22,951 research outputs found
Combinatorial Formulas for Macdonald and Hall-Littlewood Polynomials of Types A and C. Extended Abstract
A breakthrough in the theory of (type A) Macdonald polynomials is due to
Haglund, Haiman and Loehr, who exhibited a combinatorial formula for these
polynomials in terms of fillings of Young diagrams. Recently, Ram and Yip gave
a formula for the Macdonald polynomials of arbitrary type in terms of the
corresponding affine Weyl group. In this paper, we show that a
Haglund-Haiman-Loehr type formula follows naturally from the more general
Ram-Yip formula, via compression. Then we extend this approach to the
Hall-Littlewood polynomials of type C, which are specializations of the
corresponding Macdonald polynomials at q=0. We note that no analog of the
Haglund-Haiman-Loehr formula exists beyond type A, so our work is a first step
towards finding such a formula
Miniature distributed filters for software re-configurable radio applications
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Steric constraints in model proteins
A simple lattice model for proteins that allows for distinct sizes of the
amino acids is presented. The model is found to lead to a significant number of
conformations that are the unique ground state of one or more sequences or
encodable. Furthermore, several of the encodable structures are highly
designable and are the non-degenerate ground state of several sequences. Even
though the native state conformations are typically compact, not all compact
conformations are encodable. The incorporation of the hydrophobic and polar
nature of amino acids further enhances the attractive features of the model.Comment: RevTex, 5 pages, 3 postscript figure
Unified perspective on proteins: A physics approach
We study a physical system which, while devoid of the complexity one usually
associates with proteins, nevertheless displays a remarkable array of
protein-like properties. The constructive hypothesis that this striking
resemblance is not accidental leads not only to a unified framework for
understanding protein folding, amyloid formation and protein interactions but
also has implications for natural selection.Comment: 26 pages, 15 figures, to appear on Phys. Rev.
The Nature of the Driving Mechanism in the Pulsating Hybrid PG 1159 Star Abell 43
We extend our previous pulsational stability analyses of PG 1159 stars by
modeling the hybrid PG 1159 type star Abell 43. We show that the standard
kappa-mechanism due to the ionization of C and O in the envelope of this H-rich
PG 1159 star is perfectly able to drive g-mode pulsations. Thus, contrary to a
recent suggestion, there is no need to invoke any new or exotic mechanism to
explain the pulsational instabilities observed in this particular star. Our
expected instability band for l = 1 modes extends in period from ~ 2604 s to ~
5529 s, which is consistent with the available photometric observations of
Abell 43. We also suggest that efforts to detect luminosity variations in its
sibling NGC 7094 be pursued.Comment: 3 pages, 1 figure, Accepted for publication in A&
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