76,864 research outputs found
Editorial: The pre-history of Chaos—An Interdisciplinary Journal of Nonlinear Science
Published versio
Spin-Peierls transition in the Heisenberg chain with finite-frequency phonons
We study the spin-Peierls transition in a Heisenberg spin chain coupled to optical bond phonons. Quantum Monte Carlo results for systems with up to N=256 spins show unambiguously that the transition occurs only when the spin-phonon coupling α exceeds a critical value α_c. Using sum rules, we show that the phonon spectral function has divergent (for N→∞) weight extending to zero frequency for α<α_c. The phonon correlations decay with distance r as 1/r. This behavior is characteristic for all 0<α<α_c and the q=π phonon does not soften (to zero frequency) at α=α_c.First author draf
Behavior and Breakdown of Higher-Order Fermi-Pasta-Ulam-Tsingou Recurrences
We investigate numerically the existence and stability of higher-order
recurrences (HoRs), including super-recurrences, super-super-recurrences, etc.,
in the alpha and beta Fermi-Pasta-Ulam-Tsingou (FPUT) lattices for initial
conditions in the fundamental normal mode. Our results represent a considerable
extension of the pioneering work of Tuck and Menzel on super-recurrences. For
fixed lattice sizes, we observe and study apparent singularities in the periods
of these HoRs, speculated to be caused by nonlinear resonances. Interestingly,
these singularities depend very sensitively on the initial energy and the
respective nonlinear parameters. Furthermore, we compare the mechanisms by
which the super-recurrences in the two model's breakdown as the initial energy
and respective nonlinear parameters are increased. The breakdown of
super-recurrences in the beta-FPUT lattice is associated with the destruction
of the so-called metastable state and hence is associated with relaxation
towards equilibrium. For the alpha-FPUT lattice, we find this is not the case
and show that the super-recurrences break down while the lattice is still
metastable. We close with comments on the generality of our results for
different lattice sizes
Method and system for respiration analysis Patent
Respiration analyzing method and apparatus for determining subjects oxygen consumption in aerospace environment
Chaos at Fifty
In 1963 Edward Lorenz revealed deterministic predictability to be an illusion
and gave birth to a field that still thrives. This Feature Article discusses
Lorenz's discovery and developments that followed from it.Comment: For an animated visualization of the Lorenz attractor, click here
http://www.youtube.com/watch?v=iu4RdmBVdp
MCFM for the Tevatron and the LHC
A summary is given of the current status of the next-to-leading order (NLO)
parton-level integrator MCFM. Some details are given about the Higgs + 2-jet
process and the production and decay of , both of which have
recently been added to the code. Using MCFM, comparisons between the Tevatron
running at ~TeV and the LHC running at ~TeV are made
for standard model process including the production of Higgs bosons. The case
for running the Tevatron until 16fb are accumulated by both detectors is
sketched.Comment: Talk presented by R.K Ellis at Loops and Legs in Quantum Field Theory
2010, Woerlitz, Germany, April 25-30, 2010, (6 pages and 4 figures
- …