18,423 research outputs found
Optimized Neural Networks to Search for Higgs Boson Production at the Tevatron
An optimal choice of proper kinematical variables is one of the main steps in
using neural networks (NN) in high energy physics. Our method of the variable
selection is based on the analysis of a structure of Feynman diagrams
(singularities and spin correlations) contributing to the signal and background
processes. An application of this method to the Higgs boson search at the
Tevatron leads to an improvement in the NN efficiency by a factor of 1.5-2 in
comparison to previous NN studies.Comment: 4 pages, 4 figures, partially presented in proceedings of ACAT'02
conferenc
The n-body problem in General Relativity up to the second post-Newtonian order from perturbative field theory
Motivated by experimental probes of general relativity, we adopt methods from
perturbative (quantum) field theory to compute, up to certain integrals, the
effective lagrangian for its n-body problem. Perturbation theory is performed
about a background Minkowski spacetime to O[(v/c)^4] beyond Newtonian gravity,
where v is the typical speed of these n particles in their center of energy
frame. For the specific case of the 2 body problem, the major efforts underway
to measure gravitational waves produced by in-spiraling compact astrophysical
binaries require their gravitational interactions to be computed beyond the
currently known O[(v/c)^7]. We argue that such higher order post-Newtonian
calculations must be automated for these field theoretic methods to be applied
successfully to achieve this goal. In view of this, we outline an algorithm
that would in principle generate the relevant Feynman diagrams to an arbitrary
order in v/c and take steps to develop the necessary software. The Feynman
diagrams contributing to the n-body effective action at O[(v/c)^6] beyond
Newton are derived.Comment: 39 pages. The Mathematica code used in this paper can be found at
http://www.stargazing.net/yizen/PN.html Version 2: Slight re-wording of
section on removal of accelerations in 2 PN lagrangian; comments added in
conclusion; and typographical errors fixed. Article is similar to that
published in PR
Four-dimensional integration by parts with differential renormalization as a method of evaluation of Feynman diagrams
It is shown how strictly four-dimensional integration by parts combined with
differential renormalization and its infrared analogue can be applied for
calculation of Feynman diagrams.Comment: 6 pages, late
Separable Structure of Many-Body Ground-State Wave Function
We have investigated a general structure of the ground-state wave function
for the Schr\"odinger equation for identical interacting particles (bosons
or fermions) confined in a harmonic anisotropic trap in the limit of large .
It is shown that the ground-state wave function can be written in a separable
form. As an example of its applications, this form is used to obtain the
ground-state wave function describing collective dynamics for trapped
bosons interacting via contact forces.Comment: J. Phys. B: At. Mol. Opt. Phys. 33 (2000) (accepted for publication
Supersymmetric pairing of kinks for polynomial nonlinearities
We show how one can obtain kink solutions of ordinary differential equations
with polynomial nonlinearities by an efficient factorization procedure directly
related to the factorization of their nonlinear polynomial part. We focus on
reaction-diffusion equations in the travelling frame and
damped-anharmonic-oscillator equations. We also report an interesting pairing
of the kink solutions, a result obtained by reversing the factorization
brackets in the supersymmetric quantum mechanical style. In this way, one gets
ordinary differential equations with a different polynomial nonlinearity
possessing kink solutions of different width but propagating at the same
velocity as the kinks of the original equation. This pairing of kinks could
have many applications. We illustrate the mathematical procedure with several
important cases, among which the generalized Fisher equation, the
FitzHugh-Nagumo equation, and the polymerization fronts of microtubulesComment: 13 pages, 2 figures, revised during the 2nd week of Dec. 200
Magnetofossil Spike During the Paleocene-Eocene Thermal Maximum: Ferromagnetic Resonance, Rock Magnetic, and Electron Microscopy Evidence from Ancora, New Jersey, USA
Previous workers identified a magnetically anomalous clay layer deposited on the northern United States Atlantic Coastal Plain during the Paleocene-Eocene Thermal
Maximum (PETM). The finding inspired the highly controversial hypothesis that a cometary impact triggered the PETM. Here we present ferromagnetic resonance (FMR), isothermal and anhysteretic remanent magnetization, first order reversal curve, and transmission electron microscopy analyses of late Paleocene and early Eocene sediments in drillcore from Ancora, New Jersey. A novel paleogeographic analysis applying a recent paleomagnetic pole from the
Faeroe Islands indicates that New Jersey during the initial Eocene had a ~6-9 degrees lower paleolatitude (~27.3 degrees for Ancora) and a more zonal shoreline trace than in conventional reconstructions. Our investigations of the PETM clay from Ancora reveal abundant magnetite nanoparticles bearing signature traits of crystals produced by magnetotactic bacteria. This result, the first identification of ancient biogenic magnetite using FMR, argues that the anomalous magnetic properties of the PETM sediments are not produced by an impact. They instead reflect environmental changes along the eastern margin of North America during the PETM that led to enhanced production and/or preservation of magnetofossils
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