5,322 research outputs found
Theoretical prediction and spectroscopic fingerprints of an orbital transition in CeCu2Si2
We show that the heavy-fermion compound CeCu2Si2 undergoes a transition
between two regimes dominated by different crystal-field states. At low
pressure P and low temperature T the Ce 4f electron resides in the atomic
crystal-field ground state, while at high P or T the electron occupancy and
spectral weight is transferred to an excited crystal-field level that
hybridizes more strongly with itinerant states. These findings result from
first-principles dynamical-mean-field-theory calculations. We predict
experimental signatures of this orbital transition in X-ray spectroscopy. The
corresponding fluctuations may be responsible for the second high-pressure
superconducting dome observed in this and similar materials.Comment: 5 pages, 4 figures + 5 supplementary page
Consistent Re-Calibration of the Discrete-Time Multifactor Vasi\v{c}ek Model
The discrete-time multifactor Vasi\v{c}ek model is a tractable Gaussian spot
rate model. Typically, two- or three-factor versions allow one to capture the
dependence structure between yields with different times to maturity in an
appropriate way. In practice, re-calibration of the model to the prevailing
market conditions leads to model parameters that change over time. Therefore,
the model parameters should be understood as being time-dependent or even
stochastic. Following the consistent re-calibration (CRC) approach, we
construct models as concatenations of yield curve increments of Hull-White
extended multifactor Vasi\v{c}ek models with different parameters. The CRC
approach provides attractive tractable models that preserve the no-arbitrage
premise. As a numerical example, we fit Swiss interest rates using CRC
multifactor Vasi\v{c}ek models.Comment: 29 pages, 16 figures, 2 table
Strong interference effects in the resonant Auger decay of atoms induced by intense X-Ray fields
The theory of resonant Auger decay of atoms in a high intensity coherent
X-ray pulse is presented. The theory includes the coupling between the ground
state and the resonance due to an intense X-ray pulse, taking into account the
decay of the resonance and the direct photoionization of the ground state, both
populating the final ionic states coherently. The theory also considers the
impact of the direct photoionization of the resonance state itself which
typically populates highly-excited ionic states. The combined action of the
resonant decay and of the direct ionization of the ground state in the field
induces a non-hermitian time-dependent coupling between the ground and the
'dressed' resonance stats. The impact of these competing processes on the total
electron yield and on the 2s2p3p P spectator and
2s2p S participator Auger decay spectra of the Ne 1s3p
resonance is investigated. The role of the direct photoionization of the ground
state and of the resonance increases dramatically with the field intensity.
This results in strong interference effects with distinct patterns in the
electron spectra, different for the participator and spectator final states.Comment: 31 pages, 6 figure
Feshbach resonances of harmonically trapped atoms
Employing a short-range two-channel description we derive an analytic model
of atoms in isotropic and anisotropic harmonic traps at a Feshbach resonance.
On this basis we obtain a new parameterization of the energy-dependent
scattering length which differs from the one previously employed. We validate
the model by comparison to full numerical calculations for Li-Rb and explain
quantitatively the experimental observation of a resonance shift and
trap-induced molecules in exited bands. Finally, we analyze the bound state
admixture and Landau-Zener transition probabilities.Comment: 4 pages, 2 figures; revised version with extension to anisotropic
traps and new paragraph on trap-induced molecules in excited band
Recurrent bursts via linear processes in turbulent environments
Large-scale instabilities occurring in the presence of small-scale turbulent
fluctuations are frequently observed in geophysical or astrophysical contexts
but are difficult to reproduce in the laboratory. Using extensive numerical
simulations, we report here on intense recurrent bursts of turbulence in plane
Poiseuille flow rotating about a spanwise axis. A simple model based on the
linear instability of the mean flow can predict the structure and time scale of
the nearly-periodic and self-sustained burst cycles. Rotating Poiseuille flow
is suggested as a prototype for future studies of low-dimensional dynamics
embedded in strongly turbulent environments
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