P. 485 of Theorem List - Metamath Proof Explorer

Theorem List for Metamath Proof Explorer - 48401-48500   *Has distinct variable group(s)

Type	Label	Description
Statement
Theorem	gpg3nbgrvtx1 48401	In a generalized Petersen graph 𝐺, every inside vertex has exactly three (different) neighbors. (Contributed by AV, 3-Sep-2025.) (Proof shortened by AV, 22-Nov-2025.)
⊢ 𝐽 = (1..^(⌈‘(𝑁 / 2)))    &   ⊢ 𝐺 = (𝑁 gPetersenGr 𝐾)    &   ⊢ 𝑉 = (Vtx‘𝐺)    &   ⊢ 𝑈 = (𝐺 NeighbVtx 𝑋)    ⇒   ⊢ (((𝑁 ∈ (ℤ≥‘3) ∧ 𝐾 ∈ 𝐽) ∧ (𝑋 ∈ 𝑉 ∧ (1st ‘𝑋) = 1)) → (♯‘𝑈) = 3)
Theorem	gpgcubic 48402	Every generalized Petersen graph is a cubic graph, i.e., it is a 3-regular graph, i.e., every vertex has degree 3 (see gpgvtxdg3 48405), i.e., every vertex has exactly three (different) neighbors. (Contributed by AV, 3-Sep-2025.)
⊢ 𝐽 = (1..^(⌈‘(𝑁 / 2)))    &   ⊢ 𝐺 = (𝑁 gPetersenGr 𝐾)    &   ⊢ 𝑉 = (Vtx‘𝐺)    &   ⊢ 𝑈 = (𝐺 NeighbVtx 𝑋)    ⇒   ⊢ ((𝑁 ∈ (ℤ≥‘3) ∧ 𝐾 ∈ 𝐽 ∧ 𝑋 ∈ 𝑉) → (♯‘𝑈) = 3)
Theorem	gpg5nbgrvtx03star 48403*	In a generalized Petersen graph G(N,K) of order greater than 8 (3 < 𝑁), every outside vertex has exactly three (different) neighbors, and none of these neighbors are connected by an edge (i.e., the (closed) neighborhood of every outside vertex induces a subgraph which is isomorphic to a 3-star). (Contributed by AV, 31-Aug-2025.)
⊢ 𝐽 = (1..^(⌈‘(𝑁 / 2)))    &   ⊢ 𝐺 = (𝑁 gPetersenGr 𝐾)    &   ⊢ 𝑉 = (Vtx‘𝐺)    &   ⊢ 𝑈 = (𝐺 NeighbVtx 𝑋)    &   ⊢ 𝐸 = (Edg‘𝐺)    ⇒   ⊢ (((𝑁 ∈ (ℤ≥‘4) ∧ 𝐾 ∈ 𝐽) ∧ (𝑋 ∈ 𝑉 ∧ (1st ‘𝑋) = 0)) → ((♯‘𝑈) = 3 ∧ ∀𝑥 ∈ 𝑈 ∀𝑦 ∈ 𝑈 {𝑥, 𝑦} ∉ 𝐸))
Theorem	gpg5nbgr3star 48404*	In a generalized Petersen graph G(N,K) of order 10 (𝑁 = 5), these are the Petersen graph G(5,2) and the 5-prism G(5,1), every vertex has exactly three (different) neighbors, and none of these neighbors are connected by an edge (i.e., the (closed) neighborhood of every vertex induces a subgraph which is isomorphic to a 3-star). This does not hold for every generalized Petersen graph: for example, in the 3-prism G(3,1) (see gpg31grim3prism TODO) and the Dürer graph G(6,2) there are vertices which have neighborhoods containing triangles. In general, all generalized Petersen graphs G(N,K) with 𝑁 = 3 · 𝐾 contain triangles, see gpg3kgrtriex 48412. (Contributed by AV, 8-Sep-2025.)
⊢ 𝐽 = (1..^(⌈‘(𝑁 / 2)))    &   ⊢ 𝐺 = (𝑁 gPetersenGr 𝐾)    &   ⊢ 𝑉 = (Vtx‘𝐺)    &   ⊢ 𝑈 = (𝐺 NeighbVtx 𝑋)    &   ⊢ 𝐸 = (Edg‘𝐺)    ⇒   ⊢ ((𝑁 = 5 ∧ 𝐾 ∈ 𝐽 ∧ 𝑋 ∈ 𝑉) → ((♯‘𝑈) = 3 ∧ ∀𝑥 ∈ 𝑈 ∀𝑦 ∈ 𝑈 {𝑥, 𝑦} ∉ 𝐸))
Theorem	gpgvtxdg3 48405	Every vertex in a generalized Petersen graph has degree 3. (Contributed by AV, 4-Sep-2025.)
⊢ 𝐽 = (1..^(⌈‘(𝑁 / 2)))    &   ⊢ 𝐺 = (𝑁 gPetersenGr 𝐾)    &   ⊢ 𝑉 = (Vtx‘𝐺)    ⇒   ⊢ ((𝑁 ∈ (ℤ≥‘3) ∧ 𝐾 ∈ 𝐽 ∧ 𝑋 ∈ 𝑉) → ((VtxDeg‘𝐺)‘𝑋) = 3)
Theorem	gpg3kgrtriexlem1 48406	Lemma 1 for gpg3kgrtriex 48412. (Contributed by AV, 1-Oct-2025.)
⊢ (𝐾 ∈ ℕ → 𝐾 < (⌈‘((3 · 𝐾) / 2)))
Theorem	gpg3kgrtriexlem2 48407	Lemma 2 for gpg3kgrtriex 48412. (Contributed by AV, 1-Oct-2025.)
⊢ 𝑁 = (3 · 𝐾)    ⇒   ⊢ (𝐾 ∈ ℕ → (-𝐾 mod 𝑁) = (((𝐾 mod 𝑁) + 𝐾) mod 𝑁))
Theorem	gpg3kgrtriexlem3 48408	Lemma 3 for gpg3kgrtriex 48412. (Contributed by AV, 1-Oct-2025.)
⊢ 𝑁 = (3 · 𝐾)    ⇒   ⊢ (𝐾 ∈ ℕ → 𝑁 ∈ (ℤ≥‘3))
Theorem	gpg3kgrtriexlem4 48409	Lemma 4 for gpg3kgrtriex 48412. (Contributed by AV, 1-Oct-2025.)
⊢ 𝑁 = (3 · 𝐾)    ⇒   ⊢ (𝐾 ∈ ℕ → 𝐾 ∈ (1..^(⌈‘(𝑁 / 2))))
Theorem	gpg3kgrtriexlem5 48410	Lemma 5 for gpg3kgrtriex 48412. (Contributed by AV, 1-Oct-2025.)
⊢ 𝑁 = (3 · 𝐾)    ⇒   ⊢ (𝐾 ∈ ℕ → (𝐾 mod 𝑁) ≠ (-𝐾 mod 𝑁))
Theorem	gpg3kgrtriexlem6 48411	Lemma 6 for gpg3kgrtriex 48412: 𝐸 is an edge in the generalized Petersen graph G(N,K) with 𝑁 = 3 · 𝐾. (Contributed by AV, 1-Oct-2025.)
⊢ 𝑁 = (3 · 𝐾)    &   ⊢ 𝐺 = (𝑁 gPetersenGr 𝐾)    &   ⊢ 𝐸 = {⟨1, (𝐾 mod 𝑁)⟩, ⟨1, (-𝐾 mod 𝑁)⟩}    ⇒   ⊢ (𝐾 ∈ ℕ → 𝐸 ∈ (Edg‘𝐺))
Theorem	gpg3kgrtriex 48412*	All generalized Petersen graphs G(N,K) with 𝑁 = 3 · 𝐾 contain triangles. (Contributed by AV, 1-Oct-2025.)
⊢ 𝑁 = (3 · 𝐾)    &   ⊢ 𝐺 = (𝑁 gPetersenGr 𝐾)    ⇒   ⊢ (𝐾 ∈ ℕ → ∃𝑡 𝑡 ∈ (GrTriangles‘𝐺))
Theorem	gpg5gricstgr3 48413	Each closed neighborhood in a generalized Petersen graph G(N,K) of order 10 (𝑁 = 5), which is either the Petersen graph G(5,2) or the 5-prism G(5,1), is isomorphic to a 3-star. (Contributed by AV, 13-Sep-2025.)
⊢ 𝐺 = (5 gPetersenGr 𝐾)    ⇒   ⊢ ((𝐾 ∈ (1...2) ∧ 𝑉 ∈ (Vtx‘𝐺)) → (𝐺 ISubGr (𝐺 ClNeighbVtx 𝑉)) ≃𝑔𝑟 (StarGr‘3))
Theorem	pglem 48414	Lemma for theorems about Petersen graphs. (Contributed by AV, 10-Nov-2025.)
⊢ 2 ∈ (1..^(⌈‘(5 / 2)))
Theorem	pgjsgr 48415	A Petersen graph is a simple graph. (Contributed by AV, 10-Nov-2025.)
⊢ (5 gPetersenGr 2) ∈ USGraph
Theorem	gpg5grlim 48416	A local isomorphism between the two generalized Petersen graphs G(N,K) of order 10 (𝑁 = 5), which are the Petersen graph G(5,2) and the 5-prism G(5,1). (Contributed by AV, 28-Dec-2025.)
⊢ ( I ↾ ({0, 1} × (0..^5))) ∈ ((5 gPetersenGr 1) GraphLocIso (5 gPetersenGr 2))
Theorem	gpg5grlic 48417	The two generalized Petersen graphs G(N,K) of order 10 (𝑁 = 5), which are the Petersen graph G(5,2) and the 5-prism G(5,1), are locally isomorphic. (Contributed by AV, 29-Sep-2025.) (Proof shortened by AV, 22-Nov-2025.)
⊢ (5 gPetersenGr 1) ≃𝑙𝑔𝑟 (5 gPetersenGr 2)
Theorem	gpgprismgr4cycllem1 48418	Lemma 1 for gpgprismgr4cycl0 48429: the cycle ⟨𝑃, 𝐹⟩ consists of 4 edges (i.e., has length 4). (Contributed by AV, 1-Nov-2025.)
⊢ 𝐹 = ⟨“{⟨0, 0⟩, ⟨0, 1⟩} {⟨0, 1⟩, ⟨1, 1⟩} {⟨1, 1⟩, ⟨1, 0⟩} {⟨1, 0⟩, ⟨0, 0⟩}”⟩    ⇒   ⊢ (♯‘𝐹) = 4
Theorem	gpgprismgr4cycllem2 48419	Lemma 2 for gpgprismgr4cycl0 48429: the cycle ⟨𝑃, 𝐹⟩ is proper, i.e., it has no overlapping edges. (Contributed by AV, 2-Nov-2025.)
⊢ 𝐹 = ⟨“{⟨0, 0⟩, ⟨0, 1⟩} {⟨0, 1⟩, ⟨1, 1⟩} {⟨1, 1⟩, ⟨1, 0⟩} {⟨1, 0⟩, ⟨0, 0⟩}”⟩    ⇒   ⊢ Fun ◡𝐹
Theorem	gpgprismgr4cycllem3 48420*	Lemma 3 for gpgprismgr4cycl0 48429. (Contributed by AV, 5-Nov-2025.)
⊢ 𝐹 = ⟨“{⟨0, 0⟩, ⟨0, 1⟩} {⟨0, 1⟩, ⟨1, 1⟩} {⟨1, 1⟩, ⟨1, 0⟩} {⟨1, 0⟩, ⟨0, 0⟩}”⟩    ⇒   ⊢ ((𝑁 ∈ (ℤ≥‘3) ∧ 𝑋 ∈ (0..^4)) → ((𝐹‘𝑋) ∈ 𝒫 ({0, 1} × (0..^𝑁)) ∧ ∃𝑥 ∈ (0..^𝑁)((𝐹‘𝑋) = {⟨0, 𝑥⟩, ⟨0, ((𝑥 + 1) mod 𝑁)⟩} ∨ (𝐹‘𝑋) = {⟨0, 𝑥⟩, ⟨1, 𝑥⟩} ∨ (𝐹‘𝑋) = {⟨1, 𝑥⟩, ⟨1, ((𝑥 + 1) mod 𝑁)⟩})))
Theorem	gpgprismgr4cycllem4 48421	Lemma 4 for gpgprismgr4cycl0 48429: the cycle ⟨𝑃, 𝐹⟩ consists of 5 vertices (the first and the last vertex are identical, see gpgprismgr4cycllem6 48423. (Contributed by AV, 1-Nov-2025.)
⊢ 𝑃 = ⟨“⟨0, 0⟩⟨0, 1⟩⟨1, 1⟩⟨1, 0⟩⟨0, 0⟩”⟩    ⇒   ⊢ (♯‘𝑃) = 5
Theorem	gpgprismgr4cycllem5 48422	Lemma 5 for gpgprismgr4cycl0 48429. (Contributed by AV, 1-Nov-2025.)
⊢ 𝑃 = ⟨“⟨0, 0⟩⟨0, 1⟩⟨1, 1⟩⟨1, 0⟩⟨0, 0⟩”⟩    ⇒   ⊢ 𝑃 ∈ Word V
Theorem	gpgprismgr4cycllem6 48423	Lemma 6 for gpgprismgr4cycl0 48429: the cycle ⟨𝑃, 𝐹⟩ is closed, i.e., the first and the last vertex are identical. (Contributed by AV, 1-Nov-2025.)
⊢ 𝑃 = ⟨“⟨0, 0⟩⟨0, 1⟩⟨1, 1⟩⟨1, 0⟩⟨0, 0⟩”⟩    ⇒   ⊢ (𝑃‘0) = (𝑃‘4)
Theorem	gpgprismgr4cycllem7 48424	Lemma 7 for gpgprismgr4cycl0 48429: the cycle ⟨𝑃, 𝐹⟩ is proper, i.e., it has no overlapping vertices, except the first and the last one. (Contributed by AV, 1-Nov-2025.)
⊢ 𝑃 = ⟨“⟨0, 0⟩⟨0, 1⟩⟨1, 1⟩⟨1, 0⟩⟨0, 0⟩”⟩    ⇒   ⊢ ((𝑋 ∈ (0..^(♯‘𝑃)) ∧ 𝑌 ∈ (1..^4)) → (𝑋 ≠ 𝑌 → (𝑃‘𝑋) ≠ (𝑃‘𝑌)))
Theorem	gpgprismgr4cycllem8 48425	Lemma 8 for gpgprismgr4cycl0 48429. (Contributed by AV, 2-Nov-2025.)
⊢ 𝑃 = ⟨“⟨0, 0⟩⟨0, 1⟩⟨1, 1⟩⟨1, 0⟩⟨0, 0⟩”⟩    &   ⊢ 𝐹 = ⟨“{⟨0, 0⟩, ⟨0, 1⟩} {⟨0, 1⟩, ⟨1, 1⟩} {⟨1, 1⟩, ⟨1, 0⟩} {⟨1, 0⟩, ⟨0, 0⟩}”⟩    &   ⊢ 𝐺 = (𝑁 gPetersenGr 1)    ⇒   ⊢ (𝑁 ∈ (ℤ≥‘3) → 𝐹 ∈ Word dom (iEdg‘𝐺))
Theorem	gpgprismgr4cycllem9 48426	Lemma 9 for gpgprismgr4cycl0 48429. (Contributed by AV, 3-Nov-2025.)
⊢ 𝑃 = ⟨“⟨0, 0⟩⟨0, 1⟩⟨1, 1⟩⟨1, 0⟩⟨0, 0⟩”⟩    &   ⊢ 𝐹 = ⟨“{⟨0, 0⟩, ⟨0, 1⟩} {⟨0, 1⟩, ⟨1, 1⟩} {⟨1, 1⟩, ⟨1, 0⟩} {⟨1, 0⟩, ⟨0, 0⟩}”⟩    &   ⊢ 𝐺 = (𝑁 gPetersenGr 1)    ⇒   ⊢ (𝑁 ∈ (ℤ≥‘3) → 𝑃:(0...(♯‘𝐹))⟶(Vtx‘𝐺))
Theorem	gpgprismgr4cycllem10 48427	Lemma 10 for gpgprismgr4cycl0 48429. (Contributed by AV, 5-Nov-2025.)
⊢ 𝑃 = ⟨“⟨0, 0⟩⟨0, 1⟩⟨1, 1⟩⟨1, 0⟩⟨0, 0⟩”⟩    &   ⊢ 𝐹 = ⟨“{⟨0, 0⟩, ⟨0, 1⟩} {⟨0, 1⟩, ⟨1, 1⟩} {⟨1, 1⟩, ⟨1, 0⟩} {⟨1, 0⟩, ⟨0, 0⟩}”⟩    &   ⊢ 𝐺 = (𝑁 gPetersenGr 1)    ⇒   ⊢ ((𝑁 ∈ (ℤ≥‘3) ∧ 𝑋 ∈ (0..^(♯‘𝐹))) → ((iEdg‘𝐺)‘(𝐹‘𝑋)) = {(𝑃‘𝑋), (𝑃‘(𝑋 + 1))})
Theorem	gpgprismgr4cycllem11 48428	Lemma 11 for gpgprismgr4cycl0 48429. (Contributed by AV, 5-Nov-2025.)
⊢ 𝑃 = ⟨“⟨0, 0⟩⟨0, 1⟩⟨1, 1⟩⟨1, 0⟩⟨0, 0⟩”⟩    &   ⊢ 𝐹 = ⟨“{⟨0, 0⟩, ⟨0, 1⟩} {⟨0, 1⟩, ⟨1, 1⟩} {⟨1, 1⟩, ⟨1, 0⟩} {⟨1, 0⟩, ⟨0, 0⟩}”⟩    &   ⊢ 𝐺 = (𝑁 gPetersenGr 1)    ⇒   ⊢ (𝑁 ∈ (ℤ≥‘3) → 𝐹(Cycles‘𝐺)𝑃)
Theorem	gpgprismgr4cycl0 48429	The generalized Petersen graphs G(N,1), which are the N-prisms, have a cycle of length 4 starting at the vertex ⟨0, 0⟩. (Contributed by AV, 5-Nov-2025.)
⊢ 𝑃 = ⟨“⟨0, 0⟩⟨0, 1⟩⟨1, 1⟩⟨1, 0⟩⟨0, 0⟩”⟩    &   ⊢ 𝐹 = ⟨“{⟨0, 0⟩, ⟨0, 1⟩} {⟨0, 1⟩, ⟨1, 1⟩} {⟨1, 1⟩, ⟨1, 0⟩} {⟨1, 0⟩, ⟨0, 0⟩}”⟩    &   ⊢ 𝐺 = (𝑁 gPetersenGr 1)    ⇒   ⊢ (𝑁 ∈ (ℤ≥‘3) → (𝐹(Cycles‘𝐺)𝑃 ∧ (♯‘𝐹) = 4))
Theorem	gpgprismgr4cyclex 48430*	The generalized Petersen graphs G(N,1), which are the N-prisms, have (at least) one cycle of length 4. (Contributed by AV, 5-Nov-2025.)
⊢ (𝑁 ∈ (ℤ≥‘3) → ∃𝑝∃𝑓(𝑓(Cycles‘(𝑁 gPetersenGr 1))𝑝 ∧ (♯‘𝑓) = 4))
Theorem	pgnioedg1 48431	An inside and an outside vertex not adjacent in a Petersen graph. (Contributed by AV, 21-Nov-2025.)
⊢ 𝐺 = (5 gPetersenGr 2)    &   ⊢ 𝐸 = (Edg‘𝐺)    ⇒   ⊢ (𝑦 ∈ (0..^5) → ¬ {⟨1, ((𝑦 − 2) mod 5)⟩, ⟨0, ((𝑦 + 1) mod 5)⟩} ∈ 𝐸)
Theorem	pgnioedg2 48432	An inside and an outside vertex not adjacent in a Petersen graph. (Contributed by AV, 21-Nov-2025.)
⊢ 𝐺 = (5 gPetersenGr 2)    &   ⊢ 𝐸 = (Edg‘𝐺)    ⇒   ⊢ (𝑦 ∈ (0..^5) → ¬ {⟨1, ((𝑦 + 2) mod 5)⟩, ⟨0, ((𝑦 + 1) mod 5)⟩} ∈ 𝐸)
Theorem	pgnioedg3 48433	An inside and an outside vertex not adjacent in a Petersen graph. (Contributed by AV, 21-Nov-2025.)
⊢ 𝐺 = (5 gPetersenGr 2)    &   ⊢ 𝐸 = (Edg‘𝐺)    ⇒   ⊢ (𝑦 ∈ (0..^5) → ¬ {⟨1, ((𝑦 + 2) mod 5)⟩, ⟨0, ((𝑦 − 1) mod 5)⟩} ∈ 𝐸)
Theorem	pgnioedg4 48434	An inside and an outside vertex not adjacent in a Petersen graph. (Contributed by AV, 21-Nov-2025.)
⊢ 𝐺 = (5 gPetersenGr 2)    &   ⊢ 𝐸 = (Edg‘𝐺)    ⇒   ⊢ (𝑦 ∈ (0..^5) → ¬ {⟨1, ((𝑦 − 2) mod 5)⟩, ⟨0, ((𝑦 − 1) mod 5)⟩} ∈ 𝐸)
Theorem	pgnioedg5 48435	An inside and an outside vertex not adjacent in a Petersen graph. (Contributed by AV, 21-Nov-2025.)
⊢ 𝐺 = (5 gPetersenGr 2)    &   ⊢ 𝐸 = (Edg‘𝐺)    ⇒   ⊢ (𝑦 ∈ (0..^5) → ¬ {⟨1, ((𝑦 − 1) mod 5)⟩, ⟨0, ((𝑦 + 1) mod 5)⟩} ∈ 𝐸)
Theorem	pgnbgreunbgrlem1 48436*	Lemma 1 for pgnbgreunbgr 48448. (Contributed by AV, 15-Nov-2025.)
⊢ 𝐺 = (5 gPetersenGr 2)    &   ⊢ 𝑉 = (Vtx‘𝐺)    &   ⊢ 𝐸 = (Edg‘𝐺)    &   ⊢ 𝑁 = (𝐺 NeighbVtx 𝑋)    ⇒   ⊢ ((𝐿 = ⟨0, (((2nd ‘𝑋) + 1) mod 5)⟩ ∨ 𝐿 = ⟨1, (2nd ‘𝑋)⟩ ∨ 𝐿 = ⟨0, (((2nd ‘𝑋) − 1) mod 5)⟩) → ((𝐾 = ⟨0, (((2nd ‘𝑋) + 1) mod 5)⟩ ∨ 𝐾 = ⟨1, (2nd ‘𝑋)⟩ ∨ 𝐾 = ⟨0, (((2nd ‘𝑋) − 1) mod 5)⟩) → ((𝑋 ∈ 𝑉 ∧ 𝑋 = ⟨0, 𝑦⟩) → ((𝐾 ≠ 𝐿 ∧ (𝑏 ∈ (0..^5) ∧ 𝑦 ∈ (0..^5))) → (({𝐾, ⟨0, 𝑏⟩} ∈ 𝐸 ∧ {⟨0, 𝑏⟩, 𝐿} ∈ 𝐸) → 𝑋 = ⟨0, 𝑏⟩)))))
Theorem	pgnbgreunbgrlem2lem1 48437*	Lemma 1 for pgnbgreunbgrlem2 48440. (Contributed by AV, 16-Nov-2025.)
⊢ 𝐺 = (5 gPetersenGr 2)    &   ⊢ 𝑉 = (Vtx‘𝐺)    &   ⊢ 𝐸 = (Edg‘𝐺)    &   ⊢ 𝑁 = (𝐺 NeighbVtx 𝑋)    ⇒   ⊢ ((((𝐿 = ⟨1, ((𝑦 + 2) mod 5)⟩ ∧ 𝐾 = ⟨0, 𝑦⟩) ∧ (𝑏 ∈ (0..^5) ∧ 𝑦 ∈ (0..^5))) ∧ {𝐾, ⟨0, 𝑏⟩} ∈ 𝐸) → ¬ {⟨0, 𝑏⟩, 𝐿} ∈ 𝐸)
Theorem	pgnbgreunbgrlem2lem2 48438*	Lemma 2 for pgnbgreunbgrlem2 48440. (Contributed by AV, 16-Nov-2025.)
⊢ 𝐺 = (5 gPetersenGr 2)    &   ⊢ 𝑉 = (Vtx‘𝐺)    &   ⊢ 𝐸 = (Edg‘𝐺)    &   ⊢ 𝑁 = (𝐺 NeighbVtx 𝑋)    ⇒   ⊢ ((((𝐿 = ⟨1, ((𝑦 − 2) mod 5)⟩ ∧ 𝐾 = ⟨0, 𝑦⟩) ∧ (𝑏 ∈ (0..^5) ∧ 𝑦 ∈ (0..^5))) ∧ {𝐾, ⟨0, 𝑏⟩} ∈ 𝐸) → ¬ {⟨0, 𝑏⟩, 𝐿} ∈ 𝐸)
Theorem	pgnbgreunbgrlem2lem3 48439*	Lemma 3 for pgnbgreunbgrlem2 48440. (Contributed by AV, 17-Nov-2025.)
⊢ 𝐺 = (5 gPetersenGr 2)    &   ⊢ 𝑉 = (Vtx‘𝐺)    &   ⊢ 𝐸 = (Edg‘𝐺)    &   ⊢ 𝑁 = (𝐺 NeighbVtx 𝑋)    ⇒   ⊢ ((((𝐿 = ⟨1, ((𝑦 + 2) mod 5)⟩ ∧ 𝐾 = ⟨1, ((𝑦 − 2) mod 5)⟩) ∧ (𝑏 ∈ (0..^5) ∧ 𝑦 ∈ (0..^5))) ∧ {𝐾, ⟨0, 𝑏⟩} ∈ 𝐸) → ¬ {⟨0, 𝑏⟩, 𝐿} ∈ 𝐸)
Theorem	pgnbgreunbgrlem2 48440*	Lemma 2 for pgnbgreunbgr 48448. Impossible cases. (Contributed by AV, 18-Nov-2025.)
⊢ 𝐺 = (5 gPetersenGr 2)    &   ⊢ 𝑉 = (Vtx‘𝐺)    &   ⊢ 𝐸 = (Edg‘𝐺)    &   ⊢ 𝑁 = (𝐺 NeighbVtx 𝑋)    ⇒   ⊢ ((𝐿 = ⟨1, (((2nd ‘𝑋) + 2) mod 5)⟩ ∨ 𝐿 = ⟨0, (2nd ‘𝑋)⟩ ∨ 𝐿 = ⟨1, (((2nd ‘𝑋) − 2) mod 5)⟩) → ((𝐾 = ⟨1, (((2nd ‘𝑋) + 2) mod 5)⟩ ∨ 𝐾 = ⟨0, (2nd ‘𝑋)⟩ ∨ 𝐾 = ⟨1, (((2nd ‘𝑋) − 2) mod 5)⟩) → ((𝑋 = ⟨1, 𝑦⟩ ∧ 𝑋 ∈ 𝑉) → ((𝐾 ≠ 𝐿 ∧ (𝑏 ∈ (0..^5) ∧ 𝑦 ∈ (0..^5))) → (({𝐾, ⟨0, 𝑏⟩} ∈ 𝐸 ∧ {⟨0, 𝑏⟩, 𝐿} ∈ 𝐸) → 𝑋 = ⟨0, 𝑏⟩)))))
Theorem	pgnbgreunbgrlem3 48441	Lemma 3 for pgnbgreunbgr 48448. (Contributed by AV, 18-Nov-2025.)
⊢ 𝐺 = (5 gPetersenGr 2)    &   ⊢ 𝑉 = (Vtx‘𝐺)    &   ⊢ 𝐸 = (Edg‘𝐺)    &   ⊢ 𝑁 = (𝐺 NeighbVtx 𝑋)    ⇒   ⊢ (((𝐾 ∈ 𝑁 ∧ 𝐿 ∈ 𝑁 ∧ 𝐾 ≠ 𝐿) ∧ 𝑏 ∈ (0..^5)) → (({𝐾, ⟨0, 𝑏⟩} ∈ 𝐸 ∧ {⟨0, 𝑏⟩, 𝐿} ∈ 𝐸) → 𝑋 = ⟨0, 𝑏⟩))
Theorem	pgnbgreunbgrlem4 48442*	Lemma 4 for pgnbgreunbgr 48448. (Contributed by AV, 20-Nov-2025.)
⊢ 𝐺 = (5 gPetersenGr 2)    &   ⊢ 𝑉 = (Vtx‘𝐺)    &   ⊢ 𝐸 = (Edg‘𝐺)    &   ⊢ 𝑁 = (𝐺 NeighbVtx 𝑋)    ⇒   ⊢ ((𝐿 = ⟨1, (((2nd ‘𝑋) + 2) mod 5)⟩ ∨ 𝐿 = ⟨0, (2nd ‘𝑋)⟩ ∨ 𝐿 = ⟨1, (((2nd ‘𝑋) − 2) mod 5)⟩) → ((𝐾 = ⟨1, (((2nd ‘𝑋) + 2) mod 5)⟩ ∨ 𝐾 = ⟨0, (2nd ‘𝑋)⟩ ∨ 𝐾 = ⟨1, (((2nd ‘𝑋) − 2) mod 5)⟩) → ((𝑋 ∈ 𝑉 ∧ 𝑋 = ⟨1, 𝑦⟩) → ((𝐾 ≠ 𝐿 ∧ (𝑏 ∈ (0..^5) ∧ 𝑦 ∈ (0..^5))) → (({𝐾, ⟨1, 𝑏⟩} ∈ 𝐸 ∧ {⟨1, 𝑏⟩, 𝐿} ∈ 𝐸) → 𝑋 = ⟨1, 𝑏⟩)))))
Theorem	pgnbgreunbgrlem5lem1 48443*	Lemma 1 for pgnbgreunbgrlem5 48446. (Contributed by AV, 21-Nov-2025.)
⊢ 𝐺 = (5 gPetersenGr 2)    &   ⊢ 𝑉 = (Vtx‘𝐺)    &   ⊢ 𝐸 = (Edg‘𝐺)    &   ⊢ 𝑁 = (𝐺 NeighbVtx 𝑋)    ⇒   ⊢ ((((𝐿 = ⟨0, ((𝑦 + 1) mod 5)⟩ ∧ 𝐾 = ⟨1, 𝑦⟩) ∧ (𝑏 ∈ (0..^5) ∧ 𝑦 ∈ (0..^5))) ∧ {𝐾, ⟨1, 𝑏⟩} ∈ 𝐸) → ¬ {⟨1, 𝑏⟩, 𝐿} ∈ 𝐸)
Theorem	pgnbgreunbgrlem5lem2 48444*	Lemma 2 for pgnbgreunbgrlem5 48446. (Contributed by AV, 20-Nov-2025.)
⊢ 𝐺 = (5 gPetersenGr 2)    &   ⊢ 𝑉 = (Vtx‘𝐺)    &   ⊢ 𝐸 = (Edg‘𝐺)    &   ⊢ 𝑁 = (𝐺 NeighbVtx 𝑋)    ⇒   ⊢ ((((𝐿 = ⟨0, ((𝑦 − 1) mod 5)⟩ ∧ 𝐾 = ⟨1, 𝑦⟩) ∧ (𝑏 ∈ (0..^5) ∧ 𝑦 ∈ (0..^5))) ∧ {𝐾, ⟨1, 𝑏⟩} ∈ 𝐸) → ¬ {⟨1, 𝑏⟩, 𝐿} ∈ 𝐸)
Theorem	pgnbgreunbgrlem5lem3 48445*	Lemma 3 for pgnbgreunbgrlem5 48446. (Contributed by AV, 20-Nov-2025.)
⊢ 𝐺 = (5 gPetersenGr 2)    &   ⊢ 𝑉 = (Vtx‘𝐺)    &   ⊢ 𝐸 = (Edg‘𝐺)    &   ⊢ 𝑁 = (𝐺 NeighbVtx 𝑋)    ⇒   ⊢ ((((𝐿 = ⟨0, ((𝑦 + 1) mod 5)⟩ ∧ 𝐾 = ⟨0, ((𝑦 − 1) mod 5)⟩) ∧ (𝑏 ∈ (0..^5) ∧ 𝑦 ∈ (0..^5))) ∧ {𝐾, ⟨1, 𝑏⟩} ∈ 𝐸) → ¬ {⟨1, 𝑏⟩, 𝐿} ∈ 𝐸)
Theorem	pgnbgreunbgrlem5 48446*	Lemma 5 for pgnbgreunbgr 48448. Impossible cases. (Contributed by AV, 21-Nov-2025.)
⊢ 𝐺 = (5 gPetersenGr 2)    &   ⊢ 𝑉 = (Vtx‘𝐺)    &   ⊢ 𝐸 = (Edg‘𝐺)    &   ⊢ 𝑁 = (𝐺 NeighbVtx 𝑋)    ⇒   ⊢ ((𝐿 = ⟨0, (((2nd ‘𝑋) + 1) mod 5)⟩ ∨ 𝐿 = ⟨1, (2nd ‘𝑋)⟩ ∨ 𝐿 = ⟨0, (((2nd ‘𝑋) − 1) mod 5)⟩) → ((𝐾 = ⟨0, (((2nd ‘𝑋) + 1) mod 5)⟩ ∨ 𝐾 = ⟨1, (2nd ‘𝑋)⟩ ∨ 𝐾 = ⟨0, (((2nd ‘𝑋) − 1) mod 5)⟩) → ((𝑋 = ⟨0, 𝑦⟩ ∧ 𝑋 ∈ 𝑉) → ((𝐾 ≠ 𝐿 ∧ (𝑏 ∈ (0..^5) ∧ 𝑦 ∈ (0..^5))) → (({𝐾, ⟨1, 𝑏⟩} ∈ 𝐸 ∧ {⟨1, 𝑏⟩, 𝐿} ∈ 𝐸) → 𝑋 = ⟨1, 𝑏⟩)))))
Theorem	pgnbgreunbgrlem6 48447	Lemma 6 for pgnbgreunbgr 48448. (Contributed by AV, 20-Nov-2025.)
⊢ 𝐺 = (5 gPetersenGr 2)    &   ⊢ 𝑉 = (Vtx‘𝐺)    &   ⊢ 𝐸 = (Edg‘𝐺)    &   ⊢ 𝑁 = (𝐺 NeighbVtx 𝑋)    ⇒   ⊢ (((𝐾 ∈ 𝑁 ∧ 𝐿 ∈ 𝑁 ∧ 𝐾 ≠ 𝐿) ∧ 𝑏 ∈ (0..^5)) → (({𝐾, ⟨1, 𝑏⟩} ∈ 𝐸 ∧ {⟨1, 𝑏⟩, 𝐿} ∈ 𝐸) → 𝑋 = ⟨1, 𝑏⟩))
Theorem	pgnbgreunbgr 48448*	In a Petersen graph, two different neighbors of a vertex have exactly one common neighbor, which is the vertex itself. (Contributed by AV, 9-Nov-2025.)
⊢ 𝐺 = (5 gPetersenGr 2)    &   ⊢ 𝑉 = (Vtx‘𝐺)    &   ⊢ 𝐸 = (Edg‘𝐺)    &   ⊢ 𝑁 = (𝐺 NeighbVtx 𝑋)    ⇒   ⊢ ((𝐾 ∈ 𝑁 ∧ 𝐿 ∈ 𝑁 ∧ 𝐾 ≠ 𝐿) → ∃!𝑥 ∈ 𝑉 {{𝐾, 𝑥}, {𝑥, 𝐿}} ⊆ 𝐸)
Theorem	pgn4cyclex 48449	A cycle in a Petersen graph G(5,2) does not have length 4. (Contributed by AV, 9-Nov-2025.)
⊢ 𝐺 = (5 gPetersenGr 2)    ⇒   ⊢ (𝐹(Cycles‘𝐺)𝑃 → (♯‘𝐹) ≠ 4)
Theorem	pg4cyclnex 48450	In the Petersen graph G(5,2), there is no cycle of length 4. (Contributed by AV, 22-Nov-2025.)
⊢ ¬ ∃𝑝∃𝑓(𝑓(Cycles‘(5 gPetersenGr 2))𝑝 ∧ (♯‘𝑓) = 4)
Theorem	gpg5ngric 48451	The two generalized Petersen graphs G(5,K) of order 10, which are the Petersen graph G(5,2) and the 5-prism G(5,1), are not isomorphic. (Contributed by AV, 22-Nov-2025.)
⊢ ¬ (5 gPetersenGr 1) ≃𝑔𝑟 (5 gPetersenGr 2)
Theorem	lgricngricex 48452*	There are two different locally isomorphic graphs which are not isomorphic. (Contributed by AV, 23-Nov-2025.)
⊢ ∃𝑔∃ℎ(𝑔 ≃𝑙𝑔𝑟 ℎ ∧ ¬ 𝑔 ≃𝑔𝑟 ℎ)
Theorem	gpg5edgnedg 48453	Two consecutive (according to the numbering) inside vertices of the Petersen graph G(5,2) are not connected by an edge, but are connected by an edge in a 5-prism G(5,1). (Contributed by AV, 29-Dec-2025.)
⊢ ({⟨1, 0⟩, ⟨1, 1⟩} ∈ (Edg‘(5 gPetersenGr 1)) ∧ {⟨1, 0⟩, ⟨1, 1⟩} ∉ (Edg‘(5 gPetersenGr 2)))
Theorem	grlimedgnedg 48454*	In general, the image of an edge of a graph by a local isomprphism is not an edge of the other graph, proven by an example (see gpg5edgnedg 48453). This theorem proves that the analogon (((𝐺 ∈ USPGraph ∧ 𝐻 ∈ USPGraph) ∧ (𝐹 ∈ (𝐺 GraphLocIso 𝐻) ∧ 𝐾 ∈ 𝐼)) → (𝐹 “ 𝐾) ∈ 𝐸) of grimedgi 48259 for ordinarily isomorphic graphs does not hold in general. (Contributed by AV, 30-Dec-2025.)
⊢ ∃𝑔 ∈ USGraph ∃ℎ ∈ USGraph ∃𝑓 ∈ (𝑔 GraphLocIso ℎ)∃𝑎 ∈ (Vtx‘𝑔)∃𝑏 ∈ (Vtx‘𝑔)({𝑎, 𝑏} ∈ (Edg‘𝑔) ∧ {(𝑓‘𝑎), (𝑓‘𝑏)} ∉ (Edg‘ℎ))
21.48.15.9  Loop-free graphs - extension
Theorem	1hegrlfgr 48455*	A graph 𝐺 with one hyperedge joining at least two vertices is a loop-free graph. (Contributed by AV, 23-Feb-2021.)
⊢ (𝜑 → 𝐴 ∈ 𝑋)    &   ⊢ (𝜑 → 𝐵 ∈ 𝑉)    &   ⊢ (𝜑 → 𝐶 ∈ 𝑉)    &   ⊢ (𝜑 → 𝐵 ≠ 𝐶)    &   ⊢ (𝜑 → 𝐸 ∈ 𝒫 𝑉)    &   ⊢ (𝜑 → (iEdg‘𝐺) = {⟨𝐴, 𝐸⟩})    &   ⊢ (𝜑 → {𝐵, 𝐶} ⊆ 𝐸)    ⇒   ⊢ (𝜑 → (iEdg‘𝐺):{𝐴}⟶{𝑥 ∈ 𝒫 𝑉 ∣ 2 ≤ (♯‘𝑥)})
21.48.15.10  Walks - extension
Syntax	cupwlks 48456	Extend class notation with walks (of a pseudograph).
class UPWalks
Definition	df-upwlks 48457*	Define the set of all walks (in a pseudograph), called "simple walks" in the following. According to Wikipedia ("Path (graph theory)", https://en.wikipedia.org/wiki/Path_(graph_theory), 3-Oct-2017): "A walk of length k in a graph is an alternating sequence of vertices and edges, v0 , e0 , v1 , e1 , v2 , ... , v(k-1) , e(k-1) , v(k) which begins and ends with vertices. If the graph is undirected, then the endpoints of e(i) are v(i) and v(i+1)." According to Bollobas: " A walk W in a graph is an alternating sequence of vertices and edges x0 , e1 , x1 , e2 , ... , e(l) , x(l) where e(i) = x(i-1)x(i), 0<i<=l.", see Definition of [Bollobas] p. 4. Therefore, a walk can be represented by two mappings f from { 1 , ... , n } and p from { 0 , ... , n }, where f enumerates the (indices of the) edges, and p enumerates the vertices. So the walk is represented by the following sequence: p(0) e(f(1)) p(1) e(f(2)) ... p(n-1) e(f(n)) p(n). Although this definition is also applicable for arbitrary hypergraphs, it allows only walks consisting of not proper hyperedges (i.e. edges connecting at most two vertices). Therefore, it should be used for pseudographs only. (Contributed by Alexander van der Vekens and Mario Carneiro, 4-Oct-2017.) (Revised by AV, 28-Dec-2020.)
⊢ UPWalks = (𝑔 ∈ V ↦ {⟨𝑓, 𝑝⟩ ∣ (𝑓 ∈ Word dom (iEdg‘𝑔) ∧ 𝑝:(0...(♯‘𝑓))⟶(Vtx‘𝑔) ∧ ∀𝑘 ∈ (0..^(♯‘𝑓))((iEdg‘𝑔)‘(𝑓‘𝑘)) = {(𝑝‘𝑘), (𝑝‘(𝑘 + 1))})})
Theorem	upwlksfval 48458*	The set of simple walks (in an undirected graph). (Contributed by Alexander van der Vekens, 19-Oct-2017.) (Revised by AV, 28-Dec-2020.)
⊢ 𝑉 = (Vtx‘𝐺)    &   ⊢ 𝐼 = (iEdg‘𝐺)    ⇒   ⊢ (𝐺 ∈ 𝑊 → (UPWalks‘𝐺) = {⟨𝑓, 𝑝⟩ ∣ (𝑓 ∈ Word dom 𝐼 ∧ 𝑝:(0...(♯‘𝑓))⟶𝑉 ∧ ∀𝑘 ∈ (0..^(♯‘𝑓))(𝐼‘(𝑓‘𝑘)) = {(𝑝‘𝑘), (𝑝‘(𝑘 + 1))})})
Theorem	isupwlk 48459*	Properties of a pair of functions to be a simple walk. (Contributed by Alexander van der Vekens, 20-Oct-2017.) (Revised by AV, 28-Dec-2020.)
⊢ 𝑉 = (Vtx‘𝐺)    &   ⊢ 𝐼 = (iEdg‘𝐺)    ⇒   ⊢ ((𝐺 ∈ 𝑊 ∧ 𝐹 ∈ 𝑈 ∧ 𝑃 ∈ 𝑍) → (𝐹(UPWalks‘𝐺)𝑃 ↔ (𝐹 ∈ Word dom 𝐼 ∧ 𝑃:(0...(♯‘𝐹))⟶𝑉 ∧ ∀𝑘 ∈ (0..^(♯‘𝐹))(𝐼‘(𝐹‘𝑘)) = {(𝑃‘𝑘), (𝑃‘(𝑘 + 1))})))
Theorem	isupwlkg 48460*	Generalization of isupwlk 48459: Conditions for two classes to represent a simple walk. (Contributed by AV, 5-Nov-2021.)
⊢ 𝑉 = (Vtx‘𝐺)    &   ⊢ 𝐼 = (iEdg‘𝐺)    ⇒   ⊢ (𝐺 ∈ 𝑊 → (𝐹(UPWalks‘𝐺)𝑃 ↔ (𝐹 ∈ Word dom 𝐼 ∧ 𝑃:(0...(♯‘𝐹))⟶𝑉 ∧ ∀𝑘 ∈ (0..^(♯‘𝐹))(𝐼‘(𝐹‘𝑘)) = {(𝑃‘𝑘), (𝑃‘(𝑘 + 1))})))
Theorem	upwlkbprop 48461	Basic properties of a simple walk. (Contributed by Alexander van der Vekens, 31-Oct-2017.) (Revised by AV, 29-Dec-2020.)
⊢ 𝑉 = (Vtx‘𝐺)    &   ⊢ 𝐼 = (iEdg‘𝐺)    ⇒   ⊢ (𝐹(UPWalks‘𝐺)𝑃 → (𝐺 ∈ V ∧ 𝐹 ∈ V ∧ 𝑃 ∈ V))
Theorem	upwlkwlk 48462	A simple walk is a walk. (Contributed by AV, 30-Dec-2020.) (Proof shortened by AV, 27-Feb-2021.)
⊢ (𝐹(UPWalks‘𝐺)𝑃 → 𝐹(Walks‘𝐺)𝑃)
Theorem	upgrwlkupwlk 48463	In a pseudograph, a walk is a simple walk. (Contributed by AV, 30-Dec-2020.) (Proof shortened by AV, 2-Jan-2021.)
⊢ ((𝐺 ∈ UPGraph ∧ 𝐹(Walks‘𝐺)𝑃) → 𝐹(UPWalks‘𝐺)𝑃)
Theorem	upgrwlkupwlkb 48464	In a pseudograph, the definitions for a walk and a simple walk are equivalent. (Contributed by AV, 30-Dec-2020.)
⊢ (𝐺 ∈ UPGraph → (𝐹(Walks‘𝐺)𝑃 ↔ 𝐹(UPWalks‘𝐺)𝑃))
Theorem	upgrisupwlkALT 48465*	Alternate proof of upgriswlk 29719 using the definition of UPGraph and related theorems. (Contributed by AV, 2-Jan-2021.) (Proof modification is discouraged.) (New usage is discouraged.)
⊢ 𝑉 = (Vtx‘𝐺)    &   ⊢ 𝐼 = (iEdg‘𝐺)    ⇒   ⊢ ((𝐺 ∈ UPGraph ∧ 𝐹 ∈ 𝑈 ∧ 𝑃 ∈ 𝑍) → (𝐹(Walks‘𝐺)𝑃 ↔ (𝐹 ∈ Word dom 𝐼 ∧ 𝑃:(0...(♯‘𝐹))⟶𝑉 ∧ ∀𝑘 ∈ (0..^(♯‘𝐹))(𝐼‘(𝐹‘𝑘)) = {(𝑃‘𝑘), (𝑃‘(𝑘 + 1))})))
21.48.15.11  Edges of graphs expressed as sets of unordered pairs
Theorem	upgredgssspr 48466	The set of edges of a pseudograph is a subset of the set of unordered pairs of vertices. (Contributed by AV, 24-Nov-2021.)
⊢ (𝐺 ∈ UPGraph → (Edg‘𝐺) ⊆ (Pairs‘(Vtx‘𝐺)))
Theorem	uspgropssxp 48467*	The set 𝐺 of "simple pseudographs" for a fixed set 𝑉 of vertices is a subset of a Cartesian product. For more details about the class 𝐺 of all "simple pseudographs" see comments on uspgrbisymrel 48477. (Contributed by AV, 24-Nov-2021.)
⊢ 𝑃 = 𝒫 (Pairs‘𝑉)    &   ⊢ 𝐺 = {⟨𝑣, 𝑒⟩ ∣ (𝑣 = 𝑉 ∧ ∃𝑞 ∈ USPGraph ((Vtx‘𝑞) = 𝑣 ∧ (Edg‘𝑞) = 𝑒))}    ⇒   ⊢ (𝑉 ∈ 𝑊 → 𝐺 ⊆ (𝑊 × 𝑃))
Theorem	uspgrsprfv 48468*	The value of the function 𝐹 which maps a "simple pseudograph" for a fixed set 𝑉 of vertices to the set of edges (i.e. range of the edge function) of the graph. Solely for 𝐺 as defined here, the function 𝐹 is a bijection between the "simple pseudographs" and the subsets of the set of pairs 𝑃 over the fixed set 𝑉 of vertices, see uspgrbispr 48474. (Contributed by AV, 24-Nov-2021.)
⊢ 𝑃 = 𝒫 (Pairs‘𝑉)    &   ⊢ 𝐺 = {⟨𝑣, 𝑒⟩ ∣ (𝑣 = 𝑉 ∧ ∃𝑞 ∈ USPGraph ((Vtx‘𝑞) = 𝑣 ∧ (Edg‘𝑞) = 𝑒))}    &   ⊢ 𝐹 = (𝑔 ∈ 𝐺 ↦ (2nd ‘𝑔))    ⇒   ⊢ (𝑋 ∈ 𝐺 → (𝐹‘𝑋) = (2nd ‘𝑋))
Theorem	uspgrsprf 48469*	The mapping 𝐹 is a function from the "simple pseudographs" with a fixed set of vertices 𝑉 into the subsets of the set of pairs over the set 𝑉. (Contributed by AV, 24-Nov-2021.)
⊢ 𝑃 = 𝒫 (Pairs‘𝑉)    &   ⊢ 𝐺 = {⟨𝑣, 𝑒⟩ ∣ (𝑣 = 𝑉 ∧ ∃𝑞 ∈ USPGraph ((Vtx‘𝑞) = 𝑣 ∧ (Edg‘𝑞) = 𝑒))}    &   ⊢ 𝐹 = (𝑔 ∈ 𝐺 ↦ (2nd ‘𝑔))    ⇒   ⊢ 𝐹:𝐺⟶𝑃
Theorem	uspgrsprf1 48470*	The mapping 𝐹 is a one-to-one function from the "simple pseudographs" with a fixed set of vertices 𝑉 into the subsets of the set of pairs over the set 𝑉. (Contributed by AV, 25-Nov-2021.)
⊢ 𝑃 = 𝒫 (Pairs‘𝑉)    &   ⊢ 𝐺 = {⟨𝑣, 𝑒⟩ ∣ (𝑣 = 𝑉 ∧ ∃𝑞 ∈ USPGraph ((Vtx‘𝑞) = 𝑣 ∧ (Edg‘𝑞) = 𝑒))}    &   ⊢ 𝐹 = (𝑔 ∈ 𝐺 ↦ (2nd ‘𝑔))    ⇒   ⊢ 𝐹:𝐺–1-1→𝑃
Theorem	uspgrsprfo 48471*	The mapping 𝐹 is a function from the "simple pseudographs" with a fixed set of vertices 𝑉 onto the subsets of the set of pairs over the set 𝑉. (Contributed by AV, 25-Nov-2021.)
⊢ 𝑃 = 𝒫 (Pairs‘𝑉)    &   ⊢ 𝐺 = {⟨𝑣, 𝑒⟩ ∣ (𝑣 = 𝑉 ∧ ∃𝑞 ∈ USPGraph ((Vtx‘𝑞) = 𝑣 ∧ (Edg‘𝑞) = 𝑒))}    &   ⊢ 𝐹 = (𝑔 ∈ 𝐺 ↦ (2nd ‘𝑔))    ⇒   ⊢ (𝑉 ∈ 𝑊 → 𝐹:𝐺–onto→𝑃)
Theorem	uspgrsprf1o 48472*	The mapping 𝐹 is a bijection between the "simple pseudographs" with a fixed set of vertices 𝑉 and the subsets of the set of pairs over the set 𝑉. See also the comments on uspgrbisymrel 48477. (Contributed by AV, 25-Nov-2021.)
⊢ 𝑃 = 𝒫 (Pairs‘𝑉)    &   ⊢ 𝐺 = {⟨𝑣, 𝑒⟩ ∣ (𝑣 = 𝑉 ∧ ∃𝑞 ∈ USPGraph ((Vtx‘𝑞) = 𝑣 ∧ (Edg‘𝑞) = 𝑒))}    &   ⊢ 𝐹 = (𝑔 ∈ 𝐺 ↦ (2nd ‘𝑔))    ⇒   ⊢ (𝑉 ∈ 𝑊 → 𝐹:𝐺–1-1-onto→𝑃)
Theorem	uspgrex 48473*	The class 𝐺 of all "simple pseudographs" with a fixed set of vertices 𝑉 is a set. (Contributed by AV, 26-Nov-2021.)
⊢ 𝑃 = 𝒫 (Pairs‘𝑉)    &   ⊢ 𝐺 = {⟨𝑣, 𝑒⟩ ∣ (𝑣 = 𝑉 ∧ ∃𝑞 ∈ USPGraph ((Vtx‘𝑞) = 𝑣 ∧ (Edg‘𝑞) = 𝑒))}    ⇒   ⊢ (𝑉 ∈ 𝑊 → 𝐺 ∈ V)
Theorem	uspgrbispr 48474*	There is a bijection between the "simple pseudographs" with a fixed set of vertices 𝑉 and the subsets of the set of pairs over the set 𝑉. (Contributed by AV, 26-Nov-2021.)
⊢ 𝑃 = 𝒫 (Pairs‘𝑉)    &   ⊢ 𝐺 = {⟨𝑣, 𝑒⟩ ∣ (𝑣 = 𝑉 ∧ ∃𝑞 ∈ USPGraph ((Vtx‘𝑞) = 𝑣 ∧ (Edg‘𝑞) = 𝑒))}    ⇒   ⊢ (𝑉 ∈ 𝑊 → ∃𝑓 𝑓:𝐺–1-1-onto→𝑃)
Theorem	uspgrspren 48475*	The set 𝐺 of the "simple pseudographs" with a fixed set of vertices 𝑉 and the class 𝑃 of subsets of the set of pairs over the fixed set 𝑉 are equinumerous. (Contributed by AV, 27-Nov-2021.)
⊢ 𝑃 = 𝒫 (Pairs‘𝑉)    &   ⊢ 𝐺 = {⟨𝑣, 𝑒⟩ ∣ (𝑣 = 𝑉 ∧ ∃𝑞 ∈ USPGraph ((Vtx‘𝑞) = 𝑣 ∧ (Edg‘𝑞) = 𝑒))}    ⇒   ⊢ (𝑉 ∈ 𝑊 → 𝐺 ≈ 𝑃)
Theorem	uspgrymrelen 48476*	The set 𝐺 of the "simple pseudographs" with a fixed set of vertices 𝑉 and the class 𝑅 of the symmetric relations on the fixed set 𝑉 are equinumerous. For more details about the class 𝐺 of all "simple pseudographs" see comments on uspgrbisymrel 48477. (Contributed by AV, 27-Nov-2021.)
⊢ 𝐺 = {⟨𝑣, 𝑒⟩ ∣ (𝑣 = 𝑉 ∧ ∃𝑞 ∈ USPGraph ((Vtx‘𝑞) = 𝑣 ∧ (Edg‘𝑞) = 𝑒))}    &   ⊢ 𝑅 = {𝑟 ∈ 𝒫 (𝑉 × 𝑉) ∣ ∀𝑥 ∈ 𝑉 ∀𝑦 ∈ 𝑉 (𝑥𝑟𝑦 ↔ 𝑦𝑟𝑥)}    ⇒   ⊢ (𝑉 ∈ 𝑊 → 𝐺 ≈ 𝑅)
Theorem	uspgrbisymrel 48477*	There is a bijection between the "simple pseudographs" for a fixed set 𝑉 of vertices and the class 𝑅 of the symmetric relations on the fixed set 𝑉. The simple pseudographs, which are graphs without hyper- or multiedges, but which may contain loops, are expressed as ordered pairs of the vertices and the edges (as proper or improper unordered pairs of vertices, not as indexed edges!) in this theorem. That class 𝐺 of such simple pseudographs is a set (if 𝑉 is a set, see uspgrex 48473) of equivalence classes of graphs abstracting from the index sets of their edge functions. Solely for this abstraction, there is a bijection between the "simple pseudographs" as members of 𝐺 and the symmetric relations 𝑅 on the fixed set 𝑉 of vertices. This theorem would not hold for 𝐺 = {𝑔 ∈ USPGraph ∣ (Vtx‘𝑔) = 𝑉} and even not for 𝐺 = {⟨𝑣, 𝑒⟩ ∣ (𝑣 = 𝑉 ∧ ⟨𝑣, 𝑒⟩ ∈ USPGraph)}, because these are much bigger classes. (Proposed by Gerard Lang, 16-Nov-2021.) (Contributed by AV, 27-Nov-2021.)
⊢ 𝐺 = {⟨𝑣, 𝑒⟩ ∣ (𝑣 = 𝑉 ∧ ∃𝑞 ∈ USPGraph ((Vtx‘𝑞) = 𝑣 ∧ (Edg‘𝑞) = 𝑒))}    &   ⊢ 𝑅 = {𝑟 ∈ 𝒫 (𝑉 × 𝑉) ∣ ∀𝑥 ∈ 𝑉 ∀𝑦 ∈ 𝑉 (𝑥𝑟𝑦 ↔ 𝑦𝑟𝑥)}    ⇒   ⊢ (𝑉 ∈ 𝑊 → ∃𝑓 𝑓:𝐺–1-1-onto→𝑅)
Theorem	uspgrbisymrelALT 48478*	Alternate proof of uspgrbisymrel 48477 not using the definition of equinumerosity. (Contributed by AV, 26-Nov-2021.) (New usage is discouraged.) (Proof modification is discouraged.)
⊢ 𝐺 = {⟨𝑣, 𝑒⟩ ∣ (𝑣 = 𝑉 ∧ ∃𝑞 ∈ USPGraph ((Vtx‘𝑞) = 𝑣 ∧ (Edg‘𝑞) = 𝑒))}    &   ⊢ 𝑅 = {𝑟 ∈ 𝒫 (𝑉 × 𝑉) ∣ ∀𝑥 ∈ 𝑉 ∀𝑦 ∈ 𝑉 (𝑥𝑟𝑦 ↔ 𝑦𝑟𝑥)}    ⇒   ⊢ (𝑉 ∈ 𝑊 → ∃𝑓 𝑓:𝐺–1-1-onto→𝑅)
21.48.16  Monoids (extension)
21.48.16.1  Auxiliary theorems
Theorem	ovn0dmfun 48479	If a class operation value for two operands is not the empty set, then the operands are contained in the domain of the class, and the class restricted to the operands is a function, analogous to fvfundmfvn0 6875. (Contributed by AV, 27-Jan-2020.)
⊢ ((𝐴𝐹𝐵) ≠ ∅ → (⟨𝐴, 𝐵⟩ ∈ dom 𝐹 ∧ Fun (𝐹 ↾ {⟨𝐴, 𝐵⟩})))
Theorem	xpsnopab 48480*	A Cartesian product with a singleton expressed as ordered-pair class abstraction. (Contributed by AV, 27-Jan-2020.)
⊢ ({𝑋} × 𝐶) = {⟨𝑎, 𝑏⟩ ∣ (𝑎 = 𝑋 ∧ 𝑏 ∈ 𝐶)}
Theorem	xpiun 48481*	A Cartesian product expressed as indexed union of ordered-pair class abstractions. (Contributed by AV, 27-Jan-2020.)
⊢ (𝐵 × 𝐶) = ∪ 𝑥 ∈ 𝐵 {⟨𝑎, 𝑏⟩ ∣ (𝑎 = 𝑥 ∧ 𝑏 ∈ 𝐶)}
Theorem	ovn0ssdmfun 48482*	If a class' operation value for two operands is not the empty set, the operands are contained in the domain of the class, and the class restricted to the operands is a function, analogous to fvfundmfvn0 6875. (Contributed by AV, 27-Jan-2020.)
⊢ (∀𝑎 ∈ 𝐷 ∀𝑏 ∈ 𝐸 (𝑎𝐹𝑏) ≠ ∅ → ((𝐷 × 𝐸) ⊆ dom 𝐹 ∧ Fun (𝐹 ↾ (𝐷 × 𝐸))))
Theorem	fnxpdmdm 48483	The domain of the domain of a function over a Cartesian square. (Contributed by AV, 13-Jan-2020.)
⊢ (𝐹 Fn (𝐴 × 𝐴) → dom dom 𝐹 = 𝐴)
Theorem	cnfldsrngbas 48484	The base set of a subring of the field of complex numbers. (Contributed by AV, 31-Jan-2020.)
⊢ 𝑅 = (ℂfld ↾s 𝑆)    ⇒   ⊢ (𝑆 ⊆ ℂ → 𝑆 = (Base‘𝑅))
Theorem	cnfldsrngadd 48485	The group addition operation of a subring of the field of complex numbers. (Contributed by AV, 31-Jan-2020.)
⊢ 𝑅 = (ℂfld ↾s 𝑆)    ⇒   ⊢ (𝑆 ∈ 𝑉 → + = (+g‘𝑅))
Theorem	cnfldsrngmul 48486	The ring multiplication operation of a subring of the field of complex numbers. (Contributed by AV, 31-Jan-2020.)
⊢ 𝑅 = (ℂfld ↾s 𝑆)    ⇒   ⊢ (𝑆 ∈ 𝑉 → · = (.r‘𝑅))
21.48.16.2  Magmas, Semigroups and Monoids (extension)
Theorem	plusfreseq 48487	If the empty set is not contained in the range of the group addition function of an extensible structure (not necessarily a magma), the restriction of the addition operation to (the Cartesian square of) the base set is the functionalization of it. (Contributed by AV, 28-Jan-2020.)
⊢ 𝐵 = (Base‘𝑀)    &   ⊢ + = (+g‘𝑀)    &   ⊢ ⨣ = (+𝑓‘𝑀)    ⇒   ⊢ (∅ ∉ ran ⨣ → ( + ↾ (𝐵 × 𝐵)) = ⨣ )
Theorem	mgmplusfreseq 48488	If the empty set is not contained in the base set of a magma, the restriction of the addition operation to (the Cartesian square of) the base set is the functionalization of it. (Contributed by AV, 28-Jan-2020.)
⊢ 𝐵 = (Base‘𝑀)    &   ⊢ + = (+g‘𝑀)    &   ⊢ ⨣ = (+𝑓‘𝑀)    ⇒   ⊢ ((𝑀 ∈ Mgm ∧ ∅ ∉ 𝐵) → ( + ↾ (𝐵 × 𝐵)) = ⨣ )
Theorem	0mgm 48489	A set with an empty base set is always a magma. (Contributed by AV, 25-Feb-2020.)
⊢ (Base‘𝑀) = ∅    ⇒   ⊢ (𝑀 ∈ 𝑉 → 𝑀 ∈ Mgm)
21.48.16.3  Examples and counterexamples for magmas, semigroups and monoids (extension)
Theorem	opmpoismgm 48490*	A structure with a group addition operation in maps-to notation is a magma if the operation value is contained in the base set. (Contributed by AV, 16-Feb-2020.)
⊢ 𝐵 = (Base‘𝑀)    &   ⊢ (+g‘𝑀) = (𝑥 ∈ 𝐵, 𝑦 ∈ 𝐵 ↦ 𝐶)    &   ⊢ (𝜑 → 𝐵 ≠ ∅)    &   ⊢ ((𝜑 ∧ (𝑥 ∈ 𝐵 ∧ 𝑦 ∈ 𝐵)) → 𝐶 ∈ 𝐵)    ⇒   ⊢ (𝜑 → 𝑀 ∈ Mgm)
Theorem	copissgrp 48491*	A structure with a constant group addition operation is a semigroup if the constant is contained in the base set. (Contributed by AV, 16-Feb-2020.)
⊢ 𝐵 = (Base‘𝑀)    &   ⊢ (+g‘𝑀) = (𝑥 ∈ 𝐵, 𝑦 ∈ 𝐵 ↦ 𝐶)    &   ⊢ (𝜑 → 𝐵 ≠ ∅)    &   ⊢ (𝜑 → 𝐶 ∈ 𝐵)    ⇒   ⊢ (𝜑 → 𝑀 ∈ Smgrp)
Theorem	copisnmnd 48492*	A structure with a constant group addition operation and at least two elements is not a monoid. (Contributed by AV, 16-Feb-2020.)
⊢ 𝐵 = (Base‘𝑀)    &   ⊢ (+g‘𝑀) = (𝑥 ∈ 𝐵, 𝑦 ∈ 𝐵 ↦ 𝐶)    &   ⊢ (𝜑 → 𝐶 ∈ 𝐵)    &   ⊢ (𝜑 → 1 < (♯‘𝐵))    ⇒   ⊢ (𝜑 → 𝑀 ∉ Mnd)
Theorem	0nodd 48493*	0 is not an odd integer. (Contributed by AV, 3-Feb-2020.)
⊢ 𝑂 = {𝑧 ∈ ℤ ∣ ∃𝑥 ∈ ℤ 𝑧 = ((2 · 𝑥) + 1)}    ⇒   ⊢ 0 ∉ 𝑂
Theorem	1odd 48494*	1 is an odd integer. (Contributed by AV, 3-Feb-2020.)
⊢ 𝑂 = {𝑧 ∈ ℤ ∣ ∃𝑥 ∈ ℤ 𝑧 = ((2 · 𝑥) + 1)}    ⇒   ⊢ 1 ∈ 𝑂
Theorem	2nodd 48495*	2 is not an odd integer. (Contributed by AV, 3-Feb-2020.)
⊢ 𝑂 = {𝑧 ∈ ℤ ∣ ∃𝑥 ∈ ℤ 𝑧 = ((2 · 𝑥) + 1)}    ⇒   ⊢ 2 ∉ 𝑂
Theorem	oddibas 48496*	Lemma 1 for oddinmgm 48498: The base set of M is the set of all odd integers. (Contributed by AV, 3-Feb-2020.)
⊢ 𝑂 = {𝑧 ∈ ℤ ∣ ∃𝑥 ∈ ℤ 𝑧 = ((2 · 𝑥) + 1)}    &   ⊢ 𝑀 = (ℂfld ↾s 𝑂)    ⇒   ⊢ 𝑂 = (Base‘𝑀)
Theorem	oddiadd 48497*	Lemma 2 for oddinmgm 48498: The group addition operation of M is the addition of complex numbers. (Contributed by AV, 3-Feb-2020.)
⊢ 𝑂 = {𝑧 ∈ ℤ ∣ ∃𝑥 ∈ ℤ 𝑧 = ((2 · 𝑥) + 1)}    &   ⊢ 𝑀 = (ℂfld ↾s 𝑂)    ⇒   ⊢ + = (+g‘𝑀)
Theorem	oddinmgm 48498*	The structure of all odd integers together with the addition of complex numbers is not a magma. Remark: the structure of the complementary subset of the set of integers, the even integers, is a magma, actually an abelian group, see 2zrngaabl 48573, and even a non-unital ring, see 2zrng 48564. (Contributed by AV, 3-Feb-2020.)
⊢ 𝑂 = {𝑧 ∈ ℤ ∣ ∃𝑥 ∈ ℤ 𝑧 = ((2 · 𝑥) + 1)}    &   ⊢ 𝑀 = (ℂfld ↾s 𝑂)    ⇒   ⊢ 𝑀 ∉ Mgm
Theorem	nnsgrpmgm 48499	The structure of positive integers together with the addition of complex numbers is a magma. (Contributed by AV, 4-Feb-2020.)
⊢ 𝑀 = (ℂfld ↾s ℕ)    ⇒   ⊢ 𝑀 ∈ Mgm
Theorem	nnsgrp 48500	The structure of positive integers together with the addition of complex numbers is a semigroup. (Contributed by AV, 4-Feb-2020.)
⊢ 𝑀 = (ℂfld ↾s ℕ)    ⇒   ⊢ 𝑀 ∈ Smgrp