26,665 research outputs found
Dynamic polarizabilities and related properties of clock states of ytterbium atom
We carry out relativistic many-body calculations of the static and dynamic
dipole polarizabilities of the ground 6s^2 ^1S_0 and the first excited states of Yb. With these polarizabilities, we compute several
properties of Yb relevant to optical lattice clocks operating on the 6s^2
^1S_0 - 6s6p ^3P^o_0 transition. We determine (i) the first four {\em magic}
wavelengths of the laser field for which the frequency of the clock transition
is insensitive to the laser intensity. While the first magic wavelength is
known, we predict the second, the third and the forth magic wavelengths to be
551 nm, 465 nm, and 413 nm. (ii) We reevaluate the effect of black-body
radiation on the frequency of the clock transition, the resulting clock shift
at being Hz. (iii) We compute long-range
interatomic van der Waals coefficients (in a.u.) C_6(6s^2 ^1S_0 +6s^2 ^1S_0) =
1909(160), C_6(6s^2 ^1S_0 + 6s6p ^3P_0) =2709(338) , and . Finally, we determine the atom-wall interaction
coefficients (in a.u.), C_3 (6s^2 ^1S_0) =3.34 and .
We also address and resolve a disagreement between previous calculations of the
static polarizability of the ground state.Comment: 11 pages, 1 figur
A New Kind of Uniformly Accelerated Reference Frames
A new kind of uniformly accelerated reference frames with a line-element
different from the M{\o}ller and Rindler ones is presented, in which every
observer at consts. has the same constant acceleration. The laws of
mechanics are checked in the new kind of frames. Its thermal property is
studied. The comparison with the M{\o}ller and Rindler uniform accelerated
reference frames is also made.Comment: 10 pages, 2 figures. to appear in Int. J. Mod. Phys.
Pre-K-Edge Structure on Anomalous X-Ray Scattering in LaMnO3
We study the pre-K-edge structure of the resonant X-ray scattering for
forbidden reflections (anomalous scattering) in LaMnO3, using the band
calculation based on the local density approximation. We find a two-peak
structure with an intensity approximately 1/100 of that of the main peak. This
originates from a mixing of 4p states of Mn to 3d states of neighboring Mn
sites. The effect is enhanced by an interference with the tail of the main
peak. The effect of the quadrupole transition is found to be one order of
magnitude smaller than that of the dipole transition, modifying slightly the
azimuthal-angle dependence.Comment: 4 pages, 5 figures, submitted to J. Phys. Soc. Jp
Separation of colour degree of freedom from dynamics in a soliton cellular automaton
We present an algorithm to reduce the coloured box-ball system, a one
dimensional integrable cellular automaton described by motions of several
colour (kind) of balls, into a simpler monochrome system. This algorithm
extracts the colour degree of freedom of the automaton as a word which turns
out to be a conserved quantity of this dynamical system. It is based on the
theory of crystal basis and in particular on the tensor products of sl_n
crystals of symmetric and anti-symmetric tensor representations.Comment: 19 page
Anomalous He-Gas High-Pressure Studies on Superconducting LaO1-xFxFeAs
AC susceptibility measurements have been carried out on superconducting
LaO1-xFxFeAs for x=0.07 and 0.14 under He-gas pressures to about 0.8 GPa. Not
only do the measured values of dTc/dP differ substantially from those obtained
in previous studies using other pressure media, but the Tc(P) dependences
observed depend on the detailed pressure/temperature history of the sample. A
sizeable sensitivity of Tc(P) to shear stresses provides a possible
explanation
Diverse Supernova Sources for the r-Process
(Abridged) It is shown that a semi-quantitative agreement with the gross
solar r-process abundance pattern near and above mass number A=130 can be
obtained by a superposition of two distinctive kinds of supernova r-process
events. These correspond to a low frequency case L and a high frequency case H,
which takes into account the low abundance of I129 and the high abundance of
Hf182 in the early solar nebula. The lifetime of Hf182 associates the events in
case H with the most common Type II supernovae. These events would be mainly
responsible for the r-process nuclei near and above A=195. They would also make
a significant amount of the nuclei between A=130 and 195, including Hf182, but
very little I129. In order to match the solar r-process abundance pattern and
to satisfy the I129 and Hf182 constraints, the events in case L, which would
make the r-process nuclei near A=130 and the bulk of those between A=130 and
195, must occur 10 times less frequently but eject 10--20 times more r-process
material in each event. We speculate that the usual neutron star remnants, and
hence prolonged ejection of r-process material, are associated with the events
in case L, whereas the more frequently occurring events in case H have ejection
of other r-process material terminated by black hole formation during the
neutrino cooling phase of the protoneutron star.Comment: 23 pages, AAS LATEX, 8 Postscript figure
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