12,714 research outputs found
Effects of Bose-Einstein Condensation on forces among bodies sitting in a boson heat bath
We explore the consequences of Bose-Einstein condensation on
two-scalar-exchange mediated forces among bodies that sit in a boson gas. We
find that below the condensation temperature the range of the forces becomes
infinite while it is finite at temperatures above condensation.Comment: 10 pages, 2 figure
Constraints on the three-fluid model of curvaton decay
A three fluid system describing the decay of the curvaton is studied by
numerical and analytical means. We place constraints on the allowed interaction
strengths between the fluids and initial curvaton density by requiring that the
curvaton decays before nucleosynthesis while nucleosynthesis, radiation-matter
equality and decoupling occur at correct temperatures. We find that with a
continuous, time-independent interaction, a small initial curvaton density is
naturally preferred along with a low reheating temperature. Allowing for a
time-dependent interaction, this constraint can be relaxed. In both cases, a
purely adiabatic final state can be generated, but not without fine-tuning.
Unlike in the two fluid system, the time-dependent interactions are found to
have a small effect on the curvature perturbation itself due to the different
nature of the system. The presence of non-gaussianity in the model is
discussed.Comment: 9 pages, 10 figure
NMR linewidth and Skyrmion localization in quantum Hall ferromagnets
The non-monotonic behavior of the NMR signal linewidth in the 2D quantum Hall
system is explained in terms of the interplay between skyrmions localization,
due to the influence of disorder, and the non-trivial temperature dependent
skyrmion dynamics.Comment: 5 pages, 2 figure
Zero modes on cosmic strings in an external magnetic field
A classical analysis suggests that an external magnetic field can cause
trajectories of charge carriers on a superconducting domain wall or cosmic
string to bend, thus expelling charge carriers with energy above the mass
threshold into the bulk. We study this process by solving the Dirac equation
for a fermion of mass and charge , in the background of a domain wall
and a magnetic field of strength . We find that the modes of the charge
carriers get shifted into the bulk, in agreement with classical expectations.
However the dispersion relation for the zero modes changes dramatically --
instead of the usual linear dispersion relation, , the new
dispersion relation is well fit by where
for a thin wall in the weak field limit, and for a thick
wall of width . This result shows that the energy of the charge carriers on
the domain wall remains below the threshold for expulsion even in the presence
of an external magnetic field. If charge carriers are expelled due to an
additional perturbation, they are most likely to be ejected at the threshold
energy .Comment: 9 pages, 4 figure
First observation of strong OZI rule violation in interactions
The data of the CERN WA56 experiment that triggered the fast proton produced in the and interactions at beam momenta 20 GeV/c and 12 GeV/c, respectively, are used to analyse the final states . A large excess (up to two orders of magnitude) of the cross sections ratio over the OZI prediction is observed
Transforming aquatic agricultural systems towards gender equality: a five country review
Aquatic agricultural systems (AAS) are systems in which the annual production dynamics of freshwater and/or coastal ecosystems contribute significantly to total household income. Improving the livelihood security and wellbeing of the estimated 250 million poor people dependent on AAS in Bangladesh, Cambodia, the Philippines, the Solomon Islands and Zambia is the goal of the Worldfish Center-led Consortium Research Program (CRP), “Harnessing the development potential of aquatic agricultural systems for development.” One component expected to contribute to sustainably achieving this goal is enhancing the gender and wider social equity of the social, economic and political systems within which the AAS function. The CRP’s focus on social equity, and particularly gender equity, responds to the limited progress to date in enhancing the inclusiveness of development outcomes through interventions that offer improved availability of resources and technologies without addressing the wider social constraints that marginalized populations face in making use of them. The CRP aims to both offer improved availability and address the wider social constraints in order to determine whether a multi-level approach that engages with individuals, households and communities, as well as the wider social, economic and political contexts in which they function, is more successful in extending development’s benefits to women and other excluded groups. Designing the research in development initiatives to test this hypothesis requires a solid understanding of each CRP country’s social, cultural and economic contexts and of the variations across them. This paper provides an initial input into developing this knowledge, based on a review of literature on agriculture, aquaculture and gender relations within the five focal countries. Before delving into the findings of the literature review, the paper first justifies the expectation that successfully achieving lasting wellbeing improvements for poor women and men dependent on AAS rests in part on advances in gender equity, and in light of this justification, presents the AAS CRP’s conceptual frame
One-dimensional Gapless Magnons In A Single Anisotropic Ferromagnetic Nanolayer.
Gapless magnons in a plane ferromagnet with normal axis anisotropy are shown to exist besides the usual gapped modes that affect spin dependent transport properties only above a finite temperature. These magnons are one-dimensional objects, in the sense that they are localized inside the domain walls that form in the film. They may play an essential role in the spin dependent scattering processes even down to very low temperatures.9122680
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