Induction coil

An induction coil is any object used to stabilize an edge (or edges) of another pattern without touching. While still lifes and oscillators can be used as induction coils, there are also many induction coils that are not stable by themselves (such as table), which is what the term is more commonly used to refer to.

Examples

The tubs on the sides of the Gray counter are used as induction coils, as are the blocks and snakes used in the Hertz oscillator and the crinkly heptomino at the bottom of the mathematician.

The Gray counter is stabilized by two tubs.

The Hertz oscillator is stabilized by two blocks and two snakes.

The Mathematician is mutually stabilized by a crinkly heptomino.

Naming of induction coil systems

Main article: Pattern naming

Still lifes which contain induction coils are named depending on how the induction coils interact with each other.

This only counts cases where the two induction coils have a single, straight inducting face, and the resulting arrangement is disjoint (i.e. has at least two islands).

Two identical induction coils

If the induction coils in question are themselves mirror-symmetric, there are two possibilities:
- Mirrored [X]: where the arrangement has both mirror and rotational symmetry
- Rotated [X]: where the arrangement only has rotational symmetry, i.e. the components are skewed

If the induction coils are asymmetric, there are five possibilities:
- Cis-mirrored [X]: Has mirror symmetry, and is not skewed
- Trans-mirrored [X]: Has rotational symmetry, and is not skewed
- Shift-mirrored [X]: Asymmetric, skewed
- Cis-rotated [X]: Has rotational symmetry, higher-density zones nearer center
- Trans-rotated [X]: Has rotational symmetry, higher-density zones near outside

Two different induction coils

If the induction coils in question are themselves mirror-symmetric, there are two possibilities:
- [X] and [Y]: where the arrangement has mirror symmetry
- Skew [X] and [Y]: the overall pattern is asymmetric

If only one induction coil is mirror-symmetric, there are three(?) possibilities:
- Meta-[X] and [Y]: both faces are aligned
- Ortho-[X] and [Y]: skewed; dense part of asymmetric object is near center
- Para-[X] and [Y]: skewed; dense part of asymmetric object is near outside

If both induction coils are asymmetric, there are six possibilities:
- Cis-[X] and [Y]: roughly mirror symmetric
- Trans-[X] and [Y]: roughly rotationally symmetric
- Shift-[X] and [Y]: The patterns point in the same direction, and the first's heavy part aligns with the second's light part
- Meta-[X] and [Y]: The constituent patterns point in opposite directions and their "light" parts align
- Para-[X] and [Y]: The patterns point in the same direction, and the first's light part aligns with the second's heavy part
- Ortho-[X] and [Y]: The constituent patterns point in opposite directions and their "heavy" parts align

Induction coil stabilised by an object which is stable by itself

When an induction coil is stabilised by a still life, the still life is said to be on the induction coil (e.g. block on table). This is in contrast to and, which is used for two mutually-stabilising induction coils (e.g. table and dock).

Working list

To adjust patterns manually, it is convenient to have the small and useful induction coils handy. However, as the examples show, stabilizing a long edge can usually be accomplished by judiciously placing snakes, blocks and occasionally tubs along its length. Due consideration must be given to their spacing, and especially the overhang at edges and corners. Common short coils follow:

length	Preblock stabilizer	-	-
3, 3 high	House	Bookend	Bun
3, 4 high	-	Teardrop	Wing	Dove
3, 5 high	-	Cover
4, 2 high	-	Table	-
4, 3 high	Dock	Cap	Long bookend
4, 4 high		Anvil	Racetrack
5, 3 high	Very long house	-
5, 4 high		Worm
6, 3 high		Bookend siamese table