Saturday, October 5, 2024

Octonions and Aliens... and Gauge Symmetry, Oh MY!

Octonions are an eight-dimensional number system that are non-commutative and non-associative, meaning the order of multiplication matters, and grouping of multiplications can change the result; however, they are considered "alternative" which means they satisfy a weaker form of associativity, and are also power associative; they are considered the largest normed division algebra over real numbers, making them an extension of complex numbers and quaternions.


Key properties of octonions:
Dimensionality:
Eight dimensions, making them a higher dimensional extension of quaternions.

Non-associativity:
Unlike real numbers, complex numbers, and quaternions, the order of multiplication in octonions can affect the result.
Non-commutativity:
Multiplication is not commutative, meaning a * b is not necessarily equal to b * a. 
Alternative property:
While not fully associative, octonions satisfy the alternative property, which means that for any three octonions a, b, and c, the following holds: a(ba) = (ab)a and a(aa) = (aa)a.
Power associative:
Raising an octonion to a power is associative.

Normed division algebra:
Octonions form a normed division algebra, meaning every non-zero octonion has a multiplicative inverse.

Cayley-Dickson construction:
Octonions can be constructed using the Cayley-Dickson process, which is also used to build quaternions from complex numbers. 
C. elegans is remarkable in that every worm has the same exact number of cells: 959 in the adult hermaphrodite (not counting the cells that will become eggs or sperm). 302 of these cells are neurons. Researchers in Brenner's group created two first-of-their-kind resources documenting the details of this biology.

from Wikipedia
In mathematics, any Lagrangian system generally admits gauge symmetries, though it may happen that they are trivial. In theoretical physics, the notion of gauge symmetries depending on parameter functions is a cornerstone of contemporary field theory.

A gauge symmetry of a Lagrangian L is defined as a differential operator on some vector bundle E taking its values in the linear space of (variational or exact) symmetries of L. Therefore, a gauge symmetry of L depends on sections of E and their partial derivatives.[1] For instance, this is the case of gauge symmetries in classical field theory.[2] Yang–Mills gauge theory and gauge gravitation theory exemplify classical field theories with gauge symmetries.[3]

Gauge symmetries possess the following two peculiarities.
1) Being Lagrangian symmetries, gauge symmetries of a Lagrangian satisfy Noether's first theorem, but the corresponding conserved current Jμ takes a particular superpotential form Jμ=Wμ+dνUνμ where the first term Wμ vanishes on solutions of the Euler–Lagrange equations and the second one is a boundary term, where Uνμ is called a superpotential.[4]

2) In accordance with Noether's second theorem, there is one-to-one correspondence between the gauge symmetries of a Lagrangian and the Noether identities which the Euler–Lagrange operator satisfies. Consequently, gauge symmetries characterize the degeneracy of a Lagrangian system.[5]
Note that, in quantum field theory, a generating functional may fail to be invariant under gauge transformations, and gauge symmetries are replaced with the
BRST symmetries, depending on ghosts and acting both on fields and ghosts.[6]
Hopf Fibration

No comments:

Post a Comment