8,504 research outputs found
Semiconductor cavity QED: Bandgap induced by vacuum fluctuations
We consider theoretically a semiconductor nanostructure embedded in
one-dimensional microcavity and study the modification of its electron energy
spectrum by the vacuum fluctuations of the electromagnetic field. To solve the
problem, a non-perturbative diagrammatic approach based on the Green's function
formalism is developed. It is shown that the interaction of the system with the
vacuum fluctuations of the optical cavity opens gaps within the valence band of
the semiconductor. The approach is verified for the case of large photon
occupation numbers, proving the validity of the model by comparing to previous
studies of the semiconductor system excited by a classical electromagnetic
field. The developed theory is of general character and allows for unification
of quantum and classical descriptions of the strong light-matter interaction in
semiconductor structures
Some Cosmological Implications of Hidden Sectors
We discuss some cosmological implications of extensions of the Standard Model
with hidden sector scalars coupled to the Higgs boson. We put special emphasis
on the conformal case, in which the electroweak symmetry is broken radiatively
with a Higgs mass above the experimental limit. Our refined analysis of the
electroweak phase transition in this kind of models strengthens the prediction
of a strongly first-order phase transition as required by electroweak
baryogenesis. We further study gravitational wave production and the
possibility of low-scale inflation as well as a viable dark matter candidate.Comment: 23 pages, 8 figures; some comments added, published versio
BCS pairing in fully repulsive fermion mixtures
We consider a mixture of two neutral cold Fermi gases with repulsive
interactions. We show that in some region of the parameter space of the system
the effective attraction between fermions of the same type can appear due to
the exchange of collective excitations. This leads to the formation of BCS
pairing in the case where bare inter-atomic interactions are repulsive
Factorization of finite temperature graphs in thermal QED
We extend our previous analysis of gauge and Dirac fields in the presence of
a chemical potential. We consider an alternate thermal operator which relates
in a simple way the Feynman graphs in QED at finite temperature and charge
density to those at zero temperature but non-zero chemical potential. Several
interesting features of such a factorization are discussed in the context of
the thermal photon and fermion self-energies.Comment: 4 page
Teaching Chemistry in a Spiral Progression Approach: Lessons from Science Teachers in the Philippines
As the Philippines moves towards implementing the K-12 curriculum, there has been a mismatch in teacher preparation in science. The present teacher education curriculum prepares science teachers to specialise in a specific field (e.g. integrated science, biology, chemistry, and physics). However, in the K-12 curriculum, they are required to teach all the sciences in a spiral progression approach. Hence, this study analysed the experiences of science teachers in teaching chemistry in the K-12 curriculum in order to identify their challenges and how they are overcoming them. Findings suggest that the teacher’s content, pedagogy, and assessment in chemistry are problematic; specifically, challenges such as instruction-related factors, teacher competence, in-service training sufficiency, job satisfaction, support from upper management, laboratory adequacy, school resources, assessment tools, and others influence teacher success in teaching chemistry. These identified challenges greatly affect the ultimate beneficiaries of education, which is the learner
Thermal Operator and Cutting Rules at Finite Temperature and Chemical Potential
In the context of scalar field theories, both real and complex, we derive the
cutting description at finite temperature (with zero/finite chemical potential)
from the cutting rules at zero temperature through the action of a simple
thermal operator. We give an alternative algebraic proof of the largest time
equation which brings out the underlying physics of such a relation. As an
application of the cutting description, we calculate the imaginary part of the
one loop retarded self-energy at zero/finite temperature and finite chemical
potential and show how this description can be used to calculate the dispersion
relation as well as the full physical self-energy of thermal particles.Comment: 17 pages, 13 figures. Added references, version to appear in Physical
Review
The CP properties of the lightest Higgs boson with sbottom effects
In the framework of the recently proposed gluino-axion model, using the
effective potential method and taking into account the top-stop as well as the
bottom-sbottom effects, we discuss the CP--properties of the lightest Higgs
boson, in particular its CP--odd composition, which can offer new opportunities
at collider searches. It is found that although the CP-odd composition of the
lightest Higgs increases slightly with the inclusion of the sbottom effects, it
never exceeds %0.17 for all values of the renormalization scale Q ranging from
top mass to TeV scaleComment: 24 pp, 12 eps fig
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