How statement and proof provenance work
The first chip identifies the source of the statement or construction; the second identifies the source of its local proof or verification.
- Literature-sourced: the exact statement appears in a cited source; only wording and notation differ.
- AI-adapted: a semantically identical restatement of literature-sourced material, modulo indexing, notation, and boundary cases adopted by the library.
- AI-generated: a genuinely novel statement formulated by AI, with no source for the claim itself.
These labels describe origin, not correctness: citations and verification chips remain separate evidence.
Bell congruence worked: internal material length gamma(t)L and constant chart separation
Example
Worked computation of the internal material length for the Bell congruence of Fermi-Walker transport preserves the metric, and explicit rigid and non-rigid observer congruences (d) and the material metric of The material metric of a congruence: evolution of rest separations and preservation of the internal metric under Born rigidity. Fix and , let , put on and let for in an open interval containing , , in the inertial chart with . Then on the two-sided domain ; write and .
(a) The translated congruence field is and the material field is the constant ; since , the -length of is (The material metric of a congruence: evolution of rest separations and preservation of the internal metric under Born rigidity (a), Fermi-Walker transport preserves the metric, and explicit rigid and non-rigid observer congruences (d)). Hence the internal longitudinal material-metric length between labels and is for every , with minimum at , while the chart-frame separation is for every in .
(b) The longitudinal expansion of the translated congruence is , with unit rest vector (Fermi-Walker transport preserves the metric, and explicit rigid and non-rigid observer congruences (d)); it vanishes at and is nonzero for every , negative for and positive for . By The material metric of a congruence: evolution of rest separations and preservation of the internal metric under Born rigidity (b) the internal longitudinal material metric component is and its derivatives in geometric proper length are and ; with horizontal unit direction , equivalently the fractional rate of change of the rest separation per unit proper time is , and .
(c) Explicit check at , i.e. in : , and and are not needed; the rest separation is , the internal metric component is , the expansion is , and using [L7], the fractional rest-separation rate is . At the rest separation takes its minimum and the expansion vanishes; the domain is the two-sided interval , so both the decelerating branch (negative expansion) and the accelerating branch (positive expansion) are included.
(d) Scope. The length is the integral of the local rest metric over the material-label segment at common flow parameter; no finite endpoint-hyperplane distance is inferred. The computation is exact kinematics of the specified family: it uses no elasticity, no material failure criterion, no force law, no measurement and no empirical claim, and it draws no conclusion about real threads; no choice principle is used.
Facts & Assumptions
Given: , , , on , , an open label interval containing , an inertial chart with , the worldlines , and , .
Model and chart: with coordinate identification and in the orthonormal frame (Oriented time-oriented affine Minkowski space (the spacetime primitives), Inertial frames and inertial charts of the affine Minkowski model).
Derivatives: , , and the chain rule plus the total chain rule differentiate composites of the data functions (The derivative of at a point that is a limit point of , and differentiability on a set, The chain rule, in one line from Carathéodory: if is differentiable at and is differentiable at , then is differentiable at with , The chain rule for total derivatives: ).
Translated-congruence first-order data: the unit field is , the unit longitudinal rest vector is , and , nonzero exactly where (Fermi-Walker transport preserves the metric, and explicit rigid and non-rigid observer congruences (d), Kinematics of an observer congruence: acceleration, expansion, shear, vorticity and Born rigidity (c)).
Material metric: for an injective immersion with and material directions , and , i.e. with ; kills the -component, so when (The material metric of a congruence: evolution of rest separations and preservation of the internal metric under Born rigidity (a),(b),(d)).
Rest form: for the first-order rest projection (Kinematics of an observer congruence: acceleration, expansion, shear, vorticity and Born rigidity (a), The material metric of a congruence: evolution of rest separations and preservation of the internal metric under Born rigidity).
Proper time and four-velocity: the flow lines have four-velocity with , and the flow parameter satisfies for the proper time , with and iff (Four-velocity and four-acceleration of a future timelike worldline, Norms of four-velocity and four-acceleration, and the observer rest-space decomposition (a),(d), Proper time along a future timelike worldline, The proper-time function is a strictly increasing C^1 parametrization with C^1 inverse).
The natural logarithm is defined on positive real numbers and has derivative (The natural logarithm as the inverse of the exponential function, The natural logarithm has derivative 1/x and equals the integral from 1 to x of 1/t); hence by [L2]. This is the fractional rate of for constant .
Verification
(Basic data.) On one has and by [L2], so exactly on the stated two-sided domain, and ; hence is well defined and positive, and .
(The unit field and the material direction.) To realize the hypotheses of [L4], let and . By [L6] its inverse is with ; the smooth data bootstrap this inverse to smoothness. The map on the open product of the parameter image, the stated label interval and has the explicit inverse , so is an injective smooth immersion onto an open set; its flow derivative is . By [L3] the translated congruence field is , and the material direction is ; then , and by [L5] the rest form of is , while is the horizontal unit rest vector of [L3].
(Clause (a): the material length.) By step 2.1 the -length of is , so the internal longitudinal material-metric length between labels and at common flow parameter is by [L4]; since for by step 1.1 and [L6], this exceeds for every and equals only at (where ). The chart separation is for every .
(Clause (b): the expansion and the metric component.) By [L3] the longitudinal expansion is , which vanishes at and has the sign of elsewhere because ; and by step 2.1, .
(Clause (b): the rates.) By [L4], and ; since by [L4] and step 2.1, using [L7], the fractional rest-separation rate is , and multiplying by gives .
(Clause (c): the numerical check.) At : and ; the rest separation is and the metric component is by steps 2.1 and 3.2; the expansion is , and the fractional rate is by step 4.1. At the separation is and the expansion vanishes, and the two-sided domain contains both signs of , hence both signs of the expansion.
(Clause (d): scope.) Everything computed is the material-label integral of the rest metric at common flow parameter, with its exact local rates; no endpoint distance on a single simultaneity hyperplane, no elasticity, failure criterion, force law, measurement or empirical claim enters, and every step is finite-dimensional algebra or calculus from the cited suppliers, so no choice principle is used.
Depends on
The material metric of a congruence: evolution of rest separations and preservation of the internal metric under Born rigidity
Fermi-Walker transport preserves the metric, and explicit rigid and non-rigid observer congruences
Kinematics of an observer congruence: acceleration, expansion, shear, vorticity and Born rigidity
Four-velocity and four-acceleration of a future timelike worldline
Norms of four-velocity and four-acceleration, and the observer rest-space decomposition
Inertial frames and inertial charts of the affine Minkowski model
Oriented time-oriented affine Minkowski space (the spacetime primitives)
The chain rule, in one line from Carathéodory: if is differentiable at and is differentiable at , then is differentiable at with
The derivative of at a point that is a limit point of , and differentiability on a set
The proper-time function is a strictly increasing C^1 parametrization with C^1 inverse
Proper time along a future timelike worldline
The chain rule for total derivatives:
The natural logarithm as the inverse of the exponential function
The natural logarithm has derivative 1/x and equals the integral from 1 to x of 1/t
Dependency tree · 2 levels
Sources
- B. Crowell, Special Relativity, revision 2020-12-10 (author-published undergraduate textbook, 246 PDF pages): Section 3.9.2 pp. 70-72 and Section 9.5.2 pp. 206-207 (Bell's translated rockets, the constant spacing in the launch frame, the expansion and the stretching of the thread); signature (+---) converted to (-+++), c = 1 formulas restored to x^0 = c t
- D. Giulini, 'Algebraic and geometric structures of Special Relativity', arXiv:math-ph/0602018v2: Section 5.5 pp. 41-49 (Born rigidity and the evolution of the rest metric of a congruence); signature (+---) converted to (-+++), u^2 = c^2 converted to eta(n,n) = -1