462 research outputs found
Critical Temperature for -Particle Condensation within a Momentum Projected Mean Field Approach
Alpha-particle (quartet) condensation in homogeneous spin-isospin symmetric
nuclear matter is investigated. The usual Thouless criterion for the critical
temperature is extended to the quartet case. The in-medium four-body problem is
strongly simplified by the use of a momentum projected mean field ansatz for
the quartet. The self-consistent single particle wave functions are shown and
discussed for various values of the density at the critical temperature
Stability and structure of two coupled boson systems in an external field
The lowest adiabatic potential expressed in hyperspherical coordinates is
estimated for two boson systems in an external harmonic trap. Corresponding
conditions for stability are investigated and the related structures are
extracted for zero-range interactions. Strong repulsion between non-identical
particles leads to two new features, respectively when identical particles
attract or repel each other. For repulsion new stable structures arise with
displaced center of masses. For attraction the mean-field stability region is
restricted due to motion of the center of masses
Dynamical properties of dipolar Fermi gases
We investigate dynamical properties of a one-component Fermi gas with
dipole-dipole interaction between particles. Using a variational function based
on the Thomas-Fermi density distribution in phase space representation, the
total energy is described by a function of deformation parameters in both real
and momentum space. Various thermodynamic quantities of a uniform dipolar Fermi
gas are derived, and then instability of this system is discussed. For a
trapped dipolar Fermi gas, the collective oscillation frequencies are derived
with the energy-weighted sum rule method. The frequencies for the monopole and
quadrupole modes are calculated, and softening against collapse is shown as the
dipolar strength approaches the critical value. Finally, we investigate the
effects of the dipolar interaction on the expansion dynamics of the Fermi gas
and show how the dipolar effects manifest in an expanded cloud.Comment: 14 pages, 8 figures, submitted to New J. Phy
Density matrix renormalization group for the Berezinskii-Kosterlitz-Thouless transition of the 19-vertex model
We embody the density matrix renormalization group (DMRG) method for the
19-vertex model on a square lattice in order to investigate the
Berezinskii-Kosterlitz-Thouless transition. Elements of the transfer matrix of
the 19-vertex model are classified in terms of the total value of arrows in one
layer of the square lattice. By using this classification, we succeed to reduce
enormously the dimension of the matrix which has to be diagonalized in the DMRG
method. We apply our method to the 19-vertex model with the interaction
and obtain for the conformal anomaly. PACS. 05.90.+m,
02.70.-cComment: RevTeX style, 20 pages, 12 figure
Yang-Baxter equation for the asymmetric eight-vertex model
In this note we study `a la Baxter [1] the possible integrable manifolds of
the asymmetric eight-vertex model. As expected they occur when the Boltzmann
weights are either symmetric or satisfy the free-fermion condition but our
analysis clarify the reason both manifolds need to share a universal invariant.
We also show that the free-fermion condition implies three distinct classes of
integrable models.Comment: Latex, 12 pages, 1 figur
Finite-dimensional analogs of string s <-> t duality and pentagon equation
We put forward one of the forms of functional pentagon equation (FPE), known
from the theory of integrable models, as an algebraic explanation to the
phenomenon known in physics as st duality. We present two simple geometrical
examples of FPE solutions, one of them yielding in a particular case the
well-known Veneziano expression for 4-particle amplitude. Finally, we interpret
our solutions of FPE in terms of relations in Lie groups.Comment: LaTeX, 12 pages, 6 eps figure
Social dimension of risk behaviours among adolescent prostitutes: Insight from South-Western Nigeria
This study examined the social dimension of risk behaviours among adolescent prostitutes in Lagos metropolis, Nigeria. More specifically, it examined the relationship between educational attainment and use of drug among female adolescent sex workers, investigated the relationship between use of drug and tendency for criminal behaviour among female adolescent sex workers, examined the impact of drug use on the nature of sex of female adolescent sex workers, established the relationship between educational attainment and consistent use of male condom by female adolescent sex workers. Cross-sectional survey and in-depth interview research methods were adopted to generate both quantitative and qualitative data from the respondents. Findings of the study showed that 90.7% of the respondents joined the sex industry because of poverty and lack of other means of getting daily food. 98.6% of the respondents that participated in the research inquiry had knowledge about diseases that can be transmitted through sexual intercourse; while all the respondents had knowledge about the existence of HIV/AIDS, 91.7% of them identified sexual intercourse as a major route of HIV transmission. There was a significant relationship between the use of drug and nature of sex of female sex workers at P < 0.05. Specifically, 99.7% of the respondents used male condoms regularly in every sexual act, 5.5% of the respondents used female condoms at irregular intervals in every sexual act, while 84.8% compromised the use of condoms with financial rewards. Consequently, a high percentage of the population was assumed to be at risk of HIV/AIDS, while 7.2% of the sample had become pregnant while on the job and 3.1% of these pregnancies were terminated through induced abortion. Furthermore, 44.1% of the drug-addicted and low-income sex workers were found to be mostly involved in criminal activities while 60.3% of the sampled populations were victims of different types of violent sexual experience. In conclusion, socio-economic constraints are the primary factors that push adolescent girls into prostitution in Nigeria and these same factors hinder them from practicing safe sex within the sex industry. Thus, it is recommended that the Nigerian government should develop programmes that will reduce poverty level and unemployment trend, in order to reduce adolescent/adult prostitution with its attendant problems of HIV transmission and criminal activities in the country
Exact solution of Calogero model with competing long-range interactions
An integrable extension of the Calogero model is proposed to study the
competing effect of momentum dependent long-range interaction over the original
{1 \ov r^2} interaction. The eigenvalue problem is exactly solved and the
consequences on the generalized exclusion statistics, which appears to differ
from the exchange statistics, are analyzed. Family of dual models with
different coupling constants is shown to exist with same exclusion statistics.Comment: Revtex, 6 pages, 1 figure, hermitian variant of the model included,
final version to appear in Phys. Rev.
Free Expansion of a Weakly-interacting Dipolar Fermi Gas
We theoretically investigate a polarized dipolar Fermi gas in free expansion.
The inter-particle dipolar interaction deforms phase-space distribution in trap
and also in the expansion. We exactly predict the minimal quadrupole
deformation in the expansion for the high-temperature Maxwell-Boltzmann and
zero-temperature Thomas-Fermi gases in the Hartree-Fock and Landau-Vlasov
approaches. In conclusion, we provide a proper approach to develop the
time-of-flight method for the weakly-interacting dipolar Fermi gas and also
reveal a scaling law associated with the Liouville's theorem in the long-time
behaviors of the both gases
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