Comparative studies of dipole polarizabilities in Sr+^+, Ba+^+ and Ra+^+ and their applications to optical clocks

Static dipole polarizabilities are calculated in the ground and metastable states of Sr$^+$, Ba$^+$ and Ra$^+$ using the relativistic coupled-cluster method. Trends of the electron correlation effects are investigated in these atomic ions. We also estimate the Stark and black-body radiation shifts from these results for these systems for the transitions proposed for the optical frequency standards and compare them with available experimental data.Comment: 10 pages, 1 figur

Formation of Pairing Fields in Resonantly Coupled Atomic and Molecular Bose-Einstein Condensates

In this paper, we show that pair-correlations may play an important role in the quantum statistical properties of a Bose-Einstein condensed gas composed of an atomic field resonantly coupled with a corresponding field of molecular dimers. Specifically, pair-correlations in this system can dramatically modify the coherent and incoherent transfer between the atomic and molecular fields.Comment: 4 pages, 4 figure

Chiral two-pion exchange and proton-proton partial-wave analysis

The chiral two-pion exchange component of the long-range pp interaction is studied in an energy-dependent partial-wave analysis. We demonstrate its presence and importance, and determine the chiral parameters c_i (i=1,3,4). The values agree well with those obtained from pion-nucleon amplitudes.Comment: 13 pages, no figure

Solitons in coupled atomic-molecular Bose-Einstein condensates in a trap

We consider coupled atomic-molecular Bose-Einstein condensate system in a quasi-one-dimensional trap. In the vicinity of a Feshbach resonance the system can reveal soliton-like behavior. We analyze bright soliton solutions for the system in the trap and in the presence of the interactions between particles. We show that with increasing number of particles in the system two bright soliton solutions start resembling dark soliton profiles known in an atomic Bose-Einstein condensate with repulsive interactions between atoms. We analyze also methods for experimental preparation and detection of the soliton states.Comment: 7 pages, 7 figures, published versio

Chiral perturbation theory for electroweak reactions on deuterium

I summarize two recent applications of chiral perturbation theory to electromagnetic reactions on deuterium: elastic electron-deuteron scattering, and Compton scattering on deuterium. Both calculations have now been carried out to three orders in the chiral expansion. The expansion shows good convergence and is able to reproduce data for q < 600 MeV in e-d and for omega=55-95 MeV in gamma-d. These results demonstrate that ChiPT can be used to reliably compute operators and wave functions for low-momentum-transfer reactions in light nuclear systems.Comment: 10 pages, 6 figures. Write-up of invited talk at INT Workshop on "Nuclear Forces and the Quantum Many-Body Problem", October 4-8, 200

Degenerate fermion gas heating by hole creation

Loss processes that remove particles from an atom trap leave holes behind in the single particle distribution if the trapped gas is a degenerate fermion system. The appearance of holes increases the temperature and we show that the heating is (i) significant if the initial temperature is well below the Fermi temperature $T_{F}$, and (ii) increases the temperature to $T \geq T_{F}/4$ after half of the system's lifetime, regardless of the initial temperature. The hole heating has important consequences for the prospect of observing Cooper-pairing in atom traps.Comment: to be published in PR

Fermi-Bose quantum degenerate ^40 K - ^87 Rb mixture with attractive interaction

We report on the achievement of simultaneous quantum degeneracy in a mixed gas of fermionic ^40 K and bosonic ^87 Rb. Potassium is cooled to 0.3 times the Fermi temperature by means of an efficient thermalization with evaporatively cooled rubidium. Direct measurement of the collisional cross-section confirms a large interspecies attraction. This interaction is shown to affect the expansion of the Bose-Einstein condensate released form the magnetic trap, where it is immersed in the Fermi sea.Comment: 5 pages, 4 figures, replaced one figure plus some change

Investigations of Ra+^+ properties to test possibilities of new optical frequency standards

The present work tests the suitability of the narrow transitions $7s \ ^2S_{1/2} \to 6d ^2D_{3/2}$and$7s ^2S_{1/2} \to 6d ^2D_{5/2}$in Ra$^+$for optical frequency standard studies. Our calculations of the lifetimes of the metastable$6d$states using the relativistic coupled-cluster theory suggest that they are sufficiently long for Ra$^+$ to be considered as a potential candidate for an atomic clock. This is further corroborated by our studies of the hyperfine interactions, dipole and quadrupole polarizabilities and quadrupole moments of the appropriate states of this system.Comment: Latex files, 5 pages, 1 figur

Can we extract the pion electromagnetic form factor from a t-channel diagram only?

We show that we are able to extract the pion electromagnetic form factor by using the recent charged pion electroproduction data from JLab and a simple t-channel diagram. For this purpose we have performed the Q2-independent and dependent analyses. The result of the first analysis is in good agreement with those of previous works and fit the Maris and Tandy model as well as the monopole parameterization which describes a pion radius of 0.672 fm. The result of the second analysis corroborates the findings in the first analysis. Our findings therefore provide a direct proof that at the given kinematics the t-channel diagram really dominates the process. This could also set a new constraint to the phenomenological models that try to describe the process.Comment: 13 pages, 6 figure