The dynamical origin of physiological instructions used in birdsong production

In this work we report experimental measurements of pressure patterns used in canary song. We find that these patterns are qualitatively similar to the subharmonic solutions of a simple dynamical system. This is built to account for the activities of subpopulations of neurons arranged in a simple architecture compatible with anatomical observations. The consequences of Hebbian plasticity in the coupling between the driving and the driven systems are outlined.      

Dynamics of learning and generalization in perceptrons with constraints

Depending on the kind of constraints imposed on the weights of a perceptron, learning can be a combinatorially hard problem. As an example of this type, I discuss a perception with binary weights comparing results obtained from replica theory, dynamic mean field theory and simulated annealing. Contrary to the replica calculation, dynamics yields information about the performance of a polynomial algorithm in a situation where the best solution cannot be found in polynomial time. I also discuss improved learning algorithms and results for finite size perceptrons.     

Nonlinear model predicts diverse respiratory patterns of birdsong

A central aspect of the motor control of birdsong production is the capacity to generate diverse respiratory rhythms, which determine the coarse temporal pattern of song. The neural mechanisms that underlie this diversity of respiratory gestures and the resulting acoustic syllables are largely unknown. We show that the respiratory patterns of the highly complex and variable temporal organization of song in the canary (Serinus canaria) can be generated as solutions of a simple model describing the integration between song control and respiratory centers. This example suggests that subharmonic behavior can play an important role in providing a complex variety of responses with minimal neural substrate.     

Temporal scales of auditory objects underlying birdsong vocal recognition

Vocal recognition is common among songbirds, and provides an excellent model system to study the perceptual and neurobiological mechanisms for processing natural vocal communication signals. Male European starlings, a species of songbird, learn to recognize the songs of multiple conspecific males by attending to stereotyped acoustic patterns, and these learned patterns elicit selective neuronal responses in auditory forebrain neurons. The present study investigates the perceptual grouping of spectrotemporal acoustic patterns in starling song at multiple temporal scales. The results show that permutations in sequencing of submotif acoustic features have significant effects on song recognition, and that these effects are specific to songs that comprise learned motifs. The observations suggest that (1) motifs form auditory objects embedded in a hierarchy of acoustic patterns, (2) that object-based song perception emerges without explicit reinforcement, and (3) that multiple temporal scales within the acoustic pattern hierarchy convey information about the individual identity of the singer. The authors discuss the results in the context of auditory object formation and talker recognition.     

Solution to constraints in Wess-Zumino supergravity formalism

We explicitly solve the constraints of the superfield supergravity formalism of Wess and Zumino, for an arbitrary gauge, in terms of superfields. Wess and Zumino's action turns out to be identical to one of a class of actions found earlier by the author: the one with the minimal set of auxiliary fields. We also show how to write chiral Lagrangians, including the cosmological term and the Lagrangian for conformal supergravity.     

Spatial unmasking of birdsong in human listeners: energetic and informational factors

Spatial unmasking describes the improvement in the detection or identification of a target sound afforded by separating it spatially from simultaneous masking sounds. This effect has been studied extensively for speech intelligibility in the presence of interfering sounds. In the current study, listeners identified zebra finch song, which shares many acoustic properties with speech but lacks semantic and linguistic content. Three maskers with the same long-term spectral content but different short-term statistics were used: (1) chorus (combinations of unfamiliar zebra finch songs), (2) song-shaped noise (broadband noise with the average spectrum of chorus), and (3) chorus-modulated noise (song-shaped noise multiplied by the broadband envelope from a chorus masker). The amount of masking and spatial unmasking depended on the masker and there was evidence of release from both energetic and informational masking. Spatial unmasking was greatest for the statistically similar chorus masker. For the two noise maskers, there was less spatial unmasking and it was wholly accounted for by the relative target and masker levels at the acoustically better ear. The results share many features with analogous results using speech targets, suggesting that spatial separation aids in the segregation of complex natural sounds through mechanisms that are not specific to speech.     

Torsion constraints in supergeometry

We derive the torsion constraints for superspace versions of supergravity theories by means of the theory ofG-structures. We also discuss superconformal geometry and superKähler geometry.Permanent address as of September 1, 1990: Department of Mathematics, University of Michigan, Ann Arbor, MI 48109, USA     

Energy constraints in vortex-excited vibrations

Excitation or damping of flow-induced vibrations depends upon the magnitude and the phase relationship between the fluid dynamic force and the oscillatory motion of the body. These have been measured for two aerofoil shapes in mechanically controlled heaving motion in a water channel. At the same time, measurements have been made of the strength and spacing of the associated vortex trails. To help interpret the significance of these measurements, an analysis based upon energy conservation has been performed. When taken together with the classical momentum equation, this yields a relationship giving the energy available for vibration work in terms of three dimensionless vortex trail parameters. Comparing this analysis with the experimental data leads to a qualitative discussion of the significance of the vortex formation mechanism in controlling the excitation or damping of that class of vibrations which is affected by vortex shedding.     

Analytical constraints in extended supersymmetry

Starting from the deep relation between the system of numbers and extended supersymmetry we can obtain analytical constraints for superfields.Presented at the International Symposium Selected Topics in Quantum Field Theory and Mathematical Physics, Bechyn, Czechoslovakia, June 14–19, 1981.     

Integral constraints in general relativity

Using a covariant formalism we derive the conditions for there to exist integral constraints on energy-momentum perturbations in an arbitrary background spacetime.     

Many-body localization in disorder-free systems: The importance of finite-size constraints

Recently it has been suggested that many-body localization (MBL) can occur in translation-invariant systems, and candidate 1D models have been proposed. We find that such models, in contrast to MBL systems with quenched disorder, typically exhibit much more severe finite-size effects due to the presence of two or more vastly different energy scales. In a finite system, this can artificially split the density of states (DOS) into bands separated by large gaps. We argue for such models to faithfully represent the thermodynamic limit behavior, the ratio of relevant coupling must exceed a certain system-size depedent cutoff, chosen such that various bands in the DOS overlap one another. Setting the parameters this way to minimize finite-size effects, we study several translation-invariant MBL candidate models using exact diagonalization. Based on diagnostics including entanglement and local observables, we observe thermal (ergodic), rather than MBL-like behavior. Our results suggest that MBL in translation-invariant systems with two or more very different energy scales is less robust than perturbative arguments suggest, possibly pointing to the importance of non-perturbative effects which induce delocalization in the thermodynamic limit.     

Unification constraints in composite models

We consider unification constraints on composite models with special emphasis on two-loop effects due to relatively large metacolor coupling. Two classes of models are discussed. The first consists of those which do not have gaugedSU(2) _W and the second of those which include technicolor and gaugedSU(2) _W . The outcome is that in each specific composite model the two-loop contributions can affect noticeably several important quantities, such as the grand unified mass or the weak mixing angle. We find also that it may not be possible to have a unified composite model based on the symmetryG _MC ×SU(3) _c × U(1) _em with low (<10⁶ GeV) metacolor mass scale.     

Chiral constraints in dual models

An attempt is made to see how much of chiral symmetry is contained in dual models for pseudoscalar mesons. The chiral constraints are found to be contained in dual models as either dynamical restriction or kinematical factors. At the phenomenological level there is no serious inconsistency.     

Experimental constraints on polarizability corrections to hydrogen hyperfine structure

We present a state-of-the-art evaluation of the polarizability corrections--the inelastic nucleon corrections--to the hydrogen ground-state hyperfine splitting using analytic fits to the most recent data. We find a value Delta(pol)=1.3+/-0.3 ppm. This is 1-2 ppm smaller than the value of Delta(pol) deduced using hyperfine splitting data and elastic nucleon corrections obtained from modern form factor fits.     

Transition to special canonical coordinates for systems with constraints

When using the Dirac hamiltonization of Lagrange systems with constraints, it is convenient to perform a canonical transformation such that the constraints become linear combinations of only a subset of the new variables, while the primary constraints can be identified with some of the variables belonging to this subset. We prove the existence of such canonical transformation, as well as the possibility of separation of first-class constraints.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 93–97, August, 1983.