Quantum mechanics

• Can Planck’s Constant Be Derived From Maxwell’s Equations?
  Maxwell’s equations predict classical electromagnetic waves, not Planck’s constant; quantum theory supplies the action scale needed to describe photon energies.
• Can a Digital Computer Simulate Quantum Entanglement to Any Precision?
  A classical digital computer can approximate entangled quantum systems to arbitrary precision in principle, but general simulations can require exponential resources.
• What Is Planck’s Constant, Simply Explained?
  Planck’s constant sets the scale of quantum effects and relates a photon’s energy to its frequency through the equation E = hf.
• Are Coherent States of Light Classical or Quantum?
  Coherent states are quantum states with classical-like field behavior, Poisson photon statistics, and unavoidable quantum fluctuations in measurements.
• What Are the Arguments For and Against Many-Worlds?
  Many-worlds keeps the quantum state evolving without collapse, but its costs include explaining probability, branching, and its vast ontology.
• Tensor Product vs. Cartesian Product in Quantum Systems
  For two quantum subsystems, the joint Hilbert space is a tensor product, not a Cartesian product of state vectors; see dimensions, product states, and entanglement.
• Tensor Product vs. Direct Product for Three Spin-1/2 Particles
  For three spin-1/2 particles, the composite Hilbert space is an eight-dimensional tensor product; total-spin sectors give a direct-sum decomposition.