Semisimple Lie groups act transitively on pseudo-Riemannian manifolds, making them flat.
problem Understanding actions of semisimple Lie groups on pseudo-Riemannian manifolds.
method Analyzing the pseudo-Riemannian Lichnerowicz conjecture in homogeneous settings.
result Compact pseudo-Riemannian manifolds on which a semisimple group acts conformally, essentially and transitively, are conformally flat.
Every finite dimensional real representation of a compact real semisimple Lie algebra determines a metric 2-step nilpotent Lie algebra and a corresponding simply connected metric 2-step nilpotent Lie group N. We study the differential geometry of N using representation theory of the complexified complex semisimple Lie …
The study extends Dehn filling to Lie groups, ensuring geometric properties.
problem Generalizing Dehn filling to semisimple Lie groups.
method Analyzing deformations of subgroups and their geometric properties.
result Extended geometrically finite subgroups can be deformed while maintaining properties.
We show that, in compact semisimple Lie groups and Lie algebras, any neighbourhood of the identity gets mapped, under the commutator map, to a neighbourhood of the identity.
Characterizes metrics on Lie groups, proving non-simultaneous existence of balanced and pluriclosed metrics.
problem Existence of balanced and pluriclosed metrics on real semisimple Lie groups.
method Characterization using Vogan diagrams and revisiting complex structure classification.
result Complex manifolds cannot simultaneously admit balanced and pluriclosed metrics.
Proves cohomology of elliptic structures on Lie groups can be algebraic.
problem Computing cohomology of elliptic structures on compact semisimple Lie groups.
method Used spectral sequences to construct an isomorphism between left-invariant and usual differential complexes.
result Reduced analytical problem to algebraic computation.
Classifies semisimple symmetric contact spaces under Lie groups.
problem Classifying contact manifolds with specific symmetry properties.
method Homogeneous classification under semisimple Lie groups with contact symmetry.
result Classification of contact manifolds with semisimple symmetry.
The paper proves estimates for Hodge Laplacians on Lie groups.
problem Estimating Hodge Laplacians on semisimple Lie groups.
method Proves Schwartz estimates for Hodge Laplacian and Dirac operators.
result Generalizes results on symmetric spaces to Lie groups.
Study shows singularity of stationary measure on Furstenberg boundary for certain random walks.
problem Singularity of stationary measure on Furstenberg boundary for random walks.
method Analysis of random walks on semisimple Lie groups with specific properties.
result Stationary measure is singular to Lebesgue measure in certain cases.
Study of hyperkahler spaces from Lie algebras.
problem Understanding hyperkahler quotients of cotangent bundles.
method Analyzing stratified spaces of cotangent bundles of complex semisimple Lie groups.
result Explicit description of partial order on strata using Lie theoretic data.
Study proper actions of Lie groups on symmetric spaces, finding rigidity results and Hurwitz-Radon numbers.
problem Proper actions of non-compact semisimple Lie groups on pseudo-Riemannian symmetric spaces.
method Analysis of symmetric spaces and rigidity results.
result Any connected non-compact semisimple Lie group acting properly on these spaces must be globally isomorphic to Spin(n,1) up to compact factors. Geometric proof for lattice rigidity in Lie groups.
problem Local rigidity of lattices in semisimple Lie groups.
method Geometric proof of well-known results.
result Classical local rigidity of lattices proven geometrically.
Study confirms optimal bounds for group cohomology of Lie groups.
problem Optimal bounds for group cohomology of Lie groups.
method Combining complementary vanishings with spectral sequences and quasi-isometry invariance.
result Non-vanishing of group Lp-cohomology for large p and equal degree to rank. We describe a class (called regular) of invariant generalized complex structures on a real semisimple Lie group G. The problem reduces to the description of admissible pairs (\gk, ω), where \gk is an appropriate regular subalgebra of the complex Lie algebra \gg^{C} associated to G and ωis a closed 2-form on \gk, such t…
The study classifies Riemannian homogeneous spaces with polar isotropy actions.
problem Characterizing Riemannian homogeneous spaces with polar isotropy actions.
method Analyzing simply connected Riemannian homogeneous spaces of compact semisimple Lie groups and various non-compact spaces.
result Classification and non-polar isotropy actions for specific spaces.
Study limits of adjoint orbits for Lie groups, describing nilpotent orbits.
problem Understanding limits of adjoint orbits for Lie groups.
method Systematic and topological study of limits of continuous families of adjoint orbits for non-compact simple Lie groups.
result Explicit description of nilpotent orbits in terms of Richardson orbits for hyperbolic semisimple elements.
We show the local rigidity of complex hyperbolic lattices in classical Hermitian semisimple Lie groups, SU(np,p),Sp(2n+2,R),SO∗(2n+2),SO(2n,2). This reproves or generalizes some results in \cite{GM, KKP, Klingler-inv, Pozzetti}.
We factorize harmonic maps with values in a semisimple Lie groups in a product of harmonic maps with values in the components of the Iwasawa decomposition. In particular, we use this factorization to study the harmonic maps from Rn into SL(2,R).
Classifies semisimple weakly symmetric pseudo-Riemannian manifolds.
problem Classifying pseudo-Riemannian manifolds with specific properties.
method Developed from compact Lie group cases, analyzed isotropy representation and metric signature.
result Obtained classification of semisimple weakly symmetric manifolds of specific signatures.
Constructs Lie groups with negative Ricci curvature.
problem Finding Lie groups with negative Ricci curvature.
method Constructs Lie groups with specific algebraic structures and representations.
result Proves existence of Lie groups with negative Ricci curvature for various Levi factors.
Explains complex adjoint orbits in Lie theory and geometry.
problem Understanding adjoint orbits in Lie theory and geometry.
method Expository introduction to adjoint orbits of complex semisimple groups.
result Provides insights into properties of semisimple and nilpotent orbits.
The paper classifies orbits of semisimple elements in real semisimple Lie algebras.
problem Classifying orbits of semisimple elements in real semisimple Lie algebras.
method Case by case analysis of complex numbers and Galois cohomology for real numbers.
result Characterization of orbits with real representatives.
Proof of boundedness of quasimorphisms for certain Lie groups.
problem Bounding quasimorphisms on lattices in Lie groups.
method Thermodynamic formalism applied to bounded cohomology.
result Every π-quasimorphism on irreducible uniform lattices is bounded.
The paper classifies manifolds acted upon by a specific Lie group.
problem Characterizing manifolds acted upon by a specific Lie group.
method Analyzing the structure of manifolds under isometric action of a Lie group.
result Characterization of the structure of manifolds under specific Lie group action.
We apply the Guillemin-Lerman-Sternberg theorem to reprove a formula of Heckman for the Duistermaat-Heckman measure associated to the coadjoint action of T, a maximal torus of a compact semisimple Lie group G, on a regular coadjoint G-orbit in the dual space of the Lie algebra of G. This formula is, in an appro…
We complete the quasi-isometric classification of irreducible lattices in semisimple Lie groups over nondiscrete locally compact fields of characteristic zero by showing that any quasi-isometry of a rank one S-arithmetic lattice in a semisimple Lie group over nondiscrete locally compact fields of characteristic zero is…
Extends Anosov subgroup definitions to more general groups.
problem Characterize subgroups of semisimple Lie groups.
method Relativizes characterizations of Anosov subgroups.
result Proves implications and equivalences between relativized characterizations.
We continue the study of the distribution of closed geodesics on nilmanifolds constructed from a simply connected 2-step nilpotent Lie group with a left invariant metric and a lattice. We consider a Lie group with an associated 2-step nilpotent Lie algebra constructed from an irreducible representation of a compact sem…
We prove a generalization of Livsic's Theorem on the vanishing of the cohomology of certain types of dynamical systems. As a consequence, we strengthen a result due to Zimmer concerning algebraic hulls of Anosov actions of semisimple Lie groups. Combining this with Topological Superrigidity, we find a Holder geometric …
Study on almost Kaehler geometry of Lie groups orbits.
problem Understanding the geometry of adjoint orbits of Lie groups.
method Explicit formulas for Chern-Ricci form, scalar curvature, and Nijenhuis tensor derived from root data.
result Explicit formulas and conditions for the Chern-Ricci form and Kaehler type quotients.
New non-solvable Lie groups found with negative Ricci curvature.
problem Finding new Lie groups with negative Ricci curvature.
method Using a general construction from a previous article, the authors produce metric Lie algebras with negative Ricci curvature for compact semisimple Lie algebras.
result The constructed Lie algebras have negative Ricci curvature for all but finitely many finite-dimensional irreducible representations of the Lie algebra.
Prove a global shadow lemma for Patterson-Sullivan measures associated with relatively Morse subgroups in higher-rank semisimple Lie groups.
problem Prove a global shadow lemma for Patterson-Sullivan measures associated with relatively Morse subgroups in higher-rank semisimple Lie groups.
method Prove a global shadow lemma for Patterson-Sullivan measures associated with relatively Morse subgroups in higher-rank semisimple Lie groups.
result Prove a global shadow lemma for Patterson-Sullivan measures associated with relatively Morse subgroups in higher-rank semisimple Lie groups.
Compactifies character varieties for group actions.
problem Compactify character varieties for better topological analysis.
method Real spectrum compactification of character varieties in semisimple Lie groups.
result Provides a compactification with good topological properties.
We study primitive stable representations of free groups into higher rank semisimple Lie groups and their properties. Let Σ be a compact, connected, orientable surface (possibly with boundary) of negative Euler characteristic. We first verify the σmod-regularity for convex projective structures and positive repr…
Explicitly describes pluriclosed metrics on compact Lie groups.
problem Characterizing pluriclosed metrics on compact Lie groups.
method Explicit description using root systems and invariant structures.
result Explicit formulas for pluriclosed metrics in terms of root systems.
Study quasi-isometric embeddings in symmetric spaces and Lie groups.
problem Understanding embeddings between symmetric spaces and Lie groups.
method Decompose embeddings into irreducible components and analyze examples.
result Rigidity results extended to semisimple Lie groups, including counterexamples.
Lower bounds for quaternionic hyperbolic orbifold volumes found.
problem Finding explicit lower bounds for quaternionic hyperbolic orbifold volumes.
method Using H. C. Wang's radius bound for fundamental domains of semisimple Lie groups.
result Explicit lower bound for quaternionic hyperbolic orbifold volumes depending only on dimension.
Workshop notes on positivity in Lie groups and its applications.
problem Understanding total and Θ-positivity in semisimple Lie groups. method Discussion and analysis of existing theories and recent developments.
result Progress in classifying higher Teichmüller spaces through Θ-positivity. Study answers arithmeticity question for normal subgroup of lattices.
problem Arithmeticity of discrete subgroups of semisimple Lie groups with dense commensurators.
method Examined normal subgroups of lattices in semisimple Lie groups.
result Positive answer to Greenberg-Shalom's question for lattices.
The Greenberg-Shalom hypothesis connects subgroup properties to lattice structures in Lie groups.
problem Understanding subgroup properties in Lie groups and their implications.
method Analyzing infinite discrete subgroups of semisimple Lie groups and their commensurators.
result An infinite discrete subgroup of a semisimple Lie group with a dense commensurator is a lattice in a product of some factors.
We formulate and prove that there are "abundant" in nilpotent orbits in real semisimple Lie algebras, in the following sense. If S denotes the collection of hyperbolic elements corresponding the weighted Dynkin diagrams coming from nilpotent orbits, then S span the maximally expected space, namely, the (-1)-eigenspace …
Let G be a connected semisimple Lie group without compact factors whose real rank is at least 2, and let Γ\subset G be an irreducible lattice. We provide a C^\infty classification for volume-preserving Cartan actions of Γand G. Also, if G has real rank at least 3, we provide a C^\infty classification for volume-preserv…
Establishes geometric properties of elements in the positive semigroup of a general real semisimple Lie group.
problem Generalizing Lusztig's total positivity to the setting of general real semisimple Lie groups.
method Classifying Lie groups admitting a positive structure and establishing key properties of unipotent positive semigroups.
result Establishes key geometric properties of elements in the positive semigroup.
Classifies special Lie algebras with semisimple types.
problem Classifying Lie algebras of semisimple type.
method Introduced conformal pseudo-subriemannian fundamental graded Lie algebras and provided their classification.
result Classification of conformal pseudo-subriemannian fundamental graded Lie algebras of semisimple type and their prolongations.
Study of HCF on Lie groups leads to static metrics.
problem Investigating Hermitian curvature flow on Lie groups.
method Ricci-flow type equation and convergence analysis.
result Existence and convergence of solutions to HCF.
Non-invariant complex structures on Lie groups are not biholomorphic to invariant ones.
problem Understanding non-invariant deformations of complex structures on Lie groups.
method Computed cohomologies to show non-biholomorphicity.
result Non-invariant complex structures are not biholomorphic to invariant ones.
We study post-Lie algebra structures on pairs of Lie algebras (g,n), and prove existence results for the case that one of the Lie algebras is semisimple. For semisimple g and solvable n we show that there exist no post-Lie algebra structures on (g,n). For semisimple n and certain solvable g we construct canonical post-…
Classifies semisimple pairs in complex and quaternionic hyperbolic spaces.
problem Classifying semisimple pairs in Lie groups.
method Using configuration spaces and conjugacy classes.
result Local parametrization of representations of semisimple pairs.