Site type API

See Site types and layouts for the narrative version and Site types and spin models for the physics.

Abstract type and interface

LatticeCore.AbstractSiteType — Type

AbstractSiteType

Abstract supertype for site types — value-level descriptors of the physical degree of freedom living on a lattice site.

Concrete subtypes are deliberately lightweight (typically singletons or thin parametric singletons) so they can be embedded in lattice structs and used as a dispatch key by MC models.

Required interface

state_type(st)::Type — the Julia type used to store a state
random_state(rng, st) — sample a uniformly random state

Optional interface

zero_state(st) — a canonical zero state (if defined)
domain(st) — iterable over the state space (for small discrete site types)
element_type(st)::AbstractLatticeElement — which geometric element the DOF lives on. Defaults to VertexCenter. Override for bond / plaquette-centered variables such as dimer or gauge fields.

See dev/note/04_architecture/04_site_type/README.md.

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LatticeCore.state_type — Function

state_type(st::AbstractSiteType) → Type

Julia type used to store a state of site type st.

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LatticeCore.random_state — Function

random_state(rng, st::AbstractSiteType)

Sample a uniformly random state on site type st.

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LatticeCore.zero_state — Function

zero_state(st::AbstractSiteType)

Canonical zero state (e.g. 0 for Ising, 0.0 for XY). Not all site types have to define this.

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LatticeCore.domain — Function

domain(st::AbstractSiteType)

Iterable over the state space. Only meaningful for small discrete site types (Ising, Potts); continuous types leave this unimplemented.

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LatticeCore.element_type — Function

element_type(st::AbstractSiteType) → AbstractLatticeElement

Which geometric element the DOF lives on. Defaults to VertexCenter. Override for bond / plaquette / cell-centered site types.

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Built-in site types

LatticeCore.IsingSite — Type

IsingSite{T <: Integer}()

Ising spin: state is ±1 stored as T (default Int8).

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LatticeCore.PottsSite — Type

PottsSite{Q, T <: Integer}()

Q-state Potts spin: state is an integer in 1..Q stored as T.

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LatticeCore.XYSite — Type

XYSite{T <: AbstractFloat}()

Planar rotor: state is an angle θ ∈ [0, 2π) stored as T (default Float64).

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LatticeCore.HeisenbergSite — Type

HeisenbergSite{T <: AbstractFloat}()

Classical Heisenberg spin: state is a unit vector in ℝ³ stored as SVector{3, T} (default Float64).

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LatticeCore.EmptySite — Type

EmptySite()

Vacancy / empty site: stores nothing. Useful for diluted models and as a placeholder where a site has no degrees of freedom.

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