A tag is a keyword or label that categorizes your question with other, similar questions. Using the right tags makes it easier for others to find and answer your question.

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the quantum field theory believed to describe the electromagnetic interaction (and with some extension the weak nuclear force).
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Applies also to pre-Hilbert spaces, rigged Hilbert spaces, and spaces with negative norm or zero-norm states.
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A postulated symmetry between bosonic and fermionic fields in quantum field theories and string theories.
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A model of the basic particles and forces featuring six quarks, three charged leptons, three massless neutral leptons and four fundamental force carrying bosons. The twelve fermions are arranged into …
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A measure of the rate at which electric charge is transported (especially through a circuit), it has units of charge/time.
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used to describe any system with a "linear" restoring force that tends to return the system to a equilibrium state. There is both a classical harmonic oscillator and …
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A fundamental property of matter which causes it to experience electromagnetic forces.
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Any of the various explanations of gravity as a quantum theory, including string theory and loop quantum gravity.
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a formalism in Classical Mechanics. Besides Lagrangian Mechanics, it is an effective way of reformulating classical mechanics in a simple way. Very useful in Quantum Mecha…
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an ensemble of techniques which serves to treat the infinities which appear in quantum field theory or statistical mechanics.
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The time rate of change of the position of an object
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Scalar and vector potentials in electromagnetism. The scalar potential is potential energy per unit charge. For potential energy, use the potential-energy tag.
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Geometric object with magnitude (length) and direction.
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physics taught and learned. Teaching strategies, class examples and demonstrations; learning resources, career advice, etc. For explicit problems, use the 'homework' tag instead.
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a cosmological phenomenon wherein the proper distance between two spatial points for a given inertial reference frame increases from one moment of time to another. That is, space it…
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The study of how the properties of matter arise from its structure at all scales and of how processing can be used to modify those properties (often in pursuit of a specific application).
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a process in which energetic particles or energetic waves travel through a medium or space. The particles or waves radiate (i.e., travel outward in all directions) from a source.
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The product of the force on an object and the displacement the object undergoes along the direction of the force.
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a branch of abstract algebra. A group is a set of objects, together with a binary operation, that satisfies four axioms. The set must be closed under the operation and contain an ident…
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The union of special (SR) and general (GR) relativity. Use this tag if both SR and GR apply.
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a general term for several physical processes in which radiation of some sort changes direction due to an interaction with a particle. Scattering can be classified by the type of radiati…
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Interaction between two or more bodies that results in physical contact and an exchange of momentum between the bodies involved.
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the mechanism by which quantum correlations between two sub-systems survive even after being physically separated from an interaction region. The correlations could in principl…
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to electrical resistance. DO NOT USE THIS TAG for non-electrical resistance.
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for questions seeking a single specific paper or a short, non-open-ended list of references, like "What paper first discovered X?", "Where can I find the original derivation of X?", or "W…
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According to the current cosmological theories, it's the model that explains the early life of the universe, starting from a rapid expansion of hot and dense matter.
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the planet on which we live, the 3rd planet from the Sun. Questions using this tag should be about Earth the planet and not Earth-like planets nor earth, as in dirt or soil.
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the branch of solid state physics that focuses on specific properties of semiconductors. It studies dynamics of different perturbations (mainly electrons and holes) in the sem…
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for Heisenberg quantum mechanical uncertainty principle.
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the energy of a body or a system due to the position of the body or the arrangement of the particles of the system.
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Light Amplification by Stimulated Emission of Radiation. A means of creating coherent light by either driving an atomic or molecular transition in an optical cavity or firing a beam of electrons throu…
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The variables used in general relativity to describe the shape of spacetime. If your question is about metric units, use the tag "units", and/or "si-units" if it is about the SI system specifically.
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The result of sampling the property of a system
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