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StateEnvsTTN: A container to store the TTN and its environments

Similar to the setup for MPS, tt the lowest-level of abstraction, TenNetLib.jl defines StateEnvs to hold a TTN and its environments to be modified in place.

Skip this part if you want to avoid lower-level abstraction.

TenNetLib.StateEnvsTTN — Type
mutable struct StateEnvsTTN{T1, T2 <: Union{EnvCouplingModelTTN,
                                            EnvCouplingModelProjTTN}}
    psi::TTN{T1}
    env::T{T2}
end

Holds the TTN and the environment.

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TenNetLib.StateEnvsTTN — Method
function StateEnvsTTN(psi::TTN, H::CouplingModel)

Constructor of the StateEnvsTTN from a CouplingModel. Each terms in the CouplingModel are contracted in parallel.

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TenNetLib.StateEnvsTTN — Method
function StateEnvsTTN(psi::TTN, H::CouplingModel, Ms::Vector{TTN}; weight::Float64)

Constructor of StateEnvsTTN from a CouplingModel and a vector of TTN used for excited state search. Each terms in the CouplingModel are contracted in parallel.

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TenNetLib.getpsi — Method
function getpsi(sysenv::StateEnvsTTN)

Returns (shallow copy of) the state psi.

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TenNetLib.getenv — Method
function getenv(sysenv::StateEnvsTTN)

Returns (shallow copy of) the environment env.

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ITensors.position! — Method
function position!(sysenv::StateEnvsTTN, node::Int2;
                   maxdim::Int = typemax(Int),
                   mindim::Int = 1,
                   cutoff::Float64 = Float64_threshold(),
                   svd_alg::String = "divide_and_conquer",
                   normalize::Bool = true)

Moves the orthogonality center of the TTN to node and updates the effective Hamiltonian of the same.

Named arguments and their default values:

  • normalize::Bool = true: Whether to normalize afterwards.
  • maxdim::Int = typemax(Int): Maximum bond dimension after SVD truncation.
  • mindim::Int = 1: Minimum bond dimension after SVD truncation.
  • cutoff::Float64 = Float64_threshold(): Cutoff for SVD truncation.
  • svd_alg::String = "divide_and_conquer".
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TenNetLib.product — Method
function product(sysenv::StateEnvsTTN, v::ITensor)

Returns the Matrix-Vector product between the environment and input ITensor v.

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Base.copy — Method
function Base.copy(sysenv::StateEnvsTTN)

Shallow copy of StateEnvsTTN.

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