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Chapter 2: Terminology, Symbols & Metrology Baseline


I. Scope & Dependency Anchors


II. Frequency, Spectral Density & Transform Conventions

  1. S20-1 (Angular vs. linear frequency)
    Use ω = 2π f. Do not mix ω/f in a single expression unless explicitly stated.
  2. S20-2 (Fourier dual)
    F(ω) = ∫ f(t) e^{-i ω t} dt; f(t) = (1/2π) ∫ F(ω) e^{i ω t} dω.
  3. S20-3 (PSD convention)
    Explicitly declare one-sided or two-sided:
    • Two-sided: S_{xx}(ω), unit unit(x)^2/Hz.
    • One-sided: S_{xx}^{(1)}(f), same unit per Hz, domain f ≥ 0.
  4. S20-4 (Cross-spectra & coherence)
    S_{xy}(ω) and coherence γ_{xy}^2(ω) = |S_{xy}(ω)|^2 / (S_{xx} S_{yy}). Default is two-sided unless declared.

III. Units, Dimensions & Uncertainty

  1. S20-5 (Unit system)
    SI throughout: K, J, W, m, s, Hz, rad, and engineering dBm. Phase-PSD in rad^2/Hz.
  2. S20-6 (Dimension checks)
    All expressions must pass check_dim; dataset tables must include unit columns. Typical verifications:
    • S_VV = 4 k_B T R ⇒ [V^2/Hz] = [J·K^-1][K][Ω].
    • φ_CP = (2π/λ)(ρ + c_ref b_t) ⇒ [rad].
    • f_D = - ( f_c / c_ref )( v_rel · n̂ ) ⇒ [Hz].
  3. S20-7 (Uncertainty & coverage)
    Standard u(x), combined u_c, expanded U = k · u_c (coverage factor k); covariance Σ, observation covariance Σ_y.

IV. Canonical Noise & Response Conventions

  1. S20-8 (Classical thermal noise)
    Johnson–Nyquist (classical limit) S_VV = 4 k_B T R.
  2. S20-9 (Quantum FDT)
    S_{xx}(ω) = 2 coth( (ħω)/(2 k_B T) ) · Im χ_{xx}(ω). Each use of χ(ω) must specify response variable, excitation, and units.
  3. S20-10 (Bath spectral density)
    If using a scaled family, default J(ω) = η ω (ω/ω_c)^{s-1} e^{-ω/ω_c}; record η, s, ω_c provenance in the dataset.
  4. S20-11 (Heat transport & non-Fourier)
    Diffusion: ∂_t T = α ∇^2 T; Cattaneo–Vernotte: τ_q ∂_t q + q = -κ ∇T, with [α]=m^2·s^-1, [κ]=W·m^-1·K^-1.
  5. S20-12 (Cross-disciplinary arrival-time fields)
    If the metrology chain reuses propagation/arrival time, the dataset must declare one convention:
    • T_arr = ( 1 / c_ref ) * ( ∫ n_eff d ell ), or
    • T_arr = ( ∫ ( n_eff / c_ref ) d ell ),
      and explicitly provide gamma(ell) and d ell.

V. Symbol Table (Incremental)

Symbol

Name

Definition/Use

SI/Eng Unit

Dim.

Notes

T

temperature

thermal state

K

Θ

β = 1/(k_B T)

inverse temperature

statistical weight

K⁻¹

Θ^-1

κ

thermal conductivity

heat transport

W·m⁻¹·K⁻¹

M L T^-3 Θ^-1

α

thermal diffusivity

macro heat transport

m²·s⁻¹

L^2 T^-1

R_K

Kapitza resistance

interface resistance

K·m²·W⁻¹

Θ L^2 M^-1 T^3

S_{xx}(ω)

auto PSD

two-sided PSD

unit(x)^2/Hz

one-sided S_{xx}^{(1)}(f)

S_{xy}(ω)

cross PSD

correlation

unit(x)·unit(y)/Hz

J(ω)

bath spectral density

system–bath coupling

model-dependent

needs η, s, ω_c

χ(ω)

response function

FDT link

system-dependent

units must be stated

ω_c

cutoff frequency

spectral shape

rad·s⁻¹

T^-1

η, s

spectral-shape params

amplitude/index

T_1, T_2, Γ_1, Γ_φ

relaxation/coherence

decoherence figures

s / s⁻¹

T / T^-1

n̄(ω,T)

Bose occupation

1/(e^{ħω/k_B T}-1)

l_mfp

mean free path

mesoscopic transport

m

L

q

heat flux density

energy transport

W·m⁻²

M T^-3

c_ref

reference propagation speed

cross-volume const.

m·s⁻¹

L T^-1

light speed

c_med

medium speed

optional

m·s⁻¹

L T^-1

acoustic/special media


VI. Data Contract (Required/Recommended Fields)

unit_system: "SI"

spectral_conventions:

fourier: {forward: "∫ f(t) e^{-iωt} dt", inverse: "(1/2π) ∫ F(ω) e^{iωt} dω"}

psd: {type: "one-sided|two-sided", freq: "ω|f"}

noise_models:

classical: "S_VV = 4 k_B T R"

quantum_fdt: "S_xx(ω) = 2 coth(ħω/2k_B T) · Im χ_xx(ω)"

bath_spectrum:

model: "ohmic|sub|super|custom"

params: {eta: "<…>", s: "<…>", omega_c: "<rad/s>"}

heat_transport:

model: "Fourier|Cattaneo|BTE"

params: {kappa: "<W/m/K>", alpha: "<m^2/s>", R_K: "<K m^2/W>"}

arrival_time: # if propagation chain is reused, mandatory

convention: "pulled_const|integrand"

delta_form: "c_ref^-1 * ∫ n_eff dℓ" # or "∫ (n_eff/c_ref) dℓ"

gamma: "piecewise: free|fixture|substrate|device|environment"

d_ell: "m"

uncertainty:

coverage_k: 2.0

Σ: "<block-diagonal or sparse>"

references: ["Heat.Decoherence v1.0:S20-*","Core.Metrology v1.0:Ch.1–3,5"]


VII. Quality Gates (This Chapter)


VIII. Cross-Volume References & Anchors (This Chapter)


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Copyright: Unless otherwise noted, the copyright of “Energy Filament Theory” (text, charts, illustrations, symbols, and formulas) belongs to the author “Guanglin Tu”.
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Suggested attribution: Author: “Guanglin Tu”; Work: “Energy Filament Theory”; Source: energyfilament.org; License: CC BY 4.0.

First published: 2025-11-11|Current version:v5.1
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