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Wave particle duality

“Indivisible waves” of Strassler

In this blog post https://profmattstrassler.com/articles-and-posts/particle-physics-basics/the-astonishing-standard-model/why-the-weak-nuclear-force-is-short-range/ Matt Strassler talks about a concept he calls “indivisible waves”: “Don’t ask me how indivisible waves can exist; I don’t know. Experiments teach us that they do. But no one can easily visualize how and why this happens.” Is this concept of “indivisible waves” an accepted concept in physics or is it a concept invented by Strassler? Explain.

The concept of “indivisible waves” described by Matt Strassler in his blog is not a standard term in physics but rather a metaphorical way to convey a counterintuitive aspect of quantum field theory. It reflects a real, experimentally verified phenomenon but uses accessible language to explain it.

In the context of particle physics, the “indivisible waves” Strassler refers to are quantum fields that underlie fundamental particles. These fields exhibit quantized excitations, meaning that interactions occur in discrete packets of energy, corresponding to particles like photons, electrons, or W and Z bosons. This quantization ensures that these waves cannot be arbitrarily divided; the smallest “piece” of a wave is an entire quantum, or particle.

Why is this description useful?

Strassler’s term “indivisible waves” captures the idea that quantum fields behave differently from classical waves:

Classical waves (e.g., sound or water waves) can be divided into smaller parts, with their energy spread continuously across space.
Quantum waves, however, are inherently discrete in their interactions, as the energy is tied to the creation or annihilation of whole particles.

Is this a new concept?

No, it is not a new concept. The quantization of waves and fields is a cornerstone of quantum mechanics and quantum field theory, formalized in the early 20th century. However, Strassler’s term “indivisible waves” seems to be his unique phrasing to make these ideas more intuitive for a lay audience. Physicists usually use more formal language, such as “quantized excitations of a field” or “wave-particle duality.”

Summary

While “indivisible waves” is not standard terminology, the underlying idea is firmly rooted in established physics. Strassler’s phrasing aims to demystify the highly abstract concept of quantum field behavior for non-specialists.

Field, wave and particle

The words “field”, “wave” and “particle” have different meanings and properties in classical mechanics and in Quantum Mechanics. Can you explain how these words vary in meanings in these two realms?

The terms “field,” “wave,” and “particle” have distinct meanings and roles in classical mechanics and quantum mechanics due to the fundamental differences between these realms of physics. Here’s an overview of how these concepts differ:

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1. Field

In Classical Mechanics:

A field is a continuous, spatially distributed quantity that can be defined at every point in space and time.
Examples include:
- The gravitational field, representing the force experienced by a mass at a point in space.
- The electric and magnetic fields, which describe forces on charges and moving charges.
Fields are deterministic, and their behavior is governed by classical equations such as Maxwell’s equations for electromagnetism or Newton’s law of gravitation.

In Quantum Mechanics:

A field can refer to a quantum field in the context of Quantum Field Theory (QFT).
Quantum fields are operators that create and annihilate particles and describe how particles interact. For example:
- The electromagnetic field is quantized, leading to the concept of photons (quanta of the electromagnetic field).
Fields are inherently probabilistic, and their behavior is governed by quantum principles, such as superposition and uncertainty.

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2. Wave

In Classical Mechanics:

A wave is a disturbance or oscillation that travels through a medium (e.g., sound waves in air, water waves) or in a field (e.g., light as an electromagnetic wave).
Waves are described by classical wave equations and exhibit properties like interference, diffraction, and refraction.
They are continuous and deterministic.

In Quantum Mechanics:

The term wave relates to the wavefunction, which is a mathematical function representing the probability amplitude of a particle’s position and momentum.
Waves in quantum mechanics describe the probabilistic nature of particles, encapsulated by the Schrödinger equation.
Unlike classical waves, the wavefunction is not directly observable but provides the probabilities for measurable outcomes.
Quantum particles exhibit wave-particle duality, where they can behave as both waves and particles depending on the context (e.g., the double-slit experiment).

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3. Particle

In Classical Mechanics:

A particle is a localized object with mass and defined properties like position, velocity, and momentum.
Particles are treated as discrete entities, following deterministic laws such as Newton’s laws of motion.

In Quantum Mechanics:

A particle is described by its quantum state, which includes its wavefunction.
Particles are not point-like in the classical sense; they are better understood as excitations of quantum fields.
Properties like position and momentum are probabilistic and subject to the Heisenberg Uncertainty Principle.
For example, an electron is not simply a small, solid object but has a probability cloud (wavefunction) describing where it is likely to be found.

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Key Differences:

Concept	Classical Mechanics	Quantum Mechanics
Field	Continuous, deterministic	Quantized, probabilistic, operator-based
Wave	Oscillation in space or medium	Probability amplitude (wavefunction)
Particle	Localized, discrete, deterministic	Probabilistic, wave-particle duality

In summary, the transition from classical to quantum mechanics redefines these concepts, introducing probabilistic and quantized behavior that fundamentally differs from the deterministic nature of classical physics.