scholarly journals Maintaining Constant Pulse-Duration in Highly Dispersive Media Using Nonlinear Potentials

Photonics ◽  
2021 ◽  
Vol 8 (12) ◽  
pp. 570
Author(s):  
Haider Zia
Keyword(s):  
Strong Field ◽  
Propagation Distance ◽  
Weak Field ◽  
Dispersive Media ◽  
Signal Pulse ◽  
Nonlinear Phenomenon ◽  
Numerical Example ◽  
Ultrafast Optical ◽  
Nonlinear Potentials ◽  
Temporal Broadening

A method is shown for preventing temporal broadening of ultrafast optical pulses in highly dispersive and fluctuating media for arbitrary signal-pulse profiles. Pulse pairs, consisting of a strong-field control-pulse and a weak-field signal-pulse, co-propagate, whereby the specific profile of the strong-field pulse precisely compensates for the dispersive phase in the weak pulse. A numerical example is presented in an optical system consisting of both resonant and gain dispersive effects. Here, we show signal-pulses that do not temporally broaden across a vast propagation distance, even in the presence of dispersion that fluctuates several orders of magnitude and in sign (for example, within a material resonance) across the pulse’s bandwidth. Another numerical example is presented in normal dispersion telecom fiber, where the length at which an ultrafast pulse does not have significant temporal broadening is extended by at least a factor of 10. Our approach can be used in the design of dispersion-less fiber links and navigating pulses in turbulent dispersive media. Furthermore, we illustrate the potential of using cross-phase modulation to compensate for dispersive effects on a signal-pulse and fill the gap in the current understanding of this nonlinear phenomenon.

scholarly journals The confrontation between general relativity and experiment

2009 ◽  
Vol 5 (S261) ◽  
pp. 198-199
Author(s):  
Clifford M. Will
Keyword(s):  
General Relativity ◽  
Gravitational Wave ◽  
Equivalence Principle ◽  
Gamma Ray ◽  
Strong Field ◽  
Weak Field ◽  
X Ray ◽  
Spacetime Geometry ◽  
Tests Of General Relativity ◽  
Laser Interferometric

AbstractWe review the experimental evidence for Einstein's general relativity. A variety of high precision null experiments confirm the Einstein Equivalence Principle, which underlies the concept that gravitation is synonymous with spacetime geometry, and must be described by a metric theory. Solar system experiments that test the weak-field, post-Newtonian limit of metric theories strongly favor general relativity. Binary pulsars test gravitational-wave damping and aspects of strong-field general relativity. During the coming decades, tests of general relativity in new regimes may be possible. Laser interferometric gravitational-wave observatories on Earth and in space may provide new tests via precise measurements of the properties of gravitational waves. Future efforts using X-ray, infrared, gamma-ray and gravitational-wave astronomy may one day test general relativity in the strong-field regime near black holes and neutron stars.

scholarly journals Iron Complexes of a Proton-Responsive SCS Pincer Ligand with Sensitive Electronic Structure

2021 ◽  
Author(s):  
Kazimer Skubi ◽  
Reagan Hooper ◽  
Brandon Mercado ◽  
Melissa Bollmeyer ◽  
Samantha MacMillan ◽  
...  
Keyword(s):  
Strong Field ◽  
Alkali Metal Cation ◽  
Weak Field ◽  
Pincer Ligands ◽  
Zero Field ◽  
Zero Field Splitting ◽  
Pincer Ligand ◽  
Intermediate Spin ◽  
X Ray Absorption ◽  
Phosphine Complex

SCS pincer ligands have an interesting combination of strong-field and weak-field donors that is also present in the nitrogenase active site. Here, we explore the electronic structures of iron(II) and iron(III) complexes with such a pincer ligand, bearing a monodentate phosphine, thiolate S donor, amide N donor, ammonia, or CO. The ligand scaffold features a protonresponsive thioamide site, and the protonation state of the ligand greatly influences the reduction potential of iron in the phosphine complex. The N–H bond dissociation free energy can be quantitated as 56 ± 2 kcal/mol. EPR spectroscopy and SQUID magnetometry measurements show that the iron(III) complexes with S and N as the fourth donors have an intermediate spin (S = 3/2) ground state with large zero field splitting, and X-ray absorption spectra show high Fe–S covalency. The Mössbauer spectrum changes drastically with the position of a nearby alkali metal cation in the iron(III) amido complex, and DFT calculations explain this phenomenon through a change between having the doubly-occupied orbital as dz2 or dyz, as the former is more influenced by the nearby positive charge.

Binary pulsars as probes of relativistic gravity

1992 ◽  
Vol 341 (1660) ◽  
pp. 135-149 ◽  
Keyword(s):  
Binary Systems ◽  
Strong Field ◽  
Field Tests ◽  
Weak Field ◽  
Multidimensional Space ◽  
Alternative Theory ◽  
Theory Approach ◽  
Binary Pulsars ◽  
Weak Field Limit ◽  
Self Gravity

Until now, most experiments have succeeded in testing relativistic gravity only in its extreme weak-field limit. Because of the strong self-gravity of neutron stars, observations of pulsars in binary systems provide a unique opportunity for probing the strong-field régime of relativistic gravity. The two basic approaches to using binary pulsar measurements as probes of relativistic gravity are reviewed: the phenomenological (‘parametrized post-keplerian’ formalism) and the alternative-theory approach (multidimensional space of possible theories). The experimental constraints recently derived from the actual timing observations of three binary pulsars are summarized. General relativity passes these new, strong-field tests with complete success.

scholarly journals Lightwave-controlled electron dynamics in graphene

2019 ◽  
Vol 205 ◽  
pp. 05002
Author(s):  
Christian Heide ◽  
Takuya Higuchi ◽  
Konrad Ullmann ◽  
Heiko B. Weber ◽  
Peter Hommelhoff
Keyword(s):  
Strong Field ◽  
Polarized Light ◽  
Laser Pulses ◽  
Weak Field ◽  
Ultrashort Laser Pulses ◽  
Electron Dynamics ◽  
Matter Interaction ◽  
Linearly Polarized ◽  
Light Matter Interaction ◽  
Optical Cycle

We demonstrate that currents induced in graphene by ultrashort laser pulses are sensitive to the exact shape of the electric-field waveform. By increasing the field strength, we found a transition of the light–matter interaction from the weak-field to the strong-field regime at around 2 V/nm, where intraband dynamics influence interband transitions. In this strong-field regime, the light-matter interaction can be described by the wavenumber trajectories of electrons in the reciprocal space. For linearly polarized light the electron dynamics are governed by repeated sub-optical-cycle Landau-Zener transitions between the valence- and conduction band, resulting in Landau-Zener-Stuckelberg interference, whereas for circular polarized light this interference is supressed.

scholarly journals Force balance in convectively driven dynamos with no inertia

2019 ◽  
Vol 879 ◽  
pp. 793-807
Author(s):  
David W. Hughes ◽  
Fausto Cattaneo
Keyword(s):  
Strong Field ◽  
Plane Layer ◽  
Weak Field ◽  
Momentum Equation ◽  
Force Balance ◽  
Dominant Contribution ◽  
Dynamo Action ◽  
Thermal Equation ◽  
Magnetic Part ◽  
Viscous Forces

We study dynamo action in rotating, plane layer Boussinesq convection in the absence of inertia. This allows a decomposition of the velocity into a thermal part driven by buoyancy, and a magnetic part driven by the Lorentz force. We have identified three families of solutions, defined in terms of what is the dominant contribution to the velocity. In weak field dynamos the dominant contribution is the thermal component, in super strong field dynamos the dominant contribution is magnetic and in strong field dynamos the two components are comparable. For each of these solutions we investigate the force balance in the momentum equation to determine the relative importance of the viscous, buoyancy, Coriolis and magnetic forces. We do this by extracting the solenoidal part of the individual terms in the momentum equation, thereby removing their pressure contributions. This is numerically preferable to the more common practice of taking the curl of the momentum equation, which introduces an extra derivative. We find that, irrespective of the type of dynamo solution, the dynamics is controlled by the horizontal forces (in projection). Furthermore, in the progression from weak to strong to super strong dynamos, we find that the viscous forces in the thermal equation become negligible, thereby leading to a balance between buoyancy and Coriolis forces. On the other hand, no corresponding trend is observed in the magnetic part of the momentum equation: the viscous stresses always remain significant. This can be attributed to the different degrees of smoothness of the Coriolis and Lorentz forces, the latter having contributions from strong, filamentary structures. We discuss how our findings relate to dynamo solutions in which viscosity plays no role whatsoever – so-called Taylor states.

scholarly journals Gravitational time delay of signals in the Kerr metric

1986 ◽  
Vol 114 ◽  
pp. 411-416
Author(s):  
I. G. Dymnikova
Keyword(s):  
Time Delay ◽  
Strong Field ◽  
Rotation Axis ◽  
Wave Length ◽  
Field Approximation ◽  
Weak Field ◽  
Gravitational Lens ◽  
Mutual Orientation ◽  
Kerr Metric ◽  
Photon Propagation

The gravitational time delay of signals in a gravitational field of a rotating massive body is considered both in a weak field approximation and in a strong field caused by a rotating black hole. The expressions describing the time of propagation of signals are obtained by integrating the light geodesics of the Kerr metric in a frame reference of a distant observer using the Boyer-Lindquist coordinates and assuming that the wave length of radiation is much less than the characteristic scale of the field. The existence of the asymmetry in the time delay is shown depending on the mutual orientation of a photon propagation direction and of the rotation axis. As a result of this asymmetry, the effects of relative time delay are predicted and calculated for the signals focused by a rotating gravitational lens.

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