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Local Fourier transform and epsilon factors  [PDF]
Ahmed Abbes,Takeshi Saito
Mathematics , 2008, DOI: 10.1112/S0010437X09004631
Abstract: Laumon introduced the local Fourier transform for $\ell$-adic Galois representations of local fields, of equal characteristic $p$ different from $\ell$, as a powerful tool to study the Fourier-Deligne transform of $\ell$-adic sheaves over the affine line. In this article, we compute explicitly the local Fourier transform of monomial representations satisfying a certain ramification condition, and deduce Laumon's formula relating the epsilon factor to the determinant of the local Fourier transform under the same condition.
Adaptive Local Polynomial Fourier Transform in ISAR  [cached]
Djurovi? Igor,Thayaparan Thayananthan,Stankovi? Ljubi?a
EURASIP Journal on Advances in Signal Processing , 2006,
Abstract: The adaptive local polynomial Fourier transform is employed for improvement of the ISAR images in complex reflector geometry cases, as well as in cases of fast maneuvering targets. It has been shown that this simple technique can produce significantly improved results with a relatively modest calculation burden. Two forms of the adaptive LPFT are proposed. Adaptive parameter in the first form is calculated for each radar chirp. Additional refinement is performed by using information from the adjacent chirps. The second technique is based on determination of the adaptive parameter for different parts of the radar image. Numerical analysis demonstrates accuracy of the proposed techniques.
An explicit stationary phase formula for the local formal Fourier-Laplace transform  [PDF]
Claude Sabbah
Mathematics , 2007,
Abstract: We give an explicit formula (i.e., a formal stationary phase formula) for the local Fourier-Laplace transform of a formal germ of meromorphic connection of one complex variable with a possibly irregular singularity. This is a complex analogue of the formulas in the preprint math/0702436v1.
Canonical desingularization in characteristic zero by blowing up the maximum strata of a local invariant  [PDF]
Edward Bierstone,Pierre Milman
Mathematics , 1995,
Abstract: This article contains an elementary constructive proof of resolution of singularities in characteristic zero. Our proof applies in particular to schemes of finite type and to analytic spaces (so we recover the great theorems of Hironaka). We introduce a discrete local invariant $\inv_X (a)$ whose maximum locus determines a smooth centre of blowing up, leading to desingularization. To define $\inv_X$, we need only to work with a category of local-ringed spaces $X=(|X|,{\cal O}_X)$ satisfying certain natural conditions. If $a\in |X|$, then $\inv_X(a)$ depends only on $\widehat{\cal O}_{X,a}$. More generally, $\inv_X(a)$ is defined inductively after any sequence of blowings-up whose centres have only normal crossings with respect to the exceptional divisors and lie in the constant loci of $\inv_X(\cdot)$. The paper is self-contained and includes detailed examples. One of our goals is that the reader understand the desingularization theorem, rather than simply ``know'' it is true.
Blowing-up of locally monomially foliated space  [PDF]
Aymen Braghtha
Mathematics , 2015,
Abstract: In this paper, we prove that the blowing-up preserve the local monomiality of foliated space.
The Amplified Quantum Fourier Transform: solving the local period problem  [PDF]
David J. Cornwell
Physics , 2010,
Abstract: This paper creates and analyses a new quantum algorithm called the Amplified Quantum Fourier Transform (Amplified-QFT) for solving the following problem: The Local Period Problem: Let L = {0,1...N-1} be a set of N labels and let A be a subset of M labels of period P, i.e. a subset of the form A = {j : j = s + rP; r = 0,1...M-1} where P < sqrt(N) and M << N, and where M is assumed known. Given an oracle f : L->{0,1} which is 1 on A and 0 elsewhere, find the local period P. A separate algorithm finds the offset s. The first part of the paper defines the Amplified-QFT algorithm. The second part of the paper summarizes the main results and compares the Amplified-QFT algorithm against the Quantum Fourier Transform (QFT) and Quantum Hidden Subgroup (QHS) algorithms when solving the local period problem. It is shown that the Amplified-QFT is, on average, quadratically faster than both the QFT and QHS algorithms. The third part of the paper provides the detailed proofs of the main results, describes the method of recovering P from an observation y and describes the method for recovering the offset s.
On regularization of formal Fourier--Wiener transform of the self-intersection local time of planar Gaussian process  [PDF]
Andrey A. Dorogovtsev,Olga L. Izumtseva
Mathematics , 2011,
Abstract: Fourier-Wiener transform of the formal expression for multiple self-intersection local time is described in terms of the integral, which is divergent on the diagonals. The method of regularization we use in this work related to regularization of functions with non-integrable singularities. The strong local nondeterminism property, which is more restrictive than the property of local nondeterminism introduced by S.Berman is considered. Its geometrical meaning in the construction of the regularization is investigated. As the example the problem of regularization is solved for the compact perturbation of the planar Wiener process.
Classification of weighted graphs up to blowing-up and blowing-down  [PDF]
Daniel Daigle
Mathematics , 2003,
Abstract: We classify weighted forests up to the blowing-up and blowing-down operations which are relevant for the study of algebraic surfaces.
An application of type sequences to the blowing-up  [PDF]
Anna Oneto,Elsa Zatini
Mathematics , 2006,
Abstract: Let I be an m-primary ideal of a one-dimensional, analytically irreducible and residually rational local Noetherian domain R. Given the blowing-up of R along I we establish connections between the type-sequence of R and classical invariants like multiplicity, genus and reduction exponent of I.
Fourier Transform Scanning Tunneling Spectroscopy: the possibility to obtain constant energy maps and the band dispersion using a local measurement  [PDF]
L. Simon,C. Bena,F. Vonau,M. Cranney,D. Aubel
Physics , 2011, DOI: 10.1088/0022-3727/44/46/464010
Abstract: We present here an overview of the Fourier Transform Scanning Tunneling spectroscopy technique (FT-STS). This technique allows one to probe the electronic properties of a two-dimensional system by analyzing the standing waves formed in the vicinity of defects. We review both the experimental and theoretical aspects of this approach, basing our analysis on some of our previous results, as well as on other results described in the literature. We explain how the topology of the constant energy maps can be deduced from the FT of dI/dV map images which exhibit standing waves patterns. We show that not only the position of the features observed in the FT maps, but also their shape can be explained using different theoretical models of different levels of approximation. Thus, starting with the classical and well known expression of the Lindhard susceptibility which describes the screening of electron in a free electron gas, we show that from the momentum dependence of the susceptibility we can deduce the topology of the constant energy maps in a joint density of states approximation (JDOS). We describe how some of the specific features predicted by the JDOS are (or are not) observed experimentally in the FT maps. The role of the phase factors which are neglected in the rough JDOS approximation is described using the stationary phase conditions. We present also the technique of the T-matrix approximation, which takes into account accurately these phase factors. This technique has been successfully applied to normal metals, as well as to systems with more complicated constant energy contours. We present results recently obtained on graphene systems which demonstrate the power of this technique, and the usefulness of local measurements for determining the band structure, the map of the Fermi energy and the constant-energy maps.
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