Dear Joao,

If the question is: Let S and T be semigroups of transformations of degree n where |S|=10 and |T|=11. Then is S a subsemigroup of T?

Then the answer is yes, just use ForAll(S, x-> x in T);

If the question is: Let S be a semigroup of transformations where |S| =10. Then does there exist T such that |T|=11 and S embeds in T?

Then the answer is no, there is no method installed in GAP to handle this situation.

If the question is: Let S be a semigroup of degree 10 given by its Cayley table and let T be a semigroup of degree 11 given by its Cayley table. Then is S isomorphic to a subsemigroup of T?

Then the answer is: it is possible to do this in GAP but the method is not efficient. Look at the orbits of the 11 10x10 subtables of the Cayley table of T inside the symmetric group on 11 points acting on the pairs (i,j) i, j in {1,...,11}. If the Cayley table for S lies in any of these orbits, then the answer is yes! Otherwise, the answer is no. However it might take a long time to tell you an answer.

Let me know if that helps.

Regards,

James





Message: 6
Date: Fri, 15 Jun 2007 14:47:32 +0100 (WEST)
From: Joao Araujo <[EMAIL PROTECTED]>
Subject: [GAP Forum] test for subsemigroups
To: [EMAIL PROTECTED]
Message-ID: <[EMAIL PROTECTED]>
Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed


Dear Forum,

I would be grateful if someone could tell me if there is in GAP an
easy way to check if a 10-elements semigroup of transformations S
can be embedded in an 11-elements semigroup of transformations T.

I thank in advance,
Joao

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