64,858 research outputs found
Flexible matrix composite laminated disk/ring flywheel
An energy storage flywheel consisting of a quasi-isotropic composite disk overwrapped by a circumferentially wound ring made of carbon fiber and a elastometric matrix is proposed. Through analysis it was demonstrated that with an elastomeric matrix to relieve the radial stresses, a laminated disk/ring flywheel can be designed to store a least 80.3 Wh/kg or about 68% more than previous disk/ring designs. at the same time the simple construction is preserved
Interacting Quantum Topologies and the Quantum Hall Effect
The algebra of observables of planar electrons subject to a constant
background magnetic field B is given by A_theta(R^2) x A_theta(R^2) the product
of two mutually commuting Moyal algebras. It describes the free Hamiltonian and
the guiding centre coordinates. We argue that A_theta(R^2) itself furnishes a
representation space for the actions of these two Moyal algebras, and suggest
physical arguments for this choice of the representation space. We give the
proper setup to couple the matter fields based on A_theta(R^2) to
electromagnetic fields which are described by the abelian commutative gauge
group G_c(U(1)), i.e. gauge fields based on A_0(R^2). This enables us to give a
manifestly gauge covariant formulation of integer quantum Hall effect (IQHE).
Thus, we can view IQHE as an elementary example of interacting quantum
topologies, where matter and gauge fields based on algebras A_theta^prime with
different theta^prime appear. Two-particle wave functions in this approach are
based on A_theta(R^2) x A_theta(R^2). We find that the full symmetry group in
IQHE, which is the semi-direct product SO(2) \ltimes G_c(U(1)) acts on this
tensor product using the twisted coproduct Delta_theta. Consequently, as we
show, many particle sectors of each Landau level have twisted statistics. As an
example, we find the twisted two particle Laughlin wave functions.Comment: 10 pages, LaTeX, Corrected typos, Published versio
Fe and N self-diffusion in non-magnetic Fe:N
Fe and N self-diffusion in non-magnetic FeN has been studied using neutron
reflectivity. The isotope labelled multilayers, FeN/57Fe:N and Fe:N/Fe:15N were
prepared using magnetron sputtering. It was remarkable to observe that N
diffusion was slower compared to Fe while the atomic size of Fe is larger
compared to N. An attempt has been made to understand the diffusion of Fe and N
in non-magnetic Fe:N
Noncommutative BTZ Black Hole and Discrete Time
We search for all Poisson brackets for the BTZ black hole which are
consistent with the geometry of the commutative solution and are of lowest
order in the embedding coordinates. For arbitrary values for the angular
momentum we obtain two two-parameter families of contact structures. We obtain
the symplectic leaves, which characterize the irreducible representations of
the noncommutative theory. The requirement that they be invariant under the
action of the isometry group restricts to symplectic leaves,
where is associated with the Schwarzschild time. Quantization may then lead
to a discrete spectrum for the time operator.Comment: 10 page
Waves on Noncommutative Spacetimes
Waves on ``commutative'' spacetimes like R^d are elements of the commutative
algebra C^0(R^d) of functions on R^d. When C^0(R^d) is deformed to a
noncommutative algebra {\cal A}_\theta (R^d) with deformation parameter \theta
({\cal A}_0 (R^d) = C^0(R^d)), waves being its elements, are no longer
complex-valued functions on R^d. Rules for their interpretation, such as
measurement of their intensity, and energy, thus need to be stated. We address
this task here. We then apply the rules to interference and diffraction for d
\leq 4 and with time-space noncommutativity. Novel phenomena are encountered.
Thus when the time of observation T is so brief that T \leq 2 \theta w, where w
is the frequency of incident waves, no interference can be observed. For larger
times, the interference pattern is deformed and depends on \frac{\theta w}{T}.
It approaches the commutative pattern only when \frac{\theta w}{T} goes to 0.
As an application, we discuss interference of star light due to cosmic strings.Comment: 19 pages, 5 figures, LaTeX, added references, corrected typo
Laser-assisted solar cell metallization processing
Laser-assisted processing techniques for producing high-quality solar cell metallization patterns are being investigated, developed, and characterized. The tasks comprising these investigations are outlined
The Chern-Simons Source as a Conformal Family and Its Vertex Operators
In a previous work, a straightforward canonical approach to the source-free
quantum Chern-Simons dynamics was developed. It makes use of neither gauge
conditions nor functional integrals and needs only ideas known from QCD and
quantum gravity. It gives Witten's conformal edge states in a simple way when
the spatial slice is a disc. Here we extend the formalism by including sources
as well. The quantum states of a source with a fixed spatial location are shown
to be those of a conformal family, a result also discovered first by Witten.
The internal states of a source are not thus associated with just a single ray
of a Hilbert space. Vertex operators for both abelian and nonabelian sources
are constructed. The regularized abelian Wilson line is proved to be a vertex
operator. We also argue in favor of a similar nonabelian result. The
spin-statistics theorem is established for Chern-Simons dynamics even though
the sources are not described by relativistic quantum fields. The proof employs
geometrical methods which we find are strikingly transparent and pleasing. It
is based on the research of European physicists about ``fields localized on
cones.'
Non-destructive Orthonormal State Discrimination
We provide explicit quantum circuits for the non-destructive deterministic
discrimination of Bell states in the Hilbert space , where is
qudit dimension. We discuss a method for generalizing this to non-destructive
measurements on any set of orthogonal states distributed among parties.
From the practical viewpoint, we show that such non-destructive measurements
can help lower quantum communication complexity under certain conditions.Comment: 11 pages, 6 fugure
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