𝔖 Bobbio Scriptorium
✦   LIBER   ✦

Semiretracts—a counterexample and some results

✍ Scribed by Wit Foryś; Tomasz Krawczyk; James A. Anderson

Publisher
Elsevier Science
Year
2003
Tongue
English
Weight
223 KB
Volume
307
Category
Article
ISSN
0304-3975

No coin nor oath required. For personal study only.

✦ Synopsis

In the paper (Theoret. Comput. Sci. 237 (2000)) Anderson present a theorem which characterizes any semiretract S by means of two retracts R and R!: The ÿrst part of the paper contains a counterexample for this characterization. Then some results are presented which ÿnally lead to the theorem which determines for a given semiretract S the minimal number of retracts R1; : : : ; Rm such that the equality S = m i=1 Ri holds.

📜 SIMILAR VOLUMES

Some Positive Results and Counterexample
Some Positive Results and Counterexamples in Comonotone Approximation
✍ D. Leviatan; I.A. Shevchuk 📂 Article 📅 1997 🏛 Elsevier Science 🌐 English ⚖ 320 KB

Let f be a continuous function on [&1, 1], which changes its monotonicity finitely many times in the interval, say s times. We discuss the validity of Jackson-type estimates for the approximation of f by algebraic polynomials that are comonotone with it. While we prove the validity of the Jackson-ty

Indecomposabler-graphs and some other co
Indecomposabler-graphs and some other counterexamples
✍ Rizzi, Romeo 📂 Article 📅 1999 🏛 John Wiley and Sons 🌐 English ⚖ 260 KB

An r-graph is any graph that can be obtained as a conic combination of its own 1-factors. An r-graph G(V, E) is said to be indecomposable when its edge set E cannot be partitioned as E = E 1 ∪ E 2 so that G i (V, E i ) is an r igraph for i = 1, 2 and, for some r 1 , r 2 . We give an indecomposable r