.
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Mathematical Physics · Cross-listed from gr-qc
Scalar quasinormal and quasibound states of weakly magnetized Ernst–Schwarzschild spacetime: a confluent-Heun Wronskian approach
Danilo S. Ferreira and Luis B. Castro
We study the quasinormal-mode and quasibound-state spectra of a massless scalar field in weakly magnetized Ernst–Schwarzschild spacetime. In the separated $O(B_0^2)$ regime, the Klein–Gordon equation reduces to a radial confluent-Heun equation. We construct an endpoint-selected spectral Wronskian directly from the canonical confluent-Heun recurrence and its regular-to-irregular connection limit. Quasinormal modes and quasibound states are then obtained as zeros of the same analytic spectral function on the radiative and bound sheets, respectively, providing a unified treatment of the two spectral sectors within the separated weak-field problem. The resulting QNM and QBS frequencies agree with independent weak-field Ernst and massive-Schwarzschild
benchmarks available in the literature. We further show, for representative cases, that the frequencies selected by the local Heun-series termination relation examined here do not satisfy the endpoint-selected quasibound-state condition. The construction therefore provides a direct horizon-to-infinity spectral condition for both radiative and bound states within the weak-field Ernst problem.
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Mathematical Physics · Cross-listed from math.AG
On logarithmic Donaldson-Thomas invariants for local Calabi-Yau $4$-folds
Xiaolong Liu
In this paper, we study logarithmic Donaldson-Thomas invariants for local log Calabi-Yau $4$-folds with simple normal crossing divisors. Using the family version of shifted Lagrangian classes announced by Khan-Kinjo-Park-Safronov, we construct relative and family logarithmic $\mathsf{DT}_4$-theories for logarithmic
Hilbert schemes of curves, and prove a degeneration formula. For logarithmic
Hilbert schemes of points, we construct virtual classes and prove a degeneration formula in Chow groups; in particular, it is independent of shifted Lagrangian classes. Finally, combining our degeneration formula with logarithmic cobordism, we explicitly compute the zero-dimensional logarithmic $\mathsf{DT}_4$-invariants for local surface snc pairs.
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Mathematical Physics · Cross-listed from hep-th
Representation Theory of Three-dimensional Corner Symmetries
Giulio Neri and Ludovic Varrin
We study the representation theory of the three-dimensional extended corner
symmetry group associated with a circular corner. Using induced representation techniques, we construct families of representations of the infinite-dimensional corner
symmetry group and analyze their unitarity and irreducibility. We also determine the maximal central extension of the
symmetry group and construct the corresponding projective representations. The analysis is motivated by the role that corner
symmetries play in
quantum gravity, where boundary degrees of freedom — acted upon by the corner transformations — are expected to encode aspects of the
quantum structure of spacetime. In three dimensions, the representation-theoretic structures that emerge are closely related to
symmetry groups and
quantum theories that already appeared as central to the study of
gravity. This work provides a first step toward a systematic description of
quantum gravitational corner degrees of freedom in three dimensions.
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Mathematical Physics · Cross-listed from math.SP
Uniform High-Frequency Localization on Quantum Graphs
Binh T. Nguyen
We study uniform high-frequency localization for the
Laplacian on compact metric graphs through the least $L^2$-mass that eigenfunctions must place in a prescribed measurable observation set. We first identify this asymptotic localization constant with the minimum of a linear functional over the attainable edge-intensity set; in the generic standard-Kirchhoff setting, this set is governed by the regular Gauss image of the secular
manifold. Primitive cycles and exterior-to-exterior paths consequently determine the positivity threshold, but not, in general, the positive numerical value. We introduce a boundary-aware singular-completion cone and prove that it contains all regular secular edge-energy vectors for trees, unicyclic graphs, and closed graphs of cycle rank two. We then construct a cycle-rank-two graph with two Dirichlet leaves for which this completion principle fails. An exact rational separator, combined with a validated Krawczyk enclosure, yields a nonsingular scalar secular state lying outside every boundary-compatible singular sector. A positive radial derivative identity and recurrence in the compact orbit closure convert this local separation into an exact high-frequency eigensequence for a single fixed metric. For a suitable measurable observation set, the true high-frequency localization constant $C_\infty(\omega;\ell)$ and its singular-completion counterpart $C_{\mathrm{sing}}(\omega;\ell)$ satisfy $$C_\infty(\omega;\ell)<1/2<C_{\mathrm{sing}}(\omega;\ell)$$. Thus, singular completion captures the quantitative localization geometry in several low-complexity classes but does not, in general, determine the high-frequency variational problem on a fixed
quantum graph.
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Mathematical Physics · Cross-listed from math.PR
Renormalizing small ball events for branching random walk
Vilas Winstein
Consider a branching random walk (BRW) of depth $n$ with standard Gaussian increments, conditioned on all endpoints lying in an interval of radius $r$ (which may depend on $n$), i.e. a small ball event. We prove that this conditioning results in exponential decay of correlations between the endpoints, with correlation length $O(r)$. Our proof is based on the renormalization group, which in this context captures the effect of the endpoint conditioning on earlier steps in the walk. This effect can be separated into so-called relevant and irrelevant parts, and in our setting the relevant part makes the conditioned BRW behave like a branching Ornstein-Uhlenbeck walk for the first $n-O(r)$ steps, leading to the correlation decay. The irrelevant part shrinks in a nontrivial manner, and the simplest argument to bound it uniformly only yields correlation length $O(r^2)$. To achieve the optimal $O(r)$ bound, we establish that the irrelevant part shrinks horizontally in space before decaying uniformly. The BRW is a prototypical example of a log-correlated Gaussian field, and it forms the basis of many hierarchical field theories in the mathematical formulation of
quantum field theory. As such, we present our results in a general form which is applicable to other hierarchical field theories with confining potentials, of which the small ball conditioned BRW is an example. We apply our general result to two other models: first, the sinh-Gordon model which has a strictly convex potential, so at the level of covariances the model behaves like one with a quadratic potential, i.e. the model has a positive mass. Second, we consider generalizations of the $\phi^4$ model with any power $\alpha \geq 2$; as $\alpha$ increases from $2$ to $\infty$, these power potentials naturally interpolate between the massive (quadratic) potential and the infinite square well potential of the small ball event.
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Mathematical Physics
Higher abelian gauge theory in BV formalism
Shuhan Jiang
A BV structure is constructed on the space of zero modes of a quadratic elliptic higher abelian gauge theory. The associated BV integral is shown to be independent of the choice of zero-mode Lagrangian under mild hypotheses. The construction yields explicit zero-mode partition functions for several $p$-form abelian gauge theories.
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Mathematical Physics · Cross-listed from quant-ph
Regularized barycentric Rényi divergences
Milán Mosonyi
Barycentric Rényi divergences were introduced in [Mosonyi, Bunth, Vrana, Linear
Algebra and its Applications, 2024] as an alternative to standard Kubo-Ando constructions to define multivariate
quantum Rényi divergences. They are defined via a variational expression and depend on a finite collection of
quantum relative
entropies $D^{q_x}$. When all the relative
entropies are monotone under CPTP maps then so are the corresponding barycentric Rényi divergences, and when all the relative
entropies are additive then the corresponding barycentric Rényi divergences are subadditive under tensor product. Additivity has only been established before for the case where all $D^{q_x}$ are chosen to be the Umegaki relative
entropy, which is also the only case where the barycentric Rényi divergence (called the minimal one) was known to admit an explicit expression. Here we settle the problem of additivity by showing that for any choice of monotone
quantum relative
entropies, the regularized barycentric Rényi divergence coincides with the minimal barycentric Rényi divergence on invertible inputs. This in turn implies that if at least two of the $D^{q_x}$ are strictly larger than the Umegaki relative
entropy (in a precise sense), then the resulting barycentric Rényi divergence is not even weakly additive.
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Mathematical Physics · Cross-listed from math.PR
Mass gap for the hierarchical sinh-Gordon model
Omar Abdelghani, Roland Bauerschmidt, Michael Hofstetter et al. (+1 more)
The (massless) sinh-Gordon model is defined in terms of a continuum massless Gaussian free field perturbed by a cosh interaction. For the hierarchical version of the model, we prove existence of the infinite volume limit, a uniform log-Sobolev inequality, and a mass gap. Our results hold for all $b^2 \in (0,1)$ and simplify for $b^2 \in (0,1/2)$ for which the Gaussian multiplicative chaos has two moments. In an appendix, our renormalization group analysis is compared with the
conjectures and controversies in physics which are mostly based on formal analytic continuation of
conjectures for the sine-Gordon model and we raise some questions.
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All authors Omar Abdelghani, Roland Bauerschmidt, Michael Hofstetter, Ofer Zeitouni
Mathematical Physics · Cross-listed from quant-ph
One Gate at a Time: Complexity Growth in Random Quantum Circuits
Zhi Li
A random
unitary quantum circuit is expected to be incompressible for exponentially long times. We show that the constant-error
circuit complexity of a random
unitary circuit grows almost linearly with time as $\Omega(T/\log T)$. The bound holds for all $2\leq T\leq 4^n$ where $n$ is the system size, and involves no other $n$-dependence. This improves previous lower bounds derived from spectral gaps and
unitary designs by a factor of $\mathrm{poly}(n)$. Drawing on insights from
stochastic calculus,
geometric functional analysis, and randomized linear
algebra, our approach exploits the
circuit's response to variations of individual gates and requires no control over convergence to high-order
unitary designs.
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Mathematical Physics
Diassociative conformal algebras and their deformation cohomology
Anupam Sahoo and Apurba Das
In this paper, we introduce diassociative conformal
algebras that unify both associative conformal
algebras and diassociative
algebras. We show that the category of diassociative conformal
algebras is equivalent to the category of equivalence classes of formal distribution diassociative
algebras. By employing its Maurer-Cartan characterization, we then define the cohomology of a diassociative conformal
algebra and show that it carries a Gerstenhaber
algebra structure. Our cohomology can be used to study deformations and extensions of the structure. Finally, we define averaging operators on associative conformal
algebras and find their close relations with diassociative conformal
algebras.
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