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Ewine van Dishoeck
Ewine van Dishoeck is a Dutch molecular astrophysicist and astrochemist, professor at Leiden Observatory since 1995, who won the 2018 Kavli Prize for studying water and organic molecules in star- and planet-forming clouds.
Ewold Verhagen
Ewold Verhagen (born 1980) is a Dutch experimental physicist in cavity optomechanics who leads the Photonic Forces group at AMOLF and is a part-time professor at Eindhoven University of Technology.
EX Hydrae
EX Hydrae (EX Hya) is an eclipsing intermediate polar in Hydra, a magnetic cataclysmic variable where a white dwarf accretes gas with 98-minute orbital and 67-minute spin periods.
EX Lupi
EX Lupi (EX Lup) is a low-mass young star in the Lupus star-forming region, the prototype of the EXor eruptive variables, known for repeated accretion outbursts.
Exact diagonalization
Exact diagonalization is a numerical method that builds and diagonalizes the Hamiltonian matrix of a quantum many-body system in a finite basis, limited to clusters of roughly twenty sites.
Exact differential equation
An exact differential equation is a first-order equation M dx + N dy = 0 with a potential function F whose solutions are level curves F = C.
Exact plane wave spacetime
An exact plane wave spacetime is a non-flat vacuum solution of Einstein's equations with the symmetry of a plane electromagnetic wave, defined by Bondi, Pirani, and Robinson in 1959.
Exact sequence
An exact sequence is a sequence of algebraic objects, typically modules, connected by homomorphisms in which each map's image equals the next map's kernel, the central notion of homological algebra.
Exact solutions in general relativity
Exact solutions in general relativity, also called exact solutions of Einstein's field equations, are spacetime metrics solving Einstein's equations in closed form, including black holes and cosmologies.
Exact test
An exact test is a statistical hypothesis test whose Type I error rate stays at or below the significance level in finite samples, including Fisher's exact test.
Exaltation (astrology)
Exaltation is a traditional astrological concept in which each of the seven classical planets has one zodiac sign of heightened expression, with the opposite sign its fall.
Exatecan
Exatecan (DX-8951f), Daiichi Pharmaceutical's water-soluble hexacyclic camptothecin analog topoisomerase I inhibitor; potent but myelotoxic, discontinued after phase III pancreatic cancer failure, now used as an ADC payload (deruxtecan).
Exceptional field theory
Exceptional field theory (ExFT) is a reformulation of maximal supergravity, the low-energy limit of string and M-theory, in which U-duality symmetries become geometric symmetries of an extended spacetime.
Exceptional point
An exceptional point is a singularity of a non-Hermitian, energy-exchanging system where eigenvalues and eigenvectors coalesce, underpinning applications in optics, sensing, and microring lasers since the 1998 PT-symmetry work of Bender and Boettcher.
Exceptional points in metamaterials
Exceptional points in metamaterials are engineered degeneracies in non-Hermitian wave systems where eigenvalues and eigenvectors coalesce, studied in optics, acoustics, and mechanics and proposed for enhanced sensing despite noise limits.
Exceptional points in photonics
Exceptional points in photonics are singularities of non-Hermitian optical systems such as resonators with gain or loss, where eigenvalues and eigenstates coalesce, underpinning applications in sensing, lasing, and nonreciprocal photonics.
Exceptional-point enhanced sensing
Exceptional-point enhanced sensing is a scheme that operates sensors at an exceptional point, so their response to a small perturbation grows as a root rather than linearly.
Excess property
An excess property is the difference between a thermodynamic property of a real liquid mixture and its value in an ideal mixture at the same conditions.
Exchange bias
Exchange bias, also called exchange anisotropy, is a magnetic effect in which a ferromagnet's hysteresis loop shifts after field cooling through an antiferromagnet's Néel temperature.
Exchange current density
Exchange current density (symbol j₀) is the current density at which an electrode's anodic and cathodic partial reactions are equal at its equilibrium potential, so no net current flows.
Exchange force
An exchange force is a force between particles that quantum field theory describes as the exchange of a virtual carrier particle, such as the photon mediating electromagnetic force.
Exchange interaction
The exchange interaction is an effective quantum-mechanical coupling between neighboring electron or atomic spins, arising from Coulomb repulsion and the Pauli principle, that causes ferromagnetism and antiferromagnetism.
Exchange matrix
The exchange matrix J is the square matrix with ones on the antidiagonal and zeros elsewhere; multiplying by it reverses a matrix's rows or columns.
Exchange-only silicon triple-dot qubit
The exchange-only silicon triple-dot qubit is a spin qubit encoding one qubit in three electron spins on silicon quantum dots, controlled entirely by exchange interaction.
Exchangeability
Exchangeability, known in older literature as equivalence, permutability, or symmetry, is a symmetry property of a probability distribution, introduced by Bruno de Finetti and central to Bayesian statistics.
Exchangeable random variables
Exchangeable random variables are a collection whose joint probability distribution is unchanged when their labels are permuted, introduced by Bruno de Finetti and weaker than independence.
Excimer laser
An excimer laser is a pulsed gas laser that emits ultraviolet light from transient noble-gas halide molecules, chiefly used in chipmaking lithography and LASIK eye surgery.
Exciplex
An exciplex is an electronically excited complex of two different molecules, non-bonding in the ground state; it falls apart when the excitation is lost, and partners of the same structure form an excimer.
Excitability (chemistry)
Excitability in chemistry is the property of a chemical system that rests in a stable steady state but fires a large excitation event when perturbed above a critical threshold.
Excitation spectroscopy
Excitation spectroscopy is a fluorescence-detected form of absorption spectroscopy that scans the excitation wavelength while recording emission at a fixed wavelength, used on molecules, phosphors, and quantum dots.