| name | dimensional_analysis |
| description | Use when checking dimensional consistency, estimating physical scales, or deriving functional forms via the Buckingham Pi theorem. |
Dimensional Analysis
Apply this skill when you need to verify that equations are dimensionally consistent, estimate the order of magnitude of a physical quantity, or derive the functional dependence of a quantity on relevant parameters without solving the full equations.
Goal
Use dimensional reasoning to constrain or derive physical relationships, check equation correctness, and estimate scales.
Scope
- SI and natural unit systems (h-bar = c = 1, Gaussian, Heaviside-Lorentz, lattice units, etc.)
- Buckingham Pi theorem for systematic reduction
- Order-of-magnitude estimation
Inputs
physical_quantities: The relevant dimensional quantities (masses, lengths, times, charges, etc.)
target_quantity: The quantity whose dimensions or functional form you want to determine
unit_system: The unit convention in use (SI, natural, CGS, lattice, etc.)
Outputs
dimensional_check: Whether each equation or expression is dimensionally consistent (pass/fail with explanation)
pi_groups: Dimensionless combinations identified via Buckingham Pi (if applicable)
estimated_scale: Order-of-magnitude estimate of the target quantity
Workflow
- List all independent dimensional quantities and their dimensions in the chosen unit system.
- Identify the independent base dimensions (e.g., M, L, T, Q).
- If checking an equation: verify that every term shares the same dimensions.
- If deriving a relation: apply the Buckingham Pi theorem.
- Count the number of quantities (n) and independent base dimensions (k).
- Form (n - k) independent dimensionless Pi groups.
- Express the target quantity as a function of dimensionless groups times a dimensional prefactor.
- If estimating a scale: substitute typical numerical values to obtain an order-of-magnitude result.
Quality Checks
- Every term in a valid equation must have identical dimensions.
- The number of independent Pi groups must equal n - k.
- Natural-unit expressions must be convertible back to SI with appropriate powers of h-bar and c.
Constraints
- Dimensional analysis determines functional form up to dimensionless numerical coefficients; do not claim exact prefactors unless derived from a full calculation.
- When using natural units, always state the conversion factors explicitly if the user needs SI results.
- Do not silently mix unit systems within the same expression.