5,466 research outputs found
Spacetime Encodings II - Pictures of Integrability
I visually explore the features of geodesic orbits in arbitrary stationary
axisymmetric vacuum (SAV) spacetimes that are constructed from a complex Ernst
potential. Some of the geometric features of integrable and chaotic orbits are
highlighted. The geodesic problem for these SAV spacetimes is rewritten as a
two degree of freedom problem and the connection between current ideas in
dynamical systems and the study of two manifolds sought. The relationship
between the Hamilton-Jacobi equations, canonical transformations, constants of
motion and Killing tensors are commented on. Wherever possible I illustrate the
concepts by means of examples from general relativity. This investigation is
designed to build the readers' intuition about how integrability arises, and to
summarize some of the known facts about two degree of freedom systems. Evidence
is given, in the form of orbit-crossing structure, that geodesics in SAV
spacetimes might admit, a fourth constant of motion that is quartic in momentum
(by contrast with Kerr spacetime, where Carter's fourth constant is quadratic).Comment: 11 pages, 10 figure
Cyclic and constant temperature aging effects on magnetic materials for inverters and converters
Cyclic and constant temperature aging effects on magnetic materials for inverters and converter
The BLG Theory in Light-Cone Superspace
The light-cone superspace version of the d=3, N=8 superconformal theory of
Bagger, Lambert and Gustavsson (BLG) is obtained as a solution to constraints
imposed by OSp(2,2|8) superalgebra. The Hamiltonian of the theory is shown to
be a quadratic form of the dynamical supersymmetry transformation.Comment: 45 pages, v2: reference added, minor typos corrected, published
versio
Maximally Supersymmetric Yang-Mills in five dimensions in light-cone superspace
We formulate maximally supersymmetric Yang-Mills theory in five dimensions in
light-cone superspace. The light-cone Hamiltonian is of the quadratic form and
the theory can be understood as an oxidation of the N=4 Super Yang-Mills Theory
in four dimensions. We specifically study three-point counterterms and show how
these counterterms vanish on-shell. This study is a preliminary to set up the
technique in order to study possible four-point counterterms.Comment: 25 pages, typos corrected, references adde
Poisson-Lie T-duality and N=2 superconformal WZNW models on compact groups
The supersymmetric generalization of Pisson-Lie T-duality in N=2
superconformal WZNW models on the compact groups is considered. It is shown
that the role of Drinfeld's doubles play the complexifications of the
corresponding compact groups. These complex doubles are used to define the
natural actions of the isotropic subgroups forming the doubles on the group
manifolds of the N=2 superconformal WZNW models. The Poisson- Lie T-duality in
N=2 superconformal U(2)-WZNW model considered in details. It is shown that this
model admits Poisson-Lie symmetries with respect to the isotropic subgroups
forming Drinfeld's double Gl(2,C). Poisson-Lie T-duality transformation maps
this model into itself but acts nontrivialy on the space of classical
solutions. Supersymmetric generalization of Poisson-Lie T-duality in N=2
superconformal WZNW models on the compact groups of higher dimensions is
proposed.Comment: 12 pages, latex, misprints correcte
Comments on ‘‘The non-wavelike response of a continental shelf to wind’’ by G. T. Csanady
Csanady (1998) presents solutions for time-dependent wind-driven flow in a barotropic coastal ocean. We disagree with two of his three boundary condition options and wish to clarify the origin of the non-wavelike aspect of the flow
Construction and analysis of a simplified many-body neutrino model
In dense neutrino systems, such as found in the early Universe, or near a
supernova core, neutrino flavor evolution is affected by coherent
neutrino-neutrino scattering. It has been recently suggested that many-particle
quantum entanglement effects may play an essential role in these systems,
potentially invalidating the traditional description in terms of a set of
single-particle evolution equations. We model the neutrino system by a system
of interacting spins, following an earlier work which showed that such a spin
system can in some cases be solved exactly. We extend this work by constructing
an exact analytical solution to a more general spin system, including initial
states with asymmetric spin distribution and, moreover, not necessarily aligned
along the same axis. Our solution exhibits a rich set of behaviors, including
coherent oscillations and dephasing and a transition from the classical to
quantum regimes. We argue that the classical evolution of the spin system
captures the entire coherent behavior of the neutrino system, while the quantum
effects in the spin system capture some, but not all, of the neutrino
incoherent evolution. By comparing the spin and neutrino systems, we find no
evidence for the violation of the accepted one-body description, though the
argument involves some subtleties not appreciated before. The analysis in this
paper may apply to other two-state systems beyond the neutrino field.Comment: 22 pages, 7 figure
Diamond electro-optomechanical resonators integrated in nanophotonic circuits
Diamond integrated photonic devices are promising candidates for emerging
applications in nanophotonics and quantum optics. Here we demonstrate active
modulation of diamond nanophotonic circuits by exploiting mechanical degrees of
freedom in free-standing diamond electro-optomechanical resonators. We obtain
high quality factors up to 9600, allowing us to read out the driven
nanomechanical response with integrated optical interferometers with high
sensitivity. We are able to excite higher order mechanical modes up to 115 MHz
and observe the nanomechanical response also under ambient conditions.Comment: 15 pages, 4 figure
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