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The case i=1

 

A general overview of this case is provided in section 7.2 of Trotter's book [48]. Dushnik was the first to consider the problem in general: In [18], he investigated dim(1,j;n) for values of j large in comparison to n and obtained the following estimates:

Let s and t be positive integers satisfying tex2html_wrap_inline1946 and all of tex2html_wrap_inline1948 , tex2html_wrap_inline1950 , tex2html_wrap_inline1952 . Then

displaymath1932

Dushnik also showed in [18] that the preceding inequalities determine the exact value of dim(1,j;n) whenever tex2html_wrap_inline1956 and tex2html_wrap_inline1958 . The critical value tex2html_wrap_inline1960 is specified by the following conditions: Let tex2html_wrap_inline1962 be the largest positive integer u with tex2html_wrap_inline1966 and satisfying tex2html_wrap_inline1968 for all tex2html_wrap_inline1970 , and put tex2html_wrap_inline1972 (thus tex2html_wrap_inline1974 ).

Dushnik [18] and Trotter [47] use these estimates to give the exact values of dim(1,j;n) for several cases where tex2html_wrap_inline1978 and tex2html_wrap_inline1980 , the values then are tex2html_wrap_inline1982 . See [32], Corollary 2.2 and Theorem 3.3. [47] also contains a table of all values dim(1,i;n) for tex2html_wrap_inline1986 .

If j is kept fixed, the asymptotic behavior of dim(1,j;n) as a function of n was determined by Spencer in [46] by probabilistic methods: tex2html_wrap_inline1994 for fixed 1<j<n. For j=2, Füredi, Hajnal, Rödl and Trotter provide the following asymptotic formula in [22]: tex2html_wrap_inline2000 .

The most recent entry is [33, Theorem 0.7,] where Kierstead provides upper and lower bounds for dim(1,j;n) which differ by a factor of at most tex2html_wrap_inline2004 for j large (compared to n) for some constant c, and by a factor of at most tex2html_wrap_inline2012 for j small (compared to n).



Jürg Schmid