Physical world and mathematics

Differential scattering cross-section

The differential scattering cross-section, dσ/dΩ, measures how strongly particles scatter into a given solid angle; integrating it over all angles gives the total cross section.

Differential thermal analysis

Differential thermal analysis (DTA) is a thermal analysis technique measuring the temperature difference between a sample and an inert reference during controlled heating, detecting transitions without mass change.

Differential topology

Differential topology is the branch of topology studying differentiable manifolds and mappings, using tools like transversality, Morse theory, and bordism, with landmark results including Milnor's 1956 exotic 7-spheres.

Differential-phase-shift quantum key distribution

Differential-phase-shift quantum key distribution (DPS-QKD) is a quantum key distribution protocol proposed by Inoue et al. in 2002 that encodes key bits in the phase difference between consecutive weak coherent pulses.

Differentially closed field

A differentially closed field is a field with a derivation containing enough solutions of differential equations, the differential analog of an algebraically closed field, in a precise first-order sense.

Differentiation of trigonometric functions

Differentiation of trigonometric functions gives the derivatives of sine, cosine, tangent, cotangent, secant, and cosecant: in radians, differentiating sine gives cosine, and the derivatives cycle back after four steps.

Differentiation rules

Differentiation rules, also called differentiation formulas, are calculus identities that give the derivative of a function built from simpler parts, such as the product, quotient, and chain rules.

Diffraction

Diffraction is the bending and spreading of waves around an opening or obstacle, exhibited by sound, ocean waves, light, and electron matter waves, strongest when sizes match the wavelength.

Oct 22, 2026

Diffraction before destruction

Diffraction before destruction is a principle in X-ray crystallography in which an ultrashort, intensely bright X-ray pulse records the diffraction pattern of a sample before radiation damage destroys it.

Diffraction contrast

Diffraction contrast is a principal contrast mechanism in transmission electron microscopy, first observed in 1956, in which dislocations and stacking faults bend or strain the crystal lattice so Bragg diffraction makes them appear dark or bright.

Diffraction contrast tomography

Diffraction contrast tomography (DCT) is an X-ray imaging technique that reconstructs the three-dimensional grain shapes and orientations of polycrystalline materials, first reported by Wolfgang Ludwig and colleagues in 2008.

Diffraction from slits

Diffraction from slits, also called diffraction formalism, is the spreading and interference of waves passing through narrow openings, the classic demonstration that light is a wave.

Diffraction grating

A diffraction grating is an optical component with many parallel grooves or slits that splits light into its component wavelengths, each emerging at a different angle.

Diffraction microscopy

Diffraction microscopy, also known as coherent diffractive imaging (CDI), is a lensless imaging method that reconstructs a specimen's image computationally from its measured diffraction pattern.

Diffraction order

A diffraction order is one of the discrete output directions in which a diffraction grating sends light, labeled by the integer m in the grating equation.

Diffraction tomography

Diffraction tomography is an inverse-scattering imaging method that reconstructs the internal structure of weakly scattering objects from diffracted waves, unlike ray-based tomography, with applications in geophysics, breast ultrasound, and cell imaging.

Oct 22, 2026

Diffraction-limited storage ring

A diffraction-limited storage ring (DLSR) is an electron storage ring x-ray source whose emittance is low enough that the emitted x-rays are nearly fully spatially coherent.

Diffraction-limited system

A diffraction-limited system, or optical diffraction limit, is an optical instrument whose imaging performance is limited by the wave nature of light rather than by flaws in its optics.

Diffractive scattering

Diffractive scattering is a class of high-energy particle collisions in which one or both incoming hadrons emerge nearly intact, separated from the produced system by a large rapidity gap.

Diffractometry

Diffractometry is a family of techniques for determining the structure, phase composition, or texture of matter by analyzing diffraction patterns from X-rays, electrons, or neutrons, a field born in 1912.

Diffuse correlation spectroscopy

Diffuse correlation spectroscopy (DCS) is a noninvasive optical technique that measures a blood flow index in deep tissue, such as brain, muscle, and tumors, at the bedside.

Diffuse interface method

The diffuse interface method is a numerical modeling approach that treats the boundary between two phases as a smooth transition region described by a continuous order parameter.

Diffuse interstellar bands

Diffuse interstellar bands (DIBs) are about 500 broad absorption features in starlight passing through interstellar gas and dust, first noticed by Mary Lea Heger in 1919.

Diffuse reflectance infrared Fourier transform spectroscopy

Diffuse reflectance infrared Fourier transform spectroscopy, also known as diffuse reflectance infrared spectroscopy or DRIFTS, is an infrared technique for analyzing powders without pellet pressing, widely used in catalyst research.

Diffuse reflectance spectroscopy

Diffuse reflectance spectroscopy (DRS) is an optical technique measuring light scattered back from turbid materials, powders, and biological tissue to recover absorption and scattering properties, used in medicine and industry.

Diffuse reflection

Diffuse reflection scatters light or electromagnetic radiation into many directions rather than a single mirror direction, occurring when a surface is rough on the scale of its wavelength.

Diffuse scattering

Diffuse scattering is the component of a diffraction pattern spread continuously through reciprocal space rather than concentrated in sharp Bragg peaks, arising from thermal motion and disorder.

Diffuse sky radiation

Diffuse sky radiation, also called diffuse horizontal irradiance (DHI), is the sunlight scattered by molecules, aerosols, and clouds that reaches the ground from the whole sky rather than directly from the sun.

Diffuse supernova neutrino background

The diffuse supernova neutrino background (DSNB), also called the supernova relic neutrino background, is the accumulated neutrino flux from all past core-collapse supernovae, first indicated by Super-Kamiokande in 2026.