12,887 research outputs found
New Matter Effects and BBN Constraints for Mass Varying Neutrinos
The presence of light (m_a ~ 10^-6 ev) scalar fields in the early universe
can modify the cosmology of neutrinos considerably by allowing their masses to
vary on cosmological times. In this paper, we consider the effect of
Planck-suppressed couplings of this scalar to electrons and show that such
couplings can easily make new sterile states thermally inaccessible in the
early universe, preserving the successes of big bang nucleosynthesis
predictions. We consider the circumstances under which these effects give the
proper initial conditions for recently considered models of neutrino dark
energy, and consider limits from tests of the equivalence principle. The
parameters which satisfy cosmological constraints naturally give rise to
interesting signals in terrestrial neutrino oscillation experiments.Comment: 6 pages. References added, minor modification
Visible Cascade Higgs Decays to Four Photons at Hadron Colliders
The presence of a new singlet scalar particle a can open up new decay
channels for the Higgs boson, through cascades of the form h -> 2a -> X,
possibly making discovery through standard model channels impossible. If a is
CP-odd, its decay products are particularly sensitive to physics beyond the
standard model. Quantum effects from heavy fields can naturally make gluonic
decay, a -> 2g, the dominant decay mode, resulting in a h -> 4 g decay which is
difficult to observe at hadron colliders, and is allowed by LEP for m_h > 82
GeV. However, there are usually associated decays with photons, either h -> 2g
2gamma or h -> 4gamma, which are more promising. The decay h -> 2g 2gamma only
allows discovery of the a particle and not the Higgs whereas h -> 4gamma is a
clean channel that can discover both particles. We determine what branching
ratios are required for discovery at LHC and find that with 300 fb^-1 of
luminosity, a branching ratio of order 10^-4 is sufficient for a large region
of Higgs masses. Due to a lower expected luminosity of ~ 8 fb^-1, discovery at
the Tevatron requires more than 5 x 10^-3 in branching ratio.Comment: 6 pages, 2 color figures, revtex4 forma
You’re trouble you are, just like your mother! An intergenerational autobiographical narrative on activism in Higher Education
This paper draws on autobiographical interviews of a mother and daughter concerning their experiences of working in higher education to explore the changes in university teaching and research in the UK and also the possibilities of challenging prevalent normative assumptions about aims and purpose. It uses the qualitative methodology of narrative enquiry, particularly in its focus on temporality, sociality and place, to create a co-constructed account which is able to expose critical events, possibilities and limitations for higher education ‘activists’ in the recent past and present. It will be shown that the quality of the relationship between the two researcher-participants had a significant impact on the quality of the data generated, and that together the relationship and methodology promoted interpretation and analysis in ‘uncommonly accelerated ways’ (Carillo & Baguley, 2011). At the same time, it created moments of discomfort and misunderstandings about ideological perceptions. It was found that while there were some similarities at least initially between the experiences of the two interviewees in their capacities both to perform to work expectations and to take an activist position, substantial differences were identified due, in particular, to generational intellectual schisms as well as shifts in higher education from elitist institutions promoting public good to mass, neo-liberal institutions with performative and institutional goals and practices. The European dream of becoming ‘the most competitive and knowledge-based economy of the world’ (European Council, 2000) has marked the transformation and modernisation of social welfare and education systems…. When policies and institutional practices based on competence, efficiency and competition are stressed, ideals such as equity and social community tend to become secondary (Arnesan, 2011
On the mechanism of action of the cytostatic drug anguidine and of the immunosuppressive agent ovalicin, two sesquiterpenes from fungi
Transient behavior of surface plasmon polaritons scattered at a subwavelength groove
We present a numerical study and analytical model of the optical near-field
diffracted in the vicinity of subwavelength grooves milled in silver surfaces.
The Green's tensor approach permits computation of the phase and amplitude
dependence of the diffracted wave as a function of the groove geometry. It is
shown that the field diffracted along the interface by the groove is equivalent
to replacing the groove by an oscillating dipolar line source. An analytic
expression is derived from the Green's function formalism, that reproduces well
the asymptotic surface plasmon polariton (SPP) wave as well as the transient
surface wave in the near-zone close to the groove. The agreement between this
model and the full simulation is very good, showing that the transient
"near-zone" regime does not depend on the precise shape of the groove. Finally,
it is shown that a composite diffractive evanescent wave model that includes
the asymptotic SPP can describe the wavelength evolution in this transient
near-zone. Such a semi-analytical model may be useful for the design and
optimization of more elaborate photonic circuits whose behavior in large part
will be controlled by surface waves.Comment: 12 pages, 10 figure
The Bose-Einstein correlation function from a Quantum Field Theory point of view
We show that a recently proposed derivation of Bose-Einstein correlations
(BEC) by means of a specific version of thermal Quantum Field Theory (QFT),
supplemented by operator-field evolution of the Langevin type, allows for a
deeper understanding of the possible coherent behaviour of the emitting source
and a clear identification of the origin of the observed shape of the BEC
function . Previous conjectures in this matter obtained by other
approaches are confirmed and have received complementary explanation.Comment: Some misprints corrected. To be publishe in Phys. Rev.
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