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Equation 1 · Part 12 · The Resonance That Selected Carbon, and the Universes That Couldn't

subscript

⟨σv⟩3α  ∝  ΓαΓ Γrad  exp⁡ ⁣(−ERkBT)\langle \sigma v \rangle_{3\alpha} \;\propto\; \frac{\Gamma_\alpha}{\Gamma}\,\Gamma_{\mathrm{rad}}\; \exp\!\left(-\frac{E_R}{k_{B}T}\right)
subscript

What this part means

The lower label selects a particular version, component, or indexed member of the quantity. For example, x₀ and xₜ can be values at different positions.

Its job in the formula

A subscript distinguishes a version, component, step, or member of a quantity. It does not automatically mean multiplication.

The passage around this formula

The underlying reaction-rate dependence that ties the Hoyle-state’s radiative width directly to the resonance’s position above threshold is the same relation used throughout the modern literature on this reaction, of the schematic resonant form ⟨σv⟩3α  ∝  ΓαΓ Γrad  exp⁡ ⁣(−ERkBT)\langle \sigma v \rangle_{3\alpha} \;\propto\; \frac{\Gamma_\alpha}{\Gamma}\,\Gamma_{\mathrm{rad}}\; \exp\!\left(-\frac{E_R}{k_{B}T}\right). where Γα\Gamma_\alpha and Γrad\Gamma_{\mathrm{rad}} are the alpha-decay and radiative partial widths, Γ\Gamma their sum, and ERE_R the resonance energy above the reacting threshold [ 5 ] . The exponential term is why a shift in the resonance’s position has outsized leverage on the reaction rate, and why the disputed radiative-width measurements of the previous section and the sensitivity calculations here are, in the end, two views of the…

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Learn the underlying idea

A subscript is a label attached below a symbol. It often selects a time step, component, category, or member of a sequence.

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Sources cited in the surrounding passage

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