Bonn THDM 2013: Program
Contents |
1 Introduction
1.1 K0 and Wall's finiteness obstruction
Speaker: WL
Abstract: We introduce the projective class group . We explain computations for special rings, e.g., fields, complex group rings for finite groups. We state Swan's Theorem which relates the projective class group of the ring of continuous -valued functions to the Grothendieck group of vector bundles over , if is a finite -complex. We discuss Wall's finiteness obstruction which decides whether a finitely dominated -complex is homotopy equivalent to a finite -complex and takes values in the projective class group of the integral group ring of the fundamental group.
Exercises: K-group, zeroth (Ex), Finitely dominated CW complexes (Ex).
References: [Lück1987], [Lück1989], [Mislin1995], [Ranicki1985], [Rosenberg1994], [Wall1965a], [Wall1966b].
1.2 K1 and Whitehead torsion
Speaker: WL
Abstract: We introduce and the Whitehead group . We define the Whitehead torsion of a homotopy equivalence of finite connected -complexes. We discuss the algebraic and topological significance of these notions, in particular the -cobordism theorem. We briefly introduce the surgery program. Finally we introduce negative -theory and the Bass-Heller-Swan decomposition.
Exercises: K-group, first (Ex), Whitehead torsion (Ex), Reidemeister torsion (Ex), K-group, all (Ex).
References: [Cohen1973], [Lück1989], [Lück2002], [Milnor1966], [Ranicki1985a], [Ranicki1987], [Rosenberg1994].
1.3 Normal maps and surgery below the middle dimension
Speaker: SA-F
Abstract:
Exercises:
References:
1.4 L-groups
Speaker: SA-F
Abstract:
Exercises:
References:
1.5 Surgery in the middle dimension
Speaker: SA-F
Abstract:
Exercises:
References:
1.6 The geometric surgery exact sequence
Speaker: SA-F
Abstract:
Exercises:
References:
2 Surgery on smooth manifolds
2.1 Homotopy spheres and other examples
Speaker: DC
Abstract:
Exercises:
References:
2.2 Smoothing and surgery
Speaker: DC
Abstract:
Exercises:
References:
2.3 Classifying spaces for surgery
Speaker: DC
Abstract:
Exercises:
References:
2.4 The Kervaire invariant in surgery
Speaker: DC
Abstract:
Exercises:
References:
3 Algebraic L-theory
3.1 L-groups via chain complexes
Speaker: TM
Abstract: We introduce symmetric and quadratic structures on chain complexes which are analogues of symmetric and quadratic forms on modules. A non-degeneracy condition yields Poincaré complexes. Further we generalize to structures on chain maps obtaining the notion of a symmetric pair and a quadratic pair and a non-degeneracy assumption on these produces the notion of a cobordism of symmetric and quadratic Poincaré complexes. Cobordism classes then define the promised -groups. We introduce the technique of algebraic surgery which is the main tool in showing that the -groups defined via chain complexes agree with the -groups defined via forms and formations.
Exercises: Equivariant maps (Ex), Structured chain complexes (Ex), Structured chain complexes II (Ex), Structured chain complexes III (Ex).
References: [Ranicki1980], [Ranicki1980a], [Ranicki2002a], [Kühl&Macko&Mole2011], [Crowley&Lück&Macko2013, Chapter 8].
3.2 Signatures
Speaker: TM
Abstract: We first show that an -dimensional geometric Poincaré complex defines an -dimensional Poincaré symmetric structure on its singular chain complex. Its class in an appropriate -group is called the symmetric signature of that complex. Secondly we show that a degree one normal map between -dimensional geometric Poincaré complexes defines an -dimensional Poincaré quadratic structure on the mapping cone of the Umkehr map, again its class in an appropriate -group is called the quadratic signature of that map. To obtain it, we introduce the suspension of a symmetric complex and of a quadratic complex and using it we state a condition for refining symmetric structures to quadratic structures. We use -duality from stable homotopy theory to see that the condition is fulfilled for such a degree one normal map. In case our Poincaré complexes are manifolds the resulting complex represents the surgery obstruction in the -group.
Exercises: Structured chain complexes IV (Ex), Boundaries of symmetric complexes (Ex), S-duality III (Ex).
References: [Ranicki1980], [Ranicki1980a], [Ranicki2002a], [Kühl&Macko&Mole2011], [Crowley&Lück&Macko2013, Chapter 8] and [Browder1972, I §4] for S-duality; see also [Adams1974], [Switzer2002, Ch.14].
3.3 L-groups of categories and assembly maps
Speaker: TM
Abstract: We generalize the notions from the first two talks to complexes over an arbitrary additive category with chain duality. We define such a chain duality on the category of modules over a simplicial complex. This yields on one hand a construction of the -spectra. On the other hand imposing a certain local Poincaré condition produces homology of a space with coefficients in an -theory spectrum. Relaxing the local Poincaré duality to global Poincaré duality produces the assembly map.
Exercises:
References: [Ranicki1992], [Kühl&Macko&Mole2011].
3.4 Surgery obstructions and assembly maps
Speaker: TM
Abstract: We generalize the signatures from the second talk in the case when the Poincaré complexes are manifolds to signatures over the categories from the third talk. This produces a map (which turns out to be an isomorphism) from the geometric surgery exact sequence to the algebraic surgery exact sequence. This map identifies the surgery obstruction map with the assembly map.
Exercises: Chain duality I (Ex), Chain duality II (Ex), Chain duality III (Ex), Chain duality IV (Ex), Chain duality V (Ex), Chain duality VI (Ex).
References: [Ranicki1992], [Kühl&Macko&Mole2011].
4 The isomorphism conjectures
4.1 The Isomorphism Conjectures in the torsion-free case
Speaker :WL
Abstract: We introduce spectra and how they yield homology theories. We state the Farrell-Jones Conjecture and the Baum-Connes Conjecture for torsion free groups and discuss applications of these conjectures, such as the Kaplansky Conjecture and the Borel Conjecture. We explain that the formulations for torsion free groups cannot extend to arbitrary groups.
Exercises: Smash product (Ex), K-groups of oriented surface groups (Ex), Idempotents in group rings (Ex), Borel conjecture in dimensions 1 and 2 (Ex).
References: [Bartels&Lück&Reich2008], [Baum&Connes&Higson1994], [Farrell&Jones1993a], [Kreck&Lück2009], [Lück&Reich2006].
4.2 The Isomorphism Conjectures in general
Speaker: WL
Abstract: We introduce classifying spaces for families. We define equivariant homology theories and explain how they can be construced by spectra over groupoids. Then we state the Farrell-Jones Conjecture and the Baum-Connes Conjecture in general. We discuss further applications, such as the Novikov Conjecture.
Exercises: Classifying spaces for proper group actions (Ex), Equivariant homology (Ex), K-group, zeroth II (Ex).
References: [Bartels&Lück&Reich2008], [Bartels&Lück&Weinberger2010], [Baum&Connes&Higson1994], [Kreck&Lück2005], [Lück2002a], [Lück2002b], [Lück2005], [Farrell&Jones1993a], [Lück&Reich2006].
4.3 Status and methods of proof;
Speaker: WL
Abstract: We give a status report of the Farrell-Jones Conjecture, discuss open cases and the search for potential counterexamples, and briefly survey the methods of proof.
References: [Bartels2012], [Bartels&Farrell&Lück2011], [Bartels&Lück2012], [Bartels&Lück&Reich2008a], [Bartels&Lück&Reich2008], [Bartels&Lück&Reich&Rueping2012], [Lück2008a].
5 References
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