1,299 research outputs found
Determination of oscillator strength of confined excitons in a semiconductor microcavity
We have achieved a significant experimental Rabi-splitting (3.4 meV) for
confined polaritons in a planar semiconductor microcavity for only a
single quantum well (SQW) of GaAs (10 nm) placed at the antinode. The
Rabi-splitting phenomena are discussed in detail based on the semiclassical
theory, where two coupled harmonic oscillators (excitons and photons) are used
to describe the system. In this way, we can obtain the dispersion curve of
polaritons, the minimum value for the cavity reflectance and the oscillator
strength to reach the strong coupling regime. This approach describes an
ensemble of excitons confined in a SQW and includes a dissipation component.
The results present a weak coupling regime, where an enhanced spontaneous
emission takes place, and a strong coupling regime, where Rabi-splitting in the
dispersion curve can be observed. The theoretical results are confronted with
experimental data for the reflectance behavior in resonant and off-resonant
conditions and present a great accuracy. This allows us to determine the
oscillator strength of the confined excitons in the SQW with great precision.Comment: 11 pages, 7 figure
Diversidade da comunidade bacteriana presente na rizosfera de milho transgênico e na sua respectiva linhagem isogênica não transgênica.
Análise da comunidade bacteriana presente na raiz de milho geneticamente modificado e sua respectiva linhagem isogênica não transgênica.
4-Dimensional BF Theory as a Topological Quantum Field Theory
Starting from a Lie group G whose Lie algebra is equipped with an invariant
nondegenerate symmetric bilinear form, we show that 4-dimensional BF theory
with cosmological term gives rise to a TQFT satisfying a generalization of
Atiyah's axioms to manifolds equipped with principal G-bundle. The case G =
GL(4,R) is especially interesting because every 4-manifold is then naturally
equipped with a principal G-bundle, namely its frame bundle. In this case, the
partition function of a compact oriented 4-manifold is the exponential of its
signature, and the resulting TQFT is isomorphic to that constructed by Crane
and Yetter using a state sum model, or by Broda using a surgery presentation of
4-manifolds.Comment: 15 pages in LaTe
Avaliação do possível impacto de milho geneticamente modificado na ciclagem do nitrogênio em solo de Cerrado.
Fertbio 2012
Link Invariants of Finite Type and Perturbation Theory
The Vassiliev-Gusarov link invariants of finite type are known to be closely
related to perturbation theory for Chern-Simons theory. In order to clarify the
perturbative nature of such link invariants, we introduce an algebra V_infinity
containing elements g_i satisfying the usual braid group relations and elements
a_i satisfying g_i - g_i^{-1} = epsilon a_i, where epsilon is a formal variable
that may be regarded as measuring the failure of g_i^2 to equal 1.
Topologically, the elements a_i signify crossings. We show that a large class
of link invariants of finite type are in one-to-one correspondence with
homogeneous Markov traces on V_infinity. We sketch a possible application of
link invariants of finite type to a manifestly diffeomorphism-invariant
perturbation theory for quantum gravity in the loop representation.Comment: 11 page
Expression of candidates genes for drought tolerance related to ABA signaling in roots of C. Canephora.
Optical phonon modes of wurtzite InP
Optical vibration modes of InP nanowires in the wurtzite phase were investigated by Raman scattering spectroscopy. The wires were grown along the [0001] axis by the vapor-liquid-solid method. The A1(TO), E2h, and E1(TO) phonon modes of the wurtzite symmetry were identified by using light linearly polarized along different directions in backscattering configuration. Additionally, forbidden longitudinal optical modes have also been observed. Furthermore, by applying an extended 11-parameter rigid-ion model, the complete dispersion relations of InP in the wurtzite phase have been calculated, showing a good agreement with the Raman experimental data
Physically meaningful and not so meaningful symmetries in Chern-Simons theory
We explicitly show that the Landau gauge supersymmetry of Chern-Simons theory
does not have any physical significance. In fact, the difference between an
effective action both BRS invariant and Landau supersymmetric and an effective
action only BRS invariant is a finite field redefinition. Having established
this, we use a BRS invariant regulator that defines CS theory as the large mass
limit of topologically massive Yang-Mills theory to discuss the shift k \to
k+\cv of the bare Chern-Simons parameter in conncection with the Landau
supersymmetry. Finally, to convince ourselves that the shift above is not an
accident of our regularization method, we comment on the fact that all BRS
invariant regulators used as yet yield the same value for the shift.Comment: phyzzx, 21 pages, 2 figures in one PS fil
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