Homological algebra in subcategories:Nakayama functors, rank functions and differential modules
Bibliographic record
Abstract
This thesis explores aspects of homological algebra within subcategories. It comprises of three papers, each in its own chapter. In Chapter I, we investigate the homological algebra of proper abelian subcategories within a triangulated category equipped with a Serre functor. By approximating the Serre functor, we construct Nakayama functors, which in turn enable the definition of the Auslander-Reiten translations. We show that suitable proper abelian subcategories are dualising k-varieties and have enough projectives if and only if they have enough injectives. This framework yields a new proof for the existence of Auslander-Reiten sequences in the category of finite dimensional modules over a finite dimensional algebra. Chapter II introduces a theory of rank functions on (d+2)-angulated categories, generalising the notion of rank function on triangulated categories introduced by Chuang and Lazarev. We establish a bijective correspondence between object-defined and morphismdefined rank functions. Inspired by work of Conde, Gorsky, Marks and Zvonareva, we further demonstrate a bijective correspondence between rank functions on an Amiot-Lin (d+2)-angulated categories and certain additive functions on its associated module category. This leads to a decomposition theorem: integral rank functions admit a factorisation into irreducible components in this setting. Chapter III studies the homological theory of differential modules via the Q-shaped derived category introduced by Holm and Jørgensen. We prove a differential module analogue of a classical result characterising when a finitely generated module over a local commutative noetherian ring has finite injective dimension. As an application, we provide a new characterisation of local Cohen-Macaulay rings using differential modules, offering an alternative perspective on a question originally posed by Bass.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.002 |
| Scholarly communication | 0.002 | 0.004 |
| Open science | 0.001 | 0.002 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.004 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".