Bose-Einstein condensation of finite number of confined particles

The partition function and specific heat of a system consisting of a finite number of bosons confined in an external potential are calculated in canonical ensemble. Using the grand partition function as the generating function of the partition function, an iterative scheme is established for the calculation of the partition function of system with an arbitrary number of particles. The scheme is applied to finite number of bosons confined in isotropic and anisotropic parabolic traps and in rigid boxes. The specific heat as a function of temperature is studied in detail for different number of particles, different degrees of anisotropy, and different spatial dimensions. The cusp in the specific heat is taken as an indication of Bose-Einstein condensation (BEC).It is found that the results corresponding to a large number of particles are approached quite rapidly as the number of bosons in the system increases. For large number of particles, results obtained within our iterative scheme are consistent with those of the semiclassical theory of BEC in an external potential based on the grand canonical treatment.Comment: 20 pages in RevTex with 4 Postscript figures. The e-mail addresses of the authors are `[email protected]',and `[email protected]

The Specific Heat of a Trapped Fermi Gas: an Analytical Approach

We find an analytical expression for the specific heat of a Fermi gas in a harmonic trap using a semi-classical approximation. Our approximation is valid for kT>hw and in this range it is shown to be highly accurate. We comment on the semi-classical approximation, presenting an explanation for this high accuracy.Comment: To be published in Physics Letters A. 7 pages (RevTex) and 2 figures (postscript

Density and Pair Correlation Function of Confined Identical Particles: the Bose-Einstein Case

Two basic correlation functions are calculated for a model of $N$ harmonically interacting identical particles in a parabolic potential well. The density and the pair correlation function of the model are investigated for the boson case. The dependence of these static response properties on the complete range of the temperature and of the number of particles is obtained. The calculation technique is based on the path integral approach of symmetrized density matrices for identical particles in a parabolic confining well.Comment: 8 pages (REVTEX) + 6 figures (postscript

Correlations in a Confined gas of Harmonically Interacting Spin-Polarized Fermions

For a fermion gas with equally spaced energy levels, the density and the pair correlation function are obtained. The derivation is based on the path integral approach for identical particles and the inversion of the generating functions for both static responses. The density and the pair correlation function are evaluated explicitly in the ground state of a confined fermion system with a number of particles ranging from 1 to 220 and filling the Fermi level completely.Comment: 11 REVTEX pages, 3 postscript figures. Accepted for publication in Phys. Rev. E, Vol. 58 (August 1, 1998

Confined Harmonically Interacting Spin-Polarized Fermions in a Magnetic Field: Thermodynamics

We investigate the combined influence of a magnetic field and a harmonic interparticle interaction on the thermodynamic properties of a finite number of spin polarized fermions in a confiment potential. This study is an extension using our path integral approach of symmetrized density matrices for identical particles. The thermodynamical properties are calculated for a three dimensional model of N harmonically interacting spin polarized fermions in a parabolic potential well in the presence of a magnetic field. The free energy and the internal energy are obtained for a limited number of particles. Deviations from the thermodynamical limit become negligible for about 100 or more particles, but even for a smaller number of fermions present in the well, scaling relations similar to those of the continuum approximation to the density of states are already satisfied.Comment: 7 pages REVTEX and 8 postscript figures, accepted in Phys. Rev.

Screening for Gynecologic Conditions With Pelvic Examination US Preventive Services Task Force Recommendation Statement

IMPORTANCE Many conditions that can affect women\u27s health are often evaluated through pelvic examination. Although the pelvic examination is a common part of the physical examination, it is unclear whether performing screening pelvic examinations in asymptomatic women has a significant effect on disease morbidity and mortality. OBJECTIVE To issue a new US Preventive Services Task Force(USPSTF) recommendation on screening for gynecologic conditions with pelvic examination for conditions other than cervical cancer, gonorrhea, and chlamydia, for which the USPSTF has already made specific recommendations. EVIDENCE REVIEW The USPSTF reviewed the evidence on the accuracy, benefits, and potential harms of performing screening pelvic examinations in asymptomatic, nonpregnant adult women 18 years and older who are not at increased risk for any specific gynecologic condition. FINDINGS Overall, the USPSTF found inadequate evidence on screening pelvic examinations for the early detection and treatment of a range of gynecologic conditions in asymptomatic, nonpregnant adult women. CONCLUSIONS AND RECOMMENDATION The USPSTF concludes that the current evidence is insufficient to assess the balance of benefits and harms of performing screening pelvic examinations in asymptomatic, nonpregnant adult women. (I statement) This statement does not apply to specific disorders for which the USPSTF already recommends screening (ie, screening for cervical cancer with a Papanicolaou smear, screening for gonorrhea and chlamydia)

Z-induced FCNCs and their effects on Neutrino Oscillations

Adding singlet neutrinos to the standard model spectrum in general gives rise to Z-induced flavor-changing neutral currents. We study the impact of these currents on matter-induced neutrino oscillations in the sun and in supernovae. While the effects for solar neutrinos are negligible, dramatic effects are possible for supernova neutrinos.Comment: 23 pages (including 5 eps-figures), Latex; references [29-34] were added to the revised versio

The Solar Neutrino Problem in the Presence of Flavor Changing Neutrino Interactions

We study the effects of flavor changing neutrino interactions on the resonant conversion of solar neutrinos. In particular, we describe how the regions in the $Delta m^2 - sin^2 2theta$ plane that are consistent with the four solar neutrino experiments are modified for different strengths of New Physics neutrino interactions.Comment: 24 pages, 14 eps-figures, Latex. References to work by Fogli and Lisi, where implications of results from Gallium experiments are first discussed, and to work by Petcov, where eq. (9) is derived, were added. For a second version of the paper containing more figures in better resolution, see http://www.weizmann.ac.il/~ftsve

Phenomenology of Maximal and Near-Maximal Lepton Mixing

We study the phenomenological consequences of maximal and near-maximal mixing of the electron neutrino with other ($x$=tau and/or muon) neutrinos. We describe the deviations from maximal mixing in terms of a parameter $\epsilon\equiv1-2\sin^2\theta_{ex}$ and quantify the present experimental status for $|\epsilon|<0.3$. We find that the global analysis of solar neutrino data allows maximal mixing with confidence level better than 99% for $10^{-8}$ eV^2\lsim\Delta m^2\lsim2\times10^{-7} eV$^2$. In the mass ranges \Delta m^2\gsim 1.5\times10^{-5} eV$^2$ and $4\times10^{-10}$ eV^2\lsim\Delta m^2\lsim2\times10^{-7} eV$^2$ the full interval $|\epsilon|<0.3$ is allowed within 4$\sigma$(99.995 % CL). We suggest ways to measure $\epsilon$ in future experiments. The observable that is most sensitive to $\epsilon$ is the rate [NC]/[CC] in combination with the Day-Night asymmetry in the SNO detector. With theoretical and statistical uncertainties, the expected accuracy after 5 years is $\Delta \epsilon\sim 0.07$. We also discuss the effects of maximal and near-maximal $\nu_e$-mixing in atmospheric neutrinos, supernova neutrinos, and neutrinoless double beta decay.Comment: 49 pages Latex file using RevTeX. 16 postscript figures included. ( Fig.2 and Fig.4 bitmapped for compression,better resolution at http://ific.uv.es/~pppac/). Improved presentation: some statements included and labels added in figures. Some misprint corrected. Final version to appear in Phys. Rev D. Report no: IFIC/00-40, IASSNS-HEP-00-5

Screening for Impaired Visual Acuity in Older Adults: US Preventive Services Task Force Recommendation Statement

DESCRIPTION: Update of the US Preventive Services Task Force (USPSTF) recommendation on screening for impaired visual acuity in older adults. METHODS: The USPSTF reviewed the evidence on screening for visual acuity impairment associated with uncorrected refractive error, cataracts, and age-related macular degeneration among adults 65 years or older in the primary care setting; the benefits and harms of screening; the accuracy of screening; and the benefits and harms of treatment of early vision impairment due to uncorrected refractive error, cataracts, and age-related macular degeneration. POPULATION: This recommendation applies to asymptomatic adults 65 years or older who do not present to their primary care clinician with vision problems. RECOMMENDATION: The USPSTF concludes that the current evidence is insufficient to assess the balance of benefits and harms of screening for impaired visual acuity in older adults. (I statement)