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arXiv research

A locally-built, LLM-digested index of recent arXiv papers in quant finance, geometry/topology, and statistical ML — keyword search served straight from SQLite on this machine.

168,695 papers · 148 categories

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3547071,0611,414 · Jun 202019922001200920172026
48 results for unstable models

Ricci flow simulations show unstable Fubini-Study metrics develop singularities.

problem Understanding the behavior of unstable perturbations in Ricci flow.
method Numerical simulations of Ricci flow starting from unstable Fubini-Study metrics.
result Ricci flow solutions from unstable Fubini-Study metrics develop local singularities.

Unstable minimal surfaces are the unstable stationary points of the Dirichlet-Integral. In order to obtain unstable solutions, the method of the gradient flow together with the minimax-principle is generally used. The application of this method for minimal surfaces in the Euclidean spacce was presented in \cite{s3}. We…

2006-03-27abs ↗pdf ↗

Study finds limits for conical Kähler-Einstein metrics on unstable surfaces.

problem Optimal upper bounds for conical Kähler-Einstein metrics on K-unstable del Pezzo surfaces.
method Established optimal upper bounds for cone angles of Kähler-Einstein metrics with conical singularities.
result Optimal upper bounds for conical Kähler-Einstein metrics on K-unstable del Pezzo surfaces.

Algorithm identifies and transfers unstable features to create robust classifiers.

problem Developing unbiased classifiers from input-label pairs alone.
method Contrast different data environments in source tasks to encode unstable features, then cluster target task data and minimize worst-case risk.
result Our method maintains robustness across synthetic and real-world environments.

CV inference can be invalid for relatively unstable model comparisons.

problem The validity of cross-validation for model comparison is questioned when models are relatively unstable.
method The study proves that simple, individually stable models can generate relatively unstable comparisons, invalidating CV inference.
result The Lasso and soft-thresholding generate relatively unstable comparisons, invalidating CV inferences.

Unstable minimal surfaces in n-space link to hyperbolic products.

problem Characterizing unstable minimal surfaces in Rn\mathbb{R}^n and their product counterparts.
method Lifting to R\mathbb{R}-trees, deforming to hyperbolic products, and proving instability equivalence.
result Unstable minimal surfaces in Rn\mathbb{R}^n imply unstable surfaces in product hyperbolic spaces.

Because of their tractability and their natural interpretations in term of market quantities, Hawkes processes are nowadays widely used in high-frequency finance. However, in practice, the statistical estimation results seem to show that very often, only nearly unstable Hawkes processes are able to fit the data properl…

2013-10-08abs ↗pdf ↗

Segre varieties' hyperplane sections are unstable under certain conditions.

problem Stability of hyperplane sections of Segre varieties under different conditions.
method Proving instability with respect to any polarization for non-smooth or meqnm eq n cases.
result Normal hyperplane sections of Segre varieties are K-unstable under specified conditions.

Survey of computations for Riemann surface moduli spaces, focusing on unstable homology.

problem Computing unstable homology of moduli spaces of Riemann surfaces.
method Integral, mod-2, and rational coefficient computations; use of homology operations.
result Explicit generators of unstable homology for most cases determined.

SFB uses stable features to adapt unstable ones for better performance.

problem Improving classifier performance on out-of-distribution data by leveraging stable features.
method SFB learns a predictor that separates stable and unstable features, then adapts unstable predictions using stable predictions.
result SFB can learn an asymptotically-optimal predictor without test-domain labels.

We construct an inverse system of unstable Vassiliev spectral sequences on the spaces of plumbers' knots, which model the homotopy type of the space of long knots, and show that the limit of these sequences contains the finite type invariants in their usual complexity. Utilizing the cell structure on the discriminant o…

2011-07-23abs ↗pdf ↗

In this paper, we introduce a non linear ODE method to construct CMC surfaces in Riemannian manifolds with symmetry. As an application we construct unstable CMC spheres and outlying CMC spheres in asymptotically Schwarzschild manifolds with metrics like gij=(1+1l)2δij+O(l2)g_{ij}=(1+\frac{1}{l})^{2}δ_{ij}+O(l^{-2}). The existence of uns…

2015-07-10abs ↗pdf ↗

New proof associates partitions to isotopic pseudo-Anosov homeomorphisms.

problem Stable and unstable foliations for pseudo-Anosov homeomorphisms.
method Geometric realization of Fathi's result for isotopic homeomorphisms.
result Associated stable and unstable partitions for isotopic pseudo-Anosov homeomorphisms.

This article deals with stability issues related to geodesic X-ray transforms, where an interplay between the (attenuation type) weight in the transform and the underlying geometry strongly impact whether the problem is stable or unstable. In the unstable case, we also explain what types of artifacts are expected in te…

2017-08-29abs ↗pdf ↗

The paper proves regularity of states on manifolds with unstable dynamics.

problem Propagation of regularity in dynamical systems with unstable manifolds.
method Leafwise semiclassical pseudodifferential calculus adapted to foliated spaces.
result Pollicott-Ruelle resonant states are smooth over entire manifolds if smooth on unstable leaves.

We give examples of smooth surfaces with negative first Chern class which are slope unstable with respect to certain polarisations, and so have Kahler classes that do not admit any constant scalar curvature Kahler metrics. We also compare this to the work of Song-Weinkove on the J-flow.

2005-06-22abs ↗pdf ↗

We construct Hodge filtered function spaces associated to infinite loop spaces. For Brown-Peterson cohomology, we show that the corresponding Hodge filtered spaces satisfy an analog of Wilson's unstable splitting. As a consequence, we obtain an analog of Quillen's theorem for Hodge filtered Brown-Peterson cohomology fo…

2016-10-25abs ↗pdf ↗

The paper shows measures equidistribute on affine submanifolds with a rate.

problem Understanding equidistribution of measures on affine invariant submanifolds.
method Analyzing unstable foliations and using results from homogeneous dynamics.
result Measures of large dimension equidistribute on affine invariant submanifolds with an effective rate.

The paper explores maximal destabilizers for both K-stability and Chow-stability in unstable situations.

problem Exploring maximal destabilizers for K-stability and Chow-stability in unstable situations.
method Using non-Archimedean pluripotential theory and idealistic assumptions, the paper provides a route to show that maximal K-destabilizers are quantized by maximal Chow-destabilizers.
result Maximal K-destabilizers are quantized by maximal Chow-destabilizers.

MeanFlow training is unstable due to misusing conditional velocity, leading to variance issues.

problem Unstable training of MeanFlow due to variance problems.
method Theoretical analysis and derivation of optimal coefficient in closed form.
result The optimal coefficient in MeanFlow training minimizes variance but not necessarily quality.

The Ricci flow on the 2-sphere with marked points is shown to converge in all three stable, semi-stable, and unstable cases. In the stable case, the flow was known to converge without any reparametrization, and a new proof of this fact is given. The semi-stable and unstable cases are new, and it is shown that the flow …

2014-07-04abs ↗pdf ↗

In this paper, we derive the second variation formula of pseudoharmonic maps into any pseudo-Hermitian manifolds. When the target manifold is an isometric embedded CR manifold in complex Euclidean space or a pseudo-Hermitian immersed submanifold in Heisenberg group, we give some conditions on Weingarten maps to obtain …

2014-02-27abs ↗pdf ↗

Ancient mean curvature flows start from unstable minimal hypersurfaces.

problem Constructing ancient solutions to mean curvature flow.
method From an unstable minimal hypersurface with finite total curvature in \(\mathbb{R}^{n+1}\), we construct \(I\)-dimensional families of embedded ancient solutions.
result Ancient solutions arise from unstable minimal hypersurfaces.

We study the stability of capillary hypersurfaces in a unit Euclidean ball. It is proved that if the mass center of the generalized body enclosed by the immersed capillary hypersurface and the wetted part of the sphere is located at the origin, then the hypersurface is unstable. An immediate result is that all known ex…

2014-08-09abs ↗pdf ↗

Improves test set performance and reduces out-of-sample disappointment for unstable models.

problem Ensuring strong test set performance via cross-validation for unstable models.
method Nested k-fold cross-validation with hyperparameter selection based on a weighted sum of cross-validation metric and model stability measure.
result Improves out-of-sample MSE for sparse ridge regression and CART by 4% and 2% respectively, compared to k-fold cross-validation.

New Calabi-Yau metrics with conical singularities are created near complex lines.

problem Creating Calabi-Yau metrics with conical singularities near complex lines.
method Using branched covering arguments to construct metrics with conical singularities.
result Calabi-Yau metrics with unstable conical singularities are successfully created.

Nearly G2G_2-structures are unstable under a modified G2G_2-Laplacian co-flow.

problem Stability of nearly G2G_2-structures under geometric flows.
method Normalized modified G2G_2-Laplacian co-flow.
result Many nearly G2G_2-structures are unstable, with the standard structure on the round 7-sphere being an unstable critical point.

Being inspired by Ross' construction of unstable products of certain smooth curves, we show that the product C×CC\times C of every smooth curve CC of genus at least 2 is not slope semistable with respect to certain polarisations. Besides, we produce examples of Kodaira-fibred surfaces of nonzero signature, which are no…

2006-12-19abs ↗pdf ↗

Conjecture 1 of Stanley Chang: "Positive scalar curvature of totally nonspin manifolds" asserts that a closed smooth manifold M with non-spin universal covering admits a metric of positive scalar curvature if and only if a certain homological condition is satisfied. We present a counterexample to this conjecture, based…

2011-02-14abs ↗pdf ↗

We consider the Riemannian functional defined on the space of Riemannian metrics with unit volume on a closed smooth manifold MM given by Rn2(g):=MR(g)n2dvg\mathcal{R}_{\frac{n}{2}}(g):= \int_M |R(g)|^{\frac{n}{2}}dv_g where R(g)R(g), dvgdv_g denote the Riemannian curvature and volume form corresponding to gg. We show that there are lo…

2012-11-25abs ↗pdf ↗