Ricci solitons as critical points of quadratic curvature functionals
problem Einstein metrics and Ricci solitons as critical points of quadratic Riemannian functionals
method Study of Ricci solitons as critical points of a special quadratic curvature functional
result Ricci solitons are non-Einstein critical points of these functionals
New rigidity results for critical metrics of a quadratic curvature functional.
problem Proving uniqueness of critical metrics for a specific curvature functional.
method Analyzing complete, possibly non-compact, critical metrics of the quadratic curvature functional.
result Critical metrics with finite energy are scalar flat (global minima) for dimensions n≥10.
Researchers found all special metrics in 4D for certain curvature functionals.
problem Identifying special metrics in 4D for quadratic curvature functionals.
method Determined all homogeneous metrics that are critical for quadratic curvature functionals.
result All homogeneous metrics in 4D for some quadratic curvature functionals have been identified.
Proves transitivity of a specific class of quadratic polynomials.
problem Transitivity of pure Hurwitz classes of post-critically finite quadratic polynomials.
method Uses mapping classes of the sphere with finitely many marked points.
result Establishes transitivity for pure Hurwitz classes of post-critically finite quadratic polynomials.
The paper proves rigidity of Einstein metrics as critical points of quadratic curvature functionals.
problem Characterizing Einstein metrics as critical points of quadratic functionals.
method Analyzing Einstein metrics on closed manifolds using quadratic curvature functionals and point-wise inequalities.
result Rigidity results for Einstein metrics involving Weyl curvature, trace-less Ricci curvature, and Yamabe invariant.
The study classifies critical metrics on manifolds with specific curvature conditions.
problem Characterizing critical metrics for quadratic curvature functionals.
method Analyzing closed n-dimensional manifolds with Ricci, scalar curvature, and Riemannian curvature tensor.
result Critical metrics are Einstein under certain curvature conditions.
In this paper we prove rigidity results on critical metrics for quadratic curvature functionals, involving the Ricci and the scalar curvature, on the space of Riemannian metrics with unit volume. It is well-known that Einstein metrics are always critical points. The purpose of this article is to show that, under some c…
The paper proves new rigidity results for critical metrics of quadratic curvature functionals.
problem Proving rigidity of critical metrics for specific quadratic curvature functionals.
method Rigidity results for conformal vector fields, ODE argument, and new pointwise and integral estimates.
result Critical metrics are rigid under specific conditions.
Actor-critic converges globally in LQR with ergodic cost.
problem Theoretical understanding of actor-critic algorithm's global convergence.
method Nonasymptotic convergence analysis of actor-critic in linear quadratic regulator (LQR) setting.
result Actor-critic finds globally optimal policy and value function at a linear rate.
Study rigidity of Einstein metrics as critical points of curvature functionals.
problem Characterize Einstein metrics as critical points of quadratic curvature functionals.
method Analyze pointwise inequalities involving Weyl curvature and traceless Ricci curvature.
result Provide rigidity results for Einstein metrics and locally conformally flat critical metrics.
Critical graphs of quadratic differentials equidistribute in moduli space.
problem Distribution of critical graphs in moduli space.
method Study of Jenkins-Strebel differentials and their critical graphs.
result Critical graphs equidistribute to the Kontsevich measure.
Global convergence proved for multi-agent LQRs with hierarchical actor-critic.
problem Challenges in understanding multi-agent reinforcement learning algorithms.
method Developed a hierarchical actor-critic algorithm for partially exchangeable agents.
result Global linear convergence to optimal policy proved.
Actor-critic finds Nash in mean-field games with linear-quadratic costs.
problem Finding Nash equilibrium in mean-field Markov games with linear dynamics and quadratic costs.
method Mean-field actor-critic algorithm with linear function approximation.
result Algorithm converges linearly to Nash equilibrium.
Critical metrics on four-dimensional manifolds are either Einstein or product of two-dimensional manifolds.
problem Classifying critical metrics of a curvature functional on complete four-dimensional manifolds.
method Analyzing the curvature operator and energy condition to prove metric properties.
result Complete four-dimensional manifolds with finite energy are either Einstein or product of two-dimensional manifolds.
New rigidity results for critical metrics with curvature pinching.
problem Understanding critical metrics with curvature pinching conditions.
method Proving rigidity for metrics defined on closed smooth manifolds that are critical for a quadratic functional.
result Bach-flat metrics with constant scalar curvature satisfying Sec > 1/48 R are Einstein and isometric to specific spaces.
Study shows augmented deformation space of rational maps is disconnected.
problem Understanding the structure of rational maps with specific dynamics.
method Examined the augmented deformation space of a family of quadratic rational maps.
result The closure of the deformation space in the augmented space is also disconnected.
We obtain a unified theory of discrete minimal surfaces based on discrete holomorphic quadratic differentials via a Weierstrass representation. Our discrete holomorphic quadratic differential are invariant under Möbius transformations. They can be obtained from discrete harmonic functions in the sense of the cotangent …
The paper examines rigidity of Einstein metrics using curvature functionals.
problem Characterizing rigidity of Einstein metrics.
method Critical points of quadratic curvature functionals and integral inequalities involving Weyl curvature, trace-less Ricci curvature, and Sobolev constant.
result Rigidity results for Einstein metrics on complete manifolds.
Study shows how algorithmic choices affect optimal batch sizes in neural networks.
problem Understanding how batch size impacts neural network training efficiency.
method Experiments and analysis of a simple quadratic model to study algorithmic choices.
result Preconditioned optimizers like Adam and K-FAC allow larger batch sizes before diminishing returns.
We investigate rigidity and stability properties of critical points of quadratic curvature functionals on the space of Riemannian metrics. We show it is possible to "gauge" the Euler-Lagrange equations, in a self-adjoint fashion, to become elliptic. Fredholm theory may then be used to describe local properties of the m…
We show that any global solution to the special Lagrangian equations with the phase larger than a critical value must be quadratic.
In this paper we investigate the properties of a semi-linear problem on a spin manifold involving the Dirac operator, through the construction of Rabinowitz-Floer homology groups. We give several existence results for sub-critical and critical non-linearities as application of the computation of the different homologie…
Study on stability of curvature functionals on manifolds.
problem Stability of quadratic curvature functionals on manifolds.
method Analysis of stability at constant sectional curvature metrics.
result Stability properties of quadratic curvature functionals.
New Morse-Bott function defined on Stiefel manifolds, revealing complex critical structures.
problem Defining Morse-Bott functions on non-linear Stiefel manifolds.
method Replacing linear height function with a quadratic one, proving it as a Morse-Bott function.
result Critical submanifolds are fibrations of products of Grassmannians, not Grassmannians themselves.
Paper examines stability of quadratic curvature functionals on product Einstein manifolds.
problem Understanding stability of critical points of quadratic curvature functionals on product Einstein manifolds.
method Analyzes Riemannian functionals defined by L2-norms of Ricci, scalar, Weyl, and Riemannian curvatures. result Product of a spherical space form and a compact hyperbolic manifold is unstable for some quadratic functionals if the first eigenvalue of the Laplacian of the hyperbolic manifold is sufficiently small.
Study Morse-Bott functions on orthogonal groups, computing Betti numbers.
problem Computing Betti numbers of orthogonal groups using Morse-Bott functions.
method Detailed analysis of quadratic and linear Morse-Bott trace functions on O(n), using critical loci and indices. result New Morse-theoretic computation of mod 2 Betti numbers of SO(n). Calibrates Hawkes models for market events, revealing power-law feedback kernels.
problem Estimating the influence of past events and price changes on future market events.
method Proposes a calibration procedure for Quadratic Hawkes models, analyzing the kernel components.
result Empirically calibrated kernel components reveal power-law behavior, suggesting system near critical point.
We describe a graph parametrization of rational quadratic differentials with presence of a simple pole, whose critical trajectories form a network depending on parameters focusing on the network topological jumps. Obtained bifurcation diagrams are associated with the Stasheff polytopes.
The paper classifies Weyl tensors in Riemannian 4-manifolds via Lorentzian deformation.
problem Classifying Weyl tensors in Riemannian 4-manifolds.
method Deforming the metric into a Lorentzian one via a nonzero vector T. result Only Petrov Types I and D can occur, and each is determined by the number of critical points of the associated Lorentzian quadratic form.
EPG unifies SPG and DPG for reinforcement learning.
problem Improving reinforcement learning algorithms for policy optimization.
method EPG integrates across actions for gradient estimation, using practical results for Gaussian policies and extending to broader classes of policies.
result EPG reduces gradient variance without deterministic policies and with minimal overhead.
Researchers confirm scalar-flatness for critical metrics in 5-9 dimensions.
problem Verifying scalar-flatness for critical metrics in specific dimensions.
method Analyzing complete Riemannian manifolds with critical metrics of the L2-scalar curvature functional. result The conjecture that all complete noncompact critical metrics with finite energy are scalar-flat is confirmed for dimensions 5 to 9.
Reinforcement learning for continuous-time risk-sensitive asset allocation
problem Continuous-time risk-sensitive asset allocation
method Free energy-entropy duality reformulation and q-learning actor-critic method result Optimal policy learning with high accuracy
New connection found between complex polynomials and surface homeomorphisms.
problem Investigating the existence of generalized pseudo-Anosov maps from quadratic polynomials.
method Developed a new connection between dynamics of quadratic polynomials and surface homeomorphisms, focusing on Hubbard trees.
result Identified conditions for constructing generalized pseudo-Anosov maps from quadratic polynomials.
Study on finite energy SU(2) monopoles on AC 3-manifolds, proving integrality of charge and curvature decay.
problem Understanding the asymptotic behavior of finite energy SU(2) monopoles on AC 3-manifolds.
method Analysis of critical points of the SU(2) Yang--Mills--Higgs energy on asymptotically conical 3-manifolds.
result Proves integrality of the monopole number and quadratic decay of curvature, among other findings.
Study uses actor-critic method for continuous-time mean-field control with entropy regularisation.
problem Continuous-time mean-field control in reinforcement learning.
method Actor-critic approach with entropy regularisation, value function alternation, and Wasserstein space parametrisation.
result Derives exact parametrisation of actor and critic functions in linear-quadratic mean-field framework.
Study of energy quantization in a nonlinear sigma model with critical gravitinos.
problem Analyzing properties of a nonlinear sigma model with gravitinos in string theory.
method Analytical and geometric properties, Pohozaev type identity, weakly convergent sequence of fields.
result Established energy identities and obtained a holomorphic quadratic differential.
Paper develops methods for non-quadratic loss low-rank matrix recovery.
problem Recovery of low-rank matrices with non-quadratic losses.
method Projected gradient method with a regularity projection oracle.
result Projected gradient method converges globally and linearly.
We introduce and establish the main properties of QHawkes ("Quadratic" Hawkes) models. QHawkes models generalize the Hawkes price models introduced in E. Bacry et al. (2014), by allowing all feedback effects in the jump intensity that are linear and quadratic in past returns. A non-parametric fit on NYSE stock data sho…
New algorithm solves mean-field control problems using actor-critic learning with moment neural networks.
problem Solving mean-field control problems in continuous time reinforcement learning.
method Gradient-based policy and value function learning with moment neural networks on the Wasserstein space.
result Effective solution for diverse mean-field control problems, including multi-dimensional and nonlinear settings.
Uniform bounds found for Sierpinski carpet hyperbolic components.
problem Bounding hyperbolic components of Sierpinski carpet type.
method Establishing uniform a priori bounds and analyzing quadratic-like restrictions.
result Sierpinski carpet hyperbolic components of disjoint type are bounded.
Catapult phase in neural nets shows exponential loss growth before quick decrease.
problem Understanding phase transitions in neural networks during training.
method Analyzing weight norm and loss behavior for super-critical learning rates.
result Proven existence of catapult phase in quadratic models and two-layer nets.
Paper provides estimates for varifolds with critical mean curvature.
problem Estimating tilt-excess on varifolds with critical mean curvature.
method Generalizing Lipschitz approximation and Sobolev-Poincaré estimates to almost-integral rectifiable varifolds.
result VMO-type estimates for quadratic tilt-excess on varifolds with critical mean curvature.
A new method automatically and dynamically sets learning rates in deep learning.
problem Determining the appropriate learning rate in deep learning tasks is challenging and often subjective.
method Local Quadratic Approximation (LQA) to automatically and dynamically set learning rates.
result The proposed method leads to nearly optimal learning rates in a computationally efficient way.
New bounds on random quadratic forms hold under dependence, useful for adaptive modeling.
problem Need for independence in bounds on random quadratic forms.
method Uniform bounds on random quadratic forms of conditionally independent and sub-Gaussian stochastic processes.
result Bounds hold under general dependencies and sequential design.
We propose a strategy for approximating Pareto optimal sets based on the global analysis framework proposed by Smale (Dynamical systems, New York, 1973, pp. 531-544). The method highlights and exploits the underlying manifold structure of the Pareto sets, approximating Pareto optima by means of simplicial complexes. Th…
We review geometrical properties of a static spacetime (M,g), including geodesic completeness, causality, standard splittings, compact M, closed geodesics and geodesic connectedness. We pay special attention to the critical quadratic behavior at infinity of the coefficients β, β−1 (β=−g(K,K), being K a …
Let (Σ,p) be a pointed Riemann surface of genus g≥1. For any integer k≥1, we parametrize the space of meromorphic quadratic differentials on Σ with a pole of order (k+2) at p, having a connected critical graph and an induced metric composed of k Euclidean half-planes. The parameters form a finite-…
Let S be a nonexceptional oriented surface of finite type. We construct an uncountable family of probability measures on the space of area on holomorphic quadratic differentials over the moduli space for S containing the usual Lebesgue measure. These measures are invariant under the Teichmueller geodesic flow, and they…