I know that the automorphic representation can be defined only for reductive algebraic group.

What property of algebriac group makes it hinder to define for all algebraic group and what nice property of reductive enable us define automorphic representation to it?

And I also wondering whether unitary group is reductive group. I think it does so.

But for me, it is not clear why they are reductive. It's hard to guess it just from the definition of reductiveness.

Would you shed me light on this?

I know that the automorphic representation can be defined only for reductive algebraic group.

What property of algebraic group makes it hinder to define for all algebraic group and what nice property of reductive enable us define automorphic representation to it?

And I also wondering whether unitary group is reductive group. I think it does so.

But for me, it is not clear why they are reductive. It's hard to guess it just from the definition of reductiveness.

Would you shed me light on this?

I know that the automorphic representation can be defined only for reductive algebraic group.

What property of algebriac group makes it hinder to define for all algebraic group and what property of reductive enable to attach automorphic representation to it?

And I also wondering whether unitary group is reductive group. I think it does so.

But for me, it is not clear why they are reductive. It's hard to guess it just from the definition of reductiveness.

Would you shed me light on this?

I know that the automorphic representation can be defined only for reductive algebraic group.

What property of algebriac group makes it hinder to define for all algebraic group and what nice property of reductive enable us define automorphic representation to it?

And I also wondering whether unitary group is reductive group. I think it does so.

But for me, it is not clear why they are reductive. It's hard to guess it just from the definition of reductiveness.

Would you shed me light on this?