15,026 research outputs found
Single photon absorption and dynamic control of a coupled quantum dot-cavity system
We theoretically investigate the dynamic interaction of a quantum dot in a
nanocavity with timesymmetric single photon pulses. The simulations, based on a
wavefunction approach, reveal that almost perfect single photon absorption
occurs for quantum dot-cavity systems operating on the edge between strong and
weak coupling regime. The computed maximum absorptions probability is close to
unity for pulses with a typical length comparable to the half of the Rabi
period. Furthermore, the dynamic control of the quantum dot energy via electric
fields allows the freezing of the light-matter interaction leaving the quantum
dot in its excited state. Shaping of single photon wavepackets by the electric
field control is limited by the occurrence of chirping of the single photon
pulse. This understanding of the interaction of single photon pulses with the
quantum dot-cavity system provides the basis for the development of advanced
protocols for quantum information processing in the solid state.Comment: 7 pages, 4 figure
The Geometry of the Quantum Euclidean Space
A detailed study is made of the noncommutative geometry of , the
quantum space covariant under the quantum group . For each of its two
-covariant differential calculi we find its metric, the corresponding
frame and two torsion-free covariant derivatives that are metric compatible up
to a conformal factor and which yield both a vanishing linear curvature. A
discussion is given of various ways of imposing reality conditions. The
delicate issue of the commutative limit is discussed at the formal algebraic
level. Two rather different ways of taking the limit are suggested, yielding
respectively and as the limit Riemannian manifold.Comment: 29 pages, latex fil
On the Decoupling of the Homogeneous and Inhomogeneous Parts in Inhomogeneous Quantum Groups
We show that, if there exists a realization of a Hopf algebra in a
-module algebra , then one can split their cross-product into the tensor
product algebra of itself with a subalgebra isomorphic to and commuting
with . This result applies in particular to the algebra underlying
inhomogeneous quantum groups like the Euclidean ones, which are obtained as
cross-products of the quantum Euclidean spaces with the quantum groups
of rotation of , for which it has no classical analog.Comment: Latex file, 27 pages. Final version to appear in J. Phys.
Iron line emission in X-ray afterglows
Recent observations of X-ray afterglows reveal the presence of a redshifted
Kalpha iron line in emission in four bursts. In GRB 991216, the line was
detected by the low energy grating of Chandra, which showed the line to be
broad, with a full width of ~15,000 km/s. These observations indicate the
presence of a >1 solar mass of iron rich material in the close vicinity of the
burst, most likely a supernova remnant. The fact that such strong lines are
observed less than a day after the trigger strongly limits the size of the
remnant, which must be very compact. If the remnant had the observed velocity
since the supernova explosion, its age would be less than a month. In this case
nickel and cobalt have not yet decayed into iron. We show how to solve this
paradox.Comment: 3 pages, to appear in the proceedings of the the 2nd Workshop on
Gamma-Ray Bursts in the Afterglow Era, Rome, Oct. 200
q-Deformed quaternions and su(2) instantons
We have recently introduced the notion of a q-quaternion bialgebra and shown
its strict link with the SO_q(4)-covariant quantum Euclidean space R_q^4.
Adopting the available differential geometric tools on the latter and the
quaternion language we have formulated and found solutions of the
(anti)selfduality equation [instantons and multi-instantons] of a would-be
deformed su(2) Yang-Mills theory on this quantum space. The solutions depend on
some noncommuting parameters, indicating that the moduli space of a complete
theory should be a noncommutative manifold. We summarize these results and add
an explicit comparison between the two SO_q(4)-covariant differential calculi
on R_q^4 and the two 4-dimensional bicovariant differential calculi on the bi-
(resp. Hopf) algebras M_q(2),GL_q(2),SU_q(2), showing that they essentially
coincide.Comment: Latex file, 18 page
Research Note: Gunboat Diplomacy in the South Atlantic: The United States and the Falkland Island Crises, 1824-1832
Germanic government, religion, and family life in Beowulf
Thesis (M.A.)--Boston University, 1946. This item was digitized by the Internet Archive
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