| 1. |
- Armstrong, Jeremy, et al.
(författare)
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Interaction Blockade and Pairing in Two-Dimensional Finite Fermion Systems
- 2009
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Ingår i: Few-body Systems. - : Springer Science and Business Media LLC. - 0177-7963 .- 1432-5411. ; 45:2-4, s. 219-222
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Konferensbidrag (refereegranskat)abstract
- The properties of two-component fermionic quantum systems in two dimensions, such as they nowadays may be realized with cold atoms in traps, are studied within the pairing model adapted from nuclear physics. We compare the results with those of a full numerical diagonalization of the many-body Hamiltonian. The chemical potential differences, excitation energies and angular momentum spectra show that when the zero-range attractive interaction is varied in strength, strong odd-even effects, gaps and shell structure emerge.
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| 2. |
- Cremon, Jonas
(författare)
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Test of a Jastrow-type Wavefunction for a Trapped Few-body System in One Dimension
- 2012
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Ingår i: Few-Body Systems. - : Springer Science and Business Media LLC. - 0177-7963 .- 1432-5411. ; 53:3-4, s. 267-269
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Tidskriftsartikel (refereegranskat)abstract
- For a system with interacting quantum mechanical particles in a one-dimensional harmonic oscillator, a trial wavefunction with simple structure based on the solution of the corresponding two-particle system is suggested and tested numerically.With the inclusion of a scaling parameter for the distance between particles, at least for the very small systems tested here the ansatz gives a very good estimate of the ground state energy, with the error being of the order of 1 % of the gap to the first excited state.
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| 3. |
- Cremon, Jonas, et al.
(författare)
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Vortices in small Bose or Fermi systems with repulsive interactions
- 2008
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Ingår i: Few-Body Systems. - : Springer Science and Business Media LLC. - 0177-7963 .- 1432-5411. ; 43:1-4, s. 161-166
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Konferensbidrag (refereegranskat)abstract
- For rotating Bose-Einstein condensates, the occurrence of vortices has been much discussed in the Gross-Pitaevskii approach. Here, we study vortex formation in finite systems with few particles for weak and repulsive two-body interactions, by numerical diagonalization. Vortex formation is surprisingly similar for both (spinless) bosonic and fermionic particles. Breaking the rotational invariance of the Hamiltonian of the system reveals the vortex patterns. A transformation from a many-fermion to a many-boson state is proposed.
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| 4. |
- Deltuva, A., et al.
(författare)
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Universality in Four-Body Scattering
- 2011
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Ingår i: Few-Body Systems. - : Springer Science and Business Media LLC. - 1432-5411 .- 0177-7963. ; 51:2-4, s. 235-247
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Tidskriftsartikel (refereegranskat)abstract
- The four-body system is studied in the limit of large two-body scattering length by solving momentum-space integral equations for the transition operators or, alternatively, configuration-space equations for wave function. A number of universal results for atom-trimer and dimer-dimer scattering observables are found. We furthermore address the question whether the universal four-body systems contain additional states besides the known two S-wave states.
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| 5. |
- Elander, Nils O, et al.
(författare)
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Resonances and Their Relations to Spectral Densities and Scattering Cross Sections in the Schrodinger Formulation
- 2013
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Ingår i: Few-body systems. - : Springer Science and Business Media LLC. - 0177-7963 .- 1432-5411. ; 54:5-6, s. 685-695
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Tidskriftsartikel (refereegranskat)abstract
- The concept of resonances for a two-body single and many channel Schrodinger problem is discussed with respect to the Titchmarsh-Weyl theory. It is argued that the contributions from the entire set of resonances together with the free particle spectral density build the entire spectrum. The implication of this statement on the influence of resonances on a two-body scattering cross section is discussed. It is described how the residues of the S-matrix at a complex resonance energy, i.e. two complex numbers, is used to define its contribution to the cross section. The limitations of the Breit-Wigner approximation is discussed.
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| 6. |
- Elander, Nils, et al.
(författare)
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Quantum Scattering with the Driven Schrödinger Approachand Complex Scaling
- 2009
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Ingår i: Few-body systems. - Heidelberg : Springer Verlag. - 0177-7963 .- 1432-5411. ; 45:2-4, s. 197-201
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Tidskriftsartikel (refereegranskat)abstract
- Quantum scattering calculations of two and three-body systems with Coulomb interaction using thedriven Schrödinger equation combined with exterior complex scaling are discussed. A rigorous formulationfor two-body scattering is reported, and its generalization to three-body scattering is considered.
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| 7. |
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| 8. |
- Feldman, G., et al.
(författare)
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Compton scattering from deuterium and the polarizabilities of the neutron
- 2008
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Ingår i: Few-Body Systems. - : Springer Science and Business Media LLC. - 0177-7963 .- 1432-5411. ; 44:1-4, s. 325-328
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Konferensbidrag (refereegranskat)abstract
- A new program of Compton scattering on deuterium is under way at the tagged-photon facility at MAX-Lab in Lund, Sweden. We will measure differential cross sections between 60A degrees and 150A degrees over the photon energy range 60-115 MeV in 5 MeV steps, with the ultimate goal of obtaining new precision information on the electric and magnetic polarizabilities of the neutron.
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| 9. |
- Floerchinger, Stefan, et al.
(författare)
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Efimov Physics from the Functional Renormalization Group
- 2011
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Ingår i: Few-body systems. - : Springer Science and Business Media LLC. - 0177-7963 .- 1432-5411. ; 51:2-4, SI, s. 153-180
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Tidskriftsartikel (refereegranskat)abstract
- Few-body physics related to the Efimov effect is discussed using the functional renormalization group method. After a short review of renormalization in its modern formulation we apply this formalism to the description of scattering and bound states in few-body systems of identical bosons and distinguishable fermions with two and three components. The Efimov effect leads to a limit cycle in the renormalization group flow. Recently measured three-body loss rates in an ultracold Fermi gas of Li-6 atoms are explained within this framework. We also discuss briefly the relation to the many-body physics of the BCS-BEC crossover for two-component fermions and the formation of a trion phase for the case of three species.
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| 10. |
- Forssen, Christian, 1974, et al.
(författare)
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Strongly Interacting Few-Fermion Systems in a Trap
- 2015
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Ingår i: Few-Body Systems. - : Springer Science and Business Media LLC. - 1432-5411 .- 0177-7963. ; 56:11-12, s. 837-844
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Tidskriftsartikel (refereegranskat)abstract
- Few- and many-fermion systems on the verge of stability, and consisting of strongly interacting particles, appear in many areas of physics. The theoretical modeling of such systems is a very difficult problem. In this work we present a theoretical framework that is based on the rigged Hilbert space formulation. The few-body problem is solved by exact diagonalization using a basis in which bound, resonant, and non-resonant scattering states are included on an equal footing. Current experiments with ultracold atoms offer a fascinating opportunity to study universal properties of few-body systems with a high degree of control over parameters such as the external trap geometry, the number of particles, and even the interaction strength. In particular, particles can be allowed to tunnel out of the trap by applying a magnetic-field gradient that effectively lowers the potential barrier. The result is a tunable open quantum system that allows detailed studies of the tunneling mechanism. In this Paper we introduce our method and present results for the decay rate of two distinguishable fermions in a one-dimensional trap as a function of the interaction strength. In particular, we present for the first time several technical and numerical details of our approach, recently published in Lundmark et al. (Phys Rev A 91:041601, 2015). We also show results from a careful analysis of the numerical convergence.
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