| 1. |
|
|
| 2. |
- Cetoli, Alberto, 1979-, et al.
(författare)
-
Correlations and superfluidity of a one-dimensional Bose gas in a quasiperiodic potential
- 2010
-
Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - : American Physical Society. - 1050-2947 .- 1094-1622. ; 81:6, s. 063635-063642
-
Tidskriftsartikel (refereegranskat)abstract
- We consider the correlations and superfluid properties of a Bose gas in an external potential. Using a Bogoliubov scheme, we obtain expressions for the correlation function and the superfluid density in an arbitrary external potential. These expressions are applied to a one-dimensional system at zero temperature subject to a quasiperiodic modulation. The critical parameters for the Bose glass transition are obtained using two different criteria and the results are compared. The Lifshitz glass is seen to be the limiting case for vanishing interactions.
|
|
| 3. |
|
|
| 4. |
- Dion, Claude, 1970-, et al.
(författare)
-
Bimodal momentum distribution of laser-cooled atoms in optical lattices
- 2016
-
Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 93:5
-
Tidskriftsartikel (refereegranskat)abstract
- We study, numerically and experimentally, the momentum distribution of atoms cooled in optical lattices. Using semiclassical simulations, we show that this distribution is bimodal, made up of a central feature corresponding to "cold," trapped atoms, with tails of "hot," untrapped atoms, and that this holds true also for very shallow potentials. Careful analysis of the distribution of high-momentum untrapped atoms, both from simulations and experiments, shows that the tails of the distribution do not follow a normal law, hinting at a power-law distribution and nonergodic behavior. We also revisit the phenomenon leading to the existence of an optimal cooling point, i.e., a potential depth below which the temperature of the atoms starts increasing.
|
|
| 5. |
- Eriksson, Daniel, et al.
(författare)
-
Possibility to measure elastic photon-photon scattering in vacuum
- 2004
-
Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 70:1, s. 013808-
-
Tidskriftsartikel (refereegranskat)abstract
- Photon-photon scattering in vacuum due to the interaction with virtual electron-positron pairs is a consequence of quantum electrodynamics. A way for detecting this phenomenon has been devised based on interacting modes generated in microwave wave guides or cavities [G. Brodin, M. Marklund, and L. Stenflo, Phys. Rev. Lett. 87, 171801 (2001)]. Here we materialize these ideas, suggest a concrete cavity geometry, make quantitative estimates and propose experimental details. It is found that detection of photon-photon scattering can be within the reach of present day technology.
|
|
| 6. |
- Harvey, Christopher, 1982, et al.
(författare)
-
Narrowing of the emission angle in high-intensity Compton scattering
- 2016
-
Ingår i: Physical Review A - Atomic, Molecular, and Optical Physics. - : American Physical Society. - 2469-9926 .- 2469-9934 .- 1050-2947 .- 1094-1622. ; 93:2
-
Tidskriftsartikel (refereegranskat)abstract
- We consider the emission spectrum of high-energy electrons in an intense laser field. At high intensities (a_0 \sim 200) we find that the QED theory predicts a narrower angular spread of emissions than the classical theory. This is due to the classical theory overestimating the energy loss of the particles, resulting in them becoming more susceptible to reflection in the laser pulse.
|
|
| 7. |
- Harvey, Christopher, et al.
(författare)
-
Radiation damping in pulsed Gaussian beams
- 2012
-
Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - : American Physical Society. - 1050-2947 .- 1094-1622. ; 85:1, s. 013412-013424
-
Tidskriftsartikel (refereegranskat)abstract
- We consider the effects of radiation damping on the electron dynamics in a Gaussian-beam model of a laser field. For high intensities, i.e., with dimensionless intensity a0≫1, it is found that the dynamics divides into three regimes. For low-energy electrons (low initial γ factor, γ0) the radiation damping effects are negligible. At higher energies, but still at 2γ00, the damping alters the final displacement and the net energy change of the electron. For 2γ0>a0 one is in a regime of radiation-reaction-induced electron capture. This capture is found to be stable with respect to the spatial properties of the electron beam and results in a significant energy loss of the electrons. In this regime the plane-wave model of the laser field provides a good description of the dynamics, whereas for lower energies the Gaussian-beam and plane-wave models differ significantly. Finally the dynamics is considered for the case of an x-ray free-electron laser field. It is found that the significantly lower intensities of such fields inhibit the damping effects.
|
|
| 8. |
- Ilderton, Anton, et al.
(författare)
-
Pair annihilation in laser pulses : Optical versus x-ray free-electron laser regimes
- 2011
-
Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - New York, N.Y. : Publ. by the American Physical Society through the American Institute of Physics. - 1050-2947 .- 1094-1622. ; 84:3, s. 032119-
-
Tidskriftsartikel (refereegranskat)abstract
- We discuss the theory and phenomenology of pair annihilation, within an ultrashort laser pulse, to a single photon. The signature of this process is the unidirectional emission of single photons with a fixed energy. We show that the cross section is significantly larger than for two-photon pair annihilation in vacuum, with x-ray free-electron laser parameters admitting a much clearer signal than optical beams.
|
|
| 9. |
|
|
| 10. |
- Jonsell, Svante, et al.
(författare)
-
Strong Nuclear Force in Cold Antihydrogen : Helium Collisions
- 2004
-
Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - New York, N.Y. : Publ. by the American Physical Society through the American Institute of Physics. - 1050-2947 .- 1094-1622. ; 70:6, s. 062708-
-
Tidskriftsartikel (refereegranskat)abstract
- We calculate cross sections for elastic scattering and annihilation in antihydrogen-helium collisions at low energies. The calculations are based on the Born-Oppenheimer approximation, and incorporate the effects of the strong interaction through a scattering length approach. We find that the strong nuclear force not only causes significant annihilation, but also cannot be neglected in the elastic channel. In the zero energy limit we obtain the scattering length a=−7.69−3.80i a.u. for ground state antihydrogen-helium collisions. Annihilation is found to dominate over elastic scattering up to a temperature about 3 K. Loosely bound metastable antihydrogen-helium states are also investigated, and it is found that a number of relatively long-lived states with up to three units of angular momentum exist.
|
|
