5,181 research outputs found
Few photon transport in a waveguide coupled to a pair of collocated two-level atoms
We calculate the one- and two-photon scattering matrices of a pair of
collocated non-identical two-level atoms coupled to a waveguide. We show that
by proper choice of a two-photon input, the background fluorescence by the
atoms may be completely quenched, as a result of quantum interference, and that
when the atoms' detuning is smaller than their linewidths, extremely narrow
fluorescence features emerge. Furthermore, the system emits a two-photon bound
state which can display spatial oscillations/quantum beats, and can be tuned
from bunched to anti-bunched statistics as the total photon energy is varied
Life History Characteristics Of Daphnia Lumholtzi And Its Susceptibility To An Invertebrate Predator
Microscopic model of diffusion limited aggregation and electrodeposition in the presence of levelling molecules
A microscopic model of the effect of unbinding in diffusion limited
aggregation based on a cellular automata approach is presented. The geometry
resembles electrochemical deposition - ``ions'' diffuse at random from the top
of a container until encountering a cluster in contact with the bottom, to
which they stick. The model exhibits dendritic (fractal) growth in the
diffusion limited case. The addition of a field eliminates the fractal nature
but the density remains low. The addition of molecules which unbind atoms from
the aggregate transforms the deposit to a 100% dense one (in 3D). The molecules
are remarkably adept at avoiding being trapped. This mimics the effect of
so-called ``leveller'' molecules which are used in electrochemical deposition
Trident pair production in strong laser pulses
We calculate the trident pair production amplitude in a strong laser
background. We allow for finite pulse duration, while still treating the laser
fields nonperturbatively in strong-field QED. Our approach reveals explicitly
the individual contributions of the one-step and two-step processes. We also
expose the role gauge invariance plays in the amplitudes and discuss the
relation between our results and the optical theorem.Comment: 4 pages, 1 .eps figure. Version 2: reference added, published versio
The box diagram in Yukawa theory
We present a light-front calculation of the box diagram in Yukawa theory. The
covariant box diagram is finite for the case of spin-1/2 constituents
exchanging spin-0 particles. In light-front dynamics, however, individual
time-ordered diagrams are divergent. We analyze the corresponding light-front
singularities and show the equivalence between the light-front and covariant
results by taming the singularities.Comment: 21 pages, 17 figures. submittes to Phys. Rev.
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