# Tags

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.

Use this for questions pertaining to curvature of manifolds. Does not need to be specific to general relativity, but also for curvature of e.g. a Calabi-Yau manifold.
1332 questions
Fluid statics or hydrostatics is the branch of fluid mechanics which deals with the study of fluids at rest and the pressure exerted by it on an immersed object. If your question is about the study of…
1312 questions
The central term in the hamiltonian formalism. Can be interpreted as an energy input, or "true" energy.
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Questions that ask about some aspect of physics research or study which doesn't involve the actual physics. In general, soft questions can be answered without using physical reasoning.
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Change in the direction of propagation of a wave when its transmitting medium changes. The tag does also apply to index of refraction.
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The temperature-dependent emission of electromagnetic waves. Combine this tag with the [thermodynamics] tag for a macroscopic view or the [quantum-mechanics] tag for a microscopic explanation.
1271 questions
for questions on the meaning, history, and usage of various symbols and notation that are used to denote different quantities in physics. Don't forget to mention the reference, where you …
1270 questions
A law in classical electromagnetism and Newtonian gravity which relates (charge) density to the divergence of a field, or alternatively the charge in a volume to the flux through the bounding surface.
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for Heisenberg's quantum mechanical uncertainty principle. DO NOT USE THIS TAG for uncertainty in a non-quantum measurement.
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A conformal field theory (CFT) is a quantum field theory that is invariant under conformal transformations. In 2D, the infinite-dimensional algebra of local conformal transformations normally permits …
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A set of four equations that define electrodynamics. They comprise the Gauss laws for the electric and magnetic fields, the Faraday law, and the Ampère law. Together, these equations uniquely determin…
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A diagrammatic technique introduced by Richard Feynman to describe the quantum behaviour of subatomic particles and their interactions. Do not use for general questions on diagrams that are not of the…
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Frequency is the rate of repetitive aspect in the amplitude over a given dimension.
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The systematic study of group representations, which describe abstract groups in terms of linear transformations of vector spaces, such that group elements or their generators are represented as matri…
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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…
1181 questions
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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Interference describes different waves superposing to form a resultant wave of greater, lower, or the same amplitude. Normally, it involves interaction of waves that are correlated (coherent) with eac…
1138 questions
For questions about probability, probability theory, probability distributions, expected values and related matters. Purely mathematical questions should be asked on Math.SE.
1132 questions
A tag for questions about rotational motion, including angular velocity and angular acceleration.
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for questions relating to projectile, object moving through space due to the exertion of a force. The path of a projectile is called its trajectory.
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The double slit experiment involves passing light through two parallel slits to demonstrate that the light from one slit interferes with that from the other.
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An object such as a metal coil or air-filled tube which provides a force opposing the direction of deformation.
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A region of space devoid of any fluid molecules resulting in a zero pressure in ideal cases. In practice, even space has a small but finite number of molecules. In QFT, it signifies the ground state d…
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A phase transition is a change in the nature of a phase or in the number of phases of a system as a result of a change in the external conditions. Examples: melting/freezing, vaporization/condensation…
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A postulated symmetry between bosonic and fermionic fields in quantum field theories and string theories.
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Fermions are 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 …
1086 questions
The union of special (SR) and general (GR) relativity. Use this tag if both SR and GR apply.
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For questions about problems related to physics that involve evaluating integrals. Purely mathematical questions should be asked at math.SE.
1083 questions
Superconductivity is the transmission of current with no resistive losses, and is one of the most active areas of condensed matter physics research.
1076 questions
The special-relativistic relation connecting energy with 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 in reac…
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Dimensional analysis means to obtain results by analyzing the units in question, etc. DO NOT USE THIS TAG if your question is about degrees of freedom or spatial dimensions.
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for questions regarding to electromagnetic induction, a process in which a conductor is put in a particular position and magnetic field keeps varying or magnetic field is stationary and a …
1057 questions
for questions regarding the 'time dilation' which is the lengthening of the time interval between two events for an observer in an inertial frame that is moving with respect to the rest fr…
1040 questions
How is physics taught and learned. Teaching strategies, class examples and demonstrations; learning resources, career advice, etc. For explicit problems, use the 'homework' tag instead.
1039 questions
Study of macroscopic and microscopic phenomena in chemical systems in terms of physical laws and concepts [thermodynamics, statistical mechanics, kinetic theory, quantum mechanics...].
1031 questions