6,868 research outputs found

### Morse-Novikov critical point theory, Cohn localization and Dirichlet units

In this paper we construct a Universal chain complex, counting zeros of
closed 1-forms on a manifold. The Universal complex is a refinement of the well
known Novikov complex; it relates the homotopy type of the manifold, after a
suitable noncommutative localization, with the numbers of zeros of different
indices which may have closed 1-forms within a given cohomology class. The Main
Theorem of the paper generalizes the result of a joint paper with A. Ranicki,
which treats the special case of closed 1-forms having integral cohomology
classes. The present paper also describes a number of new inequalities, giving
topological lower bounds on the number of zeroes of closed 1-forms. In
particular, such estimates are provided by the homology of flat line bundles
with monodromy described by complex numbers which are not Dirichlet units

### Homological Domination in Large Random Simplicial Complexes

In this paper we state the homological domination principle for random
multi-parameter simplicial complexes, claiming that the Betti number in one
specific dimension (which is explicitly determined by the probability
multi-parameter) significantly dominates the Betti numbers in all other
dimensions. We also state and discuss evidence for two interesting conjectures
which would imply a stronger version of the homological domination principle,
namely that generically homology of a random simplicial complex coincides with
that of a wedges of k-dimensional spheres. These two conjectures imply that
under an additional assumption (specified in the paper) a random simplicial
complex collapses to a k-dimensional complex homotopy equivalent to a wedge of
spheres of dimension k.Comment: 8 pages, 1 figur

### Efficiently modeling neural networks on massively parallel computers

Neural networks are a very useful tool for analyzing and modeling complex real world systems. Applying neural network simulations to real world problems generally involves large amounts of data and massive amounts of computation. To efficiently handle the computational requirements of large problems, we have implemented at Los Alamos a highly efficient neural network compiler for serial computers, vector computers, vector parallel computers, and fine grain SIMD computers such as the CM-2 connection machine. This paper describes the mapping used by the compiler to implement feed-forward backpropagation neural networks for a SIMD (Single Instruction Multiple Data) architecture parallel computer. Thinking Machines Corporation has benchmarked our code at 1.3 billion interconnects per second (approximately 3 gigaflops) on a 64,000 processor CM-2 connection machine (Singer 1990). This mapping is applicable to other SIMD computers and can be implemented on MIMD computers such as the CM-5 connection machine. Our mapping has virtually no communications overhead with the exception of the communications required for a global summation across the processors (which has a sub-linear runtime growth on the order of O(log(number of processors)). We can efficiently model very large neural networks which have many neurons and interconnects and our mapping can extend to arbitrarily large networks (within memory limitations) by merging the memory space of separate processors with fast adjacent processor interprocessor communications. This paper will consider the simulation of only feed forward neural network although this method is extendable to recurrent networks

### L^2 torsion without the determinant class condition and extended L^2 cohomology

We associate determinant lines to objects of the extended abelian category
built out of a von Neumann category with a trace. Using this we suggest
constructions of the combinatorial and the analytic L^2 torsions which, unlike
the work of the previous authors, requires no additional assumptions; in
particular we do not impose the determinant class condition. The resulting
torsions are elements of the determinant line of the extended L^2 cohomology.
Under the determinant class assumption the L^2 torsions of this paper
specialize to the invariants studied in our previous work. Applying a recent
theorem of D. Burghelea, L. Friedlander and T. Kappeler we obtain a Cheeger -
Muller type theorem stating the equality between the combinatorial and the
analytic L^2 torsions.Comment: 39 page

### Product Market Competition, Union Organizing Activity, and Employer Resistence

We develop and estimate a model of the union's optimal extent of organizing activity that accounts for the decision of employers regarding resistance to union organizing. The central exogenous variable in the analysis is the quantity of quasi-rents per worker available to be split between unions and employers. We measure available quasi-rents per worker as the difference per worker between total industry revenues net of raw materials costs and labor costs evaluated at the opportunity cost of the workers. Using two-digit industry level data for thirty-five U.S. industries for the period 1955 through 1986, we find that both organizing activity and employer resistance to unionization are positively related to available quasi-rents per worker. However, there is still a strong negative trend in union organizing activity and a strong positive trend in employer resistance after controlling for quasi-rents per worker. Thus, the explanation for the decline in union organizing activity and the increase in employer resistance to unionization since the mid 1970's lies elsewhere.

### Lyapunov 1-forms for flows

In this paper we find conditions which guarantee that a given flow $\Phi$ on
a compact metric space $X$ admits a Lyapunov one-form $\omega$ lying in a
prescribed \v{C}ech cohomology class $\xi\in \check H^1(X;\R)$. These
conditions are formulated in terms of the restriction of $\xi$ to the chain
recurrent set of $\Phi$. The result of the paper may be viewed as a
generalization of a well-known theorem of C. Conley about the existence of
Lyapunov functions.Comment: 27 pages, 3 figures. This revised version incorporates a few minor
improvement

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