<p>Let <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(\Sigma _b\)</EquationSource> </InlineEquation> be a compact Riemann surface of genus <i>b</i>. We investigate finite quotients <i>G</i> of the pure braid group on two strands <InlineEquation ID="IEq2"> <EquationSource Format="TEX">\(\textsf{P}_2(\Sigma _b)\)</EquationSource> </InlineEquation> which do not factor through <InlineEquation ID="IEq3"> <EquationSource Format="TEX">\(\pi _1(\Sigma _b \times \Sigma _b)\)</EquationSource> </InlineEquation>. Building on our previous work on some special systems of generators on finite groups that we called <i>diagonal double Kodaira structures</i>, we prove that, if <i>G</i> does not have order 32, then <InlineEquation ID="IEq4"> <EquationSource Format="TEX">\(|G| \ge 64\)</EquationSource> </InlineEquation>, and we completely classify the cases where <InlineEquation ID="IEq5"> <EquationSource Format="TEX">\(b=2\)</EquationSource> </InlineEquation> and equality holds. In the last section, as a geometric application of our algebraic results, we construct two 3-dimensional families of double Kodaira fibrations having the same biregular invariants and the same Betti numbers but different fundamental group.</p>

错误:搜索内容不能为空,请输入英文关键词
错误:关键词超出字数限制,请精简
高级检索

Groups of order 64 and non-homeomorphic double Kodaira fibrations with the same biregular invariants

  • Francesco Polizzi,
  • Pietro Sabatino

摘要

Let \(\Sigma _b\) be a compact Riemann surface of genus b. We investigate finite quotients G of the pure braid group on two strands \(\textsf{P}_2(\Sigma _b)\) which do not factor through \(\pi _1(\Sigma _b \times \Sigma _b)\) . Building on our previous work on some special systems of generators on finite groups that we called diagonal double Kodaira structures, we prove that, if G does not have order 32, then \(|G| \ge 64\) , and we completely classify the cases where \(b=2\) and equality holds. In the last section, as a geometric application of our algebraic results, we construct two 3-dimensional families of double Kodaira fibrations having the same biregular invariants and the same Betti numbers but different fundamental group.