搜索结果：1979

In 1979, Jeltsch [Numer. Math. 32 (1979), 167-181] conjectured that every zero-stable Brown method is stiffly stable. For Brown $(K,L)$ methods, Meneguette subsequently reduced the relevant $A_0$-stability question to a zero-location property for a family of perturbed characteristic polynomials. A closely related perturbation question already appeared in his 1987 Oxford doctoral thesis, and he later posed a broader purely polynomial version of the problem in 1994 [SIAM Review 36 (1994), 656-657]. We provide a complete solution to Meneguette's polynomial problem.

Let $A$ and $B$ be finite ordered sets. We show that if the ordered sets of isotone self-maps $A^A$ and $B^B$ (ordered pointwise) are isomorphic, then $A$ and $B$ are isomorphic. This resolves a question originating with D. Duffus in 1978, with related results by D. Duffus--R. Wille in 1979 and J. Farley in 2023.

In 1979, James B.~Saxe published an extended summary on the complexity of the Distance Geometry Problem in the proceedings of the 17th Allerton Conference. Many of the proofs in his paper are sketches, and even the whole proofs do not have all the details. In this paper we provide a commentary to Saxe's results and hopefully more understandable versions thereof.

The purpose of this overview is to explain the enormous impact of Les Valiant's eponymous short conference contribution from 1979 on the development of algebraic complexity.

This paper contains a set of theoretical results concerning the coupling tensor B of an anisotropic laminate and of its compliance corresponding B. The theoretical analysis and the mechanical results are obtained through an extensive use of the so-called polar formalism, introduced as early as 1979 by Prof. G. Verchery.

In 1979 Babai found a clever argument to prove that every connected vertex transitive graph on $n \ge 3$ vertices contains a cycle of length at least $\sqrt{3n}$. Here we modify his approach to show that such graphs must contain a cycle of length at least $(1 - o(1))n^{3/5}$.

We show that the Cohen--Lyndon property holds for all non-metric small-cancellation quotients. This generalises the analogous result from the metric small-cancellation setting, and answers a question asked by Lyndon in 1966 and by Wall in his 1979 problem list.

We revisit the following problem: Given a convex polygon $P$, find the largest-area inscribed triangle. We show by example that the linear-time algorithm presented in 1979 by Dobkin and Snyder for solving this problem fails. We then proceed to show that with a small adaptation, their approach does lead to a quadratic-time algorithm. We also present a more involved $O(n\log n)$ time divide-and-conquer algorithm. Also we show by example that the algorithm presented in 1979 by Dobkin and Snyder for finding the largest-area $k$-gon that is inscribed in a convex polygon fails to find the optimal solution for $k=4$. Finally, we discuss the implications of our discoveries on the literature.

As it is well-known, the year 2005 has been the centenary of the "annus mirabilis" (1905) during which Albert Einstein published four fundamental papers of his. But already in 1979, for the centenary of Einstein's birth, the world celebrated his monumantal work. In Italy too, there appeared scientific books, and many semi-popularization (or popularization) articles. The present paper represents a talk delivered in Italian, at the invitation of the Nobel Foundation (Sanremo, IM; Italy), in time for its publication in 1979. This article has been however reprinted, much more recently, in 2002, by the "Centro DIEA", Faculty of Engineering, University of Bologna, Bologna, Italy [and its source-file, in html, has been prepared with DIEA's collaboration]. We present here a description of the human, philosophycal and scientific background, starting from which Einstein produced his amazing results: Indeed, we try to show why Einstein's writings today are still so important not only for pure physics (and technology!), but also for our epistemological understanding of the procedures followed by science, and by our own mind, in their development, as well as for our philosophical views about th

In 1979 I. Ciorănescu and L. Zsidó have proved a minimum modulus theorem for entire functions dominated by the restriction to the positive half axis of a canonical product of genus zero, having all roots on the positive imaginary axis and satisfying a certain condition. Here we prove that the above result is optimal: if a canonical product ω of genus zero, having all roots on the positive imaginary axis, does not satisfy the condition in the 1979 paper, then always there exists an entire function dominated by the restriction to the positive half axis of ω, which does not satisfy the desired minimum modulus conclusion. This has relevant implication concerning the subjectivity of ultra differential operators with constant coefficients.

Coste and Roy in 1979 defined a structural sheaf on the real Zariski spectrum of a semi-real ring $A$ and asked whether the ring of the global sections is $\sum^{-1}_1 A$ where $\sum_1$ is the multiplicative subset $\{1+\sum_{i=1}^n a_i^2|a_i\in A, n\in N\}$ of $A$. We give a positive answer to this question for real rings and integral domains.

We design a randomized algorithm that finds a Hamilton cycle in $\mathcal{O}(n)$ time with high probability in a random graph $G_{n,p}$ with edge probability $p\ge C \log n / n$. This closes a gap left open in a seminal paper by Angluin and Valiant from 1979.

We show that every sufficiently large oriented graph with minimum in- and outdegree at least (3n-4)/8 contains a Hamilton cycle. This is best possible and solves a problem of Thomassen from 1979.

In 1979, Hakimi and Schmeichel considered the problem of maximizing the number of cycles of a given length in an $n$-vertex planar graph. They precisely determined the maximum number of triangles and $4$-cycles and presented a conjecture for the maximum number of pentagons. In this work, we confirm their conjecture. Even more, we characterize the $n$-vertex, planar graphs with the maximum number of pentagons.