Study isotropy groups for complex orthogonal and skew-symmetric matrices.
problem Understanding isotropy subgroups of orthogonal similarity transformations.
method Analysis of group structure of nonsingular block matrices.
result Group structure of isotropy subgroups related to block Toeplitz matrices.
Study the geometric properties of skew symmetric matrices and orthogonal groups.
problem Understanding the geometric properties of skew symmetric matrices and orthogonal groups.
method Investigate the differential-geometric properties of the exponential map and Riemannian structure.
result Connections between skew symmetric matrices and orthogonal groups are revealed.
Minimal submanifolds in matrix spaces proven for specific ranks.
problem Minimal submanifolds in matrix spaces.
method Proving semialgebraic sets of matrices are minimal.
result Rectangular, skew-symmetric, and symmetric matrices with prescribed eigenvalues are minimal.
Paper extends matrix inequality to Hermitian matrices.
problem Extending inequalities to Hermitian matrices.
method Using Frobenius norm of commutators for real and skew matrices, extending to Hermitian and skew-Hermitian.
result DDVV-type inequalities now apply to Hermitian matrices.
Paper introduces skew-symmetric matrices for virtual doodle classification.
problem Classifying virtual doodles and distinguishing non-classical doodles.
method Use skew-symmetric augmented matrices and homology intersection number.
result Characterization of virtualization of classical doodles.
A new method for efficiently computing derivatives of skew-symmetric matrix exponentials.
problem Efficient computation of derivatives for skew-symmetric matrices.
method Characterization of invertibility, construction of nearby logarithm, and efficient implementation.
result Explicit formulae for differentiation and its inverse of skew-symmetric matrix exponentials.
Characterizes the local diffeomorphism structure of the exponential in the set of skew-symmetric matrices.
problem Characterizing the local diffeomorphism structure of the exponential in the set of skew-symmetric matrices.
method Introduce the diffeomorphic logarithm of special orthogonal matrices and an efficient algorithm.
result The region containing the principal logarithm has a special multiplicity structure.
In this paper, we will first derive a DDVV-type optimal inequality for real skew-symmetric matrices, then we apply it to establish a Simons-type integral inequality for Riemannian submersions with totally geodesic fibres and Yang-Mills horizontal distributions. In this way, we show phenomenons of duality between Subman…
The paper extends matrix inequalities to various types of matrices.
problem Generalizing inequalities for different types of matrices.
method Extending known inequalities for real, complex, and quaternionic matrices.
result New inequalities for matrices in subspaces spanned by Clifford systems or algebras.
A necessary condition for a connection in a vector bundle to be locally metric is for its curvature matrix, which consists of 2 forms, to be skew symmetric with respect to some local frame. In this paper we give a simple algorithm that can be used to decide when a matrix of 2 forms is equivalent to a skew symmetric…
Study embeds PC matrices into Grassmannian manifold for geometric interpretation.
problem Understanding algebraic consistency of pairwise comparisons matrices.
method Leverages Plücker coordinates and geometric interpretation of Grassmannian manifold.
result Algebraic consistency condition is equivalent to geometric consistency in G(2,n). The paper connects Riemannian Gaussian distributions to random matrix theory and diffusion kernels.
problem Analyzing Riemannian Gaussian distributions on symmetric spaces.
method Analytical computation of marginals using orthogonal and skew orthogonal polynomials, and diffusion kernels.
result Riemannian Gaussian distributions are random matrix types, and their probability density functions can be computed analytically.
Complete classification of quaternionic skew-Hermitian symmetric spaces found.
problem Classifying quaternionic skew-Hermitian symmetric spaces.
method Proving the existence of a torsion-free mSO∗(2n)mSp(1)-structure and showing that any homogeneous space is symmetric. result A complete classification of quaternionic skew-Hermitian symmetric spaces for arbitrary n>1. The paper defines symmetric brackets for skew-symmetric algebroids with totally skew-symmetric torsion.
problem Defining symmetric brackets for skew-symmetric algebroids.
method Using connections with totally skew-symmetric torsion and pseudo-Riemannian metrics.
result Explicit formula for the Levi-Civita connection and symmetric brackets on almost Hermitian manifolds.
Minimal spectral radii found for specific matrix types.
problem Finding smallest spectral radii for certain matrix classes.
method Analyzing skew-reciprocal integer matrices of fixed even dimensions.
result Most classes of matrices have smaller spectral radii than their reciprocal counterparts.
The paper studies geometries with parallel skew-symmetric torsion and their submersions.
problem Understanding geometries with parallel skew-symmetric torsion.
method Analyzing metric connections and submersions.
result Complete local classification of geometries with parallel skew-symmetric torsion in principal bundle cases.
For a positive definite fundamental tensor all known examples of Osserman algebraic curvature tensors have a typical structure. They can be produced from a metric tensor and a finite set of skew-symmetric matrices which fulfil Clifford commutation relations. We show by means of Young symmetrizers and a theorem of S. A.…
Defines strongest integrability condition for skew-symmetric endomorphisms.
problem Integrability conditions for skew-symmetric endomorphisms.
method Characterization of the shifted Courant-Nijenhuis torsion.
result Vanishing of the shifted Courant-Nijenhuis torsion as the strongest integrability condition.
A parsimonious model reduces over-parameterization in skewed matrix variate mixtures.
problem Over-parameterization in skewed matrix variate mixtures.
method Parsimonious family of 256 models using bilinear factor analyzers constrained over clusters, with AECM algorithm for estimation.
result Extensive simulations and real-world datasets (MNIST, Olivetti faces) demonstrate the method's effectiveness.
Proposes vMF distribution for skewed elliptical distributions.
problem Skewed distributions not adequately modeled by symmetric distributions.
method Introduces von-Mises-Fisher (vMF) distribution to represent skewed elliptical distributions.
result vMF distribution provides an explicit and simple probability representation of skewed elliptical distributions.
Study various submanifolds in quaternionic skew-Hermitian spaces.
problem Characterize submanifolds in almost quaternionic skew-Hermitian manifolds.
method Construct explicit examples of submanifolds in semisimple quaternionic skew-Hermitian symmetric spaces.
result Explicit examples of submanifolds for each type considered.
New model for pairwise comparisons without stochastic transitivity.
problem Suboptimal performance of models assuming stochastic transitivity in real-world scenarios.
method Proposes a general family of statistical models using a skew-symmetric matrix.
result Achieves minimax-rate optimality and adapts to data sparsity.
A new geometric method for clustering SPD data improves upon Euclidean and Riemannian approaches.
problem Skewed interpretations of SPD data in Euclidean analysis and computational inefficiency of Riemannian methods.
method Proposes a geometric method based on the Thompson metric for unsupervised clustering of SPD data.
result Demonstrates improved clustering results using inductive midrange centroid computation.
Counterexample found to estimate for skew-symmetric tensors.
problem Estimate for skew-symmetric tensors was claimed and used for classification results.
method Analysis of the estimate in arXiv:2103.15482.
result Counterexample disproves the estimate for skew-symmetric tensors.
Unified approach to decomposing commutative n-ary superalgebras with skew-symmetric forms.
problem Decomposing commutative n-ary superalgebras with skew-symmetric invariant forms.
method Unified approach using derived bracket formalism and inductive orthogonal sums and generalized double extensions.
result Any commutative n-ary superalgebra with a skew-symmetric invariant form can be obtained by inductive orthogonal sums and generalized double extensions.
We classify the connected pseudo-Riemannian manifolds of signature (p,q) with q≥5 so that at each point of M the skew-symmetric curvature operator has constant rank 2 and constant Jordan normal form on the set of spacelike 2 planes and so that the skew-symmetric curvature operator is not nilpotent for at least …
We study Spin(9)-structures on 16-dimensional Riemannian manifolds and characterize the geometric types admitting a connection with totally skew-symmetric torsion.
This work accelerates constrained sampling using large deviation principles.
problem Sampling constrained probability distributions efficiently.
method Large deviation principles applied to skew-reflected non-reversible Langevin dynamics.
result The skew-symmetric matrix accelerates convergence and reduces asymptotic variance.
Study constructs totally geodesic submanifolds in skew position.
problem Constructing totally geodesic submanifolds in skew position.
method Used Cartan representations of SO(3), SU(3), and Sp(3) to construct submanifolds. result Constructed totally geodesic submanifolds in complex quadrics, complex 2-Grassmannians, and quaternionic 2-Grassmannians.
scoRNN improves RNN performance with simpler orthogonal weight matrices.
problem Vanishing and exploding gradients in RNNs.
method Parametrizing orthogonal recurrent weight matrices with a scaled Cayley transform.
result scoRNN achieves superior results with fewer parameters than other unitary RNNs.
We prove a Berger-type theorem which asserts that if the orthogonal subgroup generated by the torsion tensor (pulled back to a point by parallel transport) of a metric connection with skew-symmetric torsion is not transitive on the sphere, then the space must be locally isometric to a Lie group with a bi-invariant metr…
Some known results on torsionfree connections with skew-symmetric Ricci tensor on surfaces are extended to connections with torsion, and Wong's canonical coordinate form of such connections is simplified.
The paper studies vanishing cycles in matrix singularities.
problem Understanding the topology of singular Milnor fibers of matrix families.
method Definition and analysis of vanishing cycles, proof of conjectures, study of monodromy.
result Proof of an extended Damon-Pike μ=τ conjecture for special matrix families.
Adaptive algorithm improves convergence rate of Langevin dynamics.
problem Improving convergence rate of Langevin dynamics.
method Adaptive non-reversible stochastic gradient Langevin dynamics algorithm.
result Improved convergence rate of the algorithm.
We study Nijenhuis structures on Courant algebroids in terms of the canonical Poisson bracket on their symplectic realizations. We prove that the Nijenhuis torsion of a skew-symmetric endomorphism N of a Courant algebroid is skew-symmetric if the square of N is proportional to the identity, and only in this case when t…
Study reveals hidden structure behind Racah matrices for twisted knots.
problem Understanding non-associativity in representation products of twisted knots.
method Analysis of quantum R-matrices and their eigenvalues to decompose Racah matrices.
result Discovery of pentad structure (Tˉ,Sˉ,S,E,B) associated with universal R-matrix. We construct almost complex algebraic curvature tensors for pseudo Hermitian inner products whose skew-symmetric curvature operator has constant Jordan normal form on the set of non-degenerate complex lines.
Study classifies Hamiltonian operators with skew-symmetric constraints.
problem Classifying Hamiltonian operators with skew-symmetric constraints.
method Using Poisson vertex algebras and differential-geometric constraints.
result Complete classification results for 2-component and 3-component cases.
Classifies 4D metric Lie algebras with parallel skew-symmetric tensors.
problem Classifying 4D metric Lie algebras with parallel skew-symmetric tensors.
method Complete classification up to isometric isomorphism and scaling.
result Classification of 4D metric Lie algebras with parallel skew-symmetric tensors.
We study almost Hermitian structures admitting a Hermitian connexion with totally skew-symmetric torsion or equivalently, those almost Hermitian structures with totally skew-symmetric Nijenhuis tensor. We investigate up to what extent the Nijenhuis tensor fails to be parallel with respect to the characteristic connexio…
For any triple (Mn,g,∇) consisting of a Riemannian manifold and a metric connection with skew-symmetric torsion we introduce an elliptic, second order operator Ω acting on spinor fields. In case of a reductive space and its canonical connection our construction yields the Casimir operator of the isometry gr…
For n≥1, the twistor space Z(S2n) of the conformal 2n-sphere is biholomorphic to the Zariski closure, taken in the complex Grassmannian manifold G(n+1,2n+2), of the set of graphs of skew-symmetric linear endomorphism of Cn+1. We use this fact to describe a nat…
We study n-ary commutative superalgebras and L∞-algebras that possess a skew-symmetric invariant form, using the derived bracket formalism. This class of superalgebras includes for instance Lie algebras and their n-ary generalizations, commutative associative and Jordan algebras with an invariant form. We…
This paper classifies 4D spin manifolds with skew Killing spinors.
problem Classifying 4D Riemannian spin manifolds with skew Killing spinors.
method Analyzing skew Killing spinors with skew-symmetric endomorphisms A, considering both degenerate and non-degenerate cases.
result In the degenerate case, the manifold is locally isometric to R x N with N having a skew Killing spinor.
Classifies 7D manifolds with specific geometric properties.
problem Classifying 7D manifolds with parallel skew-symmetric torsion and G2 holonomy. method Extending Friedrich's work, using classification techniques for naturally reductive spaces and nearly parallel G2-structures. result Complete classification of 7D manifolds with the specified properties.
We develop various properties of symmetric generalized complex structures (in connection with their holomorphic space and B-field transformations), which are analogous to the well-known results of Gualtieri on skew-symmetric generalized complex structures. Given a symmetric or skew-symmetric generalized complex structu…
New connections on 5-manifolds linked to Sasaki-Einstein structures.
problem Finding connections on 5-manifolds with specific properties.
method Using skew-symmetric torsion and Einstein metricity conditions.
result Existence of connections on 5-manifolds is equivalent to the existence of Sasaki-Einstein 5-manifolds.
In the present work we consider an almost complex manifold with Norden metric (i.e. a metric with respect to which the almost complex structure is an antiisometry). On such a manifold we study a linear connection preserving the almost complex structure and the metric and having a totally skew-symmetric torsion tensor. …