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On the Noether exponent

Anna Stasica (2003)

Annales Polonici Mathematici

We obtain, in a simple way, an estimate for the Noether exponent of an ideal I without embedded components (i.e. we estimate the smallest number μ such that ( r a d I ) μ I ).

On the nontrivial solvability of systems of homogeneous linear equations over in ZFC

Jan Šaroch (2020)

Commentationes Mathematicae Universitatis Carolinae

Motivated by the paper by H. Herrlich, E. Tachtsis (2017) we investigate in ZFC the following compactness question: for which uncountable cardinals κ , an arbitrary nonempty system S of homogeneous -linear equations is nontrivially solvable in provided that each of its subsystems of cardinality less than κ is nontrivially solvable in ?

On the number of compatibly Frobenius split subvarieties, prime F -ideals, and log canonical centers

Karl Schwede, Kevin Tucker (2010)

Annales de l’institut Fourier

Let X be a projective Frobenius split variety with a fixed Frobenius splitting θ . In this paper we give a sharp uniform bound on the number of subvarieties of X which are compatibly Frobenius split with θ . Similarly, we give a bound on the number of prime F -ideals of an F -finite F -pure local ring. Finally, we also give a bound on the number of log canonical centers of a log canonical pair. This final variant extends a special case of a result of Helmke.

On the Pierce-Birkhoff Conjecture for Smooth Affine Surfaces over Real Closed Fields

Sven Wagner (2010)

Annales de la faculté des sciences de Toulouse Mathématiques

We will prove that the Pierce-Birkhoff Conjecture holds for non-singular two-dimensional affine real algebraic varieties over real closed fields, i.e., if W is such a variety, then every piecewise polynomial function on W can be written as suprema of infima of polynomial functions on W . More precisely, we will give a proof of the so-called Connectedness Conjecture for the coordinate rings of such varieties, which implies the Pierce-Birkhoff Conjecture.

On the polynomial-like behaviour of certain algebraic functions

Charles Feffermann, Raghavan Narasimhan (1994)

Annales de l'institut Fourier

Given integers D > 0 , n > 1 , 0 < r < n and a constant C > 0 , consider the space of r -tuples P = ( P 1 ... P r ) of real polynomials in n variables of degree D , whose coefficients are C in absolute value, and satisfying det P i x i ( 0 ) 1 i , j r = 1 . We study the family { f | V } of algebraic functions, where f is a polynomial, and V = { | x | δ , P ( x ) = 0 } , δ > 0 being a constant depending only on n , D , C . The main result is a quantitative extension theorem for these functions which is uniform in P . This is used to prove Bernstein-type inequalities which are again uniform with respect to P .The proof is based on...

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