All articles A–Z

Inverse Galois problem

The inverse Galois problem asks whether every finite group occurs as the Galois group of a finite Galois extension of the rational numbers; it remains open in general.

Inverse gas chromatography

Inverse gas chromatography (IGC) is a chromatographic technique in which volatile probes of known properties measure the surface and bulk properties of a packed material.

Inverse Gaussian distribution

The inverse Gaussian distribution, also called the Wald distribution, is a continuous probability distribution on positive numbers, arising as the first passage time of Brownian motion.

Inverse hyperbolic functions

The inverse hyperbolic functions, also known as the area hyperbolic functions, are the six inverses of the hyperbolic functions, written arcsinh, arccosh, arctanh, and the reciprocals.

Inverse iteration

Inverse iteration is an eigenvalue algorithm that finds the eigenvector whose eigenvalue lies nearest a chosen shift, working by the power method applied to the inverse shifted matrix.

Inverse kinematics

Inverse kinematics (IK) computes the joint angles of a robot arm or animated character that place its end effector at a desired position and orientation.

The inverse limit, also called the projective limit, is a mathematical construction that assembles objects connected by backward-pointing maps into a single object of compatible choices, used across algebra, topology, and number theory.

Inverse Matrix Technology (逆矩阵科技)

Inverse Matrix Technology (逆矩阵科技), also branded Physis, is a Chinese world-model AI startup founded in Beijing in 2026 by Peking University researchers Chen Boyuan and Ji Jiaming.

Inverse optimization

Inverse optimization is a method that infers the objective function, and sometimes constraints, of an optimization model from observed decisions assumed to be optimal, reversing traditional optimization.

Inverse photoemission spectroscopy

Inverse photoemission spectroscopy (IPES), formerly bremsstrahlung isochromat spectroscopy, probes unoccupied electronic states above the Fermi level: electrons of known energy strike a sample, and emitted photons are detected.

Inverse probability weighting

Inverse probability weighting (IPW) is a statistical technique that weights each observed unit by the reciprocal of its probability of being observed, correcting selection bias.

Inverse problem

An inverse problem, also called inverse theory or inverse modeling, is the task of determining the unknown causes of observed consequences using a forward model; it is usually ill-posed and handled by regularization or Bayesian inference.

Inverse Problems

Inverse Problems is an interdisciplinary peer-reviewed journal published by IOP Publishing since 1985, combining mathematical and experimental papers with theoretical, numerical, and practical approaches to inverse problems.

Inverse problems in plasma diagnostics

Inverse problems in plasma diagnostics reconstruct unmeasurable plasma quantities, such as emissivity or current density, from indirect detector measurements by inverting an ill-posed forward model.

Inverse protein folding

Inverse protein folding is the computational task of finding amino acid sequences that fold into a given three-dimensional protein backbone, the sequence-design step of de novo protein design.

Inverse psoriasis

Inverse psoriasis, also called flexural psoriasis, is psoriasis in the skin folds, forming shiny, smooth red plaques in the groin, armpits, and under the breasts.

Inverse reinforcement learning

Inverse reinforcement learning (IRL) is a machine learning method that infers the reward function an agent is optimizing from observed behavior, first formalized by Ng and Russell in 2000.

Inverse scattering

Inverse scattering is a mathematical method that reconstructs an object's shape or a medium's refractive index and scattering potential from measurements of scattered waves, a nonlinear and ill-posed problem.

Inverse scattering transform

The inverse scattering transform, also called the nonlinear Fourier transform, solves integrable nonlinear PDEs like the KdV equation by converting them into linear scattering problems.

Inverse seesaw mechanism

The inverse seesaw mechanism is a neutrino mass model, proposed by Mohapatra and Valle in 1986, in which small neutrino masses come from a small lepton-number-violating parameter.

Inverse semigroup

An inverse semigroup is a semigroup in which every element has a unique inverse, the algebraic structure capturing partial symmetries, defined independently by Vagner and Preston in the 1950s.

Inverse synthetic-aperture radar imaging

Inverse synthetic-aperture radar (ISAR) imaging is a signal processing technique that forms high-resolution images of moving targets, using the target's own motion to synthesize the radar aperture.

Inverse transform sampling

Inverse transform sampling, also called inversion, generates random samples from a probability distribution by applying the inverse of its cumulative distribution function to a uniform random number.

Inverse trigonometric functions

The inverse trigonometric functions, also known as cyclometric or arc functions, are six functions that invert the sine, cosine, and tangent to return the angle for a given value.

Inverse vulcanization

Inverse vulcanization is a copolymerization process, introduced by Jeffrey Pyun in 2013, in which molten elemental sulfur is crosslinked by organic molecules to form stable polymers.

Oct 22, 2026

Inverse-designed mechanical metamaterials

Inverse-designed mechanical metamaterials are artificial structures whose geometry is found by working backward from a prescribed property, such as a stress-strain curve or band gap.

Inverse-gamma distribution

The inverse-gamma distribution, or inverted gamma distribution, is a continuous probability distribution obtained as the reciprocal of a gamma-distributed variable, used mainly as a conjugate prior for a normal variance.

Inverse-square law

The inverse-square law is the physical rule that a quantity spreading from a point source, like gravity or light, falls off as the square of the distance.

Oct 22, 2026

Inverse-vulcanized sulfur polymers

Inverse-vulcanized sulfur polymers are crosslinked, high-sulfur materials made by copolymerizing molten elemental sulfur with unsaturated organic monomers, used in lithium–sulfur batteries, optical devices, and mercury removal from water.