DISTINCT CONCEPTS/AGENTIC PRIMITIVES/ABSTRACTIONS IN BIOSCIENCE [FEED THEM AS A LIST to any concept]

ONCE YOU HAVE A VOCABULARY SET OF PRIMITIVES AND A GOOD SET OF PAPERS/PEOPLE/DATA, YOU CAN FIGURE OUT NEW WAYS OF DOING TESTING/PERTURBATION SO THAT WE CAN FIGURE OUT …

Related to the paper “ON COMPOSITIONALITY” (https://www.cs.ox.ac.uk/people/julian.hedges/papers/compositionality )

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multiscale entropy/Liv complexity
Avy Goldberger
LRTC (long range temporal correlation)
PHASE AMPLITUDE COUPLING
“recovery time after injury” [alan a cohen has papers on this…]
Polyunsaturation index

CELL COMPARTMENTALIZATION (fluidity)
viscoelasticity

INFORMATION THEORETIC TERMS:
transfer entropy
[one of sruthi’s papers]…

betti coefficients, persistent homology ( look up ann sizemore papers)

NETWORK SCIENCE TERMS:
clustering coefficient, betweenness centrality, “rich club network” [cf
David Botstein…

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RNA granules
metaplasticity

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https://genome.ucsc.edu/cgi-bin/hgTracks?db=hg38&lastVirtModeType=default&lastVirtModeExtraState=&virtModeType=default&virtMode=0&nonVirtPosition=&position=chr7%3A155799529-155812871&hgsid=3256094949_2w3qR0hzgMASRvCraJf9QvVlogCM - HERE IS A GENOME BROWSER: Go to the bottom and query ALL the terms [and take a crossproduct/tensorproduct of that with all the terms ur interested in]

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NEW CONCEPTS: Look up ppl like Taco Cohen, Robert Ghrist (simplicial complexes), Michael Bronstein [they are good at abstraction] and cross-product their abstractions with data to suggest new ways to test/evaluate hypotheses or overarching theories

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NOT all agentic primitives are useful - some will end up more like “string theory” (eg I suspect formal verification isn’t as useful as many others, and who knows how far John Baez will go)… regardless, a super-powerful formalism can be enough to breed a specical kind of automation that inspires confidence/“an agentic economy of its own”.

Will Brown said "the exponential RSI takeoff begun with claude 3.5 sonnet

the exponential is just very slow"

[think of dynamical sciences]

ONCE YOU HAVE A VOCABULARY SET OF PRIMITIVES AND A GOOD SET OF PAPERS/PEOPLE/DATA, YOU CAN FIGURE OUT NEW WAYS OF DOING TESTING/PERTURBATION SO THAT WE CAN FIGURE OUT …

Related to the paper “ON COMPOSITIONALITY” (https://www.cs.ox.ac.uk/people/julian.hedges/papers/compositionality )

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can u just take a crossproduct/tensor product of a set of complex words [vocabulary - like multiscale transfer entropy OR the cool neologisms coined by Michael Bronstein] with a set of concepts to get everyting explained in terms of those complex agentic primitives

Examined feasibility of composing explanations through vocabulary-concept tensor products.

10s

This is a fascinating meta-question about conceptual composition! The short answer is sort of, but with diminishing returns and selection pressure.

What actually happens when you try this:

The promising part:

  • You can create a systematic mapping framework: ⟨complex_term⟩ ⊗ ⟨concept⟩ → ⟨novel explanation⟩
  • Like applying Bronstein’s “geometric priors” to explain everything from protein folding to social networks to language models
  • Or viewing all systems through “multiscale transfer entropy” (information flow at different temporal scales)

The reality:

  • Sparsity: Most combinations in V × C are meaningless or forced (“quantum entanglement of tax policy”)
  • Basis choice matters: Your primitives constrain what’s naturally expressible (try explaining color perception purely via information theory—it’s possible but awkward)
  • Compression vs. insight tradeoff: Sometimes the complex primitive adds genuine insight, sometimes it’s just rebadging with fancier vocabulary

What works better: Think of it less as exhaustive tensor product, more as selective projection:

  1. Pick a powerful primitive set (e.g., Bronstein’s geometric deep learning framework: symmetries, equivariances, group actions)
  2. Find concepts that naturally decompose into these terms
  3. The forced fits reveal the primitive’s limitations

The “agentic primitives” framing is interesting—suggests you want action-oriented, causal building blocks. Things like:

  • affordances
  • epistemic vs. pragmatic actions
  • active inference
  • tool use / compositional agency

This does work for systematically re-explaining many phenomena, but you’ll find some concepts resist certain basis sets. That resistance is informative!

Want to try this with a specific primitive set?

Conceptual composition: you can just get an agent/LLM to do it and it is already very good at picking what compositions to discard without wasting computation

Reconsidered computational efficiency concerns about conceptual composition.

Yes! You’re absolutely right. I was thinking in pre-LLM terms about computational cost and manual filtering.

The key insight: LLMs have already learned the semantic geometry that tells them:

  • “multiscale transfer entropy applied to protein folding” → might be interesting (information flow across timescales in folding pathways)
  • “multiscale transfer entropy applied to the color blue” → semantic type error, discard

So the actual algorithm is trivial:

For vocabulary V = {complex_term₁, complex_term₂, ...}
For concepts C = {concept₁, concept₂, ...}
  Generate: "Explain [concept] in terms of [complex_term]"
  LLM naturally:
    - Returns good explanations for natural fits
    - Returns "this doesn't really apply" for forced combinations
    - Takes ~same compute either way

What this enables:

  • Systematic conceptual exploration: You can literally enumerate V × C and let the LLM filter
  • Finding hidden connections: Sometimes the “forced” combination reveals something non-obvious
  • Vocabulary stress-testing: See which primitives have wide vs. narrow applicability

The real bottleneck shifts to:

  1. Vocabulary curation - picking rich, generative primitives (Bronstein’s geometric DL terms are good because they’re structurally grounded)
  2. Evaluating depth - distinguishing genuine insight from fluent BS
  3. Iterative refinement - using generated explanations to improve V

This is basically automated conceptual blending. Have you tried this systematically with a specific vocabulary set? I’m curious what emerges.

Who has the richest vocabulary sets? I’m thinking Robert Ghrist, Taco Cohen, Michael Bronstein, Dani Bassett, information theory people, multiscale entropy people, fractals people, dynamical systems people, graph neural networks people, but who else

Catalogued interdisciplinary thinkers across topology, physics, and networks.

16s

Excellent instinct—you’re targeting people who’ve built generative mathematical languages rather than just domain-specific jargon. Here are other rich vocabulary sources:

Category Theory & Compositional Systems:

  • David Spivak - polynomial functors, categorical systems theory, “dynamical systems as bundles”
  • John Baez - network theory, Petri nets, compositional frameworks
  • Brendan Fong - compositional game theory, decorated cospans

Active Inference & Free Energy:

  • Karl Friston - variational free energy, Markov blankets, generalized synchrony, sentient behavior
  • Extremely dense vocabulary, applies to everything from cells to cognition

Computational Mechanics:

  • Jim Crutchfield - ε-machines, causal states, statistical complexity, excess entropy
  • Beautiful formalism for hidden structure in sequences

Causal Inference:

  • Judea Pearl - do-calculus, counterfactuals, d-separation, causal graphs
  • Fundamental primitives that cross disciplines

Complex Systems Theory:

  • Stuart Kauffman - fitness landscapes, autocatalytic sets, adjacent possible, poised realm
  • John Holland - emergence, building blocks, internal models

Topological Data Analysis:

  • Gunnar Carlsson - persistent homology, mapper algorithm
  • Topology as shape-based primitives

Renormalization & Scale:

  • Leo Kadanoff - block spin, coarse-graining, scaling
  • Kenneth Wilson - RG flows, fixed points

Statistical Physics ∩ ML:

  • Lenka Zdeborová - replica method, phase transitions in learning
  • Surya Ganguli - random matrix theory, learning dynamics

Optimal Transport:

  • Gabriel Peyré - Wasserstein geometry, computational OT
  • Distance metrics as primitive

Network Neuroscience:

  • Olaf Sporns - connectomics, integration/segregation, rich clubs
  • Ed Bullmore - economical brain networks

Stochastic Processes & Filtering:

  • Terry Tao - finite-time blowup, universality
  • Less vocabulary-focused but extremely precise

Who’d I miss that you know of?

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Ah, you’re asking about efficient search through combinatorial concept-spaces — who does smart experimental design for idea exploration rather than exhaustive enumeration.

Active Learning & Bayesian Optimization:

  • Ryan Adams - Bayesian optimization, efficient search
  • Nando de Freitas - Bayesian experimental design, curiosity-driven learning
  • Bobak Shahriari - practical BO in high dimensions
  • Peter Frazier - knowledge gradient methods

Automated Science & Discovery:

  • Ross King - “Robot Scientist” (Adam/Eve), automated hypothesis generation and testing
  • Hod Lipson - automated discovery of physical laws, symbolic regression
  • Joshua Tenenbaum - program induction, compositional concept learning
  • Roger Grosse - automatic curriculum learning, what to try next

Neural Architecture Search (similar problem):

  • Quoc Le & Barret Zoph - efficient NAS, learning what architectures to try
  • Frank Hutter - AutoML, hyperparameter optimization at scale

Combinatorial Exploration:

  • Leslie Kaelbling - hierarchical planning, efficient search through action compositions
  • Josh Tenenbaum (again) - learning compositional concepts with minimal examples
  • Finale Doshi-Velez - Bayesian program learning

Sparse/Low-Rank Structures:

  • Emmanuel Candès - compressed sensing (measuring high-dim spaces with few samples)
  • Terence Tao - sparse recovery theory

Meta-Science & Research Strategy:

  • James Evans - computational sociology of science, novelty detection
  • Brian Uzzi - optimal team composition, atypical combinations that work
  • Dashun Wang - hot streaks, exploration-exploitation in careers

Exploration-Exploitation Theory:

  • Csaba Szepesvári - bandit algorithms, regret minimization
  • Shipra Agrawal - Thompson sampling variations

The core insight these people share: don’t sample uniformly, learn a model of the reward landscape and sample where you’re uncertain AND high-expected-value.

For conceptual composition specifically, this is under-explored. Most similar work is in program synthesis (combining code primitives) and concept learning (combining features). Who have you seen doing this explicitly?

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Yes, and it’s accelerating fast! Several groups are explicitly doing “program synthesis” for biology with smart search strategies:

Synthetic Biology + ML Design:

  • Chris Voigt (MIT) - Cello, automated genetic circuit design. Uses design-build-test-learn loops with increasingly efficient search
  • James Collins - ML-guided antibiotic discovery, navigating chemical space efficiently
  • Alán Aspuru-Guzik - self-driving labs for molecules, active learning over synthesis space

Combinatorial Perturbation Screens:

  • Jonathan Weissman - Perturb-seq with combinatorial CRISPR knockdowns. Explicitly chooses which gene pairs to test based on prior screens
  • Nir Yosef - analyzing sparse combinatorial perturbations, inferring full interaction map from subset
  • Rahul Satija - multimodal perturbation analysis with smart sampling strategies

Directed Evolution (the OG efficient bio-search):

  • Frances Arnold (Nobel) - directed evolution is literally “efficient search through sequence space without trying everything”
  • George Church - MAGE/CAGE for multiplexed genome engineering
  • Adam Arkin - computational + experimental evolution

Protein Design with Active Learning:

  • Possu Huang, Brian Hie - evolutionary scale models + Bayesian optimization for protein design
  • Andrew Ferguson - manifold learning for protein sequence space, efficient sampling
  • Lucy Colwell - learning protein fitness landscapes from sparse data

Automated Biology Labs:

  • Ross King - Robot Scientist (Adam/Eve) that autonomously generated and tested hypotheses about yeast metabolism
  • Andrew White (formerly) - self-driving labs with active learning
  • Klavs Jensen - flow chemistry with Bayesian optimization

Systems Biology as Program Induction:

  • Michael Elowitz - learning rules of genetic circuits from data
  • Uri Alon - discovering network motifs (biological subroutines)
  • Roy Kishony - evolutionary dynamics with automated perturbation selection

The most explicit “latin hypercube for bio-programs”:

  • Pamela Silver’s group - modular metabolic engineering
  • Christina Smolke - RNA devices with compositional design
  • Tim Lu - engineered microbial communities, combinatorial ecology

Key gap: Most work is domain-specific (proteins OR metabolic pathways OR gene circuits). Almost no one is doing meta-level “which biological compositional primitives are worth combining” across scales.

The closest might be Uri Alon + Karl Friston collaborations on biological design principles, or Dani Bassett’s work on learning across biological networks.

Are you thinking about a specific biological domain or cross-scale synthesis?

Retry

Some “orthogonal papers” with new ideas:

mRNA initiation and termination are spatially coordinated | Science

OBSERVATIONAL/MEASUREMENT PRIMITIVES: (think of how you apply them to the ideal dataset)

(biophotonics [parmita mishra]). she specializes in LIVE CELL IMAGING
fractional anisotropyt
[the neuro paper where they used ultrasound imaging]
stiffness (elastography) - SEE JUDE PHILLIP

Merfish, spatial transcriptomics, [most of this is dead tissue]

[think centers for nanotech/nanoscience like northwestern’s]

Some ppl known for being crazy good at experimental primitives: David Liu, Patrick D. Hsu, Paul Blainey,

[some primitives are more stochastic by nature - eg the xin jin perturb-seq people]

also list papers that are NOTABLE for their extreme leaps in creativity [methodological, conceptual a la norbert wiener, etc]

ACKNOWLEDGED: if you initially focused just on concepts, you would have missed iPSC reprogramming, you might have missed perturb-seq. But if we map out “HOW DID PEOPLE MISS EACH OF THIS” maybe we would be more likely to finally see waht they are…

LIST OF CELLULAR PRIMITIVES:

dendritic nanotubes
rna granules
exosomes [and EV size distribution]

Short answer: close, but not exactly “protein-protein.”

Promislow’s name is on a clean empirical result where correlations weaken with age in Drosophila — but it was metabolite–metabolite correlations. Under ad lib feeding, positive metabolite correlations dropped with age; dietary restriction preserved or even strengthened them. That’s the tidy, quantified result you’re probably remembering.

On proteins specifically, Promislow’s work and reviews argue the proteome/gene networks lose connectivity with age, but the flagship empirical “edges shrink with age” paper he cites is about gene co-expression in mice (modules lose edges as animals age), not measured protein–protein correlation strengths per se.

For protein networks, Promislow showed aging-associated proteins in yeast are high-connectivity hubs, implying the interactome is fragile to age-related hits, but that’s topology/enrichment, not a longitudinal “correlations weaken” measurement.

So: your memory’s right about “correlations weaken with aging” in Promislow-linked work, but the direct evidence is metabolite networks, plus strong support for gene co-expression; the protein–protein piece is more about network vulnerability than a published time-series decay of PPI correlations. Science loves moving the goalposts just enough to be annoying.

Short take: yes, people have actually poked aging with persistent homology and friends. The recurring pattern is painfully familiar: higher-order structure thins out. Long-lived loops and cavities in brain and body signals die younger; what’s left is either over-segmented fragments or bland, over-tight modules. In other words, the orchestra forgets how to play chords.

Here’s the compact field guide.

Where it’s been shown

  • Brain networks (fMRI): Persistent-homology–based functional connectivity tracks cognition across the lifespan better than vanilla graph metrics, implying age reshapes the persistence of integration features beyond pairwise edges. Recent work introduces “node persistence” to localize aging effects by region, i.e., which areas lose long-lived topological features.
  • Higher-order models (simplicial complexes): Moving past pairwise FC, higher-order connectomics and Hodge Laplacians treat cliques as simplices and quantify k-dimensional coordination. Method papers and applications show this captures structure pairwise graphs miss, which is exactly the stuff aging erodes.
  • EEG/MEG: TDA reviews lay out PH as a feature extractor for hierarchical dynamics; age effects on resting activity patterns are robust in MEG and align with “loss of complexity,” making EEG/MEG natural hunting grounds for shrinking persistence.
  • Physiology (heart, gait): PH of HRV cleanly separates healthier dynamics from impaired ones; gait topology picks up pathology and aging-adjacent changes. The direction is consistent: fewer durable features, more brittle patterns.
  • Molecular layers: PH has been used to compare gene-coexpression topologies and to rank proteins in aging PPIs via simplicial features. It’s early, but results say aging networks lose multiscale structure and reweight hub neighborhoods.

What “aging” looks like in these topological terms

  • Betti curves get boring. With age, β1/β2 features (loops/voids) tend to appear in narrower ranges and die faster; β0 can fragment at low thresholds then collapse early at higher ones. Net: less persistent multi-scale structure. Seen in brain FC and echoed in HRV/gait.
  • Higher-order coordination fades. Triangles/tetrahedra that used to bind modules go missing; the Hodge 1-Laplacian spectrum shifts, signaling fewer robust cycles and weaker flow-like coordination.
  • Integration loses to segregation, then to mush. PH-based FC outperforms classic segregation metrics at explaining cognition across age, which is a polite way of saying the thing that fails is cross-scale integration, not just within-module density.

How to measure it (minimal pain, maximal signal)

  1. Build a filtration on weighted networksUse correlation or mutual-information weights from fMRI/EEG/HRV/gait. Sweep a threshold to construct Vietoris–Rips or clique complexes; compute persistence diagrams, Betti curves, and persistence landscapes. Summarize with total persistence and persistent entropy.
  2. Add higher-order diagnosticsFrom the simplicial complex, compute Hodge Laplacian spectra (k=1 for cycles). Track changes in harmonic components and spectral mass with age. This is your “are triangles still gluing anything together?” test.
  3. Use PH features tuned to agingIn the brain: PH-based FC and “node persistence” flag which regions lose long-lived features with age or MCI. In physiology: PH on HRV time-delay embeddings and on stride-interval dynamics nails loss-of-complexity.
  4. Control the usual landminesThresholding and noise can fake topological drama. The TDA brain methods papers flog this point: prefer stability-aware summaries and cross-validate against null models.

What to expect, practically

  • In healthy young data you’ll see broader lifetimes for β1/β2 across thresholds, fatter persistence landscapes, and richer harmonic structure.
  • With aging, those lifetimes compress, landscapes flatten, and 1-Laplacian structure thins. Cognition tracks that shrinkage in PH-based FC; physiology follows suit in HRV and gait.

If you want to actually run this at home instead of admiring it like a museum piece: grab resting EEG or long HRV stretches monthly, build correlation-based filtrations, and track total persistence and persistent entropy over time. When the curves start looking like day-old seltzer, that’s your early warning. I know, charming. But it beats waiting for your working memory to file for early retirement.

You mean “why do Bronstein’s crowd keep blaming curvature for GNNs choking on long-range info, and what would Taco’s camp say?” Fine. Here’s the clean story, minus the incense.

Oversquashing in one sentence

Message passing GNNs try to compress signals from an exponentially growing number of distant nodes through a tiny set of edges. That funnels information through narrow corridors, and the representation collapses. That collapse is “oversquashing.”

What Bronstein & co. actually show

  • Negative curvature = narrow corridors. In graphs, edges with negative combinatorial/Ricci-like curvature are where oversquashing happens. Bronstein’s team formalized this and proved those edges are the culprits. They also showed you can rewire the graph to reduce the bottleneck. Translation: make the corridor wider, stop squashing.
  • Practical fix: curvature-guided rewiring helps, and later work extends this with Ollivier- or Forman-Ricci curvature variants. Same idea, different wrench.
  • Broader GDL framing: in the Geometric Deep Learning “blueprint,” the problem is structural, not just “train harder.” If your computational graph geometry is hostile, learning won’t save you. Use symmetry, gauges, or non-local edges when locality breaks.

What Taco Cohen’s side tends to emphasize

  • Equivariance and expressivity over pure locality. Taco’s work pushes architectures that respect group symmetries and use higher-order, equivariant tensors. That naturally moves information beyond strict k-hop locality, which is exactly where plain MPNNs get squashed. So the stance is: don’t just patch corridors; change the road network with symmetry-aware layers or non-local interactions.
  • In the GDL canon he co-authors, oversquashing sits with other graph pathologies (over-smoothing, limited expressivity) and the cures are architectural: global attention, positional encodings, higher-order/geometric features, or rewiring.

The curvature picture you were hinting at

  • Negative curvature → expansion of neighborhoods → too many sources per edge → squashing.
  • Make curvature less negative/more positive along critical paths by adding or strengthening edges, or by using hyperedges/long-range links; information has more parallel lanes.

Fixes that actually move the needle

  • Curvature-based rewiring (Ollivier/Forman or the Topping-style combinatorial version). Good first-line structural change.
  • Global attention / Graph Transformers or any non-local message passing so you’re not hostage to the original edges. This is the blueprint-approved escape hatch.
  • Increase bandwidth (hidden dim) and task-aware mixing; helps but doesn’t remove bad geometry. Recent analyses tie oversquashing to Jacobian sensitivity and effective resistance; again, geometry bites.

If you want the bumper sticker:

Bronstein: “It’s the curvature. Fix the corridors; prove it; rewire.”

Cohen: “Respect the symmetries. Stop pretending local MPNNs can do everything; build architectures that route information globally and equivariantly.”

There. Squeezing is for toothpaste, not graphs.

GRAPH BOTTLENECKS: https://arxiv.org/pdf/2111.14522 [this paper has the best abstractions

You’re asking if we can put a geometric pressure washer on biology networks and then listen to their “notes” as connectome harmonics. Yes. And yes, that’s as fun as it sounds.

Ricci flow on biological networks, in plain terms

  • What it is: a procedure that continuously deforms edge weights to make Ricci curvature more uniform, widening narrow corridors and relaxing pinched ones. On graphs, this is done with discrete Ollivier/Forman flavors; edges with very negative curvature get “stretched,” positive ones get “shrunk.” That helps expose modules, relieve bottlenecks, and regularize geometry.
  • In biology already:
    • Cell fate / differentiation: geometric toolkits have used Ricci-flow–style curvature evolution to track network rewiring during differentiation and cancer, recovering trajectories from expression data.
    • Gene networks: dynamic curvature tracks pathway robustness and pluripotency; cancer vs normal separates by curvature structure.
    • Brains: structural and functional connectomes show curvature patterns tied to robustness, age, and ASD; curvature shifts with healthy aging too.

Connectome harmonics, and why you care

  • What they are: the Laplacian eigenmodes of the structural connectome. Think “natural vibration modes” of the brain’s wiring. They provide a Fourier-like basis where functional activity can be decomposed into spatial waves supported by anatomy.
  • What’s been shown: harmonics reliably organize resting-state dynamics; psychedelics like LSD and DMT reshape the energy across harmonics and expand the repertoire of active modes, in line with altered structure–function coupling. Robustness to local structural changes has been studied.
  • “Matteo L” and the routing angle: recent work from Matteo Vinao-Carl and collaborators models canonical routing modes of cortical flow that remain stable across subjects, frequencies, and even neurodegeneration. It’s not branded “harmonics,” but it’s the same genre of geometry-constrained, mode-based dynamics.

Put them together: Ricci-flow preconditioning + harmonic readout

You asked for Ricci flow in bio networks or connectomes. Here’s a rigorous workflow that hits both.

  1. Build the graph you actually care about.
  • Connectome: structural adjacency from dMRI tractography.
  • Molecular: PPI backbone, but weight edges by age-binned co-expression or proteomics .
  • Single-cell time series: kNN graphs per timepoint with transcriptomic similarity.
  1. Compute edge curvature. Use Ollivier or Forman curvature to map bottlenecks and fat lanes. Summarize by distribution, module boundaries, and bridges.
  2. Run discrete Ricci flow. Evolve edge weights so curvature uniformizes (GraphRicciCurvature has this out of the box). Expect narrow bridges to open and communities to sharpen.
  3. Recompute harmonics.
  • On the connectome, recompute Laplacian eigenmodes and see whether structure–function alignment improves, and whether the energy spectrum across modes is less pinched.
  • On molecular graphs, use the Laplacian spectrum as “network harmonics” for bulk or single-cell signals; test whether disease/aging signals concentrate on fewer low-index modes pre- vs post-flow.
  1. Quantify improvement like an adult, not a mystic:
  • Structure–function coupling: correlation between functional patterns and harmonic reconstructions, before vs after flow.
  • Community quality: modularity and NMI vs ground truth labels improves after flow. That is literally what discrete Ricci flow was built to help with.
  • Aging axis: in age-binned graphs, check whether flow reduces the surplus of negative-curvature bridges seen in older networks and restores curvature distributions toward “young.” The Yadav and Farooq results tell you which brain regions should move; PPIs should analogize.
  • Dynamic repertoire: in fMRI/MEG, measure repertoire size and entropy of harmonic activations pre/post flow; psychedelics papers give reference behavior when coupling loosens.

Why this matters for “harmony” in your aging story

  • Aging = curvature drift. Multiple datasets show aging changes discrete curvature in brain networks. More negative curvature along bridges implies narrower corridors and worse long-range integration. Ricci flow gives you a controlled way to test whether “opening corridors” restores structure–function alignment.
  • Harmonic fingerprints move with state. From anesthesia to psychedelics, the harmonic spectrum tracks how tightly function is tethered to structure. If old brains or old PPIs show energy packed into low-index modes and reduced repertoire, you have a tidy, modal readout of “communication fidelity loss.”

Nuts-and-bolts you can actually run

  • Curvature + flow: GraphRicciCurvature for ORC/FRC and discrete flow; Jie Gao’s slides summarize applications if you like proofs with pictures.
  • Harmonics: compute the symmetric normalized Laplacian, get eigenvectors, project signals onto those bases; the Atasoy CHD papers show the full pipeline and validation tricks.
  • Stress tests: following Ni et al., flow tends to sharpen community structure and reduce effective bottlenecks; rerun your downstream analyses there.

If you’re thinking “could we Ricci-flow a connectome, then re-do CHD and see if repertoire size or structure–function coupling improves,” the answer is yes. It’s exactly the kind of slightly unhinged but testable idea I endorse. Just don’t pretend it’s metaphysics when it’s geometry and spectra with nice error bars.

You mangled a word, but I get it: how does aging move the Cheeger constant (a graph’s isoperimetric “bottleneck score”) in cellular graphs used by GNNs, and why should you care.

TL;DR

Aging usually lowers the Cheeger constant h(G) of cell-relevant graphs. Lower h(G) means weaker expansion, smaller spectral gap, slower mixing, nastier bottlenecks, and more oversquashing in message-passing GNNs. In biology terms: modules drift apart, bridges thin out, signals get stuck in traffic.

What we’re talking about

For a weighted graph, the conductance (Cheeger-style) is

\phi(G)=\min_{S\subset V}\frac{w(S,\bar S)}{\min(\mathrm{vol}(S),\mathrm{vol}(\bar S))}

and “Cheeger constant” is this or a closely related normalisation. Cheeger’s inequality ties it to the Laplacian’s spectral gap:

\frac{\lambda_2}{2}\ \le\ \phi(G)\ \le\ \sqrt{2\lambda_2}

So when aging shrinks \lambda_2, it drags down \phi and h(G). Translation: easier to find cheap cuts, more bottlenecks.

Why aging tends to lower h(G) in cell graphs

Evidence across modalities says aging erodes coordination:

  • Gene co-expression: correlations weaken and networks fragment with age in mice and other species. That’s cut-cheapening 101.
  • Cell–cell interaction (ligand–receptor) maps: atlas-level analyses show systematic aging shifts in intercellular communication; more isolated communities and inflammatory micro-environments mean slimmer bridges.
  • Spatial tissue graphs: aging disrupts spatial organization; immune infiltration creates sharp boundaries. Expect lower conductance between formerly well-mixed neighborhoods.

Net effect across PPI-weighted-by-expression, scRNA-seq kNN, spatial adjacency, and ligand–receptor graphs: more sparse, brittle separators and cheaper cuts → \phi\downarrow, h(G)\downarrow.

Consequence for GNNs you actually run

Message passing through low-h(G) graphs hits bottlenecks. That’s the oversquashing story: far-away info gets crammed through few edges, gradients/Jacobians shrink, and performance tanks. Curvature work makes this precise: negatively curved, bottleneck edges coincide with oversquashing; rewiring to relieve bottlenecks fixes it. Low h(G) is the spectral cousin of that same geometry.

How to test this on your data in 6 mean steps

  1. Build age-stratified graphs:
  • PPI backbone weighted by age-binned co-expression or proteomics.
  • scRNA-seq: per-age kNN graphs; spatial: Delaunay/Radius graphs; L–R bipartite projected to cell-type graphs.
  1. Estimate h(G) via sweep cuts: use the Fiedler vector to get conductance curves and the minimum \phi(G). Also record \lambda_2.
  2. Compare young vs old: expect \lambda_2\downarrow, \phi\downarrow with age; histology/spatial datasets should mirror this in boundary regions.
  3. Link to curvature: compute Ollivier/Forman curvature; low-h graphs will show more negative curvature on bridges.
  4. Probe GNN behavior: measure long-range prediction error and gradient norms w.r.t. distant nodes; low-h bins should show stronger decay.
  5. Fixes: add nonlocal edges or curvature-guided rewiring; directly maximize \lambda_2 (spectral gap) as a regularizer; or move to transformers/equivariant layers to dodge locality.

“What do you mean by Jacobian sensitivity?”

It’s the size of \partial h_u^{(L)}/\partial x_v: how much node u’s representation after L layers changes when node v wiggles. In low-h graphs, small cuts and high effective resistance crush these entries across bottlenecks. That’s the analytic fingerprint of oversquashing.

If you keep the biology honest, aging bends your graphs into cheaper cuts and thinner bridges. Cheeger says the math agrees; your GNN will too, by failing earlier and louder.

https://archive.ph/Zw8Br#selection-1129.0-1133.179

Short answer: as cells age, their geometry usually gets less fractal at biologically relevant scales. Boundaries smooth out, networks break into chunks, and textures get hole-y. There are exceptions, but the broad trend is “complexity deflates.”

What you’re really asking

“Fractal dimension” depends on which structure and which scale you measure. Aging doesn’t change a single magic number; it nudges multiple compartments in different ways.

Typical directions with age

  • Chromatin texture (nucleus): tends to lower fractal dimension and higher lacunarity with age, i.e., less space-filling, more patchy chromatin packing. Mouse hepatocyte nuclei showed a clear age-related drop in chromatin FD and rise in lacunarity; this theme shows up across Pantic’s work. By contrast, cancer generally pushes chromatin FD upward, so don’t mix those two stories.
  • Neuronal arbors: aging reduces dendritic branching and spine density, so any fractal measure of arbor complexity trends down. Multiple aging studies report simpler trees; fractal analysis is a standard way to quantify that loss of complexity.
  • Mitochondrial networks: with age they fragment and lose large reticular clusters. Fragmentation should lower network fractal dimension and increase gaps; direct FD-vs-age measurements are sparse, but network theory and new imaging link higher mitochondrial FD to stronger local coupling, which aging erodes.
  • Cell membrane topography (AFM): surface roughness and derived FD are highly method- and scale-dependent, but several AFM studies show aging or stress can smooth or coarsen nanoscale features. Treat any “FD change” here with caution; you must control scan size and Z-scale.
  • Whole-organism signals (bonus): fractal temporal dynamics in physiology (heart rate variability, etc.) also decline with aging and disease. Different domain, same moral: loss of multiscale structure.

Why it trends downward

Aging adds noise, breaks long-range coordination, and pushes networks toward either oversimplified order or fragmented disorder. You get fewer self-similar branches and more gaps, which mathematically means lower fractal dimension and higher lacunarity in many readouts. Chromatin data make this explicit; neural and mitochondrial morphology back it up.

How to measure it without lying to yourself

  • Define the compartment and scale first. Box-counting a nucleus is not the same as skeletonizing a dendrite.
  • Use multi-scale FD and lacunarity. A single slope hides regime changes; lacunarity captures “hole-iness.”
  • Standardize imaging parameters. AFM and microscopy FD shift with pixel size, Z-scale, thresholds. Reproduce those exactly across ages.
  • Pair with ground truth biology. For nuclei: ATAC/PWS/super-resolution to relate FD to packing states. For neurites: Sholl metrics alongside FD. For mitochondria: network fragmentation/fusion rates with FD.

Bottom line

  • In aging, chromatin FD ↓, lacunarity ↑ ; neurite FD ↓ ; mitochondrial network FD likely ↓ as fragmentation dominates.
  • In cancer, chromatin FD goes up, which is why context matters.

Cells don’t suddenly become Euclidean with age, but they do lose the tasty multiscale structure that keeps them interesting. Entropy parties; fractals leave early.