These notes are an introduction to Lie algebras, algebraic groups, and Lie groups in characteristic zero, emphasizing the relationships between these objects visible in their categories of representations. Eventually these notes will consist of three chapters, each about 100 pages long, and a short appendix. Single paper copies for noncommercial personal use may be made without explicit permiss...

This article is an exposition of the 1967 paper by Parthasarathy, Ranga Rao, and Varadarajan, on irreducible admissible Harish-Chandra modules over complex semisimple Lie groups and Lie algebras. It was written in Winter 2012 to be part of a special collection organized to mark 10 years and 25 volumes of the series Texts and Readings in Mathematics (TRIM). Each article in this collection is int...

States of unital Abelian lattice-groups (normalised positive group homomorphisms to R) provide an abstraction expected-value operators. A well-known theorem due Mundici asserts that the category (with unit-preserving lattice-group as morphisms) is equivalent algebraic MV-algebras, and their homomorphisms. Through this equivalence, states correspond certain [0,1]-valued functionals on which are ...

We establish results about the second cohomology with coefficients in trivial module, symmetric invariant bilinear forms and derivations of a Lie algebra extended over commutative associative without unit. These provide simple unified approach to number questions treated earlier completely separated ways: periodization semisimple algebras (Anna Larsson), derivation algebras, prescribed part, ni...

We show that finite-dimensional Lie algebras over a field of characteristic zero such that the second cohomology group in every finite-dimensional module vanishes, are, essentially, semisimple.

A condition on an affine central subalgebra Z of a noetherian algebra A of finite GelfandKirillov dimension, which we call here unruffledness, is shown to be equivalent in some circumstances to the flatness of A as a Z-module. Unruffledness was studied by Borho and Joseph in work on enveloping algebras of complex semisimple Lie algebras, and we discuss applications of our result to enveloping a...

Furthermore h was diagonalisable in every irreducible representation and H := Span(h) is obviously an abelian subalgebra. Note that h = h + 0 is the abstract Jordan decomposition of h, that H = CL(H) is the weight space of H , acting on L with the adjoint action, corresponding to the weight 0 ∈ H . Likewise, Span(e) is the weight space for the weight c · h 7→ −2c for c ∈ C, and Span( f ) is the...

We investigate Atiyah algebroids, i.e. the infinitesimal objects of principal bundles, from the viewpoint of Lie algebraic approach to space. First we show that if the Lie algebras of smooth sections of two Atiyah algebroids are isomorphic, then the corresponding base manifolds are necessarily diffeomorphic. Further, we give two characterizations of the isomorphisms of the Lie algebras of secti...

The prime spectra of two families of algebras, Sw and Šw, w ∈ W, indexed by the Weyl group W of a semisimple finitely dimensional Lie algebra g, are studied in the spirit of [J3]. The algebras Sw have been introduced by A. Joseph (see [J4], Sect. 3). They are q-analogues of the algebras of regular functions on w-translates of the open Bruhat cell of a semisimple Lie group G corresponding to the...

A new class of locally unital and finite dimensional algebras over an arbitrary algebraically closed field is discovered. Each them admits upper weakly triangular decomposition, a generalization split decomposition. It established that the category -lfdmod left -modules fully stratified in sense Brundan-Stroppel. Moreover, semisimple if only its centralizer subalgebras associated to certain ide...