Stack Exchange Network

Stack Exchange network consists of 175 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange


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.

× 1965
Applies also to pre-Hilbert spaces, rigged Hilbert spaces, and spaces with negative norm or zero-norm states.
× 1958
Force per unit area.
× 1935
A tag for questions about the mechanical interactions of rotating objects, including torque and angular momentum.
× 1914
Negatively charged particle with spin 1/2. A component of mundane terrestrial matter, and part of all neutral atoms and molecules. It has a mass about 1/1800 that of a proton. Its antiparticle is the…
× 1902
a particular coordinate system chosen to represent physical entities. The notion is most often used in special and general relativity to denote particular coordinates chosen on th…
× 1868
In introductory mechanics, the momentum of a particle is its mass times its velocity. In electrodynamics, the momentum of a field is proportional to the cross-product of the electric field with the ma…
× 1850
the study of the informational content of quantum states. The most common object of study is the "qubit", the information in a two-state quantum system such as spin-1/2 or photo…
× 1840
The law of conservation of energy, which states that the amount of energy in a system is constant. For questions about Earth's environment, see the climate-science tag instead.
× 1833
Solid-state physics studies how macroscopic properties of solids (mechanical, electrical, optical, etc.) result from their microscopic structure. It usually deals with the scale where quantum properti…
× 1820
For questions that utilize the concept of electric fields (commonly denoted by the letter E), or for questions whose answers likely involve electric fields. More specific than the [tag:electricity], a…
× 1791
A class of theories that attempt to explain all existing particles (including force carriers) as vibrational modes of extended objects, such as the 1-dimensional fundamental string. PLEASE DO NOT USE …
× 1790
A complex scalar field that describes a quantum mechanical system. The square of the modulus of the wave function gives the probability of the system to be found in a particular state. DO NOT USE THIS…
× 1765
the study of the composition, behavior and interaction of atomic nuclei and their constituent parts.
× 1761
It's the physical property that indicates the degree/intensity of heat present in a substance or an object. It can be expressed and measured according to various scales.
× 1737
a fundamental universal constant that marks the maximum speed at which energy and information can propagate. Its value is $299792458\frac{\mathrm{m}}{\mathrm{s}}$.
× 1696
The application of physical theory to celestial systems such as stars, planets, galaxies, supernovae, and black holes. Astrophysics proper is concerned with explaining phenomena more so than making ob…
× 1683
just because your question involves math! If your question is on simplification of a mathematical expression, please ask it at Mathematical physics is the m…
× 1670
The statement that a property of a system does not change if the system is isolated.
× 1653
the interdisciplinary science that deals with the study of all mechanical waves in gases, liquids, and solids including vibration, sound, ultrasound and infrasound. Applications of acoust…
× 1612
A measure of the rate at which electric charge is transported (especially through a circuit), it has units of charge/time.
× 1578
The rate of change of velocity of a body per unit of time.
× 1568
the field of physics that studies atoms as an isolated system of electrons and an atomic nucleus. It is primarily concerned with the arrangement of electrons around the nucleus and t…
× 1537
A fundamental property of matter which causes it to experience electromagnetic forces.
× 1526
The resistance a surface or object encounters when moving over another.
× 1515
symmetric if there is some transformation we can perform on that object that leaves some property unchanged. The set of symmetry transformations of an object form a group, and…
× 1485
The product of the force on an object and the displacement the object undergoes along the direction of the force.
× 1483
An important extensive property of all systems in thermodynamics, statistical mechanics, and information theory, quantifying their disorder (randomness), i.e., our lack of information about them. It …
× 1480
a good book about X?" or more generally, "What should I read to learn about X?", typically where there is not a single authoritative reference. Please READ THE GUIDANCE IN ME…
× 1478
The path a body takes while moving through space under the influence of the gravitational forces of other bodies
× 1468
Fundamental characteristic property of particles which together with orbital angular momentum acts as the generator of rotations and which doesn't have a classical equivalent but is sometimes compared…
× 1463
Scalar and vector potentials in electromagnetism. The scalar potential is potential energy per unit charge. For potential energy, use the potential-energy tag.
× 1447
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.
× 1441
to electrical resistance and resistors. DO NOT USE THIS TAG for non-electrical resistance.
× 1409
Partial differential equation which describes the time evolution of the wavefunction of a quantum system. It is one of the first and most fundamental equations of quantum mechanics.
× 1388
defined operationally to be that which is measured by clocks. The SI unit of time is the second, which is defined to be
× 1385
The science dealing with objects and phenomena located beyond Earth. In particular, this applies to observations and data. At its core, astronomy is the physically informed cataloging and classifying …