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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a type of boundary such that any information past this boundary is inaccessible to the observer it is defined for. Common examples are the Schwarzschild radius of a black hole (whi…
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Theory, experiments and calculations related the physics of plasmas, i.e., matter constituted by ionized atoms.
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for topological field theory (Tft) and topological string theory (tst) questions.
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Could refer to (1) A hydrogen molecule; two hydrogen atoms bonded together or (2) A hydrogen atom; One electron electromagnetically interacting with a nucleus made of a single proton. Hydrogen atoms a…
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for questions about singularities in physical quantities. Use the tag "singularity" for general relativistic singularities such as those inside black holes and at the Big Bang.
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the electromagnetic radiation in the microwave band which can be observed throughout the whole universe, not connected to any astronomical object. Its spectrum…
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The motion of fluids (gases, liquids and granular material).
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The quark model postulates that the hadrons such as protons and neutrons have an inner structure; quarks.
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for questions on information theory applied to physics, especially in the fields of statistical mechanics and thermodynamics, the black hole information paradox, complexity of dynamical a…
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the study of electric circuits and electrical components, and the design of useful devices. Some questions in this tag may be more appropriate for the [Electrical Engineering(http://ele…
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A pictorial device which analyzes forces present on any body with the use of vectors. Allows easier grasping of problems involving either objects at equilibrium or in motion. Can be used to predict pr…
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A specific reference frame that describes its coordinates in a manner that does not depend on time and is isotropic.
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World's largest particle accelerator built by the CERN (European Organization for Nuclear Research) near the Franco-Swiss frontier near Geneva, Switzerland. It is designed to collide beams of protons…
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Techniques and methods for computing, estimating, or placing bounds on the errors of expressions (formulas) based on knowledge of error distributions, error intervals or bounds of variables and parame…
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a branch of mechanics that deals with the analysis of the kinematics and the mechanical behavior of materials modeled as a continuous mass rather than as discrete particles.
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Use "buoyancy" for any question where an object is suspended or submerged in a fluid. Buoyant force is the force that acts upward on a partially or completely submerged object.
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A smaller body orbiting a larger, primary body, where the primary body is not a star.
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a new kind of order in quantum matter, which corresponds to pattern of long-range quantum entanglement. See http://en.wikipedia.org/wiki/Topological_order
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A particle that emerges from the theoretical mechanism that is thought to give other particles mass.
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For questions involving consideration of the shortest (or longest) path between two points in a curved space (e.g. a straight line between two points on the surface of a sphere such as the earth).