6,393 research outputs found
Phase operators, phase states and vector phase states for SU(3) and SU(2,1)
This paper focuses on phase operators, phase states and vector phase states
for the sl(3) Lie algebra. We introduce a one-parameter generalized oscillator
algebra A(k,2) which provides a unified scheme for dealing with su(3) (for k <
0), su(2,1) (for k > 0) and h(4) x h(4) (for k = 0) symmetries. Finite- and
infinite-dimensional representations of A(k,2) are constructed for k < 0 and k
> 0 or = 0, respectively. Phase operators associated with A(k,2) are defined
and temporally stable phase states (as well as vector phase states) are
constructed as eigenstates of these operators. Finally, we discuss a relation
between quantized phase states and a quadratic discrete Fourier transform and
show how to use these states for constructing mutually unbiased bases
Sharp interface limit for a phase field model in structural optimization
We formulate a general shape and topology optimization problem in structural
optimization by using a phase field approach. This problem is considered in
view of well-posedness and we derive optimality conditions. We relate the
diffuse interface problem to a perimeter penalized sharp interface shape
optimization problem in the sense of -convergence of the reduced
objective functional. Additionally, convergence of the equations of the first
variation can be shown. The limit equations can also be derived directly from
the problem in the sharp interface setting. Numerical computations demonstrate
that the approach can be applied for complex structural optimization problems
Image Storage in Hot Vapors
We theoretically investigate image propagation and storage in hot atomic
vapor. A system is adopted for imaging and an atomic vapor cell is placed
over the transform plane. The Fraunhofer diffraction pattern of an object in
the object plane can thus be transformed into atomic Raman coherence according
to the idea of ``light storage''. We investigate how the stored diffraction
pattern evolves under diffusion. Our result indicates, under appropriate
conditions, that an image can be reconstructed with high fidelity. The main
reason for this procedure to work is the fact that diffusion of opposite-phase
components of the diffraction pattern interfere destructively.Comment: 11 pages, 3 figure
Mass and Spin of Poincare Gauge Theory
We discuss two expressions for the conserved quantities (energy momentum and
angular momentum) of the Poincar\'e Gauge Theory. We show, that the variations
of the Hamiltonians, of which the expressions are the respective boundary
terms, are well defined, if we choose an appropriate phase space for asymptotic
flat gravitating systems. Furthermore, we compare the expressions with others,
known from the literature.Comment: 16 pages, plain-tex; to be published in Gen. Rel. Gra
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