All articles starting with P

Particle

A particle, in modern physics, is a localized quantity of energy and momentum that behaves as a discrete object, and is also a wave in an underlying field.

Particle acceleration in magnetic reconnection

Particle acceleration in magnetic reconnection is the conversion of magnetic energy into nonthermal, power-law particle energies in plasmas, invoked to explain high-energy astrophysical flares and jets.

Particle accelerator

A particle accelerator, also called an atom smasher or nuclear accelerator, is a machine using electric fields to boost charged particles, probing matter and treating cancer.

Particle beam mass spectrometry

Particle beam mass spectrometry (PB-MS) is an LC-MS interface technique that removes solvent and delivers analyte to a standard electron ionization source, giving library-searchable spectra.

Particle board

Particle board, also called chipboard, is an engineered wood panel made from wood particles, such as sawdust and chips, bonded with resin and hot-pressed into sheets.

Particle damper

A particle damper is a passive vibration-control device, a cavity of small granular particles fixed to a structure, that dissipates vibration energy through inelastic collisions and friction.

Particle decay

Particle decay is the spontaneous process in which an unstable subatomic particle breaks down into two or more lighter particles, with excess energy carried away as kinetic energy.

Particle detector

A particle detector, also known as a radiation detector, is an instrument that records subatomic particles and measures their paths, momenta, energies, velocities, and charges, operating both at accelerators and beyond.

Particle filter

Particle filter, also known as Sequential Monte Carlo, is an algorithm that estimates the hidden state of a dynamic system using weighted random samples, introduced in 1993.

Particle filtering

Particle filtering is a sequential Monte Carlo method that estimates the hidden state of a nonlinear, non-Gaussian system from noisy observations, using weighted sample particles; the modern bootstrap filter dates to 1993.

Particle horizon

The particle horizon, also called the comoving horizon, is the maximum distance from which light could have reached us in the age of the universe.

Particle identification

Particle identification (PID) is the set of detector methods by which a particle physics experiment determines what kind of particle produced a track, usually by measuring mass from momentum and velocity.

Particle image velocimetry

Particle image velocimetry (PIV) is an optical, non-intrusive technique that measures a fluid flow's velocity field by imaging tracer particles between two closely spaced laser pulses.

Particle in a box

The particle in a box, also called the infinite square well, is a quantum model of a particle confined between impenetrable walls, with quantized energy levels and zero-point energy.

Particle MCMC

Particle MCMC (PMCMC) is a family of Monte Carlo algorithms combining particle filters with MCMC for Bayesian inference on non-linear state-space models, introduced by Andrieu, Doucet, and Holenstein in 2010.

Particle Photon

Particle Photon is a $19 Wi-Fi development board for the Internet of Things, announced by Particle in 2014 as the successor to the Spark Core.

Particle physics

Particle physics, also called high-energy physics, is the branch of science studying matter's fundamental constituents and forces through the Standard Model, tested in collider experiments at CERN.

Particle physics and representation theory

Particle physics and representation theory describe elementary particles as irreducible representations of the Poincaré group, classified by mass and spin, as Wigner showed in 1939.

Particle receiver

A particle receiver is a type of solar receiver for concentrating solar power in which falling sand-like particles, rather than fluid in tubes, absorb sunlight and store heat above 700 °C.

Particle shower

A particle shower is a cascade of ever more numerous, lower-energy particles formed when a high-energy electron, photon, or hadron enters matter and repeatedly converts its energy.

Oct 21, 2026

Particle Size

Particle size: the measured dimension of solid particles, reported as equivalent spherical or circular diameters. Methods include sieving, sedimentation, microscopy, laser diffraction (ISO 13320), and DLS (ISO 22412); results differ by method.

Particle smoothing

Particle smoothing is a family of sequential Monte Carlo methods that approximates the distributions of a state-space model's past states conditioned on all observations, in nonlinear and non-Gaussian settings.

Particle swarm optimization

Particle swarm optimization (PSO) is a population-based metaheuristic algorithm introduced by James Kennedy and Russell Eberhart in 1995, inspired by the social behavior of bird flocks and fish schools.

Particle system

A particle system is a computer graphics technique modeling effects like fire, smoke, and explosions as many small particles, introduced by William T. Reeves in 1983.

Particle tracking

Particle tracking, or the particle tracking method, detects particles in each frame of a microscopy video and links them into trajectories for measuring diffusion and motion.

Particle tracking velocimetry

Particle tracking velocimetry (PTV), also known as Lagrangian particle tracking, is an optical technique that measures 3D positions, velocities, and trajectories of tracer particles in flows.

Particle velocity

Particle velocity, symbol u, is the oscillatory velocity of the particles of a medium as a sound wave passes through, measured in meters per second.

Particle-in-cell simulation

Particle-in-cell (PIC) simulation is a numerical method that models plasmas by moving macroparticles through a fixed grid on which electromagnetic fields are solved self-consistently, developed at Los Alamos in the 1950s and 1960s.

Particle-induced X-ray emission

Particle-induced X-ray emission (PIXE) is an ion beam analysis technique in which MeV protons strike a sample, detecting elements from sodium to uranium at ppm sensitivity.