A következő (V. 4. (péntek), 10:00, Farkas-terem) kombinatorika
szeminárium előadása:

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Füredi Zoltán (Rényi Intézet, Budapest): t-cancellative codes and
hypergraph Turán problems
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A magyar nyelvű előadás abstarct-ja:

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A family  F  of sets is called  t-cancellative  if for any
distinct  t+2   members  A_1, ..., A_t, B, C \in  F
<CENTER>     
A_1\cup A_2 \cup ...\cup A_t \cup B  \neq (not equal)
                         A_1\cup A_2 \cup ...\cup A_t \cup C.</CENTER>
Let  c_t(n)   be the maximum size of a such an  F   on  n
elements. It is known that
<CENTER>     1.5^n /n < c_1(n) < 1.5^n </CENTER>
(Tolhuizen, construction, Frankl and Furedi, upper bound).
Korner and Sinaimeri showed
     0.11  <  lim sup  c_2(n)/ log_2 n   < 0.42

<P>     Here we give an improvement on the upper bound
but mainly we consider  c_t(n,r),  the size of the largest
t-cancellative  r-uniform family on  n  vertices, thus
answering some Turan type questions of  G. O. H.  Katona.

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Minden érdeklődőt szeretettel várunk,

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Péter