All articles starting with R
22,461 articles
Relative consistency
Relative consistency is a property of formal theories: a theory S is consistent relative to T when Con(T) implies Con(S), since strong theories like ZF cannot prove their own consistency.
Relative dating
Relative dating is a set of geological and archaeological methods for placing rocks, fossils, and artifacts in chronological order without assigning numerical ages in years.
Relative density
Relative density, or specific gravity, is the ratio of a substance's density to that of a reference substance, usually water; it is a dimensionless number independent of units.
Relative Entropy Policy Search
Relative Entropy Policy Search (REPS) is a reinforcement learning algorithm introduced by Jan Peters and colleagues in 2010 that bounds the KL divergence between successive policies.
Relative equilibrium
A relative equilibrium is a solution of the Newtonian N-body problem in which bodies keep fixed mutual distances while rotating rigidly at constant angular velocity.
Relative humidity
Relative humidity is the ratio, expressed as a percent, of water vapor in the air to the amount that would saturate it at the same temperature.
Relative income hypothesis
The relative income hypothesis is a theory of consumption proposed by Harvard economist James Duesenberry in 1949, holding that household saving depends on income relative to other households.
Relative intensity noise
Relative intensity noise (RIN) is a measure of the random fluctuations in a laser's optical power, normalized to its average power and usually specified in dBc/Hz.
Relative key
Relative key (German Paralleltonart): a major and minor key sharing the same key signature and seven pitches but different tonics, e.g. C major and A minor; tonic lies a minor third apart.
Relative lability and selective cleavage of silyl ethers
Silyl ethers are alcohol protecting groups whose lability depends on steric bulk, from acid-sensitive TMS to robust TBDPS, enabling selective protection of primary alcohols and stepwise removal with acid, fluoride, or TBAF.
Relative molecular mass
Relative molecular mass (Mr), formerly called molecular weight, is the dimensionless ratio of a molecule's average mass to one twelfth of a carbon-12 atom's mass.
Relative navigation
Relative navigation is the determination of a spacecraft's position, velocity, and attitude relative to another vehicle rather than a ground reference, enabling autonomous rendezvous, docking, on-orbit servicing, and planetary landing.
Relative permittivity
Relative permittivity, also called the dielectric constant, is the ratio of a material's permittivity to that of vacuum; filling a capacitor with a dielectric multiplies its capacitance.
Relative polycythaemia
Relative polycythaemia (Gaisbock syndrome, spurious or apparent erythrocytosis, ICD-11 3A81.2) is a raised hematocrit with normal red cell mass caused by contracted plasma volume, from dehydration, diuretics, smoking, obesity, or hypertension; treated by hydration and risk-factor correction, not phlebotomy.
Relative pose estimation
Relative pose estimation is a computer vision method that determines the rotation and translation direction of one camera relative to another from point correspondences between two images.
Relative risk
Relative risk (risk ratio, RR): ratio of event probability in an exposed group to that in an unexposed group; RR=1 means no association. Used in cohort studies and trials; case-control studies use odds ratios instead.
Relative sensitivity factor
The relative sensitivity factor (RSF) is a calibration coefficient in secondary ion mass spectrometry that converts measured ion intensity ratios into atomic concentrations, chiefly for trace elements below 1%.
Relative strength index
The relative strength index (RSI) is a momentum oscillator developed by J. Welles Wilder that measures price movement speed on a 0 to 100 scale.
Relativism
Relativism is the family of philosophical views holding that truth, moral and epistemic standards, and justification hold only relative to a framework of assessment. Also called alethic, moral, or epistemic relativism; traced to Protagoras' 'man is the measure of all things' and distinguished from skepticism, contextualism, and realism.
Relativistic angular momentum
Relativistic angular momentum is the generalization of angular momentum to special relativity, where it becomes an antisymmetric tensor with six components: three generate spatial rotations and three generate Lorentz boosts.
Relativistic beaming
Relativistic beaming, also called Doppler boosting or the headlight effect, is the concentration of radiation from a near-light-speed source into a narrow forward cone, brightening approaching jets.
Relativistic center of mass
The relativistic center of mass is the collective position variable of a system in relativity theory; unlike the Newtonian one, it is not a single unambiguous point.
Relativistic collision kinematics
Relativistic collision kinematics is the study of two-body collisions using conservation of total energy and momentum in special relativity, governing the energy available to create new particles.
Relativistic collisionless shocks
A relativistic collisionless shock is a shock wave moving at nearly the speed of light through tenuous plasma, mediated by collective electromagnetic fields rather than particle collisions.
Relativistic corrections in satellite navigation
Relativistic corrections in satellite navigation account for the difference between ground and orbital atomic clocks by compensating for gravitational and kinematic shifts, preventing massive location errors.
Relativistic Doppler effect
The relativistic Doppler effect, also called the relativistic Doppler shift, is the change in frequency and wavelength of light from a moving source, calculated consistently with special relativity.
Relativistic electromagnetism
Relativistic electromagnetism treats electric and magnetic fields as one entity whose components depend on the observer's frame, with what one observer calls an electric field another sees as a mixture.
Relativistic ephemerides
A relativistic ephemeris is a numerically integrated table of Solar-System body positions and velocities whose equations of motion include general-relativistic corrections, as in JPL's DE series.
Relativistic Euler equations
The relativistic Euler equations are the equations of motion of a perfect (non-viscous) fluid in a form consistent with special or general relativity, governing fluids at speeds where relativistic effects matter.
Relativistic force
In special relativity, force is redefined as the four-force, the rate of change of a particle's four-momentum with respect to proper time, reducing to Newton's second law at low speeds.