Nuclear Anapole Moments and the Parity-nonconserving Nuclear Interaction

The anapole moment is a parity-odd and time-reversal-even electromagnetic moment. Although it was conjectured shortly after the discovery of parity nonconservation, its existence has not been confirmed until recently in heavy nuclear systems, which are known to be the suitable laboratories because of the many-body enhancement. By carefully identifying the nuclear-spin-dependent atomic parity nonconserving effect, the first clear evidence was found in cesium. In this talk, I will discuss how nuclear anapole moments are used to constrain the parity-nonconserving nuclear force, a still less well-known channel among weak interactions.Comment: 5 pages, 1 figure, uses aipproc.cls. Proceedings of the 15th International Spin Physics Symposiu

An improved sufficient condition for absence of limit cycles in digital filters

It is known that if the state transition matrix A of a digital filter structure is such that D - A^{dagger}DA is positive definite for some diagonal matrix D of positive elements, then all zero-input limit cycles can be suppressed. This paper shows that positive semidefiniteness of D - A^{dagger}DA is in fact sufficient. As a result, it is now possible to explain the absence of limit cycles in Gray-Markel lattice structures based only on the state-space viewpoint

On factorization of a subclass of 2-D digital FIR lossless matricesfor 2-D QMF bank applications

The role of one-dimensional (1-D) digital finite impulse response (FIR) lossless matrices in the design of FIR perfect reconstruction quadrature mirror filter (QMF) banks has been explored previously. Structures which can realize the complete family of FIR lossless transfer matrices, have also been developed, with QMF application in mind. For the case of 2-D QMF banks, the same concept of lossless polyphase matrix has been used to obtain perfect reconstruction. However, the problem of finding a structure to cover all 2-D FIR lossless matrices of a given degree has not been solved. Progress in this direction is reported. A structure which completely covers a well-defined subclass of 2-D digital FIR lossless matrices is obtained

Classical sampling theorems in the context of multirate and polyphase digital filter bank structures

The recovery of a signal from so-called generalized samples is a problem of designing appropriate linear filters called reconstruction (or synthesis) filters. This relationship is reviewed and explored. Novel theorems for the subsampling of sequences are derived by direct use of the digital-filter-bank framework. These results are related to the theory of perfect reconstruction in maximally decimated digital-filter-bank systems. One of the theorems pertains to the subsampling of a sequence and its first few differences and its subsequent stable reconstruction at finite cost with no error. The reconstruction filters turn out to be multiplierless and of the FIR (finite impulse response) type. These ideas are extended to the case of two-dimensional signals by use of a Kronecker formalism. The subsampling of bandlimited sequences is also considered. A sequence x(n ) with a Fourier transform vanishes for |ω|&ges;Lπ/M, where L and M are integers with L<M, can in principle be represented by reducing the data rate by the amount M/L. The digital polyphase framework is used as a convenient tool for the derivation as well as mechanization of the sampling theorem