<p>In all dimensions <InlineEquation ID="IEq3"> <EquationSource Format="TEX">\(n \ge 5\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>n</mi> <mo>≥</mo> <mn>5</mn> </mrow> </math></EquationSource> </InlineEquation>, we prove the existence of closed orientable hyperbolic manifolds that do not admit any <InlineEquation ID="IEq4"> <EquationSource Format="TEX">\(\text {spin}^c\)</EquationSource> <EquationSource Format="MATHML"><math> <msup> <mtext>spin</mtext> <mi>c</mi> </msup> </math></EquationSource> </InlineEquation> structure, and in fact we show that there are infinitely many commensurability classes of such manifolds. These manifolds all have non-vanishing third Stiefel–Whitney class <InlineEquation ID="IEq5"> <EquationSource Format="TEX">\(w_3\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>w</mi> <mn>3</mn> </msub> </math></EquationSource> </InlineEquation> and are all arithmetic of simplest type. More generally, we show that for each <InlineEquation ID="IEq6"> <EquationSource Format="TEX">\(k \ge 1\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>k</mi> <mo>≥</mo> <mn>1</mn> </mrow> </math></EquationSource> </InlineEquation> and <InlineEquation ID="IEq7"> <EquationSource Format="TEX">\(n \ge 4k+1\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>n</mi> <mo>≥</mo> <mn>4</mn> <mi>k</mi> <mo>+</mo> <mn>1</mn> </mrow> </math></EquationSource> </InlineEquation>, there exist infinitely many commensurability classes of closed orientable hyperbolic <i>n</i>-manifolds <i>M</i> with <InlineEquation ID="IEq8"> <EquationSource Format="TEX">\(w_{4k-1}(M) \ne 0\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>w</mi> <mrow> <mn>4</mn> <mi>k</mi> <mo>-</mo> <mn>1</mn> </mrow> </msub> <mrow> <mo stretchy="false">(</mo> <mi>M</mi> <mo stretchy="false">)</mo> </mrow> <mo>≠</mo> <mn>0</mn> </mrow> </math></EquationSource> </InlineEquation>.</p>

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Closed hyperbolic manifolds without \(\text {spin}^c\) structures

  • Jacopo G. Chen

摘要

In all dimensions \(n \ge 5\) n 5 , we prove the existence of closed orientable hyperbolic manifolds that do not admit any \(\text {spin}^c\) spin c structure, and in fact we show that there are infinitely many commensurability classes of such manifolds. These manifolds all have non-vanishing third Stiefel–Whitney class \(w_3\) w 3 and are all arithmetic of simplest type. More generally, we show that for each \(k \ge 1\) k 1 and \(n \ge 4k+1\) n 4 k + 1 , there exist infinitely many commensurability classes of closed orientable hyperbolic n-manifolds M with \(w_{4k-1}(M) \ne 0\) w 4 k - 1 ( M ) 0 .