Noether's theorem links continuous symmetries to conserved currents in Lagrangian field theories.
For infinitesimal transformations δx_ν = ε_r X_rν and δη_ρ = ε_r Ψ_rρ, the conserved current is
j_r^ν = [(∂L/∂(∂_ν η_ρ)) ∂_σ η_ρ - L δ^ν_σ] X_rσ - (∂L/∂(∂_ν η_ρ)) Ψ_rρ, satisfying ∂^ν j_r^ν = 0.
Specializing to translations with X_μν = δ_μν and Ψ_rρ = 0 yields the canonical energy-momentum tensor T^μν.
It is used to establish conservation of energy and momentum from spacetime translation invariance in field theories, as in calculations for particle collisions at accelerators.
Standard axes often miss the primary directions of data spread. PCA rotates the coordinate system to align new axes with maximum variation.
- The left panel plots original points on x and y, showing a clear diagonal pattern in the colored dots.
- The middle panel shows the axes rotated so PC1 runs along the main trend and PC2 crosses it at right angles. - The right panel projects the points onto a single line using only PC1, preserving their order and most variation.
It is used to simplify high-dimensional sensor data in quality control for manufacturing processes.
DNA twists into several conformations depending on conditions and sequence.
The top panels show end views revealing each form's symmetry, and the bottom panels show the helical structures.
> A-DNA is short and wide right-handed, forming in dry states.
> B-DNA is the usual right-handed helix in cells with 10.5 base pairs per turn.
> C-DNA is right-handed with different parameters in low-humidity salt conditions.
> Z-DNA is left-handed and zigzag, common with alternating bases under stress.
Scientists apply knowledge of these forms to create targeted DNA drugs for treating diseases like cancer.
Need to find how much space a shape takes up?
These volume formulas cover the basics for common solids.
- Cube: V = a³.
- Cuboid: V = l × w × h.
- Cylinder: V = πr²h.
- Cone: V = ⅓πr²h.
- Sphere: V = (4/3)πr³.
- Hemisphere: V = ⅔πr³.
- Triangular prism: V = ½bh × L.
- Pyramid: V = ⅓ × base area × height.
Handy reminders show the cone as one-third a cylinder and the pyramid as one-third a prism with matching base and height.
It calculates the amount of liquid a tank can hold or the concrete required for a foundation slab.
A circle has its center as the reference point. From there, the radius measures out to the circumference that traces the entire outer path.
> The diameter cuts directly across through the center. > Straight connections between two points on the edge are called chords.
> Lines that just touch the circle once are tangents, whereas those that go through it twice are secants.
> The curved edge pieces are arcs. These combine into sectors using two radii or segments using one chord.
It is used to figure out sizes and shapes when building or planning anything round, from wheels to roundabouts.
Deciding convergence of an infinite series ∑_{k=1}^∞ a_k starts with the ratio test.
Form L as the limit as k goes to infinity of |a_{k+1} / a_k|.
- When L is less than 1 the series converges.
- When L is greater than 1 the series diverges.
- When L equals 1 the test reaches no conclusion.
This procedure helps verify convergence in the power series solutions for ordinary differential equations that describe mechanical systems like damped oscillators.
Circle area and related measurements follow standard formulas.
- The area of a circle is A = πr² while its circumference is C = 2πr.
- A sector's area with central angle θ degrees is A = (θ/360)πr².
- Arc length for the same angle is L = (θ/360)2πr.
- The area of an annulus is A = π(R² - r²) where R is the outer radius and r the inner radius.
Mechanics use these to determine the material area in ring gaskets for engines and pumps.
82 years ago today; July 13, 1944, Ernő Rubik was born in Hungary.
The inventor of the Rubik’s Cube (1974), one of the world’s best-selling toys of all time.
Its mathematics rooted in group theory, combinatorics, and algorithms for solving permutations has turned a colorful puzzle into a fun gateway to abstract algebra and mathematical thinking for millions.
Regular polygons reveal a consistent mathematical pattern in their interior angles.
For a polygon with n sides, the sum of all interior angles equals (n-2)×180° while each individual angle is [(n-2)×180°]/n.
It is used to ensure precise symmetry when creating tiles, road signs, and structural components in manufacturing and construction.
Quantum mechanics centers on the time-dependent Schrödinger equation, which describes how a particle's wavefunction changes with time and position.
i ħ ∂Ψ/∂t = − (ħ²/2m) ∇² Ψ + V Ψ
The left side handles time evolution using the imaginary unit and reduced Planck constant. The right side includes the mass-dependent kinetic term with the Laplacian for spatial changes and the potential energy term for forces acting on the particle.
It is used to calculate quantized energy levels in atoms and molecules, forming the basis for chemistry and electronics design.
Leonhard Euler's work established several core mathematical principles that continue to shape technical fields.
Among them are the identity setting e to the i pi power plus one to zero, the Gaussian integral result of square root of pi, the limit and series definitions for the number e, Euler's formula for e to the i x, calculus operations on the exponential function, properties of the natural logarithm, and the standard definitions for the hyperbolic functions.
These principles support modeling in numerous domains. It is used to calculate probabilities under the normal distribution and design exponential amplifiers in electronics.
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