1,608 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
How excellent is thy name: cantata (mixed) chorus and orchestra: text: Psalm #8
Thesis (M.A.)--Boston Universit
Aspects of emergent geometry in the AdS/CFT context
We study aspects of emergent geometry for the case of orbifold superconformal
field theories in four dimensions, where the orbifolds are abelian within the
AdS/CFT proposal. In particular, we show that the realization of emergent
geometry starting from the N=4 SYM theory in terms of a gas of particles in the
moduli space of vacua of a single D3 brane in flat space gets generalized to a
gas of particles on the moduli space of the corresponding orbifold conformal
field theory (a gas of D3 branes on the orbifold space). Our main purpose is to
show that this can be analyzed using the same techniques as in the N=4 SYM case
by using the method of images, including the measure effects associated to the
volume of the gauge orbit of the configurations. This measure effect gives an
effective repulsion between the particles that makes them condense into a
non-trivial vacuum configuration, and it is exactly these configurations that
lead to the geometry of X in the AdS x X dual field theoryComment: 24 page
Link Invariants and Combinatorial Quantization of Hamiltonian Chern-Simons Theory
We define and study the properties of observables associated to any link in
(where is a compact surface) using the
combinatorial quantization of hamiltonian Chern-Simons theory. These
observables are traces of holonomies in a non commutative Yang-Mills theory
where the gauge symmetry is ensured by a quantum group. We show that these
observables are link invariants taking values in a non commutative algebra, the
so called Moduli Algebra. When these link invariants are pure
numbers and are equal to Reshetikhin-Turaev link invariants.Comment: 39, latex, 7 figure
ANALYSIS OF INTERFACIAL AND MASS TRANSFER EFFECTS ON FORCED CONVECTION IN GAS-LIQUID ANNULAR TWO-PHASE FLOW
In a gas-liquid annular two-phase flow one of the main factors influencing
the determination of heat transfer rates is the average thickness of the liquid
film. A model to accurately represent the heat transfer in such situations has
to be able of determining the average liquid film thickness to within a
reasonable accuracy. A typical physical aspect in gas-liquid annular flows is
the appearance of interface waves, which affect heat, mass and momentum
transfers. Existing models implicitly consider the wave effects in the
momentum transfer by an empirical correlation for the interfacial friction
factor. However, this procedure does not point out the difference between
interface waves and the natural turbulent effects of the system. In the
present work, the wave and mass transfer effects in the theoretical
estimation of average liquid film thickness are analyzed, in comparison to a
model that does not explicitly include these effects, as applied to the
prediction of heat transfer rates in a thermally developing flow situation
Numerical tests of AdS/CFT at strong coupling
We study various correlation functions (two and three point functions) in a
large matrix model of six commuting matrices with a numerical Monte Carlo
algorithm. This is equivalent to a model of a gas of particles in six
dimensions with a confining quadratic potential and logarithmic repulsions at
finite temperature, where we are measuring the leading order non-gaussianities
in the thermal fluctuations.
This is a simplified model of the low energy dynamics of N=4 SYM at strong
coupling. We find strong evidence that the simplified matrix model matches with
the dual gravitational description of three point functions in the AdS/CFT
correspondence.Comment: 23 pages, 7 figures, revtex. v2: minor correction
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
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