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Fission fragment angular momentum puzzle
The fission fragment angular momentum puzzle is the unresolved question of why fission fragments carry spins near 7 ħ even from spin-zero nuclei, open since the early 1970s.
Fission isomer
A fission isomer is a long-lived excited nuclear state, also called a shape isomer, trapped in a superdeformed second minimum that decays by spontaneous fission.
Fission product yield
Fission product yield is the probability, usually in percent per fission, that a given nuclide or mass chain is produced when a heavy nucleus undergoes fission; yields are key to reactor physics and decay heat.
Fission track dating
Fission track dating, also called fission track analysis, is a radiometric method that determines the age of apatite, zircon, and volcanic glass by counting damage trails from uranium fission.
Fission-track thermochronology
Fission-track thermochronology is a dating method using damage trails from spontaneous uranium fission in minerals such as apatite and zircon to reconstruct rocks' low-temperature thermal histories.
Fitts's law
Fitts's law is a model of rapid aimed movement, introduced by Paul M. Fitts in 1954, in which movement time is a linear function of movement amplitude and target width.
FitzHugh–Nagumo model
The FitzHugh–Nagumo model is a simplified two-variable system of differential equations describing excitability in neurons, derived from the four-variable Hodgkin–Huxley model in 1961 and 1962.
Five whys
Five whys, also called the 5 Whys, is a root cause analysis technique that repeats the question why, about five times, to trace a problem to its underlying cause.
Five-dimensional space
Five-dimensional space is a space with five independent dimensions, in which a point is specified by five coordinates; in physics it often means five-dimensional spacetime with one extra spatial dimension.
Five-hole probe
A five-hole probe is a pneumatic instrument, adapted from the Pitot-static probe, whose five pressure ports yield flow direction, velocity, total pressure, and static pressure via calibration.
Five-hundred-meter Aperture Spherical Telescope
The Five-hundred-meter Aperture Spherical Telescope, known as FAST or Tianyan, is a 500-meter radio telescope in Guizhou, China, completed in 2016, the world's largest single-dish radio telescope.
Five-qubit code
The five-qubit code, also known as the Laflamme code, is a quantum error-correcting code denoted [[5,1,3]] that encodes one logical qubit into five, the minimum for correcting any single-qubit error.
Fixed point (mathematics)
A fixed point in mathematics, also called an invariant point, is a point that a function maps to itself, so Λ(x) = x; fixed point theorems give conditions for their existence.
Fixed stars
The fixed stars, or sphere of fixed stars, are the stars that keep the same positions relative to one another on the sky, unlike the wandering Sun, Moon, and planets.
Fixed-point arithmetic
Fixed-point arithmetic is a method of computing with real numbers by representing each value as an integer scaled by a fixed factor, with the radix point implicit.
Fixed-point combinator
The fixed-point combinator, known as the Y combinator, is a lambda calculus term Y satisfying Y f = f(Y f), supplying recursion in a language without named definitions.
Fixed-point iteration
Fixed-point iteration, also called Picard iteration or successive substitution, is a numerical method that solves equations by repeatedly applying a function to an initial guess.
Fixed-point logic
Fixed-point logic is a family of extensions of first-order predicate logic with operators defining relations as fixed points; its best-known member, least fixed-point logic, captures polynomial time on finite ordered structures.
Fixed-target experiment
A fixed-target experiment is a particle-physics experiment in which an accelerated beam strikes a stationary target, producing collisions measured by downstream detectors; it discovered the charm and bottom quarks.
Fizeau interferometer
The Fizeau interferometer is an optical instrument that measures the shape of optical surfaces by interfering light from a reference surface with light from the test surface.
FK Comae Berenices
FK Comae Berenices (FK Com, HD 117555) is a rapidly rotating, chromospherically active yellow giant in Coma Berenices, the prototype of the FK Comae stars, likely a recent binary merger.
FKG inequality
The FKG inequality, or Fortuin–Kasteleyn–Ginibre inequality, is a correlation inequality of probability theory stating that two increasing events are positively correlated; proved in 1971, it is a standard tool in percolation and statistical mechanics.
Flag algebra
A flag algebra is a formal calculus in extremal combinatorics, introduced by Alexander Razborov in 2007, that derives bounds on graph and hypergraph density problems via computer-assisted semidefinite programs.
Flag manifold
A flag manifold is the space of all flags, nested sequences of linear subspaces with prescribed dimensions, in a vector space, generalizing Grassmannians and projective space.
Flag qubit
A flag qubit is an ancilla qubit in quantum error correction that detects faults in syndrome-extraction circuits, enabling fault tolerance with far fewer extra qubits.
Flame atomic absorption spectroscopy
Flame atomic absorption spectroscopy (FAAS) is a robust, inexpensive analytical technique that measures element concentrations in a flame, covering more than 60 elements including sodium, calcium, zinc, and iron.
Flame atomic emission spectroscopy
Flame atomic emission spectroscopy (F-AES), also called flame photometry, is an analytical technique that measures metal concentrations by nebulizing a sample into a flame and measuring emitted light.
Flame ionization detection
Flame ionization detection (FID) is a gas chromatography method that burns organic compounds in a hydrogen-air flame and measures the ions formed; developed in 1957, it became the most widely used gas chromatography detector.
Flame test
A flame test is a simple qualitative chemistry test that identifies metal elements or ions in a sample from the characteristic color they give a flame.
Flamm's paraboloid
Flamm's paraboloid is the funnel-shaped surface of revolution that embeds the equatorial spatial slice of the Schwarzschild black hole geometry, described by Ludwig Flamm in 1916.