Schwinger's α/2π
Plate 055 Physics Poster
Plate 55 speaks for itself: “Small extra spin.”
The Physics
Dirac's theory gives the electron g = 2. Quantum electrodynamics adds a small correction; Schwinger's first-order term is α/2π.
a = (g − 2)/2 ≈ α/2π
- a: anomalous magnetic moment, dimensionless
- g: g-factor, dimensionless
- α: fine-structure constant ≈ 1/137.036, dimensionless
Dirac g = 2; measured: slightly more. Schwinger 1948: a = α/2π ≈ 0.0011614.
Honest caveat: α/2π is the leading term; the measured a_e = 0.00115965218… agrees once higher-order QED terms are included.
Sources
- J. Schwinger, Phys. Rev. 73, 416 (1948).
- X. Fan et al., Phys. Rev. Lett. 130, 071801 (2023).
On the poster
Plate 055, “Schwinger's α/2π”: the pixel-art plate with its slogan “Small extra spin.”, the key equation and the facts panel shown above. Pixelated Physics. Physics. Personified.
Shipping calculated at checkout by destinationMade to order, ships in 2–5 business days
Field notes
Wyświetl wszystkie-
Kármán Vortex Streets and Hydraulic Jumps: Why ...
Put a cylinder in a steady flow and it sheds a staggered trail of whirlpools called a Kármán vortex street. Let a fast, shallow stream slow down and it leaps...
Kármán Vortex Streets and Hydraulic Jumps: Why ...
Put a cylinder in a steady flow and it sheds a staggered trail of whirlpools called a Kármán vortex street. Let a fast, shallow stream slow down and it leaps...
-
What Are Lagrange Points, and Why Does JWST Sit...
Lagrange points are five spots where a small object can keep pace with two big ones, like a spacecraft riding along with the Sun and Earth. We work out where...
What Are Lagrange Points, and Why Does JWST Sit...
Lagrange points are five spots where a small object can keep pace with two big ones, like a spacecraft riding along with the Sun and Earth. We work out where...
-
Feynman Diagrams Explained: What the Little Squ...
A Feynman diagram is not a photo of particles bouncing around. Each little drawing stands for one term in a calculation of how likely a process is. Here is how...
Feynman Diagrams Explained: What the Little Squ...
A Feynman diagram is not a photo of particles bouncing around. Each little drawing stands for one term in a calculation of how likely a process is. Here is how...
