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particle-physics photons

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lagrangian-formalism variational-principle action

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What is spontaneous symmetry breaking in quantum systems?

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0range

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What exactly is a photon?

Why does space expansion not expand matter?

Why are there only derivatives to the first order in the Lagrangian?

What is time, does it flow, and if so what defines its direction?

What is spontaneous symmetry breaking in quantum systems?

Why isn't the Euler-Lagrange equation trivial?

Noether charge of local symmetries

Do virtual particles actually physically exist?

Why is there this relationship between quaternions and Pauli matrices?

If string theory is inconsistent with observations, why hasn't it been rejected yet?

Deterministic quantum mechanics

Intuitive understanding of the elements in the stress-energy tensor

How do we know that entanglement allows measurement to instantly change the other particle's state? [duplicate]

Why was quantum mechanics regarded as a non-deterministic theory?

Quivers in String Theory

What does a non-perturbative theory mean?

How is a Hamiltonian constructed from a Lagrangian with a Legendre transform

Is my interpretation of a quantum field correct?

Why do eigenvalues correspond to observable quantities?

Counting degrees of freedom of gauge bosons

Correspondence between wave function and state vector

What is the exact meaning of Lorentz invariance for a quantum scalar field?

What developments have been made in this unsolved problem? [duplicate]

Complex Lie algebra vs Real Lie algebra in Physics

Generalising a Dirac Delta function formula in General Relativity

Forces acting on rope [duplicate]

How exactly does an electron falling back to its original state from an excited state produce electromagnetic waves?

Do Dirac field states belong to a Hilbert space with spinor coefficients?

Is there a mathematical model of the process of "getting entangled with"?

Why does the spectrum of Sun follow a black-body distribution curve?