Galois cohomology of reductive algebraic groups over the field of real numbers

We describe functorially the first Galois cohomology set of a connected reductive algebraic group over the field R of real numbers in terms of a certain action of the Weyl group on the real points of order dividing 2 of the maximal torus containing a maximal compact torus. This result was announced with a sketch of proof in the author's 1988 note. Here we give a detailed proof.Comment: 6 page

On representations of integers by indefinite ternary quadratic forms

Let $f$ be an indefinite ternary quadratic form, and let $q$ be an integer such that $-q det(f)$ is not a square. Let $N(T,f,q)$ denote the number of integral solutions of the equation $f(x)=q$ where $x$ lies in the ball of radius $T$ centered at the origin. We are interested in the asymptotic behavior of $N(T,f,q)$ as $T$ tends to infinity. We deduce from the results of our joint paper with Z. Rudnick that $N(T,f,q)$ grows like cE(T,f,q)$as$T$tends to infinity, where$E(T,f,q)$is the Hardy-Littlewood expectation (the product of local densities) and$0 \le c \le 2$. We give examples of$f$and$q$such that$c$ takes the values 0, 1, 2.Comment: AMSTeX, 10 page