4,932 research outputs found
Optical carrier wave shocking: detection and dispersion
Carrier wave shocking is studied using the Pseudo-Spectral Spatial Domain
(PSSD) technique. We describe the shock detection diagnostics necessary for
this numerical study, and verify them against theoretical shocking predictions
for the dispersionless case. These predictions show Carrier Envelope Phase
(CEP) and pulse bandwidth sensitivity in the single-cycle regime. The flexible
dispersion management offered by PSSD enables us to independently control the
linear and nonlinear dispersion. Customized dispersion profiles allow us to
analyze the development of both carrier self-steepening and shocks. The results
exhibit a marked asymmetry between normal and anomalous dispersion, both in the
limits of the shocking regime and in the (near) shocked pulse waveforms.
Combining these insights, we offer some suggestions on how carrier shocking (or
at least extreme self-steepening) might be realised experimentally.Comment: 9 page
Status of the Fermilab Muon (g-2) Experiment
The New Muon Collaboration at Fermilab has proposed to measure the
anomalous magnetic moment of the muon, , a factor of four better than
was done in E821 at the Brookhaven AGS, which obtained ppm. The last digit of is changed
from the published value owing to a new value of the ratio of the
muon-to-proton magnetic moment that has become available. At present there
appears to be a difference between the Standard-Model value and the measured
value, at the standard deviation level when electron-positron
annihilation data are used to determine the lowest-order hadronic piece of the
Standard Model contribution. The improved experiment, along with further
advances in the determination of the hadronic contribution, should clarify this
difference. Because of its ability to constrain the interpretation of
discoveries made at the LHC, the improved measurement will be of significant
value, whatever discoveries may come from the LHC.Comment: Proceedings of the PhiPsi09, Oct. 13-16, 2009, Beijing, China, 4
pages 2 figures. Version 2 includes Fermilab report number, minor corrections
and one additional referenc
Carrier-wave steepened pulses and gradient-gated high-order harmonic generation using linear ramp waveforms
We show how to optimize the process of high-harmonic generation (HHG) by
gating the interaction using the field gradient of a driving pulse with a
linear ramp waveform. Since maximized field gradients are efficiently generated
by self-steepening processes, we first present a generalized theory of optical
carrier-wave self-steepened (CSS) pulses. This goes beyond existing treatments,
which only consider third-order nonlinearity, and has the advantage of
describing pulses whose wave forms have a range of symmetry properties.
Although a fertile field for theoretical work, CSS pulses are difficult to
realize experimentally because of the deleterious effect of dispersion. We
therefore consider synthesizing CSS-like profiles using a suitably phased
sub-set of the harmonics present in a true CSS wave form. Using standard
theoretical models of HHG, we show that the presence of gradient-maximized
regions on the wave forms can raise the spectral cut-off and so yield shorter
attosecond pulses. We study how the quality of the attosecond bursts created by
spectral filtering depends on the number of harmonics included in the driving
pulse.Comment: 8 pages, 10 figures; with appendix not present in published versio
Computational Relativistic Astrophysics With Adaptive Mesh Refinement: Testbeds
We have carried out numerical simulations of strongly gravitating systems
based on the Einstein equations coupled to the relativistic hydrodynamic
equations using adaptive mesh refinement (AMR) techniques. We show AMR
simulations of NS binary inspiral and coalescence carried out on a workstation
having an accuracy equivalent to that of a regular unigrid simulation,
which is, to the best of our knowledge, larger than all previous simulations of
similar NS systems on supercomputers. We believe the capability opens new
possibilities in general relativistic simulations.Comment: 7 pages, 16 figure
Eigenvector Expansion and Petermann Factor for Ohmically Damped Oscillators
Correlation functions in ohmically damped
systems such as coupled harmonic oscillators or optical resonators can be
expressed as a single sum over modes (which are not power-orthogonal), with
each term multiplied by the Petermann factor (PF) , leading to "excess
noise" when . It is shown that is common rather than
exceptional, that can be large even for weak damping, and that the PF
appears in other processes as well: for example, a time-independent
perturbation \sim\ep leads to a frequency shift \sim \ep C_j. The
coalescence of () eigenvectors gives rise to a critical point, which
exhibits "giant excess noise" (). At critical points, the
divergent parts of contributions to cancel, while time-independent
perturbations lead to non-analytic shifts \sim \ep^{1/J}.Comment: REVTeX4, 14 pages, 4 figures. v2: final, 20 single-col. pages, 2
figures. Streamlined with emphasis on physics over formalism; rewrote Section
V E so that it refers to time-dependent (instead of non-equilibrium) effect
Three-dimensional adaptive evolution of gravitational waves in numerical relativity
Adaptive techniques are crucial for successful numerical modeling of
gravitational waves from astrophysical sources such as coalescing compact
binaries, since the radiation typically has wavelengths much larger than the
scale of the sources. We have carried out an important step toward this goal,
the evolution of weak gravitational waves using adaptive mesh refinement in the
Einstein equations. The 2-level adaptive simulation is compared with unigrid
runs at coarse and fine resolution, and is shown to track closely the features
of the fine grid run.Comment: REVTeX, 7 pages, including three figures; submitted to Physical
Review
- …