13,427 research outputs found
Highly charged ions with E1, M1, and E2 transitions within laser range
Level crossings in the ground state of ions occur when the nuclear charge Z
and ion charge Z_ion are varied along an isoelectronic sequence until the two
outermost shells are nearly degenerate. We examine all available level
crossings in the periodic table for both near neutral ions and highly charged
ions (HCIs). Normal E1 transitions in HCIs are in X-ray range, however level
crossings allow for optical electromagnetic transitions that could form the
reference transition for high accuracy atomic clocks. Optical E1 (due to
configuration mixing), M1 and E2 transitions are available in HCIs near level
crossings. We present scaling laws for energies and amplitudes that allow us to
make simple estimates of systematic effects of relevance to atomic clocks. HCI
clocks could have some advantages over existing optical clocks because certain
systematic effects are reduced, for example they can have much smaller thermal
shifts. Other effects such as fine-structure and hyperfine splitting are much
larger in HCIs, which can allow for richer spectra. HCIs are excellent
candidates for probing variations in the fine-structure constant, alpha, in
atomic systems as there are transitions with the highest sensitivity to
alpha-variation
Stability of Horava-Lifshitz Black Holes in the Context of AdS/CFT
The anti--de Sitter/conformal field theory (AdS/CFT) correspondence is a
powerful tool that promises to provide new insights toward a full understanding
of field theories under extreme conditions, including but not limited to
quark-gluon plasma, Fermi liquid and superconductor. In many such applications,
one typically models the field theory with asymptotically AdS black holes.
These black holes are subjected to stringy effects that might render them
unstable. Ho\v{r}ava-Lifshitz gravity, in which space and time undergo
different transformations, has attracted attentions due to its power-counting
renormalizability. In terms of AdS/CFT correspondence, Ho\v{r}ava-Lifshitz
black holes might be useful to model holographic superconductors with Lifshitz
scaling symmetry. It is thus interesting to study the stringy stability of
Ho\v{r}ava-Lifshitz black holes in the context of AdS/CFT. We find that
uncharged topological black holes in Ho\v{r}ava-Lifshitz theory are
nonperturbatively stable, unlike their counterparts in Einstein gravity, with
the possible exceptions of negatively curved black holes with detailed balance
parameter close to unity. Sufficiently charged flat black holes for
close to unity, and sufficiently charged positively curved black
holes with close to zero, are also unstable. The implication to the
Ho\v{r}ava-Lifshitz holographic superconductor is discussed.Comment: 15 pages, 6 figures. Updated version accepted by Phys. Rev. D, with
corrections to various misprints. References update
Reply to ``Comment on `Insulating Behavior of -DNA on the Micron Scale' "
In our experiment, we found that the resistance of vacuum-dried -DNA
exceeds at 295 K. Bechhoefer and Sen have raised a number of
objections to our conclusion. We provide counter arguments to support our
original conclusion.Comment: 1 page reply to comment, 1 figur
Optical transitions in highly-charged californium ions with high sensitivity to variation of the fine-structure constant
We study electronic transitions in highly-charged Cf ions that are within the
frequency range of optical lasers and have very high sensitivity to potential
variations in the fine-structure constant, alpha. The transitions are in the
optical despite the large ionisation energies because they lie on the
level-crossing of the 5f and 6p valence orbitals in the thallium isoelectronic
sequence. Cf16+ is a particularly rich ion, having several narrow lines with
properties that minimize certain systematic effects. Cf16+ has very large
nuclear charge and large ionisation energy, resulting in the largest
alpha-sensitivity seen in atomic systems. The lines include positive and
negative shifters
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