What is the Homology Spectral Sequence for a Chain Complex with Filtration?

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  • Thread starter Euge
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    2015
In summary, the Homology Spectral Sequence is a mathematical tool used to calculate the homology groups of a chain complex with filtration. It involves constructing a filtration on the complex and arranging the homology groups of each subcomplex in a grid-like structure. This allows for the computation of difficult homology groups and provides insights into the complex's structure. However, it has limitations such as working best for finite filtration and requiring knowledge of algebraic topology and homological algebra.
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Euge
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Here is this week's POTW:

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Let $\mathcal{C} = \{C_n\}_{n\ge 0}$ be a chain complex. Compute the homology spectral sequence associated with the filtration $F_m := \sum_{n = 0}^m C_n$, $m\ge 0$.
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  • #2
No one answered this week's problem. You can read my solution below.
I'll let $d$ represent the differential of the chain complex. Since $E_n^0 \approx F_n/F_{n-1} \approx C_n$ and $d(F_n) \subseteq F_{n-1}$, then the map $d^0_n : F_n/F_{n-1} \to F_n/F_{n-1}$ is zero, $(E^0,E_n^0,d^0)$ is identified with $(\mathcal{C},C_n,0)$, and $E_n^1 \approx E_n^0 \approx C_n$. The map $d_n^1 : F_n/F_{n-1} \to F_{n-1}/F_{n-2}$ reduces to $d_n : C_n \to C_{n-1}$, and so $(E^1,E_n^1,d^1)$ is identified with $(\mathcal{C},C_n,d_n)$. We have $E_n^2 \approx H_n(\mathcal{C})$ and $d^2_n$ is zero, so $(E^2, E_n^2, d^2)$ is identified with $(H_*(\mathcal{C}), H_n(C), 0)$. All higher order $d^r$ are zero, $E_n^r \approx H_n(\mathcal{C})$ for $2 \le r < \infty$. Finally, $E_n^\infty \approx \sum_{m = 0}^n H_m(\mathcal{C})/\sum_{m = 0}^{n-1} H_m(\mathcal{C}) \approx H_n(\mathcal{C})$.
 

FAQ: What is the Homology Spectral Sequence for a Chain Complex with Filtration?

What is the Homology Spectral Sequence?

The Homology Spectral Sequence is a mathematical tool used to calculate the homology groups of a chain complex that has filtration. It is a way to break down the complex into smaller, more manageable pieces in order to compute the homology groups.

How is the Homology Spectral Sequence constructed?

The construction of the Homology Spectral Sequence involves first constructing a filtration on the chain complex, which is a sequence of subcomplexes that form a chain. Then, the spectral sequence is built by taking the homology groups of each subcomplex in the filtration and arranging them in a grid-like structure.

What is the purpose of using the Homology Spectral Sequence?

The Homology Spectral Sequence is useful because it allows for the calculation of homology groups of a complex with filtration, which can be difficult to compute directly. It also provides a way to analyze the structure of the complex and understand how the homology groups are related.

What information can be obtained from the Homology Spectral Sequence?

The Homology Spectral Sequence provides information about the homology groups of the chain complex, specifically how they are related to each other. It can also give insights into the structure of the complex and how the different filtration levels contribute to the overall homology groups.

Are there any limitations to using the Homology Spectral Sequence?

While the Homology Spectral Sequence is a powerful tool, it does have some limitations. It works best for chain complexes with finite filtration and may not provide accurate results for infinitely generated complexes. It also requires some knowledge of algebraic topology and homological algebra to understand and use effectively.

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