Algebras over variable theories

We will show that algebras over variable theories form a variety. This variety interprets the type Self of object oriented programming proposed by Abadi and Cardelli in [1]. Received February 14, 2000; accepted in final form April 5, 2001.     

Note on Magic Squares and Magic Cubes on Abelian Groups

ＮｏｔｅｏｎＭａｇｉｃＳｑｕａｒｅｓａｎｄＭａｇｉｃＣｕｂｅｓｏｎＡｂｅｌｉａｎＧｒｏｕｐｓＷｅｎＹｉｈｕｉ（ＧａｎｓｕＣｏｌｅｇｅｏｆＥｄｕｃａｔｉｏｎ）ＨｕｇｏＳｕｎ（ＣａｌｉｆｏｒｎｉａＳｔａｔｅＵｎｉｖｅｒｓｉｔｙ，Ｆｒｅｓｎｏ）Ａｂｓｔｒ...     

Factorization properties of birational mappings

We analyse birational mappings generated by transformations on q × q matrices which correspond respectively to two kinds of transformations: the matrix inversion and a permutation of the entries of the q × q matrix. Remarkable factorization properties emerge for quite general involutive permutations.

It is shown that factorization properties do exist, even for birational transformations associated with noninvolutive permutations of entries of q × q matrices, and even for more general transformation which are rational transformations but no longer birational. The existence of factorization relations independent of q, the size of the matrices, is underlined.

The relations between the polynomial growth of the complexity of the iterations, the existence of recursions in a single variable and the integrability of the mappings, are sketched for the permutations yielding these properties.

All these results show that permutations of the entries of the matrix yielding factorization properties are not so rare. In contrast, the occurrence of recursions in a single variable, or of the polynomial growth of the complexity are, of course, less frequent but not completely exceptional.     

Cycles on the generic abelian threefold

H Clemens and C Schoen gave examples of three-folds where the group of codimension two cycles modulo algebraic equivalence has infinite rank. This paper provides yet another example of the same phenomenon.     

Vector bundles over real algebraic varieties

The object of this paper is to study continuous vector bundles, over real algebraic varieties, admitting an algebraic structure. For large classes of real varieties, we obtain explicit information concerning the Grothendieck group of algebraic vector bundles. We show that in many cases this group is small compared to the corresponding group of continuous vector bundles. These results are used elsewhere to study the geometry of real algebraic varieties.Dedicated to Professor Alexander Grothendieck on the occasion of his 60th birthdaySupported by the NSF Grant DMS-8602672.     

On the dynamics and ergodic properties of theXY model

The return to equilibrium is investigated for one-dimensional (one-sided) chain of theXY model. The initial state is taken to be the Gibbs state for the sum of the Hamiltonian for theXY model of lengthN and a perturbation by a uniform magnetic field acting on the firstn sites. The time evolution under the unperturbedXY model Hamiltonian is studied for the expectation value of the average magnetization of the same firstn sites in the infinitely extended system (i.e., after taking the limitN). It is found that the return to equilibrium occurs for a finite-size perturbation (i.e., for a fixedn), while it does not occur for an infinite-size perturbation (i.e., the limit n is taken simultaneously as N). A certain twisted asymptotic Abelian property of theXY model is shown and used as a technical tool.     

Torsion in CH2 of Severi-Brauer varieties and indecomposability of generic algebras

We compute degrees of algebraic cycles on certain Severi-Brauer varieties and apply it to show that:

No-Go Theorem for ‘Free’ Relativistic Anyons in d=2+1

We show that a quantum field theoretic model of anyons cannot be free in the restrictive sense that the basic fields create only one-particle states out of the vacuum.