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.

Type to find tags:
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Path integral formulation (Due to Feynman) is a major formulation of Quantum Mechanics along with Matrix mechanics (Due to Heisenberg and Pauli), Wave Mechanics (Due to Schrodinger), and Variational M…
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the quantum field theory believed to describe the strong nuclear force.
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The special-relativistic relation connecting energy with (rest) mass, $ E^2 - (m c^2)^2= (pc)^2 $. May be used to provide accounting constraints in energy and momentum, both conserved in total, even …
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Use as a synonym to the representation-theory tag
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The force on a body resulting from it's motion through a fluid (gas or liquid). This force is directly opposed to the direction of travel.
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A tag for questions about rotational motion, including angular velocity and angular acceleration.
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To be used for questions on geometry closely pertaining to physics. Includes differential geometry and euclidean geometry.
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a layer of gases that surround it, permitting life and protecting life by absorbing ultraviolet solar radiation, warming the surface by retaining the heat and mitigating the temp…
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Polarization characterizes the oscillations in time the electromagnetic field is doing in the plane perpendicular to the propagation direction of a wave
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the practice of separating a signal by frequency (or sometimes energy or momentum) and analyzing the resulting spectrum.
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Matter not observed directly but inferred to exist based upon its gravitational effects
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just because your question involves math! If your question is on simplification of a mathematical expression, please ask it at math.stackexchange.com The mathematics tag covers non…
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The subfield of optics in which light propagation is approximated in terms of rays. It mainly includes reflection and refraction on surfaces.
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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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any of several principles that find the physical trajectory of a system by minimizing or maximizing some value computed over the proposed path (for instance geometric optics can be reproduced by insis…
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The time rate of change of energy
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particles with an intrinsic angular momentum (i.e. spin) equal to a "half integer" number of fundamental units: $\frac{(2n+1)}{2} \hbar$ for integer $n$. Fermions are required to be in a …
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an almost perfectly symmetric yellow dwarf star [spectral class G2V] which is at the center of our Solar System.
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questions concerning measurements, experiments, and activities that demonstrate physics and are safe to do at home, require at most one tool or ingredient not readily available, and can be interpreted…
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The near-vacuum extending between the planets and stars, containing small amounts of gas and dust. Also called outer space to refer to the physical universe beyond the Earth's atmosphere.
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The use of methods from the physical sciences to aid in the study of biological systems. Note that biophysics questions are only allowed if they are mainly about physics.
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A subset of [tag:fluid-dynamics] concerning primarily forces such as lift and drag generated on bodies as they move through gasses or as gasses move through the body (typically air).
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defined as the bending or flaring of light around the corners of an obstacle or aperture into the region of geometrical shadow of the obstacle. This flaring is consistent with the sprea…
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A research field within general optical physics concerned with light and its material interaction: where light is modelled by full quantum mechanical description.
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Analogous to matter, but with charge of the particles opposite to their ordinary matter counterparts.
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for dimensions of a manifold, typically the space-time. DO NOT USE THIS TAG for dimension of a physical quantity.
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astronomical bodies that are (usually) mainly composed of Hydrogen, Helium, and Lithium. They are massive enough that their gravity compresses the matter to the point where nuclear fusion oc…
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The Sun plus the collection of bodies in orbit around the Sun such as planets, dwarf planets, moons, asteroids, comets, etc.
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the magnitude of velocity.
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energy transferred from one system to another by thermal interaction. In contrast to work, heat is always accompanied by a transfer of entropy. Heat flow is characteristic of macroscopic objec…
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A vector space $\mathfrak{g}$ over some field $F$ and kitted with a bilinear, antisymmetric and Jacobi-identity-fulfilling product ("Lie Bracket" or "commutator"). In physics, most often arises as the…
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light, uncharged leptons. The neutrino tag should be applied to question relating to neutrino properties or interactions involving neutrinos.