Nilpotent and Jordan-block exponentials
If Nʳ=0 and A=λI+N, then eᵗᴬ=e^(λt)Σₖ₌₀ʳ⁻¹tᵏNᵏ/k!.
Key knowledge
If Nʳ=0 and A=λI+N, then eᵗᴬ=e^(λt)Σₖ₌₀ʳ⁻¹tᵏNᵏ/k!. For a size-r Jordan block J=λI+N with ones on the first superdiagonal, Nʳ=0 and its k-th superdiagonal in eᵗᴶ is e^(λt)tᵏ/k!. Similarity transports this formula: e^(tPJP⁻¹)=PeᵗᴶP⁻¹.
Values and equations
e^(t(λI+N))=e^(λt)Σ_(k=0)^(r−1)(tᵏ/k!)Nᵏ, Nʳ=0
- λ
- Scalar real or complex parameter
- N
- Finite nilpotent matrix
- r
- Positive nilpotence bound
- t
- Real evolution parameter
Conditions and scope
- Finite real or complex matrices, r≥1, constant λ,N and invertible P; t is a real parameter.
- The scalar matrix commutes with N, so the exponential product rule is justified. The formula works without an eigenbasis but assumes a known nilpotent decomposition or block; it does not provide every matrix's canonical-form construction.
Sources · 1
References
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Evidence and review
Section 3.8.2 nilpotent definition/truncated Taylor series and scalar-plus-nilpotent example; Theorem 3.8.2 commuting exponential product; section 3.8.3 similarity identity and series proof. The Jordan specialization follows by checking the shift matrix's powers, rather than attributing a full Jordan-form classification to this source.
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Entry details
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- math-nilpotent-jordan-exponential
- Revision
- university-core.1
- Structured reference record
- University core expansion