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Xujia Chen

Publications and source records attributed to Xujia Chen.

13 recordsLinked to original sources

Continual-Learning Physics-Informed Neural Networks for Parameterized Partial Differential Equations

Physics-informed neural networks (PINNs) incorporate governing equations into neural-network training and can approximate PDE solutions without requiring large observational datasets. Parameterized PINNs (ParamPINNs) further take physical parameters as inputs, allowing a single model to represent a family of PDE solutions over a parameter domain. Existing ParamPINNs, however, still face inefficient training, uneven accuracy across parameters, and overfitting to a limited set of sampled parameter tasks, which can impair generalization to unsampled parameters. To address these issues, we propose a continual-learning physics-informed neural network (CL-PINN), which treats PDE instances at different parameter values as related tasks and learns them sequentially. CL-PINN combines Bayesian-optimization-based active parameter selection, task-wise dynamic loss weighting, sparse physics-constrained replay, and an optional parameter subnetwork to improve task allocation and knowledge retention under bounded active-task capacity. It requires no observational data and is designed to solve parameterized PDEs over relatively broad parameter domains under limited computational resources. Multi-seed evaluations on five benchmarks, including one continuous function and four parameterized PDEs, show that Bayesian selection substantially reduces objective-loss queries relative to grid-greedy search, while sparse replay mitigates forgetting of earlier tasks. Under the prescribed within-case resource protocols, CL-PINN generally provides higher and more balanced solution accuracy than fixed-sampling and grid-greedy baselines. CL-PINN offers a practical route toward learning PDE solutions that generalize across physical parameters and has the potential to support reusable physics-informed surrogates for large-scale engineering parameter studies.

cs.LG

Curriculum Learning of Physics-Informed Neural Networks based on Spatial Correlation

Physics-Informed Neural Networks (PINNs) combine deep learning with physical constraints for solving partial differential equations (PDEs), and are widely applied in fluid mechanics, heat transfer, and solid mechanics. However, PINN training still suffers from high-dimensional non-convex loss landscapes, imbalanced multiobjective constraints, and ineffective information propagation. Existing curriculum learning and causality-guided strategies improve training stability, but mainly focus on temporal or parametric progression, lacking explicit treatment of spatial information propagation and inter-region consistency. Moreover, they are not directly applicable to boundary value problems (BVPs) with strong spatial coupling. To address this issue, we propose a spatially correlated curriculum learning framework for PINNs. To the best of our knowledge, this is the first work to address PINN training difficulties from the perspective of spatial coupling among subregions. First, spatial causal weights guide information from near-boundary regions inward, reducing optimization failures and spurious convergence. Second, a low-frequency information bridge enforces pseudo-label-based consistency across spatially separated regions, suppressing global low-frequency drift. Third, a region-adaptive reweighting strategy adjusts subregion losses to reduce local residuals and recover high-frequency details. Experiments on PDE benchmarks show that, under comparable computational cost, the proposed method alleviates training failures and improves solution accuracy. The code is available at https://github.com/pigofmomo/CurriculumLearningPINN.

cs.LG

Surgery on manifold operads

We study cobordisms of a class of topological operads called ``manifold operads''. These operads are generalizations of the Fulton-MacPherson operad: an operad built from configurations of points in Euclidean space. Cobordism of manifold operads, along with the associated theory of surgery, depends crucially on delicate combinatorial results for trees associated to operadic bimodules. As an application of surgery, we produce infinitely many manifold operads which are left or right ``bimodule cobordant'' to, but not homotopy equivalent to the Fulton-MacPherson operad.

math.AT

The Cohomology Ring of the Deligne-Mumford Moduli Space of Real Rational Curves with Conjugate Marked Points

It is a long-established and heavily-used fact that the integral cohomology ring of the Deligne-Mumford moduli space of (complex) rational curves is the polynomial ring on the boundary divisors modulo the ideal generated by the obvious geometric relations between them. We show that the rational cohomology ring of the Deligne-Mumford moduli space of real rational curves with conjugate marked points only is the polynomial ring on certain (``complex") boundary divisors and real boundary hypersurfaces modulo the ideal generated by the obvious geometric relations between them and the geometric relation in positive dimension and codimension identified in a previous paper.

math.AG

Blowdowns of the Deligne-Mumford Spaces of Real Rational Curves

We describe a sequence of smooth quotients of the Deligne-Mumford moduli space ${\mathbb R}\overline{\mathcal M}_{0,\ell+1}$ of real rational curves with $\ell\!+\!1$ conjugate pairs of marked points that terminates at ${\mathbb R}\overline{\mathcal M}_{0,\ell}\!\times\!{\mathbb C}{\mathbb P}^1$. This produces an analogue of Keel's blowup construction of the Deligne-Mumford moduli spaces $\overline{\mathcal M}_{\ell+1}$ of rational curves with $\ell\!+\!1$ marked points, but with an explicit description of the intermediate spaces and the blowups of three different types. The same framework readily adapts to the real moduli spaces with real points. In a sequel, we use this inductive construction of ${\mathbb R}\overline{\mathcal M}_{0,\ell+1}$ to completely determine the rational (co)homology ring of ${\mathbb R}\overline{\mathcal M}_{0,\ell}$.

math.AG

Kontsevich's Characteristic Classes as Topological Invariants of Configuration Space Bundles

Kontsevich's characteristic classes are invariants of framed smooth fiber bundles with homology sphere fibers. It was shown by Watanabe that they can be used to distinguish smooth $S^4$-bundles that are all trivial as topological fiber bundles. In this article we show that this ability of Kontsevich's classes is a manifestation of the following principle: the ``real blow-up'' construction on a smooth manifold essentially depends on its smooth structure and thus, given a smooth manifold (or smooth fiber bundle) $M$, the topological invariants of spaces constructed from $M$ by real blow-ups could potentially differentiate smooth structures on $M$. The main theorem says that Kontsevich's characteristic classes of a smooth framed bundle $\pi$ are determined by the topology of the 2-point configuration space bundle of $\pi$ and framing data.

math.GT

Spin/Pin-Structures and Real Enumerative Geometry

The present, partly expository, monograph consists of three parts. The first part treats Spin- and Pin-structures from three different perspectives and shows them to be suitably equivalent. It also introduces an intrinsic perspective on the relative Spin- and Pin-structures of Fukaya-Oh-Ohta-Ono and Solomon, establishes properties of these structures in both perspectives, and again shows them to be suitably equivalent. The second part uses the intrinsic perspective on (relative) Spin- and Pin-structures to detail constructions of orientations on the determinants of real Cauchy-Riemann operators and study their properties. The final part applies the results of the first two parts to the enumerative geometry of real curves and obtains an explicit comparison between the curve signs in the intrinsic definition of Welschinger and later Pin-structure dependent definitions. This comparison makes use of both the classical and instrinisc perspectives on Pin-structures and thus of the equivalence between them established in this monograph. The preface and the introductions to the three parts describe the present work in more detail.

math.DG

A Geometric Depiction of Solomon-Tukachinsky's Construction of Open GW-Invariants

The 2016 papers of J. Solomon and S. Tukachinsky use bounding chains in Fukaya's $A_{\infty}$-algebras to define numerical disk counts relative to a Lagrangian under certain regularity assumptions on the moduli spaces of disks. We present a (self-contained) direct geometric analogue of their construction under weaker topological assumptions, extend it over arbitrary rings in the process, and sketch an extension without any assumptions over rings containing the rationals. This implements the intuitive suggestion represented by their drawing and P. Georgieva's perspective. We also note a curious relation for the standard Gromov-Witten invariants readily deducible from their work. In a sequel, we use the geometric perspective of this paper to relate Solomon-Tukachinsky's invariants to Welschinger's open invariants of symplectic sixfolds, confirming their belief and G. Tian's related expectation concerning K. Fukaya's earlier construction.

math.SG

Solomon-Tukachinsky's vs. Welschinger's Open Gromov-Witten Invariants of Symplectic Sixfolds

Our previous paper describes a geometric translation of the construction of open Gromov-Witten invariants by J. Solomon and S. Tukachinsky from a perspective of $A_{\infty}$-algebras of differential forms. We now use this geometric perspective to show that these invariants reduce to Welschinger's open Gromov-Witten invariants in dimension 6, inline with their and G. Tian's expectations. As an immediate corollary, we obtain a translation of Solomon-Tukachinsky's open WDVV equations into relations for Welschinger's invariants.

math.SG

WDVV-Type Relations for Disk Gromov-Witten Invariants in Dimension 6

The first author's previous work established Solomon's WDVV-type relations for Welschinger's invariant curve counts in real symplectic fourfolds by lifting geometric relations over possibly unorientable morphisms. We apply her framework to obtain WDVV-style relations for the disk invariants of real symplectic sixfolds with some symmetry, in particular confirming Alcolado's prediction for $\mathbb{P}^3$ and extending it to other spaces. These relations reduce the computation of Welschinger's invariants of many real symplectic sixfolds to invariants in small degrees and provide lower bounds for counts of real rational curves with positive-dimensional insertions in some cases. In the case of $\mathbb{P}^3$, our lower bounds fit perfectly with Kollár's vanishing results.

math.SG

WDVV-Type Relations for Welschinger's Invariants: Applications

We first recall Solomon's relations for Welschinger's invariants counting real curves in real symplectic fourfolds, announced in \cite{Jake2} and established in \cite{RealWDVV}, and the WDVV-style relations for Welschinger's invariants counting real curves in real symplectic sixfolds with some symmetry established in \cite{RealWDVV3}. We then explicitly demonstrate that in some important cases (projective spaces with standard conjugations, real blowups of the projective plane, and two- and three-fold products of the one-dimensional projective space with two involutions each), these relations provide complete recursions determining all Welschinger's invariants from basic input. We include extensive tables of Welschinger's invariants in low degrees obtained from these recursions with {\it Mathematica}. These invariants provide lower bounds for counts of real rational curves, including with curve insertions in smooth algebraic threefolds.

math.SG

Steenrod Pseudocycles, Lifted Cobordisms, and Solomon's Relations for Welschinger's Invariants

We establish two WDVV-style relations for the disk invariants of real symplectic fourfolds by implementing Georgieva's suggestion to lift homology relations from the Deligne-Mumford moduli spaces of stable real curves. This is accomplished by lifting judiciously chosen cobordisms realizing these relations. The resulting lifted relations lead to the recursions for Welschinger's invariants announced by Solomon in~2007 and have the same structure as his WDVV-style relations, but differ by signs from the latter. Our topological approach provides a general framework for lifting relations via morphisms between not necessarily orientable spaces.

math.SG

Jenkins-Strebel Differentials on the Riemann Sphere with Four Simple Poles

A celebrated and deep theorem in the theory of Riemann surfaces states the existence and uniqueness of the Jenkins-Strebel differentials on a Riemann surface under some conditions, but the proof is non-constructive and examples are difficult to find. This paper deals with an example of a simple case, namely Jenkins-Strebel differentials on the Riemann sphere with four fixed simple poles. We will give explicit expressions of these Jenkins-Strebel differentials by means of the Weierstrass $\wp$ function and expose a simple algorithm determining the correspondence between these differentials and some classes of simple closed curves on the Riemann sphere with four points removed.

math.CV