arXiv subjects

Peter Schuck

Publications and source records attributed to Peter Schuck.

60 records · Page 4Linked to original sources

arXiv2003

Dilute Multi Alpha Cluster States in Nuclei

Dilute multi $α$ cluster condensed states with spherical and axially deformed shapes are studied with the Gross-Pitaevskii equation and Hill-Wheeler equation, where the $α$ cluster is treated as a structureless boson. Applications to self-conjugate $4N$ nuclei show that the dilute $Nα$ states of $^{12}$C to $^{40}$Ca with $J^π=0^+$ appear in the energy region from threshold up to about 20 MeV, and the critical number of $α$ bosons that the dilute $Nα$ system can sustain as a self-bound nucleus is estimated roughly to be $N_{cr}\sim10$. We discuss the characteristics of the dilute $Nα$ states with emphasis on the $N$ dependence of their energies and rms radii.

nucl-th↗

arXiv2002

Slow rotation of a superfluid trapped Fermi gas

The moment of inertia, Theta, is one of the possible observables for the experimental determination whether a trapped Fermi system has reached the BCS transition or not. In this article we investigate in detail the temperature dependence of Theta below the critical temperature T_c. Special care is taken to account for the small size of the system, i.e., for the fact that the trapping frequency hbar omega is of the same order of magnitude as the gap Delta. It is shown that the usual transport approach, corresponding to the leading order of an expansion in powers of hbar, is not accurate in this case. It turns out that Theta does not change rapidly if T becomes smaller than T_c, but it rather decreases slowly. Qualitatively this behavior can be explained within the two-fluid model, which again corresponds to the leading order in hbar. Quantitatively we find deviations from the two-fluid model due to the small system size.

cond-mat↗

arXiv2002

Description of 8Be as Deformed Gas-like Two-Alpha-Paricle States

In order to study non-zero spin excitations of the recently proposed alpha-cluster condensation in the self-conjugate 4n nuclei, spatial deformation is introduced into the model wave function of the alpha-cluster condensate. The rotational band states of 8Be are investigated as a first step of a test case for the study of the deformation of the alpha-cluster condensate. Calculations reproduce well the binding energy of the 0+ ground state and also the excitation energy of the 2+ state. Our 0+ wave function is found to be almost exactly equal to the 0+ wave function obtained by the generator coordinate method using Brink's 2 alpha wave function. The study shows that both the 0+ ground and 2+ excited states can be considered as having a gas-like (i.e. weakly bound) 2 alpha-cluster structure. As for the 0+ ground state, the change of the wave function, due to the introduction of the deformation, is found to be very small.

nucl-th↗

arXiv2001

Fully Self-consistent RPA description of the many level pairing model

The Self-Consistent RPA (SCRPA) equations in the particle-particle channel are solved without any approximation for the picket fence model. The results are in excellent agreement with the exact solutions found with the Richardson method. Particularly interesting features are that screening corrections reverse the sign of the interaction and that SCRPA yields the exact energies in the case of two levels with two particles.

nucl-th↗

arXiv1998

Dyson Equation Approach to Many-Body Greens Functions and Self-Consistent RPA, First Application to the Hubbard Model

An approach for particle-hole correlation functions, based on the so-called SCRPA, is developed. This leads to a fully self-consistent RPA-like theory which satisfies the $f$-sum rule and several other theorems. As a first step, a simpler self-consistent approach, the renormalized RPA, is solved numerically in the one-dimensional Hubbard model. The charge and the longitudinal spin susceptibility, the momentum distribution and several ground state properties are calculated and compared with the exact results. Especially at half filling, our approach provides quite promising results and matches the exact behaviour apart from a general prefactor. The strong coupling limit of our approach can be described analytically.

cond-mat.str-el↗

arXiv1993

Coexistence of Regular Undamped Nuclear Dynamics with Intrinsic Chaoticity

We study the conditions under which the nucleons inside a deformed nucleus can undergo chaotic motion. To do this we perform self-consistent calculations in semiclassical approximation utilizing a multipole-multipole interaction of the Bohr-Mottelson type for quadrupole and octupole deformations. For the case of harmonic and non-harmonic static potentials, we find that both multipole deformations lead to regular motion of the collective coordinate, the multipole moment of deformation. However, despite this regular collective motion, we observe chaotic single particle dynamics.

nucl-th↗