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Bers isomorphism on the universal Teichmüller curve  [PDF]
Lee-Peng Teo
Mathematics , 2006,
Abstract: We study the Bers isomorphism between the Teichm\"uller space of the parabolic cyclic group and the universal Teichm\"uller curve. We prove that this is a group isomorphism and its derivative map gives a remarkable relation between Fourier coefficients of cusp forms and Fourier coefficients of vector fields on the unit circle. We generalize the Takhtajan-Zograf metric to the Teichm\"uller space of the parabolic cyclic group, and prove that up to a constant, it coincides with the pull back of the Velling-Kirillov metric defined on the universal Teichm\"uller curve via the Bers isomorphism.
Higher Bers maps  [PDF]
Guy Buss
Mathematics , 2008,
Abstract: The Bers embebbing realizes the Teichm\"uller space of a Fuchsian group $G$ as a open, bounded and contractible subset of the complex Banach space of bounded quadratic differentials for $G$. It utilizes the schlicht model of Teichm\"uller space, where each point is represented by an injective holomorphic function on the disc, and the map is constructed via the Schwarzian differential operator. In this paper we prove that a certain class of differential operators acting on functions of the disc induce holomorphic mappings of Teichm\"uller spaces, and we also obtain a general formula for the differential of the induced mappings at the origin. The main focus of this work, however, is on two particular series of such mappings, dubbed higher Bers maps, because they are induced by so-called higher Schwarzians -- generalizations of the classical Schwarzian operator. For these maps, we prove several further results. The last section contains a discussion of possible applications, open questions and speculations.
Natural Isomorphism from a Linear Map's Image to Complement of Nullspace  [PDF]
H. N. Friedel
Mathematics , 2011,
Abstract: There is a natural isomorphism from image to complement of nullspace, for a bounded linear map from a real Banach space onto a closed subspace of a real Hilbert space. This generalizes Riesz representation (self-duality of Hilbert space). The isomorphism helps solve the pressure equation of fluid dynamics.
Thom isomorphism and Push-forward map in twisted K-theory  [PDF]
Alan L. Carey,Bai-Ling Wang
Mathematics , 2005,
Abstract: We establish the Thom isomorphism in twisted K-theory for any real vector bundle and develop the push-forward map in twisted K-theory for any differentiable proper map $f: X\to Y$ (not necessarily K-oriented). The push-forward map generalizes the push-forward map in ordinary K-theory for any $K$-oriented differentiable proper map and the Atiyah-Singer index theorem of Dirac operators on Clifford modules. For $D$-branes satisfying Freed-Witten's anomaly cancellation condition in a manifold with a non-trivial $B$-field, we associate a canonical element in the twisted K-group to get the so-called D-brane charges.
On meromorphic extendibility  [PDF]
Josip Globevnik
Mathematics , 2008,
Abstract: Let D be a bounded domain in the complex plane whose boundary bD consists of finitely many pairwise disjoint real analytic simple closed curves. Let f be an integrable function on bD. In the paper we show how to compute the candidates for poles of a meromorphic extension of f through D and thus reduce the question of meromorphic extendibility to the question of holomorphic extendibility. Let A(D) be the algebra of all continuous functions on the closure of D which are holomorphic on D. For continuous functions f on bD we obtain a characterization of meromorphic extendibility in terms of the argument principle: f extends meromorphically through D if and only if there is a nonnegative integer N such that the winding number of Pf+Q along bD is bounded below by -N for all P, Q in A(D) such that Pf+Q has no zero on bD. If this is the case then the meromorphic extension of f has at most N poles in D, counting multiplicity.
Bers slices are Zariski dense  [PDF]
David Dumas,Richard P. Kent IV
Mathematics , 2008, DOI: 10.1112/jtopol/jtp014
Abstract: We prove that every Bers slice of quasi-Fuchsian space is Zariski dense in the character variety.
On the extendibility of the Diophantine triple
Fadwa S. Abu Muriefah,Amal Al-Rashed
International Journal of Mathematics and Mathematical Sciences , 2004, DOI: 10.1155/s0161171204305181
Abstract: We study the problem of extendibility of the triples of the form {1,5,c}. We prove that if ck=sk2
The Bers-Greenberg Theorem and the Maskit Embedding for Teichmüller spaces  [PDF]
Pablo Ares-Gastesi
Mathematics , 1995,
Abstract: The Bers-Greenberg theorem tells that the Teichm\"{u}ller space of a Riemann surface with branch points (orbifold) depends only on the genus and the number of special points, but not on the particular ramification values. On the other hand, the Maskit embedding provides a mapping from the Teichm\"{u}ller space of an orbifold, into the product of one dimensional Teichm\"{u}ller spaces. In this paper we prove that there is a set of isomorphisms between one dimensional Teichm\"{u}ller spaces that, when restricted to the image of the Teichm\"{u}ller space of an orbifold under the Maskit embedding, provides the Bers-Greenberg isomorphism.
Graph Isomorphism for Graph Classes Characterized by two Forbidden Induced Subgraphs  [PDF]
Stefan Kratsch,Pascal Schweitzer
Computer Science , 2012,
Abstract: We study the complexity of the Graph Isomorphism problem on graph classes that are characterized by a finite number of forbidden induced subgraphs, focusing mostly on the case of two forbidden subgraphs. We show hardness results and develop techniques for the structural analysis of such graph classes, which applied to the case of two forbidden subgraphs give the following results: A dichotomy into isomorphism complete and polynomial-time solvable graph classes for all but finitely many cases, whenever neither of the forbidden graphs is a clique, a pan, or a complement of these graphs. Further reducing the remaining open cases we show that (with respect to graph isomorphism) forbidding a pan is equivalent to forbidding a clique of size three.
Isomorphism classes of association schemes induced by Hadamard matrices  [PDF]
Mitsugu Hirasaka,Kijung Kim,Hyonju Yu
Mathematics , 2014,
Abstract: Every Hadamard matrix $H$ of order $n > 1$ induces a graph with $4n$ vertices, called the Hadamard graph $\Gamma(H)$ of $H$. Since $\Gamma(H)$ is a distance-regular graph with diameter $4$, it induces a $4$-class association scheme $(\Omega, S)$ of order $4n$. In this article we deal with fission schemes of $(\Omega, S)$ under certain conditions, and for such a fission scheme we estimate the number of isomorphism classes with the same intersection numbers as the fission scheme.
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