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.
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These labels describe origin, not correctness: citations and verification chips remain separate evidence.
Worked reverse Cauchy-Schwarz and reverse triangle inequalities
Example
Worked computation in the chart of an inertial frame with ; the vectors below are coordinate columns in the frame's basis.
(a) For and one has , so the timelike lengths are each, and , so ; the inequality is strict because and are not positive proportional.
(b) For one has and , while , so : this is the equality case of the reversed Cauchy-Schwarz inequality, attained by the positive proportional pair .
(c) Reverse triangle: has , so its root is , again strict because and are not positive proportional. For , of timelike length , one has and with , since .
(d) Each of , , and is future timelike (, , and in the first coordinate against the spatial norm), so all inequalities above are instances of the future timelike hypotheses of The reversed Cauchy-Schwarz inequality for future timelike vectors and The reversed triangle inequality and convexity of the future timelike cone.
Facts & Assumptions
Given: An inertial frame with chart and , and the coordinate vectors , , , (Inertial frames and inertial charts of the affine Minkowski model).
Pairing in the frame: for coordinate vectors (Inertial frames and inertial charts of the affine Minkowski model, Lorentz forms of inertia (3,1,0) on a 4-dimensional real vector space).
Causal classification and cone coordinates: is timelike when , and in a frame with future first vector is future timelike exactly when with (Timelike, null, spacelike and causal vectors of a Lorentz vector space, The timelike set has exactly two convex components, described in orthonormal coordinates).
Reversed Cauchy-Schwarz inequality: for future timelike with , one has , with equality exactly when and are positive proportional (The reversed Cauchy-Schwarz inequality for future timelike vectors).
Reversed triangle inequality: for future timelike one has future timelike and , with equality exactly when and are positive proportional (The reversed triangle inequality and convexity of the future timelike cone).
Square roots and monotonicity: every real has a unique with , so in particular ; for one has (Square roots exist: a unique with ; the positives are , Squaring is monotone on the nonnegatives).
Elementary order arithmetic in : the order is trichotomous and transitive (Ordered field).
Verification
Evaluating the diagonal form [L1] on the given coordinate vectors gives , , , , , , , and .
By [L2] each of the four vectors is future timelike: , , and ; this is (d).
For (a): by [L5], so the right-hand side is , while ; the pair is not positive proportional, since would give from the first coordinates and then , a contradiction, and fails the same way; hence the strict clause of [L3] gives , as claimed.
For (b): with , so the pair is positive proportional; by the equality case of [L3] applied to the future timelike pair one gets , and the values of step 1.1 give and , the displayed equality.
For (c): the sum has the coordinate column , so and by [L5], and [L4] gives ; equality would force and positive proportional by [L4], which step 3.1 excludes, so the inequality is strict. Similarly with strictness by [L3] since and are not positive proportional, and has coordinate column with ; since with and , monotonicity of squaring on the nonnegatives [L5] gives .
Steps 3.1, 3.2 and 4.1 verify the strict, equality and strict reverse-triangle instances of (a), (b) and (c) respectively, all under the future timelike hypotheses confirmed in step 2.1; the equality case occurs exactly at the positive proportional pair of (b), in agreement with [L3] and [L4].
Depends on
The reversed Cauchy-Schwarz inequality for future timelike vectors
The reversed triangle inequality and convexity of the future timelike cone
Inertial frames and inertial charts of the affine Minkowski model
Timelike, null, spacelike and causal vectors of a Lorentz vector space
The timelike set has exactly two convex components, described in orthonormal coordinates
Lorentz forms of inertia (3,1,0) on a 4-dimensional real vector space
Square roots exist: a unique with ; the positives are
Squaring is monotone on the nonnegatives
Ordered field
Dependency tree · 2 levels
Sources
- B. Crowell, Special Relativity, revision 2020-12-10 (author-published undergraduate textbook): section 1.5 'Triangle and Cauchy-Schwarz inequalities' pp. 36-37; signature (+---) converted to (-+++) and c = 1 formulas converted to x^0 = c t
- S. M. Carroll, Lecture Notes on General Relativity, arXiv:gr-qc/9712019v1 (1997), Chapter 3 pp. 68-73 (timelike geodesics maximize proper time; the twin remark)
- H. S. Reall, Mathematical Tripos Part III General Relativity (Cambridge, October 12, 2022), section 2.3 'Curves of extremal proper time' pp. 28-30 (Minkowski example: straight lines are extremal and maximize); Internet Archive copy of the original https://www.damtp.cam.ac.uk/user/hsr1000/part3_gr_lectures.pdf