| 1. |
- Dehkharghani, A., et al.
(författare)
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Quantum magnetism in strongly interacting one-dimensional spinor Bose systems
- 2015
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322 .- 2045-2322. ; 5
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Tidskriftsartikel (refereegranskat)abstract
- Strongly interacting one-dimensional quantum systems often behave in a manner that is distinctly different from their higher-dimensional counterparts. When a particle attempts to move in a one-dimensional environment it will unavoidably have to interact and 'push' other particles in order to execute a pattern of motion, irrespective of whether the particles are fermions or bosons. A present frontier in both theory and experiment are mixed systems of different species and/or particles with multiple internal degrees of freedom. Here we consider trapped two-component bosons with short-range inter-species interactions much larger than their intra-species interactions and show that they have novel energetic and magnetic properties. In the strongly interacting regime, these systems have energies that are fractions of the basic harmonic oscillator trap quantum and have spatially separated ground states with manifestly ferromagnetic wave functions. Furthermore, we predict excited states that have perfect antiferromagnetic ordering. This holds for both balanced and imbalanced systems, and we show that it is a generic feature as one crosses from few-to many-body systems.
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| 2. |
- Forssen, Christian, 1974, et al.
(författare)
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Living on the edge of stability, the limits of the nuclear landscape
- 2013
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Ingår i: Physica Scripta. - : IOP Publishing. - 1402-4896 .- 0031-8949. ; T152:T152, s. 014022-
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Tidskriftsartikel (refereegranskat)abstract
- A first-principles description of nuclear systems along the drip lines presents a substantial theoretical and computational challenge. In this paper, we discuss the nuclear theory roadmap, some of the key theoretical approaches, and present selected results with a focus on long isotopic chains. An important conclusion, which consistently emerges from these theoretical analyses, is that three-nucleon forces are crucial for both global nuclear properties and detailed nuclear structure, and that many-body correlations due to the coupling to the particle continuum are essential as one approaches particle drip lines. In the quest for a comprehensive nuclear theory, high performance computing plays a key role.
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| 3. |
- 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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| 4. |
- Kim, Youngman, et al.
(författare)
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Ab initio no core full configuration approach for light nuclei
- 2014
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Ingår i: Chiral Symmetry in Hadrons and Nuclei. - : WORLD SCIENTIFIC. - 9789814618229 ; , s. 78-85
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Comprehensive understanding of the structure and reactions of light nuclei poses theoretical and computational challenges. Still, a number of ab initio approaches have been developed to calculate the properties of atomic nuclei using fundamental interactions among nucleons. Among them, we work with the ab initio no core full configuration (NCFC) method and ab initio no core Gamow Shell Model (GSM). We first review these approaches and present some recent results.
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| 5. |
- Kim, Youngman, et al.
(författare)
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Ab initio no core full configuration approach for light nuclei
- 2014
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Ingår i: International Journal of Modern Physics E. - 0218-3013. ; 23:7, s. Article no. 1461004 -
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Tidskriftsartikel (refereegranskat)abstract
- Comprehensive understanding of the structure and reactions of light nuclei poses theoretical and computational challenges. Still, a number of ab initio approaches have been developed to calculate the properties of atomic nuclei using fundamental interactions among nucleons. Among them, we work with the ab initio no core full configuration (NCFC) method and ab initio no core Gamow Shell Model (GSM). We first review these approaches and present some recent results.
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| 6. |
- Lindgren, E. J., et al.
(författare)
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Fermionization of two-component few-fermion systems in a one-dimensional harmonic trap
- 2014
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Ingår i: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 16
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Tidskriftsartikel (refereegranskat)abstract
- The nature of strongly interacting Fermi gases and magnetism is one of the most important and studied topics in condensed-matter physics. Still, there are many open questions. A central issue is under what circumstances strong short-range repulsive interactions are enough to drive magnetic correlations. Recent progress in the field of cold atomic gases allows one to address this question in very clean systems where both particle numbers, interactions and dimensionality can be tuned. Here we study fermionic few-body systems in a one dimensional harmonic trap using a new rapidly converging effective-interaction technique, plus a novel analytical approach. This allows us to calculate the properties of a single spin-down atom interacting with a number of spin-up particles, a case of much recent experimental interest. Our findings indicate that, in the strongly interacting limit, spin-up and spin-down particles want to separate in the trap, which we interpret as a microscopic precursor of one-dimensional ferromagnetism in imbalanced systems. Our predictions are directly addressable in current experiments on ultracold atomic few-body systems.
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| 7. |
- Lundmark, Rikard, 1990, et al.
(författare)
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Tunneling theory for tunable open quantum systems of ultracold atoms in one-dimensional traps
- 2015
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Ingår i: Physical Review A - Atomic, Molecular, and Optical Physics. - 2469-9926 .- 2469-9934. ; 91:4
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Tidskriftsartikel (refereegranskat)abstract
- The creation of tunable open quantum systems is becoming feasible in current experiments with ultracold atoms in low-dimensional traps. In particular, the high degree of experimental control over these systems allows detailed studies of tunneling dynamics, e.g., as a function of the trapping geometry and the interparticle interaction strength. In order to address this exciting opportunity we present a theoretical framework for two-body tunneling based on the rigged Hilbert space formulation. In this approach, bound, resonant, and scattering states are included on an equal footing and we argue that the coupling of all these components is vital for a correct description of the relevant threshold phenomena. In particular, we study the tunneling mechanism for two-body systems in one-dimensional traps and different interaction regimes. We find a strong dominance of sequential tunneling of single particles for repulsive and weakly attractive systems, while there is a signature of correlated pair tunneling in the calculated many-particle flux for strongly attractive interparticle interaction.
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| 8. |
- Papadimitriou, G., et al.
(författare)
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Ab initio no-core Gamow shell model calculations with realistic interactions
- 2013
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Ingår i: Physical Review C - Nuclear Physics. - 2469-9985 .- 2469-9993. ; 88:4
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Tidskriftsartikel (refereegranskat)abstract
- No-core Gamow shell model (NCGSM) is applied to study selected well-bound and unbound states of helium isotopes. This model is formulated on the complex energy plane and, by using a complete Berggren ensemble, treats bound, resonant, and scattering states on equal footing. We use the density matrix renormalization group method to solve the many-body Schrodinger equation. To test the validity of our approach, we benchmarked the NCGSM results against Faddeev and Faddeev-Yakubovsky exact calculations for H-3 and He-4 nuclei. We also performed ab initio NCGSM calculations for the unstable nucleus He-5 and determined the ground-state energy and decay width, starting from a realistic (NLO)-L-3 chiral interaction.
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| 9. |
- Papadimitriou, G., et al.
(författare)
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The No core gamow shell model for ab-initio nuclear structure calculations
- 2014
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Ingår i: EPJ Web of Conferences. - : EDP Sciences. - 2101-6275 .- 2100-014X. ; 66
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Konferensbidrag (refereegranskat)abstract
- We apply the Berggren basis in a No-Core Shell Model framework to calculate ground state (g.s.) energies of 3H, 4He and 5He. In our studies we use the Argonne υ18 and the chiral N3LO potentials, both of which are renormalized via a V low-k process. © Owned by the authors, published by EDP Sciences, 2014.
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| 10. |
- Rotureau, Jimmy, 1976, et al.
(författare)
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Effective Field Theory and the Gamow Shell Model: The 6He Halo Nucleus
- 2013
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Ingår i: Few-Body Systems. - : Springer Science and Business Media LLC. - 1432-5411 .- 0177-7963. ; 54:5-6, s. 725-735
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Tidskriftsartikel (refereegranskat)abstract
- We combine halo/cluster effective field theory (H/CEFT) and the Gamow shell model (GSM) to describe the 0+ ground state of 6He as a three-body halo system. We use two-body interactions for the neutron-alpha particle and two-neutron pairs obtained from H/CEFT at leading order, with parameters determined from scattering in the p3/2 and s0 channels, respectively. The three-body dynamics of the system is solved using the GSM formalism, where the continuum states are incorporated in the shell model valence space. We find that in the absence of three-body forces the system collapses, since the binding energy of the ground state diverges as cutoffs are increased. We show that addition at leading order of a three-body force with a single parameter is sufficient for proper renormalization and to fix the binding energy to its experimental value.
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