16 research outputs found
Drag dynamics in one-dimensional Fermi systems
We study drag dynamics of several fermions in a fermion cloud in
one-dimensional continuous systems, with particular emphasis on the non-trivial
quantum many-body effects in systems whose parameters change gradually in real
time. We adopt the Fermi--Hubbard model and the time-dependent density matrix
renormalization group method to calculate the drag force on a trapped fermion
cluster in a cloud of another fermion species with contact interaction. The
simulation result shows that a non-trivial peak in the resistance force is
observed in the high cloud density region, which implies a criterion of
effective ways in diffusive transport in a fermion cloud. We compare the DMRG
simulation result with a mean-field result, and it is suggested that some
internal degrees of freedom have a crucial role in the excitation process when
the cloud density is high. This work emphasizes the difference between the
full-quantum calculation and the semiclassical calculation, which is the
quantum effects, in slow dynamics of many-body systems bound in a fermion
cloud.Comment: 7 pages, 8 figure
Collision of one-dimensional fermion clusters
We study cluster-cluster collisions in one-dimensional Fermi systems with
particular emphasis on the non-trivial quantum effects of the collision
dynamics. We adopt the Fermi-Hubbard model and the time-dependent density
matrix renormalization group method to simulate collision dynamics between two
fermion clusters of different spin states with contact interaction. It is
elucidated that the quantum effects become extremely strong with the
interaction strength, leading to the transmittance much more enhanced than
expected from semiclassical approximation. We propose a concise model based on
one-to-one collisions, which unveils the origin of the quantum effects and also
explains the overall properties of the simulation results clearly. Our concise
model can quite widely describe the one-dimensional collision dynamics with
contact interaction. Some potential applications, such as repeated collisions,
are addressed.Comment: 5 pages, 5 figure
Quantum effects on one-dimensional collision dynamics of fermion clusters
Recently, many experiments with cold atomic gases have been conducted from
interest in the non-equilibrium dynamics of correlated quantum systems. Of
these experiments, the mixing dynamics of fermion clusters motivates us to
research cluster-cluster collision dynamics in one-dimensional Fermi systems.
We adopt the one-dimensional Fermi-Hubbard model and apply the time-dependent
density matrix renormalization group method. We simulate collisions between two
fermion clusters of spin-up and spin-down, and calculate reflectance of the
clusters R changing the particle number in each cluster and the interaction
strength between two fermions with up and down spins. We also evaluate the
quasi-classical (independent collision) reflectance R^{qc} to compare it with
R. The quasi-classical picture is quantitatively valid in the limit of weak
interaction, but it is not valid when interaction is strong.Comment: 3 pages, 4 figures, submitted to the proceedings for 26th
International Conference on Low Temperature Physics (LT26
Isotope production in proton-, deuteron-, and carbon-induced reactions on Nb 93 at 113 MeV/nucleon
Isotope-production cross sections for p-, d-, and C-induced spallation reactions on Nb93 at 113 MeV/nucleon were measured using the inverse-kinematics method employing secondary targets of CH2, CD2, and C. The measured cross sections for Mo90, Nb90, Y86,88 produced by p-induced reactions were found to be consistent with those measured by the conventional activation method. We performed benchmark tests of the reaction models INCL-4.6, JQMD, and JQMD-2.0 implemented in the Particle and Heavy Ion Transport code System (PHITS) and of the nuclear data libraries JENDL-4.0/HE, TENDL-2017, and ENDF/B-VIII.0. The model calculations also showed generally good agreement with the measured isotope-production cross sections for p-, d-, and C-induced reactions. It also turns out that, among the three nuclear data libraries, JENDL-4.0/HE provides the best agreement with the measured data for the p-induced reactions. We compared the present Nb93 data with the Zr93 data, that were measured previously by the same inverse kinematics method (Kawase et al., Prog. Theor. Exp. Phys. 2017, 093D03 (2017)2050-391110.1093/ptep/ptx110), with particular attention to the effect of neutron-shell closure on isotope production in p- and d-induced spallation reactions. The isotopic distributions of the measured production cross sections in the Zr93 data showed noticeable jumps at neutron number N=50 in the isotopic chains of ÎZ=0 and -1, whereas no such jump appeared in isotopic chain of ÎZ=0 in the Nb93 data. From INCL-4.6 + GEM calculations, we found that the jump formed in the evaporation process is smeared out by the intranuclear cascade component in Nb91 produced by the Nb93(p,p2n) and (d,d2n) reactions on Nb93. Moreover, for Nb93, the distribution of the element-production cross sections as a function of the change in proton number ÎZ is shifted to smaller ÎZ than for Zr93, because the excited Nb prefragments generated by the cascade process are more likely to emit protons than the excited Zr prefragments, due to the smaller proton-separation energies of the Nb isotopes
Cross sections for nuclide production in proton- and deuteron-induced reactions on 93
Isotopic production cross sections were measured for proton- and deuteron-induced reactions on 93Nb by means of the inverse kinematics method at RIKEN Radioactive Isotope Beam Factory. The measured production cross sections of residual nuclei in the reaction 93Nb + p at 113âMeV/u were compared with previous data measured by the conventional activation method in the proton energy range between 46 and 249âMeV. The present inverse kinematics data of four reaction products (90Mo, 90Nb, 88Y, and 86Y) were in good agreement with the data of activation measurement. Also, the model calculations with PHITS describing the intra-nuclear cascade and evaporation processes generally well reproduced the measured isotopic production cross sections