Asymptotic growth of saturated powers and epsilon multiplicity

Asymptotic properties of saturated powers of modules over a local domain R are studied. Under mild conditions, it is shown that the limit as k goes to infinity of the quotient of the saturation of the k-th power of a module E by the k-th power of E, when divided by k^{d+e-1}, exists. Here d is the dimension of R and e is the rank of E. We deduce that under these assumptions, the epsilon multiplicity of E, defined by Ulrich and Validashti as a limsup, actually exists as a limit.Comment: 9 pages. In the revised version a typo ("n" changed to "k") is fixed in the statement of Corollary 1.3. A couple of new corollaries are added and some references are added. In the second revision (13 pages) some extensions from domains of depth \ge 2 are given to domains of dimension \ge

Artificial Constraints and Lipschitz Hints for Unconstrained Online Learning

We provide algorithms that guarantee regret $R_T(u)\le \tilde O(G\|u\|^3 + G(\|u\|+1)\sqrt{T})$ or $R_T(u)\le \tilde O(G\|u\|^3T^{1/3} + GT^{1/3}+ G\|u\|\sqrt{T})$ for online convex optimization with $G$-Lipschitz losses for any comparison point $u$ without prior knowledge of either $G$ or $\|u\|$. Previous algorithms dispense with the $O(\|u\|^3)$ term at the expense of knowledge of one or both of these parameters, while a lower bound shows that some additional penalty term over $G\|u\|\sqrt{T}$ is necessary. Previous penalties were exponential while our bounds are polynomial in all quantities. Further, given a known bound $\|u\|\le D$, our same techniques allow us to design algorithms that adapt optimally to the unknown value of $\|u\|$ without requiring knowledge of $G$

Local monomialization of transcendental extensions

Suppose that f is a dominant morphism from a k-variety X to a k-variety Y, where k is a field of characteristic 0 and v is a valuation of the function field k(X). We allow v to be an arbitary valuation, so it may not be discrete. We prove that there exist sequences of blowups of nonsingular subvarieties from X' to X and from Y' to Y such that X', Y' are nonsingular and X' to Y' is locally a monomial mapping near the center of v. This extends an earlier result of ours (in Asterisque 260) which proves the above result with the restriction that f is generically finite.Comment: 50 page

Counterexamples to local monomialization in positive characteristic

In this paper we consider birational properties of ramification in excellent local rings. We give an example showing that local monomialization (and weak local monomialization) can fail for extensions of algebraic local rings in algebraic function fields of dimension greater than or equal to two along a valuation over a field of positive characteristic. It was earlier proven by the author that local monomialization holds within characteristic zero algebraic function fields.Comment: 11 page

Strong Toroidalization of Dominant Morphisms of 3-folds

Suppose that $f:X\to Y$ is a dominant morphism of 3-folds over an algebraically closed field of characteristic zero. We prove that there exist sequences of blow ups of points and nonsingular curves $\Phi:X_1\to X$ and $\Psi:Y_1\to Y$ such that the induced map $f_1:Y_1\to X_1$ is a toroidal morphism. This extends an earlier proof of the author of this theorem with the extra assumption that $f$ is birational.Comment: 121 page

Rectilinearization of sub analytic sets as a consequence of local monomialization

We give a new proof of the rectilinearization theorem of Hironaka. We deduce rectilinearization as a consequence of our theorem on local monomialization for complex and real analytic morphisms.Comment: 13 page

Resolution of Singularities for 3-folds in positive characteristic

In this paper a concise, complete proof of resolution of singularities of 3-folds in positive characteristic (>5) is given. The first proof of this theorem was given by Abhyankar in 1966. The resolution morphism in our proof is an isomorphism over the nonsingular locus.Comment: 55 pages. In this final version, which is to appear in the American Journal of Mathematics, complete details of the proof of embedded resolution of surfaces have been added in. Two sections have been added after the introduction, giving an outline of the proof, and discussing related results and extensions of the material proved in this pape

Asymptotic Multiplicities

We give several new applications of our theorem on the existence of multiplicity of graded families of ideals as a limit, including a very general Minkowski type inequality for graded families of ideals, a very general formula for existence of local volumes as a limit and a very general theorem on the existence of epsilon multiplicities as a limit for modules.Comment: 29 page

Generically Finite Morphisms

We consider the problem of birationally modifying a morphism of complete varieties to make it a morphism from a nonsingular variety to a normal variety. Our main result is to give a counterexample to this problem. This example also is a counterexample to the related conjecture of Abhyankar on ``weak simultaneous global resolution''. We also give some positive results. Forinstance, a positive result of this kind is possible if we remove the separatedness condition

Ramification of valuations and local rings

In this paper we consider birational properties of ramification in excellent local rings. We extend earlier results of the author with Olivier Piltant to show that strong local monomialization is true along a valuation dominating a defectless extension of two dimensional excellent local rings. We also obtain general results on the structure of the extension of associated graded rings along a valuation, and show that the invariants alpha and beta of stable forms of two dimensional extensions in characteristic p of the author and Olivier Piltant are not eventually constant.Comment: 31 pages. Formerly part of arXiv:1404.745