Curvature and the Einstein field equation · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

How matter and geometry shape each other

Science · Astronomy & Astrophysics · ages 23-24
Name ______________________   Date ____________
  1. In Gμν=(8πG/c⁴)Tμν, what do the indexed tensors describe?

    • Curvature and stress-energy
    • Coordinate names and a choice of coordinate origin
    • Two independent lists of coordinate labels
  2. Which tensor records local curvature measured through infinitesimal parallel-transport loops?

    • The list of coordinate labels alone
    • The vector's coordinate components alone
    • The Riemann tensor
  3. If one vector returns unchanged around one small loop, every local curvature component must be zero.

    Circle one:   True   False

  4. For a nearly static weak field and slow matter, which equation does the Einstein field equation recover?

    • An equation making all gravitational potentials zero
    • An equation removing all dependence on mass density
    • Newton's equation ∇²Φ=4πGρ
  5. A vector returns rotated after parallel transport around a small contractible loop in a smooth region. What does this establish?

    • The entire region must have zero curvature
    • Curvature affects transport around that loop
    • Changing the vector by hand measures the same thing
  6. In the displayed convention Gμν=κTμν, what coupling κ is fixed by matching Newtonian gravity?

    • 8πG/c⁴
    • 8πG/c²
    • 8πc⁴/G
  7. With zero cosmological constant, a vacuum region has Rμν=0. Must its full Riemann tensor also vanish?

    • Yes; every contraction determines every component
    • Yes; vacuum removes all possible tidal effects
    • No; tidal curvature can remain
  8. A student gives Tμν everywhere and claims this alone selects one spacetime metric. What information can still be needed?

    • Only a different name for each coordinate
    • Initial or boundary data
    • Only a different symbol for Newton's constant
LightMySky · lightmysky.comW1-mt_1CxE6kRDt_-s1

Answer key

For grown-ups. Fold this page away before handing over the rest.

How matter and geometry shape each other W1-mt_1CxE6kRDt_-s1

  1. Curvature and stress-energy · Gμν is the Einstein curvature tensor; Tμν is the stress-energy tensor.
  2. The Riemann tensor · The Riemann tensor describes the leading transport mismatch for chosen vectors and loop areas.
  3. False · A single vector and loop sample only part of the curvature information.
  4. Newton's equation ∇²Φ=4πGρ · Under the stated limit, the relativistic equation reduces to the Poisson equation for Newtonian potential.
  5. Curvature affects transport around that loop · A genuine transport mismatch reveals curvature encountered by the loop.
  6. 8πG/c⁴ · The Newtonian match gives κ=8πG/c⁴, where G is Newton's constant.
  7. No; tidal curvature can remain · Vanishing Ricci curvature does not require vanishing full Riemann curvature.
  8. Initial or boundary data · The source tensor constrains the metric but does not supply all solution data.
Worksheet · LightMySky