65,576 research outputs found
Fermion Energies in the Background of a Cosmic String
We provide a thorough exposition, including technical and numerical details,
of previously published results on the quantum stabilization of cosmic strings.
Stabilization occurs through the coupling to a heavy fermion doublet in a
reduced version of the standard model. We combine the vacuum polarization
energy of fermion zero-point fluctuations and the binding energy of occupied
energy levels, which are of the same order in a semi-classical expansion.
Populating these bound states assigns a charge to the string. We show that
strings carrying fermion charge become stable if the electro-weak bosons are
coupled to a fermion that is less than twice as heavy as the top quark. The
vacuum remains stable in our model, because neutral strings are not
energetically favored. These findings suggests that extraordinarily large
fermion masses or unrealistic couplings are not required to bind a cosmic
string in the standard model.Comment: 38 pages, 6 figures, version accepted for publication in Phys Rev
Harmonic oscillator in a background magnetic field in noncommutative quantum phase-space
We solve explicitly the two-dimensional harmonic oscillator and the harmonic
oscillator in a background magnetic field in noncommutative phase-space without
making use of any type of representation. A key observation that we make is
that for a specific choice of the noncommutative parameters, the time reversal
symmetry of the systems get restored since the energy spectrum becomes
degenerate. This is in contrast to the noncommutative configuration space where
the time reversal symmetry of the harmonic oscillator is always broken.Comment: 7 pages Late
Bound state energies and phase shifts of a non-commutative well
Non-commutative quantum mechanics can be viewed as a quantum system
represented in the space of Hilbert-Schmidt operators acting on non-commutative
configuration space. Within this framework an unambiguous definition can be
given for the non-commutative well. Using this approach we compute the bound
state energies, phase shifts and scattering cross sections of the non-
commutative well. As expected the results are very close to the commutative
results when the well is large or the non-commutative parameter is small.
However, the convergence is not uniform and phase shifts at certain energies
exhibit a much stronger then expected dependence on the non-commutative
parameter even at small values.Comment: 12 pages, 8 figure
Harm: The counterfactual comparative account, the omission and pre-emption problems, and well-being
The concept of “harm” is ubiquitous in moral theorising, and yet remains poorly defined. Bradley suggests that the counterfactual comparative account of harm is the most plausible account currently available, but also argues that it is fatally flawed, since it falters on the omission and pre-emption problems. Hanna attempts to defend the counterfactual comparative account of harm against both problems. In this paper, I argue that Hanna’s defence fails. I also show how his defence highlights the fact that both the omission and the pre-emption problems have the same root cause – the inability of the counterfactual comparative account of harm to allow for our implicit considerations regarding well-being when assessing harm. While its purported neutrality with regard to substantive theories of well-being is one of the reasons that this account is considered to be the most plausible on offer, I will argue that this neutrality is illusory
Second T = 3/2 state in B and the isobaric multiplet mass equation
Recent high-precision mass measurements and shell model calculations~[Phys.
Rev. Lett. {\bf 108}, 212501 (2012)] have challenged a longstanding explanation
for the requirement of a cubic isobaric multiplet mass equation for the lowest
isospin quartet. The conclusions relied upon the choice of the
excitation energy for the second state in B, which had two
conflicting measurements prior to this work. We remeasured the energy of the
state using the reaction and significantly disagree
with the most recent measurement. Our result supports the contention that
continuum coupling in the most proton-rich member of the quartet is not the
predominant reason for the large cubic term required for nuclei
Impact of a 'diagonal' intervention on uptake of sexual and reproductive health services by female sex workers in Mozambique : a mixed-methods implementation study
CITATION: Lafort, Y. 2018. Impact of a diagonal intervention on uptake of sexual and reproductive health services by female sex workers in Mozambique : a mixed-methods implementation study. Frontiers in Public Health, 6:109, doi:10.3389/fpubh.2018.00109.The original publication is available at https://www.frontiersin.orgBackground: Female sex workers (FSWs) have high risks for adverse sexual and reproductive health (SRH) outcomes, yet low access to services. Within an implementation research project enhancing uptake of SRH services by FSWs, we piloted a “diagonal” intervention, which combined strengthening of FSW-targeted services (vertical) with making public health facilities more FSW-friendly (horizontal), and tested its effect.
Methods: The study applied a convergent parallel mixed-methods design to assess changes in access to SRH services. Results of structured interviews with FSWs pre-intervention (N = 311) and thereafter (N = 404) were compared with the findings of eight post-intervention focus group discussions (FGDs) with FSWs and two with FSW-peer educators (PEs).
Results: Marked and statistically significant rises occurred in consistent condom use with all partners (55.3–67.7%), ever use of female condoms (37.9–54.5%), being tested for HIV in the past 6 months (56.0–76.6%), using contraception (84.5–95.4%), ever screened for cervical cancer (0.0–16.9%) and having ≥10 contacts with a PE in the past year (0.5–24.45%). Increases mostly resulted from FSW-targeted outreach, with no rise detected in utilization of public health facilities. FGD participants reported that some facilities had become more FSW-friendly, but barriers such as stock-outs, being asked for bribes and disrespectful treatment persisted.
Conclusion: The combination of expanding FSW-targeted SRH services with improving access to the public health services resulted in an overall increased uptake of services, but almost exclusively because of the strengthened targeted (vertical) outreach services. Utilization of public SRH services had not yet increased and many barriers to access remained. Our diagonal approach was thus only successful in its vertical component. Improving access to the general health services remains nevertheless important and further research is needed how to reduce barriers. Ideally, the combination approach should be maintained and more successful approaches to increase utilization of public services should be explored.https://www.frontiersin.org/articles/10.3389/fpubh.2018.00109/fullPublisher's versio
Fully self-consistent relativistic Brueckner-Hartree-Fock theory for finite nuclei
Starting from the relativistic form of the Bonn potential as a bare
nucleon-nucleon interaction, the full Relativistic Brueckner-Hartree-Fock
(RBHF) equations are solved for finite nuclei in a fully self-consistent basis.
This provides a relativistic ab initio calculation of the ground state
properties of finite nuclei without any free parameters and without three-body
forces. The convergence properties for the solutions of these coupled equations
are discussed in detail at the example of the nucleus O. The binding
energies, radii, and spin-orbit splittings of the doubly magic nuclei He,
O, and Ca are calculated and compared with the earlier RBHF
calculated results in a fixed Dirac Woods-Saxon basis and other
non-relativistic ab initio calculated results based on pure two-body forces.Comment: 22 pages, 13 figure
Polarization transfer observables for quasielastic proton-nucleus scattering in terms of a complete Lorentz invariant representation of the NN scattering matrix
For the calculation of polarization transfer observables for quasielastic
scattering of protons on nuclei, a formalism in the context of the Relativistic
Plane Wave Impulse Approximation is developed, in which the interaction matrix
is expanded in terms of a complete set of 44 independent invariant amplitudes.
A boson-exchange model is used to predict the 39 amplitudes which were omitted
in the formerly used five-term parameterization(the SPVAT form) of the
nucleon-nucleon scattering matrix. Use of the complete set of amplitudes
eliminates the arbitrariness of the five-term representation.Comment: 29 pages, 2 figure
Non(anti) commutativity for open superstrings
Non(anti)commutativity in an open free superstring and also one moving in a
background anti-symmetric tensor field is investigated. In both cases, the
non(anti)commutativity is shown to be a direct consequence of the non-trivial
boundary conditions which, contrary to several approaches, are not treated as
constraints. The above non(anti)commutative structures lead to new results in
the algebra of super constraints which still remain involutive, indicating the
internal consistency of our analysis.Comment: 10 pages Latex, To appear in Physics Letters
Tensor coupling effects on spin symmetry in anti-Lambda spectrum of hypernuclei
The effects of -tensor coupling on the spin
symmetry of spectra in -nucleus systems have
been studied with the relativistic mean-field theory. Taking
C+ as an example, it is found that the tensor coupling
enlarges the spin-orbit splittings of by an order of magnitude
although its effects on the wave functions of are negligible.
Similar conclusions has been observed in -nucleus of different
mass regions, including O+, Ca+ and
Pb+. It indicates that the spin symmetry in
anti-lambda-nucleus systems is still good irrespective of the tensor coupling.Comment: 12 pages, 3 figures
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