22,539 research outputs found
Splitting Sensitivity of the Ground and 7.6 eV Isomeric States of 229Th
The lowest-known excited state in nuclei is the 7.6 eV isomer of 229Th. This
energy is within the range of laser-based investigations that could allow
accurate measurements of possible temporal variation of this energy splitting.
This in turn could probe temporal variation of the fine-structure constant or
other parameters in the nuclear Hamiltonian. We investigate the sensitivity of
this transition energy to these quantities. We find that the two states are
predicted to have identical deformations and thus the same Coulomb energies
within the accuracy of the model (viz., within roughly 30 keV). We therefore
find no enhanced sensitivity to variation of the fine-structure constant. In
the case of the strong interaction the energy splitting is found to have a
complicated dependence on several parameters of the interaction, which makes an
accurate prediction of sensitivity to temporal changes of fundamental constants
problematical. Neither the strong- nor Coulomb-interaction contributions to the
energy splitting of this doublet can be constrained within an accuracy better
than a few tens of keV, so that only upper limits can be set on the possible
sensitivity to temporal variations of the fundamental constants.Comment: 4 pages, 2 figure
Constraints on the long-period moment-dip tradeoff for the Tohoku earthquake
Since the work of Kanamori and Given (1981), it has been recognized that shallow, pure dip-slip earthquakes excite long-period surface waves such that it is difficult to independently constrain the moment (M_0) and the dip (ÎŽ) of the source mechanism, with only the product M_0 sin(2ÎŽ) being well constrained. Because of this, it is often assumed that the primary discrepancies between the moments of shallow, thrust earthquakes are due to this moment-dip tradeoff. In this work, we quantify how severe this moment-dip tradeoff is depending on the depth of the earthquake, the station distribution, the closeness of the mechanism to pure dip-slip, and the quality of the data. We find that both long-period Rayleigh and Love wave modes have moment-dip resolving power even for shallow events, especially when stations are close to certain azimuths with respect to mechanism strike and when source depth is well determined. We apply these results to USGS W phase inversions of the recent M9.0 Tohoku, Japan earthquake and estimate the likely uncertainties in dip and moment associated with the moment- dip tradeoff. After discussing some of the important sources of moment and dip error, we suggest two methods for potentially improving this uncertainty
Loss-tolerant operations in parity-code linear optics quantum computing
A heavy focus for optical quantum computing is the introduction of
error-correction, and the minimisation of resource requirements. We detail a
complete encoding and manipulation scheme designed for linear optics quantum
computing, incorporating scalable operations and loss-tolerant architecture.Comment: 8 pages, 6 figure
Investigation of fast initialization of spacecraft bubble memory systems
Bubble domain technology offers significant improvement in reliability and functionality for spacecraft onboard memory applications. In considering potential memory systems organizations, minimization of power in high capacity bubble memory systems necessitates the activation of only the desired portions of the memory. In power strobing arbitrary memory segments, a capability of fast turn on is required. Bubble device architectures, which provide redundant loop coding in the bubble devices, limit the initialization speed. Alternate initialization techniques are investigated to overcome this design limitation. An initialization technique using a small amount of external storage is demonstrated
Neutrino-12C scattering in the ab initio shell model with a realistic three-body interaction
We investigate cross sections for neutrino-12C exclusive scattering and for
muon capture on 12C using wave functions obtained in the ab initio no-core
shell model. In our parameter-free calculations with basis spaces up to the 6
hbarOmega we show that realistic nucleon-nucleon interactions, like e.g. the
CD-Bonn, under predict the experimental cross sections by more than a factor of
two. By including a realistic three-body interaction, Tucson-Melbourne TM'(99),
the cross sections are enhanced significantly and a much better agreement with
experiment is achieved. At the same time,the TM'(99) interaction improves the
calculated level ordering in 12C. The comparison between the CD-Bonn and the
three-body calculations provides strong confirmation for the need to include a
realistic three-body interaction to account for the spin-orbit strength in
p-shell nuclei.Comment: 6 pages, 2 figure
Prompt Beta Spectroscopy as a Diagnostic for Mix in Ignited NIF Capsules
The National Ignition Facility (NIF) technology is designed to drive
deuterium-tritium (DT) internal confinement fusion (ICF) targets to ignition
using indirect radiation from laser beam energy captured in a hohlraum.
Hydrodynamical instabilities at interfaces in the ICF capsule leading to mix
between the DT fue l and the ablator shell material are of fundamental physical
interest and can affect the performance characteristics of the capsule. In this
Letter we describe new radiochemical diagnostics for mix processes in ICF
capsules with plastic or Be (0.9%Cu) ablator shells. Reactions of high-energy
tritons with shell material produce high-energy -emitters.
We show that mix between the DT fuel and the shell material enhances
high-energy prompt beta emission from these reactions by more than an order of
magnitude over that expected in the absence of mix
Optimal cooling strategies for magnetically trapped atomic Fermi-Bose mixtures
We discuss cooling efficiency for different-species Fermi-Bose mixtures in
magnetic traps. A better heat capacity matching between the two atomic species
is achieved by a proper choice of the Bose cooler and the magnetically
trappable hyperfine states of the mixture. When a partial spatial overlap
between the two species is also taken into account, the deepest Fermi
degeneracy is obtained for an optimal value of the trapping frequency ratio.
This can be achieved by assisting the magnetic trap with a deconfining light
beam, as shown in the case of fermionic 6Li mixed with 23Na, 87Rb, and 133Cs,
with optimal conditions found for the not yet explored 6Li-87Rb mixture.Comment: 5 pages, 3 figures, to appear in Physical Review
- âŠ