DATE: Tuesday, October 20 (2009), at 10:40am
PLACE: LIT 305
SPEAKER: Alexander Berkovich
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TITLE:
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Ternary diagonal quadratic forms that represent all odd positive integers
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ABSTRACT:
It is well known that no positive ternary form is universal. However,
at least 20 and no more than 23 positive ternary forms represent all odd integers >0.
The above is due to Kaplansky.
I will try to convince you that
x2+ y2+ 2z2,
x2+ 2y2+ 3z2,
x2+ 2y2+ 4z2
are the only three diagonal ternaries with this property.
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