Applications of algebra to a problem in topology - by Michael Hopkins

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Michael Hopkins' slides accompanying his University of Oxford lecture on topology in mathematics, specifically on work behind the solving the Kervaire Invariant.

Transcript of Applications of algebra to a problem in topology - by Michael Hopkins

Applications of algebra to a problem in topology

Tuesday, April 21, 2009

Joint work with

Mike Hill

and

Doug Ravenel

Tuesday, April 21, 2009

Pontryagin (1930’s)

Tuesday, April 21, 2009

Pontryagin (1930’s)

cobordism group of stably framed k-manifolds

Tuesday, April 21, 2009

Pontryagin (1930’s)

k=0

k=1

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Pontryagin (1930s) k=2

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Pontryagin (1930s) k=2

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Pontryagin (1930s) k=2

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Pontryagin (1930s) This defines a fuction

If genus , and so

You can always lower the genus with surgery

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Pontryagin (?)

it’s quadratic and refines the intersection pairing

is not linear

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Pontryagin (?)

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Kervaire (1960)(framed)

defined

showed

quadratic refinement of the intersection pairing

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produced a piecewise linear

Kervaire (1960)

with

has no smooth structurehence

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represented bythere exists

Browder (1969)

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Barratt-Jones-Mahowald (1969, 1984)

so the first open dimension is 126

The elements exist

for

dimensions

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The Kervaire invariant problem

In which dimensions can

be non-zero?

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Doomsday Theorem (Hill, H., Ravenel)

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Adams SpectralSequence

Adams-NovikovSpectral Sequence

Something easierto compute

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Tuesday, April 21, 2009

Adams SpectralSequence

Adams-NovikovSpectral Sequence

Something easierto compute

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Tuesday, April 21, 2009

Tuesday, April 21, 2009

supports afornon-zero differential

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Adams SpectralSequence

Adams-NovikovSpectral Sequence

Something easierto compute

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Tuesday, April 21, 2009

Rochlin’s Theorem

periodicity Theorem

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K-theory and reality (Atiyah, 1966)

space with a action

vector bundles with compatible conjugate-

linear action

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Assemble K-theory from the equivariant

chains on

slice filtration(Dugger, Hu-Kriz, H.-Morel, Voevodsky)

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slice filtration

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periodicity

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periodicity

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level 5 topological modular forms

Like with instead of

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32

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32

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the period2 below the period

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the period2 below the period

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Assemble tmf(5) from the equivariant chains

on

slice filtration

the 4 dimensional real regular representation of

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0-2

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the period2 below the period

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gap + periodicity

differentials on the

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The actual proof

Show that all the choices of are distinguished

Step 2:

Prove a gap theorem (easy)Step 3:

Use and an appropriateStep 1:cohomology theory

Prove a periodicity theorem (of period 256)Step 4:

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Relation to Geometry/Physics?

4 dimensional field theory?

generalization of Clifford algebras with periodicity of

(maybe twice that)

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Question

Tuesday, April 21, 2009