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Thesis. 1975. Ph.D.--Massachusetts Institute of Technology. Dept. of Mathematics. / Includes bibliographical references. / Ph.D.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Mathematics, 1981. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Bibliography: leaves 79-81. / by Ranee Kathryn Gupta. / Ph.D.

It is well-known that del Pezzo surfaces of degree 9 -- n. are in one-to-one correspondence to flat En bundles over elliptic curves which are anti-canonical curves of such surfaces. In my thesis, we study a broader class of rational surfaces which are called ADE surfaces. We construct Lie algebra bundles of any type on these surfaces, and extend the above correspondence to flat G bundles over elliptic curves, where G is a simple, compact and simply-connected Lie group of any type. Concretely, we establish a natural identification between the following two very different moduli spaces for a Lie group G of any type: the moduli space of rational surfaces with G-configurations and the moduli space of flat G-bundles over a fixed elliptic curve. / Zhang, Jiajin. / "July 2007." / Adviser: Leung Nai Chung Conan. / Source: Dissertation Abstracts International, Volume: 69-01, Section: B, page: 0357. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (p. 77-79). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.

Muhly and Solel developed a notion of Morita equivalence for C*- correspondences, which they used to show that if two C*-correspondences E and F are Morita equivalent then their tensor algebras $\mathcal{T}_{+}(E)$ and $\mathcal{T}_{+}(F)$ are (strongly) Morita equivalent operator algebras. We give the weak* version of this result by considering (weak) Morita equivalence of W*-correspondences and employing Blecher and Kashyap's notion of Morita equivalence for dual operator algebras. More precisely, we show that weak Morita equivalence of W*-correspondences E and F implies weak Morita equivalence of their Hardy algebras $H^{\infty}(E)$ and $H^{\infty}(F)$. We give special attention to W*-graph correspondences and show a number of results related to their Morita equivalence. We study how different representations of a W*-algebra give rise to Morita equivalent objects. For example, we show that if (E,A) is a W*-graph correspondence and we have two faithful normal representations $\sigma$ and $\tau$ of A, then the commutants of the induced representions $\sigma ^{\ms{F}(E)}(H^{\infty}(E))$ and $\tau ^{\ms{F}(E)}(H^{\infty}(E))$ are weakly Morita equivalent dual operator algebras. We also develop a categorical approach to Morita equivalence of W*- correspondences. This involves building categories of covariant representations and studying the groups $Aut(\mathbb{D}({(E^{\sigma}})^*)$ and $Aut(H^{\infty}(E))$ (the automorphism groups of the unit ball of intertwiners and the Hardy algebra). In this regard, we advance the work of Muhly and Solel by showing new results about these groups, their matrix representation and their algebraic properties.

<p>We show that, over an artin algebra, the tilting functor preserves (co)tilting modules in the subcategories associated to the functor. We also give a sufficient condition for the category of modules of finite projective dimension over an artin algebra to be contravariantly finite in the category of all finitely generated modules over the artin algebra. This is a sufficient condition for the finitistic dimension of the artin algebra to be finite [3].</p><p>We also develop relative theory and in certain subcategories of the module category over an artin algebra in the sense of [10,11]. We use the theory to generalize the main result of [26]</p>

The Drinfel’d Lagrangian Grassmannian compactifies the space of algebraic maps of fixed degree from the projective line into the Lagrangian Grassmannian. It has a natural projective embedding arising from the highest weight embedding of the ordinary Lagrangian Grassmannian, and one may study its defining ideal in this embedding.The Drinfel’d Lagrangian Grassmannian is singular. However, a concrete description of generators for the defining ideal of the Schubert subvarieties of the Drinfel’d Lagrangian Grassmannian would implythat the singularities are modest. I prove that the defining ideal of any Schubert subvariety is generated by polynomials which give a straightening law on an ordered set. Using this fact, I show that any such subvariety is Cohen-Macaulay and Koszul. These results represent a partial extension of standard monomial theory to the Drinfel’d Lagrangian Grassmannian.

Our work goes in two directions. At first we want to transfer definitions, concepts and results of the theory of hyperidentities and solid varieties from the total to the partial case. (1) We prove that the operators chi^A_RNF and chi^E_RNF are only monotone and additive and we show that the sets of all fixed points of these operators are characterized only by three instead of four equivalent conditions for the case of closure operators. (2) We prove that V is n − SF-solid iff clone^SF V is free with respect to itself, freely generated by the independent set {[fi(x_1, . . . / x_n)]Id^SF_n V | i in I}. (3) We prove that if V is n-fluid and ~V |P(V ) =~V −iso |P(V ) then V is kunsolid for k >= n (where P(V ) is the set of all V -proper hypersubstitutions of type tau ). (4) We prove that a strong M-hyperquasi-equational theory is characterized by four equivalent conditions. The second direction of our work is to follow ideas which are typical for the partial case. (1) We characterize all minimal partial clones which are strongly solidifyable. (2)We define the operator Chi^A_Ph where Ph is a monoid of regular partial hypersubstitutions.Using this concept, we define the concept of a Phyp_R(tau )-solid strong regular variety of partial algebras and we prove that a PHyp_R(tau )-solid strong regular variety satisfies four equivalent conditions.

We show that, over an artin algebra, the tilting functor preserves (co)tilting modules in the subcategories associated to the functor. We also give a sufficient condition for the category of modules of finite projective dimension over an artin algebra to be contravariantly finite in the category of all finitely generated modules over the artin algebra. This is a sufficient condition for the finitistic dimension of the artin algebra to be finite [3]. We also develop relative theory and in certain subcategories of the module category over an artin algebra in the sense of [10,11]. We use the theory to generalize the main result of [26]

In this thesis, it is proposed to examine the difference equation:(z-h) ∆-hW(z) = A(z)W(z)(1) where W(z) is a vector with two components,∆-hW(h) = W(z) – W(z-h)/h(2)Here, A(z) is a 2x2 matrix, whose elements admit factorial series representations:A (z) = R + Σ∞s=0 As+1S!/z(z+h) ••• (z+sh)(3)R and As+l are square matrices of order two and independent of z. We also assume that eigen values of R do not differ by an integer. We hope to show that if (3) converges in some half plane, then (1) will have a fundamental matris solution of the form: W(z) = S(z)ZR where S(z) is a 2x2 matrix, whose elements have convergent factorial representation in some half plane.