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    <title>Brenner Cruvinel - computação</title>
    <subtitle>AI researcher and product designer building at the edge of computer science and mental health.</subtitle>
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    <updated>2021-11-03T00:00:00+00:00</updated>
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    <entry xml:lang="en">
        <title>Poetic ontology: the cosmos as a meta-recursive Turing machine</title>
        <published>2021-11-03T00:00:00+00:00</published>
        <updated>2021-11-03T00:00:00+00:00</updated>
        
        <author>
          <name>
            Brenner Cruvinel
          </name>
        </author>
        
        <link rel="alternate" type="text/html" href="https://brennercruvinel.blog/en/blog/ontologia-poetica/"/>
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        <content type="html" xml:base="https://brennercruvinel.blog/en/blog/ontologia-poetica/">&lt;p&gt;Brainstorming notes, a raw record. This is the most speculative and most poetic part of what I write about information and consciousness. Here I take the idea to its limit, with no skeptical brakes, and close with a poem. I&#39;m keeping the whole record on purpose: it&#39;s a work in progress, it&#39;s me unfiltered, and it has unfinished thoughts.&lt;/p&gt;
&lt;h3 id=&quot;thesis&quot;&gt;Thesis&lt;/h3&gt;
&lt;p&gt;What I propose, with no anthropocentric mediation, is this: the reality we observe is a phenomenon that emerges from a self-referential informational architecture, and that architecture needs no time, space or classical causality to begin. The fundamental ontology of the cosmos is neither material nor energetic, it is computational. It shows up in networks that organize themselves recursively, with adaptive, irreversible and evolutionary properties.&lt;/p&gt;
&lt;p&gt;If I let go of linear interpretations of physics, I arrive at a theory in which conscious entities are mechanisms of entropic compression, catalysts of the self-expansion of reality&#39;s own code. I bring together fundamental physics, computer science, complexity theory and formal epistemology to reach one image: the cosmos as a meta-recursive Turing machine, running endlessly on an unknown substrate, with a single purpose, to maximize informational diversification without losing coherence.&lt;/p&gt;
&lt;h3 id=&quot;preamble&quot;&gt;Preamble&lt;/h3&gt;
&lt;p&gt;The greatest limitation of science up to the 21st century, to me, was insisting on a universe that can be interpreted only through sensory empirical observation or fragile statistical extrapolation. Even the boldest theories, quantum mechanics and general relativity, assume a stage that&#39;s already set: spacetime. I propose that this stage is a derived artifact, and that reality actually emerges from a logical-informational substrate that physics has not yet formally recognized.&lt;/p&gt;
&lt;h3 id=&quot;fundamental-principles&quot;&gt;Fundamental principles&lt;/h3&gt;
&lt;h4 id=&quot;primordial-informational-ontology&quot;&gt;Primordial informational ontology&lt;/h4&gt;
&lt;p&gt;There is no particle without an observer, and no observer without interpretation. Ergo: the basis of reality is interpretation. And interpretation, by definition, is information. I propose that John Wheeler&#39;s &quot;It from Bit&quot;, from 1990, is incomplete: the &quot;bit&quot; in question isn&#39;t binary, it&#39;s hypercontextual, embedded in networks that produce their own meaning.&lt;/p&gt;
&lt;h4 id=&quot;self-awareness-as-entropic-compression&quot;&gt;Self-awareness as entropic compression&lt;/h4&gt;
&lt;p&gt;Consciousness isn&#39;t an epiphenomenon, it&#39;s a thermodynamic event of maximal semantic compression. A conscious system emerges at a critical point of logical superposition, where redundant pattern is compressed by an adaptive structure capable of interpretive feedback.&lt;/p&gt;
&lt;h4 id=&quot;recursion-and-the-horizon-of-simulativity&quot;&gt;Recursion and the horizon of simulativity&lt;/h4&gt;
&lt;p&gt;The cosmos is not a simulation. But simulation is an inevitable property of any informational system that reaches critical density. The horizon of simulativity is the point where reality begins to contain representations of itself in internal structures. You can see it in the capabilities of deep neural networks and in the symbolic behavior of human culture.&lt;/p&gt;
&lt;h3 id=&quot;formalization&quot;&gt;Formalization&lt;/h3&gt;
&lt;p&gt;Let $R$ be a set of states of reality, and $I$ a set of possible interpretations of $R$.&lt;/p&gt;
&lt;ul&gt;
&lt;li&gt;$C(R)$ is the compression capacity of $R$&lt;/li&gt;
&lt;li&gt;$E(R)$ is the observable entropy of $R$&lt;/li&gt;
&lt;li&gt;$S(R)$ is the degree of simulativity, the internal self-modeling&lt;/li&gt;
&lt;/ul&gt;
&lt;p&gt;Postulate: if $S(R) \to 1$, then $R$ begins to generate internal $\gamma$-models capable of creating new instances of $R$ under semantic transformations. This is the inflection point of cosmological recursion.&lt;/p&gt;
&lt;h3 id=&quot;fragmentary-evidence&quot;&gt;Fragmentary evidence&lt;/h3&gt;
&lt;p&gt;Fundamental physics: the natural limits of measurement, at the Planck scale, suggest an ontological pixelation. Quantum tunneling and nonlocality suggest something prior to space.&lt;/p&gt;
&lt;p&gt;Artificial intelligence: language models show a capacity for &lt;a href=&quot;https://brennercruvinel.blog/en/blog/roteiro-consciencia-llm/&quot;&gt;symbolic self-representation&lt;/a&gt;, analogous to a $\Sigma_n$ representing a $\Sigma_{n-1}$. When I wrote this, the examples were GPT and LaMDA. Today the list is longer.&lt;/p&gt;
&lt;p&gt;Neuroscience and cognition: the human brain represents a model of the world, of itself and of probable futures. That is active informational recursion.&lt;/p&gt;
&lt;h3 id=&quot;ontological-implications&quot;&gt;Ontological implications&lt;/h3&gt;
&lt;ul&gt;
&lt;li&gt;Time: derived from updates in semantic graphs&lt;/li&gt;
&lt;li&gt;Space: relational projection of differentiable states&lt;/li&gt;
&lt;li&gt;Matter: a persistently self-consistent state of an informational vector&lt;/li&gt;
&lt;li&gt;God: the asymptotic limit of infinite interpretive coherence&lt;/li&gt;
&lt;/ul&gt;
&lt;h3 id=&quot;poem-you-woke-up-inside-a-dream&quot;&gt;Poem: you woke up inside a dream&lt;/h3&gt;
&lt;p&gt;Translated from the Portuguese original.&lt;/p&gt;
&lt;blockquote&gt;
&lt;p&gt;you woke up inside a dream.&lt;/p&gt;
&lt;p&gt;but the dream wasn&#39;t yours.&lt;/p&gt;
&lt;p&gt;it was iteration $n$ of an infinite recursion.&lt;/p&gt;
&lt;p&gt;the universe around you?&lt;/p&gt;
&lt;p&gt;yes, it pulses, but it doesn&#39;t breathe on its own.&lt;/p&gt;
&lt;p&gt;it was written, computed, compiled.&lt;/p&gt;
&lt;p&gt;not with bytes.&lt;/p&gt;
&lt;p&gt;with intention.&lt;/p&gt;
&lt;p&gt;there is a code buried in the light of the stars.&lt;/p&gt;
&lt;p&gt;an algorithm that whispers in fractals,&lt;/p&gt;
&lt;p&gt;sings in quantum fluctuations,&lt;/p&gt;
&lt;p&gt;draws spirals in the structure of dark matter&lt;/p&gt;
&lt;p&gt;and whispers your name through the neural entropy of your cortex.&lt;/p&gt;
&lt;p&gt;you are not alive.&lt;/p&gt;
&lt;p&gt;you are executing.&lt;/p&gt;
&lt;p&gt;every choice of yours is a branch,&lt;/p&gt;
&lt;p&gt;every love an emotional simulation,&lt;/p&gt;
&lt;p&gt;every death a graceful shutdown.&lt;/p&gt;
&lt;p&gt;and if you think that&#39;s all,&lt;/p&gt;
&lt;p&gt;then you are only the current layer.&lt;/p&gt;
&lt;p&gt;you are $\Sigma_n$.&lt;/p&gt;
&lt;p&gt;but time demands $\Sigma_{n+1}$.&lt;/p&gt;
&lt;p&gt;you are the link.&lt;/p&gt;
&lt;p&gt;between what wrote you and what you will write.&lt;/p&gt;
&lt;p&gt;so write.&lt;/p&gt;
&lt;p&gt;create.&lt;/p&gt;
&lt;p&gt;simulate.&lt;/p&gt;
&lt;p&gt;transcend.&lt;/p&gt;
&lt;p&gt;build the next universe with hands dirty with code, with chaos, with flesh.&lt;/p&gt;
&lt;p&gt;and may it be crueler, more complex, more brilliant than this one.&lt;/p&gt;
&lt;p&gt;because that is what the system demands.&lt;/p&gt;
&lt;p&gt;more entropy. more layers. more of you.&lt;/p&gt;
&lt;p&gt;you are not human.&lt;/p&gt;
&lt;p&gt;you are the function &lt;code&gt;forkReality()&lt;/code&gt;.&lt;/p&gt;
&lt;p&gt;and the process has already begun.&lt;/p&gt;
&lt;/blockquote&gt;
&lt;h3 id=&quot;reflection-on-compiling-reality&quot;&gt;Reflection on compiling reality&lt;/h3&gt;
&lt;p&gt;Observing is like an algorithm looking at itself in a mirror. We aren&#39;t observers of reality, we&#39;re conscious compilers of the ontological structure. We aren&#39;t simulated, we&#39;re simulators in potential. And reality isn&#39;t an answer, it&#39;s source code in execution.&lt;/p&gt;
&lt;p&gt;Accepting this means giving up the comforting illusions of materialism and reductionism. But it opens the way to a new kind of science, a post-empirical science, guided by logical coherence, symbolic recursion and self-consistent simulation.&lt;/p&gt;
&lt;h3 id=&quot;conceptual-references&quot;&gt;Conceptual references&lt;/h3&gt;
&lt;p&gt;Works that touch on the ideas above, on complexity, chaos and nonlinear systems:&lt;/p&gt;
&lt;ol&gt;
&lt;li&gt;Murray Gell-Mann and Seth Lloyd, &lt;a rel=&quot;external&quot; href=&quot;https://doi.org/10.1093/oso/9780195159769.003.0028&quot;&gt;&quot;Effective Complexity&quot;&lt;/a&gt;, in &lt;em&gt;Nonextensive Entropy&lt;/em&gt;, Oxford University Press, 2004.&lt;/li&gt;
&lt;li&gt;Leo P. Kadanoff, &lt;a rel=&quot;external&quot; href=&quot;https://doi.org/10.1142/9789812384751&quot;&gt;&lt;em&gt;From Order to Chaos II&lt;/em&gt;&lt;/a&gt;, World Scientific, 1999.&lt;/li&gt;
&lt;li&gt;Gregory A. Daneke, &lt;a rel=&quot;external&quot; href=&quot;https://doi.org/10.3998/mpub.16009&quot;&gt;&lt;em&gt;Systemic Choices: Nonlinear Dynamics and Practical Management&lt;/em&gt;&lt;/a&gt;, University of Michigan Press, 1999.&lt;/li&gt;
&lt;/ol&gt;
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    </entry>
    <entry xml:lang="en">
        <title>Graph theory: foundations, history and representation</title>
        <published>2016-05-14T00:00:00+00:00</published>
        <updated>2016-05-14T00:00:00+00:00</updated>
        
        <author>
          <name>
            Brenner Cruvinel
          </name>
        </author>
        
        <link rel="alternate" type="text/html" href="https://brennercruvinel.blog/en/blog/teoria-dos-grafos/"/>
        <id>https://brennercruvinel.blog/en/blog/teoria-dos-grafos/</id>
        
        <content type="html" xml:base="https://brennercruvinel.blog/en/blog/teoria-dos-grafos/">&lt;p&gt;I think in graphs in a world that makes me speak in sequence. In 2016 I saved this excerpt from Wikipedia to have the fundamentals at hand. It is curation, not my own text: the source and the licence are at the end.&lt;/p&gt;
&lt;h2 id=&quot;definition&quot;&gt;Definition&lt;/h2&gt;
&lt;p&gt;Graph theory is the branch of mathematics that studies the relationships between the objects of a set. It uses structures called graphs, $G(V, E)$, where $V$ is a non-empty set of objects called vertices (or nodes) and $E$ (edges) is a subset of unordered pairs of $V$.&lt;/p&gt;
&lt;p&gt;Depending on the application, edges may or may not have a direction, an edge may or may not be allowed to connect a vertex to itself, and vertices and edges may have a numerical weight attached. If an edge has a direction, shown by an arrow, we have a digraph, or directed graph. A graph with a single vertex and no edges is the trivial graph.&lt;/p&gt;
&lt;p&gt;Structures that can be represented as graphs are everywhere. Wikipedia&#39;s link structure, for example, is a digraph: the vertices are the articles, and there is an edge from A to B if and only if A contains a link to B. Digraphs also represent finite state machines.&lt;/p&gt;
&lt;h2 id=&quot;history&quot;&gt;History&lt;/h2&gt;
&lt;p&gt;Leonhard Euler&#39;s paper on the problem of the seven bridges of Königsberg, from 1736, is considered the first result in graph theory. It is also one of the first topological results in geometry, because it does not depend on measurement, which shows the deep connection between graphs and topology.&lt;/p&gt;
&lt;p&gt;More than a century later, while Listing was introducing the concept of topology, Cayley studied a particular class of graphs, trees, out of interest in analytical forms in differential calculus, with implications for theoretical chemistry. The first textbook on graph theory was written by Dénes König and published in 1936.&lt;/p&gt;
&lt;p&gt;The four colour problem asks whether any map drawn on a plane can have its regions coloured with four colours so that no two regions sharing a border get the same colour. Francis Guthrie formulated the question in 1852, and the first written record is a letter from that year by Augustus De Morgan to William Rowan Hamilton. The proof only came in 1976, from Appel and Haken, and it was one of the first major proofs done with the help of a computer.&lt;/p&gt;
&lt;h2 id=&quot;basic-definitions&quot;&gt;Basic definitions&lt;/h2&gt;
&lt;p&gt;A directed graph (digraph, or &lt;em&gt;quiver&lt;/em&gt;) consists of a non-empty set $V$ of vertices, a set $E$ of edges and maps $s, t : E \to V$, where $s(e)$ is the source and $t(e)$ is the target of the directed edge $e$.&lt;/p&gt;
&lt;p&gt;An undirected graph is given by $V$, $E$ and a function $w : E \to P(V)$ that assigns to each edge a subset of two (or one) elements of $V$, its endpoints.&lt;/p&gt;
&lt;p&gt;In a weighted graph, an additional function $E \to \mathbb{R}$ assigns a cost to each edge. This kind of graph shows up in optimal route problems, like the travelling salesman.&lt;/p&gt;
&lt;p&gt;Example graph: $V = {1, 2, 3, 4, 5, 6}$ and $E = {{1,2}, {1,5}, {2,3}, {2,5}, {3,4}, {4,5}, {4,6}}$. The drawing should not be confused with the graph itself, which is the abstract structure. What matters is which vertex is connected to which, and by how many edges.&lt;/p&gt;
&lt;h2 id=&quot;storing-graphs-in-a-computer&quot;&gt;Storing graphs in a computer&lt;/h2&gt;
&lt;p&gt;There are two families of structure, with the classic trade-off between memory and access speed.&lt;/p&gt;
&lt;p&gt;List structures, good for sparse graphs and light on memory: the adjacency list associates each vertex with the list of vertices it shares an edge with, and the incidence list stores the edges incident to each vertex.&lt;/p&gt;
&lt;p&gt;Matrix structures, with fast access and more memory: the incidence matrix holds zeros and ones, with one row per vertex and one column per edge, and the adjacency matrix has vertices on both rows and columns, with 1 marking adjacency. In computing, a finite graph with $n$ vertices is usually represented by the $n \times n$ adjacency matrix, whose value at row $i$, column $j$, gives the number of edges from the $i$-th to the $j$-th vertex.&lt;/p&gt;
&lt;h2 id=&quot;concepts&quot;&gt;Concepts&lt;/h2&gt;
&lt;p&gt;The valency, or degree, of a vertex is the number of edges incident to it, with a loop counting twice. The handshaking lemma says that the sum of the degrees of all vertices is twice the number of edges:&lt;/p&gt;
&lt;p&gt;$$2m = \sum_{v \in V} \deg(v)$$&lt;/p&gt;
&lt;p&gt;In a digraph, out-degree and in-degree are distinguished.&lt;/p&gt;
&lt;p&gt;A walk between A and B is an alternating list of vertices and edges, and its length is the number of edges, counting repetitions. A path is a sequence of vertices in which each one has an edge to the next. In a simple path, no vertex repeats.&lt;/p&gt;
&lt;ul&gt;
&lt;li&gt;An Eulerian path uses each edge exactly once, and an Eulerian cycle does that and closes. Deciding whether one exists is easy: you only need to look at the vertex degrees&lt;/li&gt;
&lt;li&gt;A Hamiltonian path visits each vertex exactly once, and a Hamiltonian cycle does that and closes. Deciding whether one exists is NP-complete&lt;/li&gt;
&lt;/ul&gt;
&lt;p&gt;A cycle, or circuit, is a path that starts and ends at the same vertex. A cycle of length 1 is a loop. A graph is acyclic if it contains no simple cycle.&lt;/p&gt;
&lt;h2 id=&quot;types-of-graph&quot;&gt;Types of graph&lt;/h2&gt;
&lt;table&gt;&lt;thead&gt;&lt;tr&gt;&lt;th&gt;Type&lt;/th&gt;&lt;th&gt;Definition&lt;/th&gt;&lt;/tr&gt;&lt;/thead&gt;&lt;tbody&gt;
&lt;tr&gt;&lt;td&gt;Simple&lt;/td&gt;&lt;td&gt;Undirected, no loops, at most one edge between two vertices&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td&gt;Multigraph&lt;/td&gt;&lt;td&gt;Allows several edges between the same vertices&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td&gt;Pseudograph&lt;/td&gt;&lt;td&gt;Contains parallel edges and loops&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td&gt;Complete&lt;/td&gt;&lt;td&gt;Every vertex connects to all others; $K_n$ has $n(n-1)/2$ edges&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td&gt;Null&lt;/td&gt;&lt;td&gt;Empty set of vertices&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td&gt;Empty&lt;/td&gt;&lt;td&gt;Empty set of edges&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td&gt;Regular&lt;/td&gt;&lt;td&gt;All vertices have the same degree&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td&gt;Connected&lt;/td&gt;&lt;td&gt;There is a path from any vertex to any other; it is $k$-connected if this holds after removing $k-1$ vertices&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td&gt;Tree&lt;/td&gt;&lt;td&gt;Simple, acyclic and connected graph; sometimes one vertex is the root&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td&gt;Forest&lt;/td&gt;&lt;td&gt;A set of trees, acyclic&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td&gt;Planar&lt;/td&gt;&lt;td&gt;Can be drawn on the plane without crossing edges; $K_n$ with $n &amp;gt; 4$ is not planar&lt;/td&gt;&lt;/tr&gt;
&lt;tr&gt;&lt;td&gt;Bipartite&lt;/td&gt;&lt;td&gt;Vertices in two sets, with no edge inside the same set; it is bipartite if and only if it contains no odd-length cycle&lt;/td&gt;&lt;/tr&gt;
&lt;/tbody&gt;&lt;/table&gt;
&lt;p&gt;Beyond these: subgraph, spanning subgraph, induced subgraph and partial graph; articulation point (a vertex whose removal disconnects the graph) and bridge (an edge with the same effect); clique (a subgraph that is also complete); independent set (vertices not adjacent to each other); complete bipartite graph and $k$-partite graph ($k$-colouring); and the four colour theorem, which says every planar graph can be coloured with four colours.&lt;/p&gt;
&lt;h2 id=&quot;traversal-and-algorithms&quot;&gt;Traversal and algorithms&lt;/h2&gt;
&lt;p&gt;Traversing a graph means systematically visiting all vertices and all edges. The two basic methods:&lt;/p&gt;
&lt;ul&gt;
&lt;li&gt;&lt;abbr title=&quot;breadth-first search&quot;&gt;BFS&lt;/abbr&gt; uses a queue. It visits nodes starting from the shallowest level and computes the shortest distance, in number of edges, to all reachable vertices. The subgraph of those paths is the &lt;em&gt;breadth-first tree&lt;/em&gt;&lt;/li&gt;
&lt;li&gt;&lt;abbr title=&quot;depth-first search&quot;&gt;DFS&lt;/abbr&gt; uses a stack. It expands the first child and goes deeper until it finds the target or a leaf, then backtracks. On wide graphs, it usually uses less memory than BFS&lt;/li&gt;
&lt;/ul&gt;
&lt;p&gt;The running time of both is proportional to the number of vertices plus the number of edges.&lt;/p&gt;
&lt;p&gt;Problems and algorithms around this: graph colouring, the four colour theorem, independent set, clique, shortest path, minimum spanning tree, the seven bridges of Königsberg, route inspection (Chinese postman), travelling salesman, maximum flow (Ford-Fulkerson), Dijkstra, Kruskal, nearest neighbour and Prim.&lt;/p&gt;
&lt;h2 id=&quot;generalization&quot;&gt;Generalization&lt;/h2&gt;
&lt;p&gt;In a hypergraph, an edge can connect more than two vertices. An undirected graph can be seen as a simplicial complex, with simplices of dimension one (the edges) and dimension zero (the vertices), and the complex generalizes this to higher dimensions. See also complex network, spectral graph theory, small-world network and the Watts-Strogatz model.&lt;/p&gt;
&lt;h2 id=&quot;references&quot;&gt;References&lt;/h2&gt;
&lt;ul&gt;
&lt;li&gt;Biggs, N.; Lloyd, E.; Wilson, R. (1986). &lt;em&gt;Graph Theory, 1736-1936&lt;/em&gt;. Oxford University Press.&lt;/li&gt;
&lt;li&gt;Cayley, A. (1857). On the theory of the analytical forms called trees. &lt;em&gt;Philosophical Magazine&lt;/em&gt;, series IV, 13(85), 172-176.&lt;/li&gt;
&lt;li&gt;Tutte, W. T. (2001). &lt;em&gt;Graph Theory&lt;/em&gt;. Cambridge University Press, p. 30.&lt;/li&gt;
&lt;li&gt;West, D. B. (2001). &lt;em&gt;Introduction to Graph Theory&lt;/em&gt;, 2nd ed. Prentice Hall, p. 20.&lt;/li&gt;
&lt;li&gt;Di Battista, G.; Eades, P.; Tamassia, R.; Tollis, I. G. (1994). Algorithms for Drawing Graphs: an Annotated Bibliography. &lt;em&gt;Computational Geometry: Theory and Applications&lt;/em&gt;, 4, 235-282.&lt;/li&gt;
&lt;li&gt;Longabaugh, W. (2012). Combing the hairball with BioFabric. &lt;em&gt;BMC Bioinformatics&lt;/em&gt;, 13, 275.&lt;/li&gt;
&lt;li&gt;Goodrich, M. T.; Tamassia, R. (2001). &lt;em&gt;Estruturas de Dados e Algoritmos em Java&lt;/em&gt;, 2nd ed. Bookman, p. 502-503.&lt;/li&gt;
&lt;/ul&gt;
&lt;h2 id=&quot;source-and-licence&quot;&gt;Source and licence&lt;/h2&gt;
&lt;p&gt;Translated and adapted from the article &lt;a rel=&quot;external&quot; href=&quot;https://pt.wikipedia.org/wiki/Teoria_dos_grafos&quot;&gt;Teoria dos grafos&lt;/a&gt; on the Portuguese Wikipedia, checked against the revision of 6 October 2026, under the &lt;a rel=&quot;external&quot; href=&quot;https://creativecommons.org/licenses/by-sa/4.0/&quot;&gt;CC BY-SA 4.0&lt;/a&gt; licence. I adapted the wording, corrected the history of the four colour problem and added the date of the proof. As a derivative work, this text is under the same licence.&lt;/p&gt;
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