49,191 research outputs found

    Spin 1 inversion: a Majorana tensor force for deuteron alpha scattering

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    We demonstrate, for the first time, successful S-matrix to potential inversion for spin one projectiles with non-diagonal SlljS^j_{ll'} yielding a TRT_{\rm R} interaction. The method is a generalization of the iterative-perturbative, IP, method. We present a test case indicating the degree of uniqueness of the potential. The method is adapted, using established procedures, into direct observable to potential inversion, fitting σ\sigma, iT11{\rm i}T_{11}, T20T_{20}, T21T_{21} and T22T_{22} for d + alpha scattering over a range of energies near 10 MeV. The TRT_{\rm R} interaction which we find is very different from that proposed elsewhere, both real and imaginary parts being very different for odd and even parity channels.Comment: 7 pages Revtex, 4 ps figure

    Dynamics of broken symmetry lambda phi^4 field theory

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    We study the domain of validity of a Schwinger-Dyson (SD) approach to non-equilibrium dynamics when there is broken symmetry. We perform exact numerical simulations of the one- and two-point functions of lambda phi^4 field theory in 1+1 dimensions in the classical domain for initial conditions where < phi(x) > not equal to 0. We compare these results to two self-consistent truncations of the SD equations which ignore three-point vertex function corrections. The first approximation, which sets the three-point function to one (the bare vertex approximation (BVA)) gives an excellent description for < phi(x) > = phi(t). The second approximation which ignores higher in 1/N corrections to the 2-PI generating functional (2PI -1/N expansion) is not as accurate for phi(t). Both approximations have serious deficiencies in describing the two-point function when phi(0) > .4.Comment: 10 pages, 6 figure

    Coordination and synergism between visual and vocal display in the brown-headed cowbirds

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    Journal ArticleSexually selected acoustic signaling is accompanied by visual displays in many birds. The motor integration of visual and vocal displays has not been extensively studied. Brown-headed cowbirds (Molothrus ater) "puff up" prior to song, move their wings during the song and conclude with a bow. The Society for Neuroscience 33rd Annual Meeting Selected Abstracts Coordination and synergism between visual and vocal display in brown - headed cowbirds. B. G. Cooper; F. Goller Dept. Biol, Univ. Utah, Salt Lake City, UT, USA Program Number: 294.13 Presentation Time: Sunday, Nov. 9, 1: 00 PM - 2: 00 P

    Respiratory motor correlates of song plasticity in young adult zebra finches

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    Journal ArticleYoung adult zebra finches (Taeniopygia guttata, 90150 phd) sing a stereotyped song, but can show rapid changes in song structure if sensory feedback is disrupted. The vocal motor correlates accompanying induced song plasticity have not yet been examined. To investigate motor changes underlying song plasticity, air sac pressure and vocal output were recorded in zebra finches (N=4, 90-120 phd) prior to, during, and after removal (reversal) of a clamp placed in each bronchus. The clamp restricted movement of the lateral labia and reduced, or completely eliminated, sound production during song

    Study of a signal processor employing a synthetic phase isolator

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    Evaluation of signal data processor employing synthetic phase isolator techniqu

    Exact and approximate dynamics of the quantum mechanical O(N) model

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    We study a quantum dynamical system of N, O(N) symmetric, nonlinear oscillators as a toy model to investigate the systematics of a 1/N expansion. The closed time path (CTP) formalism melded with an expansion in 1/N is used to derive time evolution equations valid to order 1/N (next-to-leading order). The effective potential is also obtained to this order and its properties areelucidated. In order to compare theoretical predictions against numerical solutions of the time-dependent Schrodinger equation, we consider two initial conditions consistent with O(N) symmetry, one of them a quantum roll, the other a wave packet initially to one side of the potential minimum, whose center has all coordinates equal. For the case of the quantum roll we map out the domain of validity of the large-N expansion. We discuss unitarity violation in the 1/N expansion; a well-known problem faced by moment truncation techniques. The 1/N results, both static and dynamic, are also compared to those given by the Hartree variational ansatz at given values of N. We conclude that late-time behavior, where nonlinear effects are significant, is not well-described by either approximation.Comment: 16 pages, 12 figrures, revte

    Twisting moduli for GL(2)

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    We prove various converse theorems for automorphic forms on \Gamma_0(N), each assuming fewer twisted functional equations than the last. We show that no twisting at all is needed for holomorphic modular forms in the case that N\in{18,20,24} - these integers are the smallest multiples of 4 or 9 not covered by earlier work of Conrey–Farmer. This development is a consequence of finding generating sets for \Gamma_0(N) such that each generator can be written as a product of special matrices. As for real-analytic Maass forms of even (resp. odd) weight we prove the analogous statement for 1\leq N\leq 12, 14\leq N\leq18 and N\in{16,18} (resp. 1\leq N\leq 12, 14\leq N\leq 18 and N\in{20,23,24})

    Protein-mediated dethreading of a biotin-functionalised pseudorotaxane

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    In this article, we describe the synthesis of new biotin-functionalised naphthalene derivatives 3 and 4 and their complexation behaviour with avidin and neutravidin using a range of analytical techniques. We have shown using 2-(4prime or minute-hydroxyazobenzene)benzoic acid displacement and ITC experiments{,} that compounds 3 and 4 have the propensity to form reasonably high-affinity bioconjugates with avidin and neutravidin. We have also demonstrated using 1H NMR{,} UV-vis and fluorescence spectroscopy that the naphthalene moiety of 3 and 4 facilitates the formation of pseudorotaxane-like structures with 1 in water. We have then investigated the ability of avidin and neutravidin to modulate the complexation between 1 and 3 or 4. UV-vis and fluorescence spectroscopy has shown that in both cases the addition of the protein disrupts complexation between the naphthalene moieties of 3 and 4 with 1

    Derivative relation for thermopower in the quantum Hall regime

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    Recently, Tieke et al (to be published in PRL) have observed the relation S_{yx} = alpha B dS_{xx}/dB for the components of the thermopower tensor in the quantum Hall regime, where alpha is a constant and B is the magnetic field. Simon and Halperin (PRL 73, 3278 (1994)) have suggested that an analogous relation observed for the resistivity tensor R_{xx} = \alpha B dR_{xy}/dB can be explained with a model of classical transport in an inhomogeneous medium where the local Hall resistivity is a function of position and the local dissipative resistivity is a small constant. In the present paper, we show that this new thermopower relation can be explained with a similar model.Comment: This paper supercedes cond-mat/9705001 which was withdrawn. 4 pages, Revte
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