Describing mixed spin-space entanglement of pure states of indistinguishable particles using an occupation-number basis

Focusing on systems of many identical particles, Chapter 2 introduces appropriate operators to describe their properties in terms of Schwinger’s “measurement symbols.” The latter are then factorized into “creation” and “annihilation” operators, whose fundamental properties and commutation/anticommutation relations are derived in conjunction with the Pauli exclusion principle. This leads to “second quantization” with the Hamiltonian, number, linear and angular momentum operators expressed in terms of the annihilation and creation operators, as well as the occupation number representation. Finally, the concept of coherent states, as eigenstates of the annihilation operator, having minimum uncertainty, is introduced and discussed in detail.

Download Full-text

Scattering in Terms of Bohmian Conditional Wave Functions for Scenarios with Non-Commuting Energy and Momentum Operators

Entropy ◽

10.3390/e23040408 ◽

2021 ◽

Vol 23 (4) ◽

pp. 408

Author(s):

Matteo Villani ◽

Guillermo Albareda ◽

Carlos Destefani ◽

Xavier Cartoixà ◽

Xavier Oriols

Keyword(s):

Single Particle ◽

Degrees Of Freedom ◽

Single Photon ◽

Open Quantum Systems ◽

Wave Functions ◽

Practical Application ◽

Light Matter Interaction ◽

Pure States ◽

Energy And Momentum ◽

Full Quantum

Without access to the full quantum state, modeling quantum transport in mesoscopic systems requires dealing with a limited number of degrees of freedom. In this work, we analyze the possibility of modeling the perturbation induced by non-simulated degrees of freedom on the simulated ones as a transition between single-particle pure states. First, we show that Bohmian conditional wave functions (BCWFs) allow for a rigorous discussion of the dynamics of electrons inside open quantum systems in terms of single-particle time-dependent pure states, either under Markovian or non-Markovian conditions. Second, we discuss the practical application of the method for modeling light–matter interaction phenomena in a resonant tunneling device, where a single photon interacts with a single electron. Third, we emphasize the importance of interpreting such a scattering mechanism as a transition between initial and final single-particle BCWF with well-defined central energies (rather than with well-defined central momenta).

Download Full-text

Predictors of contraceptive method discontinuation among adolescent and young women in three West African countries (Burkina Faso, Mali, and Niger)

BMC Women s Health ◽

10.1186/s12905-021-01326-0 ◽

2021 ◽

Vol 21 (1) ◽

Author(s):

Adja Mariam Ouédraogo ◽

Adama Baguiya ◽

Rachidatou Compaoré ◽

Kadari Cissé ◽

Désiré Lucien Dahourou ◽

...

Keyword(s):

Marital Status ◽

Burkina Faso ◽

Young Women ◽

Contraceptive Method ◽

Occupation Number ◽

Education Level ◽

Demographic And Health Surveys ◽

Contraceptive Methods ◽

Unintended Pregnancies ◽

Contraceptive Discontinuation

Abstract Background The effective use of contraception among adolescents and young women can reduce the risk of unintended pregnancies. However, the prevalence of contraceptive use remains low in this age group. The objective of this study was to estimate the rate of contraceptive method discontinuation among adolescents and young women and to identify its associated factors in Burkina Faso, Mali, and Niger. Method This was a secondary analysis of data from Demographic and Health Surveys of Burkina Faso (2010), Mali (2012–2013), and Niger (2012). The dependent variable was the time to discontinuation of contraceptive methods. Independent variables were represented by sociodemographic, socioeconomic, and cultural characteristics. Mixed-effects survival analysis with proportional hazards was used to identify the predictors. Results A total of 2,264 adolescents and young women aged 15 to 24 years were included in this analysis, comprising 1,100 in Burkina Faso, 491 in Mali, and 673 in Niger. Over the last five years, the overall contraceptive discontinuation rate was 68.7% (50.1% in Burkina Faso, 59.6% in Mali, and 96.8% in Niger). At the individual level, in Burkina Faso, occupation (aHR = 0.33), number of living children (aHR = 2.17), marital status (aHR = 2.93), and region (aHR = 0.54) were associated with contraceptive discontinuation. Except for education and marital status, we found the same factors in Mali. In Niger, a women's education level (aHR = 1.47) and her partner (aHR = 0.52) were associated with discontinuation. At the community level, the region of origin was associated with discontinuation of contraceptive methods. Conclusion Most adolescents and young women experienced at least one episode of discontinuation. Discontinuation of contraceptive methods is associated with the level of education, occupation, number of children, marital status, and desire for children with the spouse. Promotion of contraceptive interventions should target adolescents, young women, and their partners, as well as those with a low education level or in a union.

Download Full-text

np-Pair Correlations in the Isovector Pairing Model

Symmetry ◽

10.3390/sym13081405 ◽

2021 ◽

Vol 13 (8) ◽

pp. 1405

Author(s):

Feng Pan ◽

Yingwen He ◽

Lianrong Dai ◽

Chong Qi ◽

Jerry P. Draayer

Keyword(s):

Binding Energy ◽

Occupation Number ◽

Mean Field ◽

Energy Difference ◽

Binding Energies ◽

Pair Correlations ◽

Isospin Symmetry Breaking ◽

Pairing Model ◽

Proton Pairing ◽

Spin Basis

A diagonalization scheme for the shell model mean-field plus isovector pairing Hamiltonian in the O(5) tensor product basis of the quasi-spin SUΛ(2) ⊗ SUI(2) chain is proposed. The advantage of the diagonalization scheme lies in the fact that not only can the isospin-conserved, charge-independent isovector pairing interaction be analyzed, but also the isospin symmetry breaking cases. More importantly, the number operator of the np-pairs can be realized in this neutron and proton quasi-spin basis, with which the np-pair occupation number and its fluctuation at the J = 0+ ground state of the model can be evaluated. As examples of the application, binding energies and low-lying J = 0+ excited states of the even–even and odd–odd N∼Z ds-shell nuclei are fit in the model with the charge-independent approximation, from which the neutron–proton pairing contribution to the binding energy in the ds-shell nuclei is estimated. It is observed that the decrease in the double binding-energy difference for the odd–odd nuclei is mainly due to the symmetry energy and Wigner energy contribution to the binding energy that alter the pairing staggering patten. The np-pair amplitudes in the np-pair stripping or picking-up process of these N = Z nuclei are also calculated.

Download Full-text