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Proceedings of the 44th Symposium on Ring Theory and ...

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GRADED FROBENIUS ALGEBRAS AND QUANTUM BEILINSON<br />

ALGEBRAS<br />

KENTA UEYAMA<br />

Abstract. Frobenius algebras are <strong>on</strong>e <str<strong>on</strong>g>of</str<strong>on</strong>g> <str<strong>on</strong>g>the</str<strong>on</strong>g> important classes <str<strong>on</strong>g>of</str<strong>on</strong>g> algebras studied in<br />

representati<strong>on</strong> <str<strong>on</strong>g>the</str<strong>on</strong>g>ory <str<strong>on</strong>g>of</str<strong>on</strong>g> finite dimensi<strong>on</strong>al algebras. In this article, we will study when<br />

given graded Frobenius Koszul algebras are graded Morita equivalent. As applicati<strong>on</strong>s,<br />

we apply our results to quantum Beilins<strong>on</strong> algebras.<br />

Key Words:<br />

equivalence.<br />

Frobenius Koszul algebras, quantum Beilins<strong>on</strong> algebras, graded Morita<br />

2010 Ma<str<strong>on</strong>g>the</str<strong>on</strong>g>matics Subject Classificati<strong>on</strong>: Primary 16W50, 16S37; Sec<strong>on</strong>dary 16D90.<br />

1. Introducti<strong>on</strong><br />

This is based <strong>on</strong> a joint work with Izuru Mori.<br />

Classificati<strong>on</strong> <str<strong>on</strong>g>of</str<strong>on</strong>g> Frobenius algebras is an active project in representati<strong>on</strong> <str<strong>on</strong>g>the</str<strong>on</strong>g>ory <str<strong>on</strong>g>of</str<strong>on</strong>g><br />

finite dimensi<strong>on</strong>al algebras. This article tries to answer <str<strong>on</strong>g>the</str<strong>on</strong>g> questi<strong>on</strong> when given graded<br />

Frobenius Koszul algebras are graded Morita equivalent, that is, <str<strong>on</strong>g>the</str<strong>on</strong>g>y have equivalent<br />

graded module categories.<br />

This problem is related to classificati<strong>on</strong> <str<strong>on</strong>g>of</str<strong>on</strong>g> quasi-Fano algebras. It is known that every<br />

finite dimensi<strong>on</strong>al algebra <str<strong>on</strong>g>of</str<strong>on</strong>g> global dimensi<strong>on</strong> 1 is a path algebra <str<strong>on</strong>g>of</str<strong>on</strong>g> a finite acyclic<br />

quiver up to Morita equivalence, so such algebras can be classified in terms <str<strong>on</strong>g>of</str<strong>on</strong>g> quivers.<br />

As an obvious next step, it is interesting to classify finite dimensi<strong>on</strong>al algebras <str<strong>on</strong>g>of</str<strong>on</strong>g> global<br />

dimensi<strong>on</strong> 2 or higher. Recently, Minamoto introduced a nice class <str<strong>on</strong>g>of</str<strong>on</strong>g> finite dimensi<strong>on</strong>al<br />

algebras <str<strong>on</strong>g>of</str<strong>on</strong>g> finite global dimensi<strong>on</strong>, called (quasi-)Fano algebras [2], which are a very<br />

interesting class <str<strong>on</strong>g>of</str<strong>on</strong>g> algebras to study <strong>and</strong> classify. It was shown that, for a graded Frobenius<br />

Koszul algebra A, we can define ano<str<strong>on</strong>g>the</str<strong>on</strong>g>r algebra ∇A, called <str<strong>on</strong>g>the</str<strong>on</strong>g> quantum Beilins<strong>on</strong><br />

algebra associated to A, <strong>and</strong> with some additi<strong>on</strong>al assumpti<strong>on</strong>s, ∇A turns out to be a<br />

quasi-Fano algebra. Moreover, it was shown that two graded Frobenius algebras A, A ′<br />

are graded Morita equivalent if <strong>and</strong> <strong>on</strong>ly if ∇A, ∇A ′ are isomorphic as algebras, so classifying<br />

graded Frobenius (Koszul) algebra up to graded Morita equivalence is related to<br />

classifying quasi-Fano algebras up to isomorphism (see [3] for details).<br />

In additi<strong>on</strong>, this problem is related to <str<strong>on</strong>g>the</str<strong>on</strong>g> study <str<strong>on</strong>g>of</str<strong>on</strong>g> AS-regular algebras which are <str<strong>on</strong>g>the</str<strong>on</strong>g><br />

most important class <str<strong>on</strong>g>of</str<strong>on</strong>g> algebras in n<strong>on</strong>commutative algebraic geometry (see [8]).<br />

Our main <str<strong>on</strong>g>the</str<strong>on</strong>g>orem (Theorem 9) is as follows. For every co-geometric Frobenius Koszul<br />

algebra A, we define ano<str<strong>on</strong>g>the</str<strong>on</strong>g>r graded algebra A, <strong>and</strong> see that if two co-geometric Frobenius<br />

Koszul algebras A, A ′ are graded Morita equivalent, <str<strong>on</strong>g>the</str<strong>on</strong>g>n A, A ′ are isomorphic as graded<br />

algebras. Unfortunately, <str<strong>on</strong>g>the</str<strong>on</strong>g> c<strong>on</strong>verse does not hold in general. On <str<strong>on</strong>g>the</str<strong>on</strong>g> o<str<strong>on</strong>g>the</str<strong>on</strong>g>r h<strong>and</strong>,<br />

<str<strong>on</strong>g>the</str<strong>on</strong>g> c<strong>on</strong>verse is also true for many co-geometric Frobenius Koszul algebras <str<strong>on</strong>g>of</str<strong>on</strong>g> Gorenstein<br />

parameter −3.<br />

The detailed versi<strong>on</strong> <str<strong>on</strong>g>of</str<strong>on</strong>g> this paper will be submitted for publicati<strong>on</strong> elsewhere.<br />

–216–

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