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J Dukelsky

Publications and source records attributed to J Dukelsky.

At least 19 recordsLinked to original sources
PubMed2006

Density matrix renormalization group approach for many-body open quantum systems.

The density matrix renormalization group (DMRG) approach is extended to complex-symmetric density matrices characteristic of many-body open quantum systems. Within the continuum shell model, we investigate the interplay between many-body configuration interaction and coupling to open channels in case of the unbound nucleus (7)He. It is shown that the extended DMRG procedure provides a highly accurate treatment of the coupling to the nonresonant scattering continuum.

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PubMed2006

Integrative models for asymmetric fermi superfluids: emergence of a new exotic pairing phase.

We introduce an exactly solvable model to study the competition between the Larkin-Ovchinnikov-Fulde-Ferrell (LOFF) and breached-pair superfluid in strongly interacting ultracold asymmetric Fermi gases. One can thus investigate homogeneous and inhomogeneous states on equal footing and establish the quantum phase diagram. For certain values of the filling and the interaction strength, the model exhibits a new stable exotic pairing phase which combines an inhomogeneous state with an interior gap to pair excitations. It is proven that this phase is the exact ground state in the strong-coupling limit, while numerical examples in finite lattices show that also at finite interaction strength it can have lower energy than the breached-pair or LOFF states.

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PubMed2006

Exact solution of the isovector neutron-proton pairing Hamiltonian.

The complete exact solution of the T = 1 neutron-proton pairing Hamiltonian is presented in the context of the SO(5) Richardson-Gaudin model with nondegenerate single-particle levels and including isospin symmetry-breaking terms. The power of the method is illustrated with a numerical calculation for for 64Ge for a pf + g9/2 model space which is out of reach of modern shell-model codes.

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PubMed2004

Phase diagram of the proton-neutron interacting boson model.

We study the phase diagram of the proton-neutron interacting boson model with special emphasis on the phase transitions leading to triaxial phases. The existence of a new critical point between spherical and triaxial shapes is reported.

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PubMed2004

Stringent numerical test of the Poisson distribution for finite quantum integrable Hamiltonians.

Using a class of exactly solvable models based on the pairing interaction, we show that it is possible to construct integrable Hamiltonians with a Wigner distribution of nearest-neighbor level spacings. However, these Hamiltonians involve many-body interactions and the addition of a small integrable perturbation very quickly leads the system to a Poisson distribution. Besides this exceptional case, we show that the accumulated distribution of an ensemble of random integrable two-body pairing Hamiltonians is in perfect agreement with the Poisson limit. These numerical results for quantum integrable Hamiltonians provide a further empirical confirmation of the work of Berry and Tabor in the semiclassical limit.

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PubMed2004

Exactly solvable models for atom-molecule Hamiltonians.

We present a family of exactly solvable generalizations of the Jaynes-Cummings model involving the interaction of an ensemble of SU(2) or SU(1,1) quasispins with a single boson field. They are obtained from the trigonometric Richardson-Gaudin models by replacing one of the SU(2) or SU(1,1) degrees of freedom by an ideal boson. The application to a system of bosonic atoms and molecules is reported.

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PubMed2003

Quantum phase transitions in the interacting boson model: integrability, level repulsion, and level crossing.

We study the quantum phase transition mechanisms that arise in the interacting boson model. We show that the second-order nature of the phase transition from U(5) to O(6) may be attributed to quantum integrability, whereas all the first-order phase transitions of the model are due to level repulsion with one singular point of level crossing. We propose a model Hamiltonian with a true first-order phase transition for finite systems due to level crossings.

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PubMed2002

Electrostatic mapping of nuclear pairing.

The traditional nuclear pairing problem is shown to be in one-to-one correspondence with a classical electrostatic problem in two dimensions. We make use of this analogy in a series of calculations in the tin region, showing that the extremely rich phenomenology that appears in this classical problem can provide interesting new insights into nuclear superconductivity.

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PubMed2001

Class of exactly solvable pairing models.

We present three classes of exactly solvable models for fermion and boson systems, based on the pairing interaction. These models are solvable in any dimension. As an example we show the first results for fermions interacting with repulsive pairing forces in a two-dimensional square lattice. In spite of the repulsive pairing force the exact results show attractive pair correlations.

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PubMed2001

New mechanism for the enhancement of sd dominance in interacting boson models.

We introduce an exactly solvable model for interacting bosons that extend up to high spin and interact through a repulsive pairing force. The model exhibits a phase transition to a state with almost complete sd dominance. The repulsive pairing interaction that underlies the model has a natural microscopic origin in the Pauli exclusion principle between constituent nucleons. As such, repulsive pairing between bosons seems to provide a new mechanism for the enhancement of sd dominance, giving further support for the validity of the sd interacting boson model.

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