Co-authored-by: blackboxprogramming <118287761+blackboxprogramming@users.noreply.github.com>
4.4 KiB
Notebook Page 1 — Transcription
Source:
→ halting problem.pdf, page 1 of 24.
Transcribed by Alexa Louise Amundson.
1. Computer Science & Logic: The Halting Problem
Complex & Imaginary Numbers
(a + ib)(a − ib) = a² − ibib
Imaginary: (y + x)² y
Real: (y + x)²
Euler's formula expansion:
e^(ix) = 1 + ix − x²/2 − i(x³)/6 + x⁴/24 − ...
Paradoxes & Abstraction
- Golden Braid — a reference to levels of abstraction and paradoxes.
- "This sentence is false" → refers to its own truth value.
- Cantor diagonalization → linked to the Halting problem.
The Halting Problem
A thought experiment for a hypothetical program h that predicts whether another program will loop forever or halt.
Program 1 → [h]: Input I into program h.
h answers: will this problem halt, or will it not?
Examples:
x = 4
while x > 3: x += 1 → LOOPS FOREVER
x = 4
while x < 1000: x += 1 → Halts.
The Paradox (h+):
- Take the source code (e.g.,
11001011) and use that code as both the program and the input. - Feed
xas data into itself:x = h+. - If
hhalts →h+begins an infinite loop. - If
hloops →h+halts.
"Does it loop or halt? It's a paradox! But h does not exist!"
2. Number Theory: The Möbius Function
Definitions & Rules
The Möbius function μ(n) is a multiplicative number-theoretic function.
For any positive integer n, define μ(n) as the sum of the primitive n-th roots of unity.
Factorization rules:
μ(n) = 0 if n has one or more repeated prime factors
μ(n) = 1 if n = 1
μ(n) = (−1)^k if n is a product of k distinct primes
μ(n) ≠ 0 indicates that n is square-free.
First few values:
1, −1, −1, 0, −1, 1, −1, 0, 0, 1, −1, 0, ...
Formulas & Series
Mertens Function (summatory function of Möbius):
M(x) = Σ_{n ≤ x} μ(n)
Dirichlet Series (multiplicative inverse of the Riemann zeta function):
Σ_{n=1}^{∞} μ(n)/n^s = 1/ζ(s) ; Re(s) > 1
Lambert Series:
Σ_{n=1}^{∞} (μ(n) x^n) / (1 − x^n) = x ; |x| < 1
Kronecker Delta Relation:
Σ_{d|n} μ(d) = δ_{n,1}
Infinite Sums:
Σ_{n=1}^{∞} μ(n)/n = 0
Σ_{n=1}^{∞} (μ(n) ln n)/n = −1
Σ_{n=1}^{∞} μ(n)/n² = 6/π² = 1/ζ(2)
Historical note: Gauss considered the Möbius function over 30 years before Möbius, proving that for a prime number p, the sum of its primitive roots is congruent to μ(p − 1) (mod p).
3. Probability & Math: Gaussian Functions & Fourier Transforms
Gaussian Basics
Used to represent the probability density function of a normally distributed random variable.
- Expected value: μ = b
- Variance: σ² = c²
Standard form:
f(x) = (1 / (σ √(2π))) · e^(−(1/2)((x−μ)/σ)²)
Arbitrary constants form (a = peak height, b = center, c = width):
f(x) = a · e^(−(x−b)² / 2c²)
Fourier Transform Proofs
Transform of a Gaussian:
F{ a · e^(−bx²) } = (a / √(2b)) · e^(−ω² / 4b)
The integration proof uses substitution t = x + iω/2b, showing that the Fourier transform of a Gaussian is also a Gaussian.
Derivative Properties:
Time domain: F{ f′(x) } = iω · F(ω)
Frequency domain: F{ x f(x) } = i · d/dω F(ω)
4. Physics: Quantum Mechanics & Energy
Schrödinger Equation & Operators
Time-dependent equation:
iℏ (∂/∂t) Ψ = HΨ
Where:
i= √(−1)ℏ= Planck's constant (reduced)Ψ= quantum wave functionH= Hamiltonian operator
Harmonic Oscillator:
Classical energy: (1/2)mv² + (1/2)kx² = E
Momentum operator: p → (ℏ/i)(∂/∂x)
Quantum Hamiltonian: H → (−ℏ²/2m)(∂²/∂x²) + (1/2)kx²
Eigenvalue equation: HΨ = EΨ
Uncertainty & Photons
Heisenberg Uncertainty Principle:
Δp · Δx ≥ h / 4π (= ℏ/2, where ℏ = h/2π)
Energy of a photon:
E = hν = hc/λ
Photoelectric effect:
(1/2) m v_max² = eV₀ = hf − φ
Fundamental Constants & Bohr Model
r = (n² h² ε₀) / (π m e²) ∝ h²
v = e² / (2 ε₀ n h) ∝ 1/n
Fine-Structure Constant (α):
α = (1 / 4πε₀) · (e² / ℏc) ≈ 1/137
Speed of light: c = 3 × 10⁸ m/s
Elementary charge: e = 1.602 × 10⁻¹⁹ C