arXiv subjects
Publications and source records attributed to Alpesh M. Dhorajia.
In this paper we prove that if $R$ is a commutative, reduced, local ring, then $R$ is Hopfian if and only if the ring $R[x]$ is Hopfian. This answers a question of Varadarajan, in the case when $R$ is a reduced local ring. We provide examples of non-Noetherian Hopfian commutative domains by proving that the finite dimensional domains are Hopfian. Also, we derive some general results related to Hopfian rings.
Let $A$ be a ring of dimension $d$. Assume that for every finite extension ring $R$ of $A$, E_{d+1}(R) acts transitively on Um_{d+1}(R). Then we prove that E(A\oplus P) acts transitively on Um(A\oplus P), for any projective A-module P of rank d. As a consequence of this, we generalise some results of Gubeladze.
Let A be a commutative Noetherian ring of dimension d and let P be a projective R=A[X_1,\ldots,X_l,Y_1,\ldots,Y_m,\frac {1}{f_1\ldots f_m}]-module of rank r\geq max {2,dim A+1, where f_i\in A[Y_i]. Then (i) \EL^1(R\op P) acts transitively on Um(R\oplus P). In particular, P is cancellative. (ii) If A is an affine algebra over a field, then P has a unimodular element. (iii) The natural map Φ_r : GL_r(R)/EL^1_r(R) \ra K_1(R) is surjective. (iv) Assume f_i is a monic polynomial. Then Φ_{r+1} is an isomorphism. In the case of Laurent polynomial ring (i.e. f_i=Y_i), (i) is due to Lindel, (ii) is due to Bhatwadekar, Lindel and Rao and (iii, iv) is due to Suslin.