Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Every triangle-free planar graph has a planar upward drawing (1993)
    Springer
    Order 10 (1993), S. 1-16 
    Details
    ISSN: 1572-9273
    Keywords: 06A06 ; Planar graph ; triangle-free ; upward drawing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract A planar ordered set has a triangle-free, planar covering graph; on the other hand, there are nonplanar ordered sets whose covering graphs are planar. We show thatevery triangle-free planar graph has a planar upward drawing. This planar upward drawing can be constructed in time, polynomial in the number of vertices. Our results shed light on the apparently difficult problem, of long-standing, whether there is aneffective planarity-testing procedure for an ordered set.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01108704
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    The Complexity of Upward Drawings on Spheres (1997)
    Springer
    Order 14 (1997), S. 327-363 
    Details
    ISSN: 1572-9273
    Keywords: ordered set ; upward drawing ; sphere ; saddle point
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract Although there is a linear time algorithm to decide whether an ordered set has an upward drawing on a surface topologically equivalence to a sphere, we shall prove that the decision problem whether an ordered set has an upward drawing on a sphere is NP-complete. The proof involves the investigation of the surface topology of ordered sets highlighting especially their saddle points. It echoes the recent, important result due to A. Garg and R. Tamassia (1995) that upward planarity testing is NP-complete, for which we give a new proof.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006095702164
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    On idempotent algebras with $$p_n (\mathfrak{A}) = 2n$$ (1986)
    Springer
    Algebra universalis 23 (1986), S. 313-323 
    Details
    ISSN: 1420-8911
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract In this paper we fully characterize algebras with the number of essentiallyn-ary polynomials pn=2n for alln⩾ (Theorem 1, §3). Using this characterization we prove that the sequence (0, 0, 4) has Grätzer's minimal extension property, and the minimal extension is just the sequence 〈0, 0, 4, 6, 8,...〉.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01230624
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    A Very Strong Set Theory? (1998)
    Springer
    Studia logica 61 (1998), S. 171-178 
    Details
    ISSN: 1572-8730
    Keywords: set theory ; consistency ; axioms ; comprehension
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Philosophy
    Notes: Abstract Using two distinct membership symbols makes possible to base set theory on one general axiom schema of comprehension. Is the resulting system consistent? Can set theory and mathematics be based on a single axiom schema of comprehension?
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005048329677
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Thep n-sequences of idempotent algebras are strictly increasing, II (1991)
    Springer
    Algebra universalis 28 (1991), S. 453-458 
    Details
    ISSN: 1420-8911
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01195856
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...